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

In color newspaper printing, newsprint is a substrate, and graphic information is presented to readers through paper. Therefore, the printability of newsprint directly affects the quality of the final printed newspaper. The smoothness, ink absorption, whiteness, mechanical properties, and dimensional stability of the paper can all affect the print quality of the newspaper.
First, the smoothness of newsprint In the printing, to obtain faithful to the manuscript of the printed matter is the first condition is the smoothness of newsprint. The smoothness of newsprint reflects the degree of microscopic geometrical unevenness on the surface of newsprint. Only with a certain degree of smoothness, can we ensure the reproduction of images and texts. The surface of newsprint has many pores and pores. To achieve the desired printing effect, that is, the print is clear, the ink is uniform, and the layers are rich, it must be ensured that the paper and the blanket are in good contact. If you want to get rich, colorful graphics, you must put four-color dots on paper as much as possible. The level of paper smoothness plays a decisive role. If the smoothness is small, the ink cannot fully contact with the paper, and the fine dots must be lost and have no layer.
Therefore, the smoothness of the paper is an indispensable condition for determining the number of lines of the screen and obtaining a high quality dot. Highly flat paper can obtain enough ink, and the ink layer is uniform, the thickness is uniform, the ink transfer rate is high, the density of the printed matter is high, the dot enlargement value is small, the color is rich, and the reproducibility is strong. Paper with poor smoothness has incomplete dots, poor colors, and poor color reproducibility. Appropriately increasing the ink's fluidity, ink supply, and printing pressure can make up for the emptiness and falsehood caused by poor smoothness. However, the consequences of doing so is to cause the network to expand, dark tone paste, color cast, you can also print a lighter color, to achieve the purpose of the bottom. Therefore, newsprint must use newsprint with high smoothness.
Second, the whiteness of newsprint Paper is the carrier of graphic information, and its whiteness directly affects the color of print. When the light hits the paper, it is absorbed and the amount absorbed depends on its whiteness. The higher the whiteness, the more light is reflected. After the ink is transferred to the paper, the color is formed by the color subtracting method and the color light adding method. The low whiteness of the paper absorbs too much light, and the color of the ink cannot be fully exerted, affecting the hue, lightness, and saturation of the image color, resulting in dull colors, poor contrast, dullness of the picture, lack of vitality, and low levels.
The ink-absorbing properties of newsprint The ink-absorbing properties of paper include the transfer and penetration of ink to paper. It depends not only on the ability of newsprint to absorb the ink binder but also on the absorption of newsprint by ink under newsprint conditions. Therefore, ink absorption should be a comprehensive reflection of the performance of paper (newspaper) and ink under printing conditions. That is, the quality of ink absorption is not entirely dependent on the performance of newsprint, but also depends on the performance and printing conditions of the ink. 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.

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