The Effect of Newsprint Performance on Color Newspaper Printing (II)

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.
Paying attention to the surface efficiency of newsprint is of great help in improving the printing quality of color newspapers, because the surface efficiency of paper can provide powerful data for some quality problems, which is conducive to finding the cause of the problem. In the process of plate making and printing, according to the surface efficiency of the paper, it can effectively correct the color shift and gray scale of the ink color so as to achieve the gray balance of color overlay and reduce the factors that affect the color quality.
Fifth, the mechanical strength of newsprint For web offset presses, due to newsprint slurry material reasons. Its mechanical strength is an important factor affecting the printing quality. This is mainly manifested in two aspects: tensile strength and surface strength. The web path of the web offset press is generally long. In the high-speed printing process, the tension of each part of the paper path is different and the difference is large. Once the tension exceeds the tensile strength, the web break occurs, which affects normal printing. The surface strength of newsprint is another important technical indicator. In the printing process, when the ink is split between the paper and the blanket, the ink is peeled off due to the adhesion of the ink and the adhesion between the blanket and the paper. tension. When the peeling tension is greater than the surface strength (the internal binding force of the vertical paper surface), the paper strip is peeled from the middle and wound on the blanket cylinder, resulting in a web break and crushing the blanket. The surface of the paper is subjected to a peeling force to produce flakes, lint, and build up on the blanket. When a certain number of printing, the paper powder, paper piles are too thick to make the imprints false, small words off the pen, seriously affect the quality of the printing, but also due to increased pressure, resulting in grinding, reducing the life of the blanket . For color newspapers, the ink layer transferred to the surface of the paper is reduced. The dullness of color lacks a hierarchy, and dot-nets have been severely expanded. Because the ink is “wet and wet” during the printing process, there are also “wet off hairs”. Therefore, besides using high-surface-strength papers, appropriate technical measures must be taken to reduce the use of viscosity. The ink properly reduces printing pressure and printing speed.
Newsprint's dimensional stability Newsprint is made by intertwining plant fibers. The porous surface has hydrophilicity and hygroscopicity, and its water content has a great influence on its dimensional stability, and it has to be contacted many times during the printing process. Water changes the dimensional stability. The dimensional stability not only directly affects whether the printing production can proceed smoothly, but also affects the quality of the printed matter. Changes in dimensional stability include the expansion of the planar dimensions and changes in body shape. Newsprint is highly hygroscopic and therefore has poor dimensional stability. In different external conditions, the dimensional stability is not the same. For newsprint, due to its poor mechanical properties, dimensional stability is of great significance to the smooth progress of the printing process and to obtaining high-quality prints, otherwise it will cause problems such as paper breaks, wrinkle printing, and overprinting during the printing process. Newsprint must be controlled in temperature and humidity during transportation and storage to avoid significant changes, otherwise it will have a greater impact on dimensional stability.
In short, newsprint, as an indispensable printing material in the printing of newspapers and periodicals, must pay enough attention to its performance, and should provide adequate material protection for ensuring the normal production of printing and obtaining high quality printed matter.