The CTP technology and developments of violet PDF Print E-mail
Written by Stefan Beke-Bramkamp, Product Manager CTP, Krause-Biagosch - Bielefield   

CTP is one of the main investment plan topics of printers around the world. The question is no longer “Should I go CTP?”; it is “When should I go and which technology is best for myself?”

In some markets, printers have already gone CTP some years ago and now replace their units and sometimes their CTP technologies, because technology moves forward. CTP is known as direct imaging of printing plates by a laser. It can happen on-press or in most cases offline before printing in a CTP device, with or without a processor with different laser, imaging and plate technologies. Systems are now available for all plate formats, applications speeds and budgets, so we can say there is a large variety of CTP systems and technologies, so that the CTP buyer needs to analyse for themselves which system fits their needs in the best way.

CTP has been in the graphic world for more than ten years now and we have seen lots of new lasers since (UV, 488nm Argon-Ion, 532nm NdYag, 1064nm Thermal Yag, 830nm Thermal Diodes and 405nm Violet Laser Diodes). Most of these have been developed for graphic arts but did not really get a mass market and therefore are rather expensive to buy and replace. With these diode or laser technologies we have seen lots of different plate types and technologies, and we’ve gone through several development stages.

CTP engines operate with internal drum, external drum or flatbed imaging technologies. Internal drum and flatbed technologies mainly operate with ‘visible light’ like 405nm Violet Diodes or in earlier years with 532nm NdYag lasers. External drum systems normally operate with 830nm Thermal Diodes.

The digital plate technology is as important as the engine itself, because the engine, the plate technology and the processor join to one combined team in the CTP production. Best plates use high-quality grained and anodised aluminium substrate as we know it from the analogue plates, which ensure a wide latitude, good-quality printing, stable ink/water balance and a predictable press behaviour.

Where the digital plates have differences today is the layer(s) and how they behave towards the different laser wavelengths and in their on-press performance. For the plates it is safe to say that despite ongoing developments we have stable products for visible light or thermal imaging. The market has proven that best quality can be provided by imaging on silver-based plates in internal drum machines or thermal plates from external drum systems and that the highest runs come from burned thermal plates. For newspapers, imaging on polymer plates with violet imaging is the way to go as it provides high-speed imaging and robust on-press performance of plates within a tolerant production process.

The market has gone a fair way already but CTP is still rising and slowly digital plates are superceding analogue plates. We already see that today’s CTP plates get the standard offering of any supplier and that analogue plates play a minor role and their prices go up.

Trends in the past were that the commercial market went into the direction of thermal and the newspaper market went into the direction of visible light imaging, but now we have to look again at the options as most of the benefits of thermal imaging can be provided by violet as well.

Why is violet so popular?

The latest CTP solution to gain success is violet diode technology, and there are many reasons why this technology requires high attention in the printing industry. Violet was launched at drupa 2000 and since proved to be the most innovative CTP technology ever!

With the advent of DVD players and recorders, new violet laser diodes became available, emitting 5MW power at 400–410nm wavelengths, which is what silver plates required to be imaged by an internal drum platesetter. These new laser diodes had a narrower beam, which meant the spinner could be smaller and therefore rotate faster. Lifetime was expected to be 5,000 hours and imaging could be done in yellow safe light with manual systems. Such was the promising start of violet imaging in CTP at drupa 2000.

Since that time a lot of innovation with violet has been done and violet has experienced widespread success around the world and within all applications. The violet laser diode power went up from 5MW to 30MW in 2002, to 60MW around drupa 2004, and now to 100MW, allowing it to be the standard technology for high-speed newspaper CTP devices as well as being introduced with high-speed polymer imaging in internal drum systems. A lot of CTP system suppliers have introduced systems for imaging with violet laser diodes and, more importantly, three big plate suppliers have introduced photopolymer plates that can be burned and reach high quality combined with high run length.

Violet systems seem to be the choice of printers in the newspaper application and in the two-up and four-up market, but violet also gets attractive now for the eight-up and VLF market, as it offers more benefits than any other technology.

But what is the status of violet as per today in the different applications? In the newspaper market, Agfa, Krause and other CTP suppliers concentrate on violet imaging in flatbed systems. Fuji offers internal drum-based systems in the low-speed market. Kodak (with Creo external drum engines and the Newsetter flatbed engine) as well as Screen offer thermal solutions, but Kodak also offers an OEM machine with violet flatbed imaging.

Photopolymer plates for newspaper application are available from Fuji, Kodak and Agfa, who also offers a silver violet plate. Kodak first introduced a thermal plate for the newspaper market and Fuji also announced a thermal newspaper plate. In the newspaper market we have approximately 75 per cent of the systems working with visible light (violet and NdYag) technology and 25 per cent with thermal technology.

The commercial market shows thermal in the VLF and eight-up market, but with the strong approach of Fuji, the eight-up, four-up and two-up market are very promising for violet as violet gains more and more market share. Plates are offered for the thermal market from all major suppliers and photopolymer violet plates from Fuji, Kodak and Agfa now enter the commercial market accompanying the Agfa silver plate, which has been there since drupa 2000. Overall the commercial market is still dominated by thermal technologies but the benefits of thermal are reduced day by day as violet seems to get more R&D attention by the suppliers industry.

Violet diodes today offer a lifetime of more than 10,000 hours and provide energy for approximately 250,000 high-resolution B1 plates, which represents approximately ten years of the plate volume of a mid-size commercial printer. In newspaper application, one violet diode reaches up to three million plates, which shows that violet offers the lowest lifecycle costs in regards to laser replacement combined with competitive system pricing and high-speed flatbed design. The replacement costs for a violet diode either do not count, as the diode lasts as long as the CTP itself, or represents only 15 per cent of the exchange costs of comparable thermal heads.

Imaging with violet on the latest photopolymer plates allows for 1–99 per cent tone reproduction, up to 200lpi with conventional and up to 300lpi imaging with hybrid or FM screening, which ensures highest quality in all applications. As more and more suppliers offer violet plates that are, due to their wavelength, less complicated to produce and to process, we expect to have a tendency of lower plate pricing compared to other technologies with violet. The investment security with violet is given as it already represents a big part of the graphic market and intensive R&D is put into this technology within the media industry, which wants higher resolution for the next level DVDs as well as stronger power. This year Fuji announced processless plates for next year that can be imaged by stronger violet diodes, which will take away the last strong thermal point and can be more effective as thermal solutions as it will provide higher run lengths.

Thermal and violet have their pros and cons, but we see that there will be a choice of different technologies and plates in the future, which keeps up competition. Customers have to analyse for themselves to find their perfect CTP scenario and violet should be part of this evaluation, as it is a good, reliable and cost-effective CTP solution.
 
 
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