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First, the choice and use of silk screen printing ink
Silk printing inks, like other types of inks, are made by mixing and grinding pigments, resins, solvents, and additives.
1. Drying can be divided into:
Steam drying type - the method of making the ink film by solvent volatilization.
Oxidative Polymerization - A method of forming an ink by means of an oxidation reaction.
Two-fluid reaction type - The method of forming ink adhesion by two-component chemical reaction.
Ultraviolet-curable type - a chemical reaction introduced by ultraviolet irradiation to make ink film adhesion method.
Different drying inks can bring different gloss, different resistance (mechanical resistance, chemical resistance, and weather resistance) to the ink film after printing. Different drying equipments produce different costs, so the user must choose carefully.
2. According to the ink connecting material type can also be divided into many types, but different ink manufacturers choose different resins, can be roughly divided into epoxy resin, polyurethane, polyester, vinyl, acrylic, rubber and many more. Only with a clear definition of the substrate and different materials, inks of different resin types can be used to avoid the bad adhesion consequences caused by ink errors. For substrates with unclear materials, it is best to determine the selected ink after the printing test.
3. Different types of inks use the thinners provided by their manufacturers, mainly because various diluents have different solvency for various types of inks to avoid poor printing effects.
Second, the use of screen printing ink, the failure and its treatment
1. Foaming: The reason is that the printing viscosity is too high, the drying is too fast, the plate and the substrate are detached too quickly, the layout is bad, the ink itself is a problem and other factors, can take appropriate measures to adjust, or add the appropriate defoamer And change the ink.
2. Blocked version: The reason is that the drying is too fast, the printing speed is too slow, the printing viscosity is too high, the use of poor and improper diluent, the printing plate surface by the wind, the ink fineness is not qualified or caused by impurities. Should adjust the drying speed properly, or replace the ink.
3. Pinhole: The reason is that the printed body is too smooth, the printing surface has a grease protection layer or impurities, and the ink itself is not good. Therefore, the surface of the printed object must be pretreated, and the leveling agent must be added or the good ink must be replaced.
4. Adhesion is poor: the reason is that the ink is not properly selected, the pre-treatment is not sufficient; the substrate has impurities, and the drying temperature is insufficient; the amount of additives, curing agents, and driers is not appropriate; , due to solid color and other factors. Because the polarity of materials such as PE, PP, PET, and aluminum foil is extremely low or too smooth, electric sparks, flames, and acid immersion are generally performed to increase the surface tension of the printed surface. After the ink film of the two-component ink is cured, due to a chemical reaction, cross-linked into a dense special ink film, the completely cured ink film is difficult to be etched by the solvent, so when the double-layered ink is printed, the background color is dry. Can print, other factors can be adjusted accordingly.
5. Drawing: The reason is that the viscosity is too high, the drying is too fast, and the ink is mixed with the improper use of the resin and the solvent. The proper solvent should be used to adjust the proper viscosity or replace the good ink.
6. Migration, fading: The reason is the improper use of ink in the ink, especially a large number of plasticizer soft film, more prone to migration, should use the appropriate ink.
7. White or printed surface is misty: The reason is that thinner contains moisture, the printing environment has high humidity, or the printing ink itself is poor. Since the printing surface is dry, the solvent volatilizes to absorb the surrounding heat, causing the local water vapor to solidify in the ink film inside or on the surface causing white fogging. Therefore, the proper drying speed or space humidity should be selected, or the excellent ink should be replaced.
Third, additives, curing agents, driers, varnish oil use.
1. Additives include defoamers, leveling agents, friction additives, matting agents, etc., all of which should be properly added in accordance with the instructions for use. Inadequate printability, poor gloss, slow drying, and poor adhesion will be adverse consequences. .
2. The curing agent and driers should be accurately added according to the proportion of use, otherwise it will increase the crust of the ink, resulting in poor adhesion.
3. Varnish is usually used in the production of gold and silver inks. The transparency of the ink film is increased, the gloss of the ink film is increased, and the ink film cover is used. After adding the varnish, an appropriate proportion of thinner should be added to prevent poor printing effect.
Because the screen printing process has a wide range of applications and low investment, substrates that are difficult to print for other printing methods use screen printing, and thus the screen technology has been rapidly developed in recent decades. Bringing the screen printing process to such a fine feature is that in addition to diversified printing equipment, there is a versatile, multi-purpose screen printing ink. Therefore, it is more important to choose and use silk screen printing inks than to select other printing methods (gravure, relief, lithography, flexo).