Thermal Plates -- The Heat is OnOctober 2000
In addition to the need to bake some thermal plates to achieve longer runs, some printers were reluctant to use thermal CTP because of the cost of the plates themselves. Actual prices vary considerably depending upon the relationships printers have with plate suppliers, but some printers have cited substantial cost premiums over the cost of conventional CTP plates.
New Plates, Opportunities
It was at DRUPA 1995 that Eastman Kodak announced its first thermal plate, the Thermal Printing Plate/830—the same plate now distributed by Kodak Polychrome Graphics. Kodak Polychrome Graphics has a large share of the thermal plate market and intends to maintain its market share. To that end, the company announced continued dedication to thermal in pre-DRUPA announcements and demonstrated six different thermal plates at the trade show.
Today, though, it is not the only major printing equipment and supplies vendor with an interest in a share of the thermal plate market. Agfa, Fuji, Presstek and Printing Developments (PDI) are each continuing to expand their line of thermal plate offerings. Other companies such as Anacoil Corp. and Lastra America are also getting into the game.
The current visible versus thermal CTP debate is simply a continuation of the old internal versus external drum debate of four or five years ago, contends John O'Rourke, product manager, consumables, at Presstek. "Literally all of the proponents of visible light imaging for CTP are vendors that offer internal-drum CTP hardware exclusively. It's clear that a format debate is vendor-driven. Since a CTP imaging system represents a substantial investment for most printers, any consideration of format should be based on features, benefits and value—not the interest of one vendor or another."
He notes that thermal imaging offers daylight handling and enables ablative processes. "Ablation offers the only path to chemistry-free and true process-free plate systems. These benefits, coupled with the inherent higher image quality of thermal imaging, meet the printers' needs today and into the future."
It's a daunting task to sort through all of the thermal plate products to find the one or two plates that work best on your system. But more players in the game means more competition, and that should mean lower plate prices soon. According to Leigh Kimmelman, product manager, output products, for CreoScitex, "With so many different vendors in the market now, the price for thermal plates should come down. I believe it will not be long before it is close to that of conventional."
One of the other attractive advantages of thermal over conventional CTP was the promise of plates that required little or no processing. Today, as opposed to five years ago, this promise is now a reality; many plate vendors are offering processless or reduced processing plates, including PDI and Presstek.
Plate manufacturers understand that printers, faced with manpower shortages and the need to cut costs, like the idea of processless plates—plates that require no chemical processing before they can be used on-press. So, they are taking steps to ensure that even when some handling is required before the plates are ready to be used on-press (such as a quick wash to remove excess plating particles), the steps and resources required are minimal.
They are also employing new technologies in their attempts to create more and better processless plates. These technologies hold great promise; within a few years printers could have a much wider range of choices in processless plates. There are several technologies used for creating processless plates, including thermal ablation and bi-metal technology.
Ablation technology plates start with an aluminum layer coated with an ink-receptive layer covered by an infrared-absorbent layer. The top layer (infrared) acts as a primer for the final top coat of PVA or silicon (PVA for dry, silicon for wet printing). The platesetter laser ablates (cuts) the infrared layer to remove the ink-receptive layer below.
Some thermal ablative plates require a quick wash off before or on the press to remove debris after the ablation process is complete. Others can be used without this step, but they require water on the press. With these plates, the washout is done using a fountain solution when the plates have been put on-press.
Bi-metal technology, used by PDI, involves placing a photopolymer layer on top of a thin layer of copper that sits on top of a thin layer of aluminum or stainless steel base. After the plate is exposed to the heat in the platesetter, the developing process removes the copper in the non-imaging areas. In the last development step the polymer stencil is dissolved and removed. The result is a plate with press dot sizes that are the same as the original film.
Plate manufacturers are experimenting with several other kinds of techniques involving phase changes and chemical coatings. The concept is to trigger a physical or chemical change to a substrate to make the plate ink-receptive.
There are two approaches to phase change plates, and both involve a special coating on a metal plate. The first is a thermally alterable coating applied to an aluminum base. On-press, the unimaged layer is removed by a fountain solution to reveal the water receptive aluminum layer. The second is to use a special coating on a metal plate. After being exposed in the thermal platesetter, the plate changes from being water-receptive to ink-receptive.
The Future of Thermal
What does the future hold for thermal plate technology and which, if any, of the technologies currently in use will be used in the future?
Dave Bartram, worldwide marketing manager for CTP at Kodak Polychrome Graphics, gives a tantalizing glimpse of the long-term future. "Our definition of the goal [for a thermal plate] is to have a plate that generates no debris nor requires rinsing or development on-press. There is nothing on the market today that fits that description."
Bartram could not comment on how soon Kodak Polychrome Graphics, or any other plate manufacturer, would be able to reach the goal of a totally processless plate. He did say, though, that research in the company labs is on-going and progress is being made.
Phase-change technology may well be the foundation of the technology that allows printers to have hands-off, totally processless plates within the next five to 10 years. In the meantime, ablation looks like the technology leader for processless thermal plates. Bartram says that Kodak Polychrome Graphics is committed to fully commercializing the technology. That is likely to be the case with the other plate manufacturers currently using the technology. So, ablation—a proven, tested technology—looks as though it will be around for years to come.
Longer term, it is a sure bet that plate manufacturers will continue to pursue the goal of a plate that can be imaged without human intervention. The need for a plate that works well in a direct-to-press scenario is too great, as are the potential profits for plate manufacturers that can solve this technological puzzle.
Making the Choice
There are several ways printers can solve their own puzzle of which plates to use on which platesetter. The first is testing—getting enough of the plates you're considering, and testing them on your own platesetter and on your presses. There is no substitute for this step in the evaluation process.
Once you've determined that the plate works, you'll want to consider direct costs (cost of the plate and costs of any and all processing). You'll also want to consider any indirect costs, such as the cost for purchasing and operating a processing or baking unit. Make sure to take into account any additional costs or cost savings you might encounter by making changes in your workflow.
You will also want to take into consideration recommendations made by the platesetter manufacturer. The technology involved in CTP and digital plates is still at the stage where you need to pay attention to what the equipment manufacturers have to say. There is little, sometimes no, room for mix-and-matching between platesetters and plates.
In a short five years, thermal plate technology and manufacturing have come a long way. Today, printers have many solid products to consider and more are no doubt on the way. Some of the product choices offer reduced processing time and costs. Printers interested in thermal CTP need to consider more than the per plate costs associated with thermal. Having real numbers in hand can help make decisions easier and more realistic.
Thermal plates also have a bright future; new technologies are being developed to further reduce or eliminate processing. Plus, as the printing industry moves forward to direct-to-press technology, thermal plates will play a role in getting the industry to this goal.
Who's Offering What in Thermal Plates
Mistral—a waterless, processless plate based on thermal ablative technology, is suitable for high run lengths.
Thermolite—conventional aluminum substrate with a thermally sensitive coating on top, developed on-press, suitable for short run, on- and off-press thermal imaging.
Themostar—a thermal plate with no pre-baking requirements with run lengths up to 500,000.
830T-Plate is a digital, positive plate for CreoScitex thermal platesetters; run lengths of up to 150,000, more with post-baking.
Brillia LH-PI—a medium-run, positive working thermal plate; run lengths up to 300,000.
Brillia LH-NI—an IR laser-sensitive, negative working, long-run thermal plate for runs of 1 million impressions or more.
Kodak Polychrome Graphics
Thermal No Process—currently in beta testing, this plate requires no chemical processing, can be exposed digitally on a thermal external or internal drum equipped with a debris-removal/filtration system; suitable for runs up to 50,000.
Thermal Printing Plate/830—uses the thermal ablation technology and is suitable for runs up to 250,000. With post-baking, the run lengths go up into the millions.
Thermal Waterless Plate—a wet process plate for waterless printing with run lengths up to 100,000.
ProTherm P3000 (was announced at Graph Expo)—a successor to the Electra 830; run lengths up to 200,000, with post-baking run lengths in the millions.
ThermalNews—a thermal plate for the newspaper market with run lengths of 250,000.
Extrema 830.2G—photopolymer thermal plate, certified for use with CreoScitex thermal platesetters; rated up to 100,000 impressions without post-baking and up to 1 million with post-baking.
Prisma 830 CTP—uses bimetal technology consisting of a layer of copper on top of a layer of aluminum coated with an infrared-sensitive polymer. Created for use with CreoScitex thermal platesetters; run lengths of up to 2 million. No pre-heat or post-baking required.
Anthem—wet offset thermal plate with run lengths of 100,000; no chemical processing or pre- or post-baking.
PearlGold—for dampening-equipped presses.
PearlDry—for waterless printing; suitable for run lengths up to 100,000.
CTP Thermal Waterless Plate Thermal LD—830nm.
Thermal Versus Visible Light
With all the advantages of using thermal plates—better print quality, lower consumables usage and the promise of processless plate making—it's natural to ask the question of why you would use conventional computer-to-plate systems. There are platesetter vendors, such as Agfa, that offer both thermal and CTP systems, and feel strongly that both are valuable. Then there are companies such as CreoScitex that claim, while conventional still has a role today, thermal is key to the future of CTP.
Steve Musselman, senior worldwide marketing manager, commercial printing segment, at Agfa, explains his company's thinking on thermal versus visible light. "As Agfa sees the market, the demand for thermal platesetters and plates versus visible-light solutions will be roughly 50/50 within the next two years. Putting this in perspective, these solutions combined represent about 10 percent of today's total plate volume relative to conventional plates."
So, the question arises, according to Musselman, over where each solution has its best fit. "Many factors influence the decision, but one differential factor is run length. Taking the U.S. market as an example, only 1 percent of press runs are for more than 250,000 impressions, and only 9 percent of the sites ever need a plate that runs more than 200,000 impressions." For these extra long-run requirements, he agrees that thermal is a good fit, since with baking, most thermal plates can run more than 1 million impressions.
"Since DRUPA, we have been seeing more alternatives to thermal—as in high-quality, long run-length thermal ablative plates such as Agfa's Mistral. Agfa has also previewed its ThermoLite plate, which is non-ablative, and activates on-press," he adds. At Graph Expo, Agfa showed its spray-on emulsion called LiteSpeed—a derivative of ThermoLite. LiteSpeed was shown as part of a technology demonstration on the Creo-Scitex SP process. LiteSpeed is Agfa's spray-on, instant-drying, fusible thermoplastic that, according to Musselman, has wide lithographic characteristics.
"So, as one evaluates visible light versus thermal, it seems that thermal is finding applications at both ends of the printer's requirements, whereas visible light is a good fit for the more than 90 percent of the requirements of the general commercial printer, without some of the thermal technology and processing overhead," he concludes.
Leigh Kimmelman, product manager at CreoScitex, says thermal has significant advantages over conventional CTP, including better print quality and greater consistency across the length of a print run. He also likes the fact that thermal is moving processless—meaning no chemical waste and no instability in processing due to the use of chemicals. Eliminating processing steps allows the user to create a plate in under five minutes.
He also favors the use of thermal for digital printing. "Thermal is easier for digital presses because the plates can be handled in white light or near-white light conditions. You can also use thermal plates to do on-engine proofing as you can do on the Trendsetter or Lotem platesetters. The advantage of on-engine proofing is that the screening algorithms for the proof and the print are the same."