Looking at the current development trend of the CTP market, technology competition is inevitable. Taking the plate material as an example, there are four types: silver salt type, photopolymerization type, thermosensitive type (thermographic type), and processing-free CTP plate. As the saying goes, there are pros and cons of each.

1. Silver salt CTP plate

Silver salt type CTP plate material mainly includes two types of silver salt diffusion transfer plate and silver salt and PS plate composite plate material.

The silver salt diffusion transfer plate is mainly composed of a plate base, a silver salt emulsion layer and a physical development core layer. It uses diffusion transfer imaging technology, the principle is the silver salt plate exposed by laser scanning, in the developer containing silver halide solvent, Ag + and silver halide solvent complex diffuse to the image receiving layer, in the physical development of nuclear It is reduced to metallic silver under the action and deposited on the body surface to form a silver image. After the development is completed, the silver halide emulsion layer on the surface is removed by water washing, exposing the hydrophilic sands and image areas of the non-image area. In the lipid-sensing liquid, the organic molecules of the long fat chain with mercapto groups are selectively adsorbed on the surface of the deposited silver Make the image area oleophobic. As a result, the deposited silver image began to accept ink and repel water, while the non-image portion (without silver deposition) still repels ink, thereby achieving the goal of computer-to-plate.

The composite type of silver salt and PS plate is mainly composed of a silver salt emulsion layer with high sensitivity and a PS plate with a wide color range. A pre-sensitized photosensitive polymer layer, an adhesive layer and a silver halide emulsion layer are sequentially coated on the roughened and anodized aluminum substrate. The imaging principle is that the silver salt layer is first exposed with a laser to form a graphic silver image on the resin layer, so that the secondary photosensitive layer can be protected from light during the second exposure. After the primary development, the emulsion layer in the non-exposed area is dissolved and then subjected to secondary exposure, that is, the entire plate surface is exposed with UV light. Since the graphic image layer blocks the light, the UV light only exposes the photodegradable photosensitive resin layer in the non-graphical part, and the resin layer after secondary development and secondary exposure is dissolved to expose the alumina plate Finally, the silver image layer can be fat-sensitized with solid-plate solution.

Characteristics of Silver Salt CTP Plate

(1) The silver salt type CTP plate has high sensitivity.

It can reach 1 ~ 3μJ / cm2, even using low output power, low energy, low intensity laser, can also achieve high-speed printing plate output. Moreover, the silver salt type CTP plate has a fast photosensitive speed, which is the fastest photosensitive plate among the CTP plates at present.

(2) The application range of silver salt CTP plate is wide.

The red laser, green laser, and violet laser systems can be used. The rinsing method and post-processing process are the same as the traditional method, and the CTP plates of different manufacturers 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 screen lines can reach 300 lines / inch, the dot coverage rate can reach 1% to 99%, the quality of the printing plate is excellent, and the printing resistance is up to 250,000 or more.

(4) Because the silver salt type CTP plate uses expensive silver as the raw material.

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

2. Photopolymerization CTP plate

The photopolymerizable CTP plate is mainly composed of three parts: aluminum mesh base, photosensitive layer and protective layer. The photosensitive layer is mainly composed of film-forming resin, sensitizing dye, photoinitiator, monomer or oligomer, stable Agent and other additives. The protective layer is a polyvinyl alcohol oxygen barrier layer, which is mainly used to block the inhibitory effect of oxygen on monomers or oligomers. The imaging principle is that after the plate is scanned by the laser light source, the sensitizing dye in the photosensitive layer of the light-seeking portion first absorbs the photon energy to become an excited state, and then transfers the energy to the photoinitiator, which decomposes to form free radicals, free The base initiates the polymerization of the monomer or oligomer and solidifies, forming a graphic part. The part where no light is seen is removed by development to form a blank part. It should be noted that before development, the protective layer of the unexposed part should be washed away, and then the high-sensitivity polymer layer should be dissolved with an alkaline developer. After the development, the protective layer should be completely removed with a brush. Finally, rinse the layout with a synthetic resin solution. The synthetic resin not only improves the hydrophilicity of the blank part, but also enhances the lipophilicity of the graphic part. It can be printed after drying.

Characteristics of photopolymerization CTP plate

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

(2) The developing solution used for the photopolymerizable CTP plate is alkaline, and the film-forming resin and monomer or oligomer in the photosensitive layer have a certain acidity, which can be dissolved in an alkaline solution and removed by development, and the alkali The contamination of the developer is small, which is beneficial to environmental protection.

(3) The photopolymerizable CTP plate can use different laser light sources such as violet laser diode (410nm), argon ion laser (488nm), FDYAG laser (532nm), infrared laser diode (830nm), etc. And the photopolymerization type CTP plate can be printed with a printing resistance of over 1 million after baking.

3. Thermal CTP plate

There are many types of heat-sensitive CTP plates, but there are two main types that are relatively mature at present, namely, thermal melting type and thermal cross-linking type.

The hot-melt CTP plate is mainly composed of aluminum plate, ink-receptive layer and PVA layer (used for conventional offset printing) or silicone gel (used for waterless offset printing) without roughening. The imaging principle is to use semiconductor laser diode exposure. The heat-sensitive coating on the plate base (that is, the ink-absorbing layer) is ink-friendly and insoluble in alkaline syrup. After exposure, the coating absorbs energy and improves solubility, and can be dissolved in alkaline syrup. During development, the exposed part is dissolved in the alkaline solution, forming a blank part of the printing plate. The unexposed part does not dissolve, forming the graphic part of the printing plate. After development, it usually needs to be cleaned and glued before it can be printed on the machine.

The thermal cross-linking CTP plate is mainly composed of a roughened aluminum plate and a single-layer PS photosensitive layer. The imaging principle is through infrared exposure. During exposure, the light-to-heat conversion substance converts the light energy of the infrared laser into heat energy, so that some polymers in the photosensitive layer undergo thermal cross-linking reaction to form a latent image; reheating causes the molecular compounds in the graphic part to further cross-link , So that the graphic part will not be dissolved in the alkaline developer. It should be noted that during preheating, the blank portion also partially reacts, so the image of the blank portion should be removed during development. If the temperature is too high, a hot mist will form on the printing plate; if the temperature is too low, it will fade or weaken the graphic part.

Characteristics of thermal CTP plate

(1) The thermal CTP plate has very low sensitivity to natural light, and it is exposed by infrared laser, so it can be operated under bright room conditions.

(2) To generate an image on a thermal plate, the initial thermal energy threshold must be reached, and the thermal energy above the initial threshold will not change the shape of the dot. It is the only technology that can control the predictable results. The printing plate can be extended to 6 months and then developed, without affecting the quality of the plate.

(3) The dots of the thermal CTP plate have good reproducibility and high resolution, and the edges of the dots are sharp and clear. It is easy to achieve water-ink balance during printing, and has good printing suitability. The plate resistance after baking is up to More than 1 million seals.

In addition to the three dominant CTP plates introduced above, the CTP-free plate has become a hot topic for discussion in recent years.

4. Free processing CTP plate

The processing-free CTP plate was first introduced by Asahi Kasei Corporation of Japan. Broadly speaking, it means that the plate is exposed and imaged on the direct plate-making equipment, and it can be printed on the machine without any subsequent processing procedures, of course, without chemical development, rinsing, etc., which is a true processing-free plate; from In a narrow sense, it means that the plates do not require chemical development after exposure and imaging on the direct plate-making machine, but there will still be individual non-chemical processing steps, such as removal of plate ablation waste, coating protective glue and other processing work. In terms of plate-making methods, processing-free plates can be divided into two categories: processing-free plates for DI (Direct Imaging on Press) presses and plates exposed and imaged on CTP direct plate-making machines.

Features of processing-free plates

(1) Compared with the traditional CTP plate, the processing-free plate eliminates the steps of development, fixing, cleaning, gluing, and drying, shortens the plate-making cycle, reduces the amount of energy consumed during exposure, and reduces the overall plate-making cost , Which improves production efficiency and simplifies the production process.

(2) Since the process-free plate does not require chemical development, rinsing, etc., the process-free plate-making process will not produce environmentally harmful chemical waste liquid, exhaust gas, and waste residue, etc., which reduces environmental pollution and is more convenient for printing operators Is beneficial.

(3) Changes in plate processing conditions, changes in laser energy, concentration of processing chemicals, and processing-free plates that do not need to be processed can provide them with higher quality stability.

(4) The processing-free plate does not require a chemical development processing device, which saves plant space, which is a big advantage for small companies, but the processing-free plate is more expensive than conventional CTP plates.

The war in the CTP market has entered the age of warring states, and we have no fear of war. Only in this way can we advance the wheel of history and create a better future.

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