Analysis of electrostatic failure in gravure printing process
Electrostatic phenomena
As the substrate is mostly paper, plastic and other insulating materials, it is easy to generate static electricity and can not escape. The ink itself also has static electricity. With the accumulation of electric charge, a series of electrostatic faults will be caused, which are shown in the following aspects.
Electrostatic speckle phenomenon. It mainly appears in the printing of polyolefin film, and some irregular stripes are formed in the large area pattern part.
Electrostatic burr phenomenon. A linear "beard" appears around the line.
Electrostatic repulsion leakage phenomenon. Such as in some words around the white ink when the bottom caused by the exclusion of the gap.
The phenomenon of electrostatic dust collection. Adsorption of dust impurities in the air, reduce the transfer rate of ink, in the graphics and text appear dot. (especially the shallow net part)
Electrostatic discharge phenomenon. When the static electricity is serious, it will cause air discharge, cause fire and cause serious accidents.
Causes of static electricity
Friction electrification. Friction creates an electric charge through high-speed printing equipment.
Ink after a long period of running charge, especially when using non-polar solvents.
Countermeasures for electrostatic elimination
Control the humidity, the general relative humidity is about 65%.
Ground. The most direct method is to connect the metal body with the earth, and the electric charge will leak through the earth. For example, install a carbon fiber brush to make the film contact with it and ground to eliminate static electricity.
In the ink to add an appropriate amount of antistatic agent, add polar solvents, such as methyl ethyl ketone, isopropanol, etc.
Proper increase of ink viscosity can reduce static failure.
Electrostatic eliminator collector, commonly used in paper printing.
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