CTP pros and cons

Looking at the development trend of today's CTP market, technology competition is inevitable. Taking the plate as an example, there have been four types: silver salt type, photopolymerization type, thermal type (thermal imaging type), and CTP plate-free processing. As the saying goes, each has its own merits and contends.

1. Silver salt type CTP plate

Silver salt type CTP plates mainly include silver salt diffusion transfer plates and silver plates and PS plate plates.

The silver salt diffusion transfer plate is mainly composed of a base plate, a silver salt emulsion layer and a physical development core layer. It uses diffusion transfer imaging technology. The principle is the silver salt version exposed by laser scanning. In a developing solution containing a silver halide solvent, Ag+ complexes with the silver halide solvent and diffuses to the image receiving layer, catalyzing the physical development of the core. Under the effect of reduction into metal silver, deposited on the body surface to form a silver image. After the development is completed, the surface of the silver halide emulsion layer is removed by washing to expose the hydrophilic sand and image areas in the non-image area, and is selectively adsorbed on the surface of the deposited silver by a long-chain fatty molecule with a mercapto group in the sensory fat solution. Make the image area oleophilic. As a result, the deposited silver image begins to accept the ink and repel the water, while the non-image part (without silver deposition) still repels the ink, thereby achieving the purpose of direct computer platemaking.

The composite plate of silver salt and PS plate is mainly composed of a high-sensitivity silver salt emulsion layer and a PS plate with a wide color sensing range. A presensitized photosensitive polymer layer, an adhesive layer, and a silver halide emulsion layer were sequentially coated on the roughened and anodized aluminum substrates. The principle of imaging is to first expose the silver salt layer with a laser to form a graphic silver image on the resin layer, so that in the second exposure, the underlying photosensitive layer can be protected from light. After one development, the non-exposed parts of the emulsion layer are dissolved and then exposed twice, that is, the entire plate is exposed with UV light. Since the image and image layer blocks the light, the UV light only exposes the photo-degradable photosensitive resin layer that is not the image portion, and the second-developed and double-exposed resin layer is dissolved to expose the aluminum oxide substrate. Finally, the silver image layer can be treated with a solid solution.

Characteristics of Silver Salt CTP Plate

(1) Silver salt type CTP plate has higher sensitivity.

Can achieve 1 ~ 3μJ/cm2, that is, the use of low output power, low energy, low intensity laser, but also to achieve high-speed plate output. Moreover, the silver salt type CTP plate has a fast photospeed and is the fastest plate material in the CTP plate.

(2) The silver salt type CTP plate has a wide range of applications.

Red laser, green laser, and violet laser systems can all be used. The rinsing methods and post-treatment processes are the same as the traditional methods, and the different manufacturer's CTP plates are compatible with the chemical solution formulation.

(3) The silver salt type CTP plate has the characteristics of high resolution, wide spectral response, and good dot reproducibility.

The number of screens can reach 300 lines/inch. The coverage of network points can reach 1% to 99%. The quality of the printing plate is excellent, and the printing resistance is as high as 250,000 or more. It is more suitable for large printing and high-quality printing.

(4) As silver salt type CTP plates use expensive silver as raw material.

To a certain extent, the production cost is increased, and the silver salt type CTP plate material cannot be operated under the light room, which brings certain limitations to the preservation of the plate material.

2. Photopolymerized CTP Plate

The photopolymerization CTP plate is mainly composed of a three-part aluminum plate, a photosensitive layer and a protective layer. The photosensitive layer is mainly composed of a film-forming resin, a sensitizing dye, a photoinitiator, a monomer or an oligomer, and a stable film. Agents and other additives. The protective layer is a polyvinyl alcohol oxygen barrier layer, which is mainly used to block the oxygen blocking effect of monomers or oligomers. The imaging principle is that after scanning of the plate material by the laser light source, the sensitizing dye in the photosensitive layer of the visible part first absorbs the photon energy into an excited state, and then transfers the energy to the photoinitiator, and the photoinitiator decomposes to form free radicals. The base initiates the polymerization of monomers or oligomers and cures to form a graphic portion. The portion where no light was seen was removed by development to form a blank portion. It should be noted that before the development, the protective layer of the non-visible part should be washed away, and then the high-sensitivity polymer layer should be dissolved with an alkaline developer. After the development is completed, the protective layer is completely removed with a brush. Finally, the plate is washed with a synthetic resin solution. The synthetic resin can not only improve the hydrophilicity of the blank part, but also enhance the lipophilicity of the graphic part, and can be printed after drying.

Photopolymerization CTP Plate Features

(1) The photosensitive layer of the photopolymerizable CTP plate is very thin, and the graphic part and the blank part are basically in the same plane, which belongs to the traditional offset printing type, and has a high sensitivity, and the plate making speed is fast.

(2) The developer used in the photopolymerizable CTP plate is alkaline, and the film-forming resin and monomer or oligomer in the photosensitive layer have a certain degree of acidity, can be dissolved in the alkali solution and removed by development, and alkali The developer has little pollution and is environmentally friendly.

(3) Photopolymerization type CTP plate can use violet laser diode (410nm), argon ion laser (488nm), FDYAG laser (532nm), infrared laser diode (830nm) and other plate photosensitive light sources, and its cost is lower. And the photopolymerized CTP plate can withstand printing force of more than 1 million Indians after baking.