What is gravure printing for composite packaging bags?
The gravure printing industry is referred to as gravure printing. Gravure printing is one of the four major printing methods. It is named after the printing plate, that is, all printed patterns and characters are recessed on the printing plate. The printing must be done first. Roll the ink on the plate surface, the ink will naturally fall into the printed part of the depression, and then wipe the ink adhered to the surface (of course the ink of the depression will not be wiped off). After placing the paper, use greater pressure to emboss the recessed printing ink on the paper. Those who use this printing method are called “gravure printing.”
Gravure printing is divided into engraved gravure and photo gravure:
1. Engraving intaglio:
Engraving intaglio is an early evolution from metal decoration carving. At that time, the carved copper pattern was used as an ornament, and then it was used for printing performance.
The copperplate printing paper used in engraving gravure was first moistened in the early stage, mainly to increase the adhesion of the ink to the ink. Therefore, the back of the paper needs to be padded with a thick cloth, and a greater pressure can be used to dent the printed pattern. The adhered ink is drawn and printed on the paper. The main disadvantage of this printing method is that it needs to be dried after printing, which will produce irregular expansion and contraction, which will cause the length of the printed product to be uneven. But now copperplate printing has been improved to a dry printing method, which has improved the layout and made the lines of the engraved depressions shallower. Make it easy to pull out the sticky ink. According to copperplate printing and steel plate printing, the thickness and depth of the pattern are used to express the three-dimensional effect. The thick and deep printing plate has thicker ink, so the ink color is relatively thick. deep. A printing plate with thin and light lines will hold thinner ink, so the ink printed on it will be lighter. This kind of printed matter is as beautiful as the design of modern visual art, but most of them are used to express patterns or text. As for continuous-tone like photos, it is more difficult to achieve.
Photogravure is also called photocopy, that is, the copper plate is corroded by the principle of photography. It is a kind of adhesive paper (LarboTissue) that has been sensitized by potassium dichromate solution and a special screen for gravure. Then the adhesive tape and the positive film of continuous plate adjustment are exposed. After the adhesive tape is exposed for two times, it can be developed by warm water. The adhesive tape in the light part of the picture has a lighter black and silver on the positive film, so the adhesive tape The degree of hardening by the light wave is higher, so the film after water development is thicker. The adhesive paper in the dark part of the screen can be light wave due to the thick black and silver mask of the positive film. The degree of hardening by transmission is less, so the film after water development is thinner. Therefore, after the development, the adhesive tape of different thickness is attached to the copper roller or flat roller, and it is corroded by ferric chloride. The thicker part of the light part of the adhesive film, the solution can penetrate and erode the copper plate to a greater depth. It is shallow, so the ink film that it adheres to is thinner, and the ink color that it prints is lighter. As for the dark area, where the film is thin, the thickness of the glue can be penetrated by the solution and etched into the copper plate must be deeper, so the print is sticky The ink film is thicker, and the ink color it prints is darker.
What are the characteristics of gravure printing on plastic packaging bags?
1. The amount of inking of Louyin is determined by the depth of the concave of the graphic part of the curved printing plate. The concave depth of the graphic part during printing is relatively fixed. Therefore, the amount of ink is kept relatively stable;
2. The inking method of gravure printing is that the plate cylinder is directly immersed in the ink tank to receive the ink, or the ink transfer roller is used to coat the ink on the plate cylinder, eliminating many ink transfer rollers and ink volume adjustment devices;
3. The ink transfer volume of gravure printing is larger than that of offset printing and flexographic printing, so the ink layer of the product graphics and text is thick, and the three-dimensional effect is strong;
4. Most gravure printing is rotary printing, with fast speed and strong ability;
5. The range of gravure printing materials is wide, and it has good adaptability to plastic packaging bags and composite materials that are easy to extend and deform;
6. Gravure printing uses dry ink and non-absorbent plastic packaging film.
Disadvantages of gravure printing: plate-making costs are expensive, printing costs are also expensive, plate-making work is more complicated, and a small number of prints is not suitable.