Computer-to-Plate (CTP) Technology

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Computer-to-Plate (CTP) Technology

3 August 2018

With a rather broad brush, we cover major elements in the evolution of CTP
from its inception.
The transition of imaging from film to plate has at its core the evolution
of laser technology. There are a variety of factors that influence the use of
laser technology in CTP equipment. These factors include laser type, power,
design, life, operating cost, and plate sensitivity. We address each of these
in separate sub-sections. We alsoaddress corresponding evolution in
plate technology.
We summarize the pros and cons of the two dominant technologies in
the market.
In this section, we present an objective measurement of the productivity
of various platesetters on the market.
This section attempts to provide insight into the evolution of product
development by the major players in the U.S. marketplace. This section in
particular should prove useful in clarifying the various and often confusing
product lines offered by platesetter manufacturers.
We address some of the common tactics and policies of the major equipment
manufacturers in their sale and support of platesetters and related peripherals.

CTP engineering evolved from computer-to-film (CTF) imagesetter technology,
which was predominantly internal drum. In this design, the media is
vacuumed to the internal surface of the drum and exposed by a laser
beam reflectedby a mirror (or mirrors) mounted on a high speed spinner
motor. The laser is positioned a considerable distance fromthe media and
moves across it to expose the image. Because of this distance, a sensitive
media emulsion isrequired for the system to function. When this design was
incorporated into CTP equipment, the most viable laser was a 532 nanometer
(nm) YAG green laser. Other available lasers were the 633 nm red and the
488 nm blue gas lasers. The most viable media was silver-based plate, which
could be exposed by all three laser types. Internal drum construction,
utilizing a single laser diode, was the technology of choice in the mid 1990s,
when CTP technology first began to emerge. Most early entrants into the
CTP market, such as Agfa, Autologic, Cymbolic Sciences, Purup, and Western
Litho, chose the 532 nm YAG laser, following the lead of Creo, who
pioneered CTP technology with their 3244 Platesetter. Competitors such as
Barco (which later became part of Esko Graphics) and ECRM chose the
488 nm blue gas laser. History proved the choice of the blue laser to be a
mistake, primarily because of its high failure rate, often in less than
1,000 hours.

A few manufacturers also offered equipment with the
633 nm red laser, since this laser was well accepted and understood in CTF
technology.From these primitive laser technologies evolved violet laser diode
technology, which is used in almost all internal drum-based CTP equipment
today. The violet diodes cost less than the blue and green lasers, and can
also be used in a more user-friendly yellow safe-light environment.
Although the majority of early CTP devices were based on internal drum
design, several manufacturers took a different approach: Creo and Scitex
initially, joined soon thereafter by Screen. These companies recognized the
limitations inherent in internal drum technology for imaging directly to plate
emulsions.Rather than using the traditional internal drum technology,
these pioneers developed external drum recordersbearing an 830 nm
infrared laser. In this design, the media is clamped to the external surface
of the drum, which allows for mounting of the laser a few centimeters from
the media. Mounting the laser closer to the plate, combined with the
design of a powerful laser source with multiple laser diodes, created the
ability to expose what is known today as thermal plates. The use of thermal
plates eliminated the need for a darkroom or safelight environment.
In addition, the thermal plates had the advantage of durability for print
runs of upwards of a million if baked. The external drum approach also had
its roots in film imagesetting devices. External drum imagesetters were
being marketed by Screen and also by Orbotech, a lesser known Israeli
manufacturer of very large format imagesetters. Behind the scenes of these
two manufacturers lay Creo, a little known company at the time. In the
1980s and early 1990s, Creo was a major supplier of components to these
manufacturers. Creo held the patents and supplied to Orbotech nearly all of
the major components for its external drum recorders, and supplied similar
components to Screen. Creo did not, however, design and manufacture
actual imagesetters, which placed it in the unique position of having
advanced imaging technology but with little vested interest in CTF.
Creo was the first to come out with a thermal external drum platesetter,
introducing their pioneering Trendsetter at Graph Expo in October 1995.
The first production models shipped to customers in Spring of 1996.
Since Screen had experience manufacturing external drum imagesetters,
one would have expected them tohave been an early leader in the
application of this technology to the imaging of plates. Surprisingly,
this is not thecase. Screen’s original efforts to produce a CTP device, in 1996,
were based upon a flatbed design. It is possible thatthe patents owned by
Creo on external drum technology prevented Screen from initially pursuing
an external drumdevice. Whatever the reason, it was not until late 1998
that Screen began shipping the external drum-based PlateRite
(PT-R) 8000.With the introduction of the PT-R platesetter, Screen quickly
made major inroads in the CTP market. The mechanisms and electronics
to achieve the mounting of film to an external drum, although reliable,
were extremely

complex and undoubtedly more costly to manufacture than the mainstream
internal drum imagesetter. Since Screen had already perfected the
manufacture of external drum technology for its imagesetters, this
experience gave the company a competitive advantage when it became
clear that this technology would capture an expanded market that
could not accept their initial flatbed design or the internal drum design of
other manufacturers Scitex, who focused on internal drum imagesetters,
originally introduced the internal drum Doplate 800 platesetter along with
a flatbed platesetter in 1996. However, neither product was successful,
and Scitex quickly abandoned both models in favor of the external drum
design, introducing their first Lotem by the middle of 1997.The external
drum devices of all three manufacturers quickly became widely accepted
in the marketplace. Creo at first was the dominant player, but Screen’s
offerings eventually became the most widely used because of OEM
agreements. Heideberg, Agfa, and Fuji were at a competitive disadvantage
with Creo, Scitex, and Screen, as they didnot have an external drum
thermal platesetter to offer the market. Realizing that any attempt to
“reinvent the wheel”, at least in the short term, was senseless, these
manufacturers turned to OEM agreements. Until these manufacturers
had the ability to develop their own viable external drum platesetters,
they purchased proven Screen platesetters and re-badged them as their
own. Heidelberg at first marketed Creo Trendsetters, but then switched to
offering Screen PTRsafter their agreement with Creo dissolved. Agfa and
Fuji both offered Screen PT-Rs under their brand names.Heidelberg has
since developed their own external drum thermal platesetters and has
discontinued marketing Screen PT-Rs. Agfa developed a thermal external
drum platesetter of their own design the Xcalibur/Avalon series. However,
they continued marketing 4-up PT-Rs under their Accento brand. On
January 29, 2008, Agfa announced the closure of its production facility
for thermal external drum platesetters. At this time, Agfa also announced
future plans for extending their offering of the PT-R line to the 8 up and VLF
models, which were not previously part of their product offerings since
they would conflict with their Avalon series of platesetters. Fuji, rather than
create its own thermal platesetter at a very high cost, continues to offer
the Screen PT-R platesetters, along with internal drum violet machines of
their own design. Because of widespread market acceptance of the PT-R
and because of these OEM agreements, Screen is now the number one
manufacturer of platesetters worldwide

The visionaries of the late 1980s and early 1990s determined that film-based
imagesetting equipment had matured to such a level that the basic design
principles could be adapted to imaging directly to plates. The key ingredient
missing in that era was an affordable laser with the power necessary to
image the less sensitive emulsion of the plates available at the time.
CTP technology progressed as advances were made in both laser
technology and plate technology, which generally progress in unison.
Lasers are usually described by platesetter manufacturers according to their
position on the color spectrum. The spectrum is measured in nanometers
(nm). Each laser color requires a plate with an emulsion that is sensitive to
that particular laser wavelength. Below is a chronological listing of lasers
used in CTP equipment, along with corresponding technological advances
in available plates.
CTP Lasers nm Color
360-450 Ultraviolet
405-410 Violet
488 Blue
532 Green (YAG)
633-670 Red
830 Infrared – thermal
1064 Infrared (YAG) – thermal
Chronological Introduction
Year nm Technology Applications
1994 532 Green Very early Creo 3244 platesetter, Cymbolic
Sciences Platejet, Agfa Galileo.
1994 488 Blue Gas laser tubes used in the Barco Crescents and the
ECRM AIR 75. This technology is completely obsolete because
of the unreliable nature of these lasers.
1995 1064 Infrared The thermal 1064 nm laser represents a doubling
of the 532 nm green laser and was used in internal drum
machines. This technology has been replaced by external
drum platesetters with 830 nm lasers. The 1064 nm laser is
completely obsolete.
1995 360-450 Ultraviolet Technically
not a laser, this is a UV light source that is used to expose
conventional plates. This technology was pioneered by
basysPrint. Other manufacturers have attempted
to create competitive equipment to expose conventional
plates, but until Lüscher’s entry into this market in 2006,
only basysPrint had widespread acceptance. Lüscher is now
offering serious competition to basysPrint in this market.
1996-8 830 Infrared Thermal – Pioneered by Creo, Scitex, and Screen,
and now the standard laser wavelength in all thermal platesetters.

Year nm Technology Applications
2000 633-670 Visible Red VR diode – Generally found as an option for
ECRM platesetters. The red laser diode never found wide
acceptance and is no longer used in current production
2000 405-410 Violet Silver-based – Introduced at Drupa 2000, violet
technology was well received as an alternative to green
lasers. Violet sensitive plates can be handled in user
friendly yellow safelight conditions. Violet lasers also cost
less than green and thermal lasers. All early offerings of
this laser were for use with silver-based plates.
2000 830 Processless Ablative (thermal) – Presstek pioneered
specialized plates that can be imaged by thermal lasers and
that do not require chemical processing. Presstek’s plates
are imaged by an ablative process, in which the laser
erodes the emulsion, creating a dust that must then be
removed from the machine’s interior. This requires a device
to vacuum the dust out of the system. However, even
with this device, regular cleaning of the machine interior
is essential. Recent innovations have created processless
plates that do not require chemical development and do
not use an ablative process for imaging.
2002 405-410 Violet Photopolymer – Photopolymer plate requires a
more powerful laser than the original 5 milliwatt (mW)
violet laser that most manufacturers used when violet
platesetters were first introduced. Generally, these plates
require at least a 30 mW laser for exposure. Depending
upon the architecture of the platesetter and the sensitivity
of the plate being used, a 60 mW laser may be required.
There is no silver content in photopolymer plates,
eliminating the need to deal with this pollutant.
Photopolymer plates are also cleaner than silver plates
and require less processor maintenance.
2005 830 Chemical Free Non-ablative (thermal) – At Graph Expo 2005,
Agfa introduced their Azura plate. This plate is technically
classified as “chemistry-free”, since it requires processing
with a gumming solution prior to printing. The Azura plates
have an advantage over the Kodak and Fuji true
“processless” plates in that there is a clear visible image
on the plate prior to mounting on the press.
2006 830 Processless Non-ablative (thermal) – Plates requiring no
processing prior to mounting on the press are currently
offered by Kodak and Fuji. The primary difference
between thetwo offerings is the sensitivity of the emulsion.
Kodak’s plates require 300 mJper cm2 of laser power