Bubbles in glass screen printing

Bubble glass may sometimes appear on ink after printing due to the following reasons: ① Poor prepress treatment of the substrate. Adhesion of dust and oil stains on the surface of the substrate; ② Bubbles in ink. To adjust the ink, when adding solvents and additives for stirring, some bubbles will be mixed in the ink. If left unattended, low viscosity ink will naturally defoaming, while high viscosity ink may not naturally defoaming. Some of these bubbles are naturally eliminated during printing due to the transfer of ink, while others become larger and larger. To remove these bubbles, an defoamer is used, and the amount of defoamer added to the ink is generally 0. About 1% to 1%, if the specified amount is exceeded, it will actually have a foaming effect. Even if the ink foams after transfer, as long as the wetness of the substrate and the fluidity of the ink are good, the bubbles on the surface of the printing ink film will gradually disappear, and the ink will form a flat printing ink film. If the ink bubbles are not eliminated, the ink film will form a circular and uneven film surface. When bubbles in general ink pass through the screen, they can also be defoaming due to the effect of the screen; ③ Excessive or uneven printing speed can also generate bubbles. The printing speed should be appropriately reduced to maintain uniformity of the printing speed. 6. Electrostatic faults usually have a small electrostatic current but a large potential difference, which can lead to phenomena such as attraction, repulsion, conductivity, and discharge The adverse effects on screen printing. The silk screen during printing is electrified by the pressure and scraping of the scraper rubber, causing the rubber part and the silk screen to become charged. The wire mesh itself is electrified, which can affect the normal inking and cause plate blocking faults; At the moment of output of the substrate, it will be sucked by the silk screen; ② Methods to prevent static electricity. The methods to prevent static electricity include adjusting the ambient temperature and increasing air humidity. The appropriate temperature is generally around 20 ℃, and the relative humidity is around 60%; It can transmit static electricity in wet air; Reduce screen spacing and printing speed.