1. Material properties
PET film is a plastic film material with low to medium surface energy. Surface pretreatment is required before printing to improve the surface energy or wetting ability, otherwise the firmness of the ink and ribbon is not good and it is easy to fall off.
2. The basic method of surface pretreatment
a. Corona treatment
The surface of the material can be increased by high-voltage discharge. There are two methods: pre-treatment by the supplier when manufacturing the material and in-line processing on the printing press. The surface tension of the treated film is required to reach more than 38dyn. It should be noted that no matter how much corona current is used in some PET materials, the surface tension value cannot be increased, so in fact, few manufacturers use corona surface treatment, because the unstable quality will affect the printing of the ink in the later stage.
b. Surface coating
The surface of the material is pre-coated with affinity inks, such as corona-free PET film surface treatment agent and PET film surface treatment agent, to improve the wetting ability of the ink and increase the firmness of the ink. This treatment method is the most ideal, common and stable method for PET materials.
3. Printing quality assurance
a. The surface of the material must be pretreated and meet the standard.
b. Use matching special ink, and pre-test in combination with the actual production process.
c. Control the thickness of the ink layer. Drying should be thorough, and attention must be paid to the overprinting part of the ink to prevent the lower layer of ink from drying impermeable.