Analysis of common problems of home-made water-based positive chart PS version

Home-made liquid formulations positive PS version has been widely used in China's printing industry. However, various quality problems reflected in actual production directly affect the quality of printed matter, production costs, and economic benefits of the company. The quality problems of the positive PS version can be divided into two major categories: the quality of the PS version and the quality of the PS version.

One, the quality problem of positive figure PS version body

Since China's PS version experiment was successfully developed and put into production in 1973, the domestic PS edition manufacturing industry has developed rapidly. At present, there are more than 30 manufacturers of PS plates in the country, and there is a "Pattern-type PS plate industry standard." However, due to the differences in the standardization of technologies, equipment, and manufacturers, the quality of the PS version varies from place to place, from factory to factory, and from time to time. Some quality is still unstable. For the quality of the PS version body, the use of manufacturers often pay insufficient attention, often mistaken for their own use of the problem.

1. The background color of PS is not good. After the exposure, the contrast of the color is too small, which causes the multiple printing plates to be trapped in the line and is inconvenient to observe when developing.

2. The development time is not well understood. The development is stronger, the small dots are damaged; the development is weaker, the development is not complete, and the printing is dirty. This phenomenon shows that the development tolerance of the PS version body is too small. A good PS version has a large development latitude, and a little more development time can also keep small dots intact. A shorter time can also keep the printing plate from being dirty, and the development is stronger and weaker. The poor quality of the PS plate requires rigorous development conditions and special attention must be paid when operating.

3. After development, there is a "blue bottom" that causes the printing to be dirty. Even if the concentration of the developer is increased, the enhancement of the development is not effective, and even the graphic is destroyed. This is mainly due to the fact that the color material in the emulsion is deposited deep in the sand. Overexposure can generally be used to remedy this.

4. It is not easy to print on the ink. When the PS version is printed on the machine, it is not easy to apply ink or not to apply ink. There are many reasons. There are two quality factors involving the PS version: First, the PS version has been stored for more than one year or Improper storage, such as the preservation of the ambient temperature is too high (more than 30 °C), relative humidity greatly exceeds 65%, too strong light; the other is the photosensitive adhesive viscosity is too low, photosensitive coating is too thin.

5. Partial "flower version", paste version. There is a certain gap between the thickness and flatness of domestic PS plates and the international level. The thickness is inconsistent, the over-standard and flatness are uneven, which affects the quality of the PS plate, causing local rapid wear and tear, resulting in “flower pattern” and stencil printing. dirty.

6. Broken version. Discontinuation of the printing process, often due to the lead plate base made of cold rolling process, the tensile strength increases, but the fatigue strength is low, brittle, easy to break the plate. If the printing pressure is too high and the speed of the machine is fast, the plate breaks easily.

7. Partially dropped. After the roughening of the electrolysis, the gray quality of the printing plate base is not completely removed, and the partial photosensitive layer is not strongly adsorbed. Printing hundreds or thousands of sheets may partially print out.

8. Locally out of print. Before the application of the photosensitive liquid, the layout was not cleaned, leaving traces of acid flow when hanging, resulting in partial plate-off.

9. PS plate surface roughness is not good, coarse sand, too thin. Abrasives are too thick, water capacity is insufficient, easy to dirty; fine sand eyes, the photosensitive film in the microporous is not easy to clean, the base is easy to pollution, easy to stain on printing.

10. PS version of ink affinity, poor alkali resistance. Sensitizer deteriorated due to failure.

11. Improper ratio of photosensitizer, such as film-forming agent content is too low, sensitivity is reduced, and resistance to printing is low. If the content of the photosensitive resin is too low, the wear resistance and alkali resistance of the photosensitive layer will be reduced, and such a PS plate has low resistance to printing.

12. The photosensitive film is too thin, and the alkaline developing solution easily damages the oxide film during development. When printing on the machine, the printing plate and the blank space are dirty.

PS version body quality problems, in general, the use of manufacturers can not be resolved, can do just the information back to the manufacturer in a timely manner. If the problem cannot be solved, the PS version of other brands and models will have to be re-used. Do not mistake the quality of the PS version for use. (to be continued)