The ink layer of printed matter mainly refers to the properties of paper, ink properties, ink layer thickness, surface and integral density of printed pictures and texts. Their influence on the quality of film coating is mainly the influence on the adhesion strength between printed matter and film.
1. ink layer thickness. When the ink layer is thicker and the area is larger, these inks change the surface characteristics of the paper pores, close many paper fiber pores, hinder the penetration and diffusion of adhesive, making it difficult to bond the printed matter with plastic film, easy to occur delamination, bubble and other faults.
2. the role of ink diluent. Commonly used ink thinning agents are white ink, virgin oil and bright paste. Among them, white ink has obvious powder particles, which do not bond tightly with the binder. After printing, these pigment particles will float on the paper surface, which hinders adhesion. Villey oil is rolled by aluminium hydroxide and binder. Because aluminium hydroxide is light, it often floats on the surface of the ink layer after printing. When coating, an isolation layer is formed between the binder and the ink layer, resulting in no bonding or bubbles. The light paste is made of resin, dry vegetable oil and drier. Its texture is fine and its conjunctiva is bright. It has similar properties with conjugated terpene resin as the main component of the film adhesive, they have good affinity, can be firmly adsorbed on the surface of polypropylene film ink.
3. add and put dry oil. Dry oil can speed up the drying of printing ink, but the large amount of dry oil can easily make the surface of the ink layer into a glossy and smooth low-interface D layer, the adhesive is difficult to wet and penetrate, affecting the fastness of the film, therefore, to control the amount of dry oil.
4. powder powder. The offset printing adopts powder spraying process to avoid the dirty print, and a layer of fine particles is formed on the surface of the powder spraying ink layer. When the film is covered, the adhesive is not the ink layer everywhere, but with these powder bonding, forming a false adhesion phenomenon, seriously affecting the quality of the film. Therefore, to coat the product, should avoid the use of powder spraying technology, powder has been sprayed on the printed matter, the application of dry cloth to wipe off powder one by one.
5. gold and silver ink prints. Jin Yinmo was made of metal powder and a binder. The uniformity and fixation of these metal powders in the binder are very poor, and the ink layer can be easily separated during drying. These separated metal powders form a barrier between the ink layer and the adhesive layer, affecting the effective bonding of the two interfaces. After placing this product for a period of time, wrinkles and bubbles will appear. Therefore, the coating of gold and silver ink should be avoided.
6. drying condition of printing ink layer. When the ink is not completely dried, the high boiling point solvent contained in the ink can easily make the plastic film swell and elongate, which is the main reason for the bubble and delamination of the product after coating. The full drying of the ink layer is the first condition to ensure the quality of the ink. For products that are imprinted and used for ink coating, they can be dried.