In the use of flexible packaging, whether compounded or not, almost all of them must be printed, so the function and influence of printing ink must not be ignored. If its properties are not understood in advance, it will often cause major accidents.
Plastic printing inks are divided into two categories: gravure inks for surface printing and gravure inks for composite printing (inside printing). Surface printing is generally used for non-transparent films, such as various colored films, paper, aluminum foil, etc.
According to the current situation at home and abroad, generally single-layer polyethylene films (including LDPE, MDPE, HDPE, LLDPE), EVA films and non-stretched polypropylene films can be processed by surface printing, and generally in tube film rolls Most of them are printed in the form.
In addition, as long as the transparency of other films and cellophane allows (even surface PE printing films used as composite toothpaste tubes), they are all printed on the inside. This is because printing on the inside can not only bring out the ink color more It is bright and smooth, and can also protect the ink surface.
Surface printing ink, as the name suggests, is applied to printed matter whose printing surface is directly exposed to the outside. Therefore, it is particularly required to have the following characteristics.
① Strong wear resistance and scratch resistance.
② It has heat resistance that can withstand high temperatures during heat sealing.
③The appearance requires good gloss.
Internal printing inks are generally used for composite films. Since the ink is partially sandwiched between the printing film and another layer of composite film, it only requires the so-called special durability of composite adaptability, such as composite strength, AC for composite use. The affinity and bonding properties of primers and various adhesives, etc., while the wear resistance, scratch resistance and gloss required for surface printing are almost not required. This is the difference between the two.
