Analysis of common problems in the PS version of t

2022-08-23
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Analysis of common problems of domestic water based positive PS version

domestic water based positive PS version has been widely used in China's printing industry. However, various quality problems reflected in the actual production directly affect the quality of printed matter, production costs and economic benefits of enterprises. The quality problems of Yangtu PS version can be divided into two categories: the quality problems of PS version and the quality problems of using PS version

I. quality problems of Yangtu PS version

since the successful experiment of developing PS version in 1973 and its production, the domestic PS version manufacturing industry has developed rapidly. At present, there are more than 30 PS version manufacturers in the country, and there is the "Yangtu PS version industry standard". However, due to the differences in the standardization of technology, equipment and management of various manufacturers, the quality of PS version varies with the number of well cover pressure testing machines on the local market, different manufacturers and time, and some quality is still very unstable. Manufacturers often pay insufficient attention to the quality problems of the PS version, and often mistakenly believe that it is the problem of their own use

1. The background color of PS version is not good. After exposure, the contrast of the color becomes too small, resulting in the line blockage of the printing plate after multiple exposure, which is not easy to observe when developing

2. It is difficult to master the development time. The development is stronger, and the small spot is damaged; The development is weak, the development is not complete, and it gets dirty when printing. This phenomenon shows that the development tolerance of PS version is too small. A good PS version has a large development tolerance. It can keep a small and complete point even if it takes a little more time to develop, and it can keep the printing plate from getting dirty if it takes a little shorter time. It can develop completely if it is stronger or weaker. The poor quality PS version requires harsh development conditions, so special attention should be paid to the operation

3. There is a "blue background" after development, causing dirty printing. Even if the developer concentration is increased, it is useless to strengthen the development, and even the graphics and texts are destroyed. This is mainly caused by the deposition of the pigment in the photosensitive adhesive at the depth of the sand mesh. Generally, overexposure can be used to remedy

4. It is not easy to ink, and the PS version is not easy to ink or not at all when it is printed on the machine. There are many reasons. There are two quality factors related to the PS version: first, the PS version has been stored for more than one year or is improperly stored, such as the storage environment temperature is too high (more than 30 ℃), the relative humidity is too high, more than 65%, and the light is too strong; The second is that the viscosity of photosensitive adhesive is too low and the photosensitive coating is too thin

5. Partial "flower version" and paste version. There is a certain gap between the thickness and flatness of the domestic PS plate and the international level. The inconsistent thickness, over standard and uneven flatness affect the quality of the PS plate. Another alternative term is that the fracture modulus is locally and rapidly worn, resulting in "flower plate", paste plate, and then plate falling and dirty

6. Broken version. The interruption of the printing process is often due to the fact that the lead plate base is made by the cold rolling process, which improves the tensile strength, but the fatigue strength is low, brittle and easy to break. If the printing pressure is too high and the machine speed is fast, it is easy to break the plate

7. Partial word dropping. After electrolytic coarsening, the gray matter of the plate base is not removed completely, and the local photosensitive layer is not adsorbed firmly. If hundreds or thousands of copies are printed, local plates may be lost

8. Partial version loss. Before coating the photosensitive solution, the layout was not washed cleanly, leaving traces of acid flowing when hanging to dry, causing local plate loss

9. The surface roughness of PS version is poor, and the sand mesh is too coarse and fine. The sand mesh is too coarse, the water retention is insufficient, and it is easy to get dirty; The sand mesh is too fine, the photosensitive film in the micropore is not easy to be clean, the plate base is easy to be polluted, and it is easy to get dirty when printing

10.ps version has poor inkability and alkali resistance. It is caused by deterioration and failure of photosensitive agent

11. The proportion of photosensitizer is improper, such as the content of film-forming agent is too low, the sensitivity decreases, and the printing resistance is low. If the content of photosensitive resin is too low, the wear resistance and alkali resistance of the photosensitive layer will decline, so the printing resistance of PS version is low

12. the photosensitive adhesive film is too thin, the alkaline developer is easy to damage the oxide film during development, and it is easy to absorb moisture and dirt on the stencil and blank during machine printing

ps version body quality problems can't be solved by the manufacturer in general. What can be done is to feed back the information to the manufacturer in time. If the problem cannot be solved, we have to choose the PS version of other known brands and models again. Don't mistake the quality problem of the PS version for the use problem. (to be continued)

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