After the PET film is printed with the pattern design according to the gravure printing method, it can have the function of cleaning the product packaging, and has an excellent publicity and planning function for the product. However, the most common polyhydrocarbon plastic film materials (PE, PP, modified polyolefin, etc.) belong to non-polar high polymers, and their surface free energy is very low, only 2.9~3.0×10-6J/cm2 . Theoretically speaking, if the surface free energy of a certain type of object is less than 3.3×10-6J/cm2, it is basically impossible to attach any known adhesive at this stage. Therefore, in order to obtain a certain packaging and printing fastness of the ink on the surface of polyolefin, it is necessary to increase its surface free energy. According to the current processing technology regulations, it should be 3.8 ~ 4.0 × 10-6J/cm2. So far, the most widely used plastic film solution in the world is corona treatment.

  Because corona treatment is generally carried out in the air, under the impact standard of high voltage and high frequency spark discharge, on the one hand, weak electrolytes are formed in the gas, resulting in various polar functional groups; on the other hand, in the molecular formula of polyene The double chain, especially the double chain on its carbon bond, is easier to open. In that way, at the instant of solution, various polar functional groups undergo grafting reaction with the polymer surface, thereby changing the polyolefin surface from non-polar to polar surface. It can be said that the surface of the polyolefin after the arc discharge solution has a thickness of about 10-10 meters has become a polar chemical substance that is completely different from the original polyolefin structure, and the surface free energy is further improved. Reach 3.8～4.0*10-6J/cm2. In addition, the high-voltage and high-frequency spark discharge will roughen the surface of the plastic film material according to the impact (observed with a high-magnification transmission electron microscope, you can see the unevenness of small grooves on the surface), thereby improving the wettability of the ink. and total touch area. Therefore, the adhesion fastness of ink on its surface is improved by the action of organic chemistry and physics.