Newsprint and Printing (center)

When the newsprint is constant, changing ink properties or printing conditions will change ink absorption. The ink absorption directly affects the drying speed of the ink on the surface of the paper, and also affects the color effect and the film fastness of the ink. The essence of ink-absorption is the comprehensive reflection of ink absorption and adhesion during the printing process. It is not only related to the surface properties, porosity, compressibility, and adsorptivity of the paper, but also the composition and rheology of the ink. Dryness and other related, but also with the printing method, printing pressure and stamping time and so on.
Newsprint has a low degree of smoothness, and it is impossible to obtain a large amount of transfer under the condition of less ink supply. When the ink supply is large enough, the ink layer is in contact with the surface of the paper at the moment of imprinting to obtain a larger ink transfer amount. Therefore, the ink transfer amount differs depending on the nature of the paper surface. In order to achieve the desired printing effect, under the same conditions, the amount of ink supply must be determined according to the surface properties of the paper to meet the amount of solid ink required for different papers and the amount of free ink required to cover the surface is split on paper. The amount of ink.
During the transfer of the ink to the paper, the binder of the ink undergoes sorption and pressure infiltration, and the surface portion undergoes physical and chemical changes to form a solid dry ink film. When the ink absorption of the paper is too large, the amount of ink sucked is large, and too much of the binder and some of the pigment particles are sucked into the interior of the paper, so that the pigment particles are not effectively protected, causing the prints to be unstuck, from the powder, dried up, and the ink dark. Light, reducing the brightness of color, while saturation, hue are also affected. The low ink absorption results in thick ink film and high density in the field, which is beneficial to color reproduction. If the ink supply is too large, the back surface may be dirty. Web offset presses mostly use newsprint and have a high printing speed, so the ink absorption ability of the paper is strong.
Fourth, the surface efficiency of newsprint The color effect that the ink produces after transferring to the paper, mainly depends on the nature of the ink, but it is also inseparable with the nature of the paper. With the same ink printed on different paper, not only the color intensity and contrast are different, but also the difference in color and gray scale is also very large, even if printed on both sides of the same paper, the color effect is not the same. This is because the surface of the paper has different absorbency and gloss.
The surface efficiency of the paper is mainly about absorption and gloss. The absorptivity of the paper is mainly the strength of the liquid absorption capacity, and the absorption of the ink is mainly to absorb the link material in the ink. The color effect of the ink is formed after a certain amount of ink is solidified on the surface of the paper, but the degree of absorption of the binder in the ink or the ink layer is different by the paper, causing the gloss, color density and hue of the ink layer on the paper surface to change. Stronger ones have greater changes; lesser absorbances have less change. Gloss is the optical property of the paper surface - the degree of specular reflection. The degree of gloss depends mainly on the roughness of the surface of the paper and the properties of the materials that make up the paper. The ink is dry and color on the surface of the paper, and its continuity and uniformity after drying of the conjunctiva must be affected by the surface state of the paper, resulting in different color effects. The surface efficiency is high. Under the same conditions, the color intensity of the ink is the largest and the color shift and the gray scale are the minimum. Otherwise, the color intensity of the ink layer is low, the color deviation and the gray scale are relatively high, and the color overprint ash balance is difficult. (To be continued)