Heat-sensitive CTP offset printing plate mainly include heat-melting, heat-etching, photo-etching, heat-crosslinking, and degradable printing plates, including direct imaging and indirect imaging.
The hot-melt plate is composed of a smooth aluminum plate, an ink-repellent layer, a PVA layer (for conventional offset printing), and silica gel (for waterless offset printing). The imaging principle is to use a semiconductor laser diode to melt away the graphic part, exposing the lipophilic layer below, removing the residue on the plate, and then it is ready for printing on the machine. This offset printing plate uses a non-chemical treatment process and is worth promoting. Second, it can be operated in a bright room.
2.Thermally cross-linked plates.
Thermally cross-linked CTP plates are coated with a layer of polymer sensitive to 830nm laser light on a roughened, anodized aluminum plate base, and then coated with a protective layer. Its imaging principle is through the heat of infrared rays rather than the effect of the spectrum. After reaching a certain temperature, some polymers in the photosensitive layer undergo a thermal crosslinking reaction to form a latent image; reheating causes further crosslinking of the polymer compounds in the graphic part. The purpose of the joint reaction is to prevent the graphic part from being dissolved in the alkaline developer.
There is almost no relationship between the exposure time of this kind of offset printing plate and the exposure energy, and the nature of the graphic part is very stable. Even after 6 months of exposure, the printing plate is still reusable. In addition, thermally cross-linked plates have low sensitivity to natural light, so they can be operated in a bright room, and only conventional plate-making equipment is required for processing.
Heat-sensitive CTP offset printing plate are the direction of development and use, while silver salt plates are only in a transitional period. Thermosensitive CTP plates are one of the most potential plates in the future. It has high energy utilization rate, saving precious metals and other properties.
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