At present, most products are produced by gravure printing. The quality of gravure printing products will be affected by many aspects such as film, ink, printing ink, printing roller, equipment and production workers. The following will briefly discuss some points of the gravure printing process quality control.
Commonly used flexible packaging printing substrates are usually the following: Biaxial stretching BOPA, BOPET, BOPP and derived films (such as: K coating, matting film, pearl film, heat sealing film, glass evaporated film, etc.). Unstretched PP, PE film. PP, PE or PVC shrink film. Cellophane or plastic tear film. Other plastic film or paper. Different printing substrates, their printing, composite adaptability varies, in the printing need to choose a different production process in order to achieve better quality.
BOPP is the most commonly used printing substrate. It is printed with polyamide or chlorinated polypropylene ink. With suitable tension and embossing force, the drying temperature is controlled below 80°C. BOPET printing points: Because PET is usually thin, easy to wrinkle, need a larger tension when printing, the ink has a certain degree of selectivity, easy to use the general printing ink layer, the film static electricity, prone to block version (not access to the Internet ), fluffing and knife marks (knife wire) phenomenon, printing workshop humidity is good.
BOPP printing points: BOPP is a film that absorbs moisture easily. It is necessary to ensure that the environmental humidity of the printing machine cannot be too high (if it is not dehumidified, it is not suitable for Indonesian film in the environment with high humidity); immediately after opening, the nylon film must be preheated (if There is no preheating device on the machine table. The plate can be mounted on the second color and the first color can be used as a preheating.) The preheating temperature is 50~80°C; the printing tension should be properly reduced to make the ink adaptable. Depending on the choice of different product structures, if it is a cooking bag, cooking ink must be selected; after printing, the finished product must be sealed and placed in dry complex indoor storage and stored as soon as possible.
K coating film (KOP, KPA, KPET) printing point: Because K coating film is roller coating type or spraying type, its thickness uniformity is not very good, the surface is uneven, and PVDC is just brittle, when printing The printing tension and the imprinting pressure cannot be too large, the overprinting is difficult, the ink transferability is poor, and when printing a light screen plate, it is easy to get a flower point (parts of the network points are lost), and a higher hardness press roller is used for printing. The solvent must be selective. If the solvent is used improperly, the coating may be dissolved. The residual amount of the solvent in the printing film is relatively large, and the adhesion is easy. Therefore, special attention should be paid to drying and cooling.
The printing of an extinction film can be done using OPP's process, and printing is performed on the glossy surface. However, because the matt layer on the surface cannot withstand high temperatures, the drying temperature needs to be controlled. Pearl film using table printing ink for printing, try to use a good transparency printing ink. The heat shrinkable film should be printed with a very low drying temperature. Special heat shrinkable ink should be selected (the printed ink layer should be able to shrink without falling). If it is a PVC heat shrinkable film, consider the solvent to dissolve the film. Sex.
The tension of unstretched PP and PE films is very small when printing, and it is difficult to overprint. The amount of deformation of the printing should be fully taken into consideration when designing the pattern. For different printing substrates, adjustments must be made in ink selection, plate design, and printing process to ensure that the quality of the product meets the requirements; in addition, some high barrier coating materials are not printed on the coating as much as possible under the conditions. To prevent damage to the barrier coating.