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Screen Printing Ink Introduction (Part 1)
Screen printing inks, like other types of inks, are made of pigments, resins, solvents, and additives.Screen printing ink types can be divided to 4 types according to its curing method:
1, Solvent based ink: as the solvent evaporating, the ink film adhere to the substrate.
2, Oxidative polymerization type: through an oxidation reaction, form the ink layer.
3, 2 components reaction type: through a two-component chemical reaction.
4, UV ink: by UV irradiation cause the chemical reaction.
Screen Printing ink types can be divided into 5 types by its applications:
1, Screen printing ink for fabric
2, Screen printing ink for plastic
3, Screen printing ink for metal
4, Screen printing ink for paper
5, Screen printing ink for glass
According to the type of ink binder, screen printing ink can also be divided into many types, which can be roughly divided into epoxy resin ink, polyurethane ink, polyester ink, and vinyl ink type, acrylic ink type, rubber type, etc. Only when it is clear that the substrates are made of different materials can different materials be selected.
Use the same resin type ink to avoid poor adhesion. For uncertain material, it is best to determine the selected ink after passing the printing test.
It’s better to choose the manufacturer’s recommended solvent, because the different solvent has different solubility, to avoid the poor printing effect.
During screen printing ink process, what are the common problems and their solutions?
1, Foaming: the reason is that the printing viscosity is too high, drying is too fast, and the plate and the substrate are separated too quickly.
Solution is to add an appropriate amount of defoaming agent or replace other ink.
2, Screen Blocking: The reason is that drying is too fast while the printing speed is too slow, and the printing viscosity is too high. It is caused by bad and improper diluent, the printing surface is blown by wind, the fineness of the ink is not proper or contains impurities.
3, Pinhole: The reason is that the printed object is too smooth, the printing surface has a protective layer of grease or impurities. It is caused by the poor quality of the ink itself, so the surface of the printed object must be pre-treated to add leveling agent or replace with high-quality ink.
4, Poor adhesion: The reason is improper selection of ink and insufficient pre-treatment; There are dust in the object, the drying temperature and time are insufficient; the dosage of additives, curing agent and drier is inappropriate.
When two-component ink is printed in overlapping colors, it is caused by factors such as excessive solidification of the background color. Due to PE, PP, PET, and aluminum foil have very low chemical polarity or are too smooth, so they are generally treated by corona, flame, strong acid dipping and other treatments to increase the surface tension of the printing surface. After the ink film of the ink is cured, it is cross-linked into a dense and extremely strong ink film due to chemical reactions.
The fully cured ink film is difficult to be eroded by solvents. Therefore, when printing with multiple colors, after the base color is dry,It can be printed, and other factors can be adjusted accordingly.
5, Drawing: The reason is that the viscosity is too high, the drying is too fast, or a improper solvent. appropriate solvent should be used, the appropriate viscosity should be adjusted or high-quality ink should be replaced.
6, Migration and fading: The reason is the use of inappropriate pigments in the ink, especially if there is a large amount of plasticization, so appropriate ink should be used.
7, White or foggy printing surface: The reason is that the diluent contains water, or the air humidity is high, or the printing ink itself is defective. When the printing surface dries, the solvent evaporates and absorbs surrounding heat, causing local water vapor to solidify inside the ink film or on the surface, causing white fog.
Therefore, you should choose an appropriate drying speed or reduce the space humidity, or replace the high-quality ink.
Screen Printing Ink Additives:
Additives include defoaming agents, leveling agents, anti-friction agents, matting agents, etc., which should be used according to the instructions in the manual. Improper use will result in poor printability, poor gloss, or dry too slow, decreased adhesion or other adverse consequences.
The curing agent and drier should be added accurately according to the usage ratio, otherwise it will increase the ink condensation.
screen Printing INK
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Add: RM1902 EASEY COMM BLDG 253-261 HENNESSY ROAD WANCHAI HK, CHINA.
Tel: +86 757 22606975
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