1.1 ink adhesion mechanism
Wetting: adhesion fastness is the result of the interaction between the molecules of printing substrate film and ink binder.
Compatibility: ink connecting material and substrate polarity close, good compatibility. (be sure to choose the ink that matches the printed matter)
1.2 causes and Countermeasures of poor adhesion
Substrate factor.
a. The corona treatment degree of the substrate surface is not enough, the tension is not reached, or the treated substrate surface is invalid due to poor storage environment and long storage time. It is generally required that the surface tension of PP and PE should be ≥ 38mn / m, pet ≥ 50Mn / M and NY ≥ 52mn / m. The surface tension of each batch of films should be checked before use.
b. Most of the base materials are added with certain lubricants, antistatic agents, moisture-proof agents, etc. these additives gradually penetrate into the surface of the film over time, forming a weak interface layer on the surface of the film, which affects the ink adhesion. Therefore, the film should be used within the validity period, and the surface tension should be tested before use. It can be tested with dyne pen.
Substrate factor
The factors of moisture absorption of substrate. For example, PA, PVA, Pt and other materials are easy to absorb moisture and reduce adhesion. Such substrates should be stored under good conditions (controlled temperature and humidity) and fully preheated before use.
The wrong type of ink, mixed with different types of ink. There are many kinds of gravure inks, including surface printing ink and inner printing ink. Different materials correspond to different inks. All kinds of special inks must be used correspondingly. Otherwise, the adhesion fastness is not enough. The operation process instructions should be checked before production.
Ink whitening. Ink deterioration, whitening makes adhesion extremely reduced.
Ink drying is not sufficient. In addition, a certain drying temperature is very beneficial to improve the adhesion of some resin joint materials.