Decorative textured screen printing method

Since the introduction of matte (imitation metal etching) ink, it has been widely used in high-grade cigarettes and wine packaging printing. Afterwards, inks such as wrinkles, icy flowers, refraction, and corals have appeared. They are favored by users of high-grade packaging. Scrubs, wrinkles. Ice flowers. Refraction and coral and other printing effects in the packaging printed material has played a good decorative effect, collectively referred to as decorative texture, used ink collectively known as decorative ink, its printing collectively known as decorative printing.

Decorative texture screen printing method

The inks used for decorative printing are all UV inks. The first is that UV inks cure fast and print quality is good. Even if the commonly used solvent-based inks use infrared drying, the curing is slower. The curing of aqueous inks is, of course, slower, and UV inks require only 3 to 5 seconds or even less than 1 second to cure. Second, scrub, refraction. Decorative textures, such as corals, must be instantaneously cured after printing. Screen printing wrinkles, ice and other decorative textures must be cured by UV irradiation to cause uneven surface shrinkage, and therefore can only be printed with UV inks.

The screen printing decorative texture has the advantages of simple equipment, low investment, and quick implementation. When making a plate, the part of the screen that needs to be printed with a decorative texture is mostly blank (except for the refraction effect). Decorative ink can be printed on the substrate. The desired texture is created by the intrinsic properties of various screen printing inks.

Matte printing is the most common type of application in decorative printing and is widely used in cigarettes. Printing of products, such as wine, cosmetics and health products. In addition to the semi-polymers, reactive diluents and photo-initiators necessary for general UV inks, the matte screen printing ink formulation also contains some granular materials with a size of 5 to 50 μm and a content of 5% to 40%. During printing, the ink is pressed with a squeegee to transfer the ink to the substrate (usually gold or silver cardboard) through the mesh of the screen. When the ink is printed on gold or silver paper, the particles are also transferred to the gold and silver paper. Due to the surface tension, the ink in the ink will agglutinate to the surface of these particles. After being cured by UV light, the ink will form. There are many large particles that have these particles as the core and are surrounded by a solidified resin, which we call sanding particles.

It can be seen that the generation and distribution of the matte particles are random. There are many factors affecting the size, color tone and distribution of the matte particles. Besides the ink formulation, the mesh size, the shape of the scraper, the angle of the scraper, the old and new scraper, the spacing between the screen and the substrate. The squeegee speed and the size of the force, and the properties of the substrate, etc. all have influence on the formation of the matte particles. In addition, ink scraping is like filtering the ink. The resin and fine particles in the ink are easier to pass through the screen, while the coarse particles are more accumulated in the residual ink. Therefore, the composition of the ink will occur after each scraping. Changes, the printed matte texture will also change. As a result of the above factors, the influence of many factors has caused almost all of them to be different even in the same printed matter. This determines that the matte effect of screen printing is only decorative function and no anti-counterfeiting function.

Wrinkles, another important type of decorative printing, are formed by the uneven shrinkage of the ink during curing and consist of many criss-cross lines. When using screen printing method to print wrinkle ink, a 100-250 mesh screen should be used. The thickness of the printing ink layer is 10-40 blaze m. The pre-irradiation with a low-pressure mercury lamp is first performed so that the ink surface layer is partially cured and contracted beforehand. Medium-pressure mercury lamp irradiation, so that the ink is completely cured. Due to the difference in the curing speed of the ink surface layer and the inner layer, the generated tension causes uneven shrinkage and wrinkling. There are many factors that affect the thickness, shape, etc. of the wrinkles, such as the thickness of the printing ink layer, the size of the screen mesh, and particularly the power and distance of the pre-irradiated low-pressure mercury lamp, the conveyor speed, and the like. Therefore, when the wrinkle texture is printed by the screen printing method, there is a clear difference in the wrinkles of each sheet even in the same printed matter.

Ice flower crystal clear, very beautiful. An ice pattern consists of many small "wafers," each of which contains many lines of different lengths and shapes. The ice flower effect is printed with a special UV ice-printing ink. When the ink is exposed to UV light at a relatively high temperature, uneven curing shrinkage is generated and the crystal grain is formed. If the curing speed is too fast, beautiful grain patterns cannot be obtained. Therefore, the UV screen printing ice printing ink has a very slow curing speed, a high curing temperature, and a very high energy consumption. A printing factory in China has invested in a UV curing machine for the purpose of printing ice flowers. It uses 9 sets of 6.3 kW UV lamps and can print more than 600 folios per hour.

At present, some equipment manufacturers have developed new types of UV curing equipment. Although the curing speed has been improved, the quality of the grain lines is very poor. Ice printing is influenced by many factors such as ink layer thickness, UV lamp intensity, temperature, curing speed, and so on. It has great randomness and arbitrariness. Not only does the ice print effect of each print differ, but also different parts of the same print have The difference is that the process is unstable and the product consistency is very poor. Therefore, the screen printing ice flower still remains in the proofing or small batch production stage.

The other two important effects in decorative printing are corals and refractions. The so-called coral is actually a bubble, but it is just a bubble that looks like a coral. The effect of printing corals is UV screen printing coral ink. The surface tension of the ink is very small. When printing, the ink is transferred to the gold and silver card paper through the screen under the action of the blade pressure. When the screen is rebounded, bubbles are generated. The ink is characterized by being capable of stabilizing the air bubbles in the ink layer as it is. After being cured by UV light, a so-called coral effect is formed.

In decorative screen printing, the refraction is rather special. The formation of other decorative textures is naturally formed by the inherent characteristics of the ink. It is disorderly, and the refraction is made in the screen to make many parallel and dense lines. When printing, the refraction ink is scraped onto the gold and silver card paper to generate a dense parallel grating, and the incident light is refracted to form a refraction effect. In general, the screen density of 4 screens/mm or more can achieve better refraction effect.

There are many types of screen printing decorative inks, but each kind of ink can only print one effect. For example, matte inks can only print frosted effects and cannot be used for printing such as wrinkles and icy flowers. And, even if the matte ink is thick. There are several kinds of medium and fine ones, each having its own purpose. If there are several kinds of decorative textures such as coarse sand, fine sand, wrinkles, and refraction in the same printed matter, they must be plated separately and printed in multiple times according to the process requirements of each type of ink, which is not only very troublesome, but also difficult. Registered, scrap rate is extremely high.

Source: HC Network