Imaging 12 - Fujifilm Graphic Systems

CTP technology – processless plates
T
he processless metal litho
plate has been one of those
long-term dreams of the
printing industry that never
quite turns up in the form you’d expect.
The idea of a plate that you run through a
conventional platesetter, take out and put
straight on to the press seems obvious. It’s
faster (no processing time), ought to be
cheaper (no chemistry to buy), and
environmentally better (no chemistry to
dispose of). But it’s proving frustratingly
elusive to achieve. The more plate
developers look into it, the more they
appreciate the benefits of good old
chemical development – and they’re
doubtless aware that no-process also
means a loss of revenue from chemistry.
Over the years plenty of developers
have announced no-process plates and
some are actually in production today, but
so far none have offered a complete
replacement for conventional chemicallydeveloped
plates. The main processless
metal plates currently in full production
are all intended for on-press imaging in
digital presses.
Current predictions suggest that a noprocess
plate may have a higher total cost
than a conventionally processed plate plus
chemistry, which sounds back-to-front. It’s
all a matter of tolerances – a conventional
(non-CTP) plate gives very high yields off
the production line because it can exhibit
relatively wide production tolerances and
still work perfectly on the press. A
chemically-developed CTP plate has
somewhat lower yields due to more finicky
tolerance requirements, which is why it
costs more (though competitive pressure
and steadily increasing production
capacity is driving this down). A noprocess
plate has much narrower
tolerances, so yields will be smaller and
prices significantly higher. The basic
economics of processless don’t yet add up,
even if manufacturers feel ready to swing
into full-scale production.
Derek Wyse, MD of consultancy
Vantage Strategic Marketing, who
specialises in printing plate technical and
market analysis, is sceptical about the
economic prospects of processless plates
in the general commercial market, saying,
“We think it will appeal mainly to the twoand
four-page press user market, because
of the costs of equipment.” He believes
that conventional UV-sensitive offset
plates exposed by dedicated platesetters
are the way ahead for larger formats: the
16 Imaging 12 autumn 2002
plate production costs, chemistry and onpress
behaviour are all likely to remain
more favourable than exotic no-process
systems, he predicts.
Paths to process-free
There are five main technological paths
available to plate manufacturers seeking
the processless grail – and you can be sure
that all the manufacturers will be trying
out all these processes and more.
The earliest and so far most widely
used technology is thermal ablation, where
a powerful laser blasts a coating away
from the non-image areas of the plate.
This is the process used on the waterless
digital litho presses and it works with both
metal and polyester plates. The snag is
that the ablation process generates debris
– ash or dust burned away by the lasers –
which is bad news in a precision optical
device like a platesetter. On-press imagers
have vacuum extractors and filters on the
heads. A few platesetters are offered with
vacuum ‘debris management’ options, but
so far off-press thermal ablation has found
relatively few buyers. Also, there’s only
one plate supplier, which contributes to
making printers nervous.
Switchable polymer plates are seen by
several manufacturers as the ideal for the
future, though there’s nothing on the
market yet. The coating covers the whole
plate and there’s no need for an expensive
graining process. The laser imager is used
to alter the plate coating so it switches
from water-receptive (non-image) to
water-repellent (image). Creo is experimenting
with a spray-on switchable
coating that can be applied on or offpress
to re-usable metal plates: other
manufacturers are profoundly sceptical
that it can be kept dust-free. In any case,
it seems like a retrograde step, back to the
days before pre-sensitised litho plates
revolutionised offset printing in the 1970s.
MAN Roland uses the unique
DICOtape process on its DICOweb digital
web offset press. Here the energy from a
thermal laser is used to transfer an inkreceptive
coating from a ribbon of foil
material onto bare stainless steel cylinders.
After printing, the ‘plate’ cylinders can be
scrubbed bare and re-imaged.
Inkjets seem to be a promising area in
the longer term. Here a modified printer
sprays ink-receptive coating onto bare
metal plates, which then go through a
chemical hardening process (UV-cured
inks will probably be suitable in future).