Coating Defects
Conventional films are divided into two types: coated and uncoated. There are also two corresponding situations where film coating defects cause ink rub-off. For coated film materials, if the surface coating has poor adhesion, it will result in poor ink adhesion. For uncoated film materials, ink rub-off often occurs because the adhesion between the surface layer and the ink is not good.
To solve the problem of ink rub-off caused by coating defects, we can take the following measures: apply a surface varnish printing treatment to protect the ink surface and prevent ink rub-off; perform corona re-treatment on the surface layer. The corona dyne value of the material surface should be not les than 38 mm/m. If the dyne value is lower than 36 mm/m, it will directly affect the adhesion of the printing ink.
Applying a primer on the surface layer or using an enhancer with strong ink adhesion (the mixing ratio is about 3%) can also improve the ink receptivity of the film surface layer. Some matte synthetic paper materials are not suitable for detection with 3M tape because their surface coatings have certain characteristics of paper coatings.
Tension
For film materials with corona-treated printing surfaces, to achieve good ink wetting, the dyne value usually needs to be above 38 mm/m. If it is lower than 36 mm/m, ink rub-off problems are likely to occur. At the same time, the dyne value of such materials will gradually decrease over time, resulting in printing ink rub-off problems. The essence of this problem is the tension problem.
Ink Drying and Tension
During the printing process, the reasons of ink drying and tension may also cause ink rub-off. Specifically, the printing ink layer is too thick, resulting in incomplete drying; the energy of the UV lamp is insufficient, the lamp tube is aged, and the reflector of the lamp tube is aged, resulting in insufficient drying and curing of the UV lamp and the ink layer is not dry; the ink is overly dried, resulting in material deformation and ink layer peeling.
Matching of Ink and Material
The degree of matching between ink and material can also cause ink rub-off to a certain extent. For example, if the molecular tension of the ink is too large, a uniform ink layer cannot be formed on the surface of the substrate material; or if the ink model that has exceeded the expiration date or inferior domestic brand ink is used, printing ink rub-off will occur.
Post time: Dec-31-2024
