Application of gravure printing in in-mold labeling

In-mold labeling (1 "Mould Label") is a brand-new label packaging form that is different from the traditional direct screen printing, heat shrink label, self-adhesive label, and is mainly used for blow molding of plastics such as PET, PET, etc. Injection molding products, that is, before the blow molding and injection molding, the printed in-mold labels are put into the blowing and injection mold cavity. When the molds are blown and injected, the mold is marked by high temperature and high pressure inside the mold. The special adhesive melts and fuses with the surface of the bottle or injection molded part. When the mold is opened, a beautifully printed bottle or injection part is completed at one time.

First, the printing of in-mold labeling

In-mold labeling bottom paper is a paper-plastic composite material. The most commonly used printing methods are offset printing and flexographic printing. There are gravure printing abroad.

Offset printing, also known as lithography, utilizes the principle of polar water molecules and non-polar inks repelling each other. In the graphic part of the layout is the lipophilic surface, which absorbs ink, and the blank part is the hydrophilic surface, repelling the ink. When printing, wet the surface with water first, make the blank part adhere to the water film, and then use the ink roller to infiltrate the entire plate surface. At this time, the blank part repels the ink, and the graphic part adheres the ink, and the printing plate and the pressure act to make the printing plate. The text is transferred to paper.

According to its layout features, flexographic printing is a type of relief printing. The printing plate is a relief plate with a relief height of 0.7 mm or more. The ink is transferred to the embossed surface by a flat textured metal ink roller with 200N500 lines/inch. , and then directly imprinted on the material to be printed.

In gravure printing, the graphic part of the printing plate is recessed by electronic engraving or laser engraving. The non-graphic part is convex on the same plane. When printing, the surface of the printing plate cylinder is covered with ink, and then the printing plate is made by a special squeegee. The ink on the surface of the drum is scraped, the graphic part of the concave part of the drum is full of ink, and after the pressure is applied, the ink of the concave part is transferred to the substrate.

Second, the characteristics of printing on the in-mold labeling printing

1 consistent color printing

The traditional offset printing, due to the printing principle and the limitation of the printing method, is easy to produce color difference in the mass production, and the gravure printing will keep the color difference small due to the continuity of the printing and the fast printing speed and can guarantee the batch color. Consistency.

2. The bottom paper requires low

The use of gravure printing can make common bottom paper into pearlescent, matt, white and other forms through different printing materials, so that the variety of stickers in the mold can be completed through printing, simplifying the requirements for the bottom paper material.

3. The printing process is simple

After the offset printing and flexographic printing, the ink needs to be cured, and the UV light oil is used for protection. This often causes back sticking, which causes the adhesive surface to adhere to the ink and affect the lamination. However, gravure printing can achieve the requirements of fastness to the surface pattern through the binding force of the ink to the backing paper and its own resistance to rubbing, and can be quickly dried, simplifying the printing process, improving the work efficiency, and reducing the cost.

4. Simple process

Offset printing and flexo printing can only print common ink colors. If the label requires localized effects such as hot stamping, bright silver, and laser, it must be compounded with other materials and labels. The gravure printing can complete all the local processing such as printing, aluminum plating and laser on a bottom mold, which not only improves the efficiency but also reduces the high waste rate caused by the secondary treatment.

5. Improve the quality of the label

When hot stamping, the hot pressure destroys the pores of the label's back layer, which can easily generate bubbles and become sand spots, destroying the overall effect of the label, and the gravure printing of bright gold and bright silver is part of the printing, and its nesting accuracy is high. Can print small gold, silver text, can complete the second hot stamping can not achieve the exact rate of registration, to ensure the overall quality of the label.

In-mold labeling has been popular in some developed countries in Europe and America for many years. After two to three years of observation in China, it has also begun to be applied on a larger scale, and it has been accepted by more and more people in the industry and end users. Gravure printing It is also bound to become one of the main printing methods for in-mold labels due to its unique advantages.

(Text / Wu Yi Zhang Yaping)