Analyze the watermark in the screen

The so-called "watermark" is a trace of traces of photosensitizers and developer impurities remaining on the screen surface after the development of the batch screen printing plate. Because the traces are not obvious, the operator is very difficult to observe with the naked eye, and when the machine is printed, it will show a printing failure such as “no ink leakage” or “poor ink leakage” around the traces.

In the production process of screen printing, tap water is generally used to process printing plates. If the screen printing time is too long or the water flow is too rapid during the processing, the printing effect of the screen printing pattern may be distorted, the printing durability may be low, and the printing screen may have a printing failure such as a large area of ​​ink leakage, and if the processing time is too short or When the water flow is too slow during flushing, it can easily cause a “watermark” failure. In order to prevent the "watermarking" phenomenon on the screen and improve the printing rate of the screen, it is very important to grasp the development flush.

To prevent the "watermarking" from developing and flushing, the method of operation is: after the screen exposure is completed, the two sides of the printing plate are fully wetted with water, and the water flow speed can not be too rapid or too slow. The control of the water flow speed can not wash away the screen surface. The sensitizers prevail. After fully wetting the layout, slightly increase the water flow rate and flush only the non-printing surface of the screen until all of the non-exposed sensitizer (non-printing pattern) flows down. Then put the screen vertically for a while (about 3min ~ 5min), after finishing the screen into the oven, to be completely dry, the screen on the "watermark" disappeared.