Thermal Technology - Computer Direct Plate Making

The computer-to-platemaking technique was first commercialized in gravure and flexo printing in the 1980s and was applied to plain printing in 1990. In 1975, the concept of computer-to-plate was first tried on an electrostatic plate, but neither the resolution nor the calendering speed could meet commercial printing needs. In 1982, the silver salt coated polyester version was used for monochromatic low register precision printing. Until 1990, metal lithography that used silver salt technology for four-color commercial printing began to be used. This type of printing plate has high photospeed. In 1995, thermal plates with heat transfer or thermal cross-linking were formally launched. In recent years, the introduction of new low-cost high-energy infrared laser tubes has accelerated the promotion of thermal technologies.

With the continuous development of computer-to-plate technology, the entire global printing and publishing industry is also rapidly growing. In 1999, the total value of the global printing and publishing industry reached US$750 billion. And it is expected to increase by 2.5%~3.5% annually. As the world's third largest industry with 675,000 industry companies, nearly 4 million employees, and 250,000 printing plants, the global printing and publishing industry itself is undergoing continuous transformation, including the application and development of computer-to-plate technology. It is recognized by the industry as the future direction of the printing industry. Vantage Strategic Market and State Street Consultants, with industry research yearbooks, predict that by 2003, 18% to 25% of the global demand for printed media will come from computer-directed plates. The global installed capacity of computer-to-plate machines will increase from 1,435 units in 1997 to 1,1,500 units in 2003. State Street Consultants also predicts that in 2003, 53% of the global installed capacity will be thermal platesetters.

What is heat-sensitive technology? Thermal technology refers to the type of energy source needed to image the plate, not the processing of the plate. The image is generated by thermal energy rather than light energy. One of the more important concepts in thermal technology is the critical value. This is because the critical value is the key to determining whether the plate is imaged. In other words, under the critical temperature, the plate does not generate an image and no reaction occurs. When the critical temperature is reached, the plate produces images. Also, when the temperature exceeds the critical temperature, which is equivalent to the excessive glow in the traditional printing process, the dot size and shape that have been generated will not be affected. This fundamentally solves the inaccuracy of copying of outlets caused by excessive, insufficient or artificial factors in the traditional plate making process. Moreover, the concept of critical value of thermal technology is also equivalent to the core concept in digital technology. Non-zero is not only a "1" concept. Whether the image on the plate is only determined by whether or not the critical value is reached. This makes digital computer direct plate making possible. Therefore, it can be said that only the thermal technology is the only choice for the direct digitalization of computer direct plate making.

Thermal computer direct plate making technology can be roughly divided into two categories:
(1) Thermal cross-linking (2) Thermal fusion The first type is thermal cross-linking type, which is a kind of thermal plate that has relatively mature technology and has achieved large-scale commercial production. The basic composition of the plate is a roughened aluminum base plate and a thermal crosslinked material coating. The image forming principle of the plate is mainly absorbed by the infrared crosslinked material of the thermal crosslinked coating to convert the infrared energy into heat energy, so that the crosslinked reaction occurs when the thermal crosslinked coating reaches a critical temperature, and the plate after the light is irradiated. A preheating process is applied to the development to further promote the curing of the crosslinking reaction, and then the development is performed in an alkaline developer to remove the coating of the non-visible light portion.
The second type is a hot-melt type. The basic composition of this plate is a smooth aluminum plate without a roughening treatment, an ink-receptive layer of hot-melt material, and a PVA layer (or silicone). The principle of imaging is to use a semiconductor diode to light the printing plate. The hot-melt material of the heated part is combined with the aluminum plate base to form an ink-receptive layer, and no light part can be peeled off or blown off.
The thermal computer-to-plate making technology is still evolving. Currently, it has developed a free-run thermal plate free of chemical liquids and a waterless version without any process. From the research direction of the entire thermal computer direct plate making technology, we can see that thermal plate computer direct plate making technology is developing toward the direction of non-chemical treatment and green environmental protection. This also meets the needs of the entire printing industry for the future of green digital printing trends.

As a relatively mature, large-scale commercial production and application of computer-to-plate technology, thermal technology is increasingly accepted and accepted by customers in the printing industry. What are the outstanding characteristics of the thermal technology that the industry calls the future direction of computer direct plate making? I will analyze the characteristics of direct thermal plate-making technology for everyone.

(1) Brightroom operation Because of the threshold value concept I mentioned earlier, this makes it possible to operate the thermal plate under the light room, so there is no need for special cassettes and darkrooms, and the operator can clearly control every step of the process. . For many years, the plate-making printers have been trying to move out of the darkroom. If they still use visible light technology, the printer will be 20 years behind. One of the key advantages of today's thermal technology is that the plate can be processed under bright yellow or UV filtered white light. This freed the plate-making staff from the darkness and regained sight.

(2) Abnormal sharp corners, high resolution, and no dot gain Also due to the concept of critical values ​​I mentioned earlier, this concept is actually a binary dioptric mode, which allows the dot size to be accurately duplicated and the dots Sharp edges, almost no dot gain. After studying the thermal CTP plate, GATF found that the dot reproduction accuracy of the plate can reach 0.5% to 98%, and can reach at least 2% to 97%. This is exactly the result of the 1995 GATF survey of visible light plates. The highest range that the material can reach. The following figures are enlarged ones for a thermal plate and a photosensitive plate. We can clearly see the sharpness of the edges of the thermal plate's Internet point, and the edges of such sharp dots make it possible to copy high-quality dots. Using thermal CTP plate, you can get 1100LPI network cable precision image. And when outputting 600LPI images, it can generate 1% dot. This provides a strong guarantee for the fine prints pursued by the printing industry. This feature of thermal technology has made it quickly selected by many commercial printers worldwide who are looking for quality printing.

(3) The printability of the thermal plate meets the high quality printing requirements.
The thermal technology CTP plate is very stable on the press. After the plate is on the machine, only a small amount of overprinting paper can quickly reach the ink-water balance, and this balance can be maintained during printing, and the water consumption is small. The printing surface during the printing process is very clean and free from the concerns of the upper part. The following figure is the enlarged root of the printing plate's Internet site. We can clearly compare the advantages of the thermal printing plate and the hydrophilic zone. This ensures excellent printability. In addition, the heat-resistant printing plate can reach 150,000 to 250,000 impressions when it is not baked, and 1 million impressions after baking, and it is suitable for matte paper printing and UV inks.

(4) Non-chemical treatment process to reduce environmental pollution Another advantage of today's thermal imaging systems is that the media can meet the minimum and non-hazardous development requirements, as well as the development trend without development. Because the principle of thermal imaging is different from that of photosensitive plates, on the one hand, the use of silver salts in the production of plates is avoided, and silver is avoided. On the other hand, the silver in processed liquids is also avoided in the process of plate washing. Ionic pollution of the environment. And the future development and application of non-chemical liquid flush or no-extraction thermal plate will further reduce the environmental pollution in the process of plate removal.

(5) The image is very stable. Because the thermal imaging technology only depends on the critical value, the image generated on the plate after the light is very stable. After printing, the plate can be placed for 6 months and then developed. The same will not affect the quality.

(6) Easy-to-use thermal CTP plate is similar to the traditional PS plate in terms of feel and processing, and it is fully applicable to the existing dampening solution and on-press plate adjustment device. This allows plate-making staff, printers can easily accept and operate this digital plate, without fear of the conversion of traditional processes to digital processes.

Of course, thermal technology has many disadvantages at the same time, such as the need for high-energy laser to make up for the lack of speed. However, with the rapid development of laser technology and the development of thermal technology itself, shortcomings in this area will not affect the overall advantages of thermal technology for the printing industry. Currently, there is a supply of thermal media on the market that meets the demand for rapid plate-making in the newspaper market. Its plate-making speed can reach 360 thermal plates per hour, which fundamentally changes the view that plate-making speed of thermal plates is slow. State Street surveyed printing customers in 3/4 cities in North America and found that 70% of potential buyers plan to use thermal imaging systems when limiting respondents to indicate only one type of media they like.

The future development trend of the printing and publishing industry will surely be to bid farewell to the darkroom, to the digital, to remove environmental pollution, and finally to achieve digital green printing. In the process of printing and publishing industry going digitally green, thermal direct computer plate making technology will undoubtedly be the best choice.



Kodak Poly Lighting Group Beijing Representative Office