How to solve the problem caused by improper paper absorption
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The amount of ink absorbed can be considered from the viewpoint of pore size. After the ink is filled into the pores, the hair tube in the paper absorbs the binder in the ink. If the pores between the paper fibers are small, the capillary action of the fiber is destroyed, and the ink absorption performance is poor; if the pores between the paper fibers are excessive Large, ink absorption is too strong, when the viscosity of the printing ink is low, the capillary not only absorbs the binder, but also absorbs the pigment, which will cause the ink to penetrate the back of the paper, which will cause offset and affect the thickness of the ink layer after drying. The imprint does not exhibit the desired color saturation on the paper surface, affecting the amount of printed matter.
The amount of permeation in the pressurized infiltration stage and the free permeation stage is highly dependent on the absorption properties of the paper, especially the free permeation. Therefore, the stronger the ink absorbing property of the paper, the faster the paper absorbs the ink vehicle, and the faster the ink is dried. The ink absorption of paper has a lot to do with the quality of printed matter. Many printing failures are caused by the mismatch between the ink absorption of the paper and the printing conditions used.
1. The ink absorption of the paper is too strong
(1) The print is dull and powdered
In printing, the paper mainly absorbs the binder in the ink. If the paper absorbs too much ink, the binder is excessively absorbed into the paper layer or coating, resulting in the lack of binder in the ink layer on the paper surface. The pigment particles are suspended on the paper surface, and the printed matter is dried or tarnished after the conjunctiva is dried. Even if the imprint is rubbed, the pigment will peel off in a granular form, causing pulverization. When the pulverization is severe, during the process of printing, the color of the previous color is peeled off from the paper surface after printing one color.
The solution is as follows
1 Replace the appropriate paper.
2 Use a tackifier to increase the viscosity of the ink, or add a higher varnish to the ink.
3 Adjust the paper to moisture.
(2) print through
The viscosity of the ink is small. When the printing pressure is too high, the paper absorbs ink too much. The binder penetrates into the inner pores of the paper, replacing some of the air in the pores of the paper, causing scattering between air-fiber, air-filler and air-coating. The interface is reduced, the light scattering ability of the paper is reduced, and the transparency is increased, which may cause the offset phenomenon to occur.
The solution is as follows
1 Replace the appropriate paper.
2 reduce the printing pressure.
3 improve the viscosity of the ink.
(3) The density of the ink layer is reduced, and the hue changes.
When printing on paper with large capillary pores, some of the pigment and the binder will penetrate into the paper together (the pores of the paper fiber are larger than the pigment particles), and the excessive penetration of the binder will dry the blot, and the tinting strength of the ink will decrease. The saturation of the layer is reduced, resulting in a significant decrease in the color density of the print. At the same time, a significant reduction in the color density of the print also changes the hue of the print and affects the correct reproduction of the gray balance.
The solution is as follows:
1 Replace the appropriate paper.
2 Perform a gray balance data test on the paper.
2. The ink absorption of paper is too weak
The ink absorption of the paper is too weak, and the speed of absorbing the ink is too slow. Although a bright ink layer can be obtained during the printing process, it affects the osmotic fixation and oxidative polymerization of the ink, so that the fixing speed of the ink is lowered, and the ink is transferred to the paper. After that, it cannot be absorbed by the paper very quickly, so that the undried ink is transferred to the back of the other paper covered by it, causing stickiness and sticking in severe cases.
The solution is as follows:
1 Replace the appropriate paper.
2 Appropriately increase the printing pressure.
3 Reduce the ink viscosity.
4 reduce the printing speed.