Foreword With the development and application of CTP technology, people in the circle realize that CTP plate is the core part of this technology. Compared with the traditional plate-making process, the processing of CTP plate is a little tedious, but its remarkable printability is unmatched by traditional plates, such as the quality of outlets. For this reason, the market for CTP is bullish. There are about 30 CTP systems in the UK, and there are about 400 globally. According to DuPont's forecast, by 2000 it will increase to at least 5,000 units. Therefore, it has become increasingly important to understand CTP plates. For now, there are mainly five different types of CTP plates, and the performance varies greatly between them. Each type of plate has its own characteristics.
First, silver salt diffusion transfer type This type of plate due to the use of diffusion transfer imaging technology, sensitivity to a variety of laser, such as argon blue laser, holmium aluminum garnet laser, ruby ​​laser and so on.
Principle: The blank part sees light. When developing, the light part is dissolved by the developer. The graphic part of the light does not form a conjugate on the core layer. The residue of the blank part is rinsed with warm water, and then the graphic part is subjected to lipophilic treatment. .
Features: Similar to silver halide film, good sensitivity, fast exposure, moderate contrast, light source is low intensity, low energy consumption laser, different manufacturers of CTP plate is compatible with chemical solution formulations.
Second, polymer compound type polymer compound type CTP plate, printability is very similar to the traditional PS version.
Composition: Coarse aluminum plate, polymer compound layer, PVA layer. The polymer compound layer includes a photosensitizer, a polymerization monomer, a polymerization initiator, a binder, and the like.
Principle: When exposed, the sensitizer absorbs the energy of the laser and produces a polymeric group together with the initiator. Prior to development, the PVA layer of the non-visible part is washed away, and the high-sensitivity polymer layer is dissolved with an alkaline developer. After the development is completed, the PVA 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 portion, but also enhance the lipophilicity of the graphic portion, and can be printed after drying. It is worth noting that, after the exposure is over, the polymerization reaction continues for several hours. In this case, infrared rays are generally used to stabilize it quickly. Infrared aging can also remove the defects on the plate.
Features: good printability, relatively clean processing, after baking, the resistance is more impressive, the printing plate has been scratched and brushed.
Third, the silver salt emulsion and polymer compound composite type (abbreviation) take into account the advantages of the previous two printing plates.
Composition: Coarse aluminum plate, PS photosensitive layer, adhesive layer, silver salt emulsion layer.
Principle: The first exposure, the formation of silver salt latent image, development, rinse, resulting in a protective layer of protection. After the second exposure, the polymer layer is exposed to light, and the mask layer is washed away with a brush. The polymer layer is developed with an aqueous solution and then rinsed with water. After the glue is dried, it can be printed on the machine.
Features: The process is complex, adding chemical pollutants, but the advantages are also obvious; the energy of the light source is lower than that of a single polymer type, the stability of the latent image is improved, the printing adaptability is good, and the printing resistance is higher after the baking version .
Fourth, spray mask type fourth CTP plate, using spray or spray technology.
Composition: Conventional PS plate plus a thin layer of soluble or wax soluble layer.
Principle: The ink jet head of the CTP system is used to inject and expose ink on the plate, and the mask is washed. The subsequent processing is the same as that of the conventional ps plate.
Features: Due to the use of the regular PS version, no additional equipment is required, making it the most economical CTP plate.
Fifth, the heat-sensitive thermal CTP version of the choice of a large, hot-melt type, thermal erosion type, photo corrosion type, thermal cross-type, degradation type technology, thermal type plate, both direct imaging There is also indirect imaging through the mask. The following describes two thermal-type CTP plates.
1, hot melt type composition: light source, without roughening of the aluminum version, ink layer, PVA layer (conventional offset printing), silicone (waterless offset printing).
Principle: Using a semiconductor laser diode, melt the graphic part to expose the underlying oleophilic layer and remove the residue on the plate to prepare for printing on the machine.
Features: Non-chemical treatment process, from the perspective of environmental protection, especially worthy of promoting the use of thermal-type CTP plate. Second, you can work under the bright room. As far as the Pearl model is concerned, the resistance to India is a bit lower (50,000 impressions), but it has now risen to 100,000 impressions.
2, thermal cross-linked type composition: coarse aluminum version, single-layer PS photosensitive layer.
Principle: After a certain temperature is reached by infrared heat instead of spectrum, some of the polymers in the photosensitive layer undergo thermal crosslinking reactions to form latent images; reheating causes the molecular compounds in the graphic part to undergo further cross-linking reflections. It is because the graphic part is not dissolved in the alkaline developer. It is worth mentioning that some reactions occur in the blank part during preheating, so the image of the blank part is removed during development. If the temperature is too high, a hot mist will form on the plate; if the temperature is too low, the graphic part will be weakened or weakened.
Features: There is almost no relationship between exposure time and exposure energy. In other words, below the energy threshold, the external conditions will not affect the quality of the plate; beyond the energy threshold, the size and clarity of the dot will not be affected. Therefore, there is no such thing as underexposure and overexposure; the nature of the graphic part is very stable, and the plate is still usable even six months after exposure; in addition, the thermal crosslinked plate has a low sensitivity to natural light. It is thus possible to work under the light room, and only a conventional plate making apparatus is required for processing.
The earliest manufacturer of thermal-type plates was Kodak. Its direct thermal imaging system has 47 sets worldwide. Polaroid recently joined the market with product models Quantum830 and Quantum1064.
Many businesses that produce CTP plates are considering developing thermal-type plates. DuPont also has related patented products. The company's Horsell Anitee says that it will soon be available on the market. In addition, laser ablation imaging using dry processing is also brewing.
Conclusion CTP is a very active field in today's printing industry. In the near future, we expect to see more new products and technologies.
First, silver salt diffusion transfer type This type of plate due to the use of diffusion transfer imaging technology, sensitivity to a variety of laser, such as argon blue laser, holmium aluminum garnet laser, ruby ​​laser and so on.
Principle: The blank part sees light. When developing, the light part is dissolved by the developer. The graphic part of the light does not form a conjugate on the core layer. The residue of the blank part is rinsed with warm water, and then the graphic part is subjected to lipophilic treatment. .
Features: Similar to silver halide film, good sensitivity, fast exposure, moderate contrast, light source is low intensity, low energy consumption laser, different manufacturers of CTP plate is compatible with chemical solution formulations.
Second, polymer compound type polymer compound type CTP plate, printability is very similar to the traditional PS version.
Composition: Coarse aluminum plate, polymer compound layer, PVA layer. The polymer compound layer includes a photosensitizer, a polymerization monomer, a polymerization initiator, a binder, and the like.
Principle: When exposed, the sensitizer absorbs the energy of the laser and produces a polymeric group together with the initiator. Prior to development, the PVA layer of the non-visible part is washed away, and the high-sensitivity polymer layer is dissolved with an alkaline developer. After the development is completed, the PVA 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 portion, but also enhance the lipophilicity of the graphic portion, and can be printed after drying. It is worth noting that, after the exposure is over, the polymerization reaction continues for several hours. In this case, infrared rays are generally used to stabilize it quickly. Infrared aging can also remove the defects on the plate.
Features: good printability, relatively clean processing, after baking, the resistance is more impressive, the printing plate has been scratched and brushed.
Third, the silver salt emulsion and polymer compound composite type (abbreviation) take into account the advantages of the previous two printing plates.
Composition: Coarse aluminum plate, PS photosensitive layer, adhesive layer, silver salt emulsion layer.
Principle: The first exposure, the formation of silver salt latent image, development, rinse, resulting in a protective layer of protection. After the second exposure, the polymer layer is exposed to light, and the mask layer is washed away with a brush. The polymer layer is developed with an aqueous solution and then rinsed with water. After the glue is dried, it can be printed on the machine.
Features: The process is complex, adding chemical pollutants, but the advantages are also obvious; the energy of the light source is lower than that of a single polymer type, the stability of the latent image is improved, the printing adaptability is good, and the printing resistance is higher after the baking version .
Fourth, spray mask type fourth CTP plate, using spray or spray technology.
Composition: Conventional PS plate plus a thin layer of soluble or wax soluble layer.
Principle: The ink jet head of the CTP system is used to inject and expose ink on the plate, and the mask is washed. The subsequent processing is the same as that of the conventional ps plate.
Features: Due to the use of the regular PS version, no additional equipment is required, making it the most economical CTP plate.
Fifth, the heat-sensitive thermal CTP version of the choice of a large, hot-melt type, thermal erosion type, photo corrosion type, thermal cross-type, degradation type technology, thermal type plate, both direct imaging There is also indirect imaging through the mask. The following describes two thermal-type CTP plates.
1, hot melt type composition: light source, without roughening of the aluminum version, ink layer, PVA layer (conventional offset printing), silicone (waterless offset printing).
Principle: Using a semiconductor laser diode, melt the graphic part to expose the underlying oleophilic layer and remove the residue on the plate to prepare for printing on the machine.
Features: Non-chemical treatment process, from the perspective of environmental protection, especially worthy of promoting the use of thermal-type CTP plate. Second, you can work under the bright room. As far as the Pearl model is concerned, the resistance to India is a bit lower (50,000 impressions), but it has now risen to 100,000 impressions.
2, thermal cross-linked type composition: coarse aluminum version, single-layer PS photosensitive layer.
Principle: After a certain temperature is reached by infrared heat instead of spectrum, some of the polymers in the photosensitive layer undergo thermal crosslinking reactions to form latent images; reheating causes the molecular compounds in the graphic part to undergo further cross-linking reflections. It is because the graphic part is not dissolved in the alkaline developer. It is worth mentioning that some reactions occur in the blank part during preheating, so the image of the blank part is removed during development. If the temperature is too high, a hot mist will form on the plate; if the temperature is too low, the graphic part will be weakened or weakened.
Features: There is almost no relationship between exposure time and exposure energy. In other words, below the energy threshold, the external conditions will not affect the quality of the plate; beyond the energy threshold, the size and clarity of the dot will not be affected. Therefore, there is no such thing as underexposure and overexposure; the nature of the graphic part is very stable, and the plate is still usable even six months after exposure; in addition, the thermal crosslinked plate has a low sensitivity to natural light. It is thus possible to work under the light room, and only a conventional plate making apparatus is required for processing.
The earliest manufacturer of thermal-type plates was Kodak. Its direct thermal imaging system has 47 sets worldwide. Polaroid recently joined the market with product models Quantum830 and Quantum1064.
Many businesses that produce CTP plates are considering developing thermal-type plates. DuPont also has related patented products. The company's Horsell Anitee says that it will soon be available on the market. In addition, laser ablation imaging using dry processing is also brewing.
Conclusion CTP is a very active field in today's printing industry. In the near future, we expect to see more new products and technologies.
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