The Today and Future of Rapid Printing Platemaking Technology

Foreword
A new technological revolution is now evolving in the world. Human society has entered the era of a new information economy called "knowledge economy," and printing is recorded and transmitted as a social record. The means of storing information has made an indelible contribution to the history of the development of human social civilization. It has a clear and beautiful image and text. Intuitive, permanent, simple and inexpensive process. Large print, extensive use and other characteristics. Therefore, in the long historical period in the future, it is still an indispensable information tool for human society.

Fast printing meets the needs of the times, with short replication cycles and easy operation. High degree of automation, adapt to the rapid transfer of information and office automation needs. Since the reform and opening up, with the rapid development of the market economy, printed materials have become more and more diverse. Small batch trends. Make our country's rapid printing industry develop rapidly. According to incomplete statistics, China currently has more than 25,000 fast printing companies and more than 35,000 small offset press systems. Throughout China’s fast printing industry, there are only about 1,000 high-end rapid printing equipment. Most of them are still middle- and low-end equipment. The number of special color photography products that can be printed is very small. This is far from the demand in the modern era. therefore. People have put forward higher requirements for fast printing. They hope the printing speed will be faster, the quality will be better, and they will be able to print more advanced color prints. Therefore, for the fast printers, it is of utmost importance to adopt advanced technical equipment and high-quality printing plates and apply them correctly according to actual conditions.

Rapid printing system and plate making method
The rapid printing system mainly uses high-speed small offset presses as the main equipment to realize the integration of typesetting, plate making, printing, and binding, and the two systems, namely, platemaking and printing, are mutually complementary devices to produce high-quality printing plates in order to print high quality. printed matter. Therefore, in the prepress work, it is correct. The fast and effective method of plate making is very important.

There are many methods for rapid printing plate making, which can be divided into the following types:

1. The electrostatic photography direct plate making method was directly made by electrostatic photography and appeared in the United States around 1960. Japan and the United States, mainly used for rapid printing plate making, the use of zinc oxide paper base plate, paper base coated with zinc oxide resin photosensitive layer and some sensitizer, the use of photosensitive semiconductor photoelectric properties, through the electrostatic photography for plate making. Electrostatic photocopying is used to charge the platesetter. exposure. development. Revision. Solid printing and other processes can be used to make printing plates. According to the different development methods, it can be divided into dry and wet methods. The wet method is better than the dry method, and the resolution is higher. Up to 10 ipi/mm wet process plate, the wet process platemaking mechanism plate, and the wet plate process are needed. It is more popular in foreign countries, and dry-process plate making is more widely used in China. The resolution of dry-process plates is 4 to 5/mm. The main features of electrophotographic photography are simple operation, high speed, and low cost. Suitable for printing printed text artwork.

2. Ordinary paper copier direct plate making method This method is a kind of plate making method that uses the electrostatic copying machine to copy, the characteristic is simple and convenient, the lithographic performance requirement to the printing plate is not strict. The earliest was by the American AM company and 3. M company adopts and popularizes the application of zinc oxide paper base waterborne paper base plate. However, it is necessary to disable the fixing part at the time of plate making. After the plate-making, revision and then using a special fixed-plate machine, this method is currently taking up a considerable proportion in China. China's copier manufacturers have produced electrostatic photocopying dual-use machine, such as 邯郸, Wuhan. Zhanjiang and other factories, in addition to Yingkou zinc oxide paper mill production copying system with zinc oxide paper base, better quality, lower prices, an A3 format printing plate is priced at about 1 yuan, resistant to force up to 3000- 5000 printed.

3. Direct photography process
Direct photography platemaking is the use of silver salt diffusion transfer method, do not use film, silver salt version placed on a small camera photography. After exposure. The silver halide layer is developed to form a hydrophilic and hydrophilic portion. This method of plate making is fast and of good quality. It is not only suitable for line drawings and texts, but also suitable for continuous monochrome manuscripts. Can be screened directly for photography. Network cable up to 150IPi/inch. Resolution up to 15 ~ 2OIpi/mm. Silver salt plate is a high-grade plate in the field of fast printing.

4. Pre-painted photolithography
Pre-coated photosensitive version referred to as PS version. Platemaking is based on photocopying by a printing machine. Or sulfate paper and other manuscripts. Exposure to the UV light source is applied to the pre-coated sensitized plate. After chemical development and fixing. Can produce high-quality printing plates. PS version has good reproducibility and high resistance to printing force. The images are bright, rich in levels, and good in writing. Printable color prints. It is a fast printing high-grade plate.

5. The laser plate printing machine direct plate making method laser printing machine direct plate making, was developed and applied by Beijing University of Chemical Technology in early 1990, obtained the Chinese invention patent in 1995, the plate material uses the polyester plate making base silver salt plate or the paper base plate. With the combination of advanced computer typesetting technology and laser printer, quick printing is more simple, clear and beautiful. Resolution up to 600dpi. India's resistance to print more than 20,000 India. The prepared version can be stored for two years, making a cost of A5 format printing plate 5 yuan.

Technical characteristics of several major plates
1. Zinc Oxide Paper Base
The use of zinc oxide (molecular formula ZnO) in electrophotographic technology has developed rapidly since the 1950s and has been going on for half a century. It is one of the more mature plates. At present, it still occupies an important position in the field of fast printing, especially in China, accounting for more than 70% of all kinds of plates. The zinc oxide version is based on paper base. With 90 ~ 127g / m drawing paper or photographic base paper. 3. The zinc oxide fine powder and some sensitizers are mixed in the resin in an appropriate ratio. Only coated with paper on the performance of optical conductors, light conductors have a large dark resistance, can deposit the charge, after the photosensitive material is charged. Electrons were obtained on zinc oxide surface pro-adhesions. Photosensitive zinc oxide after sun exposure. That is, photoconductive electrons and holes are generated. The pro- attachments in the system fail.

The dark resistance of the plate area is reduced. Presented as conductive area. Still maintaining a certain potential, the surface of the photoconductor is formed as an electrostatic latent image. The magnetic brush was used to develop the toner on the latent image. That is, it becomes a visible image, and the plate for printing is produced after revision-fixing.

Zinc oxide plates are available in dry and wet versions. Platemaking must use their own version of the plate making system. Dry process plate resolution is 4 ~ 5Ipi/mm. Wet plate making is 10IPi/mm. According to the paper base thickness and the water resistance of the coating, the resistance force is 3000 to 10,000. Printable text line drawing manuscript. Wet version resolution, level are better. Is a medium-grade plate.

2. Silver salt diffusion transfer
Silver salt diffusion transfer version uses silver salt diffusion transfer imaging principle to make printing plate, according to the choice of plate. Divided into silver salt paper base, silver salt polyester base film and silver salt aluminum foil version; the first two kinds of plates are more widely used, silver salt paper base is coated with water-resistant resin on both sides of paper base to improve the paper base Water-resistance, double-sided coated paper based on polyester film base coated with hydrophilic layer, hydrophilic layer containing oxide particles (titanium dioxide, silicon oxide, etc.) silicone resin, gelatin and developer (in order to disperse oxide particles to enhance hydrophilic layer and Adhesive strength between the image layer or the photosensitive layer) and a small amount of developer allows the silver halide diffused and transferred into the image layer to be rapidly reduced to metallic silver, wherein the oxide particle layer is fine. The coating surface forms a separating agent and the like.

The photosensitive layer mainly contains silver halide, gelatin, sensitizer, etc. The silver salt version is composed of a hydrophilic layer, an image layer, and a photosensitive layer. The currently used silver salt plate is mainly composed of an integral type. The sensitivity layer and the image receiving layer are respectively coated on the same substrate, and are divided into an upward diffusion transfer type and a downward diffusion transfer type according to different coating structures. A hydrophilic layer and a silver salt emulsion layer are first coated on the substrate, and then the physical layer (image layer) is coated by vacuum evaporation or sputtering. It is called upward diffusion transfer type.

On the plate, the hydrophilic layer and the image receiving layer were applied first, and the photosensitive layer was applied to the downward diffusion transfer type.

The former requires better transparency of the image layer, and the hydrophilicity of the photosensitive layer is better, requiring special formulas. The cost is higher, and the latter requires higher peeling of the photosensitive layer. There are many processing operations, but the cost is low. The silver salt version is suitable for printed matter with high print quality because of its good plate-making quality and high resistance to printing forces.

3. Pre-coated version (PS version)

Pre-Painted Photographic Plates, which are abbreviated as PS plates, are pre-coated with a photosensitive resin solution on a specific plate, dried, and then stored like a film, and removed when needed. Fast printing uses a lithographic PS plate, mainly for short-run color prints. PS plate making is fast and convenient, affected by the climate, and has a good version. Ink absorption and ink transfer are good and reproducibility is good. Recoverable N3O line prints.

The PS plate used for quick-printing small offset presses is mainly composed of a plate base and a photosensitive adhesive coating. After the plate base has been treated with hydrophilicity, a layer of photosensitive adhesive is applied, and the PS plate produced after drying is printed. Aluminum-based Ps plate, cellulose acetate film Ps plate and paper Ps plate, according to the different types of photosensitive materials and developer, can be divided into positive PS version, negative PS version and anhydrous PS version, the current Yang Pattern PS version of the broader application.

The plate base is the substrate that bears the photosensitive layer and is the main component of the printing plate. In order to meet the printing needs, the plate base should have good hydrophilicity, and the coating layer should have strong adsorption force and firm adhesion. The aluminum plate used as a substrate is very smooth. Hydrophilicity, adsorptivity, abrasion resistance and corrosion resistance are all very poor. Therefore, the surface of the substrate must be electrochemically treated. After roughening by electrolysis, the surface of the electrode is roughened, and then anodized to form a dense, hard, passivated oxide film. After the above process is processed to improve the printing plate's preservation and printing rate. Improves the water retention of the printing plate.

The paper base used in the paper-based PS version requires good mechanical strength. But also use water-resistant resin to treat the paper base to improve the water resistance of the paper base. The water-absorbing deformation of the paper base is avoided, a hydrophilic layer is coated on the waterproof layer, and the photosensitive adhesive layer is finally coated.

Due to the small diameter of the small offset press cylinder, the thickness of the Ps plate is mostly 0.10 to 0.18 mm. Generally used 0.15mm photosensitive coating are mostly composed of a variety of ingredients of high molecular composition material. Including sensitizers, film formers, dyes (blocking dyes and sensitizing dyes). Sensitizers, stabilizers, etc. Photosensitizers can be divided into two major types. One is a low molecular organic photosensitive material. The other type is a high-molecular photosensitive compound, also called a photosensitive resin.

Anhydrous PS plate, also known as water-free silicone offset printing plate, this type of printing without water wet, practical silicone resin anhydrous PS plate base for the aluminum version. There are three types of structures. The first type is the siliconization of conventionally used PS plates. The second type is to layer the silicone resin and PS platen into a multi-layer anhydrous PS plate. The third type is to directly make a single-layer photosensitive silicone resin. Water PS version. Photosensitive silicone anhydrous PS plate, plate making process is simple. The development effect is good, the resolution is high, and it is not necessary to dampen with dampening fluid when printing. This version is most suitable for use in quick offset printing machines.

4. Laser printer direct plate making small offset printing machine (LD printing plate)

The LD printing plate was developed and produced by Shenzhen Macleans Paper Co., Ltd. and it was directly printed with a laser printer. It is a new type plate material printed by a small offset press.