[Chinese Packaging Network News] In the printing process, the phenomenon of pinholes produced by ink printing is a headache for the staff working on screen printing. If it is the printing of opaque objects such as billboards and thick paper, this is not easy to observe small holes, and generally does not become a problem. However, precise printing on some highly demanding products on aluminum plates, glass, and acrylic plates requires no pinholes after post-processing and etching. In addition, the causes of pinholes in the printing of inks are also varied, and many of them are currently unexplained, and some may also be problems with quality management. Pinhole exclusion of printed products is one of the most important inspection items in the inspection of printed products.
Here we analyze the appearance of pinholes that often occur in several ink printing processes:
1, the substrate surface cleaning. Aluminum plates, glass plates, acrylic plates, etc. should be printed before they are printed. In multicolor printing, a method of rubbing with alcohol prior to printing is generally used. In addition, semi-automatic and fully automatic ultrasonic cleaners can also be used. After pre-treatment, dirt such as grease can be removed, and dust attached to the surface can also be removed.
2. Dust and foreign objects attached to the plate. At the time of plate making, there are some sols mixed into the water wash image. In addition, when the emulsion is applied, dust may be mixed in, and pinholes may be formed on the screen. These tests can be found and repaired promptly if they are checked. If dust and foreign matter adhere to the screen, blocking the screen openings can also cause pinholes. Before the official printing, if the use of strong ink absorption paper, after several printing, you can remove the dust from the plate.
3, detergent washing machine is often mixed with broken fibers, this detergent is dissolved in alcohol, when cleaning the surface of the substrate, it will often form a thin film of surfactant, printing ink on the film when the pinhole occurs . Therefore pay special attention when using cleaning agents and alcohol. When carrying the substrate by hand, the fingerprint of the hand will also adhere to the printed surface, forming pinholes during printing.
The above-mentioned printed pinholes can be eliminated by paying attention only during the printing process. However, due to the complexity of the printing, many problems need to be dealt with in actual practice.