Direct-to Plating

In the beginning there was silver, and it was good—for CTP. Silver's sensitivity made it the perfect fit for low-powered argon ion lasers of a decade ago. Next came processless thermal ablative plates. Now these silver and ablative technologies compete with low- and no-process polymer plates.

Four-up printshops have discovered polyester plates, joining the small-format crowd in appreciation of this high-quality option. Capable of resolving 2400-dpi details just like silver-diffusion plates, they feature a silver halide coating that requires chemical processing. North American sales of non-metal platesetters will rise 9.5% through 2010, in addition to the practice of converting old film imagesetters to polyester platemaking.

Mitsubishi Imaging sells both Silver DigiPlate material and compatible platesetters. Its SDP-Eco1630III platesetter offers a self-contained, two-bath processor. The activator and stabilizer have been redesigned for Mitsubishi's Eco process, drastically reducing chemical consumption. Other silver-emulsion polyester plates include Agfa (SetPrint), Heidelberg (Cristala Quickplate Silver) and Presstek/AB Dick (MegaPro).

Presstek and its AB Dick unit helped define small-format CTP. The ABDick Freedom 25,000-run aluminum plate and its Vector 52 thermal platesetter (with integrated plate washer) is touted as “the lowest priced chemistry-free thermal CTP plates on the market.”

Processless CTP began more than 15 years ago, when Presstek's first thermal platesetter and ablative plates shook up the industry, featuring a hydrophylic top layer that is vaporized with thermal energy to reveal the oleophillic layer below. Presstek's chemistry-free line-up includes the new 100,000-impression Anthem Pro and 50,000-impression Aurora plates, in addition to the niche PearlDry for waterless runs. Thermal ablative Aurora is compatible with most thermal platesetters, including Kodak Trendsetter and Screen PlateRite.

Agfa introduced the first “violet” printing plate in 2000 based on a silver-halide emulsion tuned to visible light exposure in the violet range (400-430 nanometers). At a time when thermal processes had come to dominate CTP, violet platesetters equipped with low-cost, 5-milliwatt laser diodes brought renewed competition to the marketplace. Today, only Agfa, Mitsubishi Paper Mills and Heidelberg market a silver-diffusion plate for the considerable installed base of 5mw violet platesetters. The market potential of “first-generation” violet plates featuring silver emulsions is enhanced even by the popularity of “second-generation” 30+mw laser diode platesetters because they can also operate at the 5mw intensity used for silver emulsions. Chief among these, with over 1,500 installed, is Heidelberg's Prosetter series.

Since the arrival of “aqueous chemistry” for analog platemaking more than two decades ago, polymer plates have become well established. Most CTP plates today are based on similar polymer emulsions, sensitive to either thermal (830-1080 nm) or violet (400-430 nm) light. All these polymer plates use an energy-sensitive emulsion that crosslinks (hardens) to the aluminum after exposure. Non-image areas are removed by a processor, or by the ink train of a press.

“Second-generation” violet photopolymer CTP systems are enabled by violet laser diodes offering the high-output power (30 watts or more) typically required to initiate crosslinking in polymer emulsions; this physical reaction to visible light is signified by the “photo” in photopolymer. Fujifilm's Brillia LP is a family of high-resolution, high-sensitivity photopolymer plates. The plates are available in violet (LP-NV), adapted for use with argon ion and FD-YAG lasers (LP-N3), or for newspaper applications (LP-NN2 and LP-NNV). Still under development is Fujifilm's Brillia HD PRO-V violet photopolymer plate, said to be the industry's first processless violet option. Availability is projected for early 2007. Agfa's :N91V plate is a negative-working photopolymer product for violet platesetters that's already popular in the newspaper industry. The Kodak Violet Print Digital Plate (just launched in the U.S. and Canada) builds on the established success of the Violet News Digital Plate. While both products require a chemical processor with a built-in preheater, users can take comfort in the decade-long positive track record of pre-heating plate processors.

Thermal polymer plates arrived years before the first violet photopolymer products; early thermal polymer systems were easy to recognize due to the omnipresent pre-heat ovens. Fortunately, “ovenless” thermal polymer plates are now available. While there are too many to review individually, any list should include Kodak's no-bake Sword Excel Thermal Plate. It's no easy task to supplant the classic Kodak 830 Thermal plate that accompanied many first-generation Creo Trendsetters back in the 1990s, but the Sword Excel plate has proven itself in numerous high-volume installations.

Fujifilm's Brillia LH-PJ is a positive thermal plate requiring no pre-heat and providing more compatibility with harsh UV chemistry without post baking, and improved scratch resistance.

Announced at Ipex and Graph Expo 2006, Agfa's new N91v ChemFree (only a working title) will utilize a mysterious “photopolymerization” technology. Little has been revealed about this product, but a recently uncovered 1971 Agfa patent defined photopolymerization as “vinyl groups capable of being cross-linked upon exposure to actinic light” (U.S. Patent No. 4001016). “Actinic” is broadly defined as electromagnetic radiation that produce photochemical reactions.”

Now in commercial distribution, Fujifilm's Brillia HD (provisionally known as the PRO-T) is chemistry-free, employing On-Press Development. The non-image emulsion of ODP plates softens after contact with press fountain solution; upon contact with the ink rollers, the plate's unwanted coating is removed with the first few printed sheets. Kodak Thermal Direct Non Process Plate can also be classified as ODP. The technology has also spawned some controversy, as it can be difficult to discern an exposed plate's image before mounting.

ONLINE: www.agfa.com, fujifilmgs.com, graphics.kodak.com, mitsubishiimaging.com, presstek.com and us.heidelberg.com