Since the direct introduction of computer-to-plate (CTP) technology at the drupa printing exhibition in Germany in 1995, the CTP system has gained rapid popularity worldwide in just a dozen years. At present, the application of CTP systems in developed countries and regions such as the United States, Western Europe, and Japan has accounted for more than 50% of all printing platemaking processes, and some places have reached 60% to 70%. By the end of 2005, more than 400 CTP systems had been put into use in China, mainly distributed in the Yangtze River Delta, the Pearl River Delta, municipalities directly under the Central Government, and inland capital cities. The development space is very large.
1. Violet laser CTP-the rising star of direct laser plate making
1. Development of purple laser and CTP plate-making machine In 1996, Japan Nichia Company developed 400-410 nm InGaM crystal purple laser diode, which was originally developed to further increase the storage capacity of DVD discs. The point is smaller, the capacity of the same size disc is more than 40 times that of ordinary CD discs, and 6 to 7 times that of ordinary household DVD discs, but the laser power applied to DVDs is very small. With the continuous expansion of laser power, purple laser diodes with a service life of more than 3 000h were launched in 1999. In May 2000, the CTP plate-making system began to use a purple laser. At first, it was only 5 mW, and it could only expose the silver salt CTP plate. In 2001, when the plate-making machine used a 15 mW purple laser, it could already expose high-sensitivity photopolymerized plates, but the plate-making speed was slower. In 2002, a 30 mW purple laser diode appeared and was applied to the CTP plate-making system. At this time, plate-making could be quickly performed, and the advantages of the purple laser CTP plate-making system were shown. At drupa2004, the purple laser CTP was in the limelight. Agfa, Fuji, Heidelberg, Esko-Graphic, Escher-Grad, ECRM, Highwater, Krause and other companies launched the purple laser CTP version of the device, with a power of 30-60 mW. After 2005, with the emergence of 60 mW, 100 mW and even more powerful lasers, the CTP technology of purple laser has become even more powerful. Especially for the newspaper industry with high requirements for plate-making speed and quality stability, the purple laser CTP plate-making system is favored. On the other hand, the expansion of the power of the plate-making machine will reduce the reliance on high-sensitivity CTP plates, making large-scale production of medium-sensitivity violet laser CTP plates possible. This has also become a strong backing for the rapid promotion of purple laser CTP technology. Last year, the installed capacity of the purple laser CTP plate-making machine in the newspaper industry surged, which also fully shows that the purple laser CTP is the rising star of direct laser plate-making.
2. Purple laser CTP technical characteristics
â‘´Brighter operating environment
⑵ Small laser spot, high resolution ⑶ Small size, easy maintenance and replacement ⑷ Fast speed ⑸ Stable quality ⑹ Long life
2. Violet laser CTP equipment
1. Equipment characteristics
Due to the small size of the laser, usually the purple laser CTP equipment uses an inner drum imaging structure. It uses the cylinder as the drum supporting the printing plate, and the printing plate is fixed at a fixed position on the inner contour. During exposure, the acousto-optic regulator modulates the continuous laser beam generated by the laser light source according to the light and dark characteristics of the image information in the computer. The modulated laser beam is first irradiated onto the rotating mirror. As the mirror rotates, the laser beam is refracted onto the drum to form an exposure image. Adjusting the focus can change the diameter of the laser beam to obtain different degrees of resolution; adjusting the rotation speed of the mirror can adjust the exposure time. The advantages of this plate-making method are:
â‘´ Scanning speed is faster. Because the purple laser is a short-wave laser with a wavelength of 400 to 410 nm, and the shorter the wavelength, the higher the energy. Therefore, the purple laser has a higher imaging speed compared to other commonly used CTP light sources such as green laser and red laser. The scanning speed of the purple laser can reach 55,000 lines / minute, which is equivalent to the scanning of a folio version with 2 400 dpi resolution in 1 minute 46 seconds.
⑵Higher accuracy. The shorter wavelength light also has another feature, that is, the laser spot will be smaller, and a finer 250 lpi (1% to 98%) dot can be scanned.
(3) Operation close to bright room. The purple laser plate-making system can be operated under the yellow safety light, providing the operator with a brighter working environment and making the operation more convenient.
⑷Longer life. The lifetime of the violet laser of the violet laser plate-making machine can already reach about 5 000h. Because its working principle is to start immediately, the laser is only started when exposure is needed, and it is usually turned off. It can produce stable laser values ​​without preheating and stability, so the overall service life is longer, generally 4.5 to 5 Year (related to workload).
⑸ The price is cheap. Because the purple laser is also widely used in other work, such as making DVD discs, automobile manufacturing, etc., it has a lower price. In addition, a single-beam laser head can be used to make the violet laser CTP plate-making equipment relatively cheap.
⑹ Others. If the upper and lower versions are convenient, multiple punching specifications can be supported at the same time.
2. Since domestic and foreign equipment manufacturers and brands began to use purple lasers in their CTP plate-making systems in May 2000, more than 20 plate-making machine manufacturers worldwide have sold purple laser CTP plate-making machines to the market. At present, violet laser CTP equipment generally uses violet laser diodes with a power of 30 to 60 mW and a wavelength of 405 to 410 nm. Since drupa2004, the models have higher accuracy and more types.
Table 1 lists the products and performance of the major manufacturers of purple laser CTP equipment.
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3. Purple Laser CTP Plate
1. History of plate material development
The original purple laser was only 5mW, and it could only be exposed to the silver salt CTP version. Generally, the sensitivity of the photosensitive version could not meet the requirements. Therefore, there is only the silver salt diffusion transfer version on the market. In 2001, when the plate-making machine used a 15mW violet laser, it could already expose high-sensitivity photopolymerized plates. However, there are fewer varieties of such plates and fewer manufacturers. In 2002, the 30 mW purple laser diode appeared and was applied to the CTP plate-making system. At this time, plate-making could be quickly performed. The corresponding varieties of purple laser CTP plate materials appeared diversified. And the photosensitive CTP plate of medium sensitivity has also begun to adapt to the purple laser CTP plate-making system. International plate material manufacturers have begun to launch their own purple laser CTP plate materials to the market. After 2003, with the advent of 60 mW, 100 mW and even more powerful lasers, more plates can be used to satisfy the purple laser plate-making system. In addition, the sensitivity of the photosensitive plate is not shown in Table 2. Various purple laser CTP plates and their performance have been improved. The purple laser CTP plates available for users on the market are very rich, which relieves users' worries.
2. The domestic and foreign plate manufacturers and brands of purple laser plate can be divided into silver salt plate and photopolymerized plate. The silver salt plate contains a silver halide layer, which is diffused to form a metallic silver image area on the plate surface. This layer is sensitive to light and has a fast exposure. A 5 mW laser is enough. The photopolymerization version uses free radicals to initiate polymerization to produce alkali-insoluble polymers, which can be developed with an aqueous kit. The waste liquid does not contain silver or other potentially harmful substances. Its printing process is 200,000 to 350,000, and it can reach 1 million after baking.
The second film factory of Lucky Group, Zhongkeyin, Shanghai Institute of Printing Technology, etc. have all invested in scientific research and development of purple laser CTP plate materials, and have achieved results. The laser CTP plate material has been domestically produced, paving the way for the newspaper industry to adopt the purple laser CTP technology for cheap plate materials.
4. Newspaper and Purple Laser CTP
Above we talked about some characteristics of the purple laser CTP plate-making machine and plate materials. These advantages of the purple laser CTP plate-making technology are exactly what the newspaper industry requires, so what conditions do the newspaper industry need to invest in the purple laser CTP?
1. Mature workflow
Since the CTP technology is based on a fully digital workflow, the prepress system requires a higher level computer digital network platform. The newspaper industry must consider the following issues:
â‘´Must ensure that the digital technology is based on ADOBE and HARLEQUIN standards;
⑵Networking and remote control process of remote locations and clients;
⑶PDF / JDF standard data format and data processing type;
â‘· Standard CIP3 / CIP4 data control system;
⑸Function of large version and professional trapping function;
⑹ Mature color management and digital proofing technical support.
Its core is a reliable PDF workflow, which fully supports PDF1.3, PDF1.4 and PostScript files, a complete RIP and a PDF workflow running on the network supports multiple file formats, and can output curve PDF, RIP-over PDF , PostScript and 1-bitTIFF files that have been RIP, and also need XML-based PDF, and support CIP3 / CIP4.
2. Concerns of newspaper printing companies
(1) Is the accurate and safe handling of Chinese in the work process safe, reliable, flexible and smooth?
(2) Can the high-speed output of the plate-making machine bring about the effectiveness of publishing and improve the production efficiency?
⑶Is the printing quality improved?
â‘· Will new technologies and new equipment produce benefits in the short term?
⑸Is the production cost reduced?
Since the printed version must be on time, the editing system must complete the editing of the layout after the deadline for submission; the pre-press department must be responsible for the entire process of outputting the finished layout from the newspaper layout software to the completion of the printing plate, in addition to the time requirements Take care of the quality of printing. A series of time levels make the newspaper's prepress production process different from commercial printing, although both processes use the same technology, such as PostScript, PDF, RIP and Page pairing, digital proofing, laser phototypesetting Machine and CTP direct plate-making technology. The biggest difference is that the newspaper's PS / PDF files are stable, that is, from the same typesetting software, while commercial printing may come from a variety of different applications, and the stability is not easy to control. The most important difference is the urgency of time. Even if the printing press fails, commercial printing can still ask for help from other printing companies. It is not a big problem for a day and a half. Newspaper printing is different. The newspaper may be held accountable within 5 minutes.
Therefore, there is a difference in speed between newspaper printing machines and commercial printing machines. How can the prepress process implement such an urgent time requirement? In particular, the CTP direct plate-making machine not only shortens the cost of film printing for the newspaper prepress process, but also can transfer the CIP3 ink control data to the printing machine, which is conducive to the saving of ink and paper. These benefits can play their role in the newspaper process that counts every second.
In addition, the price of purple laser CTP equipment is relatively low, and the operation is stable and reliable. Purple laser is cheap, easy to replace and maintain; the plate making speed is fast, which can reach 30 ~ 35 sheets / hour (30 mW laser), 60 ~ 80 sheets / hour (60 mW) 2 0 0 ～ 2 5 0 sheets / Hour (100 mW); the plate has high durability and is very suitable for the newspaper industry. Purple laser plate material has more room for selection, and has been localized, the price will drop to the price that the newspaper industry can bear; the laser point is small, and it has better network point reduction (1% ~ 99%, 175 lpi), Can produce more exquisite images, improve the printing quality of the newspaper industry. The following is a set of (four) 1 030mm × 800mm printing plates as an example: imported purple laser CTP version (65 yuan / m2) + digital proofing: 214 + 33 = 247 yuan film + imported PS version (50 yuan / m2) ) + Digital proofing: 105 + 165 + 33 = 303 yuan film + domestic PS version (35 yuan / m2) + digital proofing: 105 + 115 + 33 = 253 yuan domestic purple laser CTP version is generally below 60 yuan / m2 And the durability of the CTP version of the purple laser is almost twice that of the ordinary PS version, and the benefits and costs are not a problem.
V. Conclusion
1. Violet laser CTP brings high-precision imaging quality to the newspaper industry
The innate characteristic of the 405 nm violet laser is that the size of the light spot can be controlled to 1 to 2 μm. This physical characteristic well guarantees the imaging quality of the purple laser CTP. With the high-precision inner drum structure and the photopolymerized purple laser CTP plate, the newspaper industry can easily deal with 300-line AM screening and 20 μm FM screening. Platemaking accuracy requirements.
2. Violet laser CTP brings the low cost of laser to the newspaper industry.
As we all know, the 405 nm violet laser has a short wavelength and belongs to a cold light source. The stability of the light source is better. The laser power suitable for exposure imaging of the photopolymerized violet laser plate is only 30-60 mW, which is only a thousandth of the power of the thermal CTP laser. one. Therefore, compared with the high-power laser of thermal CTP, only one laser, purple laser CTP will save the newspaper industry a very considerable laser replacement cost every year.
3. Purple laser CTP brings reliable equipment stability to the newspaper industry
Violet laser CTP equipment adopts mature and stable inner drum mechanical structure. Technicians familiar with imagesetters of traditional plate-making equipment know that the stability and reliability of the inner drum mechanical structure have been verified in the production and application of imagesetters for more than ten years. The inner drum type mechanical structure is stationary during the imaging process, so that the stability of the equipment is effectively guaranteed for a long time, completely avoiding the jamming, flying version and spiral type that often occur with the outer drum thermal CTP The unevenness of flat screen brought by imaging also further guarantees the accuracy of plate-making imaging.
4. The rapid plate-making speed of the purple laser CTP improves the publishing timeliness of the newspaper industry. And the plate has high printing resistance, which is very suitable for the newspaper industry
5. Violet laser CTP brings a stable development environment and the lowest developer cost to the newspaper industry. The unique sand mesh structure and coating process of the purple laser photopolymerization plate make the service life of the developer greatly extended. Of all the CTP plate processing chemicals, the tolerance of the purple laser photopolymerization plate is undoubtedly the largest. At the same time, the process stability is greatly improved, and the labor intensity of the operator is greatly reduced.
All in all, the advantages of violet laser CTP in terms of application cost, stability and production capacity have brought the hope of rapid popularization of CTP to the newspaper industry. We believe that CTP, a technology that is also developing in itself, will bring more surprises to the newspaper industry!
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