The amount of ink absorption can be considered from the perspective of pore size. After the ink is filled into the pores, the capillary tubes in the paper absorb the binder in the ink. If the pores between the paper fibers are small, the capillary action of the fibers is destroyed, and the ink absorption performance is also poor; if the pores between the paper fibers are too Large, the 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, causing through-printing, and affecting the thickness of the dried ink layer. Make the imprint can not show the proper color saturation on the paper, which affects the amount of printed matter.
The amount of penetration in the pressure penetration stage and the free penetration stage have a great relationship with the absorption performance of the paper, especially free penetration is more prominent. Therefore, the stronger the ink absorption of the paper, the faster the paper absorbs the ink binder, and the faster the ink drying speed. The ink absorption of paper has a great relationship with the quality of the printed matter. Many printing failures are caused by the mismatch between the ink absorption of paper and the printing conditions used.
1. Paper absorbs too much ink
(1) The imprint is matte and powdery
In printing, the paper mainly absorbs the binding material in the ink. If the paper absorbs the ink too much, the binding material is excessively absorbed into the paper layer or coating, resulting in the lack of binding material in the ink layer on the paper surface. The pigment particles are suspended on the surface of the paper. After the conjunctiva dries, the printed product will fade in color or lose its luster. Even if some of the prints are rubbed, the pigment will peel off in a granular form, causing powdering. When the pulverization is serious, in the process of printing, the ink layer of the previous color will be peeled off from the paper surface when printing the next color.
The solution is as follows
â‘ Replace the appropriate paper.
â‘¡Use tackifier to increase the viscosity of ink, or add ink with higher resin content to the ink.
â‘¢Moisture-conditioning the paper.
(2) Through printing
When the ink viscosity is low and the printing pressure is too high, the paper absorbs ink too strongly. The binder penetrates into the internal pores of the paper, replacing part of the air in the paper pores, causing scattering between air-fiber, air-filler and air-coat Decreasing the interface reduces the light scattering ability of the paper and increases the transparency, which may cause the phenomenon of through-printing.
The solution is as follows
â‘ Replace the appropriate paper.
â‘¡ Reduce printing pressure.
â‘¢Improve ink viscosity.
(3) The density of the ink layer decreases and the hue changes
When printing on paper with large pores, part of the pigment and binder will penetrate into the paper together (the pores of the paper fibers are larger than the pigment particles). Excessive penetration of the binder will make the blot dry, the coloring power of the ink will decrease, and the ink The saturation of the layer is reduced, so that the color density of the printed matter is significantly reduced. At the same time, a significant reduction in the color density of the printed matter will also cause the hue of the printed matter to change and affect the correct reproduction of the gray balance.
The solution is as follows:
â‘ Replace the appropriate paper.
â‘¡ Test the gray balance data again for this kind of paper.
2. The ink absorption of the paper is too weak
The ink absorption of the paper is too weak, and the speed of ink absorption is too slow. Although a brightly colored ink layer can be obtained during the printing process, it affects the penetration and oxidative polymerization of the ink, resulting in a reduction in the speed of ink fixation and the transfer of ink to the paper After being applied, it cannot be quickly absorbed by the paper, so that the wet ink will be transferred to the back of the other paper covered above, causing sticking, and in serious cases, adhesion.
The solution is as follows:
â‘ Replace the appropriate paper.
â‘¡ Increase the printing pressure appropriately.
â‘¢ Lower the ink viscosity.
â‘£ Reduce the printing speed.
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