Influence of the performance of the hottest newspr

2022-08-23
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The influence of paper performance on color newspaper printing

in color newspaper printing, paper is the substrate, and graphic information is finally presented to readers through paper. Therefore, the suitability of paper printing directly affects the final color newspaper printing quality. The smoothness, ink absorption, whiteness, mechanical properties and dimensional stability of paper will affect the printing quality of color newspapers

I. smoothness of paper

in printing, the primary condition for obtaining a printed matter faithful to the original is the smoothness of paper. The smoothness of the paper reflects the uneven degree of the micro geometric shape of the paper surface. Only with a certain smoothness can the reproduction effect of graphics and texts be guaranteed. There are many pores and pores on the surface of the paper. In order to obtain the ideal printing effect, that is, the imprint is clear, the ink color is uniform, and the layers are rich, we must ensure that the paper is in good contact with the blanket. If you want to get pictures and texts with rich levels and realistic colors, you must present the four color dots on the paper as much as possible. The smoothness of paper plays a decisive role. If the smoothness is small, the ink cannot be in full contact with the paper, and small points must be lost without hierarchy. Therefore, the smoothness of paper is an indispensable condition to determine the number of lines and obtain high quality points. Paper with high flatness can obtain enough ink, and the ink layer is uniform, the thickness is consistent, the ink transfer rate is high, the field density of printed matter is high, the dot enlargement value is small, the color is rich, and the reproducibility is strong. The point obtained by the paper with poor smoothness is incomplete, the color is not bright, and the color reproducibility is poor. Properly increasing the fluidity of ink, ink supply and printing pressure can make up for the emptiness and inaccuracy of imprinting caused by poor smoothness. But the consequence of doing so is to cause dot expansion, dark tone paste, color deviation, or you can print a lighter color first to achieve the purpose of bottoming. Therefore, color newspaper must use paper with high smoothness

Second, the whiteness of paper

paper is the carrier of graphic information, and its whiteness directly affects the color of printed matter. After the light shines on the paper, it will be absorbed, and the amount of absorption 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 pigment subtraction and chromatic light addition. If the whiteness of the paper is low, it absorbs too much light, and the color of the ink cannot be brought into full play, which affects the hue, lightness and saturation of the image color, resulting in gray color, poor contrast, rigid picture, no vitality and few layers

III. ink absorption of paper

ink absorption of paper includes the transfer and penetration of ink to paper. It depends not only on the absorption ability of paper to ink binder, but also on the absorption of ink by paper under embossing conditions. Therefore, ink absorption should be the comprehensive reflection of the performance of paper (paper) and ink under printing conditions, that is, the quality of ink absorption does not completely depend on the performance of paper, It also depends on the performance of the ink and the printing conditions. When the paper is fixed, changing the performance of ink or printing conditions will change the ink absorption. Ink absorption directly affects the drying speed of the ink on the paper surface, and also affects the color effect and conjunctival fastness of the ink. The essence of ink absorption is the comprehensive reflection of the absorption and adhesion of paper to ink in the printing process. It is not only related to the surface properties, porosity, compressibility, adsorption, etc. of paper, but also related to the composition, rheology and dryness of ink, as well as the printing method, printing pressure and stamping time

the smoothness of paper is low, and it is impossible to get a large amount of transfer under the condition of less ink supply. When the ink supply is large enough, the ink layer contacts the paper surface at the moment of imprinting, and a large amount of ink transfer can be obtained. Therefore, the amount of ink transfer varies with the surface properties of the paper. 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, so as to meet the amount of solidified ink required by different papers and the amount of free ink required to cover the surface, and the amount of ink split on the paper

during the transfer of ink to paper, the binder of ink undergoes physical and chemical changes on the surface part through absorption and pressure penetration, forming a solid dry ink film. If the ink absorption of the paper is too large, the ink absorption is large. Too many binders and parts harden the soil, and the pigment particles are sucked into the interior of the paper, so that the pigment particles cannot be effectively protected, resulting in weak imprinting, powdering, drying, dim ink color, reducing the brightness of the color, and at the same time, the saturation and hue are also affected to a certain extent. Small ink absorption results in thick ink film and high field density, which is conducive to color reproduction. If the ink supply is too large, it is easy to cause dirt on the back. Web offset presses mostly use paper and the printing speed is fast, so the ink absorption ability of paper is strong

IV. surface efficiency of paper

the color effect produced after the ink is transferred to the paper mainly depends on the nature of the ink, but it is also inseparable from the nature of the paper. Using the same ink to print on different papers, not only the color intensity and contrast are different, but also the color deviation and gray scale are very different. Even if printed on both sides of the same paper, the color effect is also different. This is because the absorption and gloss of the paper surface are different

the surface efficiency of paper is mainly more than 700 projects. The absorption and gloss should be considered when signing, starting or putting into production. The absorption of paper is mainly the strength of liquid absorption capacity, and the absorption of ink is mainly the absorption of binder in ink. The color effect of ink is formed after a certain amount of ink is consolidated on the surface of the paper, but the absorption degree of the paper to the ink or the binder in the ink layer is different, which causes the gloss, color density and hue of the ink layer on the paper surface to change, and the strong absorption will change greatly; Small absorption leads to small change. Glossiness is the degree of specular reflection of the optical properties of the paper surface. The gloss mainly depends on the roughness of the paper surface and the properties of the substances that make up the paper. When the ink is dry and colored on the paper surface, its continuity and uniformity after drying the conjunctiva must be affected by the paper surface state, 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 deviation and gray scale are the smallest. Otherwise, the color intensity of the ink layer is low, and the color deviation and gray scale are relatively high, resulting in the difficulty of color overprint gray balance

paying attention to the surface efficiency of paper is of great help to improve the quality of color newspaper printing, because the surface efficiency of paper can provide powerful data for some quality problems, which is conducive to finding the causes of problems. In the process of plate making and printing, the color deviation and gray scale of the ink color are effectively corrected according to the surface efficiency of the paper, so as to achieve the gray balance of color superposition and reduce the factors affecting the color quality

v. mechanical strength of paper

for web offset press, due to the reasons of paper pulp. Its mechanical strength is an important factor affecting the printing quality. This is mainly reflected in two aspects: tensile strength and surface strength. The paper path of web offset press is generally long. In the process of high-speed printing, the tension of each part of the paper path is different and varies greatly. Once the tension exceeds its tensile strength, the paper will break, affecting normal printing. The surface strength of paper is another important technical index. During the printing process, when the ink splits between the paper and the blanket, the peeling tension is generated due to the tension of ink adhesion and the adhesion between the blanket and the paper. When the peeling tension is greater than the surface strength (the internal binding force perpendicular to the paper surface), the paper tape will peel from the middle and wrap around the rubber drum, resulting in paper breakage and crushing of the rubber blanket. The paper surface is subject to the action of peeling tension to produce powder and wool, which are accumulated on the blanket. When a certain amount of paper is printed, the accumulation of paper powder and paper wool is too thick, which will make the impression false and untrue, and the small text will break the pen, which will seriously affect the printing quality. In addition, due to the increase of pressure, it will cause plate grinding and reduce the service life of the blanket. For color newspaper, the ink layer transferred to the paper surface is reduced. The color is dim, lack of hierarchy, and the point is seriously enlarged. Due to the wet stacking and wet transfer of ink in the printing process of color newspaper, there is also wet hair loss. Therefore, when printing color newspaper, in addition to using paper with high surface strength, corresponding technological measures should be taken to use ink with low viscosity to appropriately reduce the printing pressure and printing speed

VI. dimensional stability of paper

paper is woven from plant fibers with a turn-off buzzer. Its surface is porous, hydrophilic and hygroscopic. Its water content has a great impact on its dimensional stability. In the process of color newspaper printing, it is necessary to contact water many times, resulting in changes in dimensional stability. Dimensional stability not only directly affects the smooth progress of printing production, but also affects the quality of printed matter. The change of dimensional stability includes the expansion and contraction of plane size and the change of shape. The moisture absorption of paper is strong, so the dimensional stability is poor. Under different external conditions, the dimensional stability is different. For paper, due to its poor mechanical performance and stable size, it is of great significance for the smooth printing process and obtaining high-quality prints. Otherwise, it will cause problems such as paper interruption in the printing process, printing wrinkles, inaccurate overprint, etc. During the transportation and storage of paper, the temperature and humidity must be well controlled to avoid large changes, otherwise it will have a great impact on the dimensional stability

in a word, paper, as an indispensable printing material in newspaper and periodical printing, must be paid enough attention to its performance, so as to provide due material guarantee for ensuring the normal progress of printing and production for seven years of college time and obtaining high-quality printing materials

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