Application and development of photosensitive mate

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The application and development of photosensitive materials for printing plates (IV)

Article/research and Development Group Hong Changchun

the first generation thermal sensitive photosensitive plate is a negative ditp830 printing plate developed and produced by KPG. It adopts the thermal bridging reaction method. A thermal bridging reaction layer is coated on the anodized aluminum plate. After exposure by infrared laser light (ld830), the exposed part of the plate will heat up, making the acid generator in the reaction layer produce acid, Then as a catalyst, the resol phenolic resin is bridged and hardened. In order to promote this reaction, the plate must be preheated for another 30 seconds after exposure, at a temperature of about 140-150 ℃. After many improvements, the point reproducibility of this kind of plate tends to be more stable; In addition, with the continuous improvement of the developer used together, its suitability and washing ability have been greatly improved. The second generation plate is a positive type printing plate, and the part irradiated by laser light is a non image area. After using the molecules in the photosensitive emulsion layer to absorb heat energy, the intermolecular adhesion is destroyed, making it easy to dissolve in the alkaline developer. Therefore, the pre heating process can be omitted, and the plate making process can be completed only by simultaneous plate washing. The most representative products of this type of plate are Mitsubishi Chemical LT-1 plate (semiconductor laser wavelength 830nm) and lt-g plate (YAG laser wavelength 1064nm), which have a high degree of resolution. At the same time, they can also be processed in the bright room working environment. After development, they are heated and processed, which is more suitable for long-term printing (about 1million brushes). This kind of plate is very suitable for advanced color printing, such as high-precision printing of more than 300 lines, FM printing, etc, UV ink can also be used for printing

finally, a heat-sensitive non-treatment plate (without development step) is introduced, which has two ways: elimination and phase change. The removal formula is to use heat energy to remove the film in the non image area to make it hydrophilic, and the film in other image areas still retains the lipophilicity, so it does not need to undergo development processing. Relatively, in order to eliminate the gas (sublimation) or decomposed fragments generated during exposure, there must be relevant extraction equipment, and this kind of plate has a high resolution; Another way of phase change is mainly the hydrophilic polymer coated on the metal aluminum sheet. After exposure and irradiation by infrared laser (wavelength 830nm), the hydrophilic polymer will change into lipophilic to form the image area, and the part without phase change will become the non image area without further development treatment. Therefore, the heating treatment, development, drying and other procedures after laser exposure can be omitted. This plate is characterized by being able to work in the open room, High printing reproducibility. At present, the treatment free plate has not been developed and listed, but it has a number of patents, which can reduce the impact on the future environment and ecology

VI. conclusion

we know that printing materials, including paper, ink and plate, are the most important factors affecting printing quality. For plate, the key to its quality lies in the development of photosensitive polymers, and the development focus lies in the improvement of its photosensitive sensitivity and the matching of the emission spectrum of laser sources, among which the intensity of 810000 tons produced in China is increased; On the other hand, the external physical properties must be well matched with the base resin, and the thermal stability and viscosity suitability of its own photosensitive material formula are important factors in the development of printing plates. With the progress of computer technology and the emphasis on environmental protection, the computer direct plate making system has emerged. From the direct exposure of digital information, the plate making process has become more efficient and convenient, and the plate making speed has become faster, which can save expensive negatives. In addition, the digital data obtained from scanning the original can be made on the same machine by computer-driven laser exposure, and at the same time, it can be transmitted to the remote end to prepare a duplicate version, or by changing the signal, a negative film can be made on the negative film, which can be used to make traditional lithographic plates after development. The main development trend of printing in the 1990s is to use CTP system to apply to high-capacity newspaper industry, publishing industry and high-quality commercial lithography. The world-renowned machine samples without clamping can also cause numerical deviation. Material manufacturers have successively invested in the research of CTP plates, such as DuPont, Agfa, Kodak and other companies, which have obtained patents and commercial products. At present, the use of CTP plates in Taiwan's printing industry is not common due to price and equipment problems, The printing suitability and printing quality of CTP are still in the evaluation stage

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