What should be paid attention to in the use of screen printing ink?
Sep 09, 2021
Printing ink refers to the screen printing method. All inks are called screen printing inks. Volatile dry ink is the most used ink in screen printing. The composition of the ink film is mainly high molecular material. After printing, the solvent volatilizes and the high molecular material forms the ink film. This volatile drying process is reversible, that is, the dried ink film can be re-dissolved in a solvent.
1. Properly increase the pH value of the ink to reduce the drying speed of the screen printing process without affecting the drying speed. The pH value is generally controlled at 8.5～9.5. If the drying is too fast, add a stabilizer to control the pH value above 9, but not more than 9.5, otherwise the ink properties will change. The surface tension of ink and wash is lower, and the screen plate is more likely to block the plate, and the drying will become slower.
2. Adding slow-drying agent and speed-up can reduce the phenomenon of plate blocking. Too slow screen printing speed will cause the ink to spread on the printing plate and cause the dots to stick. However, if the ink dries too fast, the ink cannot be fully transferred, causing ink accumulation around the dots, resulting in blockage.
3. Without affecting the screen printing speed, try to make the ink drying slower during the screen printing process. This can be adjusted by adding a slow drying agent. The amount of slow-drying agent required for the inks of different manufacturers is different, generally not more than 5%. After adding the slow-drying agent, the ink will thicken and the pH value will decrease. Therefore, water and stabilizers should be added at the same time as the slow-drying agent to control the viscosity and pH of the ink.
4. Adding a slow-drying agent can solve the abrasion of the screen printing and the stickiness of the surface of the varnish plate. The ink drying too fast will cause the ink to dry on the surface of the printing material without entering the penetrating stage, resulting in insufficient adhesion, and the ink layer is easy to fall off. When overprinting or glazing, the printing plate of the next color will stick the ink of the previous color. This can also be adjusted by changing the color sequence or reducing the viscosity of the ink.
5. The paper guide roller generates heat, which can also speed up the drying speed of the screen printing. When we use a large amount of ink in screen printing products, if the drying capacity of the screen printing machine is limited, the speed will not open fast every time it is turned on, and after a period of time, there will be a certain room for improvement in the speed. This is the paper guide. The roller is hot. After the paper guide roller heats up, the ink is not easy to stick to its surface. Before starting the machine, the independent drying device is turned on in advance. The suction device can be turned off when the machine is turned on, so that the equipment can accumulate the maximum heat in the shortest time. The vehicle speed can be increased quickly.
6. If the amount of ink used in the silk-screened products is large, try to choose high-color density inks and higher-line anilox rollers, which is beneficial to the drying of the silk-screened products and can also reduce the phenomenon of water streaks.
