The relationship between the characteristics of coated paper and printing quality (4)
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(7) Surface peeling (Picking)
In the case of relief gravure printing, the adhesion of the ink is low, and there is little peeling. In the lithographic printing, the ink has a high degree of adhesion, strongly acts on the paper surface, and the addition of moist water during printing destroys the hydrogen bonding of the paper surface, which is liable to cause peeling. The degree of adhesion refers to the amount of force generated when the ink is separated from the blanket and the paper. The surface of the paper needs to have a force against the adhesion, so various papers are added in the paper. Treatment of surface strength.
(8) Differences in the table
If the double mesh Hybrid forme is used to manipulate the paper, the difference in the surface can be greatly reduced.
(9) Moisture
The paper is made in water and is very hydrophilic in chemical structure. It is easy to absorb moisture, release moisture, and stretch when it absorbs moisture. Therefore, it shrinks when wet, that is, it lacks dimensional stability and often causes paper diseases such as curling, waves, and shrinkage. Side (Tight Edge) and so on. The equilibrium moisture content of the paper is affected by the paper grade and atmospheric humidity. In general, 1/10 of the relative humidity is the equilibrium moisture content of the paper. Paper with too low moisture content absorbs moisture, which may cause the paper to curl and wave, which may cause the paper machine to work poorly and the paper feeding is poor. In addition, if the moisture is too high, it will be wetted, causing the paper to curl, shrink, and the printing appearance is not good, resulting in problems such as the texture. However, the congenital size of this paper is not stable and cannot be completely removed. Therefore, the humidity and temperature of the printing plant and processing plant are very important. It is necessary to have proper temperature and humidity to adjust the environment.
(10) pH value
The neutralization of the printing paper, the storage of the paper pH on the paper, and the drying of the printing ink and the emulsification of the moist water have a great influence. In other words, when the pH of the paper is 4 or less, the components in the ink react with the metal component of the dryer to form a specific compound. When the pH is 6 or more, the emulsification of the wet water and the ink is promoted, and the scumming is caused. Therefore, the pH of the generally moist water is controlled to about 5.5.
In addition to the above 10 impact factors:
(1) Whether it will wear on the plate
(2) Is there any static electricity?
(3) Compressibility and elasticity
(4) Whether it is a flat paper disease is an impact factor.
Second, the factors affecting printing are as follows:
(1) Flatness
Good printed paper should be free of wrinkles, waves and curls:
(2) Cutting
Must be the correct size and square.
(3) Foreign bodies
Foreign objects such as loose paper, pigments, fibers, etc., must be removed from the paper manufacturing process.
(4) Moisture content or relative humidity
The relative humidity of the paper must be the same as the operating environment.
(5) Resistance to surface pull-up
The surface strength of the paper must be sufficient to resist peeling of the surface during printing, resulting in poor handling.
(6) Water resistance
With moderate water resistance, it can adapt to the wetting effect of lithography.
(7) Ink affinity
Good affinity helps the ink function on the paper.
(8) The shape of the paper should be very complete without any small holes, scratches, creases and impurities. The paper roll should be tightly wound and the edges should be flat, and there is no paper disease.
(9) No static electricity
(10) Not wearable Does not wear the plate.
Whether the quality of coated paper is good or not, in addition to the great influence of the quality of the original paper, the composition of the coating is also an important factor. When different types of organic pigments are added to the coating to replace the white pigment commonly used - clay The coated paper produced is proportional to the amount of organic pigment added in terms of whiteness, white gloss, printing gloss, opacity, smoothness, etc., which means that the organic pigment can improve the coated paper. nature.
When different types of organic pigments are added to the coating to replace titanium dioxide with high price, high whiteness and high refractive index, the coated paper produced is added with organic pigments in terms of white paper gloss, printing gloss and smoothness. The amount is proportional, but in terms of whiteness and opacity, it is inversely proportional to the amount of organic pigment added. This means that in some special applications, although organic pigments cannot completely replace titanium dioxide, the properties of coated paper can be maintained. A certain level will not differ too much.
When different types of organic pigments are added to the paint to replace the inexpensive and commonly used white pigment, calcium carbonate, the coated paper produced is whiteness, white gloss, print gloss, opacity, smoothness, All aspects are proportional to the amount of organic pigment added, which means that the use of organic pigments is an inevitable trend to further enhance the properties of coated paper.
In the relationship between the coating amount and the quality of the coated paper, when the organic pigment is added to the coating, the properties of the coated paper are better than those without the organic pigment, and when the coated paper is close in nature, organic is added. The coated paper of the pigment can reduce the amount of coating. When the organic pigment is dense, the coating amount can be reduced by about 30%, and the organic pigment of the subsequent type can be reduced by about 40%. If the organic pigment is hollow, the coating amount can be reduced by about 45%. This means that in the trend of paper lightweighting, organic pigments can bring considerable help.
The quality of printed matter has a great relationship with the printed materials, and the quality of the printed materials is closely related to the original paper, paint and surface treatment. Therefore, choosing a sinister paper as the printed material is a cost saving and improvement. The only way to print quality.