Several Problems Needing Attention in the Deployment of Ink Addition in Packaging Offset Printing

The order of adding inks should be from large to small, that is, a large proportion of main ink should be added. The deployment of pale ink should be preceded by a diluting agent, and then dark ink should be gradually added to the diluting agent. There are two methods for blending inks: blending a small amount of ink can be done with manual mixing; blending a large amount of ink should use mechanical mixing.

The hiding power of ink refers to the ability of the ink to cover the background. The stronger the hiding power, the lower the transparency of the ink. Four-color printing requires high transparency of the ink, otherwise it will affect the color reproduction of the print.

The ink adhesion is adjusted in printing according to the following factors:

1 The surface strength of the paper. The surface strength of the paper is large, and the adhesiveness of the ink can be adjusted to be larger. On the contrary, the adhesiveness should be adjusted smaller, otherwise the paper “falls powder”. “Lint-fighting” is very powerful, which seriously affects product quality and production efficiency. This is often the most important motivation for regulating ink adhesion.

2 printing speed. When the speed is high, the adhesive deployment requirements are smaller, and vice versa. The faster the speed is, the more likely it is to “pick up” the phenomenon and spread the ink unevenly, and it is necessary to reduce the adhesiveness to suit it.

3 layout text structure. When printing halftone images, the most important thing is that the shape and area of ​​the dot should be correctly reproduced, and the adhesiveness should be adjusted to be larger. When printing real-time images, we hope to get a uniform and solid field, and because there are no dot gain problems, the adhesion must be smaller.

4 workshop temperature. When the temperature rises, the cohesive force of the ink will decrease, and problems such as increased emulsification and increased dot gain rate are more likely to occur. When the ink is adjusted, the adhesiveness of the ink should be adjusted in advance. Conversely, adjust the ink adhesion.

In the production of offset printing, the ink drying is too slow, the most common drawback is that it is prone to "back blemishes." In addition, the drying speed of the ink is too slow, and the free penetration of the binder increases, resulting in dark ink and lack of gloss. The ink drying is too fast, and the ink surface layer is easily conjunctiva during the printing process, which affects the production process, and may also lead to the crystallization of the ink and affect the printing of the subsequent ink of the dry-type overprinting.