Effect of Packaging Offset Printing on Post-printing Film

In packaging offset printing, many products require post-press processing. Among the many processes in the post-printing surface treatment are the lamination processing. However, during the processing, many quality problems will be encountered. Many of these quality problems are related to packaging offset printing. We say that the effect of the film is not only related to the material of the film and the process of the film, but there are many reasons related to printing. In order to guarantee the quality of the lamination process, we must analyze those factors related to quality, find out the reasons, and solve the quality problem. This article talks about the impact of packaging offset printing on the film.

The factors related to packaging printing are roughly: the ink layer thickness of the printed matter, the area of ​​the graphic, the nature of the ink being printed, the nature of the printing paper, the technical operation of the printing, and the like. These factors affect the mechanical bonding, physical and chemical adhesion. As a result, the adhesive properties of the film on the surface of the package print are changed and quality problems occur.

1. The thickness and area of ​​the ink layer of the packaged printed matter

Some packaging prints are large in graphic area and some are printed in the field so that the ink layers are relatively thick. Thick ink layers are often difficult to adhere to plastic film, and will soon be delaminated and foamed after bonding. This is because the thick layer of ink changes the porous surface characteristics of the paper, closing the pores of the paper fibers and impeding the penetration and expansion of the adhesive on the paper. The fastness of the film is greatly affected. In addition, the thickness and area of ​​the ink layer change, causing a change in the surface tension, thereby causing a change in the adhesive fastness. Therefore, we have to strictly control the amount of ink printed during the printing process. Control the field density. Compared with other printing, the ink layer of the package offset printing has the lowest thickness of the ink layer and is favorable for the coating, and is generally controlled at 2-3 μm.

2, packaging printing ink

Packaging film printing products should use fast-fixed bright offset ink. Because of fast-fixed bright offset printing inks, its binder is composed of synthetic resin, dry vegetable oil, high-boiling point kerosene, and the like. The molecular groups in these synthetic resins and the molecular groups in the cross-linking agent will expand and infiltrate each other, resulting in cross-linking, forming a physical and chemical bonding force, and being conducive to coating. In the application of packaging offset ink should pay attention to kerosene can not put too much, otherwise it will cause the ink to dry too fast, so that the ink surface crystallization, but affect the film coating effect. When printing light colors, it is necessary to add some thinner. Application of high-quality diluting agent. White oil is not used as an emulsifier. The inferior white ink has obvious silty particles that are not firmly bonded to the binder. After printing, the binder will penetrate the paper, and the pigment floating on the paper will hinder the adhesion. Virgin Oil is a paste-like transparent body made by dispersing and rolling aluminum hydroxide and dry vegetable oil. Although there is better printability, the aluminum hydroxide is light and will float on the surface of the ink layer after printing, resulting in poor adhesion or blistering. Wiley oil is slow in drying, and inhibiting the drying of the ink is not good for the coating. Therefore, Weili oil must be used with caution. The fast-drying glossy oil can make the prints glossy and dry and has good printing performance. We say that it is best to use a quick-drying bright oil as a diluting agent.

3, add printing and dusting

In order to adapt to high-speed multi-color printing, to prevent the back of the printed paper from sticking, packaging offset printing is often used to solve the dusting process. The sprayed powder is mostly composed of cereal starch and natural suspended matter. These powder particles are coarse. If too much dust is sprayed during the printing process, these powder particles will float on the surface of the printed product. When the film is coated, the adhesive does not bond with the ink layer at every place, which seriously affects the quality of the coating film. Therefore, it is necessary to strictly control the amount of powder sprayed when printing offset printing. Use the minimum amount of dusting on the premise that it is not sticky.

4, the surface of the print, the inner layer of dry

The ink on the surface of the printed matter or the inner layer is poorly dried, which will cause great damage to the quality of the film and cause problems such as foaming and delamination. There are many factors that affect the drying of the ink on the surface of printed matter, such as the type of ink, the amount of desiccant, the structure of the paper, the temperature and humidity of the workshop environment, and so on. Therefore, we must pay particular attention to the drying of the ink layer during printing. When printing, strictly control the ink balance, pay attention to the emulsification of the ink, and control the acidity of the fountain solution. At the same time control the temperature and humidity of the workshop. The surface and inside of the packaged printed matter are truly dried, so that the quality of the film is guaranteed.

In short, in order to ensure the quality of the packaging film, we must not only consider the film coating process, but also should be considered from the beginning of printing, otherwise the quality of the previous process will affect the quality of the latter process, this concept should be remembered. It is necessary to establish the idea that the previous process serves the later process.