Effect of paper properties on ink fixation

Paper is a kind of film-type material formed by finely intertwining plant fibers in a moist state, adding appropriate amounts of fillers, rubber compounds, and color materials, and dehydrating, pressing and drying.

The fixing of paper for ink is relatively good, and the fiber of the paper and the road are related to cellulose, hemicellulose, lignin, and pectin resins. The paper has the following features: ink absorption property is a reflection of fiber properties, interweaving conditions between fibers, fillers, and the nature and content of the rubber compound. Its essence is the adsorption of the pores between fibers on the capillary of the ink binder. I personally think that paper with a high content of woody fibers has good ink-absorbing properties and strong imprints, such as newsprint, letterpress, etc. In addition, when paper is made, paper with less filler and less material absorbs more ink.

Paper absorption of ink is related to the pressure of offset printing and the length of the imprinting time; it is related to the viscosity of the ink and is related to the structure of the paper itself. Absorption of the ink by the paper is too large or too small to affect the fixing fastness of the print.

Coated paper is the most commonly used high-grade trademark, decoration, self-adhesive paper for offset printing. It is coated with a uniform white paste on the base paper and is made of calendered high-grade printing paper. The surface of the paper is smooth. The ink absorption and reception conditions are very good and the surface whiteness is high. It requires a high degree of smoothness in the coated paper, and the paper is not stripped, and the absorption is as small as possible.

Offset paper is composed of 5% bleached chemical pulp mixed with 50% other pulp, such as pulp, pulp, bamboo pulp, rice straw, wheat straw pulp and reed pulp. Offset paper requirements: 1 paper, small scalability, strong water resistance; 2 no pull hair, no off, play close to the texture; 3 ink absorption should not be too high.

After the ink is transferred from the plate or blanket to the paper, some of the ink, especially the binder in the ink, penetrates the paper. At the same time, the solvent in the binder began to evaporate. In addition, the main part of the linking material produces a chemical reaction and a physical reaction, so that the ink film on the surface of the printing plate gradually increases in viscosity and hardness, and finally forms a solid film layer, which is the drying process after ink transfer.

If the paper is too loose. The oil absorption is too strong, combined with the low viscosity of the ink used. The large amount of printing force can also cause the ink to penetrate the back of the paper, forming a print that can be seen from the north side of the print sheet, called "printing."

The paper absorbs ink too strongly, and the mean value of the capillary aperture of the paper is relatively large, which causes some of the pigment particles to infiltrate into the paper together with the binder, affecting the thickness of the ink film layer, the fixing fastness of the ink layer, and the imprinting on the paper surface. Rendering the proper color saturation will also affect the quality of printed products. On the other hand, when the paper is too small in ink absorbency, the dry and conjunctiva is slow when the printing is performed, and the problem of sticking on the back is likely to occur.

Source: Printing Technology