Compared with corona pretreatment, the reason why the coating pretreatment of heat transfer film can keep the treatment effect stable for a long time is that corona pretreatment can only produce a very thin functional layer, while the coating thickness produced by coating pretreatment is 0.5 microns to several microns, so many factors that lead to the decrease of surface energy after corona pretreatment do not exist.

On the one hand, the coating is like a barrier layer, which can block the migration of additives to the film surface; On the other hand, the layer remains active for a long time on the film surface.

The question now is, is pretreatment of coating really necessary? Because most printing machines can be equipped with corona treatment devices nowadays, it is theoretically possible to print thin film materials without pretreatment coating.

Printing plants often encounter a phenomenon: if some substances and impurities affecting ink adhesion are deposited on the surface of heat transfer film, or when ink and pretreatment coating are incompatible with each other, ink peeling will occur. Our experience shows that if there is poor adhesion of ink in the printing process, the film material pretreated by coating can also be solved by corona treatment before printing.

The difference is that after corona treatment, the film pretreated by coating can achieve a more perfect printing effect, and the uniformity of printing ink is obviously better than that of the film material without coating pretreatment. In addition, the film pretreated by coating can make the ink adhesion reach a higher level only by simple corona treatment, because corona treatment at this time can make the pretreated coating have great similarity with ink in chemical properties.

In a word, due to the structural characteristics of heat transfer film, surface pretreatment is needed to achieve good printing process and quality. Pretreatment coating can not only improve the long-term stability of label printed matter, but also produce value-added effect for printing plants, because the fluctuation of film materials’ performance will not affect the printing results, and film materials of different materials can be changed at will, without having to adapt the printing process to the film materials.

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