Laser is an emerging discipline and high-tech technology. Since its birth in the early 1960s, it has been valued by countries around the world and has developed rapidly. As a result, the application range of lasers continues to expand, and correspondingly profound changes have taken place in many fields. The printing industry around the world, like other industries, is also actively adopting this new technology. Laser is used in electronic plate making and color separation, laser phototypesetting, holographic printing technology, etc., and has greatly optimized the printing system. Due to space limitations, this article only discusses the application of laser in plate making.
The printing plate is an indispensable part of the printing process. It is the medium that transfers ink to the substrate. The quality of the printing plate is directly related to the quality of the printed matter. The printing industry has been working hard to improve the plate-making process in order to achieve the best results. It can produce printing plates as quickly as possible while reducing labor intensity and plate-making costs. In the early stage, the production of gravure, embossed, and offset printing plates mainly relied on manual, mechanical, chemical corrosion, electrophotographic technology, etc. However, these methods had shortcomings such as lack of operational stability and long plate-making time. Since the birth of the laser, these problems have been solved Now, using the high intensity, high coherence, and monochromaticity of laser, printing plates can be produced quickly and reliably.
A laser engraving printing plate is to shoot a focused laser beam toward the printing plate, melt the specified range of the printing plate, and then remove the unnecessary parts to produce a convex or concave image. The shape, size, and size of the image can be modulated electronically. control. Generally speaking, when the power density of the laser reaches 10-lOw/cm, the plate-making materials (including ceramics) will be melted or vaporized. After the medium-intensity laser beam is focused by the lens, the power density value obtained at the focus is much larger. With the above values, the laser is more suitable for engraving printing plates. Because of its characteristics of monochromaticity, high energy, and good coherence, laser shows strong advantages in engraving and plate making. Especially the development and application of modern purple laser technology have made the production of printing plates more perfect. The laser has high intensity and can not only melt and etch non-metallic materials (such as imaging film, photosensitive resin plate and plastic plate, etc.), but also melt metallic materials (nickel, lead, steel, chromium and other plates). Even highly refractory ceramic rollers can be etched, with a much wider etching range than other methods. Laser plate making is fast and of good quality. Generally, the time to engrave a folio is about 3 minutes. If the purple laser technology with a shorter wavelength is used, the time will be shorter, and the resolution can be improved to ensure the quality of the dots. Because laser has good coherence and concentrated energy, it has high engraving efficiency and low total energy consumption. Laser plate making is not perfect. The problem is that the effect of laser engraving metal directly is not good. Because the ink holes etched by laser are not smooth and have burrs, and the metal surface has a strong reflection effect on the laser, only a high-power laser can be used to engrave it. The general solution to this problem is to put a resin or plastic sleeve on the outside of the metal roller, and the laser does not directly engrave on the metal plate.
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