【1】 Introduction to screen printing
Screen printing belongs to orifice plate printing. The simple understanding is to use mesh glue to seal the redundant mesh area, leave the required image or text, and transfer the ink to the substrate through the holes of the orifice plate through a certain pressure to form the image or text.
Screen printing substrate can be paper, wood, glass, metal, plastic and many other substrates.
Common screen printing applications in daily life include instructions on products, decorative patterns on household appliances, T-shirt patterns, guide signs, book covers, posters, business cards, etc.
【2】 Technological process of screen printing
The general process is as follows:
Screen printing file output → film production → screen production → color printing → ink curing
01, screen printing file output;
It's the silk screen production document sent by the designer to the manufacturer, because the screen printing production is mostly monochrome or multicolor overprint, so we need to deal with the document at the early stage of design. Vector file is the best document format, such as aicdpspdf. If the graphics are small or the definition requirements are low, it is also OK to provide high-definition image format.
Hierarchical design of documents
Because the narrow sense of screen printing can only be monochrome printing and monochrome overprint, the designer needs to carry out layered processing on the document, for example, black and red / black and blue need to split screen printing twice.
There are also some artistic creation, do not need to ensure consistency, can be multi-color synchronous screen printing
【3】 Problems and solutions in printing ink
Foaming: the reasons are that the printing viscosity is too high, the drying is too fast, the plate and the substrate are separated too fast, the layout is not good, the ink itself has problems, etc., so the corresponding measures can be taken to adjust according to the above reasons, or appropriate defoaming agent can be added and the ink can be replaced.
2. Block: the reason is that the printing speed is too fast, the printing viscosity is too high, the diluent is not used properly, the printing position is blown by wind, the ink fineness is unqualified or the impurities are brought. The drying speed should be adjusted properly or the ink should be replaced.
3. Pinhole: because the substrate is too smooth, the printing surface has grease or impurities, and the ink itself is not good, so the substrate surface must be pre printed, and the leveling agent or the excellent ink should be replaced.
4. Poor adhesion: the reason is that the ink is not selected properly, the pre printing treatment is not sufficient, the substrate has impurities, the drying temperature and time are insufficient, the dosage of additives, curing agents and drying agents is not appropriate, and the base color is solidified too hard when the two-component ink is stacked.
Because PE, PP, pet, aluminum foil and other materials have low chemical polarity or too smooth, they are generally treated with spark, flame, strong acid leaching to improve the surface tension of printing surface. After the ink film of two-component ink is cured, due to the chemical reaction, it is difficult to cross link into a dense ink film. The completely cured ink film is difficult to be etched by solvent. Therefore, when the color overlay printing is done, the bottom color table can be printed after drying, and other factors can be adjusted by corresponding methods.
5. Drawing: the reason is that the viscosity is too high, the drying is too fast, and the resin and solvent used in the ink are not matched properly. Use the appropriate solvent, adjust the appropriate viscosity or replace the fine ink.
6. Migration, color: the reason is that the ink is not used properly, especially with a large number of plasticizer soft films, which is more likely to migrate, and appropriate ink should be selected.
7. White or foggy on the printing surface: the reason is that the diluent contains water, the high air temperature in the printing environment, or the printing ink itself is not good.