Paper is no stranger to us in our work. Generally, the paper we use has undergone static electricity elimination treatment, so we have no idea what harm static electricity can cause to paper. In fact, industrial paper is used for printing, packaging, etc. In fact, many problems can occur in paper manufacturing and slitting due to static electricity. Let's take a look at the effects of static electricity on paper from several aspects below.
I. Hazards of Static Electricity
1. Affect the printing quality of the product.
Firstly, the surface of the substrate is charged, such as paper, polyethylene, polypropylene, cellophane, etc. They will adsorb paper scraps or a large amount of dust and impurities in the air, thereby affecting the transfer of ink, reducing the ink transfer rate, and causing "flowers" to appear on the printed matter. "Point", or due to mutual repulsion, it may cause the winding to slip or be uneven.
Secondly, the ink is charged. This situation often occurs when the ink is at a relatively low viscosity or when the antistatic component in the ink is insufficient. If the discharge occurs while in motion, "electrostatic ink spots" may appear on the printed matter, looking as if the ink has poor fluidity and the ink application is very uneven. This situation often occurs in thin-plate printing with multiple layers. However, sometimes it also occurs in the on-site white version, and it also manifests as another phenomenon: rejection. Originally, the white ink was used as the base, but when encountering some characters (mostly black characters), a gap was formed around these characters, meaning the white ink could not print on that area. The main reasons are that the quality of the white ink is poor and its viscosity is too low. If the charged ink discharges at the edge of the lines on the printed matter, "ink whiskers" may occur at this point. This situation is more common in solid plates. In addition, the ink may also fog up due to being charged, causing serious pollution to the printed matter and the printing environment.
2. Affect production safety
In severe cases, charged substrates may even cause air discharge due to extremely high potential, resulting in electric shock or fire. Charged ink may cause the ink and solvents to catch fire or electrocut workers through the ink. In high-speed printing machines, many components generate a large amount of static electricity due to the strong friction during high-speed operation. For old-fashioned web-fed rotary printing machines with incomplete power dissipation devices, the voltage at certain positions on the machine can sometimes reach as high as 15,000V, and the current can also be around 100uA during high-speed operation. Such powerful voltage and current have a complex impact on the printing process. The harm is also quite serious, especially directly threatening the personal safety of the operators.
During the printing process, the paper on the paper pile is separated and conveyed forward under the friction between the paper feeding belt and the paper pressing wheel. Between the papers and between the papers and the machines, there is always a state of friction. Friction generates electric charges. When electric charges accumulate, paper becomes charged. When papers carry charges of the same polarity, they repel each other, resulting in inaccurate registration and uneven paper collection during printing. When the paper carries opposite charges, it causes problems such as empty sheets, double sheets, multiple sheets, and inaccurate registration during paper feeding. The surface of paper with static electricity is also prone to attracting some paper fibers and dust, which can cause problems such as mottled or spotted printed images. Therefore, it is very important to eliminate static electricity on the paper during printing.
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