1、 At present, there are three main types of CTP plate: silver type CTP plate, photopolymer type and  thermal CTP plate

Let's take a look at the characteristics, advantages and disadvantages of these plates.
 

（1） Silver type CTP plate
 

Silver type CTP plate mainly includes silver type diffusion transfer plate and silver type and Positive PS Plate.

Silver type diffusion transfer plate is mainly composed of plate base, silver type emulsion layer and physical developing core layer. The diffusion transfer imaging technology is adopted, which is based on the silver type CTP plate exposed by laser scanning. In the developing solution containing silver halide solvent, Ag + and silver halide solvent complex and diffuse to the image receiving layer, reduce to metallic silver under the catalysis of physical developing core, and deposit on the surface of the body to form a silver image. At the end of development, the silver halide emulsion layer on the surface is removed by water washing, and the hydrophilic sand and image area in the non image area are exposed. In the fat sensing liquid, the long fatty chain organic molecules with sulfhydryl group are selectively adsorbed on the deposited silver surface to make the image area lipophilic.

Results the deposited silver image began to accept ink and repel water, but the non image part (silver free deposition) still repels ink, so as to achieve the purpose of computer direct plate making.


 

Silver type and PS plate composite plate are mainly composed of silver type emulsion layer with high sensitivity and PS plate with wide color sensing range. On the coarsened and anodized aluminum substrate, a pre sensitized photosensitive polymer layer, a bonding layer and a silver halide emulsion layer are successively coated. The imaging principle is that first, the silver type layer is exposed once by laser, and a picture and text silver image is formed on the resin layer, so that the photosensitive layer below can be protected from photosensitivity during the second exposure.

After one development, the emulsion layer of the non exposed part is dissolved, and then the second exposure is carried out, i.e. the whole panel is exposed with UV light. Because the image and text layer blocks the light, UV light only exposes the photodegradation sensitive resin layer of non image and text part. The resin layer after secondary development and secondary exposure is dissolved to expose the alumina plate base. Finally, the silver image layer can be treated with the solid solution.
 

Characteristics of Silver type CTP plate
 

1. Silver type CTP plate has a high sensitivity, which can reach 1-3 μ J / cm2. That is to say, using a laser with low output power, low energy and low intensity can also achieve high-speed plate output. Moreover, Silver type CTP plate is the most sensitive plate among CTP plates.

2. Silver type CTP plate is widely used in red laser, green laser and violet laser systems. Its washing method and post-treatment process are the same as the traditional method, and the CTP plate of different manufacturers is compatible with the formula of chemical solution.

3. Silver type CTP plate has the characteristics of high resolution, wide spectral response and good dot reproducibility. The number of screening lines can reach 300 lines / inch, dot coverage can reach 1% - 99%. The plate quality is excellent, and the printing resistance can reach more than 250000 prints. It is more suitable for large printing volume and high quality printing.

4. Because the silver type CTP plate uses expensive silver as raw material, the production cost is increased to a certain extent, and the silver type CTP plate cannot be operated in the open room, which brings some limitations to the plate preservation.