1. Appearance Strength of Copper Plate Paper
The surface strength of coated paper refers to the separation strength between coatings particles and coatings and base paper. It is an important performance index of coated paper, which is usually expressed by the drawing speed. When the surface strength of copperplate paper is low, it is easy to produce wool and powder dropping in the printing process. With the stop of printing, more and more paper wool and powder will accumulate on the plate, which will eventually lead to lithography and affect the printing quality and operation. Therefore, it is necessary to improve the appearance strength of copperplate paper to ensure good printing effect.
2. Moisture and Temperature Resistance of Copper Plate Paper
The moisture content of the copperplate paper refers to the percentage of the moisture content in the copperplate paper to the weight of the copperplate paper. With the development and progress of society, the printing industry has also developed by leaps and bounds. The appearance of commercial rotary printing presses has put forward new requirements for the temperature resistance and moisture content of printed copperplate paper. If the moisture content is inappropriate and the temperature resistance is poor, the blistering phenomenon of copper plate paper in printing will become a more serious and common problem in rotary printing.
Because of the high-speed printing characteristics of rotary printers, 40,000 to 50,000 sheets per hour are common (and the fastest speed of ordinary sheet paper printing is less than 20,000 sheets per hour). When printing is dull, direct folding is stopped. At such a high speed, in order to avoid printing abnormalities such as non-drying ink and negative stickiness, printing is required. Brush ink is dry and fast, and the most effective way to make ink fast and dry is high temperature heating, so in the construction of rotary printing machine, there is an oven to stop heating the printed copperplate paper, so that the ink can be fast and dry.
Quantitative moisture in copperplate paper is released into water vapor when it is dried at high temperature (usually about 140 C). Because there are coating layers on one or both sides of copperplate paper, and because of the effect of binder and crosslinking agent in the coating, it can prevent hair and powder from falling off in the printing process, but it can be used for printing. In the process of ink drying, water vapor is unfavorable to the outward release; if the same position on both sides of the paper happens to be full-page printing, and the amount of ink is very large, because the ink will completely cover the paper surface, further cause water vapor can not be released out, it will produce bubbling phenomenon.
In order to prevent blistering in printing, the following three points should be paid attention to when choosing and using copperplate paper:
(1) Choose copper plate paper with good heat resistance.
(2) Copper plate paper with moisture content between 6% and 8% was selected. If the moisture content of copperplate paper is too high, it will not release the water vapor in the printed matter with coating and ink quickly in a short time, thus forming bubbles; if the moisture content is too low, the paper will easily produce static electricity, and tend to be brittle and hard, which is not conducive to printing; if the moisture content is not equal, it will form tight edges, lotus edges and rolls. Song and so on.
(3) Temperature of copper plate printing workshop should be controlled at 18-25 C and relative humidity should be maintained at 50-60%.
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