Factors Affecting the Quality of Self-adhesive Label Flexographic Printing (I)

Avery Dennison began to get involved in flexo printing very early and began manufacturing its own UV flexo presses as early as fifteen years ago. At the same time, we also have a strong team of technical supporters, and gained a lot of experience in the accumulation of practice over the years. In this article, we will introduce some of the major factors that affect the quality of the adhesive printing process. We hope that we can help everyone to have a better understanding of the flexographic printing of stickers.

Flexo printing originated in the United States in the 1920s. Due to the toxicity of the aniline dye inks used, flexographic printing, originally called flexographic printing, has not been developed. In the 1970s, due to the progress of industry, the development of high-polymer resin plates, ceramic anilox rollers, UV inks, and UV drying technology in recent years has led to a qualitative leap in the development of modern flexographic technology.

At present, the flexo process is the fastest growing printing process in the world. In terms of the label industry, the US flexo printing accounts for about 85% of the label industry; the European flexo printing started later than the United States, and the current market share is about It's 45%, and it's rising rapidly. Flexo printing is currently in its infancy in Asia and many manufacturers are launching new flexo presses. The development of flexographic printing technology is in the ascendant, which was fully reflected in Chicago in the United States in 2000. All exhibitors invariably launched the latest flexographic or UV flexographic technology and equipment. Even some well-known equipment suppliers, formerly directed at the adhesive label industry's main software for the sudden printing of printed materials, quietly turned to the flexo version at the 2000 Chicago show, especially the UV flexo version. With the continuous progress of science and technology, flexo printing has gradually entered a new era. The reason why flexographic printing has achieved great development is due to its economy and high quality.

1. Color separation film

Separation film directly affects the print quality and print quality. Since the flexographic printing uses mesh spinning rolls, the anilox roll meshes are arranged at a certain angle (currently 60 degrees or 45 degrees at most), and in order to avoid electroprinting, the flexographic film screening angle is 7.5 degrees compared to offset printing. The difference. If the film is used with a flat exposure system, the graphics should be compressed according to the diameter of the plate cylinder, the thickness and thickness of the double-sided adhesive before the film is formed. It should also pay attention to the performance of the film and media graphics performance match. The use of frosted film will be more conducive to the production of printing plates.

2. Plate material and production

First of all, according to the type of ink used to select the appropriate plate, not all plates are suitable for the use of UV ink, the wrong choice will cause the printing plate in the printing process swelling and deformation. The plate making process is also very important, and the time control of each step should be just right. Underexposure, excessive de-sticking, insufficient drying, and improper storage will reduce the plate life.

3. Anilox roller characteristics

First of all, the selection of the mesh roll should follow the following principles: The number of screens (line/inch or line/meter) of the separation film should be at least 1:3.5 with the anilox roll, and dot printing should reach a ratio of 1:5. . The degree of cleaning of the anilox roller is also very important. Regular and thorough cleaning of the texture can ensure the ink transfer amount, ink color matching and repeat repeatability.

4. Ink type and compatibility, ink system

Different substrates should use the corresponding ink system, such as paper ink, PE, PP, PET plastic film ink, PVC ink, aluminum foil ink and so on. Incorrect selection of the ink system, or poor ink compatibility, can lead to a decline in the performance and strength of the ink on the surface of the substrate, and may even cause h-response.

5. Corona treatment, surface coating, UV lamp

These factors also affect the adhesion of the ink, and the printability of the plastic film can be improved by the corona treatment of the printing surface and the application of a surface coating layer. The surface is coated with a variety of chemicals: acrylic, vinyl, etc., solvent-based or water-based. The use of gravure wheel or flexo printing, the advantage is: for printing no time limit, good wetting and ink binding force, suitable for most of the current market and ink, do not need online equipment and processing, chemical resistance And scratch better, suitable for printing at the same speed. The disadvantages are that the cost is more expensive than corona-treated material relative to the finished product, and corona treatment is the most common method currently used to improve the surface coatability, wettability, and adhesion of the PE/PP.