Introduction to CTP Plate (I)

With the increasing development and application of CTP technology, people in the industry realize that CTP plate is a core part of this technology. Compared with the traditional plate-making process, the processing of the CTP plate is somewhat tedious, but its remarkable printability is unmatched by traditional plates, such as the quality of the dots. For this reason, the market for CTP is bullish. There are about 30 CTP systems in the UK, and there are about 400 globally. DuPont expects to increase to at least 5,000 units by the year 2000. Therefore, it has become more and more important to understand and 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.
The requirements for CTP plates are as follows:
The plate must be economical and practical to complete the laser exposure process in a short time. The photosensitive wavelength must be shifted from the UV region of the conventional PS plate to the visible or infrared region. And the exposure speed is nearly 100 times that of conventional PS plates, and the exposure energy should be below 100 UJ/cm2.
The plate used for high-quality color printing must have high sensitivity, good resolution, strong dot reproduction capability, high printing durability, easy handling, and high contrast requirements.
For a 175 lpi color printed CTP system, the output scanning resolution of the plate making machine should be greater than 2000 dpi, the tone adjustment range of the image should be between 2% and 98%, and the plate material is suitable for printing plate suitability and printing capacity. There must also be comprehensive practical considerations in terms of costs.
Currently used CTP plates include: heat-sensitive plates, silver salt diffusion transfer plates, silver salt emulsions and polymer compounds, photopolymerization, electrostatic, and spray masks.
Silver salt diffusion transfer silver salt diffusion transfer version due to the use of diffusion transfer imaging technology, sensitivity to a variety of laser, such as argon blue laser. Yttrium aluminum laser, ruby ​​laser and so on.
Composition: A roughened aluminum plate, a silver salt emulsion layer, and a physical developer layer.
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.
Photopolymerization type photopolymerization CTP plate, printability and the traditional PS version is very close.
Composition: Coarse aluminum plate, polymer compound layer, PVA layer. (PVA not only prevents oxygen from entering the polymer layer and reacts with the photoactive group, but also plays a catalytic role in exposure.) The polymer compound layer includes: a photosensitizer, a polymerization monomer, a polymerization initiator, and a binder.
Principle: The VA layer 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 part, but also enhance the lipophilicity of the graphic part, and can be printed after drying. It is worth noting that, after the exposure is over, the polymerization reaction continues for several hours. At this time, the defects on the plate are generally removed by the infrared aging effect.
Features: Printability is good, the process is relatively clean, after the baking version, the printing rate is considerable, the printing plate can withstand scratching and brushing.
Composite composition of silver salt emulsion and polymer compound: roughened aluminum plate, PS photosensitive layer, adhesion 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. Then the second exposure (UV light source), so that the polymer layer to see the light, with a brush to wash the support layer, the polymer layer developed with an aqueous solution, and then washed with water, sizing and drying can be printed on the machine.
Features: The process is complex, adding chemical fluids.
Composite composition of silver salt emulsion and polymer compound: roughened aluminum plate, PS photosensitive layer, adhesion layer, silver salt emulsion layer.
Principle: The first exposure, the formation of silver salt latent image, development, washing, producing a protective layer of masking, followed by a second exposure (UV light source), so that the polymer layer to see the light, washed with a brush to remove the layer of polymer The layer is developed with an aqueous solution, rinsed with water, dried on a sizing machine and printed on the machine.
Features: The process is complex, adding chemical scum, but the advantages are obvious. The energy of the light source is lower than that of the single polymer type, which improves the stability of the latent image and the printability of the printing film is good; the printing rate after the baking version is large. (To be continued)