Abstract: What are the several methods of self-adhesive printing? What are the precautions for self-adhesive printing? Self-adhesive refers to prints printed on a composite material with paper, film or other special materials as the fabric, adhesive on the back, and silicon-coated protective paper as the base paper. This article mainly introduces several methods of self-adhesive printing, as well as relevant knowledge points such as adjusting the paper feeding part and adjusting the printing pressure when printing self-adhesive. Self-adhesive printing Several methods of self-adhesive printing Precautions for self-adhesive printing

Several methods of self-adhesive printing

Currently, global self-adhesive label printing adopts The different printing methods can be divided into three camps.

1. Mainly flexo printing

North America is a typical representative of self-adhesive label printing using flexo printing as the leading technology. The main equipment is a small and medium-sized unit-type printing unit, which mainly uses ink and ink. It adopts roll-to-roll printing and circular die-cutting. It has the characteristics of high production efficiency, advanced technology and compliance with environmental protection requirements.

2. Half and half between letterpress and flexo printing

This processing method is mostly found in Europe. The application of flexographic printing is basically the same as that in the United States. Letterpress printing also accounts for 50%. And letterpress printing all uses UV ink, and most of the equipment is stacked or satellite type. The material processing method is also roll-to-roll printing.

3. Mainly embossed printing

This method is mainly used in the Asia-Pacific region. There are mostly developing countries in the Asia-Pacific region, and label printing is still relatively backward. Even if letterpress printing is used, only a few use UV ink equipment. Most label printing still uses resin-based ink, roll-to-roll printing and sheet-fed printing. ***Existence; Due to the high proportion of manual labeling, sheet-fed offset self-adhesive labels are widely used; the die-cutting method is mainly flat die cutting.

4. Offset printing

Offset printing is the main way for label printing factories in my country to print paper self-adhesives. Offset printing is characterized by fine graphics and rich layers, which is suitable for mass printing. The printing equipment can be used for multiple purposes, which is suitable for the characteristics of the Chinese label market. However, sheet-fed offset printing is not suitable for printing films with no absorbent surface, because film labels are mostly roll-to-roll printing and require volatile drying ink. Offset printing can print thicker plastic materials, such as in-mold labels and labels and tags, but the machine must be equipped with a UV curing device, which requires a considerable expense.

5. Screen printing

Screen printing is the printing method with the widest adaptability to substrates. Currently, many screen printing factories use low-cost screen printing equipment to contract for self-adhesive labels and Film label printing business. Screen printing labels are characterized by thick ink color and strong three-dimensional effect, and UV ink can be used to print film products. Except for a handful of rotary screen printing equipment that are capable of roll-to-roll label printing, most screen printing equipment are semi-automatic flat screen printers that can only print single products, have low overprint accuracy, and are not suitable for use with production lines. Film label production equipment. Post-press processing technology should also pay attention to the corresponding changes in label post-press processing during business transformation. For example, when printing self-adhesive labels, the post-press processing of self-adhesive labels is divided into sheet-fed processing and roll processing according to the application form of the label. Paper processing.

Precautions for self-adhesive printing

1. Pay attention to the adjustment of the paper feeding part when printing self-adhesive. The air volume of the paper suction nozzle and paper blowing nozzle in the paper feeding part should be increased accordingly.

2. The paper separation nozzle and paper feeding nozzle should be replaced with larger diameter and thicker rubber rings to achieve smooth paper feeding and the paper feed roller does not swing.

3. Adjust the printing pressure. In the offset printing process, every two adjacent rollers among the three rollers of printing plate, rubber and impression are in contact and squeezed with each other to perform transfer printing. In order to achieve normal ink transfer on the printing paper and truly reproduce the continuous-tone text, lines, images, and half-tone dots in the graphics and text parts, these imprints must be added with the necessary printing pressure in addition to the surface contact between the two rollers. effect. The severity of the printing pressure and the accuracy of the adjustment control will directly determine the size and depth of ink color transfer and printing dot reproduction.

It is necessary to adjust the center distance between the impression cylinder and the rubber cylinder during self-adhesive printing. The center distance of the cylinder can be increased by about 0.2 to 0.4 mm. If the paper changes from thick to thin, the thickness that should be reduced is the thickness of the lining removed from the printing plate liner and added to the rubber cylinder; if the paper changes from thin to thick during printing, the thickness should be reduced from the rubber cylinder lining. Remove a certain thickness and add the corresponding thickness to the lining of the plate cylinder.

When loading the plate, it must be pressed tightly to prevent relative slippage during printing. In actual production, the ideal printing pressure is generally controlled at about 0.15-0.25mm. The ideal printing pressure must be emphasized. It means that under a certain compression and deformation of the printing surface, the minimum pressure should be used to ensure that the imprint of the graphics and text parts of the printing plate is strong enough on the paper and the dots are clear and complete.

4. Since the self-adhesive is the thickness of two layers of coated paper, the thickness of the paper should pay attention to the gap between the double-sheet controller and the corresponding increase in the paper pressure tongue and feeding board of the side gauge and front gauge. The distance between them should be increased.

5. The distance between the paper feeding dog pad and the surface of the impression cylinder, as well as the paper feeding dog pad and the feeding paper board, should be increased, and the distance should be kept approximately equal to the paper thickness plus 0.3mm.

So, what are the special arrangements for the color sequence of self-adhesive printing?

1. Self-adhesive printing products have a solid surface, as well as text, lines, and patterns. For example, for printing products such as wine boxes and pharmaceutical trademarks, it is best to first print text, lines, and patterns in the color sequence, and then put the full version on the machine for printing at the end. This can avoid the imprint being left unseen due to the thickness of the self-adhesive paper. When the paper is dry, the paper collides with each other and is scratched, and the back side becomes sticky.

2. Print the darker colors in the front and the lighter colors in the back. Since the darker ink has strong hiding power and strong adhesion, it is better to print in the front first to facilitate accurate overprinting. , the covering power of light colors is weak, and it is difficult to see if it is slightly out of order when overprinted at the back. Correspondingly, the overprinting effect is also good.

3. Often in a printed product, there are half-tone four-color dots and continuous tone patterns, text, and lines. At this time, the four-color dots should be printed first, which is beneficial to Accurate overprinting can reduce the impact of paper expansion and contraction, and then print continuous-tone text, lines, and patterns. The printing color sequence should be prioritized, and it is more appropriate to start with difficult tasks and then easy ones.

4. The weather changes greatly in summer and during rainy seasons. It is necessary to control the temperature and humidity of the environment. The cut paper stacks and semi-finished products must be tightly wrapped in plastic before and after printing.