Water-based ink superimposition rate improvement measures

In color printing, the adhesion of the ink of the latter color on the ink film of the previous color is called the overprint of the ink. The color effect of printed matter is related to the strength of the coloring power of the ink, the color deviation of the ink, and other factors, and also relates to the size of the overprinting rate of the ink. The overprinting rate of ink, also called the ink receiving amount of ink, refers to the percentage of the main density of the subsequent color ink transferred to the preceding color ink layer on the stacked blocks.

Nowadays, many printers used by carton printing companies mostly use multi-color water-based printing slot machines, and they often encounter problems with low stacking rates. The post-printing color cannot completely cover the previous color, and the occurrence of pitting phenomenon seriously affects the printing effect and causes waste of the cardboard. This is particularly evident when printing large areas of the field. How to increase the overprint rate of water-based ink? The following is a brief discussion.

1 To accelerate the drying speed of the first color ink on the substrate

1) When printing with a four-color printing slot machine, the two inks that need to be stacked are respectively set in the first color group and the last color group, so that the drying time of the first color ink layer can be appropriately increased, which is favorable for the trapping rate. The improvement.

2) Use a quick-drying ink as much as possible during the first color printing, which can speed up the penetration and fixation of the first color ink. Of course not dry too fast, otherwise the ink has dried on the roller, affecting the ink transfer.

3) Pay attention to the arrangement of the printing sequence, and print as much as possible on the smaller area of ​​the graphic, and print on the larger area. The advantage of doing so is that the area of ​​the first color printing graphic is small, and drying is relatively faster, which is beneficial to overprinting of the ink. At the same time, due to the small area of ​​the graphic, it is also possible to reduce the number of pairs of ink layers after the cardboard is conveyed. Dirty chance.

4) Under the premise that the color saturation satisfies the requirement, the thickness of the ink layer of the first color should be reduced as much as possible, which is beneficial to the drying of the first color, and can also increase the overprinting rate of the ink.

2 Adjust the relationship between the two ink fluidity and viscosity

Although water-based inks are soluble in water, it is possible to use water to dilute in order to reduce ink saturation or increase fluidity during printing, but diluting with water is not the best method. Stabilizers are preferably used to minimise the color of the ink for carton printing that requires a bright color. This facilitates the drying of the ink, and at the same time the adjuvant can increase the gloss of the ink layer. After dilution with water, when the ink adheres to the paperboard, it cannot dry instantaneously, and there must be a period of dry time, which will reduce the side pressure strength and compressive strength of the paperboard.

In addition, the relationship between the first color and the viscosity of the rear printing color is adjusted. For multi-color printing, the viscosity of the first color water-based ink is appropriately reduced so that the viscosity of the second color ink is increased at the same time to increase the trap rate.

Source: "Printing World" Author: Liu Chao