Why is there color difference in plastic packaging printing? What should be done?

The packaging with pure and bright color can add color to the product, while the packaging with uneven ink and color difference may reduce the grade of the product. But in the printing process, color difference often appears, then what is the cause of color difference? What should be done about it?

First, human factors

The color difference in printing may be the poor level of printing personnel or the relatively poor sense of responsibility, some workers in the ink has not yet been balanced, they began to open all the way, the printing process keeps adjusting the amount of water and ink, while adjusting and opening, is bound to cause the color difference in the same batch of printed products, which has a great relationship with the skill level of workers, experience, and personality. It is the color difference of the same batch of products caused by the lack of ability.

In addition, whether the person in charge is responsible is also an important reason. If the first sample is not signed or signed incorrectly, the person in charge and the worker will not have a comprehensive grasp of the product requirements, which will lead to the inconsistency between the printed matter and the sample.

Second, poor ink

The process shows that the thickness and viscosity of the printing ink layer are not easy to produce printing color difference. When printing, only a moderate and uniform printing ink layer can better ensure the ink quality of the printed product and effectively prevent the production of printing sticky faults. If the printing ink layer is too thick, its viscosity will increase correspondingly, which is easy to cause the phenomenon of powder off the paper surface in printing and hair, and then affect the uniform color of the printing ink. However, if the printing ink layer is too thin and the ink viscosity is too small, the ink color of the print will appear light, and the visual effect of the print is poor.

Three, printing surface treatment

Plastic packaging printing will go through a variety of surface treatment processes such as laminating, glazing, calendering, and over-oiling, which will also lead to different degrees of color changes on the surface of the printed matter. Some of these changes are physical and some are chemical. The physical change is mainly reflected in the increased specular reflection on the surface of the product, which has a certain impact on the color density. For example, complex film, UV varnish, calendering, etc., the color density will increase. The color density of the printed product is reduced after multiple subfilm and matte oil. The chemical change is mainly from the coating adhesive, glazing oil, UV oil and so on. These materials contain a variety of solvents, which will cause chemical reactions in the color of the printing ink layer and cause color changes.

Four, printing pressure

The ideal printing process is on the basis of "three flat (ink roller flat, water roller flat, roller flat)", in order to use a thinner ink layer through the role of balanced printing pressure, so that the printing can be more uniform ink color. When the printing pressure is insufficient or uneven, when there is poor contact between the packaging body and the printing page, it is necessary to increase the amount of ink to meet the visual effect of the page inking, but this will not only increase the consumption of ink, but also easily produce printing color difference and sticky quality problems.

Five, the ink roller is poor

Lithography, letterpress and other printing processes, printing products can obtain uniform ink color, the quality of the roller has a crucial role. On the printing machine of color prints, there are generally three kinds of ink roller, ink roller and ink roller, among which the ink roller and ink roller have a greater impact on the color of ink. The elasticity, viscosity, roundness, hardness and surface finish of the ink roller largely determine the quality of the ink. If the inking roller has poor elasticity, insufficient viscosity, eccentric roller body, hard colloid and poor colloid finish, it is easy to cause uneven or unstable ink brushing in the printing process, so that the printing ink color of each sheet is inconsistent.

6. Maintenance of equipment

The operating state of the equipment will also affect the printing quality. If the machine is unstable, such as inconsistent pressure and unstable paper feed, empty sheets and multiple sheets frequently appear in printing. It is bound to cause color difference in printing.

Therefore, the daily maintenance of the equipment should be strengthened, attention should be paid to the lubrication of the key parts of the machine, to prevent the intensification of wear, so that the equipment is in a stable state, and the quality of printing ink should be improved.