Quality enhancement with hybrid production

Transcription

1 Combining hybrid inks, overprint varnishes and UV coatings in sheetfed offset Quality enhancement with hybrid production The term hybrid derives from the Latin hibrida, meaning the offspring of a mixed union. Although the union referred to was originally restricted to humans or animals, the term hybrid is now most commonly used in horticulture to describe plants of mixed parentage (hybridisation) and in the automotive industry to describe vehicles propelled by a combination of internal combustion and electric power (hybrid motor). In sheetfed offset today, hybrid presses are generally taken to be presses with the ability to apply hybrid inks and a final UV coating as well as conventional offset inks and an aqueous coating with easy conversion between the two different modes of operation and no need to exchange the rubber rollers, blankets and dryer modules. Hybrid inks incorporate two different chemical drying properties: they dry by oxidation and penetration like conventional oil-based inks, and harden under UV radiation like UV-curing inks. To accommodate the different modes of operation hybrid presses are configured with IR, thermal air and UV dryer modules. Hybrid coating is a cost-effective yet versatile inline process for quality enhancement. It is also a less challenging introduction to UV print production. The gloss levels that can be achieved by applying UV coatings to PRODUCTS PRACTICES PERSPECTIVES hybrid inks are equal to those delivered by pure UV printing systems. A full-solid UV coating in conjunction with a matt or granular overprint varnish applied in the offset register is an economical way of creating some attractive and unusual gloss contrasts. Print designers benefit from the freedom that this conveys, while users benefit from the ability to exploit new lines of business. Hybrid technology is available for virtually every market addressed by sheetfed offset and offers enormous potential for winning new accounts. In other words, hybrid presses deliver diverse and stunning effects inline without the drawbacks of twocoater or pure UV presses. The potential they offer printers in the form of cost savings, quality enhancement and range of applications is examined objectively in this issue of Process. There are also chapters on the latest advances in hybrid technology and the importance of choosing the right (ie tested and mutually compatible) consumables to ensure a trouble-free performance. KBA has been a driving force in the evolution of hybrid technology, and this publication is the product of the expertise and experience that we and our development partners, and our customers as users, have gained over the years. Contents Issue 1/ KBA Editorial 2 Inks and coatings Drying 3 KBA dryers 6 Choosing the right system 10 Adhesion 11 Test methods 14 UV technology Lamps 15 Compatible consumables 18 Blankets and washes 22 Paper specifications 24 Hybrid ink specifications 26 Coating specifications 28 Gloss coating Gloss 30 Offline coating 31 Inline coating 32 Hybrid technology Retrospect 36 Fogra test 39 Cost-efficiency 44 Waterless hybrid inks 47 Environment Emission testing 49 Alcohol-free dampening 51 Handling Benefits and tips 53 Applications Pressroom examples 58 Contacts 63 Resources/partners 29 Product No.:. Accredited For Hybrid Printing

2 Editorial Hybrid has come of age Demand in the industry for issue no. 2 of KBA Process, spotlighting waterless, keyless offset, had copies flying off the shelves at such a rate that our stocks are all but exhausted. We are now following it up by focusing on another aspect of print production in which KBA has been an initiator and driver: hybrid technology, a fresh take on product enhancement in sheetfed offset that is catching on fast among members of the trade. As the name indicates, hybrid technology represents a melding of different production processes, in this case along with new consumables (hybrid-compatible inks and coatings), advanced press engineering and highly specialised know-how. KBA initiated the first applications of this technology in Europe some six years ago. Since then we have worked closely with major players in the ink and coating industry to develop hybrid technology to its present level of maturity, expounding the economic and technical benefits it can deliver and tirelessly promoting its adoption amid ceaseless sniping from various corners at trade fairs, dedicated events and in the trade press. Its success in the market has vindicated us on every count. Since the official launch at Drupa 2000 we have sold a grand total of 250 half-size to VLF Rapida presses with a hybrid capability. Most of them are configured with five or more inking units, a coater for UV and aqueous coatings and a delivery extension for IR, thermal air and UV dryers. Many have been in operation for a some years now and have compellingly demonstrated their superior performance. The sheer diversity of applications they support, some of which are detailed in this issue, have enabled hybrid users to raise their profile in the marketplace with some stunning print samples to win new accounts and offer ad agencies more space for creativity without breaking the bank. And it is by no means only Rapida presses that are used for hybrid applications. Other brands have jumped on the bandwagon as it gathered momentum, and now trumpet its virtues as if they had never been in any doubt. Pioneers with the courage of their convictions do not struggle alone for long if their ideas prove successful. And this is all to the good, because without competition there would be no rapid advances in sheetfed offset and inline finishing such as we have experienced over the past 30 years. The graphic arts industry needs a constant stream of new ideas, not merely a stubborn defence of a status quo that has reliably delivered results, but only with familiar technologies. The industry needs visionaries with staying power on both the demand and the supply side, visionaries who are not going to fall at the first hurdle. Because print will only survive in the long term if it offers more than just ink on paper, cartonboard or plastic. Print can and must arouse emotions, and sheetfed offset can and must raise its profile above that of copiers. Hybrid technology makes an invaluable contribution, as you can see on the following pages. Perhaps you, too, will soon be joining the swelling ranks of hybrid enthusiasts who gather in their hundreds to compare notes and learn the latest at the user meetings we organise each year. Yours, Albrecht Bolza-Schünemann, president and CEO, Koenig & Bauer AG 2 Process

3 Drying and curing Basic principles Formulating and drying sheetfed offset inks and coatings The inks and coatings used in sheetfed offset, and thus in the hybrid process, differ in the physical and chemical principles by which they dry or harden. So selecting the appropriate inks and coatings for any specific job depends not only on substrate absorbency but also on the required speed and degree of drying, the visual effects to be achieved, the proposed applications and the impact on health and the environment. And, of course, the press must be equipped with suitable dryers. A lot of the components in inks and coatings have a direct or indirect impact on how well they dry. Drying method dictates ink formula Sheetfed offset can accommodate inks and coatings with widely differing levels of viscosity. Even at press speeds of around 18,000 sheets per hour, highviscosity inks and oil-based overprint varnishes (OPVs) can be run just as easily as low-viscosity UV coatings and water-based (aqueous) coatings. On hybrid presses, aqueous coatings play a role only during conventional production. For preference, UV and aqueous coatings are applied by an anilox roller and doctor blade standard items of equipment on KBA Rapida dual coater and hybrid presses. Oil-based OPVs are applied the same way as ink via an inking unit with dampened offset plates which ensures precise registration. The inks and coatings are formulated for one or more specific drying methods, and the dryer engineered to assist or initiate the underlying principle. A table of the physical and chemical drying principles involved can be seen overleaf. The primary components in sheetfed offset inks are the binder (binding agent), colorant and additives, all of which interact. So there is always the possibility that one substance will impair the function of another. As a result it is not easy for ink manufacturers to formulate specific properties into the ink or to deliver upon demand enhancements with regard to drying, perfecting, ink fly, stacking or (for food packaging) odour and taste. The largest component by mass in sheetfed offset inks is the binder, which functions as a vehicle for the other components and helps the ink to form a film on the substrate. Commonly referred to as resin, the binder is more accurately a blend of hardened resins, mineral and/or vegetable oils and a siccative (drying agent). In other words it is just a varnish used in ink formulation an indication of its chemical proximity to colourless OPV. Now that other types of coating are widely available, the propensity of oil-based varnishes to yellow plays a minor role, and hybrid production has given this varnish a new lease of life as a means of creating gloss contrasts. When a full-solid UV gloss coating is applied to the sheet it cannot adhere to any areas already covered in an oil-based OPV. Oils dissolve resins, disperse pigments The purpose of adding mineral and/or vegetable oils is primarily The main component of offset ink is varnish, which functions as a binder to dissolve hard or tacky resins so that the ink flows more easily. Another is to disperse the colorant evenly and encapsulate the pigments. Vegetable oils have a direct impact on ink oxidation. If they completely replace the mineral oils the ink can be termed environmentally friendly. Resins form films A common property of all natural and synthetic resins is that during the drying process they form a skin. They must therefore be selected according to how the ink is to dry. Inks that dry purely by oxidation and those that dry by a combination of oxidation and penetration have a high percentage of alkyd resins and colophonies (or rosins), but need oil as a solvent to help them flow. Radiation-cured inks and coatings require no oils or other volatile substances. Radically cured UV inks and coatings, and the less common electron-beam (EB) cured inks, are mainly based on acrylic (AC) resins. Cationically cured UV inks have a large proportion of epoxy (EP) acrylates and specialised resins. In the binder used for radiationhardened inks and coatings, simple and complex resin molecules called monomers and oligomers for convenience assume the function of both resin and oil. In UV and EB systems, viscosity is influenced by the monomers, which function as a thinner in place of oil because they are free and non-cross-linked. Since they optimise fluidity they constitute a major component of UV coatings. Oligomers, which are compounds cross-linked into small chains (prepolymers), influence the gloss, hardness, abrasion and chemical resistance of the polymers subsequently formed. The monomers and oligomers remain separated in the coating until the groups of highly reactive free molecules within them are seized on by radicals or Process

4 Drying and curing Basic principles Monomers and oligomers The terms monomers and oligomers are commonly used in technical literature because of their brevity. However, it would be more correct to use the terms given in UV protocol version 9/2001 issued jointly by four national safety councils CNAMTS in France,BG Druck & Papierverarbeitung in Germany, ISPESL in Italy and HSE in the UK on improved conditions of use of UV technology in the printing industries of the signatory countries. This defines the monomers in UV inks as stenomeric acrylates with a low molecular weight and the oligomers as eurymeric acrylates with a high molecular weight. Both are components of hybrid inks. During the oxidative polymerisation of resin molecule, the ambient oxygen reacts with the oxidising medium, splitting into reaction-friendly oxide ions that cross-link the resin via what are known as oxygen bridges. Catalysts enhance oxygen absorption in the binder, IR radiation accelerates oxidation cations the links to three-dimensional cross-linking (polymerisation). Hybrid inks contain resins that are suitable both for inks that dry by oxidation/penetration and by radical UV curing, so they arguably combine the best of both worlds. The oils, for example, prevent the ink fly that is one of the drawbacks of UV inks. Also, hybrid inks can be overprinted directly with both UV coatings and special OPVs. And whereas pure UV inks and washes require special equipment because they are so aggressive, hybrid inks are relatively mild, so the chemical and physical resistance of the standard rubber rollers and universal blankets specified for conventional inks is perfectly adequate. UV inks, UV coatings and hybrid inks all require ozone extraction at the end-of-press dryer, while EB inks need protection from x-rays. During the curing process, UV radiation causes the photoinitiator (PI) molecules to decompose into radical (PI-) or complex (PI+) cations. The products arising from this decomposition cross-link the monomers (MM) and oligomers (OM) to create a polymer Siccatives promote polymerisation The term siccative is used to denote the substance responsible for the chemical drying process, which can be gradual, by oxidation, or immediate, by some form of radiation. In both cases the process initiated is polymerisation. In inks that dry either partially or solely by oxidation, the siccative acts as the oxidant and the proportion of siccative can be increased by the press operator. Because the oxygen in air is involved in oxidation, the layer of ink starts drying gradually from the surface inwards, so the formation of a skin is not an accurate indication of the actual degree of hardening. In practice it has been found that the application of heat actively accelerates the relatively slow process of polymerisation. An inline aqueous coating capability is thus not the only reason why a lot of colour presses are equipped with infrared and thermal dryers. The inks in hybrid presses dry and harden in several stages. Interdeck UV dryers are normally inserted between the printing units to superficially dry the lower layers of ink without impairing penetration by the oilbased components. Immediately prior to delivery, heat is applied to accelerate oxidation, followed by UV radiation. This allows the UV coating sufficient dwell time to form a smooth, high-gloss finish. The plug-in dryer modules can be inserted at any port in a double delivery extension or the delivery. To support hybrid production KBA has developed a Methods of drying or curing inks and coatings, and possible applications Drying principle External initiator or accelerator Applications Physical process: Absorption of binder IR radiation, possibly thermal radiation Conventional and hybrid inks (in conjunction with oxidation) for absorbent substrates; conventional and waterless coldset inks dry by penetration only Evaporation of volatile mineral oils in binder Thermal, flotation or IR radiation Heatset inks; waterless offset inks for printing plastic Evaporation of volatile base fluid Thermal radiation (modular, flotation, impact jet dryer); Solvent-based inks (gravure, screen, pad, flexo), coatings (offline) and toners (ink-jet); liquid toner (HP thermal fixation indigo/toyo ElectroInk) Evaporation of high-boiling base fluid Thermal or possibly IR radiation Water-based (aqueous) coatings, inks (flexo, gravure) and toners (thermal ink-jet) Precipitation of binding agent and absorption of solvent Moisture in substrate, steam application Moisture- or steam-set corrugated print production with moisture Resolidification of melted or evaporated wax Room temperature; thermal fixation Phase-change ink sticks for ink-jet; ink-bearing films for thermal sublimation; dry and liquid toner Chemical process: Oxidative polymerisation of binder Ambient oxygen, powder application (for better pile ventilation), acceleration by IR and thermal radiation, possible addition of siccative (in ink feed) Conventional, hybrid,waterless offset and screen-printing inks for absorbent substrates, oil-based overprint varnish (in conjunction with penetration) for absorbent substrates and ink layers; purely oxidising offset inks for film Polymerisation of acrylic binder through decomposition of photoinitiators into radicals Polymerisation of epoxy binder through cations released by photoinitiators Polymerisation of acrylic binder through splitting of radicals Polymerisation, polyaddition or polycondensation of two binder components Continuous UV radiation, excimers (flexo only), possibly in inert nitrogen atmosphere Pulsed UV radiation or IR radiation Electron beams rendered inert in nitrogen atmosphere Possible addition of solvent, depending on reaction mechanism Radical UV-cured inks and coatings for sheetfed, heatset and narrow-web offset, screen, flexo and gravure, offline coating; hybrid inks for sheetfed offset; waterless UV offset inks for plastic film, cards, CDs and narrow-web presses (labels, packaging) Cationic UV-cured inks and coatings for sheetfed offset, narrow-web flexo/offset; dual-cure inks for sheetfed offset EB-cured inks and coatings for sheetfed offset, narrow-web offset and flexo Two-component and plastic inks for screen printing 4 Process

5 Drying and curing Basic principles twin-tube carbon IR dryer which can also be fitted in conventional presses (see next chapter). Radiation hardening with and without photoinitiators UV inks and coatings and, to a lesser degree, hybrid inks, contain as a siccative photoinitiators that decompose into highly reactive molecules when exposed to UV radiation. The organic photoinitiators for the various types of resin release either negatively charged radicals or positively charged polyatomic ions (complex cations). These react with the groups of free molecules in the resin, triggering the polymerisation process. Since the photoinitiators are added prior to shipping, the inks and coatings must be stored well away from the light. Photoinitiators are relatively aggressive components, but since hybrid inks and washes contain far fewer than UV inks, the printing units do not have to be specially protected. Odour remains a problem, though this is less noticeable in hybrid inks than in radical UV inks and coatings, and is imperceptible in cationic UV inks. At present, all the hybrid inks and UV coatings used in sheetfed offset contain radical substances only. Above a certain power level an end-of-press UV dryer can cure the inks and coatings in a matter of seconds. Radical UV coatings can also be applied more thickly than cationic ones, and this is a key factor in creating gloss. Although a cationic formulation would have the advantage of continuing to harden once radiation has ceased, thus ensuring that the ink or coating dries right through, with thick layers this can take several hours. Also, at high press speeds more than one end-ofpress UV dryer would be required because of the longer radiation exposure needed, and this would cut the dwell time in which the coating can spread. There has been a lot of research into what have been dubbed dual-cure inks, which basically dry by oxidation and penetration, and thus in theory could be used for conventional applications (ie without the inline coating necessary for hybrid inks), but are briefly exposed to UV radiation to pre-harden the surface so that prints can be finished without delay. If these research efforts prove successful, dual-cure inks could be run on hybrid presses as a third mode of operation and on conventional presses as an alternative to protective coatings to allow faster finishing. EB inks do not require a siccative and electron beam radiation is powerful enough to trigger polymerisation without radicals. Because EB radiation also kills germs, this process is primarily used for printing sterile packaging. The high initial investment costs are outweighed by the efficiencies accruing from the fact that the layers of ink on both sides of the sheet harden instantaneously when only one side is irradiated. Colorant influences more than visual appearance The colorants used in sheetfed offset inks are all pigments. Pigments are defined as organic or inorganic crystals and their agglomerations. In their undissolved form they are suspended evenly in the binder. The bigger the pigment particles and the higher their concentration in the binder, the faster the ink dries or hardens. Effect pigments (metallic, iridescent) can also be added to inks and aqueous coatings. Hybrid inks are available with pigments whose concentration, agglomeration and chemical parameters are largely the same as those in conventional printing inks, so they are basically closer to conventional inks than to UV inks. This is the reason why dot gain with hybrid inks is the same as with conventional inks. Unlike UV inks the characteristics do not have to be changed, which makes it easier to introduce hybrid technology in the press room and to switch between conventional and hybrid operation. However, pigment colour impacts on the curing process of the UV content in hybrid inks, just as it does in UV inks: the longer the wavelength, ie the greater the distance from the UV range (in other words primarily process yellow and spot reds), the smaller the What you should know about hybrid inks impact of the UV radiation. This is because a high proportion of the ultraviolet spectral components in yellow and red pigment particles is absorbed, so they remit fewer UV rays and literally overshadow adjacent particles. With hybrid inks, this can be counteracted by accelerating oxidation prior to the final UV curing, but that is not an option with UV inks. Drying: by oxidation, penetration and radical UV radiation, either simultaneously or consecutively; oxidation compensates for imperfect UV curing (eg of red and yellow pigments) Dryer technology: multistage one to two interdeck UV dryers to trigger curing, IR and thermal dryers in the delivery extension to accelerate oxidation in hybrid inks and/or oil-based varnishes, end-of-press UV dryer in the delivery for hybrid inks and UV coating Formulation: wet and waterless offset inks available Pigmentation: as for conventional inks; process and special inks available Dot gain: as with conventional inks (an advantage when changing the operating mode); unlike UV inks they require no special characteristic curves Printability: easy to handle, no ink fly Material compatibility: no problem if KBA/Fogra-accredited hybrid inks and hybrid-specific oil-based OPVs, UV coatings and washes are used, plus standard rubber rollers and blankets for conversion between conventional and hybrid production Coatability: direct (ie no need for primer) with UV coating; in combination with oil-based OPV and UV coating to create gloss contrasts Value for money: dearer than standard and UV inks, but cheaper to apply and more versatile Car brochure printed using hybrid inks plus matt and gloss coatings Process

6 Drying and curing KBA systems Innovative, highperformance dryers UV IR+TA KBA s universal VariDry system unites flexibility and cost-efficiency. Customised drying systems KBA has a reputation for bespoke products, and its sheetfed offset presses are no exception. Each module-based Rapida press is configured to meet the individual customer s specifications. As a result KBA can provide the ideal kit for general-purpose and specialist printing plants alike. But even when catering to highly specialised needs, KBA strives to ensure that the dream machine affords an equally high degree of flexibility. As any printer can confirm, no one print job is like another. And it is often the drying technology that reveals whether the press delivered embodies an ideal combination Continued from page 5 An end-of-press VariDry unit on a Rapida 105 hybrid press, showing the UV curing unit and the heat section comprising CIR emitters and the thermal air wand of processes or whether the operator must compromise on quality and cost-efficiency. Not surprisingly, for its hybrid presses KBA has developed a dedicated drying system that defines the benchmark in hybrid coating. A drying system fulfils its purpose when it enables the press to accommodate the complete spectrum of inking and coating permutations demanded for production. Hybrid inks, for example, can be finished with a UV coating or with an oil-based overprint varnish plus UV coating, while conventional inks receive a water-based coating. The proportion of spot to full-solid coating, and also the maximum ink coverage, can differ enormously according to the combination of coatings used and the type of job in hand. So KBA has made it possible to position the dryers at virtually any point between the printing units, in the delivery extension and in the delivery within a hybrid Rapida (see box, Standard hybrid press ). The IR, UV and thermal air units can be moved freely from one position to another, and additional ones plugged in at pre-installed docking ports. The never-ending search for technological perfection No shrink-wrapped dryer system can possibly deliver the ideal technology for every application. KBA s ongoing aim is therefore to offer cutting-edge technology that is both reliable and flexible, and to this end has collaborated closely with dryer manufacturers AdPhos- Eltosch, Grafix and IST Metz. Turn to page 7 Additives for fine-tuning Since oils, resins, siccatives and pigments can be combined in so many different ways, it follows that they can only serve as roughand-ready tools for determining printability, adhesion, drying and optical properties. In order to fine-tune inks and coatings to suit specific printing conditions, drying scenarios and substrates, it is necessary to use additives. These are chemicals that are blended in to prevent the ink, say, from forming a skin in the ducts ( duct-fresh ) or from drying on the rollers in the inking unit ( roller-fresh ). But they can also take the form of catalysts and additional siccatives for accelerating individual drying processes. Dispergents help the oils encapsulate the pigment particles and thus prevent lumps from forming, while thinners determine viscosity. The red and yellow pigments in UV and hybrid inks do not cure as well as the blue, green and black pigments. Hybrid inks compensate for this deficit by oxidising (Photos and illustrations: Kleeberg) Other specific substances, which include silicone oils and their substitutes for waterless offset, influence the ph value, emulsification and surface tension and therefore optimise the interaction with the fount solution, plate surface and paper coating. Levelling agents make the ink or coating spread faster upon application to create a richer gloss, while waxes improve slippage and gloss. Many of these additives with the exception of waxes, which are incompatible with UV coatings have naturally been included in hybrid inks as well. Complex demands It can be seen from the above that the practical demands made on ink formulation and drying technologies are enormously complex, so it follows that optimising the properties of inks in general, and of hybrid inks in particular, for specific applications is equally complex. A hybrid label affixed to a can of ink or wash is thus no guarantee for trouble-free printing and finishing. On the contrary, it makes it all the more vital to use only inks, coatings and binders that have been tested for compatibility and accredited by KBA and Fogra or approved by KBA. Hybrid coating is carefree only in conjunction with competent advice. Dieter Kleeberg 6 Process

7 Drying and curing KBA systems Standard KBA hybrid press and optional extras 6 P Five inking units for conventional and hybrid inks: a standard rubber coating on the rollers may only be used in conjunction with KBA-approved consumables and aids. The four process colours can be followed in the fifth printing unit by an additional colour or oil-based overprint varnish to produce gloss effects. Many users add an optional sixth printing unit for greater flexibility. 2 Interdeck UV dryer: there must be a UV lamp between the final printing unit and the coater.if the press is configured with more than five printing units and if print jobs entail a high level of ink coverage, a lot of spread, a high production speed and opaque white primer or metallic inks, it is advisable to add a second interdeck dryer that can be plugged in at any point. An interdeck dryer should have a power density of 160 to 200W/cm, if possible infinitely adjustable. 3 Coater with two separate circulating systems: this allows the press to be converted rapidly between two different types of coating. An optional automatic ink pumping system for aqueous and UV coatings is even quicker and more convenient. An integrated cleaning system with adjustable cycle timing cleans all the coating components automatically in a matter of minutes and almost completely eliminates the need for manual cleaning. With this in place, conversion between UV and aqueous coating takes just 10 minutes, and between identical types of coating (UV to UV, water to water) a mere one to two minutes. 4 Delivery extension: the extended dwell section for the coating contains a combined infrared/thermal air dryer which is used when printing standard inks and aqueous coatings. 5 End-of-press UV dryer: this features three lamps with power levels ranging from 160 to 200W/cm and, like the interdeck dryers, should preferably be infinitely adjustable to suit the substrate. The addition of a powder bar (P) at the maximum possible distance from the end-of-press UV unit, towards the sheet brake, is recommended to prevent a glass-plate effect. 4 and 5 VariDry dryer: initially available only for the Rapida ACS: optional air-cleaning system, strongly recommended. It supports the obligatory ozone extractor at the UV lamp by extracting the residual ozone and loose powder particles above the delivery pile. The interfaces and docking ports have been rejigged and sheet travel adapted to dryer dimensions and performance levels. In 2003 KBA seized an opportunity to integrate drying technology earlier into its design and manufacturing cycle so as to offer a complete press/dryer package. During the Graph Expo trade fair in Chicago, US manufacturer Air Motion Systems (AMS) of Golden, Colorado, signed a licensing agreement granting KBA worldwide rights for the production, further development, distribution and servicing of AMS drying and curing systems for installation in Rapida sheetfed offset presses from the 105 to 205. The modular UV, IR and thermal air systems are marketed collectively under the name VariDry. KBA will, however, continue to offer the option of dryer systems from other manufacturers. VariDry for hybrid presses too The ability to manufacture and develop the VariDry system, right down to the individual dryer modules, at its Radebeul plant enables KBA to meld its expertise in sheetfed offset press engineering and more specifically in sheet guidance in the dryer section and the selection of materi The VariDry unit can accommodate seven Carbon Twin emitters als and coatings more closely with dryer technology. This has greatly increased the flexibility and range of applications possible with VariDry: the modules are freely interchangeable, they can be placed in any position or sequenced by drying principle (UV, IR, thermal air), configured in any quantity and performance level and can thus be customised for the substrate, image layout, ink type, coating and production speed. VariDry will initially be installed in all Rapida 105 presses, ie all medium-format hybrid presses, and will later be extended to other formats. If there is no end-of-press UV curing, the delivery extension for the new Rapida 105 can accommodate 18 VariDry modules ie seven infrared plus eleven thermal air all freely interchangeable. Another new feature is that the heat registers for the thermal air are located on either side directly in the delivery. Warm-air extraction is infinitely adjustable from the console. With end-of-press UV curing (ie on hybrid presses), the last three docking ports are occupied by UV lamps with an output of 160 to 200W/cm ( W/in) apiece. These lamps are also interchangeable. This is useful when lamps with different power levels are used. Each lamp is simply plugged in and can be changed easily by the operator. Process

8 Drying and curing KBA systems Wavelengths used in IR drying Water-based coatings are dried by exposing them to IR radiation, which they absorb.this causes them to heat up and the water in them to evaporate. But the water will not evaporate completely unless the actinic wavelength* (around 3,000 nanometres or 118µin) of the coating is irradiated with a specific amount of energy. According to Wien's displacement law**, the shorter the wavelength at which a lamp achieves maximum radiance ie the further this wavelength is from the 3,000nm ideal in the electromagnetic spectrum the higher the input of energy required.that is why shortwave IR lamps are less suitable than medium-wave ones. Ultra-shortwave halogen IR (HIR) lamps and water-cooled IR lamps have a maximum radiance in the near-infrared (NIR) range of around 800nm (31.5µin), the transition point between visible red light and invisible heat radiation. They are therefore totally unsuitable because the energy input required would make them uneconomic. Shortwave IR (SIR) lamps have a maximum radiance of around 1,100nm (43.3µin). Because of the distance from 3,000nm, this demands a huge imput of energy, much of which is not used, so the relative energy efficiency (the efficiency with which water is made to evaporate) is correspondingly poor. Also, the unutilised heat radiation has the undesirable effect of heating the substrate. The main diagram shows the spectral radiation distribution or intensity curve, S(λ), of three different types of IR lamp: shortwave (SIR), fast medium-wave (FMIR) and twin-tube carbon (CIR), standardised according to their surface drying power. From the blue inset diagram, which represents the relative spectral absorption rate α (λ) for aqueous coating (maximum at a wavelength of 3,000nm), it can be seen that twin-tube carbon emitters are more effective at evaporating water (indicated in light blue beneath the CIR curve) than other IR lamps.the intensity curve also shows that CIR produces the best absorption rate, and thus the most effective reaction with the smallest input of energy, ie at the lowest temperature: just 1,200 C (2,192 F). (Source: Heraeus Noblelight) The maximum radiance of the various medium-wave IR lamps on the market ranges from approximately 1,500 to 2,400nm ( µin). Lamps operating at 1,500nm switch on and off fast and react instantly to control signals, so maximum radiance can be timed precisely. In practice, these fast medium-wave IR (FMIR) lamps, as they are known, are often paired with shortwave IR (SIR) lamps because their combined intensity curves approach 3,000nm. However, the effect is still not satisfactory.twin-tube carbon IR (CIR) lamps have a maximum intensity of 2,000nm and are thus much closer to the 3,000nm goal than the other types of lamp mentioned, so they do not have to be paired with SIR lamps. What is more, CIR lamps are almost as fast as FMIR lamps. But the high radiation density generated with CIR is unique. It is this property that slow medium-wave IR (SMIR) lamps lack, otherwise their maximum radiation of 2,400nm would make them even more effective. Technology has not advanced far enough to produce longwave IR lamps, whose maximum radiation would lie between 5,000 and 10,000nm. *The actinic wavelength of a substance is the wavelength at which a chemical or physical reaction is triggered within the substance. Aqueous coatings and other substances containing or comprising polymers react to IR radiation most effectively at 3,000nm (118µin). ** Wien's displacement law states that, for a black body (in this case a lamp), the product of its thermodynamic temperature and the wavelength corresponding to its maximum radiated energy is a constant (T λ = constant). Basically, the hotter the lamp, the shorter the wavelength at which it will emit radiation. So if the maximum radiated energy shifts towards a longer wavelength (in this case towards 3,000nm) the curve flattens out because the temperature falls. It follows that if the maximum temperature or radiated energy is reduced, the lamp will require less energy to achieve the same level of drying efficiency. This is the principle exploited by twin-tube carbon emitters. The thermal air wand (left) and Carbon Twin emitter (right) can be positioned at any port, enabling the VariDry system to be customconfigured for production speed and the job in hand Twin-tube carbon IR a new dryer generation KBA s R&D work on the VariDry concept culminated in a new infrared drying system the twintube carbon emitter which dramatically enhances the efficacy of IR dryers. Since IR dryers are one of the biggest consumers of energy on a sheetfed press, this is reflected in energy costs. The new IR emitters can be plugged into the VariDry unit whenever thermal irradiation is required, eg to dry the aqueous coating in conventional and hybrid presses or primer in a dual coater press, to accelerate oxidation when running conventional, waterless or hybrid inks, or to evaporate solvents in other printing processes. 8 Process

9 Drying and curing KBA systems Carbon technology maximum impact, minimum heat KBA plumped for the unconventional Carbon Twin system, as it is called, because it evaporates the water in water-based coatings with maximum efficiency and speed yet a minimum input of energy. Such a high level of efficiency was previously unknown. The Carbon Twin was brought to market in 2003 by Heraeus Noblelight in Hanau, Germany, a specialist manufacturer of light and light-radiation systems for industrial applications and part of Heraeus Holding, a fine metals and technology group. As in most other short- and medium-wave IR lamps, the filaments are housed in two parallel tubes in order to generate the necessary output across the format width. KBA uses twin tubes with a power density of 80W/cm (200W/in), which heats the carbon filaments to 1,200 C (2,192 F). The quartz glass tube is gold-plated on the inside for maximum efficiency in reflecting the IR radiation. A carbon IR (CIR) emitter operates in the medium-wave infrared spectrum and achieves maximum radiance at a wavelength of 2,000 nanometres (79µin). CIR is thus much closer than other IR dryers to the wavelength of 3,000nm (118µin) at which the water in an aqueous coating completely evaporates (see box, Wavelengths used in IR radiation ). Its proximity to this ideal wavelength means that a CIR emitter requires significantly less energy to evaporate water. This lower energy input and smaller proportion of wasted heat translates into a much higher degree of efficiency than with other IR dryers and, which is just as important, only a slight warming of the substrate. The new quickswitch CIR emitter is regulated by measuring the temperature of the delivery pile. This enhances both the process stability and the quality. But that s not all: twin-tube carbon emitters have such a high, stable and homogeneous radiation density that they can even be used for sheet widths of up to three metres (118in). So the Carbon Twin operates well within its limits even in the world s widest sheetfed offset press, the KBA Rapida 205. Dieter Kleeberg The end-of-press UV unit in the VariDry system can accept three interchangeable UV lamps, each with a specific power of 200W/cm (500W/in) The supply lines for communication, power, exhaust and water must be in the parked position when a UV lamp is removed The UV lamps have bayonet connections for quick and easy repositioning Process

10 Inks and coatings Interaction Choosing the right coating system A press is selected according to the product spectrum it must print and the properties, ie adhesion and mutual compatibility, of the press consumables used to print these products. The table below lists the relevant KBA press configurations for the various permutations of inks, coatings and substrates. In packaging, display and label printing, where visual and haptic effects play a key role, inline coating is the norm. In the past, printers had a choice of two competing systems: pure UV or double coating. Now, largely thanks to development work by KBA, there is a third choice: hybrid coating. Pure UV A production line with UV inks plus final UV coating delivers an exceptionally high level of gloss. Here it is advisable to have a double delivery extension so that dwell time is sufficient for the UV coating to cure into a homogeneous, mirror-smooth surface. But once the radical decision has been made to go for a pure UV system it is all but impossible to switch to another type of coating. Double coating Previously the preferred choice for printers wishing to continue using standard inks, but unwilling to dispense with a UV gloss for certain jobs. The two coaters are generally located at the end of the press. To eliminate or reduce the risk of draw-back (penetration of the ink or substrate by the coating) an aqueous coating must be applied between the wet offset ink and the final coating. This primer seals the ink and, when dried by IR or thermal radiation, serves as a base to which the UV coating can adhere. Each of the coaters must have an integrated dryer, which adds to the size and cost of the press line. However, they do support a wider range of gloss effects than pure UV presses. For example, instead of a primer plus UV coating they can be used to apply two identical aqueous coatings (eg to enhance the final gloss by doubling the coating layer on the substrate) or to apply two different coatings (eg a standard coating in the first coater and special effect pigments in the second). Two-coater presses also include presses featuring an additional Permutations of inks, coatings and substrates possible in sheetfed offset flexo printing unit plus dryer prior to the first offset unit, for applying opaque white or effect primer. They can even be used for UV inks. KBA has shipped a number of Rapida presses with this capability, which is also available from Heidelberg (Speedmaster CD 102 Duo) and MAN (Roland 700 Ultima). However, unusual configurations such as these are generally limited to niche applications. The third way: hybrid Hybrid presses, unlike UV presses, unite the best of both worlds. Not only that, they are more versatile than pure UV presses and require less experience with UV production on the part of the operating crew. So hybrid presses are the ideal tool for new players in the UV market. As a rule, the gloss achieved with UV-coated hybrid inks is far superior to that delivered by the application of two coatings on standard inks, and approaches the levels of pure UV systems. Hybrid presses are particularly good at delivering a combination of matt and gloss effects in which the gloss contrast is far sharper than that achieved by applying a hot aqueous coating prior to the UV coating to create a drip-off effect. And hybrid coating offers additional options such as a blend of granular and gloss effects. What is more, in the appropriate configuration, hybrid presses can print with a low alcohol content or even no alcohol at all, and therefore boast environmental credentials that neither UV presses (aggressive cleaning agents, ozone emission, ink mist) nor dual coater presses (higher energy consumption for drying) can hope to match. And if that is not enough, prepress specialists will be glad to learn that, whereas UV inks have a higher dot gain and different ink mixing properties, hybrid inks have the same tonal transfer characteristics as standard inks. The hybrid process combines several drying technologies: hybrid inks dry by oxidation like conventional inks (and partially penetrate the substrate), but respond to UV radiation like UV inks. Production can be switched between hybrid and conventional inks with no change of rubber rollers, blankets or dryer modules. And a hybrid press can process both standard inks and water-based coatings. Dieter Kleeberg Preprint Ink type 1st coating 2nd coating Substrate KBA press Oil-based varnish* Oxidising/penetrating Super-absorbent paper Rapida Oxidising/penetrating Oil-based overprint* Paper, carton Rapida, Rapida hybrid Oxidising/penetrating** Aqueous Paper, carton, (corrugated) Oxidising/penetrating Oil-based overprint* (spot) Drip-off or dual-effect aqueous (full-solid) Paper, carton, corrugated Rapida+D+DE(2), Rapida hybrid, Rapida 74 G+C+DE(2) and 74 Karat+C+D Rapida+C+DE(2) Oxidising** Special aqueous Selected synthetics, metallised Rapida+C+DE(2), Rapida 74 G+C+DE(2) and 74 Karat+C+D with plastic printing option Oxidising/penetrating Aqueous (primer) Metallic aqueous Paper, carton, corrugated Rapida+C+D+D+C+DE2 (double coating) (Aqueous effect, opaque white)*** Oxidising/penetrating Aqueous (primer) UV Paper, carton, corrugated Rapida C+ID(+ID)+P+C+D+D+C+DE2 (double coating) (Aqueous effect, opaque white)*** Oxidising/penetrating Aqueous Aqueous coating, aqueous effect Paper, carton, corrugated Rapida C+ID(+ID)+P+C+D+D+C+DE2 (double coating) (Aqueous effect) UV Metallic effect UV or aqueous effect Paper, carton Rapida C+ID(+ID)+P+UVID+P+ +UVID+C+D+D+C+DE2 (UV+double coating) UV** UV Paper, carton, corrugated, selected synthetics, metallised, metal Rapida+P+UVID+P+UVID+P+UVID+C+DE2 (pure UV) Hybrid** (ox./ pen. + UV) Special UV Paper, carton, corrugated Rapida hybrid Hybrid** (ox./ pen. + UV) Special oil-based overprint* (spot) Special UV (full-solid) Paper, carton, corrugated Rapida hybrid *Oil-based varnish is normally applied by an offset printing unit, all other coatings by a coater **Also wet offset ***Inline preprint coating only possible with special presses Abbreviations: P = printing unit, C = coater, D = dryer, ID = interdeck dryer, UVID = UV interdeck dryer, DE = delivery extension with end-of-press dryer, DE2 = double delivery extension, hybrid = P(+UVID)+P+UVID+C+DE2 10 Process

11 Inks and coatings Interaction Adhesion and compatibility of inks and coatings No ink is suitable for all types of substrate. Also, inks and coatings that dry by different principles cannot be combined in the same printing and finishing process unless they are mutually compatible and compatible with the substrate. On top of this the drying system must be configured to optimise the print quality delivered while consuming no more energy than absolutely necessary. Ink must adhere to the substrate It is an irrefutable fact that the degree of ink adhesion to the substrate is a basic determinant of print quality. In practice, overprint varnishing is sometimes used in the belief that it improves ink adhesion. This is wrong: the coating merely adheres to the layers of ink, and if these are not firmly attached then both the coating and the ink will come away. So inks must be selected first and foremost according to their compatibility with the physical and chemical properties of the substrate, ie its absorbency, wettability (roughness, surface tension) and resistance to IR and UV radiation. Taint, odour etc are secondary considerations. The coating, laminate or film is then selected to suit both the substrate and the ink. And it must adhere to the ink regardless of whether it is applied when the ink is still wet or has already dried. If the prints are to undergo further finishing, eg stamping or scoring, then it is vital to check whether the layer of coating will allow this, and whether the hot-stamping foil can be printed if necessary. One method frequently adopted to enhance ink adhesion on label paper or on carton is to apply opaque white or an aqueous coating prior to printing. Both types of coating are chiefly used to create specific visual effects, but once they have dried they furnish an ideal primer for the inks that follow. Oil-based overprint varnish and UV coating in hybrid production Oil-based overprint varnishes (OPVs) are available in various gloss, matt and structured formulations and are relatively uncomplicated, being compatible with standard inks, non-alkali-resistant inks and hybrid inks alike. But it is best to follow the manufacturer s recommendations as to the compatibility of a varnish with a specific series of ink. Oil-based OPVs fell out of favour because of their inherent colour and propensity to yellow with age, their lengthy drying time, the need for powdering and the thinness of the layer compared to coatings applied with a dedicated coater. Hybrid inks have given OPVs a new lease of life, though applications are limited to the creation of contrasting gloss effects. Highgloss spots are created by applying OPV to the non-spot areas, followed by a full-solid inline UV coating. The UV coating penetrates the wet OPV and causes draw-back, so a high gloss is created only on the unvarnished spots. This interaction of two different coating systems is the opposite of the standard method of spot coating, but means that spot coating is possible in an offset register. Specific effects can be achieved by applying a varnish and coating with different surface tensions. The higher the surface tension of the OPV, the more granular the effect (reticulated grain structures), while reducing the tension makes the coating more matt. Though very good, the results do not approach the standard of a UV matt coating. What is draw-back? OPV and aqueous coating Interfacial tension plays a similar role when oil-based OPV is used with an aqueous coating to cause drip-off a phenomenon created by applying a matt OPV, which adheres well on standard inks, followed by a high-gloss thermal aqueous coating. Heating the coating with a separate heating unit reduces its viscosity and makes it a lot easier to process. The high-gloss coating drips off the areas with a matt coating and the matting is retained, hence the term drip-off. Weilburger Graphics has dubbed this the twin effect and with its Senolith Twin-Effect coatings there is no need to heat the aqueous coating. However, since an aqueous coating cannot deliver as high a gloss level as a UV coating, drip-off cannot compare with a hybrid coating. And hybrid is most certainly the better choice for anyone printing gloss contrasts on a regular basis. Aqueous coating alone and with UV coating Aqueous coatings are the most popular choice for inline applications. Up to 90% of the water content in protective waterbased coatings evaporates in a fraction of a second when exposed to IR or thermal air radiation, though aqueous coatings for creating matt or gloss effects, or coatings embodying effect pigments, do not dry quite as fast. Once the water has evaporated, the finely distributed acrylates harden instantly into a solid film, which is why aqueous coatings are used increasingly as a means of enabling prints to be finished much sooner. There is no yellowing, no need for powder, and aqueous coatings are compatible with all but a very few ink types (eg alkali-resistant ones). In conjunction with UV inks they can even be used as overprint and special-effect coatings. Moreover, a specific type of aqueous coating, called a blister coating, can be used to glue moulded film onto the substrate (mostly carton or solid board). Draw-back is a sudden loss of gloss caused by the coating penetrating the ink and/or substrate to which it is applied, and is the main reason why dual coater presses were developed. Draw-back occurs, for example, if a UV coating is applied to conventional offset inks while they are still wet: the airtight layer of coating prevents the ink from drying by oxidation. Although some ink components penetrate the substrate as normal, the others bond with the coating, causing a change in light reflection which is perceived as a loss of gloss. The higher the ink coverage, the duller the effect. If an aqueous primer is applied and actively dried in an IR or thermal dryer prior to the UV coating, it prevents all contact between the ink and the UV coating and also enhances the degree of gloss. However, draw-back can still occur if the UV coating is applied before the primer is dry.with hybrid inks, which respond to UV radiation, draw-back is virtually non-existent. Process

12 Inks and coatings Interaction Overcoming interfacial tension to improve wetting and spreading Interfacial, or surface, tension is created by intermolecular forces (Graphic: Schmid Rhyner) Intermolecular attraction is what causes a medium (in this case the substrate, plate surface, ink, coating, fount solution, air) to cohere, ie form a solid or droplet. Intermolecular forces near the surface give the appearance of a surface film, and this is known as surface tension when the adjacent medium is air. Contact with another medium (eg ink on a plate,coating on ink) causes an interaction between the two surfaces, and this is called the interfacial tension. The SI unit of measurement is 1 millinewton per metre (1mN/m), which replaced 1dyn/cm. Because of its molecular dipolarity water has a very high surface or interfacial tension, revealed in its tendency to bead (form droplets) and run off smooth surfaces. Isopropyl alcohol or substitutes thereof are added to the fount solution in offset so as to reduce the surface tension of the water base and thus ensure optimum plate wetting by enabling the water to spread over all the print-free areas. Manufacturers of low-viscosity aqueous and UV coatings add wetting and spreading agents to achieve the same effect. These cause the coating to spread quickly and evenly on the ink layers or directly on the substrate.to ensure that the volume of coating applied is always the same, and the film therefore homogeneous, anti-foam agents are added to eliminate air bubbles. If the shearing resistance has been set properly then the coating can even be transferred at high speed without causing any problems. Nonetheless, wetting may be impaired for no apparent reason. Such impairment may take the form of tiny holes called pinholes in the layer of coating. To achieve optimum adhesion of all ink and coating layers the interfacial tension must fall within a specific range:the substrate or primer must have the highest tension (paper coating 35mN/m, synthetics 38mN/m minimum), the ink a medium and the coating the lowest tension. If a liquid (2) is to spread over and wet a solid (1), its surface tension must be lower than that of the solid (bottom schematic). Otherwise it will bead and run off (top schematic) (Graphic: Weilburger Graphics) An aqueous coating is essential in a dual coater press, where it functions as a barrier between the wet oxidising ink and the UV coating to counteract draw-back (see box). At the same time it enhances the gloss of the UV coating. Sometimes a light dusting of powder is needed, but often even this can be dispensed with. At all events, aqueous and UV coatings should only be combined where approved by the coating manufacturer. As an alternative to an end-of-press UV coating it is possible to apply an additional aqueous coating or use film lamination, whose quality is improved by the primary coat. UV coating on UV and hybrid inks UV coatings deliver the highest gloss level and this is even better on UV and hybrid inks than on a prior application of primer. In fact, the coating can be so smooth and hard that it can cause a form of blocking called the glass-plate effect (see box). UV inks and coatings cure instantly, so the prints can be finished without delay, even if as in the case of hybrid inks the underlying layers of ink have only been superficially hardened and not cured right through. Once cured, UV coatings have little or no propensity to migrate (contaminate substances with which they come into contact), block or rub off, and are alkali-, chemicaland heat-resistant. What is more, they are not only compatible with UV and hybrid inks but are also available in formulations suitable for die-cutting and gluing. Another big advantage of UV inks and coatings is that they can be applied to non-absorbent substrates like plastic film and metal. But one of the most popular applications is for printing folding cartons, where the absence of taint and odour are vital. Since UV-cured print consumables contain no solvents they are taintfree, and with the right handling they are almost odour-free. Hybrid inks adhere to paper, carton, solid board and corrugated just as effectively as standard inks, and for substrates such as these they are an ideal substitute for UV inks, which have a number of inherent drawbacks. Also, like UV inks they can be directly overprinted with a UV coating, whereas standard inks require a prior application of primer. And because hybrid inks, like UV inks, have already been pre-cured in an intermediate UV dryer, the UV coating has no trouble adhering to the film that has been created. Choosing suitable hybrid inks When choosing hybrid inks it is best to follow the recommendations of the press manufacturer and Fogra. This will not only ensure that the inks print cleanly, are easy to wash off and, of course, have been tested for compatibility with rollers and printing blankets, but will also ensure that they are coatingproof (ie solvent- and alkali-proof as per DIN 16524), contain no drying retardants and are not highly scratch-resistant. It thus eliminates the need for additives and the inherent risks these entail. An immaculate print also depends on metering fount solution additives correctly. Powder spraying is not normally necessary, but if a powder does have to be applied it is best to choose a very fine one so as not to impair the coating. The range of workable substrates is limited to coated paper, carton and board with low levels of absorbency. Stock weights of 120gsm (80lb book) or more should be creased prior 12 Process

13 Inks and coatings Interaction to folding, so it must be ensured that the fibres run parallel to the crease. The substrate should be allowed to acclimatise in the press room for a minimum of twelve hours prior to impression. Choosing suitable UV coatings Curing speed and adhesion both of the coating on the ink and of glue or hot-stamping foil on the coating depend on the coating formula. The reactivity of UV coatings varies according to whether or not they can be used for hot-stamping or gluing. What is more, the UV coatings suitable for hybrid inks differ from those suitable for dual coating or pure UV applications. The adhesion of a UV coating to the ink also depends on whether or not the ink contains a slip additive (eg silicone or wax), since this may reduce the interfacial tension of the ink so much that the coating can no longer spread properly. In this respect waterless hybrid inks pose a particular challenge for coating manufacturers, though at the second hybrid user meeting, in April 2005, KBA demonstrated that even here viable solutions have been found. The UV coating, too, should contain as little silicone as possible. Silicone makes conventional UV coatings more glue-resistant, as the tape test shows, but gloss contrast suffers as a result since wetting is also impaired. UV coatings specifically formulated for use with glues are silicone-free and should be used in preference to coatings mixed by the press operator. Having said that, cutting out the glue areas in the coating forme is always safer than gluing coated areas. It is advisable to add a little silicone when UV coating both sides of the sheet to prevent blocking when the sheets are trimmed. As a rule this type of blocking can be avoided by adding a light dusting of powder or a suitable partial coating. Trimming the pile before it cools (and the air between the sheets is driven out) also helps. If an unsuitable UV coating is used it can cause the ink layers to loosen, which is fatal. To prevent such unpleasant surprises it is vital to follow the manufacturer s recommendations when using new combinations of ink and coating. Most coating manufacturers are also willing to check the compatibility of a coating with a specific ink by carrying out a series of tests, and to modify the coating if necessary. Based on feedback from Rapida users and its own experience in the Radebeul demonstration centre, KBA recommends a viscosity (DIN cup run-out speed) of 70s for UV coatings. The coating should have a spreading speed of approximately 50s following application. The viscosity can be reduced by using the temperature control system to warm the coating. Dieter Kleeberg Anilox coaters, anilox rollers and coating formes What is the glass-plate effect? This is a form of blocking in which all the air between smooth paper sheets in the delivery pile is forced out, creating a vacuum like that between two plates of glass. UV coated paper, particularly if it is perfect coated, is particularly prone to this type of blocking, making it all but impossible to separate the sheets. Preventive action can take the form of a light dusting of powder, a prior application of an oil-based varnish (red stripes) or trimming the pile while it is still warm and full of air. Anilox coater: Two-roller coaters are a thing of the past: thicker layers of coating can be applied with an anilox doctoring system.this flexo-based technology is also more suitable for the low viscosities of aqueous and UV coatings and allows coatings with larger effect pigment particles to be applied. Anilox roller: The thickness of the coating layer applied to the substrate depends on the volume of coating picked up by the anilox roller,and this can only be metered precisely if the press operator ensures that no dried residue is allowed to remain on the roller surface. The choice of screen for the surface depends on the coating that is to be applied. Praxair Surface Technologies, which supplies rollers for KBA coaters, advocates conventional hexagonal screens only for coatings with metallic pigments. For all other aqueous and UV coatings it uses open structures for a foam-free transfer. Spirally engraved rollers are no longer the state of the art: Praxair has developed what it calls anilox reverse technology (ART) a negative screen, as it were, which instead of cells has islands forming a network of channels which accept the coating (see graphic). For highgloss coatings, ART is often combined with a thin ink film (TIF) and the coating distorted in one direction.the table below indicates when an anilox roller should be used in a hybrid press coater for aqueous coating (conventional mode) and UV coating (hybrid mode). KBA Radebeul, whose keyless inking credentials have been honed by years of experience, has also started manufacturing anilox rollers for its keyless inking units and coaters. Coating forme: For high-end coating jobs it is customary to use a polymer flexo plate, which is normally manufactured externally. But for most other jobs a coating forme is perfectly adequate, and also much cheaper. This can be a coating blanket or a polymer plate imaged offline either manually or with a CAD plotter. Coating blankets are usually used for full-solid coating and can remain in the press for several jobs. But they can also be used for straightforward spot coating by cutting the nonimage areas out of the surface layer.this, too, can be done either manually in the press or on a plotter. Coating blankets have a similar composition to printing blankets, but the surface does not allow any build-up. Allowance must be made for the difference in height when switching between coating blankets and plates. Structure Frequency Angling Pick-up Anilox roller? ART 120 lpc 45 9 cm 3 /m 2 UV and aqueous coating on paper up to 170 gsm ART 120 lpc cm 3 /m 2 UV and aqueous coating on carton ART/TIF 100 lpc 45 /75 16 to 20 cm 3 /m 2 Aqueous coating for high gloss ART/TIF lpc 45 /75 18 to 22 cm 3 /m 2 UV coating for high gloss Process

14 Inks and coatings Basic principles and interaction Choosing the right testing method Before combining a specific substrate, hybrid ink and UV coating for the first time in a production run it is wise to determine the optimum setting for the end-of-press UV dryer. And immediately prior to impression it is also advisable to check how well the UV coating cures and adheres, especially if it is going to be applied to full solids. In this instance, optimum setting means the setting at which the dryer consumes no more energy than is absolutely necessary not only because excessive energy consumption bumps up costs,but also because too high a level of UV radiation can overheat the coating and substrate, causing them to emit odours and become so brittle that even the paper s inherent coating may crack during folding. Cationically cured UV coatings adhere to any material and cure right through after a single UV impulse, so there is no need to run tests prior to use. But the present generation of UV coatings for hybrid inks all cure by radical chain action, like the inks. So what is the best way to check whether a UV coating on hybrid inks has cured right through? Though there are several methods used in the press room to determine the threshold values and optimum permissible radiation power,none of them has been standardised,so they all depend on the individual printer s experience and subjective perception.and the accuracy of such tests is also impaired by coating specifications, eg their suitability or otherwise for stamping or gluing. Fingernail test A quick and reliable way of checking the coating is to scrape the coating with a fingernail or other suitable object (which should be used again for later tests). This will show how hard the coating surface is and whether the coating film has adhered to the ink layers firmly enough to prevent it from being rubbed off. This test is fine for checking to see whether the sheets are dry enough for finishing. Slippage, another coating property, can be checked quickly and manually by taking two sheets from the pile and sliding them against each other with varying degrees of pressure. At the same time the operator will see whether blocking (due to the glass plate effect) has occurred with high-gloss sheets. Talcum test The talcum test is a more complicated method for checking scratch-resistance. Two sheets are UV-coated and one sheet is laid aside while the other is run through the press and final UV dryer a second time, but with no additional coating. Fine powder (talcum or baby powder) is then applied to the sheets and wiped off again. If powder remains on both sheets, then the level of UV radiation applied was obviously too low. If powder adheres only to the coating film that has been cured once, then the radiation level was almost, but not quite, high enough. The test can be repeated until the correct level is reached. Some printers use just Up to a certain thickness equivalent to the full-solid density DS, a non-linear value a layer of UV ink will cure completely. Above this the level of UV radiation must be increased. Hybrid inks, which also dry by oxidation and penetration, have a higher critical thickness (Source: RadTech) one sheet and cover half of it during the second pass through the dryer. Tape test A lot of hybrid and UV printers use the tape test. Since the width and adhesive strength vary from one type of tape to another, it is almost impossible to repeat the test precisely so as to obtain comparable results. On top of this, the speed with which the tape is ripped off the coated surface even by the same printer can vary a lot. The tape test is used to check whether the UV coating is adhering to the hybrid ink layers and therefore whether it has hardened all the way through. But what it really demonstrates are various forces relative to each other: it only shows whether the UV coating adheres more (or less) strongly to the tape than to the ink. But does the printer really want to know whether the coating sticks better than an adhesive? UV coatings with a silicone content of 1% to 2% will be more resistant to the tape, so the test may be useful for this particular coating mixture. But adding silicone to a UV coating has a number of drawbacks which can be avoided by using special coatings. When the tape is ripped off, what splits may be the paper coating or the ink, not the UV coating. While this would indicate that the coating has cured thoroughly and adheres well, it can also prompt the printer to draw the wrong conclusions with regard to the adhesive power between ink and paper or the cohesive forces within the layers of ink or paper coating. Thus the whole logic of the test is destroyed, since it may give rise to more uncertainty, not less. Acetone test This, too, serves not to test the surface hardening of the UV coating, but the extent to which it has cured in depth and thus its adhesion to the ink. This test entails soaking a cloth in acetone, rubbing it over the coated surfaces of two sheets and then rubbing the two sheets together. If the coatings shift, they have failed the test. This will furnish usable results if normal UV coatings are used, but not stampingor glue-compatible coatings, which will not shift even if they are insufficiently cured. So this method is equally unreliable, particularly since the volume of acetone, the dwell time and the abrasive force are not specified. Chemical test Where a lot of problematical substrates and coatings must be tested, eg in the packaging industry, it often pays to have an in-house laboratory where much more complex and sophisticated tests can be conducted than are possible under pressure of time at the press. Checking on drying progress is just one of many. A coloured chemical solution is applied to the coating in accordance with the manufacturer s instructions and under reproducible conditions. This will cause the coating to discolour, with the degree of discoloration (which can be precisely determined by analysis) indicating the degree of curing. Dieter Kleeberg The tape test is often used to check whether a UV coating has hardened and adhered to the hybrid ink. But is it really only the coating layer that comes away, or has the ink layer or paper coating split as well? (Photo: Vegra) 14 Process

15 UV technology UV lamps UV radiation correct positioning, correct power level Precise control of the UV curing process is essential both in pure UV printing and in hybrid coating. The spectral properties of the lamps, their positioning singly as interdeck dryers or grouped together as final dryers, and the ability to adjust the level of radiation so as to cure inks and coatings fast, yet with no excessive application of heat, all play a vital role. Allowance must also be made for the impact on the substrate and curing process of the IR radiation generated as a by-product. Rapida users can choose between a VariDry system from KBA or dryers from other manufacturers. The relative spectral radiation distribution (emission spectrum) of a mercury vapour lamp, and its wavelength drift from UVC into the range of visible radiation (light). An identifying feature of mercury vapour is that its highest peak is 365nm. Lamps with low peaks in the UVC range emit little ozone into the ambient air. Peaks in the near infrared range (700 to 1,000nm) are not shown Printing with UV inks and coatings demands a lot of experience. There is less skill involved in working with hybrid inks and UV coatings, so they represent both a useful alternative and a good introduction to pure UV production. Nonetheless, there are a few basic ground rules that hybrid users must take on board with respect to UV technology. Not all UV radiation is the same Ultra-violet light is the term used to describe the invisible shortwave range that borders on the visible violet range at around 380 nanometres (15µin) in the electromagnetic wave spectrum. It extends to approximately 100nm and is divided into three types: UVA (long-wave), UVB (mediumwave) and UVC (short-wave). These all serve different functions during the curing process for UV coatings, UV inks and hybrid inks (see table). Which is why the spectral properties (or emission spectrum) of a UV lamp must be appropriate for the intended application. At present the only suitable source of UV radiation are gas discharge lamps, which have quartz glass tubes filled with either mercury or halide vapour (usually an iodine compound). Mercury vapour lamps are the preferred choice for UV curing, while high-pressure metal halide lamps are used in the manufacture of printing formes. The steepness of the peaks in the emission curve depends on the pressure inside the tube. These peaks reflect a higher radiation intensity than in adjacent wavelengths. For a high degree of efficacy in curing hybrid inks or UV coatings, some peaks must fall within the spectral sensitivity range of the photoinitiator (UVC), others in the continued reaction range (UVB) and deep impact range (UVA). Lamp manufacturers shift the emission spectrum into the desired wavelength range by doping the electrodes with metal halides like gallium. Quartz glass shields between the lamp and the substrate filter out interference from other wavelengths. How to refresh UVC The short-wave UVC range, which only has low peaks, is the weak point in UV radiation technology because the emission spectrum shifts towards the longwave range as the lamp ages, so more energy is required to trigger polymerisation. The service life of a UV lamp as stated by the manufacturer is therefore not the same as its useful life in the original range. Although, within UVC, peaks from the passive, near-x-ray range drift into the range that plays an active role in curing, this feeding only partially balances the loss caused by ageing. As a rule of thumb it may be said that the optimum useful life of a UV lamp shifts from UVC to UVB and finally to UVA in the course of time. So our advice is to make sure that the first of the three end-of-press UV lamps in the delivery extension is always the newest one. Even if you have to change one of the other two lamps, it is better to move the first one to the central position to make room for a new first lamp, and during the next change move both these lamps along so that it is always the first lamp that is new. This ensures that the UVC radiation in the end-of- Significance of UV types and octaves for UV curing UV type Wavelengths Effect during UV curing Health, environment UVA (long wave) nm Penetrates thick layers of ink and coating Skin ageing, rapid tanning UVB (medium wave) nm Supports radical polymerisation Sunburn, permanent tan UVC (short wave) nm Triggers radical and cationic polymerisation by splitting the photoinitiators Ozone emission UV octave Wavelengths Range utilised by lamp during UV curing Differentiation UV-1 ( quartz UV ) nm Active range; triggers and supports polymerisation 400/300 nm near U V, 300/200 nm far UV UV-2 ( vacuum UV ) nm Passive range; feeds active range through wavelength drift towards UV-1 Process

16 UV technology UV lamps press dryer is always fresh. Most UVC radiation is required in the first lamp because this is where the curing process is triggered, whereas the purpose of the second and third lamps is to maintain or deepen the cross-linking process. The three lamps in KBA VariDry end-of-press dryers usually have a power profile of 40%- 80%-100% from front to back. Certain jobs with a high colour content demand a higher power level, primarily in the second lamp. KBA s VariDry the perfect solution Flexible, high-performance presses like the Rapida can only operate at maximum efficiency if the UV curing system has an equally high level of flexibility and per- Energy emission of a UV lamp UV lamps are available in two power levels, 160 and 200W/cm (400 and 500W/in). The ballast starts the lamp, stabilises power output and adjusts the radiation level (in real time) to production speed. The press operator can monitor each individual lamp, and preset its power level as a percentage value, from the console. The reflectors in a VariDry UV lamp do not focus the light on the substrate surface, as they do in other lamps, but diffuse it, causing it to flood the substrate. This simple principle can only be applied if the substrate surface is at the optimum distance from the lamp. Dispensing with specific irradiation geometries means that KBA is no longer bound to the dif- UV radiation by the lamp 30% Visible radiation by the lamp (light) 10% Heat radiation by the lamp (IR) 40% Heat radiation by the electrodes 10% Heat conduction by the quartz glass 10% Source: Grafix could rapidly nullify the cold-mirror effect (see box opposite). This is another reason why they can easily be switched from an interdeck to a final dryer position. Of course, heat management is still essential: both the lamp housing and the shutter have water-filled tubes running through them to conduct the heat into a circulating cooling system. This is so effective that the operator no longer has to wait for the lamp to cool down before replacing or repositioning it. The space-saving shutters in the VariDry UV lamps fulfil two functions: as reflectors when open and as light-screens when closed. What is the best way to measure UV radiation? Depending on the type of press line, some manufacturers install UV probes in the lamp housings as a more or less reliable method of monitoring lamp output in W/cm 2 and thus deducing the UV radiation level during production. The operator can use a portable probe to check other points in the dryer. As a rule, exchangeable flat or rod sensors are used with a peak sensitivity in the median range of UVA, UVB or UVC. There is some dispute about the usefulness of some measuring methods measuring free radicals, for instance, is a waste of time. It would be more helpful (and desirable) to measure the size and position of the peaks, ie to use spectrometry. This is the only way that the actual ageing of the UV lamps can be monitored consistently and in the case of inline measurement lamp efficiency in all three UV radiation wavelengths adjusted via the press controls. However, it would bump up the price of a UV dryer. At present the operating hours of each individual UV lamp are logged at the Rapida console a basic essential for reliable lamp utilisation. A general problem is that manufacturers of UV inks and coatings formulate them for specific wavelengths, so the lamp spectrum, not the highest peak or lamp power, may be the key factor. This, unfortunately, is one reason why energy consumption in the press room is often a lot higher than is really necessary. Loss of UV radiation intensity (%) through ageing formance, and is just as easy to handle. KBA s VariDry system fulfils all these criteria (see pp 6-9, Innovative, high-performance dryers ). KBA has achieved this by bringing dryer development and construction in-house, so it no longer has to compromise in any way on lamp design and integration into the press. The upshot is that VariDry modules are easy to use, easy to maintain and easy to position. ferent geometries for the various dryer positions. As a result the lamps can be positioned as interdeck or end-of-press dryers and are freely interchangeable a feature that is unique among dryer systems for printing presses. So dryer constellations can be configured to suit individual production specifications. Another difference is that the VariDry UV lamp has no dichroic coating, since fine dust particles UV lamp (Dr Hönle) in a KBA VariDry dryer. When the two flaps are open (top) they act as reflectors, when they are closed they act as a shutter (bottom). The ribbed flaps are water-cooled (blue pipes), the dryer is protected underneath by a glass shield A device from Dr Hönle for measuring overall UV lamp output 16 Process

17 UV technology UV lamps How cold should UV curing be? Everything is relative, and that includes the coldness of cold UV curing: even the temperature on the surface of a cold UV lamp can exceed 900 C (1,652 F). However, there are various types of UV lamp, and each suppresses secondary IR radiation in a different way, for example by combining various cooling systems. The simplest method is to extract the heat using cold air. Cold blown air is always present at a press and does not have to be generated specially. The drawback is that the lamp initially radiates the full amount of heat. In interdeck dryers the cold air is applied at the lamp and the impression cylinder (which is thus also cooled), in an end-of-press UV dryer it is applied after curing so as to cool the hot sheets immediately. Although KBA did not adopt this method for its VariDry system, third-party aircooled systems can be fitted in its presses as an option. Water cooling is much more widespread, and was KBA s preferred choice for VariDry dryers. With this method the substrate is warmed solely by residual heat, which is useful because heat promotes curing, while a combination of residual heat and a warm UV coating optimises spread and hardening. Inert chamber on a Rapida 105 Inserting an additional IR lamp before the final UV dryer has not proved to be effective; on the contrary, the IR radiation resoftens cured inks, which then attack the UV coating and can cause blocking. Inert UV systems exploit the fact that a nitrogen atmosphere promotes curing, so less radiation energy and up to 80% less heat is required. This is an ideal method to use when printing heat-sensitive substrates, eg synthetic sheets, because it reduces pile temperature by as much as 15 C (59 F). It also means that the press can run at a higher speed because the sheets do not have to dwell under the lamps for so long. A combination of water cooling and dichroic coating (Graphic: IST-Metz) The inert chamber is located above the impression cylinder. The technology required for a sheetfed offset press is much more complex than for a narrow-web press (where inert UV is a proven technology) because the substrates handled are generally thicker and the gripper bars run through the inert chamber at high speed, so it cannot be sealed so effectively. The first inert system developed by KBA in alliance with AdPhos-Eltosch and the SID (Saxon Institute for the Printing Industry) was fitted in a Rapida 105 at Belgian plastic printer Crea in For film printers, investing in inert UV is well worth the higher initial cost, especially since the storage costs for nitrogen are lower. AdPhos-Eltosch recently brought out an alternative to inert systems in the form of its TwinRay module, which is designed in such a way that only dichroic reflected radiation hits the substrate, so the temperature at the pile is half what it would be otherwise. Dichroic lamps are a form of cold lamp frequently found in sheetfed offset. Dichroic is a term used to describe material or treated material which reflects certain wavelengths of light (in this case UV) but transmits others (in this case IR).However, this is associated with a partial loss of useful wavelengths. Either the reflectors have a dichroic coating or the lamps are diverted over a semi-permeable cold mirror. In addition IR radiation, which would normally take a direct path to the substrate, is filtered out by a quartz glass sheet. Dichroic lamps are often used as interdeck Dichroic coating plus quartz glass filter (green) UV dryers (despite their compactness, which reduces dwell time), but not as endof-press UV dryers. This is partly because some residual heat radiation is desirable (see above) and partly because they cause the substrate to emit a lot of fine dust. If this dust settles on the dichroic coating and is not regularly removed,no more heat will be absorbed. This is why KBA favours water cooling for its VariDry lamps. However, uncoated and dichroic coated dryers are still available from other manufacturers (AdPhos-Eltosch, Grafix, Dr Hönle and IST-Metz), who combine them either with air or water cooling. In flexo printing there is another alternative to the cold mirror system for printing sensitive webs of plastic film: the excimer laser. Excimer is an acronym for excited dimer, ie a molecule composed of two identical simpler molecules (monomers), raised from the ground state to a higher energy level. Because of their lower intensity these laser-like UV lamps must be used in conjunction with an inert chamber. More powerful systems are not available for sheetfed offset. The big advantage: excimer lasers radiate in a single wavelength in packaging printing mostly 308nm of the xenon-chlorine compound and do not allow any IR radiation How a cold mirror functions to arise.the big drawback: this one wavelength cannot handle the necessary spectrum range from UVA to UVC, so special photoinitiators, inks and coatings are required. As a result this method cannot be used for current UV applications in sheetfed offset, including hybrid coating. Reducing the number of switching sequences extends useful life Regardless of whether you install a VariDry or other type of dryer with a Rapida press the lamps are automatically protected from needless switching sequences. Power control and adjustment to press speed are infinitely adjustable, so they have no detrimental impact on the lamp. Shutters eliminate the need to switch off the lamps when the press is stopped and switch them on again when the press restarts. They can even stay on when the blankets are being washed, at a stand-by output 50% below the maximum power level preset at the console. Power consumption can thus be reduced to a minimum while prolonging lamp life. It remains to be seen how well the quick-start GraphiCure GC9 UV lamps developed by Kühnast Strahlungstechnik and Baldwin Technology will perform with regard to useful life and UV spectrum. GC9 has no shutter, so the energy-saving compact fluorescent lamp must be switched off during press standstill. Dieter Kleeberg Process

18 UV technology Rollers, blankets, plates, paper Resistance of consumables to UV radiation during hybrid coating Press components, rubber rollers, printing and coating blankets, plates and substrates intended for UV printing must be selected for their resistance to the aggressive UV inks and washes used and, of course, to UV radiation.with hybrid coating this applies only to a limited extent because the relevant inks and chemicals are far less aggressive. As a result consumables for hybrid production are also suitable for conventional printing with aqueous coating, whereas with a pure UV printing process it is not possible to switch to any other kind of process. Resistance of rollers and blankets to swelling It is an established fact of UV production that the rubber coatings and layers on rollers and blankets (both printing and coating blankets) must not be susceptible to swelling, ie the UV inks and the equally aggressive UV washes must not cause the rubber to swell above an acceptable tolerance threshold. The inks used in association with hybrid coatings, by contrast, easily penetrate synthetics and polymer plate layers, even though their Blankets suitable for hybrid production (August 2005) Blanket Applications Substrates Strippable? Atécé PrintCare SF-A PrintCare SP/SS/N PrintStrip R606 Böttcher TOP 1001/1002/1003 TOP 4400 TOP 5400-N Contitech, Phoenix Xtra Print Conti-Air Ebony Conti-Air Spectral Phoenix Ruby Carat Phoenix Topaz Carat Phoenix Opal/Canyon Day International, Day Brasil davidm QL Stripper daygraphica 3610/EU 03 daygraphica NSP 03 Printec max Printec coater/stick n strip Duco, Birkan Multi Hybrid Superflex Superstrip FB/FB longer run Superstrip PB/UVPB Superstrip SB Adhesive TR Turquoise UV Compressible EPDM Folex Conventional or hybrid, UV or UV plus hybrid production Aqueous or UV coating Aqueous or UV coating Aqueous or UV coating Conventional or hybrid, UV or UV plus hybrid production Conventional or hybrid, UV or UV plus hybrid production Conventional or hybrid, UV or UV plus hybrid production Conventional or hybrid, UV or UV plus hybrid production Hybrid or UV production Conventional or hybrid, UV or UV plus hybrid production Aqueous or UV coating Aqueous or UV coating Conventional or hybrid production Conventional or hybrid, UV or UV plus hybrid production Conventional or hybrid production Aqueous or UV coating Conventional or hybrid, UV or UV plus hybrid production Conventional or hybrid, UV or UV plus hybrid production One-off aqueous or UV coating Aqueous or UV coating Aqueous or UV coating Conventional or hybrid, UV or UV plus hybrid production UV mode, some hybrid inks Paper, carton, cardboard, plastic, metal Paper, carton, cardboard, plastic, metal Paper, carton Paper, carton, cardboard, plastic, metal Paper, carton, metal Metal (with UV also paper, carton) Paper, metal Paper Paper, carton Paper, carton, cardboard, metal Paper, carton, cardboard, plastic, metal Paper, carton, cardboard, plastic, metal Paper, carton, cardboard Carton, cardboard, plastic, metal Paper, carton, cardboard Paper, carton, cardboard, plastic, metal Paper, carton Corrugated board Paper, carton, cardboard, plastic, metal Paper, carton, cardboard, plastic, metal Paper, carton, cardboard, plastic, metal Paper Paper, carton, plastic, metal Folacoat UV LT-D/LT-P Aqueous or UV coating Paper, carton, cardboard, plastic, metal yes Fujikura Graphics Luminus Conventional or hybrid, UV or UV plus hybrid production Paper, carton no I.M.C. Perfect Dot 4-SR Conventional or hybrid, UV or UV plus hybrid production Paper, plastic, metal no Kinyo Airtack M Adhesive Conventional or hybrid, UV or UV plus hybrid production Paper no MacDermid (formerly Rollin) Elastostrip Metro Prisco Priscolith Ebony Priscolith Hybrid Reeves Vulcan Combo Vulcan Folio Vulcan Image4U Aqueous or UV coating Conventional or hybrid, UV or UV plus hybrid production Conventional or hybrid, UV or UV plus hybrid production Conventional or hybrid production Conventional or hybrid, UV or UV plus hybrid production Conventional or hybrid, UV or UV plus hybrid production Conventional or hybrid, UV or UV plus hybrid production Paper, carton, cardboard, plastic, metal Carton, cardboard, plastic, metal Paper, metal Carton, cardboard, metal Paper, carton, metal Paper Paper, carton no yes yes yes ( 0.7/0.8/0.8 mm max.) no no no yes no no yes (approx. 0.9 mm) yes no no no yes (0.8 mm max.) no no yes ( 0.8 mm max.) yes (0.95/0.8 mm max.) yes no no Errors and omissions excepted. Some blanket manufacturers accredit their products for specific washes. Not all blankets are available worldwide, production may be discontinued at any time. KBA reserves the right to approve or reject certain products for hybrid applications. yes no no no no no no 18 Process

19 UV technology Rollers, blankets, plates, paper Typical structure of a printing blanket for conventional or hybrid production, taking Duco Multi Hybrid as an example: NBR top layer (green), micro-ground to 1 µm raw stencil depth, for rapid sheet release and ink transfer, low dot gain, high smash and edgecut resistance; thin stabilising fabric layer; thick compressible layer (black, now often with microspheres); low-stretch carcass (Graphic: Duco) Blankets like this Duco Superstrip that are suitable for both UV and aqueous coatings have a smooth, cast surface, an easy-peel stripping layer and a low-stretch carcass. The standard stencil depth is around 0.8 mm (Graphic: Duco) chemical composition resembles that of conventional inks more closely than UV inks. They can be washed off the rollers, blankets and plates with special hybrid washes which can also be used to wash off conventional inks following a change of operating The print-run stability of KPG s Sword Ultra thermal plate can be doubled to 1 million impressions by baking, but its penetrationproof exposure layer is resistant to hybrid and UV chemicals even without baking (Photo: KPG) mode. Extended contact with washes must cause no more than a minor change in the volume of the rubber and non-vulcanised polymers (swelling due to the absorption of chemicals or shrinkage due to their removal). Swelling and shrinkage, eg when changing from hybrid to conventional ink or from ink to washes, is unavoidable the decisive factor is that it must remain within the specified tolerance range. Rollers and blankets react more or less strongly to the various types of hybrid inks and washes available. That is why it is best to follow KBA recommendations and look for the accredited for hybrid printing label that indicates which inks and washes can be used together without causing problems with swelling. KBA only approves inks and washes which, when tested with standard rollers ie rollers that are otherwise normally used with conventional inks cause no change in volume at all or only within tolerable limits. At present only rollers supplied by German manufacturer Felix Böttcher, Cologne, have been found to comply. Otherwise hybrid rollers must be used, as some competitors specify, but that is not in keeping with KBA s definition of hybrid technology. Irrespective of this the blankets must be suitable for both hybrid and conventional/hybrid production. The topmost layers of these blankets are generally made of NBR (nitrile butadiene rubber). Some blankets with a compound surface made of nitrile-pvc-polymer are not only suitable for hybrid production but also expand the range of applications possible to UV, while blankets with top layers of EPDM (ethylene-propylene-diene monomer/ terpolymer, EPD rubber) are specific to UV inks. Marketing claims by some manufacturers that quality impairment must be accepted with universal blankets compared to dedicated hybrid or UV blankets may be true in some cases, though by no means in all. What is true is that contact with UV and conventional inks is no good for rubberbased materials in the long run an issue that does not arise with hybrid plus conventional operation. There is as yet no durable substitute for EPDM in the shape of a universally compatible blanket, which to a certain extent represents the best available compromise. As for the washes that are currently available, the following rule of thumb applies: hybrid washes are only compatible with nitrile-based materials for hybrid and conventional operation and would cause EPDM to swell. EPDM is only compatible with UV inks and UV washes. Plate stability during long print runs Hybrid presses can basically consume any brand of offset plate whose print-run stability, as for UV printing, can be enhanced by baking with the exception of coarse-resolution plates for newspaper production. It is only possible to bake analogue and digital plates that have a photopolymer or thermal polymer layer. Heating the developed polymer layer both seals and hardens the polymer surface, which impairs penetration by ink components and washes. This stops the layer peeling away under the impact of ink or if the blankets are washed between runs. It also eliminates the risk of post-copying caused by heat or UV radiation in the vicinity of the interdeck dryers. Most baked CTP plates are thermal plates. Fujifilm has even brought out the first bakable violet CTP plate, the Brillia LP-NV. A few thermal plates are penetration-resistant, and thus UV- and hybrid-compatible, even without baking. These include Fujifilm s VPU, which was specially developed for UV applications. Even so, some penetration-resistant plates can still be thermally fixed for longer print runs. In practice, Presstek s processless Anthem plate has proved equally suitable for UV and hybrid inks. And with the right hybrid inks, it is already Stripping a coating blanket by cutting with a CAD plotter and removing the non-image areas (Photos: Folex) possible to switch to waterless offset print production. Although waterless plates cannot be baked, this is not necessary anyway for short to medium print runs. Toray plates, which have a proven record of long-term performance in waterless UV printing, are also suitable, as are waterless plates from KPG (currently only available in North America). However, plates based on polyester are just not durable enough. There is as yet insufficient practical data on the compatibility with waterless hybrid inks of ablative plates such as Presstek s aluminium-based PEARLdry. Resistance of coating formes to chemicals UV coatings applied in hybrid production must be compatible both with the hybrid inks and, where relevant, with the overprint varnish that is used to create contrasting gloss effects. UV coatings require the use of a coating blanket that is resistant to both UV coatings and UV washes. These blankets are also suitable for aqueous coatings, which means they can be used in both modes of operation, hybrid and conventional. For spot coating with overprint varnishes, on the other hand, a hybrid-compatible offset plate is used instead of a blanket. Printers who are loath to use a costly photopolymer flexo plate Process

20 UV technology Rollers, blankets, plates, paper Analogue and CTP plates suitable for hybrid production (November 2005) Plate Imaging Development Hybrid application Baking for hybrid? Maximum width Agfa-Gevaert Meridian P51/P71 N91 N91v Thermostar P970/971 Anocoil Positive, UV (analogue or CTcP) Negative, thermal Negative, violet Positive, thermal (830/1064 nm) Wet Wet Wet Wet Commercials, packaging Commercials Commercials Commercials 830 T-Plate Positive, thermal Wet Commercials Yes N/a First Graphics (Kodak) FGN Negative, thermal Wet Commercials, packaging Yes N/a Fuji Photo Film Brillia LH-PCE/PSE Brillia LH-PIE/PJ Brillia LP-N3 Brillia LP-NV VPS-E/VPL-E VPU Huaguang (KPG licence) TN TP Indústria Brasileira de Filmes Positive, thermal Positive, thermal Negative, argon or Fd:YAG Negative, violet Positive, UV (analogue or CTcP) Positive, UV (analogue or CTcP) Negative, thermal Positive, thermal Preheat, wet Preheat, wet Preheat, wet Preheat, wet Wet Wet Wet Wet Commercials Commercials Commercials Commercials Commercials, packaging Commercials, packaging Commercials, packaging Commercials, packaging IBF-Million 2 Positive, thermal Wet Commercials Yes N/a Ipagsa Arte IP-21 Eco 88 Rubi T-50 Kodak Graphic Communications Group (formerly Creo) Positive, thermal Positive, UV (analogue or CTcP) Positive, thermal Wet Wet Wet Commercials, packaging Commercials, packaging Commercials, packaging Mirus PN Negative, thermal or UV (an./ctcp) Wet Commercials, packaging No, but possible 2080 mm Kodak Polychrome Graphics KPG DITP Thermal KPG EasyPrint KPG Electra Excel KPG Sword Excel KPG Sword Ultra KPG X54 Scorpion/Scorpion+ Konica Minolta Negative, thermal or UV (an./ctcp) Positive, UV (analogue or CTcP) Positive, thermal Positive, thermal Positive, thermal Negative, thermal Preheat, wet Wet Wet Preheat, wet Wet Wet Commercials, packaging Commercials, packaging Commercials Commercials, packaging Commercials, packaging Commercials, packaging Yes Yes Yes Yes Yes No Yes No Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes No, but possible No (waterless offset) Duros HST Positive, thermal Wet Commercials Yes N/a Lastra (Agfa-Gevaert) LT2 LVX Futura Oro PDI Positive, thermal Negative, violet Positive, UV (analogue or CTcP) Wet Wet Wet Commercials Commercials Commercials, packaging No, but possible Yes Yes Prisma 830/Steel 830 Positive, thermal Wet Commercials, packaging No (bimetal base) N/a Presstek Anthem Positive, thermal processless Commercials No 1118 mm Saverio Rief Therma Positive, thermal or UV (an./ctcp) Wet Commercials Yes 1660 mm Southern Lithoplate Cobra Negative, thermal or UV (an./ctcp) Preheat, wet Commercials, packaging Yes 1500 mm TechNova Gemini Plus Taurus Thermostar TN (Agfa P970) Toray Waterless TAC-RG5/RL7 Waterless TAN-E Waterless TAPD-G1/H-G2 Verona Lastre VELA LPN-100/LPV-100 VELA Universal Positive, UV (analogue or CTcP) Positive, UV (analogue or CTcP) Positive, thermal Negative, thermal Negative, analogue UV Positive, analogue UV Positive, UV (analogue or CTcP) Positive, UV (analogue or CTcP) Wet Wet Wet Wet Wet Wet Wet Wet Commercials Commercials, packaging Commercials Commercials, packaging Commercials, packaging Commercials, packaging Commercials, packaging Commercials, packaging Yes Yes Yes No (waterless offset) No (waterless offset) No (waterless offset) Errors and omissions excepted. Some plate manufacturers accredit their products for specific processors and developing chemicals. Not all blankets are available worldwide, production may be discontinued at any time. KBA reserves the right to approve or reject certain products for hybrid applications. CTcP used here as a synonym for UV imaging of conventional plates with a CTP recorder is a registered trademark of BasysPrint, Boizenburg (Germany)! for a final spot coating can fall back on a strippable coating or printing blanket. But it is advisable to check the maximum stencil depth, which is defined by a stripping barrier beneath the top Yes Yes layer. If the coating blanket is to be re-used, blanket manufacturers recommend clamping it on N/a N/a N/a 2000 mm 2050 mm 2050 mm 1230 mm 1230 mm N/a N/a N/a N/a N/a N/a N/a 1560 mm N/a N/a 1512 mm 1512 mm N/a 1660 mm N/a N/a 1030 mm N/a N/a 1610 mm 1610 mm 1610 mm N/a N/a fairly tightly with a torque wrench. Printing pressure should be set as light as possible to allow 20 Process

21 UV technology Rollers, blankets, plates, paper the coating to spread evenly on the substrate. Robinson test helps pre-empt complaints Packaged goods with odour or taste impairments caused by the carton or cardboard packaging are a frequent cause for complaint,and not just in UV printing.the Robinson test is a good way of avoiding this pitfall and prevents costly materials from being wasted.this sensory test is recommended if new substrates or new permutations of substrate,ink and coating are to be used,and for this reason the test should be carried out in two stages: on the individual consumables prior to print production and collectively after production of a small, authentic hybrid print run.when conducting the test you should bear in mind that odours may develop over a period of time as a result of reaction with the oxygen in the ambient air. It is best to prepare a number of samples so that several people can participate.the testers must compare the odours emitted by the different samples relative both to the other samples and to the reference (odourless material or product). Samples and references are placed in thick-walled glass containers in which there is a small reservoir of water to provide 75% relative humidity.the ageing process is accelerated so that potential odours will be detectable within 48 hours.the testers subsequently assess the differences in odour according to a five-level valuation scale:0 = none;1 = scarcely perceptible;2 = perceptible but scarcely definable; 3 = definable; 4 = strong. Half-points are possible.the testing committee, which is convened as required, comprises experienced specialists recruited from the ink, carton and cardboard industry, printing companies (print buyers) and users (packers, retailers, consumers). Inks for hybrid production (November 2005) Manufacturer Ink series Comments Arets Graphics Eckart America Epple Gans Ink & Supply Huber Group Jänecke+Schneemann Sicolor Sun Chemical/DIC Sun Chemical Toyo Ink Toyo Ink Unionprint Van Son Xsys Print Solutions Xsys Print Solutions EXC Process Hybrid MetalStar Hybrid Starbrite OS UV-Hybrid 4-Color Process Hostmann-St. Reflecta Hybrid Supra UV Hybrid Sico Brite Sun Cure Hy-Bryte/Daicure Hy-Bryte Sun Cure Hy-Bryte Max FD Hybrid Aqualess SOY FD Hybrid Eco-SOY VersaCure Quickson UV Coatable Flint-Schmidt Gemini Process K+E Novabryte BF Process Not recommended, too aggressive (UV properties) Metallic ink for final printing unit, not yet tested KBA/Fogra-accredited Not yet tested Modification recommended after Fogra test KBA/Fogra-accredited KBA/Fogra-accredited KBA/Fogra-accredited Like Sun Cure Hy-Bryte, but not yet accredited Waterless offset ink, passed KBA tests Not yet tested Not yet tested Not yet tested KBA/Fogra-accredited KBA/Fogra-accredited Errors and omissions excepted. Not all inks are available worldwide. KBA reserves the right to approve or reject certain products for hybrid applications. Accreditation lapses with any change of formula. Washes for hybrid production (November 2005) Wash Felix Böttcher Böttcherin Hybrid Day International Varn Hybrid-Wash DC DruckChemie Hybrid 1.0 Hybrid 3.0 Fuji Hunt/DS Druckerei Service Novasol HB 8 Novasol HB 10 Vegra Schnellreiniger E 939 Fogra accreditation test Passed Not yet tested Passed Not yet tested Passed Passed Passed; formula is currently being modified and resubmitted for accreditation Not all washes are available worldwide. The compatibility of a wash depends on the type of ink, the ink series, and the rubber used in the blankets and rollers. KBA reserves the right to approve or reject certain products for hybrid applications. Fogra certifies washes in accordance with an industry initiative on solvent reduction. Tests to date focused on the compatibility of consumables for sheetfed offset presses. Future tests will also examine the effectiveness of washes. By the end of 2005 a standard testing method had been devised and five washes tested. Accreditation lapses with any change of formula. References (left) and substrate samples (right) during the Robinson test (Photos: M-real) Resistance of substrates to UV radiation Since the use of plastic and metal as a printing substrate is largely confined to UV applications, it is the specifications for paper, cartonboard and cardboard that are of primary interest as far as hybrid coating is concerned. They are essentially the same as for pure UV printing, since most of the problems that may arise are caused by UV radiation. Operators of hybrid presses should therefore rely on the experience and handling instructions of their paper vendors. A cardinal rule for both UV curing and IR radiation is that dryer power should be set to the absolute minimum necessary, because it is a well-known fact that paper is extremely sensitive. The heat generated during drying makes it shrink, and UV radiation can trigger undesirable chemical reactions such as yellowing. Another problem is that folding can cause the inherent paper or board coating to crack. There are two ways to prevent this. One is to use a flexible UV coating, but only one recommended by the paper manufacturer. The second is to crease heavier stock carton and board weighing 150gsm (102lb book) or more prior to folding. But if you do decide to crease the stock, make sure that the equipment you use is neither worn nor wrongly adjusted, otherwise you will merely exchange one evil for another. One quick and simple method for checking the creasability of coated cartonboard is to use a letterpress platen to simulate the folding sequence. Some printers have found that spraying the crease with a mixture of water and alcohol is an effective way to prevent cracking. A third issue, caused by the chemical decomposition of the binder in the paper coating under UV radiation, is odour emission. But it is rarely possible to determine instantly whether it is the paper coating, the ink or the inline coating that is responsible for the smell. This is because it is possible for quite unpleasant smells to be emitted by a combination of components which, individually, are totally odourless. Even fount solution and printing powder can contribute to odour emission. Additional causes may be microbial infestation due to improper transport and storage conditions, packaging that is inappropriate for the type of substrate, excess resin in the pulp, or contaminated papermaking equipment. By consulting your paper vendor on suitable UVtested substrates you should at least be able to eliminate the binder as the cause prior to production. Many paper manufacturers are happy to accommodate customer requests to test specific combinations of materials. You should also check for proof of quality control during manufacture and delivery. The dual drying properties of hybrid inks mean that, unlike UV printing, substrate absorbency is pertinent only in conjunction with the UV coating. Even here, the thickness of the coating film means that its impact is of marginal interest. So the risk of inadequate hardening due to binder depletion arising from over-rapid draw-back by the coating does not play any significant role. Dieter Kleeberg Process

22 UV technology Resistance of rollers, blankets, plates, paper Hybrid-compatible blankets and washes KBA s hybrid philosophy holds that hybrid inks should be printable with blankets that are also suitable for conventional inks. It follows that the washes used to clean them off the blankets should also be suitable for conventional inks. In some cases the press operator may even plump for blankets with additional resistance to pure UV inks, but this universal compatibility is not essential. What is essential is long-term stability in dual-mode operation, so the inks and washes must cause no excessive swelling or shrinkage of the rubber on the blankets and rollers in either conventional or hybrid mode. It would therefore be an obvious advantage if hybrid-compatible blankets and washes were developed in lockstep with each other. Day International s approach is a good example. DayGraphica 3610: the standard blanket for hybrid production In at the start The various companies currently engaged in optimising the hybrid printing process are vigorously pursuing innovation in order to ensure that hybrid technology can deliver the performance demanded. Day International was one of the first to take up the challenge associated with the many potential applications of the hybrid process. This commitment has paid off: today hybrid users can choose from a whole raft of Day International hybrid products with proven compatibility. But while these products, taken individually, are highly effective, combining them can give rise to major problems. The blankets, in particular, must fulfil widely diverse criteria. Day International has found that close collaboration with press manufacturers, UV users and the ink industry is the only way to develop rubber compounds which, in conjunction with inks and coatings, deliver an optimum image on different substrates. Blankets for hybrid presses Day International developed three blankets which are now widely used for hybrid production: daygraphica 3610, day- Graphica EU 03 and daygraphica NSP 03. These have been joined by a strippable coating blanket, davidm QL Stripper, which can be used to apply an aqueous coating to conventional inks and a UV coating to hybrid inks, so it is suitable for both the modes of operation possible with hybrid presses, and the wide choice of substrates for which they are designed. The most popular of Day International's blankets is the daygraphica 3610, which generates less heat and is fully compatible with hybrid inks. The face compound is nitrile rubber, which allows an ideal range of contrasts to be created on the printed sheet. DayGraphica EU 03 has the same underlying structure but a different face compound. For hybrid operators whose work entails printing a lot of different jobs on various substrates this blanket offers some specific benefits. Very good ink transfer and a long service life are two of them. Day International's most recent hybrid-compatible blanket, day- Graphica NSP 03, is universally compatible because the face compound is made of nitrile and PVC, so it can be used for conventional sheetfed offset, hybrid and pure UV production. It allows printers to switch freely between conventional plus hybrid and conventional plus UV with no impairment to quality. Exploiting synergies in wash and blanket development The scanning electron microscope images at the bottom of the next page show the effect a wash can have on the rubber face of a blanket. With an aggressive wash it can be seen that the volume of the rubber layer changes because the original molecular face structure is destroyed. Aggressive or unsuitable washes can also destroy or dissolve certain additives that make the rubber compound harder or more elastic. In practice this can have a severe impact not only on blanket performance, service life and inking rollers but also on ink-splitting and thus print quality. With a compatible wash the rubber retains its original properties. A joint project with chemicals manufacturer Varn Products, a member of the Day Group, has enabled new synergies to be exploited in the development of blankets and pressroom chemistry. This is because Day International and Varn focus on the mutual compatibility of their products right from the initial development phase, enabling them to offer high-quality, mutually compatible washes and blankets that deliver an optimum performance within the printing process (see table). DayGraphica EU 03: suitable for a broad range of products Washes for hybrid presses Two crucial criteria for the costefficiency of a wash are that it must clean the rubber rollers and blanket surface thoroughly and rapidly restore ink transportability when the ink train is restarted after the washing cycle. Varn Products offers three different hybrid washes with such properties: V60+ Wash, AIII Hydro-Solv and Hybrid-Wash. While the first two products have already fulfilled the accreditation criteria stipulated by Fogra and all the major manufacturers of printing presses and washing systems, Hybrid-Wash is still being reformulated in accordance with KBA recommendations. (Editor s note: Fogra s accreditation tests on hybrid inks revealed that Hybrid-Wash W6 in the chapter on pages 35-39, Fogra tests hybrid inks met the minimum washability criteria in most cases. However, the impact of washes on blanket swelling was not the object of the ink tests. Tests on washes, a basic condition for their 22 Process

23 UV technology Resistance of rollers, blankets, plates, paper DayGraphica NSP 03: for conventional plus hybrid operation, conventional plus UV operation or for pure hybrid operation in conjunction with Hybrid-Wash Before a wash comes onto the market it must pass a series of stringent laboratory and practical tests Applications for hybrid and UV products manufactured by Day International and Varn Products Blankets, washes Conventional inks Hybrid inks Pure UV inks Rubber base of face compound DayGraphica blanket Varn wash Rubber base of face compound DayGraphica blanket Varn wash accreditation, include the degree to which they cause roller coatings, the rubber in the washing systems or the face compounds of the rubber blankets to swell.) Hybrid-Wash was developed for printers whose job structure Nitrile butadiene rubber (NBR) 3610, EU 03 V60+ wash, AIII Hydro-Solv Nitrile/PVC compound NSP 03 AIII Hydro-Solv Hybrid-Wash does not demand the ability to switch between hybrid and conventional inks, and who therefore print exclusively with hybrid inks. But because vegetable oils, which are compatible with nitrile/pvc rubber compounds, EPDM Eclipse UV wash are used as solvents, blankets and rubber rollers must be designated as suitable for conventional plus UV production. This wash, which is not classified as a hazardous substance under EU law, contains no volatile organic compounds (VOCs) and therefore has just a mild odour. It has a flashpoint of over 100 C (212 F). V60+ is a cost-effective wash classified as hazard class AIII, and was developed for use with both conventional and hybrid inks, ie in conjunction with nitrile butadiene rubber (NBR). Another wash in the same category is AIII Hydro-Solv, a version of Hydro- Solv suitable for all types of offset ink conventional, hybrid and pure UV. Unlike most other hybrid washes it is based on mineral-oil distillates. This is one of the reasons why it is suitable both for nitrile butadiene rubber and for nitrile-pvc compounds on rollers and blankets. As the name indicates, AIII Hydro-Solv is water-miscible. It has a flashpoint of over 62 C (144 F), so it is not classed as a hazardous substance for transport and storage purposes. Simon Bornfleth, Georg Fritz, Day International/Varn Products, Reutlingen Face compound of a rubber blanket viewed under an electron microscope. The surface and volume of the sample on the left remained largely unchanged after 88 hours of immersion in a compatible wash at a constant temperature of 60 C (140 F). The sample on the right, which was immersed in another commercially available but more aggressive wash, showed significant structural changes after just 16 hours at room temperature Process

24 UV technology Resistance of rollers, blankets, plates, paper Substrates for hybrid applications The best type of stock to use for hybrid applications is glossy coated paper or board because it enhances the gloss effect of the UV coating. The composition of the coating applied to the paper or board during manufacture, and the smoothing action of the calender, impart certain chemical, physical and mechanical properties to the substrate which influence its suitability for UV curing in conjunction with hybrid inks and UV coatings as well as its creasability and foldability in the finishing department.the Schneidersöhne Group, a German paper and board specialist, has investigated the properties required for hybrid production. Gloss test charts and other prints created using hybrid inks and coatings Finding the ideal combination The print quality delivered by a press depends to a large extent on the substrate used, since this is what gives print its visual impact. Not every type of paper boasts the properties essential for a trouble-free production run using hybrid inks. The interaction of the substrate with the ink and coating during hybrid production has a fundamental impact on the adhesive strength of the ink on the paper, the ruband scratch-resistance of the ink film and the gloss level of the oilbased varnishes and UV coatings used. And since not every combination of substrate, ink and coating is equally appropriate, finding the best one can dramatically enhance the image delivered. It is also advisable to carry out print tests with various permutations of the systems involved in the process, so as to optimise their interplay. Mechanical factors influencing gloss quality Pressroom experience has shown that coating or varnishing delivers the highest gloss levels when applied to substrates with a particularly smooth surface. Glossy paper like Schneidersöhne s LuxoMagic is an ideal basis. LuxoMagic was used in the gloss test that KBA ran on hybrid-printed stock (see chapter on Gloss and its measurement using the KBA test chart ). The differences in the various types of glossy coated paper on the market essentially lie in their inherent gloss levels, which are determined by the coating pigments and/or calendering process used. A gloss finish is created by coating a web of paper a number of times and running it through a calender. Supercalenders impart gloss by subjecting the paper to a combination of high pressure, moisture and high temperatures as it runs through the nips the mechanical contact points between the rollers in a succession of calenders. The pressure exerted at the nips makes the coated paper surface denser and smoother. The colour pigments for the coating, and the degree of mechanical pressure exerted during the calendering process, can be adjusted to obtain the precise level of gloss required. The degree of substrate compression that necessarily occurs during calendering depends on the paper s thickness and specific volume. Some problems associated with glossy coated paper, for example cracking during folding, may originate in the manufacturing process. This is why heavier stock (150gsm or 102lb book upwards) should be scored prior to folding so as to create a flexible hinge. Paper that has been severely compressed is less elastic (ie stiffer) than similar paper that has been glazed more gently in a softnip calender. On top of this the UV coating used must form as flexible a film as possible: if it is too brittle it will crack and impair the fold. Brittleness and dimensional stability Coated stock may also become brittle during hybrid print production followed by radiation curing. This is because heat is generated as a by-product of the chemical and physical reactions triggered to dry the ink. The heat draws moisture from the paper, and as this dries out the individual fibres shrink and lose their elasticity. At the same time the ink film hardens and the dimensions of the printed sheet become fixed. In some cases moisture absorption by the substrate during conventional offset production, or a partial extraction of moisture during thermal air drying, may cause an undesirable distortion in sheet dimensions. The choice of pulp, the ratio of long running fibres to short cross fibres, the composition of the coating base paper and its inherent moisture content can all impair the dimensional stability of the sheet. Semi-matt and matt coated stock Hybrid inks and coatings can be applied to semi-matt as well as glossy coated paper, and the manufacturing technology involved is much the same: it is the choice of coating colour pigments and calendering pressure that creates the semi-matt effect. Softnip calenders are commonly used because they glaze or semi-glaze the surface gently, with much less mechanical pressure than a supercalender. In exceptional cases customised rollers are used to create a specific matt surface. Even here, multiple passes are the norm in order to create an extremely uniform, close-grained surface. The way matt coated papers are processed makes them less suitable for hybrid production. The matt effect on the surface is created solely by the coating pigments used, most commonly calcium carbonate pigments whose geometric structure is a bizarrely shaped polygon. Their uniform distribution over the surface of the substrate gives it a fine yet porous and open structure which diffuses incidental light to impart an impression of mattness to the observer. Matt coated papers are not calendered and need not be multiple coated. If, despite its shortcomings, matt coated paper is specified for a UV or hybrid print job, then a preproduction test run is strongly recommended because prior treatment with primer or the addition of antipenetration 24 Process

25 UV technology Resistance of rollers, blankets, plates, paper agents may well prove necessary in order to achieve a satisfactory impression. Coated stock promotes process stability The quality of coated paper from different manufacturers largely depends on the composition of the coating base paper, the formulation of the coating colour and the manufacturing technology used. Basically there are some outstanding coated papers available today which satisfy market demands and are hybrid-compatible. These papers not only have optimum penetrating properties, and thus successfully bridge the divide between the desire for a high level of gloss gain by the ink and the need to tumble the pile as soon as possible for perfecting: they also promote process stability at the high press speeds of 18,000 sheets per hour typically achieved by new-generation hybrid presses. Uncoated stock unsuitable By contrast, the absorbency and surface characteristics of uncoated paper make it totally unsuitable for printing with hybrid inks and coatings. The application of a UV coating on uncoated paper demands a special prior treatment of the surface with a primer, either spot or solid, to fix or reduce substrate absorbency. The penetrative properties of uncoated papers are fundamentally different from those of coated stock. Wetting coated paper with highly viscous ink triggers a phase break in which the fluid components (mineral or vegetable oils) are separated out of the ink and penetrate the coated surface. Wetting uncoated paper, however, produces no phase break: the ink dries progressively, and this process takes much longer. Paper under a raster electron microscope Surface of a glossy coated paper Interaction in hybrid applications Various interactions have also been observed between the substrate and the other process components during hybrid applications. These relate to the adhesion of hybrid inks and coatings to the paper and the impact of UV radiation curing on unprinted areas of the sheet. UV radiation destroys optical brighteners. A substrate with a high level of basic whiteness will have a lower proportion of optical brighteners, so the loss of white will be correspondingly small. Paper or board with a high proportion of optical brighteners, however, will tend to yellow when subjected to UV radiation and the heat that this generates, because the brighteners in the coating will lose their optical impact over a period of time and the unprinted areas will revert to their (lower) natural level of whiteness. The quality of the optical brighteners, and their stability under UV radiation, therefore exert a major impact on the quality of the printed product. Surface of a semi-matt coated paper Cross sections of the two types of paper, which both weigh 135 gsm, clearly show the difference in thickness and density caused by calendering Surface of a matt coated paper Porous surface of uncoated paper Another form of yellowing, which occurs with overprint varnish and is therefore specific to the areas to which it is applied, is particularly noticeable on the back of a perfect-printed sheet or in a graphic. This undesirable phenomenon, too, is caused by the partial or total destruction of optical brighteners, and the loss of whiteness is perceived as a quality flaw. Thick films of ink or coating have just as critical an impact as excessive UV radiation. Even disregarding the inherent odour of UV inks and coatings, hybrid products have a distinctive, persistent odour that not everyone finds acceptable. Some UV-printed products have such a powerful smell that they may be considered a form of pollution. It emanates from the products of volatile fission in the UV components, which accumulate as gaseous monomers at the binding agents contained in the coloured coating on the substrate surface. The volatile monomers in the various types of UV ink react in different ways when released during radical polymerisation. Binding agents may retain the monomers for different lengths of time or be destroyed by them. A basic essential for eliminating, or at least minimising, print odour is to ensure that the radiation system thoroughly cures both the UV inks and the UV coatings. A judicious combination of compatible consumables and an ongoing dialogue with the providers of the technologies involved in hybrid production have already enabled the process to deliver prints that combine an outstanding image quality with minimum odour. Christoph Weinert Schneidersöhne Group For further information please contact the author on , christoph.weinert@schneidersoehne.de Process

26 UV technology Hybrid inks Specifications for hybrid inks Higher gloss with UV coating If a print job specifies a high gloss level of 85 or more, then a UV coating is the only possible alternative to film lamination. But a UV coating can only deliver such a high gloss level if the substrate to be coated is completely dry, otherwise the coating will penetrate the ink film. And once it has been applied, the coating must have plenty of time to spread and form a smooth, glossy surface. There is a choice of four methods for applying a UV coating: 1.Offline on a dried film of any type of ink; 2.Inline on an aqueous primer applied to a film of wet conventional ink and dried in an interdeck dryer (two-coater press); 3.Inline on a pre-cured film of UV ink; 4.Inline on a pre-cured film of hybrid ink. Epple provides suitable inks, washes and overprint varnishes Epple s Starbrite hybrid inks, which have been on the market for a number of years, unite the properties of conventional inks and UV inks, so they can be finished inline with a high-gloss UV coating. As a result printers can enjoy the benefits of UV inks high-speed curing and compatibility between the binding agent and the UV coating without having to install a pure UV press. Using Starbrite printing inks and Starbrite 1300 hybrid wash it is possible to print with normal rubber rollers and blankets; with no further modification of the printing units for UV applications; with an IPA-free fount solution. Multiple tests conducted in association with all the major roller manufacturers to check roller and blanket swelling have shown that Starbrite inks and washes deliver the best results in conjunction with conventional, as opposed to UV-modified, rollers and blankets (see box). The suitability of Starbrite inks for hybrid production was confirmed at the second hybrid user meeting, in April 2005, where they were awarded the KBA/Fogra seal of approval. But setting aside the impact of inks and washes on rubber-based materials, the best offset plates to use are baked or UV-compatible ones. As far as gloss levels are concerned, the impact of the substrate, degree of ink coverage and colour imposition is negligible. As with all inks, slight changes occur in the gloss level immediately after impression. Users have even noticed positive changes during oxidation in the pile. Contrasting gloss effects can be created by using Starbrite inks with various compatible matt overprint varnishes which can be applied as a spot coating in the offset register prior to a full-solid UV coating. For this particular application Epple offers Starbrite 1290 and 1579 yellow-resistant coatings both of them for an orange-peel effect and 1523 for a smooth matt gloss. The key to success with the hybrid printing process apart from choosing the appropriate press technology is to use the right hybrid inks. These not only dry by oxidation and penetration, like conventional inks, but also cure by radiation, like UV inks, and accept a direct UV coating without a primer. This chapter examines the typical characteristics and specifications of hybrid inks, taking as an example one of the ink types accredited by KBA and Fogra: the Starbrite series developed by German manufacturer Epple in Neusäss. The Starbrite product range also includes washes and overprint varnishes specially formulated for hybrid inks % 70% 70% 100% 100% 70% 100% 100% M+K C+M CMY M+K C+M CMYK CMY CMYK =40% =140% =210% =200% =200% =280% =300% =400% 0% Gloss levels, by colour content and area coverage, of Starbrite hybrid inks with UV coating (green) and conventional inks with aqueous plus UV coating (blue) 72 hours after application at a speed of 10,000 sheets per hour on GD2 double-coated gloss cartonboard. The median gloss level is higher with a hybrid coating (90.7) than with two coatings (88.3) and the influence of the ink noticeably weaker (scarcely any fluctuation in gloss levels). The image printed was the KBA test chart (see chapter on gloss, page 30) Storage and setting The stability of hybrid inks during storage depends on the ambient temperature and the chemical properties of the pigments. The higher the storage temperature, the less stable the inks. In a large-scale series of tests Epple pinpointed pigments for both process and special inks that were storable for a minimum of six months at a maximum temperature of 25 C (77 F). Starbrite process inks are formulated print-ready for the sequence black cyan magenta yellow. Dot gain and print quality are largely comparable with those of conventional printing inks. Problem-free ink/water balance When it comes to achieving the correct ink/water balance, Starbrite inks behave like conventional printing inks. And unlike earlier UV inks they are not excessively hydrophilic. They are also less prone to emulsification and tinting. It is always wise to analyse the water used: depending on the quality it may be necessary to alter the composition of the fount solution. In theory, any conventional dampening additive can be used, alcohol substitutes included, with the exception of siccatives. Print tests have shown that fount solution containing siccatives can cause the ink to dry on the rollers, which can impair print production. Epple offers dampening additive Waterfit 1239 for use with hybrid inks. Hybrid inks and conventional inks have different tack The rheological properties of hybrid inks most noticeably viscosity, tack and flow display the same mutual dependence as those of conventional inks, so it 26 Process

27 UV technology Hybrid inks Swelling: testing the tolerance of consumables for conventional applications Rubber consumables were tested for swelling (+) and shrinkage (-) during exposure to Epple s Starbrite hybrid inks and Starbrite 1300 wash. In every instance consumables developed for use with conventional printing inks were found to be the most suitable, in accordance with KBA s hybrid philosophy.starbrite inks and wash proved to be the best combination because they were compatible with the same consumables. Results of tests with hybrid inks: Characteristic curves for black, cyan, magenta and yellow Starbrite inks printed on a Rapida 105 in KBA s Radebeul showroom at full-solid densities of 1.89, 1.56, 1.54 and Differences in dot gain compared to a conventional series are so small that they require only a minor modification of the curves in pre-press Rubber coatings on Westland rollers: Werograph (standard), Weromix (conventional/uv),wero-uv Results of tests with hybrid washes: 1. Rubber coatings on Böttcher rollers: standard rollers +0.25%, conventional/uv rollers +0.65%, UV rollers +0.45% 2. Rubber coatings on Westland rollers: standard rollers -0.2%, conventional/uv rollers -0.5%, UV rollers +30.5% 3. Rubber seals in automatic Baldwin washing systems: swelling after the first day +0.02%, after the second day 0% and after the seventh day +0.04% (knockout criterion: dimensional changes due to swelling must be less than 1% after 7 days) is difficult to change one value without influencing the other two. Of these three variables, tack is the most important. It is a measure of the force required to split the ink on its way from the ink trough to the substrate via the inking unit, plate and blanket. With hybrid systems, dry tack (ink without water) is slightly higher than with conventional inks, while wet tack (ink with water) is slightly lower. Dry and wet tack must be carefully adjusted relative to each other in order to achieve a flawless result. Viscosity, ie the degree of fluidity of the ink, depends on the internal friction acting against printing pressure or shear stress. The impact of shear stress means that the ink is exposed to shear at a constant speed. The quotient of shear stress and shear speed is known as dynamic viscosity, measured in Pascal x seconds. Viscosity measurements for product development are also very important when it comes to describing in detail and optimising other properties such as flow, yield point, relaxation time etc. Determining odour using a gas chromatograph The odours emitted by prints are typically generated by volatile aldehydes, or alkanes, which are carbon compounds containing the functional molecular group -CHO. To determine the level of aldehyde, the Starbrite inks and overprint varnish were applied to solid bleached sulphate board and examined using gas chromatography. In the first experiment a Starbrite process ink not declared as low-odour was compared with an oxidative process ink. In the second experiment a low-odour Starbrite process ink was compared with a low-odour conventional ink. The volatile aldehydes being traced were butanal (which has 4 carbon atoms), pentanal (5), hexanal (6) and heptanal (7). The aldehyde that emits the strongest odour is hexanal. The hexanal spike with conventional inks is clearly evident: with non-low-odour Starbrite ink, on the other hand, it is very much smaller. The two low-odour process inks emitted identical volumes of hexanal. The hexanal levels in the non-low-odour Starbrite inks approached the range of conventional low-odour inks, and in the low-odour Starbrite inks they were precisely within the range. Even so, if hybrid inks are used to print food packaging it is best to make sure that, as with conventional inks, the contents do not come into direct contact with the printed surface. Gas chromatography provides an absolute measurement, unlike the Robinson test, which is a highly subjective, relative sensory testing method and therefore impossible to reproduce with any degree of precision (see chapter on Resistance of consumables to UV radiation during hybrid coating, pages 18-21). However, a Robinson test is recommended from time to time because it encompasses the entire product paper, ink, coating, fount solution and even storage. Norbert Lenzgeiger, Epple Druckfarben The gas chromatographic analysis revealed that the concentration of aldehyde (in mg/m 3 ) in Starbrite ink with overprint varnish (blue) was lower than in the substrate (200gsm Iggesund Invercote solid bleached sulphate carton, green) and therefore negligible Gas chromatogram: the level of hexanal, which is the most pungent ingredient in ink, is many times higher in conventional inks (red) than in non-low-odour Starbrite inks (blue), and the same in low-odour standard inks (green) as in low-odour Starbrite inks (black) Process

28 UV technology UV coatings UV coating specifications In hybrid production, UV coatings are used in the final coater to create a high gloss. They are applied as a full solid, wet on wet either directly on the hybrid inks or on an oil-based overprint varnish (OPV) functioning as a spot varnish. The interaction between the two contrasting types of coating, OPV and UV, gives rise to a number of spot effects, while their different surface tensions can be exploited to create various structural and haptic effects. But both UV and hybrid coating must perform to specific standards. Compatibility with hybrid inks The first relates to the coatability of hybrid inks, which must contain binding agents that dry by oxidation and others that cure by cross-linking. Hybrid inks, unlike conventional inks, can deliver high-gloss effects provided that specially formulated UV coatings and if hybrid inks are also applied in conventional production mode the appropriate water-based coatings are used. Because the coating is the only pure UV consumable processed and UV. On conventional inks, ie inks that dry by oxidation and/or penetration, a UV coating can only be applied in conjunction with an aqueous primer. This normally requires a two-coater press and the average gloss level achievable is around 70. With hybrid inks there is no need for primer and thus a second coater, and the median gloss level is around 90. For direct UV coating, UV-reactive inks must be used which are much harder to print than hybrid inks and deliver gloss are the substrate, the volume of coating applied and the position, quantity and efficacy of the individual UV lamps. Compatibility with other coatings to create contrasting gloss effects High-gloss UV coatings must be compatible not only with hybrid inks but also with the oil-based overprint varnishes specifically formulated for hybrid production. The precise degree to which the two coatings accept or repel each other can be controlled by adjusting the surface tension. For example, to create a matt or collotype grain effect on certain areas a dampened offset plate can be used in the last printing unit to apply an OPV, which repels UV coatings. The high-gloss UV coating is applied We believe that the technology to support visual effects and hybrid production is one of the most intelligent developments of the past 50 years in the print industry. Albert Uhlemayr, the author, speaking at the first KBA hybrid user meeting in September Vegra has promoted hybrid coating right from the start as a full solid, but cannot adhere to the OPV. This creates a contrast between the matt or granulated effect of the OPV and the high gloss of the remaining areas. Since coatings applied in a single workflow should always be mutually compatible, it is best either always to use the same brand or to ask various manufacturers for a list of coatings that are mutually compatible. The Vegra group, for example, offers a combination of oil-based overprint varnish 3606 and highgloss UV coating 1038 for hybrid Viscosity of UV coatings KBA product manager Anne-Kathrin Gerlach and head of sheetfed offset marketing Jürgen Veil checking the gloss levels possible with Vegra UV coatings on a hybrid press in the press, the other press sections do not have to be UV resistant. One of the biggest advantages of hybrid inks (at least in KBA s system) is that conventional roller coatings are perfectly adequate, so the rollers do not have to be protected with a layer of EPDM as they do in pure UV print production. In practice, inline UV coatings are used with three different types of ink: conventional, hybrid levels of 80-plus. The highest gloss levels with UV coatings are achieved with offline coating systems, where the type of ink is immaterial because it is completely dried in advance. Whatever the process, the level of gloss actually achieved depends on the dwell time. This in turn depends on printing speed and the length of the dwell section, so a double delivery extension is advisable. Other factors Viscosity can be determined with a DIN immersion-type run-out cup. The cup is filled up to the mark and the coating timed as it runs out through the 4mm (0.15in) hole in the base at an ambient temperature of 20 C (68 F). UV coatings should take no less than 25 seconds (or the application will be uneven) and no more than 65 seconds (or the coating may spray). Viscosity is influenced by temperature and diminishes as the temperature in the coater increases in continuous operation, so this loss of viscosity must be factored in. At the KBA hybrid user meeting, 45 C (113 F) was discussed as being the optimum temperature for UV coating. But because the optimum storage temperature is lower, the coating should not be warmed prior to pumping. 28 Process

29 UV technology UV coatings Resources/alliance partners We wish to thank all our alliance partners for their invaluable support in advancing and optimising hybrid technology for shopfloor applications. Associations, certifying institutes Berufsgenossenschaft Druck und Papierverarbeitung, D-Wiesbaden ( Fogra Forschungsgesellschaft Druck e.v., D-Munich ( Inks and coatings Epple Druckfarben AG, D-Neusäss ( Flint-Schmidt GmbH & Co KG, D-Frankfurt/M ( Huber Group/Hostmann-Steinberg GmbH, D-Celle ( Jänecke+Schneemann Druckfarben GmbH, D-Hannover ( Schmid Rhyner AG Print Finishing, CH-Adliswil ( Sicolor GmbH, D-Neusäss ( SunChemical Hartmann Druckfarben GmbH, D-Frankfurt/M ( Terra Lacke GmbH, D-Lehrte ( Toyo Ink Co. Ltd., J-Tokyo Vegra GmbH, D-Aschau am Inn ( Weilburger Graphics GmbH, D-Gerhardshofen ( Xsys Print Solutions Deutschland GmbH, D-Stuttgart ( Washes Varn Products GmbH, D-Reutlingen ( DC DruckChemie, D-Ammerbuch ( DS Druckerei Service, D-Reutlingen ( Vegra GmbH, D-Aschau am Inn ( Blankets Birkan Drucktechnik GmbH, D-Eching am Ammersee ( Day International GmbH, D-Reutlingen ( Phoenix Xtra Print GmbH, D-Hamburg ( Plates Kodak Polychrome Graphics, D-Osterode ( Rudolf Reproflex GmbH, D-Goslar ( Xsys Print Solutions Deutschland, D-Stuttgart ( Rollers Felix Böttcher GmbH & Co. KG, D-Cologne ( Praxair Surface Technologies, D-Schlüchtern ( Dryers Adphos Eltosch Torsten Schmidt GmbH, D-Norderstedt ( Grafix GmbH Zerstäubungstechnik, D-Stuttgart ( Dr. Hönle AG UV Technology, D-Gräfelfing ( IST Metz GmbH, D-Nürtingen ( RadTech Europe, NL-Den Haag ( Substrates M-real Technical Sales and Marketing, D-Hamburg ( Schneidersöhne Group, D-Ettlingen ( UPM-Kymmene Sales GmbH, D-Hamburg ( Vegra UV coating 1038 for hybrid finishing is exceptionally scuff-resistant, adheres extremely well and can be scored, folded, glued (with water-based adhesives), heatstamped and heat-sealed (PVC and PP) coating. Alternatively, to create a drip-off effect with aqueous coating, apply coating 3606/1 with special coating DL 1188 on hybrid inks. Further information on Vegra products is available at At all events, it is important to ensure that the UV coating is always applied uniformly and in sufficient volume. This should be no less than 5g/m 2, which is equivalent to a pick-up volume by the anilox roller of 15g/m 2. It is essential to clean the anilox roller and check its pick-up volume, using the roller code, prior to impression. All coatings can be worked at maximum production speed. As with aqueous coatings, the temperature of the pile following the UV coating serves as a yardstick for potential problems during folding or scoring. Use in food and non-food packaging printing Examinations of prints hybridcoated with Vegra s high-gloss UV coating 1038 showed no residual monomers or photoinitiators when subjected to an extraction process using alcohol and methylene chloride. On top of this, all Vegra UV coatings are odour-free and certified as such by ISEGA*. So this type of gloss coating can also be used for food packaging, provided the UV lamps are sufficiently powerful to cure the coating properly, and are cleaned and replaced regularly. UV coating 1038 can even be heat-stamped, which also makes it suitable for packaging and labels. Special hotstamping gold foils are available for just this purpose. Albert Uhlemayr, President of the Vegra Group *ISEGA Forschungs- and Untersuchungsgesellschaft ( in Aschaffenburg, Germany, is an independent, globally active consultancy and testing institute for trade and industry, eg manufacturers of pulp, paper, board, folding cartons, synthetics, packaging, inks, coatings and chemical additives; ISEGA issues internationally recognised testimonials and product certificates in accordance with ISO in a number of languages including English, French and German; in 1990 it also started certifying packaging manufacturers hygiene management systems Process

30 Gloss coating gloss Gloss and its measurement using the KBA test chart Gloss is the bright glint that results from holding shiny objects at a particular angle relative to a light source. This gloss angle is equal and opposite to the angle of illumination and is the same as the angle of reflection from a mirror, so gloss light is often called specular light, from the Latin for mirror (or Fresnelian light, after the person who first described the optical laws of specular reflection). A surface with minute variations in its topography reflects the light at many different angles and scatters it. The specular reflection is therefore broader and less directed reflection, the higher the perceived gloss level. One way to reduce scattering is to fill cavities in the surface with a homogeneous medium such as a coating. The level of gloss is the relative light intensity measured at the specular angle with a gloss meter (reflectometer). There are a number of standards for measuring gloss, and these allow measurement from different angles, so the angle must always be stated with the values measured. ISO 2813 prescribes an angle geometry of 20 /20 for high gloss, 60 /60 for medium and 85 /85 for matt the specular reflection at different angles. The values measured at the gloss angle are known variously as reflectometer values, gloss levels, gloss values or degrees of gloss. They vary from 0 (dispersed reflection, zero gloss) to 100 (directed reflection, maximum gloss). The reflectometer values in the table may be taken as a rule of thumb. Application is assumed to be via a flexo unit, except for the oil-based varnish and offline coating. DIN details a less familiar method, visual gloss count, based on a scale from 0 (matt) to 10 (high gloss). The most common US standard, ASTM D 4039, specifies two gloss measurements (60 /60 and 20 /20 ) to obtain a haze index (H = R60 - R20). It is useful for evaluating the haze in clear finishes on non-glossy substrates and in reflected images on opaque glossy pigmented finishes. Gloss is a phenomenon that can be depicted as an indicator (intensity distribution, shown here in yellow) of reflected light Gloss levels delivered by common coating processes UV matt coating on hybrid inks R = UV matt coating on UV inks R = 20 Inks (depending on substrate) R = Oil-based overprint varnish on standard and hybrid inks R = 60 Aqueous coating on standard inks R = 70 Double coating (UV gloss coating on primer) R = UV gloss coating on UV inks R = UV gloss coating on hybrid inks R = Offline UV coating on dry ink R = intense than from a smooth surface. The geometric shape formed above the surface by reflection is known as an optical indicatrix (coloured yellow in the graph) and is specific to that surface. The narrower and longer the indicatrix, ie the higher the proportion of gloss surfaces. For some years the printing and packaging industry favoured 45 /45, but now 60 /60 is also frequently used for measuring coated images. The shape of the indicatrix can be determined using a fixed light source (60 or 45 ) and measuring There is at present no standardised test chart for determining gloss levels. KBA has therefore developed its own test chart with which the degree of gloss can be determined on just about any substrate at different production speeds, regardless of the type of coating and degree of coverage. With this system the press operator can measure gloss on halftone solids using a reflectometer, and check its reproducibility for various different jobs.the two images above were chosen because they feature both light tones and saturated solids, so they provide a good reference for a visual assessment of gloss levels. With double coating the gloss level tends to diminish at the intersection between areas with high and low solids coverage Test results for hybrid coating Gloss measured immediately and after 72 hours MK 70% CM 70% CMY 70% MK 100% CM 100% CMYK 70% CMY 100% CMYK 100% unprinted 140% 140% 210% 200% 200% 280% 300% 400% Measured immediately, 10,000 sph Measured immediately, 12,000 sph Measured after 72 h, 10,000 sph Measured after 72 h, 12,000 sph Using the test chart to determine the gloss levels (y axis) produced by a hybrid coating on images with different degrees of total ink coverage (0 to 400%), at two different printing speeds (12,000 and 10,000sph). Measurements were taken immediately following impression (t+0) and after three days drying time (t+72h).the results were unequivocal: the high gloss achieved with hybrid coating remained more or less constant. The gloss impairment after 72 hours was minimal and prove that there was no draw-back. Printing speed had only a minor impact on gloss (less than 5 gloss points). Even the slight loss at 400% total ink coverage and a press speed of 12,000sph was still acceptable. Conclusion: the UV coating delivered by hybrid printing is not only of an exceptionally high quality but also consistently reproducible. 30 Process

31 Gloss coating Offline When is offline the better choice? As a rule, offline finishing is a service provided by specialist operations, though some folding-carton manufacturers run offline gloss coaters alongside the stamping and die-cutting equipment to which their sheetfed offset presses feed. The technique used coating or film lamination depends on the type of product printed. While gloss levels are generally higher than those possible with inline coating, this alone does not justify the higher cost, so other criteria must be taken into consideration. Coater configurations offered by Billhöfer: 1 three-roller system, 2 two-roller system, 3 double-sided coating with two-roller units, 4 calender Offline or inline finishing? It costs more to finish products offline, ie in one or more dedicated stand-alone devices, than inline, ie during impression. This is why inline coaters have virtually become a routine feature of sheetfed offset presses. Nonetheless, there are some sound reasons for choosing offline gloss coating, eg if: an exceptionally high level of gloss is specified, so calendering or a thicker application of coating is necessary scuff protection and resistance must be improved (eg dust jackets for books) the existing press has no inline coating capability or double-sided coating is specified, so finishing must be outsourced on-demand gloss coating is required too rarely to warrant the expense of having an inline coater running idle for prolonged periods of time offline gloss coating is combined with additional finishing processes such as the application of an adhesive the full sheet format must be coated, which is not possible in the press because of the gripper margin. Although the vast majority of gloss and protective coatings are applied inline, both approaches inline and offline are expanding along with the demand for more sophisticated finishing. Coating The advantage of offline over inline coating is that the ink has already dried, so it does not matter what type of ink has been used. Coating devices can employ various technologies. Dedicated coating devices apply the coating via rollers. The thickness of the coating layer is controlled by adjusting the nip and viscosity. A distinction is made between single- and double-sided and between gripper and gripperfree systems (which can coat a sheet right up to the edge). Sheetfed presses can also be used for offline coating by configuring them as a coating unit with feeder, dryer and delivery (standalone coater) or as a single printing unit functioning as a coater, for which purpose sheetfed gravure and screen printing presses are the most suitable. Alongside water-based and UV coatings, offline coating devices can also apply solvent-based nitrocellulose varnish, but for environmental reasons this is gradually being replaced by other types of coating. Packaging printers commonly use coatings with specific properties, eg cold or steam resistance. And low-cost screen printing machines are often used to apply adhesive coatings on plastic cards. Hot-calender coatings play a major role. They are the only type of coating that can compare with a laminate film when it comes to gloss levels, but without the drawbacks (see section on laminating). When subjected to heat they can be applied in a layer that is twice as thick as other types of coating and then compressed inline by polished calender rollers. Laminating Film lamination is the most complicated method for imparting gloss to an image. As with coatings, there is a choice of gloss and matt laminates, but in addition to this it is possible to apply film with a textured surface, eg to imitate cloth for hardcover books, and with special functional layers, for extreme scuff resistance, say. The most popular material for film lamination is oriented polypropylene (OPP), which is exceptionally tear-resistant, structurally stable and suitable for thermal applications. Acetate film is occasionally used if prints are to be stamped or partially glued. Polyester (PET) is a frequent choice for book covers and encapsulation. Though more expensive, propylene or nylon films are better for book covers because they have the virtue of being thinner and of lying flat, so they allow the paper or board to adjust to humidity changes with significantly less curling. As with offline coating, the type of ink used prior to laminating is immaterial. But laminating does have certain drawbacks. It is much more costly than coating, the coated products cannot be recycled as easily, the film may not be as durable as a coating, and a laminate is generally thicker than a coating. This may, of course, translate into an advantage for outside applications (displays, hoardings, stadium advertising etc) because it makes the products more weather-proof. There is a choice of three laminating processes: water-based lamination with the glue applied cold (with or without solvent); hot-melt lamination using hot glue; and thermal lamination, a relatively new process using film with pre-applied heat-reactive glue. Thermal lamination is now widely used because no solvent is involved, job changes on the laminator are quicker, high laminating speeds are possible, the laminating quality can be more easily reproduced and the products can be recycled more easily. Dieter Kleeberg Process

32 Gloss coating Inline Inline coating systems In sheetfed offset, coating is the only means of imparting a gloss to the sheets inline.there is a choice of inline coating processes to suit the type of inks used and press configuration. Hybrid presses can apply three different types of coating in two modes of operation, so in this respect they are more flexible that two-coater presses. These, however, can apply a UV coating to conventional inks. Inline coating on hybrid inks was one of the topics examined at the second KBA hybrid user meeting in April Coating with and without a coater and in perfecting mode In Choosing the right coating method, on page 10, the benefits of hybrid technology are compared with those of pure UV printing and double coating, and the table showing the various permutations of ink, coating and substrate possible also indicates the relevant press configurations. Continuing on from this, the table below lists the options for the three basic systems with no coater, one coater or two coaters configured after the final printing unit. A water-based coating can even be applied in presses with no coater at all, using either the dampener or the inking unit. But the quality delivered by the dampening-duct coating option previously offered by KBA and other manufacturers is not up to today s standards, so there is very little demand for it among printers. And applying an aqueous coating in the inking unit, possibly with the aid of the slipin doctor-blade recommended by some of KBA s competitors as an entry-level solution, has also proved to be problematical: if there is no downstream IR or thermal air dryer, or if the IR dryer is only powerful enough to dry ink, this limits the volume of coating that can be applied. More sophisticated configurations include presses that can even coat both sides of the sheet, ie they apply a gloss or protective coating prior to perfecting. Depending on the type of coating they must also incorporate a preperfecting dryer in the form of plug-in modules or, preferably, full-scale dryers. KBA has already installed several Rapida 105 universal and new-generation Rapida 105 presses with this configura- Inline coating sheetfed offset options No. of coaters Type of coating (area) Ink type Coating application Comments None OPV (solid, spot) Oxidative/penetrative Wet-on-wet in printing unit with imaged plate and blanket None Aqueous (solid) Oxidative/penetrative Wet-on-wet in printing unit with uncoated aluminium plate and blanket None Dampening duct (solid) Oxidative/penetrative Wet-on-wet in dampener with uncoated aluminium plate and blanket Maximum gloss level 60 Thin coating film, slightly thicker with slip-in doctor blade (not offered by KBA, as problematical without IR/thermal air dryer) Thin film of low-concentration aqueous coating; Varidamp coating no longer in demand One Aqueous* (solid, spot) Oxidative/penetrative or hybrid Wet-on-wet in coater Flexo coater and delivery extension with IR/thermal air drying; also in conventional mode on hybrid presses; max. gloss 70 One UV (solid**) UV On cured inks in coater Interdeck UV curing, UV-resistant materials, flexo coater and double delivery extension with final UV curing; max. gloss 90 One UV (solid**) Hybrid (oxidative/penetrative + UV) On cured inks in coater Flexo coater and double delivery extension with IR/UV dryer for hybrid mode on hybrid presses; max. gloss 95 One OPV (spot) + UV (solid**) Hybrid (oxidative/penetrative + UV) OPV wet-on-wet in final printing unit, UV on dried OPV in coater Flexo coater and double delivery extension with IR/UV dryer for hybrid mode on hybrid presses; max. gloss 95, optimum gloss contrasts One OPV (spot) + drip-off/twin-effect aqueous (solid) Oxidative/penetrative or hybrid OPV wet-on-wet in final printing unit, aqueous in coater Flexo coater and delivery extension with IR/thermal dryers; possible warming of aqueous coating; average gloss contrasts Two Aqueous coating* (spot, solid) + aqueous coating* (solid**) Oxidative/penetrative Wet-on-wet in 1st coater, on dried coating in 2nd coater Two flexo coaters with dual IR/thermal interdeck dryers, double delivery extension, end-of-press IR/thermal dryers; max. gloss 80, interesting effects Two Aqueous coating as primer (solid**) + UV (solid**) Oxidative/penetrative Primer wet-on-wet in 1st coater, UV on dried primer in 2nd coater Two coaters with end-of-press UV coating; max. gloss 85 Two Metallic effect coating (solid) + UV UV or special-effect aqueous coating (solid) Metallic effect coating on cured inks in 1st coater, second coating on dried metallic effect coating in 2nd coater Interdeck UV coating, UV-resistant materials, two coaters with final IR/thermal dryers; interesting effects *also with special-effect pigments **with possible exclusion of areas to be glued Colour codes: white = oxidative/penetrative inks, green = hybrid inks, violet = UV inks; yellow = OPV, blue = aqueous coating, grey = aqueous coating with special-effect pigments, mauve = UV coating; red = IR/thermal air dryer 32 Process

33 Gloss coating Inline tion. Off-spec presses sometimes feature a coater before the first printing unit, eg for applying an aqueous opaque white or specialeffect primer (MetalFX metallic, iridescent). Aqueous coating Aqueous coatings are the most popular choice for inline application in sheetfed offset. They can take the form of a gloss, matt or protective coating. Thanks to the doctoring systems that are now a standard feature they can also incorporate special-effect pigments. To dry them properly the coater must incorporate infrared lamps plus a thermal air wand to expel moisture (see chapter on KBA VariDry, pp 6-9). Applying aqueous gloss coatings wet-on-wet will inevitably cause a loss of gloss, because some of the coating is sure to penetrate the ink. However, the draw-back is not on the same scale as when a UV coating is applied directly to conventional inks or to primer before it is sufficiently dry. With a hybrid press it is possible to apply an aqueous coating to conventional inks. While this would also function with hybrid inks, the gloss level with a UV gloss coating is very much better. UV coating Unlike aqueous coatings, which must be dried immediately, a UV gloss coating needs time to spread and form the smooth surface necessary for a high gloss. While both systems require a Separate circulation systems for faster coating changes The ability to switch at speed from one mode of operation to another on hybrid presses demands an equally fast and cost-effective change of coating.the standard configuration for a Rapida hybrid press includes two separate pumping circuits for the coater, so that during makeready for a new job the coating can be changed by simply switching to the other circuit. Optional equipment includes an automatic cleaning and pumping system for aqueous and UV coatings.with this, conversion from UV to aqueous coating or vice versa takes just seven to ten minutes, and from UV to UV or aqueous to aqueous just one to two minutes. Schematic of Harris & Bruno s LithoCoat automatic coating feed system. UV or aqueous coating is pumped out of containers 1 or 2 to the coating conditioning unit and on to the doctoring chamber delivery extension, with an aqueous coating system this is used to house powerful IR and thermal air dryers, whereas with a UV coating system it extends the distance to the end-of-press dryer and thus the length of time in which the coating can spread. For presses with an output of up to 18,000sph it is even advisable to install a double delivery extension. Because the UV coating is never applied wet-on-wet, but always on a layer of ink or aqueous coating that has already been dried, it can scarcely penetrate underlying layers. This is another reason why, in principle, higher gloss levels can be created than with an aqueous coating. The absorbency of the substrate only plays a role in the extent to which the ink has formed a smooth or (through penetration) roughened surface. UV coatings differ according to the applications for which they are formulated. The key properties of UV coatings for pure UV applications, for instance, are higher gloss and slippage. In twin-coater presses the UV coating is also optimised for adhesion The longest Rapida 105 hybrid press to date is a 5/5 perfector with perfect coating.the five recto units, which can apply conventional or hybrid inks, are followed by a coater for aqueous or UV coating, two thermal/uv interdeck dryers, five verso units, a third coater, a double delivery extension with IR and thermal air dryers and a final UV dryer immediately prior to sheet delivery. Additional UV lamps can be plugged in as interdeck dryers before and after perfecting. Potential markets for products featuring a two-sided gold, silver, gloss or matt coating in addition to a normal aqueous or UV coating include the cosmetics, fashion and automotive industries L30 Combi Circulator (left) and X10 Conditioner two components in Tresu s automated dual-circuit pumping system to the aqueous primer. UV coatings for hybrid production are formulated for optimum adhesion on hybrid inks or repulsion on OPV to create spots. Although hybrid presses incorporate interdeck UV curing for the inks and the high-gloss UV coating, the press operator requires no particular experience with UV production. This makes hybrid presses the ideal entry-level system for the adoption of UV technology because the operator can use the tonal transfer characteristics of conventional presses he can rely on a more stable production performance than in pure UV printing, especially where the ink/water balance is concerned he can switch easily between conventional and hybrid production, and between aqueous coating and OPV plus UV coating, because there is no need for UV-resistant components in the printing units. Process

34 Gloss coating Inline Current state of the art in doctor-blade technology Modern flexo coating systems allow large volumes of coating to be applied and thus outstanding gloss levels to be achieved.the role of earlier two-roller coating units, to enable the volume of coating applied to be varied with comparative ease, has become superfluous because the coating film must usually have a uniform thickness. And if the volume of coating does need to be changed, this can be done by using an anilox roller with a different pick-up volume or specification, eg for pearl gloss pigments. KBA s anilox technology is particularly user-friendly: the lightweight design of the rollers means that even in B1 or B2 presses they can be exchanged manually, without the need for a lifting aid. As already mentioned in the chapter on the adhesion and compatibility of inks and coatings (pp 11-13), the anilox rollers used in flexo coaters today have an open structure and a finer screen.the finer the screen, the more efficiently coating spreads and the finer the spot textures that can be achieved. The previously continuous cell walls have been reduced to mere pyramid-shaped stumps at the intersections. This new engraving pattern, known as anilox reverse technology (ART) makes the surface much easier to clean and enables the anilox roller to achieve a gloss 3 to 5 points higher than before, because the coating is less prone to form an orange-peel skin or pinholes. ART engraving combined with a thin ink film (TIF) enhances the spreading properties of the UV coating despite the thinner film. The cross-hatched spiral formerly preferred has fallen out of favour because it draws the coating from one side of the press to another. Advances have also been made in the design of the doctor blade. Until now, one critical issue was the rapid abrasion of the two steel blades. Replacing them with ceramic blades, and using ceramic for the anilox roller coating, has increased the service life by a factor of 8. Ceramic reverse-angle and doctoring blades following eleven weeks of production at 8,000sph (Photos: Praxair) The rotation of the anilox roller causes different levels of abrasion on the two doctoring blades, illustrated here on two BTG ceramic blades after a week s use Cleaning processes for anilox rollers Process, aids Automatic washing unit integrated in coating feed system Cleaning mat Steel brush Ultrasound Blasting with - sodium bicarbonate - carbon dioxide (dry ice) - plastic pellets IR laser Double coating Despite the higher energy input for drying and the bigger footprint compared to a hybrid press, there are some sound reasons for configuring a press with two coaters, and this option will remain in KBA s product range. Two-coater presses allow: auv coating to be applied to conventional inks, though only indirectly following inline sealing of the ink film with a layer of aqueous coating awide range of imaginative effects to be created by applying different types of aqueous coating. The aqueous coating (primer) applied prior to the UV coating does more than ensure that the UV coating adheres properly. The mere fact that the primer is dried and substrate absorbency thus reduced before the UV coating is applied, enhances the overall level of gloss obtained. On top of this the stabilising effect of the primer improves any subsequent lamination. To avoid problems when working with two different types of coating it is essential to source them from the same manufacturer and make sure that they are mutually compatible. The versatility of the two-coater configuration lies in its ability to apply not only an aqueous primer and UV coating but also two aqueous coatings, either identical ones or different ones. Even without a final UV coating the application of two aqueous gloss coatings can create high gloss levels. Still more interesting is the fact that some very attractive effects can be achieved if one of the two aqueous coatings contains metallic or Comments Time-variable washing programs for all coating components; virtually no manual cleaning; very fast Used in place of or on coating blanket, has a fulling effect; recommended by Praxair Highly effective if rollers are cleaned immediately after impression; a wash for aqueous and/or UV coating (if possible, biologically decomposable) is applied and massaged in with a circular motion; the rollers are then dried with a lint-free cloth; copper or brass brushes are not suitable because they react with the ceramic; aggressive agents can cause roller corrosion Roller must be removed; improper usage can damage ceramic; relatively expensive Roller must be removed; improper usage can damage ceramic; relatively expensive Recommended for an anilox roller screen of 300lpc or finer; roller must be removed; improper usage can damage ceramic; relatively expensive pearlescent pigments, or simply just a tint, offering tremendous scope for creativity. Gloss contrast coating Contrasting gloss effects can be created in three different ways, variously described as drip-off coating, twin-effect coating and hybrid coating. A feature common to all of them is spot coating with a matt or texture-building OPV in the last printing unit followed by a full-solid high-gloss coating, which because of its high interfacial tension does not adhere but forms beads on the sheet surface and runs or drips off. The differences lie in the type of gloss coating: drip-off coating is aqueous and heat-sensitive, twineffect coating is standard aqueous and hybrid coating is UV. Twin-effect systems are also available for hybrid inks. The biggest difference lies in the quality of the gloss contrast that can be achieved: a combination of hybrid inks, OPV and UV coating is unbeatable and far superior to the gloss contrast obtainable with the two other processes. 34 Process

35 Gloss coating Inline This, along with the ability to switch between different operating modes, is the second major reason why printing with a hybrid press may be the best solution in many instances. UV coating on special hybrid inks The fact that only a few of the hybrid inks currently on the market have been tested by Fogra and approved by KBA for use in Rapida presses does not mean that the rest are unsuitable. The same applies to special inks. The risk of using untested inks is lowest where the ink manufacturer has already received hybrid accreditation for CMYK inks. Pantone Matching System (PMS) inks and a few metallic-effect inks are also available for hybrid applications, so in this respect there is no cause for reservations with regard to hybrid production. When a UV gloss coating is applied to special inks it can result in draw-back if the inks have not been cured sufficiently in the interdeck dryer. Since some of the colours in a PMS scale look very strong, a lot of printers tend to overink to try and achieve the same intensity. As a result the film of ink is simply too thick to be cured properly by just one UV lamp, so it is advisable to install a second interdeck UV dryer for PMS inks. Even with an achromatic CMYK separation the black is often overinked, which is why in such cases the efficiency of the interdeck UV curing should also be checked. Too thick a film can also cause problems during trimming, scoring and stamping. It would be a help if ink manufacturers could, in future, increase the concentration of pigments in their special inks, because a stronger colour would reduce the thickness of the film. However, ink manufacturers point out that there is limited scope for such intervention in the formulation of hybrid inks. Hybrid inks with metallic pigments are already available in various shades of bronze, silver and gold. Gold is the only colour that causes printability problems for some users. It is impossible to say whether the UV coating chosen will impair the metallic gloss effect of the relevant metallic ink. Good results have been obtained by preprinting with MetalFX silver base ink from Sun Chemical or Huber prior to applying hybrid or UV CMYK inks followed by a final UV gloss coating. If the black ink film is thinner, the UV coating enhances the KBA s calendar for 2005, Michael Freudenberg: Abstract Landscapes is a fine example of the extraordinary quality now possible when creating gloss contrasts with hybrid coating.the artist s signature, the calendar dates and the KBA logo have a high-gloss finish, while the black imitation passe-partout has a granular texture. To complete the stunning effect, the brush strokes in each of the pictures reproduced are emphasised with a fine-grained gloss. The calendar was printed using Epple s Starbrite hybrid inks and overprint varnish plus Weilburger Graphics Senolith UV/hybrid effect coating on 170gsm GardaMatt supplied by Cartiere del Garda gloss of the metallic components. Nonetheless, it would not hurt to run a test print, since inadequate drying can cause the ink and coating to crack when the sheets are trimmed. Coating needs planning If you are planning to include coating in your production schedule, there are a number of factors you should consider: preparing spot coating formes prolongs makeready asimple aqueous coating may enable the sheets to be finished sooner sheets that have been UVcoated on both sides should be trimmed while the pile is still warm, to eliminate the risk of blocking (glass-plate effect) coating requires a higher overcount when scheduling offline coating it is advisable to consult your finishing provider with regard to press availability, gripper margin and interim storage prior to additional finishing processes (eg embossing). Dieter Kleeberg Rapida 105 dual coater press comprising a coater, two interdeck dryers and a second coater plus a double delivery extension Hybrid inks with no coating? At the most recent hybrid user meeting the question was raised as to whether hybrid inks can be used without any coating. Apart from the fact that replacing relatively cheap conventional inks with more costly hybrid inks makes little economic sense, there are technological reasons for not doing so. Hybrid inks are formulated to accept a coating: they therefore have no inherent gloss, so are much duller than conventional inks, and must contain no waxes or silicones, so they also lack any scuff protection and would be vulnerable to scratching on the recto side during verso printing. Process

36 Hybrid technology Retrospect KBA achieves breakthrough with hybrid technology KBA s sheetfed offset specialists have been busy optimising the performance of hybrid printing inks since the end of the 1990s. It is largely thanks to this dedication that press technology, printing inks, coatings, washes and blankets for hybrid applications have attained their current standard of perfection. KBA was quick to recognise the potential that hybrid offers and instead of questioning its feasibility, like other press manufacturers, invested heavily in developing and optimising the technology in close collaboration with ink, coating and dryer manufacturers.today KBA leads the field, with an installed base of 250- plus Rapida press lines that enable users to reap the benefits of its patented hybrid technology and the new coating effects now possible, while maintaining the ability to switch to conventional operation at the touch of a button. Initial uncertainty The accidental discovery of the hybrid principle by a Grafix technician in the early 1990s led to the development of dedicated inks capable of drying by UV radiation as well as by oxidation and penetration. But it was soon found that formulating such inks was no easy matter merely mixing standard inks with UV inks was not the answer. And it is an unfortunate fact that, even today, not every ink labelled hybrid deserves the name. Washes, too, must be specially formulated. Disregarding the basic principles gave rise to problems, complaints and even damage to the press. KBA has responded by having a range of consumables tested for hybrid compatibility and approving only those that pass the test. As a result there has been an abrupt decline in the number of naysayers and sceptics who seize on every issue as evidence of hybrid s inherent inadequacy. KBA sets milestones Despite the flak, KBA s sheetfed offset specialists in Radebeul continued to pursue their objective with single-minded determination, and in November 2000 registered a number of patents for hybrid coating. Since then KBA has defined its hybrid technology in terms of the configurations, consumables and peripherals recommended for use in its Rapida presses. The list of consumables recommended for use with KBA s standard hybrid package is updated on an ongoing basis to reflect the current state of the art. KBA delivered the first press with a hybrid capability on 11 May This was a Rapida 162a sixcolour perfector with coater for The first demonstrations of hybrid coating at a trade fair took place on this Rapida 105 twocoater press at Drupa By applying a UV coating in both coaters, but otherwise making no changes whatsoever to press equipment, KBA proved that hybrid inks can run on conventional presses Unimac Graphics in the USA. It was followed at the end of July the same year by the first hybrid Rapida 105 universal, a five-colour version of which was shipped to Montligeon in France. In December 2002, hybrid coating moved into B2 with the delivery of a Rapida 74 five-colour coater to La Moderna Stampa in Italy. The first user of a new-generation Rapida 105 hybrid press was Challenge Printing in the USA, which took delivery in September In November 2005 the world s first superlarge hybrid Results of emission tests conducted on a Rapida 105 two-coater hybrid press at Drupa 2000 Source of emission Threshold value Test result VOCs (volatile organic compounds): isopropyl alcohol hydrocarbons 500 mg/m 3 substantially lower 500 mg/m 3 substantially lower Ink mist under discussion untraceable Ozone 0.2 mg/m 3 substantially lower UV radiation as per pren substantially lower Powder 6 mg/m 3 (1.5 mg/m 3 under discussion) substantially lower Noise 84 db (A) lower Albrecht Bolza-Schünemann, at that time deputy president of KBA, affixing the BG s emission tested seal of approval on a hybrid Rapida 105 at Drupa Process

37 Hybrid technology Retrospect At Mayr-Melnhof s 9th symposium on carton in 2004 KBA demonstrated the use of hybrid coating for brand protection press, a Rapida 205 six-colour with coater and dryer, shipped to another US printer, Philipp Lithographing. KBA, not unnaturally, platformed its achievements at Drupa 2000, which thus became the first trade fair at which print professionals could witness live demonstrations of hybrid coating. The press concerned was a Rapida 105 twocoater press, which applied a fullsolid final UV coating with no prior application of primer in the first coater and a high-gloss UV spot coating in the second. This was compelling proof that hybrid coating is perfectly possible with conventional printing units. That particular Rapida 105 was also the first sheetfed offset press worldwide to be awarded the internationally recognised emission tested environmental seal of approval issued by the Berufsgenossenschaft Druck und Papierverarbeitung, the German health and safety executive. At Drupa 2004 KBA and its alliance partners unveiled the latest advances in hybrid coating. Packaging printers were quick to pick up on the new low-odour hybrid inks which opened up whole new fields of application. Alternate conventional and hybrid production was demonstrated on a new-generation 18,000sph Rapida 105, which in 2005 was also awarded an emission tested seal of approval. That same year the first VariDry systems (see pages 6-9) were installed in Rapida 105s and thus also in hybrid presses. This bespoke dryer technology is another decisive advance in perfecting the hybrid process. KBA also started accrediting the hybrid printing inks tested by Fogra for performance and hybrid compliance when used in conjunction with other consumables and aids. Accreditation is a neverending process and should eventually become established as the standard testing procedure. It is a major contribution by KBA towards enhancing the reliability of hybrid production and thus of hybrid applications. KBA promotes exchange of views In September 2003 KBA organised a hybrid user meeting which, for the first time, furnished a platform for exchanging views and comparing notes. More than 150 users and producers of consumables attended the event, at which KBA and other prominent suppliers reaffirmed their commitment to supporting users by continuing to drive Countering scepticism Back in 1999, when KBA started shipping hybrid presses with conventional inking rollers (as opposed to rollers specially engineered for hybrid or UV production) and not only dispensed with a dedicated UV capability in the printing units but also implemented low-alcohol production, other manufacturers pursued a different approach. Here the issue is not the early mover advantage that KBA enjoyed, which is documented in a string of patents and installations, but the widespread scepticism the group had to overcome. In 2001 a major competitor published the results of print tests run on an eight-colour press printing cartonboard using pure UV, double coating and hybrid coating. The testers came to the conclusion that on cost-efficiency and the range of applications possible, double coating production scored over hybrid, which was more problematical (these findings stood in crass contrast to a cost-efficiency analysis presented by KBA marketing director Klaus Schmidt at an open house on environmental printing processes in October the same year). The testers claimed that there was a higher risk of ink emulsification in hybrid operation, and that additional interdeck UV dryers were required when printing full solids.the fact that the printing units were harder to clean than UV units, and required manual cleaning and intermediate wiping, indicates that unsuitable consumables were used. The testers also claimed that a larger volume of ink had to be applied than in conventional print production in order to achieve the same density in the print. They therefore calculated that alongside higher costs for washes, ink consumption would also be higher.they recommended fitting UV-resistant coatings on the inking rollers and using UV blankets to avoid problems with hybrid inks. If the hybrid component in the ink was less than 10% then conventional rollers could be used. Since then competitors have largely come round to KBA s standpoint concerning hybrid technology. Nonetheless, a technology brochure issued at Drupa 2004 still expressed reservations: And since all the hybrid inks examined by [ ] contain a high proportion of photoinitiators, UV-resistant consumables must be used in the printing units and the delivery. In general we recommend the use of dedicated hybrid inking and dampening rollers.the minimalist solution advocated by certain competitors and manufacturers of dryers and inks limits the versatility of the press, while unsuitable components and materials can impact negatively on maintenance costs and the resale value of the press. Process

38 Hybrid technology Retrospect The inks and other consumables recommended by KBA and its alliance partners make the hybrid process exceptionally stable, as countless examples from the press room have proven. Problemfree, quality hybrid printing is then possible with conventional printing units. A typical hybrid configuration comprises a five-colour sheetfed offset press with a coater, an interdeck UV dryer, a double delivery extension housing infrared and thermal air dryers, and an end-of-press UV dryer. Depending on the application it may be advisable to add a second interdeck UV dryer. The press shown here, a new-generation 18,000sph Rapida 105 in the customer showroom at KBA s plant in Radebeul, has a sixth printing unit so that it can print six-colour scales (eg Hexachrome) or apply a special colour prior to overprint varnishing. The price for a hybrid B1 (40in) press is approximately 20% lower than for a two-coater press. Energy and machine overheads are also much lower, and on top of this a hybrid press is much more versatile. KBA can supply hybrid versions of any of its Rapida presses from the B2 (29in) Rapida 74 to the superlarge (80in) Rapida 205 advances in this relative new technology. Hybrid s enormous potential for expanding the range of coatings and applications possible is far from exhausted and demands an intensive dialogue between developers and users. KBA sees itself as a market-driven innovator and co-ordinator, and this role is universally acknowledged in professional circles. The response to the second KBA hybrid user meeting in April 2005 was even greater, with 280 participants from 12 countries. The meeting furnished a lot of the figures quoted in this publication, and revealed just how far hybrid technology has advanced in such a few years. Print jobs that would not have been possible without hybrid production confirm the wisdom of investing in this technology. Despite a few issues that have arisen as users have taken on more challenging jobs and acquired a taste for experimentation, there is general satisfaction with the support provided by KBA and consumables suppliers. KBA has used other events as a platform for promoting hybrid technology and has met with a huge response among printers eager for further information. KBA hybrid users first publicly discussed their reasons for adopting hybrid and their experience to date at a print forum in And at the 9th symposium organised by Mayr-Melnhof Karton (MMK) at KBA in 2004, where the focus was on possible coating applications for brand protection, a hybrid Rapida 105 compellingly demonstrated its suitability for this type of work as well. Jürgen Veil, head of KBA sheetfed offset marketing, unveiled an economical method he and his team have developed for creating a 100% forgery-proof hidden image by exploiting the contrasts possible with different transparent coatings on unscreened solids. Hybrid winning hearts and minds Worldwide shipments of hybrid presses by KBA alone for all the current formats have topped the 200 mark, not counting a string of presses that KBA Radebeul has modified for hybrid production. And sales of hybrid presses have increased every year since the process was launched a success that has vindicated KBA on all counts. After repeatedly calling into question the whole concept of hybrid production, previously vociferous opponents in the consumables industry have now jumped on the KBA bandwagon and are issuing information in the trade press about various installations. This is because the proven cost-efficiency and simple handling of hybrid presses have made it difficult, in the long run, to muster a compelling argument against them, even though they may impact on sales of coaters. Dieter Kleeberg Regular demonstrations of hybrid technology, like this one for a group of Italian print professionals, are held in KBA s Radebeul showroom 38 Process

39 Hybrid technology Accreditation Fogra tests hybrid inks In 2004 KBA asked Fogra, the Munich-based testing institute, to examine six different series of hybrid inks. Around 600 individual tests were conducted to find out whether and to what extent the inks a) caused rubber roller coatings and blankets to swell, and b) were washable. The object was to determine which inks were suitable for hybrid print production and to issue a seal of approval ( accredited for hybrid printing ) to indicate this. The Fogra/KBA seal confirms that an ink is recommended for hybrid print production, but only in conjunction with the rubber rollers, blankets and washes utilised in the tests. In the course of the tests Fogra also came up with some new proposals for approving other products with a view to enhancing process reliability and safety. Testing and standardising to enhance compatibility The reason KBA requested the tests was that some consumables currently designated as hybridcompatible and used in hybrid Rapida presses have proved to be almost pure UV consumables. The result has been damage to rollers and blankets and a loss of confidence by users not just in the consumables available but in the innovative hybrid process itself. Having consumables tested for hybrid compatibility by a highly respected institute like Fogra establishes clearly defined standards for product approval. The aim is not to oblige manufacturers to disclose their formulae but to ensure that the properties of consumables designated as hybrid compatible really do function as labelled, ie promote the requisite standard of quality in hybrid printing and coating along with a trouble-free press operation. To test for roller swell, 36 x 6mm (1 1 /2 x 1 /4in) samples of rubber compound were immersed for seven days in hybrid ink at a constant temperature of 40 C (104 F) KBA asked Fogra to examine six different brands of hybrid ink (CMYK Euroscale) supplied by six (now five) manufacturers: Series A: K+E Novabryte BF Process from Xsys Print Solutions (formerly BASF), Series B: Sun Cure Hy-Bryte from Sun Chemical, Series C: Starbrite from Epple, Series D: Reflecta Hybrid from Hostmann-Steinberg (Huber Group), Series E: EXC Process Hybrid from Arets Graphics, Series F: Gemini Process from Xsys Print Solutions (formerly Flint-Schmidt). Impact of hybrid inks on roller swell For the DIN test regime German roller manufacturer Felix Böttcher in Cologne provided samples of the three rubber compounds used in its inking and dampening rollers: M1: for ink forme rollers, M2: for ink vibrators, M3: for dampener forme rollers. The samples were immersed in hybrid inks at a temperature of 40 C (104 F) for seven days and changes in volume (%), mass (%) and hardness (Shore A) subsequently noted. Fogra recommends raising the temperature to 50 C (122 F) so as to align the results with roller manufacturers standard tests. Since changes in volume and mass do not necessarily result in a corresponding and proportionate loss of hardness, the approval procedure must include tests for this as well. Inks C and F caused the least swelling, while E failed the test because it caused substantial changes in volume and mass. The impact of D on the hardness of compound 2 was critical. Impact of hybrid inks on blanket swell Here, samples of six blankets for the DIN test regime were provided by three different manufacturers: 1: ContiAir/Phoenix Xtra Print s Topaz Carat (for conventional, hybrid and UV inks), 2: ContiAir/Phoenix Xtra Print s Tourmaline (for conventional inks), 3: ContiAir/Phoenix Xtra Print s Ruby Carat (for hybrid and UV inks), 4: Day International s Equalizer 3610 (for conventional and hybrid inks), 5: Day International s NSP 03 (for conventional, hybrid and UV inks), 6: Duco/Birkan s Multi Hybrid (for conventional, hybrid and UV inks). During the tests only the surface of the blankets was exposed to the ink. As with the rollers, the ink was left to react for seven days, also at a temperature of 40 C, but changes in thickness and mass were then measured in absolute terms. As expected, the changes were similar to those in the roller compounds. Blanket 3, which was primarily developed for UV production and features a top layer of EPDM (ethylene propylene diene monomer), was impervious to all types of ink. Inks C and F caused conspicuously little swelling in all blankets. Inks A, B, D and, most noticeably, E caused all the other types of blanket to swell. The threshold values for changes in thickness (±0.04mm) and changes in mass (±100g/m 2 or ±0.0707g/surface area tested), which are the same as for the wash tests, seem excessive, which is why Fogra recommends that blanket manufacturers adopt more sensible limits for the impact of ink. Standardised device for determining changes in thickness, in this instance of a blanket Process

40 Hybrid technology Accreditation Impact of washes on hybrid inks Five washes Day International s Hybrid-Wash, DC Druck Chemie s Hybrid 1.0 and 3.0, DS Druckerei Service s Novasol HB 10 (Fuji Hunt) and Vegra s E939, plus a sample formula were tested for their efficacy with hybrid inks. All washes are based on vegetable oils, which have a high boiling-point and are less aggressive than UV washes. The samples prints on paper strips before and after washing 0.17g of ground ink with 0.3ml of wash were obtained using a special test printer provided by Prüfbau. The prints were cured under a UV lamp and subsequently measured with a densitometer. The washability of hybrid inks was therefore assessed according to the reduction (in %) in optical thickness of the ink film. Inks B and C were harder to wash off than A, D, E and F. Yellow ink generally washed off less easily than the other colours. A wash that effectively removes one series of inks may be ineffective with another. For example, W5 cleaned off inks A and E fairly efficiently, but failed the test with B and C. The sample formula performed well in every test and is therefore recommended as a reference wash for future tests. Accreditation and future testing criteria Of the six different makes of CMYK inks tested, only four were given the seal of approval: Series A: Xsys Print Solutions K+E Novabryte BF Process, Series B: Sun Chemical s Sun Cure Hy-Bryte, Series C: Epple s Starbrite, Series F: Xsys Print Solutions Gemini Process. If the composition of an accredited product is changed, Fogra must be notified without delay and the product resubmitted. The inks that failed the tests will be modified and resubmitted, with series D standing a good chance of approval, but not series E because of its UV-typical properties. Since the first batch of tests was limited to a random selection of six different series of inks, it does not necessarily follow that all non-accredited inks are unsuitable. For example, Toyo Ink s FD HB Eco-SOY series gave some excellent results when it was used for print demonstrations at a hybrid user meeting in April The same applies to blankets, rollers and washes. However, anyone using products other than those listed above does so at their own risk, so it would be wise to seek advice on the choice of process components. In future any manufacturer can, for a fee, volunteer to have Fogra test its products for approval, without being referred by KBA. Shortly before this edition of Process went to press, two more inks Jänecke+Schneemann s Supra UV Hybrid and Sicolor s Sicobrite passed the Fogra accreditation test. The washability of the six hybrid inks was tested using six different hybrid washes and a special test printer provided by Prüfbau Propensity of rubber compounds to swell: change in volume (in %) of three different rollers following seven-day contact with hybrid inks A to F (threshold value: ±4%) Black M1 M2 M3 A B C D E F Yellow M2 M1 M3 A B C D E F Magenta M1 A B C D E F Cyan M2 M1 M3 A B C D E F M2 M3 40 Process

41 Hybrid technology Accreditation Proposals for test criteria The report we submitted on the tests included some proposals for future test criteria. One is that laboratory tests could be used to reveal potential weaknesses in rubber compounds, since some of the swelling indicates that there is a very real risk of damage during continuous exposure. We also recommend that the washability of inks submitted for approval should be tested with a standard wash formula (which Fogra would develop) and that a minimum degree of washability should be prescribed using the method mentioned above. New washes could be tested for approval in the same way, provided they exceed the minimum degree of washability with standard inks. Although the cleaning tests confirmed pressroom find- Propensity of rubber compounds to swell: change in mass (in %) of three different rollers following seven-day contact with hybrid inks A to F (threshold value: ±4%) Black M1 M2 M3 A B C D E F Yellow M2 M1 M3 A B C D E F Magenta M1 A B C D E F Cyan M2 M1 M3 A B C D E F M2 M3 Propensity of rubber compounds to swell: change in hardness (in Shore A) of three different rollers following seven-day contact with hybrid inks A to F (threshold value: ±5 Sh.A) 0 A B C D E F 0 A B C D E F M3 M1 M2 Black A B C D E F M3 M M3 M1 M2 Magenta A B C D E F M1 M M Yellow -5-6 Cyan M2 Process

42 Hybrid technology Accreditation ings, in that they revealed some substantial differences both in the washability of individual inks and the efficacy of individual washes, they did indicate that washing problems depend largely on the combination of other consumables used. Washability is a crucial factor in standardising print production with hybrid inks because washing times have an enormous impact on productivity. Washability tests could lead to shorter washing cycles and thus enhanced cost-efficiency. At the same time they would enable the printing process to be standardised more efficiently. At present washes must be classified according to their efficacy with specific hybrid inks. Dr.Wolfgang Rauh, fogra Alexander Schiller, fogra Propensity of rubber compounds to swell: change in thickness (in mm) of six different blankets following seven-day contact with hybrid inks A to F (threshold value: ±0.04 mm) Black Magenta A B C D E F A B C D E F 0.10 Yellow 0.10 Cyan A B C D E F A B C D E F Propensity of rubber compounds to swell: change in mass (in g) of six different blankets following seven-day contact with hybrid inks A to F (threshold value: ±0.0707g/surface area tested) Black Magenta A B C D E F A B C D E F Yellow 0.10 Cyan A B C D E F A B C D E F 42 Process

43 Hybrid technology Accreditation Product No.:. Accredited For Hybrid Printing At a hybrid user meeting in April 2005, Jürgen Veil (right), head of KBA sheetfed offset marketing, awarded the first KBA/Fogra certificates of accreditation to manufacturers of hybrid inks represented by (from left) Joachim Erlach (Epple), Gerrit Wemken (Sun Chemical Hartmann) and Harold Terwal (Flint-Schmidt/Xsys Printing Solutions) The KBA/Fogra seal of approval includes a space for the product name and number By the time this edition of Process went to press a total of six hybrid inks had passed the KBA/Fogra accreditation tests (see table on page 21). A Fogra test certificate is indispensable for KBA accreditation Efficiency (in %) of six different washes (W1 to W6) on black, magenta, yellow and cyan hybrid inks A to F (ideal: 100%; acceptable minimum: 50%) A W1 W2 W3 W4 W5 W6 C K M Y C C K M Y W1 W2 W3 W4 W5 W B M Y C K W1 W2 W3 W4 W5 W6 D K M C Y W1 W2 W3 W4 W5 W E W1 W2 W3 W4 W5 W6 K C M Y F M C K Y W1 W2 W3 W4 W5 W6 Process

44 Hybrid technology Cost-efficiency Comparative cost analysis of hybrid, pure UV and two-coater presses Reduced costs, enhanced flexibility = greater impact this was the conclusion reached by a comparative cost analysis of hybrid and other types of press in KBA Process No. 1, Focus: direct offset printing on corrugated board published in 2003.The analysis compared the cost-efficiency of three different versions of a Rapida 105 five-colour press: hybrid, pure UV and with two coaters. As more recent studies have shown, the findings apply equally well to the new 18,000sph press generation. In some respects the absolute cost disadvantages of a two-coater press have become even greater, largely due to increased energy prices. On the other hand, the cost differences between hybrid and UV presses have virtually disappeared, so any decision in favour of the hybrid process is now based primarily on the value-added benefits it can deliver in the form of special visual effects. Mathematical models and key data The comparative cost analysis was based on mathematical models derived from actual production data. The basic press was defined as a medium-format Rapida 105 with five printing units, a coater, double delivery extension plus a blanket and roller washing system. The classic two-coater press, hybrid press and pure UV press compared all featured additional equipment (see box). Both the original and the more recent calculations for the three configurations included the footprint, initial investment cost, energy consumption, the cost of consumables (ink, coating, coating plates) and press efficiency expressed as the annual output or print-run costs. KBA utilised the following key data, which have only been updated with regard to press speed: production time: 3,000 hours per year in two-shift operation; level of press utilisation: 85% of production time a realistic figure, since usable time is slightly less (92-95%) than available time; format utilisation: full-format image 700 x 1,000mm (27 1 /2 x 39 1 /2in); ink film thickness: 1µm (39.3µin), with an average tonal value of 30% per printing unit; coating volume (wet): 4gsm on an 80% solid, with the coating Comparison of three coater configurations T H UV volume for primer, aqueous and UV coating assumed to be the same for simplicity s sake; average run length: 10,000 sheets, which in the 3,000 hours of production time available allowing for makeready and an average printing speed of 11,500sph (two-coater press) or 13,000sph (UV, hybrid press) corresponds to 1,500 or 1,800 runs respectively per year; Basic press: KBA Rapida 105 with one coater and double delivery extension (including powder bar and air-cleaning system) plus impression cylinder, blanket and roller washing Two-coater version (T): basic press plus 7 two IR and thermal air interdeck dryers 8 a second coater with doctoring blade and UV capability 9 a dual-circuit system for aqueous and UV coating 10 several end-of-press dryers for conventional inks plus protective coating or conventional inks plus gloss or UV coating (actuated on demand) Hybrid version (H): basic press plus 1 UV capability for the coater 4 two interdeck UV dryers 9 a dual-circuit system for aqueous and UV coating 10 several end-of-press dryers for conventional inks plus aqueous coating or hybrid inks plus UV coating Pure UV version (UV): basic press plus 1 UV capability for all printing units plus coater 2 UV rollers and ink agitators for all printing units 3 a circulating system for UV coating 4 two interdeck UV dryers 5 three additional ports for interdeck UV dryers 6 a final dryer for UV inks plus UV coating 44 Process

45 Hybrid technology Cost-efficiency A two-coater version of the Rapida has a 20% bigger footprint than a hybrid version average makeready: 45 to 55 minutes, with ink changes, cylinder washing times etc based on press room averages. Makeready for job changes on hybrid and UV presses can, in some cases, be much shorter (around 25 minutes) and on a two-coater press 10 to 20 minutes longer (with the same number of personnel) because the two coating plates must be positioned in register, especially for spot coating jobs. Footprint: hybrid press 15% smaller than two-coater press A Rapida 105 five-colour press with two coaters is roughly 3.5m (11ft 6in) longer than a fivecolour hybrid or UV press and has a footprint of around 160m 2 (1,722ft 2 ), compared to just 135m 2 (1,453ft 2 ) for a hybrid press. The effective saving is thus approximately 15%. 120% 100% 80% 60% 40% 20% 0 8% 23% T 4% 8% 8% 4% 88% 88% 88% D H UV Initial investment cost: more than 19% = 320,000 higher with a two-coater than with a hybrid press. Hybrid press = 100%; yellow (88%) = basic press; blue (23%) = two interdeck dryers and additional coater; red (8%) = coating circulation system and final dryer for aqueous and UV coating; violet (4%) = interdeck UV dryer; green (8%) = UV kit (ink agitators, rollers, coating circulating system, final dryer) Initial investment cost: 20% higher for two-coater press than for hybrid press The initial investment cost for the hybrid press was assumed to be 100%, and for the UV press it worked out at roughly the same. A hybrid press has additional drying equipment for handling aqueous coatings on conventional inks alongside UV coatings on hybrid inks, whereas a UV press requires special rollers, ink agitators and docking ports for the interdeck dryers. The two-coater press cost around 20% or 320,000 ($383,000) more, mainly because of the second coater and the two interdeck dryers that are required. Energy consumption: 70% higher with two-coater press Energy consumption accounted for a substantial proportion of annual print production costs. The calculation, which included 180% 160% 140% 120% 100% 80% 60% 40% 20% 0 27% 16% 65% 27% 27% 18% 18% 62% 55% 55% Energy consumption: over 70% = 60,000 per annum (at 18 cents per kwh) higher with a two-coater press than with a hybrid or pure UV press. Hybrid press = 100%; blue (62% two-coater, 55% hybrid and UV) = consumption by drives and central dampener; violet (18%) = consumption by interdeck UV dryer; red (65%) = consumption by IR and hot air dryers; orange (16%) = consumption by end-of-press IR dryer; green (27%) = consumption by end-of-press UV dryer the motor, setting drives, central dampening, interdeck and final dryers, revealed that the twocoater press consumed 70% more energy than the hybrid or UV press. The additional drive power required for the much longer press configuration with two coaters, and the relatively high energy consumption of the two interdeck IR/thermal air dryers and final IR dryer pushed up the cost. At an assumed priced of 18 cents (21 US cents) per kwh the additional annual energy costs for the two-coater press were calculated at around 60,000 ($72,000). This is a sizeable cost block which must be passed on to the customer or it will impact on profitability. Cost of consumables: up to 60% higher with two-coater press A glance at the cost of consumables for the three processes (see 160% 140% 120% 100% 80% 60% 40% 20% 15% 1.1% 6.6% 2.9% 27% 6.6% 133% 66% 25% 6.6% 66% D H UV 0 D H UV Cost of consumables: over 58.6% = 490,000 per annum more with a twocoater than with a hybrid press. Hybrid press = 100%; green = coating plates (133%, 66% and 66%), red (2.9%) = waste from spot coating registration, violet (6.6%) = UV coating, blue (1.1%) = primer, yellow (15%, 27% and 25%) = ink chart below) reveals that here, too, the two-coater press is the most expensive, with costs around 58% higher than with a hybrid press and 60% higher than with a UV press. This is mainly due to the high price of coating plates. In extreme cases the difference in consumables costs alone can total up to half a million euros per year. It was assumed that production with two coaters would require two coating plates, one for matt and one for gloss coating. If the primer for full-solid coating can be applied via a blanket, for example, then the outlay for coating plates is naturally that much lower. Without coating plates the cost of consumables for the twocoater press is lower than for the other two types of press because conventional offset inks are for the moment still cheaper (at around half the price) than hybrid and UV inks. Here, the manufacturers of hybrid inks are challenged to promote this new technology by dropping their prices as volumes increase. There has already been some movement in this direction. Of course, a hybrid press can, if job specifications demand it, also run conventional inks and an aqueous coating, so the cost advantage of the two-coater press exists only if two different types of operation are compared. If a hybrid press is used solely to apply ink, it again becomes more cost-effective than a two-coater press, whose additional coaterrelated aggregates cannot be disengaged when not required, and therefore push up energy consumption. Efficiency: hybrid has the edge Finally, the comparative efficiency of two-coater, hybrid and UV presses was examined in the chart overleaf. Investment sum (I) was based on the same figures as in the chart showing the initial investment cost. Process

46 Hybrid technology Cost-efficiency Although a two-coater press consumes more energy and space, it may still be worth considering for certain applications Absolute output (A) is a fictitious average output which includes all production, makeready and assumed down times. Makeready (M) is the average makeready time. This means that the time spent on work sequences that are not necessary for every job change was distributed evenly over several jobs. In the chart, makeready for the two-coater press was calculated to be just ten minutes longer, on average, than for the hybrid or UV press, based on the assumption that it is possible to work simultaneously on both coaters. This, however, would require additional personnel. Production output (P), ie the number of sheets printed per year, was calculated from the run length, makeready time, printing speed and the available time of 3,000 hours per year. 140% 120% 100% 80% 60% 40% 20% 0 The chart illustrating relative production costs shows that the costs per 1,000 sheets (including makeready) are practically the same with the hybrid and UV press, but between 18 and 20% higher with the two-coater press, depending on run length. The substantial cost advantage afforded by the hybrid press diminishes as the run length increases, since both the longer makeready and the high price of coating plates for the two coaters have a proportionately smaller impact. But for the most common run lengths the production costs with hybrid inks and a UV final coating are much lower, on the whole, than with two coaters. The graph in the chart shows the actual production costs (excluding paper costs) per 1,000 sheets in euros for the hybrid press, according to run length. The costs initially fall as the run D 122 % D % H UV H UV H UV H UV D 85.8% D 85.8% I A M P Efficiency (hybrid press = 100%): I = invested sum (119.2%, 100% and 99.9%), A = absolute output (85.8%, 100% and 100%), M = makeready (122%, 100% and 100%, including extra personnel for coating register makeready at the two-coater press), P = production output (85.8%, 100% and 100%) length increases and then level out at just under 50 ($60) for run lengths of 20,000 sheets or more. So before investing in a new press it is a good idea to determine exactly what is to be produced on it. Conclusion: hybrid is more versatile and cost-effective Despite their similar appearance, a hybrid press includes features that make it much more versatile than a pure UV press, without bumping up the initial investment cost. Thanks to recent advances in ink formulation a hybrid press unites the cost benefits of the UV process a less complex, cheaper press configuration and higher gloss coating levels with the benefits of conventional inks and coatings for certain applications. The mode of operation can be switched without changing the press kit and, depending on the job, with no lengthy job changes. Since the costs are roughly equal, this is where the prime advantages of hybrid are be found compared to UV. A hybrid press has the edge over a two-coater press with regard to the footprint, energy consumption and cost of consumables. Dr Roland Reichenberger D % 48 D 140 % 140% D 138 % D % D % D % 120% 100% 80% 60% 40% 20% euros H UV H UV H UV H UV H UV H UV Relative production costs per 1,000 sheets by run length (including makeready in %): hybrid press = 100%. Graph: absolute production costs per 1,000 sheets on a hybrid press 46 Process

47 Hybrid technology Waterless offset Waterless offset with hybrid inks On 21 April 2005, a Rapida 74 waterless sheetfed offset press in KBA s Radebeul showroom scored a first in Europe by printing hybrid inks. Under the critical gaze of 280-plus print media professionals attending the second KBA hybrid user meeting, the press proved that hybrid inks formulated for waterless offset have excellent runability. It also proved that some superb matt-gloss effects can be achieved with inline coating. KBA pioneers waterless hybrid The two-day hybrid user meeting, which opened on 20 April in Dresden, served as a platform for KBA and the European Waterless Printing Association (EWPA) to promote the use of hybrid inks in waterless offset. The demonstration on the Rapida 74 furnished compelling proof that the hybrid process not only functions without fount solution it even delivers a quality that need shun no comparison with wet offset. Various contrasting gloss effects had been created on a number of different images two days earlier, during preparations for the press demonstration, and these prints were also much admired by the trade professionals and Rapida users present. Once again, KBA has lived up to its role as a driver of innovation, not just in the field of hybrid coating but also in waterless offset, for which it has developed a unique keyless inking unit. The elimination of two process variables water, which is relatively unstable, and key-by-key inking, which is heavily influenced by the subjective perceptions of the operator lays the foundations for standardising print production. KBA has already implemented this technology in digital and conventional sheetfed offset (in the form of the Gravuflow inking units for the 74 Karat and Rapida 74 G, and the keyless inking units for the Genius 52 and other KBA-Metronic presses used to print film and data storage devices) and in newspaper offset (the Newsflow inking units for the Cortina). anese manufacturer Toyo Ink, is currently the only waterless hybrid ink on the market. However, some European ink manufacturers are working on similar inks, and this is sure to enhance the appeal of hybrid offset in the near future especially in tandem with Gravuflow ver- Waterless UV specialist The author of this article, Detlef Braun, is not only an active member of the EWPA but also runs his own company, Druck & Beratung. D&B is a consultancy specialising in the provision of training and support in waterless offset production with UV inks, a sector of the packaging and plastic printing market that is experiencing strong growth. As a result D&B has relocated to bigger premises (Lahnstrasse 31, Mülheim an der Ruhr, Germany. Tel: , Fax: -12, Waterless UV offset is a challenging process that requires meticulous planning and preparation if the risk of investing in the wrong equipment, and thus provoking customer dissatisfaction, is to be eliminated. Braun knows what he is talking about: at Druck & Beratung a press has been printing plastic cards for many years. The dual drying properties of waterless hybrid inks place them firmly in his remit. A major printing aid that Braun has developed is a dedicated control strip, the H-1/04, for checking density and ink trapping. The individual patches are triangular, which is a more appropriate shape for the ink-splitting properties of highly viscose waterless UV inks. It remains to be seen whether this strip will need to be used with waterless hybrid inks. sions of Rapida presses, which are already a popular tool for expanding the range of applications possible. Forum participants seized the opportunity to address questions concerning dampener-free offset to Detlef Braun, the first chairman of EWPA and the author of this article. They were particularly keen to know whether hybrid inks can be used to print film. Since film printing, which is currently the domain of pure UV and waterless UV, is a challenge that hybrid must still overcome, the answer was no, and other ink specialists would say the same. The outlook The ink that was used, FD Hybrid Aqualess Soy M supplied by Jap- Process

48 Hybrid technology Waterless offset The world s first waterless hybrid ink comes from Japan Toyo Ink was the first manufacturer worldwide to develop a hybrid ink, the FD Hybrid Aqualess Soy, for waterless offset. Japan is a waterless offset stronghold:toray has been making waterless printing plates since 1977, and alongside Toyo Ink there are three other Japanese manufacturers in the market for waterless inks.the country has a higher proportion of waterless sheetfed offset presses (excluding DI presses) than anywhere else in the world. Toyo Ink s portfolio includes five waterless inks: Aqualess Ultra L/M for conventional sheetfed offset presses; Aqualess Karat for keyless presses (approved by KBA for the 74 Karat, Rapida 74 G and Genius 52); Aqualess Ecoo for direct-imaging offset presses (approved by KBA for the 46 Karat); Aqualess UV for UV printing on plastic cards, film and CDs/DVDs; FDHB Aqualess Soy L/M for hybrid production. Toyo Ink not only boasts a lot of experience in the formulation of waterless inks but is also a long-standing manufacturer of UV and electron beam inks along with a hybrid ink series for wet offset, FDHB Eco-Soy. So it is not surprising that the company has succeeded in creating a suitable blend of hybrid and waterless inks. One of the challenges associated with developing FDHB Aqualess Soy was to blend the two completely different types of resin commonly used for hybrid and waterless inks, and to find a formula that was compatible with a silicone oil substitute (hybrid inks should not contain silicone because it impairs their UV coatability). Toyo Ink found that soya oil was a satisfactory substitute, and used this as the vegetable oil component. Ink viscosity has a major impact on printability in waterless offset. Generally speaking, the viscosity or tack of waterless inks is higher than that of wet offset inks, but lower than that of waterless UV inks. Hybrid ink is less viscous than waterless UV ink. FDHB Aqualess Soy is even formulated in two temperature-specific versions: L for lower and M for medium plate-cylinder temperatures (see table). The temperature-control systems for KBA presses are programmed for the higher end of the medium temperature range because this improves ink application. FDHB Aqualess Soy is not yet available in special colours, but the black in the process scale can be replaced by a more concentrated formula for achromatic separations. FDHB Aqualess SOY was put through all the usual tests. Paper was printed wet-on-wet at a running speed of 50mpm (154ft/min) and cured by one 120W/cm (300W/in) UV lamp. 15 seconds later its was tested for smearing and set-off in the pile. It was found that there was absolutely none with hybrid waterless inks and very little with FDHB Eco-Soy hybrid wet offset inks. Rub-resistance was measured two hours after impression in an oscillator whose 500g (17oz) testing head was run across the printed image 200 times.rub resistance was found to be good (a 4 rating), just one grade below that of UV inks, which was excellent (5). De-inkability using alkaline flotation a fundamental issue with UV inks was also checked. Toyo found that ink residue on hybrid-printed paper was almost as low as on conventionally printed paper: less than 5mm 2 /m 2 (0.0007in 2 /ft 2 ). This compared with around 85mm 2 /m 2 (0.01in 2 /ft 2 ) on UV-printed paper. The test used to determine ink smearing and set-off when the sheets in a pile shift relative to each other showed that FDHB Eco-Soy wet offset hybrid ink (left) was prone to both, whereas FDHB Aqualess Soy waterless hybrid ink (right) was totally resistant. The lower line of images shows the test sheets with smear marks, the upper one shows ink set-off on the underside of the overlying sheet. (Photos: Toyo Ink) Rheological and thermal properties of waterless hybrid inks Parameter FDHB Aqualess SOY M FDHB Aqualess SOY L Tack at 30 C Flow at 25 C Dynamic viscosity at 25 C Pa s Pa s Recommended plate temperature C C The demonstration showed that the waterless hybrid process is 100 per cent suitable for printing paper, carton and solid board. The absence of fount solution alone ensures that waterless inks deliver a higher gloss, so combining waterless and hybrid processes is an obvious step because this will enhance the gloss of the UV coating still further and enable even sharper matt-gloss contrasts to be achieved, opening up new applications for both processes. The EWPA, in association with KBA, is happy to assist its members with this technology. Detlef Braun Toyo Ink's waterless hybrid ink, FDHB Aqualess Soy 48 Process

49 Ecology Emission testing Testing press emissions For the past five years the Berufsgenossenschaft Druck und Papierverarbeitung (BG), the German print industry s equivalent of the HSE in the UK and OSHA in the US, has been busy promoting low-emission technologies by awarding exemplary systems emission tested accreditation through the testing and certification centre attached to its Expert Committee on Printing and Paper Processing. The first 18,000sph press to receive this accolade was the KBA Rapida 105. The consumables used in the tests included hybrid inks and the appropriate washes. Emerging emphasis on the environment There is an emerging emphasis in society today on environmental protection, and more specifically on the reduction of emissions. In recent years there has been a lot of debate, sometimes with media exposure, on what has become known as emissions trading, and this has focused the spotlight of public interest more intensely on this particular aspect. In fact environmental protection has been an ongoing issue for more than thirty years. Just think back to studies like those by the Club of Rome on growth thresholds (1973), or the Global 2000 paper published by the US government in While environmental objectives or initiatives are often the object of controversy, it may safely be said that, in essence, the political powersthat-be have all expressed a firm commitment to reducing and limiting emissions. In general, society s response to environmental issues has undergone a sea-change, and as a result there has been an increasing demand for greener products. In the graphic arts industry this was initially expressed in a desire for ecologically manufactured paper, eg recycled. In the course of time customers have steadily raised their expectations regarding the sustainability of printed products. But environmental protection also means safeguarding health, both of employees in the workplace and of the general public. Back in the early 1990s the BG squared up to this challenge and assumed a pioneering role in the print media industry. An industry initiative, solvents in offset, set about tackling the hazards posed by solvent emissions in the press room. The BG is committed to minimising emissions. Day in and day out printers are exposed both to physical emissions like noise or radiation and to material ones like powder or solvents. These are often associated with pollution of the ambient air in the press room and at the press. Optimising the printing process by developing low-emission presses is a vital approach to addressing these issues. Emission tested accreditation The first press to receive the BG s emission tested certificate for exceptionally low-emission technology was a KBA Rapida 105 at Drupa 2000, precursor to the new 18,000sph generation unveiled at Drupa To qualify for accreditation, the press design and operation must be proven to reduce emission levels to substantially below the The BG s accreditation procedure for the new Rapida 105 entailed recording emission levels at all the printing units and the delivery lowest thresholds permissible in the EU. The emissions measured are of solvents (volatile carbons in washes, fount solutions, inks and coatings), aerosols (eg ink and coating mist), dust (powder), ozone, UV radiation and noise. The first step towards determining emission levels is to obtain data on the various aspects of offset print production on the shop floor. For this purpose a series of tests is conducted on different types of substrate. The inks used may be conventional, UV or special inks such as hybrid inks. Applications involving aqueous or UV coatings are tested in the same way. The certificate indicates the applications for which the specified press has been approved. Safety features are, of course, another aspect that is closely scrutinised: checking for compliance with European safety regulations is part and parcel of the accreditation procedure. Testing emissions at the new KBA Rapida 105 The BG subjected the 18,000sph new-generation KBA Rapida 105 to a series of challenging tests. Among other things, the purpose of these tests was to determine whether the criteria for awarding an emission tested certificate had been met. The metrological examination, which was carried out at the end of 2004, entailed running a series of tests on both paper and board. Two hybrid inks, one UV and two conventional inks were used, as were diverse UV coatings, one aqueous coating and a number of different washes. It should be noted that all the print tests were run at an output Process

50 Ecology Emission testing of 14,400 sheets per hour, equivalent to 80% of the rated maximum, and with no alcohol in the fount solution. An analysis of the findings revealed the following: Ink mist at each of the printing units was well below the stipulated threshold of 1.5mg/m 3, and in many cases more than 30% lower. As expected, the 105 cleared the IPA concentration hurdle with flying colours, since the absence of alcohol in the fount solution made the entire question of IPA emissions superfluous. For users this brings a number of cost benefits: although advances have been made in reducing IPA levels, the mere fact of using alcohol generates costs beyond the actual price, eg with regard to health and safety (storage, fire prevention etc). Other emissions, eg carbons, ozone, UV radiation, powder and noise, were also well below the permitted levels. It is good to know that the new generation KBA Rapida 105 also meets the criteria for the emission tested certificate, even though it has a higher output of 18,000 sheets per hour. This is all the more remarkable because higher press speeds generally give rise to increased levels of particulate and non-particulate emissions, especially noise. Hybrid technology a stable process Subjecting the new Rapida 105 to such a rigorous examination by the BG s testing and certification centre served two purposes. The first was to ensure compliance with all national and European environmental, health and safety standards. The second, in conjunction with materials testing (eg monitoring the impact of inks and washes on the volume of rubber consumables, conducted by Fogra on behalf of KBA) was to promote process stability and the proper application of hybrid technology. In future, users will be able to recognise at a glance which products fulfil the relevant criteria for hybrid production. This will also help prevent products being utilised that can have harmful side effects on personnel and/or materials. Health protection is environmental protection and vice versa It is not only public authorities who expect printing plants to play an active role in protecting the environment: customers are increasingly making the same demands. Presses boasting the BG s emission tested seal of approval are a crucial component since they furnish the technology for compliance. The key to success, however, is responsible behaviour on the part of users. Here, education and training are essential in enabling them to choose the appropriate technology and chemistry, and deploy them as intended. Today, presses bearing the emission tested seal are often dubbed eco-presses. In this instance eco stands for both ecology and economy. Ecology, because the press enables the operator to print with reduced emissions by optimising the printing process. Economy, because the press has the technology to utilise the necessary auxiliaries more efficiently than ever before, substantially reducing costs. The printing process can thus be made much more profitable. What is more, lowemission presses may even be eligible for state subsidies in certain European countries. In addition to fulfilling its original purpose, environmental and health protection can, if properly implemented, also reduce costs and enhance productivity. Dr Bernhard Küter, Dr Axel Mayer, BG Druck und Papierverarbeitung KBA sheetfed marketing manager Jürgen Veil accepting the BG s emission tested certificate from Albrecht H Glöckle in April 2005 at the second hybrid user meeting In black and white: KBA s 18,000sph new-generation Rapida 105 satisfies all the criteria for the emission tested certificate issued by the BG Druck und Papierverarbeitung 50 Process

51 Press ecology Fount solution Impact of fount solution on print production with hybrid inks Hybrid inks can be applied easily at maximum press speed without the need for isopropyl alcohol (IPA) in the fount solution because the dampening tolerance range is not as narrow as with UV inks. This has been confirmed by Fogra in studies conducted using new IPA-free two-component hybrid inks formulated by DC DruckChemie. It is a well-known fact that, in offset, the ink/water balance is more of an issue with UV inks than with conventional inks. The more sensitive reaction of UV inks is expressed in higher levels of makeready waste and in an extremely narrow dampening tolerance range during print production, which means that the printing process must be constantly monitored and the dampening and printing units repeatedly adjusted. In many cases this leads to a reduction in production speed, which makes it an economic issue. In a government-sponsored research project, Enhancing the ink/water balance in offset with UV inks, Fogra Forschungsgesellschaft Druck in Munich has examined the problems arising both with UV and with hybrid inks. Dampening adjustment with new test chart The project kicked off by asking how the stability of the dampening process can be measured at the press. Because the printing units are set individually they all react differently. So although the press operators adjusted the dampening units with the utmost care, using the customary roller proof, tests revealed significant variations from one printing unit to the next. It was soon concluded that a new, more sensitive instrument was needed to check and adjust dampening. Fogra developed such an instrument in the form of a dampening test chart (see box). This enabled informative dot gain curves (ie dot gain as a percentage in the printed image against tonal values as a percentage in the test chart data file) to be calculated during the print tests. A UV ink and two hybrid inks were compared in conjunction with an alcohol-based fount solution (IPA concentration 10%) that is already in widespread use and a new alcohol-free fount solution. Fogra fount control test chart The test chart contains highly sensitive scan elements for monitoring the uniformity of the dampening film across the entire plate.with the aid of this chart it is possible to adjust all the dampening units uniformly, while at the same time monitoring and logging press status. It enables technical problems such as rubber roller shrinkage in the inking unit, wrongly adjusted potentiometers in the printing units, deformed or worn dampening rollers in individual printing units and technical differences in the various combinations of ink and fount solution to be detected easily and simply. To determine the ink/water balance, proceed as follows. After loading the plate with the test chart, run off a proof print in the usual fashion until a reference colour density (generally 1.4) has been achieved in the solid. Then progressively reduce duct roller speed (and thus the volume of fount solution applied to the plate) until the image begins to smear. As a rule smearing will only be perceptible on one side of the sheet. Increase the roller gap in the dampening unit and print a fresh proof. Reduce duct roller speed again until smearing occurs. If the UV print production with IPA fount solution a tightrope walk A comparison of graphs 1 and 2 overleaf reveals perceptible differences in dot gain. Graph 1 clearly shows why the ink/water balance is so critical in this specific permutation of UV ink and IPA fount solution. A duct roller setting of 60 was the only setting at which the dot gain curve complied with the offset standards laid down by the BVDM (German Printing and Media Industries Federation). Minimal changes in dampening feed, which on a running press can easily be caused by a build-up of deposits on the rollers or changes in temperature etc, led almost immediately to dramatic deviations in colour reproduction within the image. So with this combination of ink and fount solution the press operator must monitor the process constantly and make any adjustments necessary to produce saleable prints. The behaviour of the same UV ink with an alcohol-free fount solution (graph 2) was far less critical. Here, changes in duct roller settings produced little variation in dot gain, which remained close to the standard. The fount solution used was supplied by DC DruckChemie in Ammerbuch, and has since been developed to market maturity. It is described as a two-component version with no associated health smearing is distributed evenly across the entire plate width, this indicates that the volume of fount solution being applied to the plate is uniform and that the dampening unit is therefore evenly adjusted. The next step is to increase duct roller speed in predefined increments. After that, pull a number of printed sheets, measure the dot gain and compare the results for this particular combination of ink and fount solution with other combinations. The test chart also allows ghosting effects and other flaws to be assessed, but these are not the subject of this article. The test chart data file is available to Fogra members and non-members ( as part of a service package which includes practical training in applying the test chart, and basic on-site press setting by Fogra personnel. Process

52 Press ecology Fount solution 1 Dot gain with UV ink and a 10% alcohol fount solution at six dampening duct settings between 35 and 99 2 Dot gain with UV ink and a UV-optimised alcohol-free fount solution at five dampening duct settings between 60 and 99 hazards: a patented component, AlkoGreen, replaces IPA, Fount- Green is the compatible concentrate. Hybrid inks non-critical with and without IPA The same procedure as for the UV inks was used to examine the two hybrid inks. Hybrid ink 1 (supplied by the same manufacturer as the UV ink) was found to be much easier to print, even with a conventional IPA fount concentrate (graph 3). Although this combination of ink and fount solution did not eliminate changes in dot gain when dampening feed was changed, these were much smaller than with UV ink. When hybrid ink 1 was run with a fount solution specifically enhanced for alcohol-free UV production DC AlkoGreen/FountGreen the dot gain curves were much flatter and closer together (graph 4). Hybrid ink 2, which was supplied by a different manufacturer, behaved in much the same way as hybrid ink 1 (graphs 5 and 6). Summary The behaviour of hybrid inks is generally much less critical than that of UV inks, and they are trouble-free even without the use of isopropyl alcohol, as was demonstrated with the IPA-free DC AlkoGreen/FountGreen solution. They therefore enable the press to run at maximum speed. During the accreditation procedure for the emission tested certificate issued to the Rapida 105 by the Berufsgenossenschaft Druck und Papierverarbeitung (the equivalent of the HSE in the UK and OSHA in the US), AlkoGreen/ FountGreen was used as a fount solution and performed to specifications at a production speed of 14,000 sheets per hour. Dr Wolfgang Rauh, Fogra 3 Dot gain with hybrid ink 1 and a 10% alcohol fount solution at seven dampening settings between 18% and 75% 4 Dot gain with hybrid ink 1 and a UV-optimised alcohol-free fount solution at ten dampening duct settings between 27% and 75% 5 Dot gain with hybrid ink 2 and a 10% alcohol fount solution at seven dampening duct settings between 18% and 75% 6 Dot gain with hybrid ink 2 and a UV-optimised alcohol-free fount solution at seven dampening settings between 30% and 75% 52 Process

53 Handling Benefits and practical tips Sophisticated, but soon mastered The number of hybrid coating enthusiasts worldwide is rapidly growing. For some, its simplicity facilitates entry into UV production, which is much more challenging. For others, the fact that some stunning and highly sophisticated visual effects can be achieved with surprisingly little effort plays a decisive role. And many have been won over by the relative ease with which it is possible to switch cost-effectively from one process to another, enabling them to handle jobs that specify high-end finishing alongside more routine work. The options available, the benefits delivered by hybrid applications and the limitations to which they are subject were discussed in detail at the second KBA hybrid user meeting in April 2005, which gave prospective and current users an opportunity to compare notes, come up to speed with the technology and pick up some useful tips from KBA and its development partners. A touch-screen is essential at the console for the hybrid Rapida (Photo: Kleeberg) Mode change: quick and simple KBA hybrid presses have a lot of ingenious features for making makeready, cleaning and production changeover easier, faster and safer provided, as has been emphasised several times in this publication, that only the consumables and aids approved and accredited by KBA are used. One key advantage is that the press operator does not have to change the blankets and rollers when converting between hybrid and conventional production. In hybrid mode, hybrid inks are run in conjunction with a final UV gloss coating applied in the coater. For spot effects, an optional matt overprint varnish can be applied in the final printing unit. In conventional mode, ink application can be followed by an aqueous coating, which can also contain special-effect pigments. The interdeck and end-of-press dryers are all plug-in modules, so they can be positioned freely, activated or deactivated selectively and reduced or increased in number in just a few quick movements to suit job specifications and the relevant mode of operation (see chapter on KBA drying and curing systems, pages 6-9). For easier conversion, standard equipment includes a coating feed system with two separate circuits and time-variable washing programs, with the wash for the coating recovered and returned to two separate tanks. With Harris & Bruno s LithoCoat system, for example, conversion from a UV to an aqueous coating, or vice versa, takes just seven minutes, and from one aqueous coating to another just two minutes. Tip: Regularly maintain the rubber rollers to improve their service life. Remove ink residue and limescale, and give them a thorough clean from time to time. Whatever the production mode, rubber rollers are prone to swell and shrink even with the hybrid inks and washes recommended by KBA, though with these the change in volume remains within the tolerance range (as can be seen in the Fogra tests on pages 39-43). Nonetheless, depending on the inks and washes used and the frequency of mode changes, mixing hybrid and conventional production can cause greater wear and tear on the rollers than conventional production alone. Flexibility: exploit it efficiently Hybrid production accounts for 30% to 70% of output by the 250- odd Rapida users worldwide who operate a hybrid press line, so rapid mode conversion is a key factor in maintaining flexibility. Even so, for economic reasons it is advisable to minimise the number of mode changes by sequencing as many jobs as possible in one mode before switching to the other. Tip: Calculate whether it would be more cost-effective to split your weekly production routine into hybrid days and conventional days. Customers could be offered a price incentive to support this cost-saving regime by delivering their data within the relevant deadline. Printing curves: almost identical in both modes Print entrepreneurs installing a hybrid press as an introduction to UV technology will be glad to learn that there is no steep learning curve as far as dot gain is concerned. With a pure UV press consuming UV inks, UV-resistant ethylene propylene diene monomer (EPDM) blankets and rollers, the characteristic printing curves and the corrective values for dot gain compensation in pre-press would have to be completely recalculated. Kodak Polychrome Graphics Excel plates are used for hybrid production on the presses in KBA s showroom in Radebeul The dot gain curve with hybrid inks is just as flat as with conventional inks, making it easier both to adopt hybrid technology and to switch from conventional to hybrid mode. The curves in the screenshot above were determined using KPG s new Sword Ultra thermal plates which do not need to be baked for UV and hybrid production Process

54 Handling Benefits and practical tips With hybrid inks, on the other hand, the low dot gains familiar from conventional production still apply. Of course, as with any new press, the printing curves and an ICC press profile for colour management must still be calculated or modified. And as with any change of ink, substrate or blanket, it is advisable to check print characteristics when switching from conventional to hybrid inks, especially if the job involves images that are prone to colour fluctuations. If the consumables approved by KBA are used as directed, modifying print characteristics and dot gain should be a relatively minor task. This is a big advantage and not only makes it easier to learn the new technology in the first place but also to convert between hybrid and conventional production. The only difference as far as pre-press is concerned is that the plates whether baked or not must be UV-resistant (see chart on page 20). Tip: Use the same brand of plate for both modes of operation so as to minimise the number of changes necessary in the relevant parameters. UV inks will not contaminate the press. Tip: Further reduce VOC emissions at your hybrid press by using an alcohol-free dampening solution. Although all hybrid Rapidas already bear an emission tested seal, dispensing with alcohol will make the press even greener and improve the working climate in the press room. Anilox roller: easy care Over and above the automation modules that have become routine items of equipment programmable plate changing, CIP3/4 link, storable and reusable press settings, automatic blanket and roller washing time- and laboursaving features and design were a primary focus of KBA s development activities. For example, for printers wishing to play safe during changes of coating, the anilox roller and blade duct can be easily accessed and cleaned manually in just two minutes, though as a rule the automatic wash-ups for the coater and pumping systems are perfectly adequate. Tip: A quick method for testing whether the anilox coating roller needs cleaning after a print run is to colour the coating with food dye and apply it as a full solid. You can then check its uniformity either visually or with a densitometer. Normally the anilox roller in the coater must be changed only when it is worn, which with the materials and engraving techniques used today is very rarely. But it may need changing if a different pick-up volume or type of aqueous coating (with large special-effect pigment particles) is specified. This takes just a few minutes and does not even require a hoist, because KBA has introduced rollers made of lightweight aluminium. All the press operator has to do to change the roller is remove the screw on the doctor chamber and swing it out of the way, open the bushes, lift out the roller and replace it with the new one. Tip: Although the anilox roller is light enough for one person to handle alone, it should always be lifted out and carried by two people, especially if the roller is too wide to allow one person to hold both the spindles. Balancing the roller on the palm of one hand while gripping a spindle with the other is risky because the other spindle or the end of the roller could easily knock against some obstacle and sustain damage. The lightweight rollers are no less durable than their heavy conventional counterparts. Not only that, they require less energy input to revolve at the new-generation Rapida s maximum production speed of 18,000 sheets per hour. Ink/water balance: more stable than in UV, alcohol-free no problem Participants at the latest KBA hybrid user meeting confirmed once again that the ink/water balance in hybrid production is much more stable than in pure UV production, but must be monitored more closely than in conventional sheetfed offset. So the demands made on the qualifications of the press operator are not excessive. As the preceding chapter ( Impact of fount solution on print production with hybrid inks ) illustrates, the correct balance between dampening and inking can be stabilised still further by using a compatible alcohol-free solution. Hybrid inks will pose no problems if these conditions are met. What is more, hybrid inks have the advantage of being immune to misting and unlike Automatic washing systems can cause a build-up of wash and ink in the blade duct (top). With the appropriate hybrid wash this does not happen (bottom) (Photos: Fuji Hunt DS Druckerei Service) Hybrid inks are also available in cartridges, which is the form Industriedruck Dresden prefers for its hybrid Rapida 105 The aluminium anilox roller developed by KBA for the coater is so light that it can be changed without a hoist 54 Process

55 Handling Benefits and practical tips Suction air paths in the Air Clean System Hybrid washes: economical and effective Hybrid washes can be used to clean both hybrid and conventional ink off rollers, blankets and cylinders. The challenge for the chemist lies in overcoming their opposite polarities, since conventional inks and the conventional constituents in hybrid inks are nonpolar, the UV constituents polar. Most washes for hybrid production reflect the current state of the art in pressroom chemistry: they enhance the rinsability of the rubber, for example, by emulsifying spontaneously with water, and the stability of the wash-inwater emulsion thus created means that a smaller volume is required, cleaning is more thorough and there is no contamination of the washing system. Ink particles and paper dust are trapped in the emulsion and removed with it, so there is virtually no build-up on the pipework, blade duct or drip pan. In general, a good wash can be recognised by the fact that, after cleaning, the blanket and roller surface dry and are operable almost immediately and promote an optimum ink take-up or splitting, which helps cut waste. It is also important to choose a wash that is appropriate for the automatic washing systems routinely fitted on KBA hybrid presses. The accreditation process tests wash compatibility with the rubber (no swelling or shrinkage), but not the risk of corrosion. However, with modern washes this should be very small. Tip: The same applies to hybrid washes as to hybrid inks: only use products that have been tested by Fogra and approved by KBA. Always follow ink manufacturers recommendations with regard to the compatibility of their products with specific hybrid washes. Delivery: minimising contamination The double delivery extension containing the various end-ofpress dryer modules that support dual-mode operation (VariDry system) with the new-generation Rapida 105 has been elevated to make it easier for the press crew to insert and reposition them. In addition, changing the sheet path has increased the distance between the powder bar and the final UV dryer, reducing the risk of contamination of the reflectors in the UV dryer. This means that, on presses with a perfect coating capability, more powder can be used to eliminate the form of blocking known as the glass-plate effect. Straight printing on a hybrid press normally requires very little powder (eg where contrasting spot/gloss effects have been created with The interdeck UV dryers for the Rapida hybrid press are easily accessible and can be transferred to another port in a matter of minutes overprint varnish and UV coating) or none at all. Tip: When giving the reflectors an occasional clean, avoid touching the surface of the mirrors because dust and powder will tend to cling to the fingerprints. In this connection it may be worth fitting an optional aircleaning system (ACS) at the delivery. Positioned directly above the delivery pile, this additional extractor prevents powder and paper dust from entering the dryer zone, keeps the gripper chains and sheet jogger clean and draws off residual vapours that can arise after ozone extraction above the end-of-press UV dryer. With an ACS at the delivery the press operator will no longer be exposed to ammonia emission from aqueous coatings or the typical ozone emission from UV radiation curing. IR radiation power level: less is more As any printer knows, paper is extremely sensitive. It will warp from the edges inwards if allowed to absorb uncontrolled moisture from the ambient air, and will shrink and become brittle if moisture is withdrawn. And because the pressroom climate throughout the world varies considerably depending on the geographical location and plant sophistication, the condition of the paper or board prior to acclimatisation differs accordingly. Tip: Ask your paper vendor not to deliver paper that is shrinkwrapped or sealed in plastic bags, and refuse to accept stock wrapped in this way. Plastic film can cause condensation and thus warping, which even an extended period of acclimatisation cannot remedy. Process

56 Handling Benefits and practical tips Shrinkage and brittleness caused by IR or UV radiation were a major issue at the last KBA hybrid user meeting. This is because the final IR dryer, which is fitted in a hybrid press to dry aqueous coatings when conventional inks are used, can also be activated, or may still be emitting heat, alongside the end-of-press UV dryer during hybrid production. Although the heat emitted by infrared radiation promotes oxidation in the hybrid inks, the IR radiation emitted as a by-product of UV radiation is normally strong enough to support oxidation in the delivery pile even with extensive ink coverage. Provided no heat-sensitive plastic film is being printed, this is a desirable side-effect because it also promotes curing in the hybrid inks and UV coating under UV radiation. In general, the amount of IR heat generated by UV lamps is quite sufficient for oxidation, especially if the image contains a lot of dark areas. Exposing cured hybrid ink to IR radiation prior to entry into the final UV dryer would cause the ink to loosen and this in turn would attack the UV coating from below, ie from its uncured side. The result could be blocking in the pile. However, if the image is pale, or features large areas that are print-free or have low ink coverage, additional IR radiation may well be beneficial. But even here, less may still be more, ie the IR lamp should be set at its minimum power level. Some printers use a rod hygrometer to measure the moisture levels in the air between the sheets in the feeder and delivery piles, and use the difference in moisture content to calculate the thresholds for IR radiation. However, it takes a long time for the relative air humidity in the delivery pile and the residual moisture in the paper or board to attain equilibrium. Only a highly experienced printer can draw usable conclusions from this measurement. A more reliable method, but one that is not feasible at the press, would be to measure the absolute water content in the substrate, which should be at least 5%. KBA recommends using twintube carbon emitters for IR radiation, since they are the most energy-efficient. Tip: Measuring the pile temperature is better than measuring the moisture content. UV dryer: no more energy than necessary Excessive UV radiation can damage the coating film in the same way that excessive IR radiation can damage the substrate, by making it brittle, which can cause the film and the underlying paper to crack when folded. The power level of the final UV dryer should therefore be set no higher than absolutely necessary. The chapter on Choosing the right testing method (page 14), describes the most reliable methods for checking whether the UV coating has cured properly. One method that was not mentioned, because it is unsuitable, is to check the UV intensity with dedicated measuring strips which, according to the dryer manufacturers, respond to both UV and IR radiation. Tip: As far as energy input in IR drying and UV curing systems is concerned the following applies: no more than necessary! Sheets printed and coated using the hybrid process share the virtue of UV prints in that they can be finished without delay, eg on a flatbed die-cutter like this Bobst SP 142-CER II at Leopold Verpackungen in Ludwigsburg Inadequate curing may also be attributable to UV lamps that are too old. UV coatings and hybrid inks are not formulated for specific wavelengths, so the highest peak in the UV radiation spectrum is not necessarily a measure of effectiveness. Make sure that the UVC lamp in the final UV dryer is always fresh, because as the lamp ages the UV ratios change. When a lamp needs replacing, always fit the new lamp in the first position and move the others on. The first lamp is where the maximum level of UVC radiation is needed because that is where the curing process in the UV coating is initiated, whereas the subsequent two lamps merely sustain and deepen the process. If the paper coating is not UVcompatible it may, in some cases, react undesirably to UV radiation and become brittle, causing it to crack when the paper is folded. Most paper manufacturers are familiar with this issue and can provide information on the UVcompatibility of specific types of paper and board. There is no quick fix to this problem because simply reducing the amount of binder, or using a more flexible one, may impair printability. Tip: To prevent heavier coated stock stock, eg 150gsm (102lb book) or upwards, from cracking, crease it prior to folding. Also, make sure that finishing equipment is set properly. Some users recommend spraying the crease on difficult substrates with a mixture of water and alcohol. Odour emission: notify or test in good time Binders may also be responsible for odour emission by the paper coating when it is exposed to UV radiation. Odour emissions by hybrid inks have been dramatically reduced in recent years, and UV coatings have long since qualified as sufficiently odourless for food packaging. But even if the individual substrate, hybrid ink and UV coating normally emit little or no odour during UV radiation, in combination they may still deliver a nasty surprise in the form of an unpleasant smell. Tip: Many paper manufacturers are happy to test specific combinations of substrate, ink and coating for their customers in order to eliminate the risk of unpleasant odours being emitted when the consumables are used together. Conclusion: hybrid not a 'mission impossible' At the second KBA hybrid user meeting in 2005, as at the first in 2003, users were united in their conviction that going hybrid was a wise move. The willingness to experiment demonstrated by print entrepreneurs in search of fresh applications for hybrid coating proves that the process has been well and truly mastered and is an inspiration to creative design. Adopting hybrid technology is no great challenge because the production method is basically the same as with conventional inks: it merely expands the choice of inline coating options. Any odours emitted by the paper are caused by the same phenomena as in pure UV print production, but otherwise the press operator generally has to contend with far fewer problems. Dieter Kleeberg 56 Process

57 Handling Benefits and practical tips Second hybrid user meeting, April 2005, Dresden and Radebeul Jürgen Veil, head of KBA sheetfed offset marketing, and his team were instrumental in honing hybrid technology to its present level of maturity. An accomplished and humorous host, he displayed a rare level of detailed knowledge not only of hybrid production but of all the related technologies as well Authentic print jobs boasting some spectacular hybrid coating effects were a focus of interest (Photo: Kleeberg) The 280-plus users who attended the meeting were unanimous in their conviction that hybrid technology is now a viable alternative to double coating and pure UV A Rapida 105 six-colour coater press with double delivery extension in KBA s Radebeul showroom demonstrated the ease with which hybrid inks, a matt overprint varnish and a high-gloss UV coating can be applied inline Participants could draw on the expertise of specialist panels like this one comprising representatives from dryer manufacturers and KBA Print demos with waterless hybrid inks on a KBA Rapida 74 were equally impressive Process

58 Applications Examples Near-limitless options Thanks to the creativity of many Rapida users and their advertising clientele, hybrid technology has evolved into a genuine alternative to double coating or pure UV, and one that furnishes options unparalleled by either of these two processes. It initially captured the interest of packaging printers, who were delighted to discover that it supports direct offset on folding cartons, displays and corrugated board. But soon the unusual contrasting matt/gloss effects that could be created fired the imagination of graphic designers specialising in high-grade commercial work, who have since pioneered new applications for achieving some stunning visual effects. Since then hybrid technology has also been taken on board by a few pioneering film printers. Another new field of application is counterfeit protection for packaging and labels.there are even one or two interesting examples of 'multi-hybrid' presses double-coating and UV presses with hybrid capabilities. Hybrid coating as growth opportunity Hybrid print production with an inline UV gloss coating is more than just an easy introduction into UV technology it boasts some unique capabilities that justify its conscious adoption in preference to other processes. High gloss. This can be achieved much more economically than with a two-coater press and almost as cost-effectively as with a UV press. Gloss contrasts. These, too, can be created more simply than with a two-coater press and in perfect offset register. Two different types of coatings can be applied, more specifically a matt or structured overprint varnish (as a spot varnish) and a UV coating (applied as a full-solid gloss coating, which is repelled by the spot varnish). The visual impact achieved outshines even such acclaimed alternatives as drip-off and twin-effect coating on conventional presses equipped with aqueous coaters. This feature provides hybrid printers with a unique tool for raising their profile in the marketplace. Many advertising agencies would like to exploit the potential this capability offers but have trouble finding a printer. So for printers hybrid represents a means of winning new custom. Counterfeit protection. The above-mentioned contrast coating capability developed by KBA s engineers opens up a profitable niche market: that of counterfeit protection for packaging using images concealed within the coating. Diversity. Hybrid coating is suitable for virtually every market addressed by sheetfed offset. Even synthetics, metallised and still more challenging transparent paper have been found to be hybrid-compatible. One exception is food packaging: although the ink industry has already developed low-odour hybrid inks, it has not yet come up with totally odour-free inks or combinations of inks, coatings and substrates, nor is it likely to do so in the immediate future, so this will remain a UV domain. Even in pure UV production, odours can be emitted if the acrylates in the UV ink do not cure properly. Pure UV will also maintain its dominant position in plastic printing because hybrid inks only adhere to certain synthetics. Flexibility. Production can be switched effortlessly between the two different modes of operation, so if there is not enough hybrid work to keep the press running at maximum capacity, routine jobs specifying conventional inks with aqueous coating can be scheduled without dot gain having to be recalculated. The fact that the characteristic curves for hybrid inks are similar to those for conventional inks makes it much easier for staff to take the new technology on board. In the USA the two types of ink often differ, making it necessary to equip hybrid presses with special rollers and blankets, but this is not in keeping with KBA s hybrid philosophy. Even so, KBA is happy to give these customers the same level of support it gives its other customers in implementing hybrid technology. Creating a spot coating forme in offset register No matter whether the relevant page elements have been generated as an image, graphic or layout file: the spot coating template can simply be generated from the files in the relevant publishing program. This can take the form of individual levels from a Photoshop or Illustrator file or diverse elements from an entire page, like this one from a KBA calendar. The text, calendar dates and reproductions of paintings are stored in a QuarkXPress document and printed in an EPS file (photo left). Once in this form the calendar page can be opened and edited in Adobe Photoshop, just like any other image file. First it is converted into a grey-scale image to allow all the relevant tonal values to be spread as desired. The second photo shows how the highlights, midtones and shadows are shifted together in the threequarter tone area (marked red). The magic wand tool (red arrow in the third photo) is used to mask, copy and insert the blacklooking image areas as a level in a new file (fourth photo). These are the spots to which the overprint varnish will be applied during hybrid coating. The full-solid gloss UV coating only adheres to the non-spot areas (marked in red). If the spot coating image contains real grey levels it is then stored in Photoshop as a rastered greyscale image, otherwise it can be stored as a linework bitmap. The file is then inserted in the layout program and subsequently output in register as part of the workflow. 58 Process

59 Applications Examples A selection of the products printed on a Rapida 105 six-colour hybrid press at folding-carton and display specialist Hager Papprint in Kirkel, Germany.The press, which came on stream in mid- 2005, prints and coats solid and corrugated board weighing up to 700gsm. Like many other companies that have gone hybrid, Hager Papprint commemorated the press inauguration with an open day, filling its showroom with typical hybrid products and distributing brochures expounding the creative options hybrid technology offers Folding cartons and displays: chromo duplex board the preferred choice Ever since its introduction, hybrid technology has successfully been used to print one-side coated board. Medium-volume chromo duplex board, the preferred choice for folding cartons, is also hybrid-compatible because it has a high inherent gloss. It is heavier than high-volume chromo duplex board, whose ply is not as firmly glazed and is therefore easier to crease, which helps prevent the paper coating from cracking when folded. For more exclusive products it is worth using cast-coated board whose inherent high-gloss surface maximises the gloss delivered in hybrid production. It is not unusual for folding carton and display sheets to be finished with embossed effects, which of course demands a UV coating with the flexibility to accommodate such effects. Roughly a quarter of the 250-odd printing plants with KBA hybrid presses have opted for large-format versions, the most popular models being the Rapida 142 and 162/162a. The Rapida 130a and 205 are still the exception as far as hybrid production is concerned. The Rapida 130a seven- colour hybrid press installed in October 2000 at Wall in Graz, Austria, is exceptional in other ways, too, because it is a twocoater version into the bargain. This multi-hybrid configuration supports the huge diversity of coating options matt, highgloss, pearlised and metallic demanded by clients in the tobacco, confectionery and cosmetics industries. A Rapida 142 with a similar configuration but six colours is in operation at a major German folding-carton and corrugated specialist, STI in Lauterbach. Above: Pioneer hybrid user STI in Lauterbach, Germany, runs hybrid inks on its Rapida 142 six-colour double-coater press to print film-laminated folding cartons. In the photo, STI s Rainer Buchholz (right) discusses possible applications with KBA s Horst Hörning Below: Wall in Graz also combines double coating with hybrid printing, but on a Rapida 130a Jürgen Leopold (2 nd left), managing partner of German packaging printer Leopold, Ludwigsburg, with print production manager Hans-Joachim Gonnermann (r) plus KBA s Marcus Weber (l) and Michael Stürmer at Leopold s first hybrid press, a 15,000sph six-colour Rapida 142 that was installed in 2004 following a string of conventional Rapidas Process

60 Applications Examples Direct offset on corrugated: KBA poster tubes a familiar sight Direct offset with hybrid inks on corrugated board has already moved into the main stream. Perhaps the best-known example, especially at trade fairs, is KBA s ubiquitous poster tube, which is made of G-flute. One of the finer grades of corrugated, G- flute has the virtue of lying flat and cutting cleanly. The coarser the grade of corrugated (eg E- and F-flute), the more highly compressible the blanket must be, with a corresponding change in packing. The key to troublefree printing is to use a top liner and flute of sufficiently high quality and to allow the corrugated plenty of time to acclimatise. Here, more than with chromo duplex board, it is essential to run the UV lamp at its lowest setting, because water evaporates from corrugated faster than from solid board. Labels: a playground for creative types Label printers must be capable of handling a vast variety of designs, so they are more or less predestined to adopt hybrid production technology. They need a press that can be converted effortlessly from applying conventional inks on rough, structured, unbleached stock to applying hybrid inks plus a UV coating on smooth, gloss-coated stock. Special full-solid UV coatings are available that make the labels water-resistant and therefore suitable for bottles and cans. Delicate matt-gloss effects are particularly popular, and hybrid s ability to apply a matt spot varnish in offset register enables some stunning effects to be achieved, even within the relatively narrow confines of a label. Applying a flexible UV coating allows labels to be embossed or finished with stamping foil. Tin-can labels printed and coated on a Rapida 74 six-colour hybrid press are a speciality of LitoGrafia La Nueva Latina in Mexico City US specialist Mainline Printing in Topeka, Kansas, uses hybrid inks plus a UV coating and film lamination to produce collectibles with a refracted or hologram background (Photos: HoopsCollector.com) Paper and board suitable for hybrid production As a rule,gloss-coated paper and board deliver the best results.the glossier the coating applied in the paper mill, the higher the gloss level that can be achieved with a coating applied in the press.which is why uncoated and matt-coated stock (unbleached paper, duplex and substitute chromo board) normally do not come into the question. Secondary criteria include odour emission under UV radiation, and compatibility with finishing processes (creasing, scoring, gluing, embossing, laminating). It is always a good idea to check whether the UV coating is also compatible with these processes. Paper coating method, volume Definition Applications One-side blade, > 12 g/m 2 One-side blade, > 12 g/m 2 One-side blade, > 12 g/m 2 Chromo duplex board, 1.45 m 3 /g min. (GD1) Folding cartons, displays Chromo duplex board, m 3 /g (GD2) Folding cartons, displays Chromo duplex board, 1.3 m 3 /g max. (GD3) Folding cartons, displays One-side blade, > 12 g/m 2 One-side blade, approx. 18 g/m 2 One-side blade, > 20 g/m 2 One-side blade, > 20 g/m 2 One-side cast, > 24 g/m 2 One-side cast, > 24 g/m 2 One-side cast, > 24 g/m 2 Two-side roller, 5-20 g/m 2 Two-side roller, 5-20 g/m 2 Chromo triplex board (GT1, GT2, GT3) Chromo carton (GC1, GC2, GC3) Chromo paper Coated pulp board Cast-coated chromo board (GG1, GG2) Unglazed high-gloss paper Cast-coated pulp board Illustration printing paper Art paper Folding cartons, displays Folding cartons, displays, comm. Commercials, labels Folding cartons, displays Folding cartons, displays Commercials, labels Folding cartons, displays Commercials, illustrated books Commercials, illustrated books Flute type Flute pitch Flute frequency Flute height E-flute (standard) F-flute G-flute N-flute O-flute mm 2.4 mm standard 1.8 mm standard < 1.7 mm approx. 1.4 mm /m 415/m standard 555/m standard > 600/m approx. 700/m mm 0.75 mm standard 0.55 mm standard mm 0.3 mm With blade coating, calcium carbonate is applied by a dip roller, doctored to a fine film by a metering blade, dried and finally polished with rotating brushes. The highest gloss quality is achieved with cast coating,where the coating is polished by an ultra-smooth heated chrome cylinder. Art paper is coated using rollers, either inline in the papermaking machine or offline, depending on the thickness of the coating. Chromo duplex board is based on duplex board,which comprises a woodfree or low-wood top ply,a (highly voluminous) recyclable filler ply and a (generally unprinted) bottom ply,often with an additional ply below the top one to prevent darker fibres from showing through. The three plies in triplex board are made of three different types of fibre,none of them recycled. Chromo board and chromo paper are based on white pigmented stock. Chromo duplex board can also be used if the hybrid printing process is to be followed by lamination onto solid board of any thickness or corrugated of any sort. Because of the flexibility demanded, only single-wall corrugated with fine flutes is suitable for direct offset. If it is to be hybrid coated a top liner of around 200gsm should be added. KBA poster tubes one of the best-known examples of direct hybrid printing and coating on corrugated 60 Process

61 Applications Examples The configuration of the world s first 13-unit B1 sheetfed offset press, a Rapida 105 installed at Ultra Litho in Johannesburg in 2001: 1. mobile sheeter; 2. and 6. five printing units for conventional or hybrid inks; 3. and 7. coaters for aqueous or UV coatings; 4. interdeck IR/hotair/UV dryers; 5. perfector; 8. double delivery extension with IR and hot-air dryers; 9. end-ofpress UV dryer in the delivery Above: Week for week, Industriedruck Dresden prints long runs of glossy magazine covers to tight deadlines Below: The main line of business at Warsaw-based Eldruk one of three KBA hybrid users in Poland is pharmaceutical packaging, though the company also uses its Rapida 105 universal hybrid press to print magazine covers Commercials: high-impact advertising Spot gloss coatings have long been used to enhance the visual impact of promos, illustrated books, book covers, calendars and business reports by highlighting images, logos and lettering etc. Hybrid coating expands the range of effects that can be created to include contrasting matt/gloss and granular/gloss effects. KBA compellingly demonstrated this in its 2005 calendar (see picture and description on page 35 in Inline coating systems ), in which a blend of granular and gloss coatings enables the viewer not just to see the brush-strokes and linen structure but to feel them as well. This effect would have been impossible to create with the same precision and plasticity on a two-coater press, let alone at such a low cost and with such a short makeready. Benteli Hallwag Druckerei (BHD), a Swiss print provider in Wabern, near Bern, is aiming to exploit hybrid s coating options in order to raise the stakes in the high-end market in which it is a prominent player. According to managing director Martin Brawand this was one reason why, when he first started checking out the possibilities, he soon discarded a long configuration in favour of a Rapida 105 six-colour with a standard hybrid configuration. At the beginning of 2005, PressR3 in Almenno San Bartolomeo (Italy) pressed the button on a highly automated Rapida 105 six-colour hybrid press, which it uses to print advertising brochures, illustrated books, posters, solid board and corrugated displays and exclusive branded carrier bags. In this case the press is being promoted more as a means of delivering upmarket products entailing sophisticated finishing, rather than specialised commercials or packaging. Magazines: special-effect covers Competition for shelf space is as ferocious in the packaging industry as it is in the publishing trade. The ability to deliver glossy covers is thus an effective tool for addressing a high-potential niche market. In late 2004 German magazine printer Industriedruck Dresden, for example, installed a Rapida 105 five-colour to print covers for high-volume titles such as Gala. Any printer wishing to follow its example could do no better than to install an 18,000sph new-generation hybrid press, which supports a far broader product spectrum than a pure UV press with its limited, single-process repertoire. Towards the end of 2001 the world s first 13-unit medium-format sheetfed offset press, a Rapida 105, went live at a leading South African print enterprise, Ultra Litho in Johannesburg. The press is freely convertible between ten colours straight plus single-sided coating and five over five plus perfect coating. The challenge in designing this particular configuration, which was the brainchild of Ultra Litho s production director Hans Kieslich, lay in ensuring that the recto side (with either conventional inks plus aqueous coating or hybrid inks plus UV coating) is sufficiently dry prior to perfecting. This problem was solved by fitting interdeck IR, thermal air and UV dryers before the perfecting unit. Ultra Litho uses the press to print covers for business reports and magazines, even running conventional and hybrid inks in the same pass to deliver covers with a highgloss coating on the outside and an aqueous protective coating or (to match the content) a matt coating on the inside. Grafica Artistica Meridionale (GAM), in Roccapiemonte near Salerno, makes luxury hybrid-coated advertising brochures which manufacturers of tin cans in southern Italy use to great effect to promote regional specialities. In addition to the brochures GAM also prints some 18,000 different label designs for bottles and tin cans Process

62 Applications Examples Plastic film: with selected materials Printers of plastic film have found that polypropylene and polystyrene film are compatible with hybrid inks. Ultraprint Impressora, a commercial printer in São Paulo, Brazil, operates two Rapida 105s and one Rapida 74, which alternate between hybrid production with a UV coating on plastic film and conventional production with an aqueous coating on paper and board. One of the company s main lines of business is plastic giveaways such as bagged or boxed cards and tags for insertion in packaged goods. A Rapida 142 six-colour hybrid press at Ivy Hill Packaging in Louisville, Kentucky, prints various kinds of plastic film. However, as is customary in the US, the hybrid inks used more closely resemble UV inks. Hybrid technology is not yet sufficiently advanced to support print production on PVC. Ink manufacturers are not pursuing this avenue because pure UV inks are already available for this application. A German printer, Berle:druck in Kaarst, is pursuing Coating compatibility its own methods for boosting flexibility. Its Rapida 74 fivecolour coater press has a UV as well as a hybrid capability. Alongside UV inks for the reverse side of lenticular films it can also apply hybrid and conventional inks. An interesting option developed by US printer Curtis Packaging in Sandy Hook, Connecticut, for its Rapida 130a is CurtCHROME, a unique process entailing the inline application of a metallic ink to simulate a metal coating on plastic film or board. This can be followed by a transparent coating, up to eight different colours and a final coating. A lot of hybrid users have successfully printed and coated genuine metallic substrates such as aluminium-coated plastic film or foil-laminated paper and board. One such specialist application is printing on special-effect foils, ie shimmering refractor or microembossed hologram foil capable of incorporating customised design features. Mainline Printing, a commercial and label printer in Topeka, Kansas, has evolved into one of the leading specialist printers in Coating specifications were a major topic at the second KBA hybrid user meeting.the compatibility of UV coatings with hybrid inks, for example, was just one of several issues discussed in depth. Others included the overprint varnish (OVP) used to create contrasting gloss effects. Since UV radiation in the end-of-press dryer tends to cause yellowing OVP only retains its original colour when dried by oxidation such effects must be created without applying spot varnish to a white substrate.coating manufacturers are unlikely to roll out a UV-resistant OVP any time soon.however, some adventurous hybrid users have been busy experimenting and have already come up with non-yellowing formulas. Cured UV coatings are sensitive to heat, which can cause them to crack, so it is best to avoid using hotmelt glue.omitting glued areas when printing folding cartons will not solve the problem because the entire carton is heated as it passes through the dryers. The water-resistance of certain UV coatings is what appeals to printers of drinks labels. There are even special coatings that are actually washable, but their hybrid compatibility has yet to be tested. There are also special coatings that can be applied to offset inks. Normal UV coatings can only be applied to solvent-based inks using silkscreen. Are aqueous metallic coatings and UV coatings compatible? Dryer manufacturers warn that reflection off the metal particles can reduce the amount of UVC radiation that reaches the UV coating. While results with gold have been satisfactory, a less problematical alternative is to use pearlescent pigments instead of metallic ones. MetalStar UV-coatable hybrid inks manufactured by Eckart are available in the US. With hybrid presses, of course, it is also possible to apply an aqueous metallic-effect coating to conventional inks. the expanding market for memorabilia and collectibles such as cards featuring sports stars. Mainline Printing prints both the cards and their fancy boxes on two Rapida 105 universal presses. KBA provided intensive support in addressing the technological challenges posed by the need to apply as many as ten colours plus a UV coating to the metallic background of the image. An ingenious patented process that entails no intermediate carrier is used to laminate the specialeffect foil onto the board or plastic substrate prior to impression. As is often the case in card printing, a transparent film is laminated onto the UV coating following impression. Around 100 cards can be stamped out of a mediumformat sheet. Brand protection: concealed images A major focus of the 9th symposium organised by Mayr-Melnhof Karton (MMK) at KBA in Radebeul in November 2004 was the use of coating as a means of brand protection. The processes discussed included two based on concealed image technology (CIT). One, developed by StarBoard Technologies based in Or Akiva (Israel), enables coded 2-D and 3- D images to be embedded in The three hybrid Rapidas at Ultraprint Impressora in Brazil print plastic film as well as paper homogeneous screen structures. The images can only be decoded and revealed with the relevant key, a dedicated lens. The other process, developed by KBA s sheetfed offset marketing manager Jürgen Veil and his team of process engineers, represents a revolution in CIT. For the first time images can be concealed within full solids, instead of being restricted to screened areas. CIT can therefore be used on packaging printed with a solid process or special colour. This landmark advance was made possible by the ability to apply contrasting transparent coatings an ability inherent in hybrid presses. Dieter Kleeberg In the past, concealed images for brand protection, eg of cosmetic packaging, could only be applied in a raster (top right). Now KBA has developed a process which, for the first time, enables a hidden image to be created on solid black by applying different types of coating 62 Process

63 KBA Process is a sporadic publication created to facilitate strategic investment planning by providing detailed, practical information on the current status and future prospects of new technologies and advances. Koenig & Bauer AG Würzburg Facility Friedrich-Koenig-Str Würzburg Germany Tel: Fax: Web: kba-wuerzburg@kba-print.de Koenig & Bauer AG Frankenthal Facility Johann-Klein-Str Frankenthal Germany Tel: Fax: Web: kba-frankenthal@kba-print.de Koenig & Bauer AG Radebeul Facility Friedrich-List-Str Radebeul Germany Tel: Fax: Web: office@kba-planeta.de KBA-Metronic AG Benzstr Veitshöchheim Germany Tel: Fax: Web: info@kba-metronic.com Publications to date: KBA Process no.1 Focus on Direct Offset on Corrugated (2002) KBA Process no. 2 Waterless and Keyless (2005) Publisher: KBA Group ( Editors: Jürgen Veil Klaus Schmidt Dieter Kleeberg KBA, sheetfed offset marketing manager responsible for the content (veil@kba-planeta.de) KBA, marketing director (klaus.schmidt@kba-print.de) (Kleeberg & Stein), trade journalist, PR service provider to the print industry (kleeberg.stein@t-online.de) Authors: Simon Bornfleth (Day International/Varn Products) Detlef Braun (Druck & Beratung/EWPA) Georg Fritz (Day International/Varn Products) Dieter Kleeberg (Kleeberg & Stein) Dr Bernd Küter (Berufsgenossenschaft Druck und Papierverarbeitung) Norbert Lenzgeiger(Epple) Dr Axel Mayer (Berufsgenossenschaft Druck und Papierverarbeitung) Dr Wolfgang Rauh (Fogra) Dr Roland Reichenberger (KBA) Alexander Schiller (Fogra) Albert Uhlemayr (Vegra) Jürgen Veil (KBA) Christoph Weinert (Schneidersöhne) Layout: Margret Hillmann (KBA) Translation: Christina Degens-Kupp (KBA) Product specifications and features may be changed without prior notice. No part of this publication may be reproduced in any way without the publisher s permission and source data. Although registered trademarks, copyrighted and patented products are not specified as such, this does not mean that they are, or may be treated as, public domain. If you wish to receive our free customer magazine, KBA Report, and are not yet a subscriber, please contact Anja Enders in the marketing department: anja.enders@kba-print.de Tel: Fax: Printed in the Federal Republic of Germany Process

64 People & Print KBA hybrid technology Brilliant money-saver A KBA hybrid press saves you money right down the line. 20% on space and running costs compared to a two-coater press. Much less waste. Plus ultra-short makeready and production times into the bargain. But one thing it never skimps on is quality, which is nothing short of brilliant. Interested? Give us a call. KBA.P.326 e Koenig & Bauer AG, Radebeul Facility (near Dresden) phone: (+49) , office@kba-planeta.de,