Screen Printing Failures and Countermeasures--Bubbles

Six, bubbles

Substrate will appear bubbles on the ink after printing. The main reasons for bubbles are as follows:

1 The substrate is poorly processed before printing. Substrate attached to the surface of dust and oil traces and other substances.

2 bubbles in the ink. In order to adjust the ink, adding solvents and additives to stir, the ink will be mixed with some bubbles, if placed regardless of the low viscosity of the ink will naturally deaeration, high viscosity inks and some can not be natural deaeration. Some of these bubbles are naturally eliminated in the printing process due to the transfer of ink, while others become larger and larger. In order to remove these bubbles, defoamers should be used. The amount of defoamer added in the ink is generally about 0.1 to 1%. If the amount exceeds the prescribed amount, it will have a foaming effect.

After the ink is transferred, even if it is foamed, as long as the wettability of the substrate and the ink flowability are good, the bubbles on the surface of the printing ink film will be gradually eliminated, and the ink forms a flat printing ink film. If ink bubbles are not eliminated, the ink film will form a ring-shaped uneven film surface. Bubbles in the general ink can be degassed by the action of the screen when passing through the screen. In addition, the use of hot water or boiling water will have a better defoaming effect when the ink is mixed and stirred.

For transparent inks such as red, blue, and green, the linking material of these inks has the feature of easy foaming due to the small proportion of organic pigments in fine particles. If the corresponding thinner, tackifier or release agent is added, the ink can also be converted into a stable ink with good printability.

3 The printing speed is too fast or the printing speed is not uniform. Appropriately reduce the printing speed and maintain the uniformity of printing speed.

If none of the above measures can eliminate air bubbles in prints, consider using other types of ink.

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