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Plates: The unsung hero of print!

26 May 2010

Sachin Shardul verifies the print performance of printing plates - including history, technology, chemistry and waste in order to help printers make a more informed choice when purchasing

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I am a printing plates person. That means, I've sold (and serviced) tons of PS plates for a major part of my career. Which is why, I've never found printing plates, dull and irrelevant. In fact for me, plates are a crucial stage in the supply chain - and this includes a print buyer. For example, I always advised a print buyer to ask his printer what pre-press workflow they're using to identify screening and plate combinations. The print buyer said, why is it important? I told him, you do a fair amount of reprints, and if your printer switches workflows in between a print run, the results can be somewhat unpredictable due to different look-up tables and plates and curves and screening "types" and so on.

But in normal circumstances, it is unlikely that print buyers would be involved in specifying a particular type of plate for their work (Imagine a buyer saying: "I think the Fuji HD LH-PIE will work best with the Fedrigoni and metallic black and metallic silver ink on my job"), but printing plates remain a vital link in the production chain so it's helpful for specifiers to be as clued up as possible. "Without plates, we have no job. Their role is taken for granted," says Sanjay Malhotra, chief executive officer at Malhotra Graphics. Bimal Chaku, the  vice president at Malhotra Graphics, adds: "Plates are so critical to the job, they're almost the unsung heroes. And clearly good quality plates are essential to good quality print."

Dish of the day

Quite so, and there's an incredible amount of technology packed into each and everyone of them, from the composition of the "litho-grade" aluminium base to the formulation and application of the coatings and the precision cutting and packing.

Manufacturers such as Agfa, Fujifilm, Kodak and TechNova invest millions of dollars every year in research and development as specialists in white coats fiddle around in laboratories honing plate performance. And when a manufacturer decides to invest in a new plate production line, the scale of investment is enormous - as I witnessed at TechNova's new digital plate line in Taloja, Navi Mumbai.

Today, the array of printing plates available is enormous. For example, TechNova's iCTP technology. I'm a big fan of this technology because of its simplicity. All it requires is a special type of plate that can be imaged on what is essentially a ramped-up version of a normal inkjet printer. The inkjet CTP system images polyester and metal plates as well as polyester films. Commercial printers use PoliJet and MetiJet plates whereas newspaper houses use PosiJet polyester films. PoliJet polyester plates are available up to size 820mm X 1030mm, and require no processing, and are more than adequate for many jobbing print applications including spot colour work. It's a popular option for the mini offset presses and entry-level printers. Interestingly enough, mini offset presses use another innovative product from TechNova, NovaDom, which are laser polyester plates. As Neelkanth Mehta, manager customer service iCTP at TechNova Imaging Systems informs me, "Its very popular among printers who do bookwork." At the other end of the scale, there is the precision manufacturing of huge aluminium plates, each about the size of a kingsize bed, for the latest VLF (very large format) sheetfed and web offset presses.

By and large, printers rely on their print providers to use the right type of printing plate and, whatever the "hype" from plate manufacturers, my experience with printing plates has taught me that a majority of plates used in offset litho, manufactured by the top four manufacturers mentioned earlier, will provide perfectly good results.

But in cases where there are problems, for example, with the reproduction of fine art work or very tiny stochastic/FM screens, or printing with UV inks, then it's worth asking questions about whether the plates and platesetter being used by the printer actually have a specification that is suitable for that type of work. All plate manufacturers provide technical data sheets for their plates that will specify quality aspects such as suitability for line screens up to a maximum, say 200lpi, and the percentage range of dot size that can be held, for example 2%-98%, so it's easy for plate suitability to be checked should problems arise. 

Nowadays, the vast majority of plates are produced directly from digital data using computer-to-plate systems, and the days of pre-press departments fiddling about with the intermediate step of film separations is for the most part a distant memory. Most buyers are already benefiting from the quality and accuracy of print produced with first generation dots on the plate.

Green and clean
So what's next for the not-so-humble printing plate? In common with so many other areas of life in general, the environment is a hot topic, and in recent years manufacturers  have made great strides in increasing the eco-friendliness of plate production, traditionally something that has involved fairly complex chemical processing with all of its attendant hazardous waste and emission issues and high levels of power and water consumption.

As a result, both chemistry-free and processless plates are now becoming available (there's a subtle difference, explained below) that are suitable for both sheetfed and web litho printing. The run-length varies according to the plate manufacturer's specs, typically ranging from  50,000 to 250,000 impressions. Processless plates can't be baked, so for longer print runs extra sets of plates would need to be produced. Chemistry-free plates (e.g. TechNova's VioGreen) can be baked to print upto 500,000 impressions.

As Steve Green, regional managing director Asia Pacific Region at Kodak's Graphic Communications Group, who visited India recently, points out, different criteria are needed for all the different types of print. So if a printer says, ‘I want to go processless', it may not deliver what your print buyer is actually looking for. Not every product suits every market.

Even where processing of plates remains necessary, manufacturers are doing much to reduce their environmental impacts by making plates "developer-free" (e.g. Kodak Thermal Direct, Presstek Aurora Pro, Fuji Brillia HD Pro-T, Agfa and TechNova's Amigo). These plates use solutions for development that are totally free of solvents and are not therefore considered harmful effluents. They require less water and have longer-lasting chemistry.

Printers should be asking this sort of question of their plate suppliers. Are they looking to reduce power use and water use, and reduce waste? This can be the case with both process-free and processed plates, says Padmakar Ojale, country general manager graphic arts at Fujifilm India. For example, not having to bake plates (when plates are pre-heated in an oven as part of the processing stage as in case of violet plates, to make the final plate more robust) is also more environmentally friendly.

"TechNova is committed to working with the printing fraternity to help the printing industry "Go Green" by providing products, roadmaps and hands-on support to to reduce power and water consumption and eliminate harmful effluents and solvent vapour emissions," says Pranav Parikh, managing director of TechNova.

The company has set up a special "Green Group" that offers customised roadmaps to printers to help them reduce their carbon footprint (an indicator of the amount of CO2 emission of their operations on a "cradle-to-grave" basis).

Kodak in Ipex 2010, will launch Trillian SP, a no-preheat thermal plate that reduces chemistry consumption. The plate is claimed to cut chemistry consumption by 70% and is considerd robust on press for long runs. Trillian SP plates are targetted at commercial printers, publishers and offset package printers. The plate lowers the total cost of ownership and provide environmental benefits by using significantly less chemistry and eliminating the use of pre-heat and post-bake ovens, even for long jobs in harsh chemical environment.

Fujifilm has been involved in a big environmental push over the past year as part of the marketing campaign for its processless plate range and this has included a special website  www.howgreenareyourplates.com that lets printers and print specifiers calculate the environmental footprint of different plate options.

Today, talk to any of the plate manufacturers and you realise there's a tremendous amount of work being done on the bigger picture of process stability, which reaps benefits once the plates get to the press in terms of reduced makeready times and wastage, and job repeatability.

As Chandan Naik the director of Transtech, the Nagpur-based company explains: "Once the print run is finished, the used plates remain a valuable commodity - aluminium is an expensive metal to manufacture and is highly desired. So the vast majority of plates are recycled and printers are able to offset the value of the scrap metal against some of their waste costs." According to Naik, the printer can save good deal of money on the plates.  Transtech provides this service of recoated plates for hundreds of printers in India which includes newspapers as well.

The environmental conditions and considerations will play a role and new plate technologies will be unveiled; which means this unsung hero will sing new tunes.


 

PLATES: AT A GLANCE

CHEMISTRY-FREE VS PROCESSLESS
What's the difference? When a plate is truly processless, there is no intermediate step in between the plate being imaged and it being used on the printing press. The plates are effectively ‘developed' on the press during the makeready cycle, when non-image areas are removed as the press runs up. Examples include Kodak Thermal Direct, Presstek Aurora Pro, Fuji Brillia HD Pro-T.  

In the case of chemistry-free plates, after imaging, the non-image areas are removed through a simple application of a gumming solution (either manually or using a simple "Clean-out" unit).  There is no effluent as the gumming solution is recirculated in the clean-out unit. Products such as Agfa's Azura V, Fuji's HD-Pro-V and TechNova's VioGreen CTP plates are classed chemistry-free.

Chemistry-free plates seem to be generally preferred over process-less plate for various reasons. Whilst, process-less plates have limitations like: no contrast, hence mistakes cannot be detected prior to printing; Poor scratch resistance, posing a challenge for automatic loading units on plate cylinders; since the non-image areas are cleaned on the press, there is an inherent risk of contaminating the rollers and press chemicals; the plate is susceptible to mishandling and sensitive to daylight and cannot be stored beyond one hour of exposing, which limits flexibility of print scheduling. On the other hand, chemistry-free plates offer : higher sensitivity ensuring higher through-put per hour - a critical need of newspapers and service-bureaus; lower start-up waste on the press; longer run-length; higher resolution; and more importantly, visible image for plate inspection prior to mounting on the press.

THERMAL VS VIOLET CTP
Plate manufacturers have spent years wrangling about the relative merits of different imaging technologies. Advocates of thermal argue that it is superior because it is essentially a binary process - a laser dot is either exposed or it isn't. However, issues include imaging speed and the cost and lifetime of the high-powered lasers required. Violet CTP uses cheaper mass-market laser diode technology so manufacturers can take advantage on the developments being made in consumer applications. But the violet photopolymer plates don't have the reproduction qualities of thermal (or indeed silver), so aren't suitable for highest quality applications.

However, the controversy regarding thermal vs violet appears to have been set to rest with the introduction of the latest generation of violet platesetters from FFEI (marketed by Fujifilm and TechNova under their own brand names in India), and commercial quality violet plates from Fujifilm and TechNova after Drupa 2008. 

TechNova and Fujifilm claim the latest generation plates are of quality equal to thermal in terms of reproduction, and superior robustness on the press. TechNova claims that its Viostar and VioGreen violet plates can reproduce 10 micron dots when imaged on their Viostar (FFEI) platesetters.
Judging by the market trends, it seems that Indian printers have embraced violet technology over thermal during the last one year.

UV CTP (popularly known as CTcP)
This technology has been around for many years. The appeal of UV CTP or CTcP is that it uses high-speed conventional negative and positive PS plates instead of the expensive thermal and violet plates. The current generation of UV platesetters (made by BasysPrint, Luscher and Cron) are equipped with laser diodes, thereby enhancing the resolution and throughput. However, the image resolution and print quality are not comparable to violet and thermal plates. The plates require processing and chemistry-free versions are not technically feasible.

Due to the very high cost of the UV platesetters, this technology requires high volume of plate consumption per month to break-even (approx 2000 to 3000 square metres per month).

This break-even volume will continue to increase with the decreasing gap in the prices of thermal, violet and PS plates. Usage of UV CTP is confined mainly to large plate service bureaus.

SILVER
Silver halide technology has been used for years for both film and plates and is a tried and tested technology. It offers high-speed exposure and excellent quality, but in CTP terms, the technology has effectively peaked. One of the reasons for this is the plates have to be developed, so there is no prospect of a chemistry-free or processless option with silver. And although the plates are processed in what is effectively a closed-loop system where the silver is recovered, it is still classed as hazardous waste and requires appropriate handling. For certain high-quality applications, some printers still prefer to stick with silver despite the advances in photo-polymer and thermal plates. But silver halide has had its heyday, and R&D is now focused on violet, thermal and inkjet.

THE FUTURE
A few years ago, some plate manufacturers were denouncing violet chemistry-free and no-process plate technology as something that was a mere pipe dream, and would never come to market as a commercially available product. How wrong they were: at Pamex earlier this year, manufacturers showed (or spoke about) violet chemistry-free plates that are set to ship around now. Meanwhile, that most ubiquitous of  technologies - inkjet - could be the key to the holy grail of printing plate technology in that it promises a solution comprising a simple, low-cost platesetter, and a plate that requires no processing or special treatment. An inkjet CTP system deposits a press-ready image directly onto a metal plate without the need for a photosensitive coating. One to watch.

The future of CTP
Faster, productive systems will evolve to image many plates quickly; new generations of low cost, energy-efficient laser diodes will be employed; large arrays of edge-emitting laser diodes may simplify and speed the imaging mechanisms, providing a fillip for on-press imaging and there are wildcards that may impact the future development of the CTP market.

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