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w w w. k b a - p r i n t . c o m
Issue 1/2006
3
PRODUCTS | PRACTICES | PERSPECTIVES
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
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.
KBA
Editorial
2
Inks and coatings
Drying
KBA dryers
Choosing the right system
Adhesion
Test methods
3
6
10
11
14
UV technology
Lamps
Compatible consumables
Blankets and washes
Paper specifications
Hybrid ink specifications
Coating specifications
15
18
22
24
26
28
Gloss coating
Gloss
Offline coating
Inline coating
30
31
32
Hybrid technology
Retrospect
Fogra test
Cost-efficiency
Waterless hybrid inks
36
39
44
47
Environment
Emission testing
Alcohol-free dampening
49
51
Handling
Benefits and tips
53
Applications
Pressroom examples
58
Contacts
Resources/partners
63
29
Product No.:
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Quality enhancement
with hybrid production
Contents
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Combining hybrid inks, overprint varnishes and UV coatings in sheetfed offset
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 technolo-
2 Process 3 | 2006
Albrecht Bolza-Schünemann, president and CEO, Koenig & Bauer AG
gies. 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,
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 3 | 2006 3
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.
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
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.
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
Absorption of binder
IR radiation, possibly thermal radiation
Evaporation of volatile mineral oils in binder
Thermal, flotation or IR radiation
Conventional and hybrid inks (in conjunction with oxidation) for absorbent substrates; conventional and
waterless coldset inks dry by penetration only
Heatset inks; waterless offset inks for printing plastic
Evaporation of volatile base fluid
Thermal radiation (modular, flotation, impact jet dryer);
thermal fixation
Thermal or possibly IR radiation
Solvent-based inks (gravure, screen, pad, flexo), coatings (offline) and toners (ink-jet); liquid toner (HP
indigo/Toyo ElectroInk)
Water-based (aqueous) coatings, inks (flexo, gravure) and toners (thermal ink-jet)
Physical process:
Evaporation of high-boiling base fluid
Precipitation of binding agent and absorption of solvent Moisture in substrate, steam application
with moisture
Resolidification of melted or evaporated wax
Room temperature; thermal fixation
Moisture- or steam-set corrugated print production
Phase-change ink sticks for ink-jet; ink-bearing films for thermal sublimation; dry and liquid toner
Chemical process:
Oxidative polymerisation of binder
Polymerisation of acrylic binder through decomposition
of photoinitiators into radicals
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
Continuous UV radiation, excimers (flexo only), possibly in Radical UV-cured inks and coatings for sheetfed, heatset and narrow-web offset, screen, flexo and gravure,
inert nitrogen atmosphere
offline coating; hybrid inks for sheetfed offset; waterless UV offset inks for plastic film, cards, CDs and
narrow-web presses (labels, packaging)
Polymerisation of epoxy binder through cations released Pulsed UV radiation or IR radiation
Cationic UV-cured inks and coatings for sheetfed offset, narrow-web flexo/offset; dual-cure inks for sheetfed
by photoinitiators
offset
Polymerisation of acrylic binder through splitting
Electron beams rendered inert in nitrogen atmosphere EB-cured inks and coatings for sheetfed offset, narrow-web offset and flexo
of radicals
Polymerisation, polyaddition or polycondensation of two Possible addition of solvent, depending on reaction
Two-component and plastic inks for screen printing
binder components
mechanism
4 Process 3 | 2006
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
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.
What you should know about hybrid 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 3 | 2006 5
Drying and curing | KBA systems
Innovative, highperformance dryers
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
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 pos-
UV
IR+TA
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
sible 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 AdPhosEltosch, Grafix and IST Metz.
Turn to page 7
Continued from page 5
Additives for fine-tuning
Complex demands
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.
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.
6 Process 3 | 2006
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.
Dieter Kleeberg
Drying and curing | KBA systems
Standard KBA hybrid press and optional extras
1
3
1
1
1
1
6
P
5
4
2
2
4
1 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 105
6 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
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 (400 - 500W/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.
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
Process 3 | 2006 7
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 (59 - 94.5µin). 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.
Twin-tube carbon IR – a new dryer
generation
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
8 Process 3 | 2006
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.
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 3 | 2006 9
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)
Rapida+D+DE(2), Rapida hybrid, Rapida 74 G+C+DE(2)
and 74 Karat+C+D
—
Oxidising/penetrating
Oil-based overprint* (spot) Drip-off or dual-effect aqueous
(full-solid)
Paper, carton, corrugated
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* Special UV (full-solid)
(spot)
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 3 | 2006
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
Aqueous coating alone and with UV
coating
no more energy than absolutely necessary.
Ink must adhere
to the substrate
Oil-based overprint varnish and UV
coating in hybrid production
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 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
tainly the better choice for anyone printing gloss contrasts on a
regular basis.
matt. Though very good, the
results do not approach the standard of a UV matt coating.
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 cer-
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).
What is draw-back?
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 3 | 2006 11
Inks and coatings | Interaction
Overcoming interfacial tension to improve wetting and spreading
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.
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
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.
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
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
12 Process 3 | 2006
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)
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
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
Dieter Kleeberg
coating.
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 coaters, anilox rollers and coating formes
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.
Structure
ART
ART
ART/TIF
ART/TIF
Frequency
120 lpc
120 lpc
100 lpc
100 - 80 lpc
Angling
45°
45°
45°/75°
45°/75°
Pick-up
9 cm3/m2
13 cm3/m2
16 to 20 cm3/m2
18 to 22 cm3/m2
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.
Anilox roller?
UV and aqueous coating on paper up to 170 gsm
UV and aqueous coating on carton
Aqueous coating for high gloss
UV coating for high gloss
Process 3 | 2006 13
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
14 Process 3 | 2006
or 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
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.
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
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 stamping-
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)
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.
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
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
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)
380 - 315 nm
Penetrates thick layers of ink and coating
Skin ageing, rapid tanning
UVB (medium wave)
315 - 280 nm
Supports radical polymerisation
Sunburn, permanent tan
UVC (short wave)
280 - 100 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’)
400 - 200 nm
Active range; triggers and supports polymerisation
400/300 nm ‘near U’V, 300/200 nm ‘far UV’
UV-2 (‘vacuum UV’)
200 - 100 nm
Passive range; feeds active range through wavelength drift towards UV-1
—
Process 3 | 2006 15
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-
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-
Energy emission of a UV lamp
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/cm2 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.
16 Process 3 | 2006
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
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
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
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.
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
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
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 2002. For film printers,
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
How a cold mirror functions
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
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.
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 3 | 2006 17
UV technology | Rollers, blankets, plates, paper
Resistance of consumables to UV
radiation during hybrid coating
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
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.
Blankets suitable for hybrid production (August 2005)
Blanket
Applications
Substrates
Strippable?
Atécé
PrintCare SF-A
PrintCare SP/SS/N
PrintStrip R606
Böttcher
Conventional or hybrid, UV or UV plus hybrid production Paper, carton, cardboard, plastic, metal
Aqueous or UV coating
Paper, carton, cardboard, plastic, metal
Aqueous or UV coating
Paper, carton
no
yes
yes
TOP 1001/1002/1003
TOP 4400
TOP 5400-N
Contitech, Phoenix Xtra Print
Aqueous or UV coating
Paper, carton, cardboard, plastic, metal
Conventional or hybrid, UV or UV plus hybrid production Paper, carton, metal
Conventional or hybrid, UV or UV plus hybrid production Metal (with UV also paper, carton)
yes ( 0.7/0.8/0.8 mm max.)
no
no
Conti-Air Ebony
Conti-Air Spectral
Phoenix Ruby Carat
Phoenix Topaz Carat
Phoenix Opal/Canyon
Day International, Day Brasil
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
Paper, metal
Paper
Paper, carton
Paper, carton, cardboard, metal
Paper, carton, cardboard, plastic, metal
no
yes
no
no
yes (approx. 0.9 mm)
davidM QL Stripper
dayGraphica 3610/EU 03
dayGraphica NSP 03
Printec max
Printec coater/stick ’n’ strip
Duco, Birkan
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
Paper, carton, cardboard, plastic, metal
Paper, carton, cardboard
Carton, cardboard, plastic, metal
Paper, carton, cardboard
Paper, carton, cardboard, plastic, metal
yes
no
no
no
yes (0.8 mm max.)
Multi Hybrid
Superflex
Superstrip FB/FB longer run
Superstrip PB/UVPB
Superstrip SB Adhesive
TR Turquoise
UV Compressible EPDM
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
Corrugated board
Paper, carton, cardboard, plastic, metal
Paper, carton, cardboard, plastic, metal
Paper, carton, cardboard, plastic, metal
Paper
Paper, carton, plastic, metal
no
no
yes ( 0.8 mm max.)
yes (0.95/0.8 mm max.)
yes
no
no
Aqueous or UV coating
Paper, carton, cardboard, plastic, metal
yes
Folex
Folacoat UV LT-D/LT-P
Fujikura Graphics
Luminus
Conventional or hybrid, UV or UV plus hybrid production Paper, carton
no
Conventional or hybrid, UV or UV plus hybrid production Paper, plastic, metal
no
Conventional or hybrid, UV or UV plus hybrid production Paper
no
Aqueous or UV coating
Paper, carton, cardboard, plastic, metal
Conventional or hybrid, UV or UV plus hybrid production Carton, cardboard, plastic, metal
yes
no
Conventional or hybrid, UV or UV plus hybrid production Paper, metal
Conventional or hybrid production
Carton, cardboard, metal
no
no
Conventional or hybrid, UV or UV plus hybrid production Paper, carton, metal
Conventional or hybrid, UV or UV plus hybrid production Paper
Conventional or hybrid, UV or UV plus hybrid production Paper, carton
no
no
no
I.M.C.
Perfect Dot 4-SR
Kinyo
Airtack M Adhesive
MacDermid (formerly Rollin)
Elastostrip
Metro
Prisco
Priscolith Ebony
Priscolith Hybrid
Reeves
Vulcan Combo
Vulcan Folio
Vulcan Image4U
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.
18 Process 3 | 2006
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 3 | 2006 19
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
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
Yes
Yes
Yes
Yes
N/a
N/a
N/a
2000 mm
830 T-Plate
Positive, thermal
Wet
Commercials
Yes
N/a
Negative, thermal
Wet
Commercials, packaging
Yes
N/a
Brillia LH-PCE/PSE
Brillia LH-PIE/PJ
Brillia LP-N3
Brillia LP-NV
VPS-E/VPL-E
VPU
Huaguang (KPG licence)
Positive, thermal
Positive, thermal
Negative, argon or Fd:YAG
Negative, violet
Positive, UV (analogue or CTcP)
Positive, UV (analogue or CTcP)
Preheat, wet
Preheat, wet
Preheat, wet
Preheat, wet
Wet
Wet
Commercials
Commercials
Commercials
Commercials
Commercials, packaging
Commercials, packaging
Yes
No
Yes
No
Yes
No
2050 mm
2050 mm
1230 mm
1230 mm
N/a
N/a
TN
TP
Negative, thermal
Positive, thermal
Wet
Wet
Commercials, packaging
Commercials, packaging
Yes
Yes
N/a
N/a
Positive, thermal
Wet
Commercials
Yes
N/a
Arte IP-21
Positive, thermal
Eco 88
Positive, UV (analogue or CTcP)
Rubi T-50
Positive, thermal
Kodak Graphic Communications Group (formerly Creo)
Wet
Wet
Wet
Commercials, packaging
Commercials, packaging
Commercials, packaging
Yes
Yes
Yes
N/a
N/a
N/a
Mirus PN
Negative, thermal or UV (an./CTcP)
Wet
Commercials, packaging
No, but possible
2080 mm
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
No, but possible
No (waterless offset)
1560 mm
N/a
N/a
1512 mm
1512 mm
N/a
Duros HST
Positive, thermal
Wet
Commercials
Yes
N/a
Positive, thermal
Negative, violet
Positive, UV (analogue or CTcP)
Wet
Wet
Wet
Commercials
Commercials
Commercials, packaging
No, but possible
Yes
Yes
1660 mm
N/a
N/a
Positive, thermal
Wet
Commercials, packaging
No (bimetal base)
N/a
Anthem
Saverio Rief
Positive, thermal
processless
Commercials
No
1118 mm
Therma
Positive, thermal or UV (an./CTcP)
Wet
Commercials
Yes
1660 mm
Cobra
Negative, thermal or UV (an./CTcP)
Preheat, wet
Commercials, packaging
Yes
1500 mm
TechNova
Gemini Plus
Taurus
Thermostar TN (Agfa P970)
Toray
Positive, UV (analogue or CTcP)
Positive, UV (analogue or CTcP)
Positive, thermal
Wet
Wet
Wet
Commercials
Commercials, packaging
Commercials
Yes
Yes
Yes
1030 mm
N/a
N/a
Negative, thermal
Negative, analogue UV
Positive, analogue UV
Wet
Wet
Wet
Commercials, packaging
Commercials, packaging
Commercials, packaging
No (waterless offset)
No (waterless offset)
No (waterless offset)
1610 mm
1610 mm
1610 mm
Positive, UV (analogue or CTcP)
Positive, UV (analogue or CTcP)
Wet
Wet
Commercials, packaging
Commercials, packaging
Yes
Yes
N/a
N/a
Agfa-Gevaert
First Graphics (Kodak)
FGN
Fuji Photo Film
Indústria Brasileira de Filmes
IBF-Million 2
Ipagsa
Kodak Polychrome Graphics
Lastra (Agfa-Gevaert)
LT2
LVX
Futura Oro
PDI
Prisma 830/Steel 830
Presstek
Southern Lithoplate
Waterless TAC-RG5/RL7
Waterless TAN-E
Waterless TAPD-G1/H-G2
Verona Lastre
VELA LPN-100/LPV-100
VELA Universal
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 advis-
20 Process 3 | 2006
able to check the maximum stencil depth, which is defined by a
stripping barrier beneath the top
layer. If the coating blanket is to
be re-used, blanket manufacturers recommend clamping it on
fairly tightly with a torque
wrench. Printing pressure should
be set as light as possible to allow
UV technology | Rollers, blankets, plates, paper
the coating to spread evenly on
the substrate.
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 coat-
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).
References (left) and substrate samples
(right) during the Robinson test
(Photos: M-real)
Inks for hybrid production (November 2005)
Manufacturer
Ink series
Comments
Arets Graphics
EXC Process Hybrid
Not recommended, too aggressive (UV properties)
Eckart America
MetalStar Hybrid
Metallic ink for final printing unit, not yet tested
Epple
Starbrite
KBA/Fogra-accredited
Gans Ink & Supply
OS UV-Hybrid 4-Color Process
Not yet tested
Huber Group
Hostmann-St. Reflecta Hybrid
Modification recommended after Fogra test
Jänecke+Schneemann Supra UV Hybrid
KBA/Fogra-accredited
Sicolor
Sico Brite
KBA/Fogra-accredited
Sun Chemical/DIC
Sun Cure Hy-Bryte/Daicure Hy-Bryte KBA/Fogra-accredited
Sun Chemical
Sun Cure Hy-Bryte Max
Like Sun Cure Hy-Bryte, but not yet accredited
Toyo Ink
FD Hybrid Aqualess SOY
Waterless offset ink, passed KBA tests
Toyo Ink
FD Hybrid Eco-SOY
Not yet tested
Unionprint
VersaCure
Not yet tested
Van Son
Quickson UV Coatable
Not yet tested
Xsys Print Solutions Flint-Schmidt Gemini Process
KBA/Fogra-accredited
Xsys Print Solutions K+E Novabryte BF Process
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.
ing 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 3 | 2006 21
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
DayGraphica 3610: the standard blanket for
hybrid production
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.
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, dayGraphica EU 03 and dayGraphica
NSP 03.
22 Process 3 | 2006
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, dayGraphica 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
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
Rubber base of face compound
DayGraphica blanket
Varn wash
Nitrile butadiene rubber (NBR)
3610, EU 03
V60+ wash, AIII Hydro-Solv
Rubber base of face compound
DayGraphica blanket
Varn wash
Nitrile/PVC compound
NSP 03
AIII Hydro-Solv Hybrid-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
Hybrid inks
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,
Pure UV inks
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 com-
pounds (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 HydroSolv 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 3 | 2006 23
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.
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
24 Process 3 | 2006
Gloss test charts and other prints created using hybrid inks and coatings
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 elas-
tic (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
UV technology | Resistance of rollers, blankets, plates, paper
agents may well prove necessary
in order to achieve a satisfactory
impression.
Paper under a raster electron microscope
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.
Surface of a glossy coated paper
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
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.
Interaction in hybrid applications
Various interactions have also
been observed between the substrate and the other process components during hybrid applica-
Surface of a matt coated paper
tions. 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.
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
www.schneidersoehne.de
For further information please contact the author on +49 2236 606-237,
[email protected]
Process 3 | 2006 25
UV technology | Hybrid inks
Specifications for
hybrid inks
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.
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;
26 Process 3 | 2006
The Starbrite product range also includes washes and overprint varnishes
• 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.
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 tempera-
specially formulated for hybrid inks.
95
90
85
80
75
70
70% 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)
ture, 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
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.
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 1.40 .
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
Results of tests with hybrid inks:
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
1.5
1.0
0
The gas chromatographic analysis revealed that the concentration of aldehyde (in mg/m3) 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 3 | 2006 27
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
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
28 Process 3 | 2006
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
“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
2003.Vegra has promoted hybrid coating
right from the start
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.
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
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
(www.bgdp.de)
•Fogra Forschungsgesellschaft Druck e.V., D-Munich (www.fogra.org)
Blankets
•Birkan Drucktechnik GmbH, D-Eching am Ammersee
(www.birkan.de, www.duco.co.uk)
•Day International GmbH, D-Reutlingen (www.day-intl.com)
•Phoenix Xtra Print GmbH, D-Hamburg (www.pxp.de,
www.contiair.com)
Plates
Inks and coatings
•Epple Druckfarben AG, D-Neusäss (www.epple-druckfarben.de)
•Flint-Schmidt GmbH & Co KG, D-Frankfurt/M (www.flint-schmidt.de)
•Huber Group/Hostmann-Steinberg GmbH, D-Celle (www.mhm.de,
www.hostmann-steinberg.de)
•Jänecke+Schneemann Druckfarben GmbH, D-Hannover
(www.js-druckfarben.de)
•Schmid Rhyner AG Print Finishing, CH-Adliswil (www.schmid-rhyner.ch)
•Sicolor GmbH, D-Neusäss (www.sicolor.de)
•SunChemical Hartmann Druckfarben GmbH, D-Frankfurt/M
(www.sunchemical.com)
•Terra Lacke GmbH, D-Lehrte (www.terralacke.de)
•Toyo Ink Co. Ltd., J-Tokyo
•Vegra GmbH, D-Aschau am Inn (www.vegra.de)
•Weilburger Graphics GmbH, D-Gerhardshofen
(www.weilburger-graphics.de)
•Xsys Print Solutions Deutschland GmbH, D-Stuttgart
(www.xsys-printsolutions.com)
Washes
•Varn Products GmbH, D-Reutlingen (www.day-intl.com)
•DC DruckChemie, D-Ammerbuch (www.druckchemie.com)
•DS Druckerei Service, D-Reutlingen (www.dsgroup.de,
www.fujihunt.com)
•Vegra GmbH, D-Aschau am Inn (www.vegra.de)
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
www.vegra.com.
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/m2, which is
equivalent to a pick-up volume by
the anilox roller of 15g/m2. 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 fol-
•Kodak Polychrome Graphics, D-Osterode (www.kpgraphics.com)
•Rudolf Reproflex GmbH, D-Goslar (www.rudolf-reproflex.de)
•Xsys Print Solutions Deutschland, D-Stuttgart
(www.xsys-printsolutions.com)
Rollers
•Felix Böttcher GmbH & Co. KG, D-Cologne (www.boettcher.de)
•Praxair Surface Technologies, D-Schlüchtern (www.praxair.com)
Dryers
•Adphos Eltosch Torsten Schmidt GmbH, D-Norderstedt
(www.adphos.de, www.eltosch.de)
•Grafix GmbH Zerstäubungstechnik, D-Stuttgart (www.grafix-online.de)
•Dr. Hönle AG UV Technology, D-Gräfelfing (www.hoenle.de)
•IST Metz GmbH, D-Nürtingen (www.ist-uv.com)
•RadTech Europe, NL-Den Haag (www.radtech-europe.com)
Substrates
•M-real Technical Sales and Marketing, D-Hamburg (www.m-real.com)
•Schneidersöhne Group, D-Ettlingen
(www.schneidersoehne.de)
•UPM-Kymmene Sales GmbH, D-Hamburg (www.upm-kymmene.com)
lowing 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 (www.isega.de) 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 17025 in a number of languages including
English, French and German; in 1990 it also started certifying packaging manufacturers’
hygiene management systems
Process 3 | 2006 29
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
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
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 16537 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.
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.
UV matt coating on hybrid inks
R = 10 - 20
UV matt coating on UV inks
R = 20
Inks (depending on substrate)
R = 30 - 50
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 = 65 - 85
80
UV gloss coating on UV inks
R = 85 - 90
75
UV gloss coating on hybrid inks
R = 85 - 95
Offline UV coating on dry ink
R = 90 - 98
Test results for hybrid coating
Gloss measured immediately and after 72 hours
100
95
90
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
30 Process 3 | 2006
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
85
70
65
MK 70%
140%
CM 70%
140%
CMY 70%
210%
MK 100%
200%
Measured immediately, 10,000 sph
Measured immediately, 12,000 sph
CM 100%
200%
CMYK 70%
280%
CMY 100%
300%
CMYK 100%
400%
unprinted
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.
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
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
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
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 3 | 2006 31
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 2005.
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
Maximum gloss level 60
None
Aqueous (solid)
Oxidative/penetrative
Wet-on-wet in printing unit with uncoated Thin coating film, slightly thicker with slip-in doctor blade (not
aluminium plate and blanket
offered by KBA, as problematical without IR/thermal air dryer)
None
Dampening duct (solid)
Oxidative/penetrative
Wet-on-wet in dampener with uncoated
aluminium plate and blanket
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 Flexo coater and double delivery extension with IR/UV dryer for
dried OPV in coater
hybrid mode on hybrid presses; max. gloss 95, optimum gloss
contrasts
One
OPV (spot) + drip-off/twin-effect Oxidative/penetrative or hybrid
aqueous (solid)
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**)
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
Oxidative/penetrative
(solid**) + UV (solid**)
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
Oxidative/penetrative
*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 3 | 2006
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.
L30 Combi Circulator (left) and X10
Conditioner – two components in Tresu’s
automated dual-circuit pumping system
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 underly-
ing 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
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 3 | 2006 33
Gloss coating | Inline
Ceramic reverse-angle and doctoring
blades following eleven weeks of
production at 8,000sph
(Photos: Praxair)
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.
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:
• a UV coating to be applied to
conventional inks, though only
indirectly following inline sealing of the ink film with a layer
of aqueous coating
• a wide range of imaginative
effects to be created by apply-
ing 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
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
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
Cleaning processes for anilox rollers
Process, aids
Automatic washing unit integrated in coating feed system
Comments
Time-variable washing programs for all coating components; virtually no manual cleaning; very fast
Cleaning mat
Used in place of or on coating blanket, has a fulling effect; recommended by Praxair
Steel brush
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
Ultrasound
Roller must be removed; improper usage can damage ceramic; relatively expensive
Blasting with
- sodium bicarbonate
- carbon dioxide (dry ice)
- plastic pellets
Roller must be removed; improper usage can damage ceramic; relatively expensive
IR laser
Recommended for an anilox roller screen of 300lpc or finer; roller must be removed; improper usage can
damage ceramic; relatively expensive
34 Process 3 | 2006
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.
Gloss coating | Inline
Coating needs planning
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 360053 on 170gsm
GardaMatt supplied by Cartiere del Garda
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
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.
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
• a simple 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 3 | 2006 35
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 250plus 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
1999. 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 2000. 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
2004. 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/m3
500 mg/m3
substantially lower
substantially lower
Ink mist
under discussion
untraceable
Ozone
0.2 mg/m3
substantially lower
UV radiation
as per prEN 1010-2
substantially lower
Powder
6 mg/m3
(1.5 mg/m3 under discussion)
84 dB (A)
substantially lower
Noise
36 Process 3 | 2006
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 2000
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 3 | 2006 37
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
38 Process 3 | 2006
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 2002.
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.
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
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.
Regular demonstrations of hybrid technology, like this one for a group of Italian print
professionals, are held in KBA’s Radebeul showroom
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 (11/2 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 53521 test regime
German roller manufacturer
Felix Böttcher in Cologne provided samples of the three rubber
compounds used in its inking and
dampening rollers:
M1: 17925 for ink forme rollers,
M2: 47940 for ink vibrators,
M3: 22022 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 53521 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/m2 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 3 | 2006 39
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 2005. 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%)
9
8
7
6
5
4
3
2
1
0
9
8
7
6
5
4
3
2
1
0
40 Process 3 | 2006
8
7
6
5
4
3
2
1
0
-1
Black
M2
M3
M1
A
B
C
D
E
F
M2
M1 M3
B
C
D
E
M2
F
M3
M1
A
9
8
7
6
5
4
3
2
1
0
Yellow
A
Magenta
B
C
D
E
F
Cyan
M2
M1
M3
A
B
C
D
E
F
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%)
9
8
7
6
5
4
3
2
1
0
9
8
7
6
5
4
3
2
1
0
8
7
6
5
4
3
2
1
0
-1
Black
M2
M3
M1
A
B
C
D
E
F
M2
M1 M3
B
C
D
E
M2
F
M3
M1
A
9
8
7
6
5
4
3
2
1
0
Yellow
A
Magenta
B
C
D
E
F
Cyan
M2
M1 M3
A
B
C
D
E
F
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)
A
B
C
D
E
F
A
0
0
-1
-1
C
D
E
F
M3
M3
-2
B
-2
M1
-3
M1
-4
-5
-3
-5
Black
Magenta
-6
-6
0
M2
-4
M2
A
B
C
D
E
F
0
A
B
C
D
E
F
M3
-1
-1
M1
M1
-2
-2
-3
-3
-4
-5
-6
M2
Yellow
M3
-4
-5
Cyan
M2
-6
Process 3 | 2006 41
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)
0.10
0.10
Black
0.08
0.08
0.06
0.06
0.04
0.04
0.02
0.02
0
123456
0
-0.02
-0.02
A
B
C
D
E
F
Yellow
0.10
0.10
0.08
0.08
0.06
0.06
0.04
0.04
0.02
0.02
0
123456
Magenta
123456
A
B
C
D
E
F
Cyan
0
123456
-0.02
-0.02
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)
0.10
0.10
Black
0.08
0.08
0.06
0.06
0.04
0.04
0.02
0.02
0
123456
0
-0.02
-0.02
A
0.10
B
C
D
E
F
0.10
Yellow
0.08
0.08
0.06
0.06
0.04
0.04
0.02
0.02
0
123456
123456
A
B
C
D
E
F
Cyan
0
123456
-0.02
-0.02
A
42 Process 3 | 2006
Magenta
B
C
D
E
F
A
B
C
D
E
F
Hybrid technology | Accreditation
credit
c
A
id P
ybr r
For H
d
e
Product No.:
ing
int .
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)
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).
The KBA/Fogra seal of approval includes a
space for the product name and number
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%)
80
80
70
A
60
60
50
K
40
M
50
YC
30
20
20
10
10
0
W2
W3
W4
W5
W6
C
W2
D
50
50
40
30
W5
W6
C
Y
30
Y
20
W4
40
C
KM
W3
KM
70
60
20
10
10
0
0
W1
70
C
K
W1
80
60
80
Y
0
W1
70
M
40
30
80
B
70
W2
W3
W4
W5
W1
W6
80
E
W2
W3
W4
K
W5
W6
C
Y
50
MY
40
M
60
C
K
50
W6
F
70
60
W5
40
30
30
20
20
10
10
0
W1
W2
W3
W4
W5
W6
0
W1
W2
W3
W4
Process 3 | 2006 43
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 (271/2 x
391/2in);
• 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
44 Process 3 | 2006
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;
Comparison of three coater configurations
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
T
8+9
7
7
10 10 10
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)
1+9
H
10 10 10
4
4
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
1+3 1+2 1+2 1+2 1+2 1+2
UV
6
4
5
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
5
5
4
Hybrid technology | Cost-efficiency
T
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 160m2
(1,722ft2), compared to just
135m2 (1,453ft2) for a hybrid
press. The effective saving is thus
approximately 15%.
120%
100%
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
4%
8%
8%
4%
140%
140%
16%
120%
60%
88%
88%
65%
27%
27%
27%
40%
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)
25%
6.6%
18%
18%
55%
55%
0
60%
40%
62%
6.6%
133%
66%
66%
20%
20%
D
80%
80%
20%
0
15%
1.1%
6.6%
2.9%
100%
60%
40%
A glance at the cost of consumables for the three processes (see
27%
100%
88%
Cost of consumables:
up to 60% higher with two-coater
press
160%
120%
80%
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.
160%
180%
8%
23%
Initial investment cost:
20% higher for two-coater press
than for hybrid press
D
H
UV
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
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 3 | 2006 45
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.
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
140%
120%
D 122 %
D 119.2 %
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
186 euros
97
67
58
53
48
D 142.1 % D 140 %
D
138
% D 136.9 % D 136.2 %
140%
D 135.4 %
H UV
H UV
100%
H UV
H UV
H UV
H UV
H UV
H UV
100%
D 85.8%
D 85.8%
80%
80%
60%
60%
40%
40%
20%
20%
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%)
46 Process 3 | 2006
Dr Roland Reichenberger
120%
H UV
H UV
0
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.
0
2000
5000
10000
15000
20000
30000
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
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-
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.
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, 45478 Mülheim an der Ruhr,
Germany. Tel: +49 208 594482-10,
Fax: -12, www.wluv.de).
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.
The outlook
The ink that was used, FD Hybrid
Aqualess Soy M supplied by Jap-
Process 3 | 2006 47
Hybrid technology | Waterless offset
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)
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 5mm2/m2 (0.0007in2/ft2). This compared with
around 85mm2/m2 (0.01in2/ft2) on UV-printed paper.
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.
48 Process 3 | 2006
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
Rheological and thermal properties of waterless hybrid inks
Parameter
FDHB Aqualess SOY M
FDHB Aqualess SOY L
Tack at 30°C
11.0 - 13.0
9.0 - 11.0
Flow at 25°C
16.0 - 17.0
17.0 - 19.0
Dynamic viscosity at 25°C
70 - 80 Pa s
50 - 60 Pa s
Recommended plate temperature 28 - 32 °C
24 - 28 °C
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 1980. 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 2004.
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 compli-
ance 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 3 | 2006 49
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/m3,
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
50 Process 3 | 2006
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
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.
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 solu-
tion 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
(www.fogra.org) as part of a service
package which includes practical training in applying the test chart, and basic
on-site press setting by Fogra personnel.
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
Process 3 | 2006 51
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, FountGreen is the compatible concentrate.
haved in much the same way as
hybrid ink 1 (graphs 5 and 6).
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, be-
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 proce-
dure 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 3 | 2006
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.
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.
A touch-screen is essential at the console for
the hybrid Rapida (Photo: Kleeberg)
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.
days. Customers could be offered
a price incentive to support this
cost-saving regime by delivering
their data within the relevant
deadline.
Flexibility: exploit it efficiently
Kodak Polychrome Graphics’ Excel plates are used for hybrid production on the presses in
KBA’s showroom in Radebeul
Hybrid production accounts for
30% to 70% of output by the 250odd 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
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.
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 3 | 2006 53
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
54 Process 3 | 2006
Hybrid inks are also available in cartridges, which is the form Industriedruck Dresden prefers
for its hybrid Rapida 105
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)
The aluminium anilox roller developed by KBA for the coater is so light that it can be changed
without a hoist
Handling | Benefits and practical tips
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 press-
es. 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.
Suction air paths in the Air Clean System
Process 3 | 2006 55
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 feasi-
56 Process 3 | 2006
ble 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!
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 equip-
ment 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
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
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 3 | 2006 57
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
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
58 Process 3 | 2006
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.
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.
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 mid2005, 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 sur-
face 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 (2nd 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 3 | 2006 59
Applications | Examples
Direct offset on corrugated:
KBA poster tubes a familiar sight
Labels:
a playground for creative types
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, Gflute has the virtue of lying flat
and cutting cleanly. The coarser
the grade of corrugated (eg Eand 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.
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
One-side blade, > 12 g/m2
One-side blade, > 12 g/m2
One-side blade, > 12 g/m2
One-side blade, > 12 g/m2
One-side blade, approx. 18 g/m2
One-side blade, > 20 g/m2
One-side blade, > 20 g/m2
One-side cast, > 24 g/m2
One-side cast, > 24 g/m2
One-side cast, > 24 g/m2
Two-side roller, 5-20 g/m2
Two-side roller, 5-20 g/m2
Applications
Chromo duplex board, 1.45 m3/g min. (GD1) Folding cartons, displays
Chromo duplex board, 1.3-1.45 m3/g (GD2) Folding cartons, displays
Chromo duplex board, 1.3 m3/g max. (GD3) Folding cartons, displays
Chromo triplex board (GT1, GT2, GT3)
Folding cartons, displays
Chromo carton (GC1, GC2, GC3)
Folding cartons,displays,comm.
Chromo paper
Commercials, labels
Coated pulp board
Folding cartons, displays
Cast-coated chromo board (GG1, GG2)
Folding cartons, displays
Unglazed high-gloss paper
Commercials, labels
Cast-coated pulp board
Folding cartons, displays
Illustration printing paper
Commercials, illustrated books
Art paper
Commercials, illustrated books
Flute type
Flute pitch
Flute frequency
Flute height
E-flute (standard)
F-flute
G-flute
N-flute
O-flute
3.0 - 3.5 mm
2.4 mm standard
1.8 mm standard
< 1.7 mm
approx. 1.4 mm
283 - 333/m
415/m standard
555/m standard
> 600/m
approx. 700/m
1.0 - 1.8 mm
0.75 mm standard
0.55 mm standard
0.5 - 0.55 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.
60 Process 3 | 2006
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
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
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)
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
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 3 | 2006 61
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
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 compatibility
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.
62 Process 3 | 2006
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 3D 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
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. 4
97080 Würzburg
Germany
Tel: +49 931 909-0
Fax: +49 931 909-4101
Web: www.kba-print.com
E-mail: [email protected]
Koenig & Bauer AG
Frankenthal Facility
Johann-Klein-Str. 1
67227 Frankenthal
Germany
Tel: +49 6233 873-3371
Fax: +49 6233 873-3222
Web: www.kba-print.com
E-mail: [email protected]
Koenig & Bauer AG
Radebeul Facility
Friedrich-List-Str. 47-49
01445 Radebeul
Germany
Tel: +49 351 833-0
Fax: +49 351 833-1001
Web: www.kba-print.com
E-mail: [email protected]
KBA-Metronic AG
Benzstr. 11
97209 Veitshöchheim
Germany
Tel: +49 931 9085-0
Fax: +49 931 9085-100
Web: www.kba-metronic.com
E-mail: [email protected]
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
(www.kba-print.com)
Editors:
Jürgen Veil
Klaus Schmidt
Dieter Kleeberg
KBA, sheetfed offset marketing manager responsible for the content ([email protected])
KBA, marketing director
([email protected])
(Kleeberg & Stein), trade journalist, PR service
provider to the print industry
([email protected])
Authors:
Simon Bornfleth
Detlef Braun
Georg Fritz
Dieter Kleeberg
Dr Bernd Küter
(Day International/Varn Products)
(Druck & Beratung/EWPA)
(Day International/Varn Products)
(Kleeberg & Stein)
(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:
E-mail: [email protected]
Tel: +49 931 909-4518
Fax:+49 931 909-6015
Printed in the Federal Republic of Germany
Process 3 | 2006 63
People & Print
KBA hybrid technology
Brilliant money-saver
KBA.P.326 e
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.
Koenig & Bauer AG, Radebeul Facility (near Dresden)
phone: (+49) 351 833-2552, e-mail: [email protected], www.kba-print.com
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