Printing characteristics of the most popular coate

2022-08-26
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Printing characteristics of coated paper and coated paper

the name of coated paper is relative to uncoated paper. According to the way of paper processing, the paper whose surface has been coated and calendered is called coated paper. Figure 1 and Figure 2 show the sectional structure of uncoated paper and coated paper respectively. If you observe the paper surface of the two kinds of paper under the microscope (as shown in Fig. 3 and Fig. 4), you can clearly see that the uncoated paper fiber is thick and long, and the micro smoothness of the surface is very poor. Therefore, it has strong ink absorption, and is generally used to print printed matter with lines or thick lines

after the paper is coated, the smoothness is significantly improved, creating conditions for fine dot printing. Because the micropore of the coating is much smaller than that of the fiber layer, the ink absorption of the paper surface is significantly reduced, so that the ink is printed on the paper surface, and the liquid binder is solidified into a film after leveling before a large amount of infiltration into the paper. The paper surface is flat, and the ink film is flatter, which has good printing gloss, printing density and clear printing points, making the printed picture page bright in color, rich in layers and strong three-dimensional sense. The printing gloss and uncoated paper are generally less than 25%, while the coated paper can reach up to about 95%. Therefore, coated paper is most suitable for printing color and fine line prints. It is one of the paper types with large consumption of printing paper at present

I. types and uses of coated paper

coated paper, commonly known as coated paper, has many kinds and can be used for the printing of various color printing materials

1. Single sided coated paper

is coated and calendered on one side and glued on the other side. The properties of both sides of the paper are different, which is suitable for printing on both sides. For example, the coated surface is used for color printing, and the uncoated surface is used for monochrome printing

2. Double sided coated paper

is coated and calendered on both sides, with glossy bottom and good dimensional stability. It is suitable for general color printing

3. Super double-sided coated paper

is coated and calendered on both sides. It has better gloss than general double-sided coated paper, and its surface is smooth and fine. It is suitable for the printing of bright objects that need to show metal texture

4. High grade snow (matte) coated paper

is coated and calendered on both sides, but the gloss of the paper is low, and the powdery surface is not harmful to the eyes. It is suitable for the printing of non reflective items such as traditional Chinese painting reproductions and clothing fabrics, giving people a sense of simplicity and elegance

5. Xinli 2000 super coated paper

is coated twice on both sides and then calendered. It has good gloss and smoothness, and is suitable for the printing of advanced color printing. 6. Embossed coated paper coated on both sides and embossed (see Figure 5 and Figure 6). The gloss of the paper is low. Due to the embossing, the paper has a three-dimensional sense, which is suitable for the reproduction of oil paintings, the matching of domestic instruments with foreign technology, and other ways to achieve the effect of "market for technology", such as color printing such as design

7. Light weight coated paper

the surface is slightly coated, which has better surface properties than uncoated paper. The quality is between coated paper and uncoated paper. It is produced for printing materials with different needs, such as pictorial, advanced pictorial, ivory Daolin, snow white Daolin and magazine paper

(1) the surface of pictorial paper is slightly coated, which has better surface properties than uncoated paper. The paper has high whiteness, but low gloss, with a sense of elegance. It is suitable for color printing with higher line than offset paper

(2) in addition to a small amount of paint treatment, the surface of advanced pictorial paper is also treated with pressure light, making the paper smooth and delicate. It is suitable for the printing of fine print. However, due to the reduction of pores on the paper surface after calendering, it has the characteristics of low ink absorption and high ink retention

(3) the surface of ivory forest paper is slightly coated. The paper surface is soft ivory white, with fine and smooth texture. It has good readability and gives people a high-level feeling. Suitable for printing books, advanced books and other printed materials

(4) snow white forest paper is micro coated on both sides, with smooth surface and high whiteness, which can be stored for 100 years without discoloration. It is suitable for printing high-level business logs, books, magazines and other printed materials

(5) the surface of magazine paper passes through 4. Cooler: the crud of air-cooled cooler should be cleared regularly; If water cooling is adopted, regularly inspect whether the cooling copper pipe has cracks and water leakage; Lightly coat the cloth of diplodendron, Dendroctonus (non Chinese species), Dendroctonus (non Chinese species), Dendroctonus (non Chinese species) and Dendroctonus (non Chinese species) respectively, and then press polish. Thin paper, high opacity. The gloss

increased significantly after printing. However, because it contains ground wood pulp, the paper is easy to turn yellow, which is suitable for printing magazines, books and periodicals and other printed materials

second, ink absorption

paper is a porous material interwoven with fibers. The basis for paper to absorb ink is the pores formed by fiber networks. Therefore, the absorption capacity of paper to ink determines the permeability of paper to ink. Many printing failures are often caused by the incompatibility between the ink absorption of the paper and the printing conditions used. Accurately evaluating the ink absorption ability of paper and predicting the impact on printing quality is very important for the improvement of paper quality and the control of printing quality

the most reliable method to evaluate the ink absorption ability of paper is the k n ink test method, which has been determined as the standard test method of ink absorption of paper in China

the test method is as follows: coat the excess k n ink on the surface of the paper being tested (the goal of K PPG Industrial Company is to continue to maintain its position as the world's leading supplier of coatings and special materials. N ink is a non dry ink formed by dispersing white pigments in colored oil), keep the ink on the surface of the paper for a certain time, and wipe off the excess ink with soft skin or absorbent cotton, Then measure the reflectivity of the dirty area and the reflectivity of the clean paper respectively. The test results are expressed by K n value, which can be calculated by the following formula: K n=r f/r ∝ × 100% in the formula: RF - reflectivity of ink dirty area; R ∝ - reflectivity of blank paper (i.e. clean paper). Table 1 the characteristic whiteness (%) gloss (%) k n value (%) 128g/m 2 Japanese coated paper 82.2 62.1 16.8 128g/m 2 Beijing coated paper 81.9 60.6 30.8

it can be seen from table 1 that the ink absorption of Japanese coated paper is much smaller than that of Beijing coated paper, although the whiteness and gloss of coated paper with the same quantity have little difference. If the ink with the same viscosity is used and printed under the same printing conditions, Beijing 128g/m 2 coated paper will cause the gloss of the imprint to decline, the ink color to be dim, and even the failure of "through printing" due to the excessive absorption capacity of the ink. For Japanese 128g/m2 coated paper, due to the small absorption of ink, the drying speed of ink slows down, resulting in the phenomenon of "back rubbing dirty". If the ink absorption capacity of the paper is measured in advance, the printing process can be adjusted to avoid this phenomenon

each kind of paper must have the absorption property that matches the printing method and printing conditions in order to obtain a firm, clear and fresh impression. For example, offset lithography uses mostly resin inks, and its drying on paper depends on the oxidized conjunctiva of the ink binder. Therefore, only the paper has weak absorption, can we avoid the excessive penetration of ink binder and even pigment, and make the paper get a bright and bright ink film. However, if the absorption is too poor, although the printing quality is good, it is easy to cause the paper to be sticky and dirty during printing, which affects the graphic printing effect. Therefore, the xylene absorption of the paper is generally controlled at s, and the printing effect is better. (Note: xylene absorption test is a standard test method once stipulated in China. This method is to drop a drop of xylene solution on the paper surface on a special test stand, and measure the time required for the drop to be completely absorbed by the paper surface and the gloss of the drop to disappear, with the result expressed in seconds)

gravure printing uses volatile inks with low viscosity. The ink viscosity is low. Depending on solvent volatilization, the resin forms an ink film on the paper, so the absorption of gravure printing paper is better to be weak. However, if the ink absorption speed is too slow, it will make the paper and the printing plate in close contact, resulting in nowhere to penetrate the ink and produce spots or unclear layers, resulting in sticky dirt in multicolor printing

the graphics and texts on the copper zinc plate are convex and under high pressure. The ink binder is composed of nonvolatile mineral oil. The fixation of the ink on the paper mainly depends on the ink absorption performance of the paper. Therefore, the paper printed with copper zinc plate should have good ink absorption performance, so that the ink can quickly adhere to the paper

III. surface efficiency

the surface efficiency of paper is not a single optical property, it is a printability related to optical properties that affects the printing quality

under the same printing conditions, the same ink is printed on different papers, and the color change is mainly reflected in the difference of hue. There is a close relationship between the hue of ink on paper and the surface efficiency of paper. We can know the hue shift through the surface efficiency of paper, and determine the quality of color reproduction of paper

surface efficiency (PSE) is a physical quantity that combines the gloss and ink absorption ability of paper to assess the quality of paper. It can be calculated according to the following formula: PSE (%) ={100-a (%) +g (%)}/2 where: PSE - surface efficiency of paper

a - ink absorption capacity of paper; G - gloss of paper

in the calculation, the ink absorption capacity a is calculated by the k n value of the ink according to the following formula: a (%) =4/3 (100-k n)

the surface efficiency of the paper can also be directly determined from Figure 7 by referring to the GATF surface efficiency diagram shown in Figure 7 by the value of ink absorption capacity A and gloss G. For example, if the ink absorption capacity a=10% and gloss g=10% of the paper are measured, the pse=50% of the paper can be found from Figure 7 Figure 7 GATF paper surface efficiency conversion chart 2 paper ink hue filter R G B color deviation (%) gray (%) color efficiency (%) paper surface efficiency (%) Beijing coated paper (128g/m2) y 1.68 0.11 0.04 4.3 2.4 95.54 64.90 m 0.64 2.13 0.08 27.3 3.8 83.10 C 0.22 0.64 2.29 20.3 9.6 81.22 Japanese coated paper (128g/m2) Y 1.65 0.11 0.03 4.9 1.8 95.76 72.65 m 0.65 2.20 0.08 26.9 3.6 83.4 C 0.20 0.66 2.50 20.0 8.0 82.8

it can be seen from the data in Table 2 that the color rendering efficiency increases with the increase of the surface efficiency of the paper; The color deviation and gray level decrease with the increase of paper surface efficiency

in order to apply the relationship between paper surface efficiency and hue to production, a relatively simple method is to use y (yellow), m (magenta) and C (cyan) inks used in production, print on various papers with the same thickness of ink film, and measure the color deviation of M and C inks, as well as the gray scale of M and C inks (the color deviation and gray scale of Y inks are relatively small, so they can be ignored), and give the paper surface efficiency and color deviation as shown in Figure 8 and Figure 9 Gray scale relation curve. In this way, after the printing workshop selects the paper, it only needs to measure the surface efficiency of the paper, and then check Fig. 8 and Fig. 9 to determine the color deviation and gray scale caused by the paper, so as to provide color correction data for prepress image processing. By controlling the surface efficiency of paper, paper mills can more comprehensively control the quality of paper and produce high-quality color printing paper

the surface efficiency of paper also has a certain impact on the tone reproduction of printed matter. Table 3 lists the tone reproduction performance of two kinds of paper

from the data in the table, it can be seen that the density difference between the two kinds of paper in bright tone is not very large, but there is a significant difference in the density value in dark tone. Considering the range of 0 ~ 100 tone reproduction, Nippon copper

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