Digital Reproducible Flat Plate Platemaking Principle

With the continuous development of digital technology, digital presses have greatly improved in terms of print quality, format, speed, etc., prompting digital presses to gradually enter the mass-printing market while consolidating the small-volume print market. Involved in the high-volume high-quality print market at the same time also exposed the deficiencies of the non-reproducible printing plate (disposable printing plate) digital printing press. For example, the replacement of printing plates in large-volume printing not only wastes time, but also easily causes quality differences between the printed products. The advantage of using a reproducible printing plate is that no matter how large the printing volume is, it is no longer necessary to replace the printing plate, thereby shortening the cycle of digital printing, saving raw materials, and at the same time ensuring the uniformity of the quality of the same batch of printing products. Based on the principle of excellence, most digital press production companies have introduced their own reproducible flat printing digital presses. The production company of digital printing presses differs in the types of digital printing presses, the principle of plate making, and the materials used to make plates. It's not the same. This article describes in detail the principles of plate making for various digital reproducible flat printing plates.

1. Instant-type thermal transfer digital reproducible flat printing plate making principle

The plate-making step of this type of printing plate is to first remove the old graphics on the printing plate cylinder, and then perform imaging through a laser imaging head. After imaging, the graphic part on the printing plate is heat-fixed, and all the steps are in the printing machine. Completed within.

Alkaline solution is used to clean the old images on the printing plate. The surface of the cleaned plate cylinder is hydrophilic. After the platemaking, it is used as a hydrophilic blank, and the ink-friendly graphic part is directly made on the surface of the plate cylinder. The graphic part of the material is a synthetic polyester, which has a roll shape prior to plate making. During the platemaking process, the synthetic polyester is pulled tightly against the surface of the plate cylinder, and the synthetic polyester is burned onto the surface of the plate cylinder with a laser beam controlled by the color separation data of the original, thereby forming a graphic portion on the printing plate. After that, the text part was short-time thermosetted with hot air at 150°C to complete the printing plate. When the plate cylinder rotates during plate making, the laser head moves along the axial direction of the cylinder to complete the entire layout of the plate. The imaging system is generally a multi-laser head, commonly used is 64 laser heads, the resolution of the plate produced can reach 2400dpi.

The printing plate made by this method is generally used for web printing, and the ink is transferred onto the paper via a blanket, which belongs to the horizontal printing technology category. After the printing is completed, the polyester layer of the printing plate is washed away with a chemical lotion, and the next batch of printing plates can be produced. The key to instant-type thermal transfer digital regenerative flat printing platemaking technology is to ensure that the hydrophilic properties of the printing plate cylinder base and the oleophilic properties of the polyester material transferred to the drum surface are stable.

2. Prefabricated thermal transfer digital reproducible flat printing plate making principle

Prefabricated thermal transfer digital remanufactured flat plates are plated off-line, using a special imaging system to make graphics on transferable materials, allowing simultaneous production of different manuscripts for different manuscripts to be printed. . Then, the prefabricated transferable material with different graphic contents is rolled up and stored in the material box in the printing unit. During the platemaking process, the prefabricated material is pulled out of the material box and is tightly attached to the plate cylinder. Then, the material is heated to transfer the graphic image to the plate cylinder. The graphic part is then temporarily thermosetted with high temperature to complete the printing plate production. After a batch of printed products is printed, the surface of the plate cylinder is chemically cleaned, and the next batch of prefabricated material to be printed is pulled out of the material box and plated.

With this method of plate making, only one heat source for transferring images and texts as wide as the plate cylinder is required in the printing unit, and an imaging system is no longer required. The printing method is the same as the previous one. The difference is that it uses the unit type B-B printer.

3, inkjet digital reproducible flat printing plate principle

The basic principle is to use a non-contact method to spray a special ink with ink receptivity on the surface of the printing plate to form the graphic part on the printing plate, and the surface of the printing plate is oxidized and electrolyzed to have hydrophilicity. Performance, as a blank part of the plate. In order to improve the printability and stability of the printing plate, the printing plate may be subjected to heat treatment or other physicochemical treatment. This type of printing plate is often produced offline. Of course, it is also possible to install such a plate making system in the printing unit and perform in-machine plate making.

After printing a batch of printed products, the graphic parts on the plates can be cleared to make the next batch of printed materials. The key to this digital remanufactured platemaking technology is that the cost of the cleaning device used to clean the printing plate cannot be too high, and the hydrophilicity of the plate should be maintained well after the continuous plate making. At present, this technology is still being further improved.

4, magnetization toner type digital reproducible flat printing plate making principle

The principle of this technique is to first make an image on the plate base by the imaging system according to the data of the color separation manuscript. The resulting image is a magnetic latent image. The drum rotating magnetic latent image absorbs the toner containing iron and the toner adheres to the image. After the plate is heated and solidified, it becomes the graphic part of the printing plate. During the printing process, ink is received, and the printing plate itself is hydrophilic, forming a blank part on the printing plate. The ink is washed off by the graphic part transferred onto the paper by the blanket, and the next batch of printing plates can be produced. This technology belongs to the category of horizontal printing.

Theoretically, the graphic part of the printing plate made by this method should be capable of continuous printing without the need of inking after every printing of one printing article. However, in fact, due to the abrasion during printing, the printing plate The edge of the graphic part will gradually shrink, resulting in unclear edges of the printed image. Therefore, this kind of printing plate cannot guarantee the quality of the print in continuous printing. Therefore, this technique has not been put into practical use. (to be continued)