The role of glazing in packaging printing

With regard to the finishing and finishing of the paper surface, many domestic packaging and printing companies have an erroneous conception; as long as it comes to glazing, no matter what the user wants, the packaging is used to package what kind of product. Polished as usual. I personally believe that the glazing properties of the paper surface must first be determined by the contents of the package. At the same time, it is also necessary to analyze whether the packaged printing products that have been coated with light have reached the point of view of post-press processing, transportation, and storage conditions. The user's actual use requirements.

First, the surface finishing effect of polishing

The finishing function of glazing is mainly to protect the printed products or improve the vividness of the surface of the printed products, improve the grade of the products, and create good conditions for post-processing such as die-cutting or gluing. There are many kinds and methods of coating, and the varnish used in coating has oily materials (thinner: toluene, etc.), alcohols (release agent: alcohol, etc.) and water-based materials (release agent: water). The coating machine has an on-line coating unit and an independent coating machine. The on-line and off-line stand-alone coatings can be classified into extrusion coating type glazing and blankets or flexo-type transfer type glazing. In addition, the screen printing machine can be used for partial coating or full-plate coating.

The application of various glazing materials and glazing equipment should be decided according to different paper, different inks and different finishing effects, but also consider the different situations encountered in the glazing process, and then decide to adopt the overall analysis What kind of glazing technology, how to add different additives or thinners in glazing materials to adjust, in order to achieve the coordination, aesthetics and durability.

For example, drugs, foods, cosmetics, and other goods, because it is food or direct contact with the body of the article, so when the surface finish of its packaging, you should use alcohol or water-based coating materials. This will not only harm the human body and animals, but also meet environmental protection requirements. If chemical materials containing benzene are used for polishing, although the effect of coating and the cost of coating will satisfy printers and users, the potential harm is long-term.

In addition to the full version of the coating, a partial polish can be used to perform higher-level finishing on the surface of the printed product. However, at present, the only way to reflect the design intention of the partial coating is personally believed that there are only three processes: screen polishing, Intaglio printing and offset UV varnish can only be referred to as partial coating by glazing products made with these processes. Some of the so-called local glossers (including our Foucault's local coaters), whether coated with a blanket or coated with a flexographic plate, have not achieved the required accuracy. Lines, etc. can't be done with existing local glossers, even if it's done. The effect is also not ideal. Therefore, I generally recommend that customers use the screen printing process to do partial glazing, so that the glazing product made on the surface has a three-dimensional sense, the level is more distinct, and the precision is high.

The main function of polishing is to increase the brightness of printed products and polish the printed products. Its surface finish can reach the level of glass cardboard. However, after the polishing of the printed products, the folding endurance is poor. This is because the temperature of the calender when polishing is high, and the moisture of the paper is almost completely sucked away. Therefore, it is generally necessary to perform a resurgence treatment after the polishing. The use of suitable indentation lines and undercuts for die-cutting can also help overcome this shortcoming of the polishing process.

Currently more popular in the matt surface (matt coating or matte coating) on ​​the local UV coating. Finishing works well. In addition, you can also add different effects of coarser pigments (such as pearlescent pigments) to UV coatings. In order to achieve a special finishing effect.

Second, the functional role of polishing

The functional role of glazing is mainly reflected in water resistance, moisture resistance, folding resistance and abrasion resistance.

When it comes to improving the function of paper packaging, the most common is to increase the strength of the paper. At present, the most common domestic applications are film, including composite BOPP film, matte film, PET film coated with gold, silver or other colors, or Gravure-printed film.

Regardless of the material of the film, the function of the film is generally to improve the waterproof, folding and abrasion resistance of the print. However, for cartons and carton packs, film is not the best choice because the carton and cartons that are covered with the film are poor in moisture resistance. Once damp, they are likely to debond, resulting in separation of the film from the paper.

For the carton, carton packaging, UV coating is an ideal choice, because the UV coating after the waterproof, moisture resistance and abrasion resistance are better. Only UV glazing If handled improperly, the product has poor folding resistance during die-cutting and is prone to bursting. However, better glazing preparation is used, and mastering the glazing process can still be overcome.

Due to the high surface brightness of UV-glazed packaging, which does not steal light, and has good wear resistance and penetration resistance, UV coating has been widely used in the packaging of ceramics, machine parts and other products. . However, there are many disadvantages of UV polishing, such as: After the UV coating of packaging products smell heavier, irritating to the human body; UV coating oil on the paper and ink adhesion is poor, poor adaptability after processing, not easy to paste Box, easy to burst when die-cutting and so on. Although UV glazing materials are constantly improving, many developed countries do not allow UV coating on foods, pharmaceutical products and cosmetic packaging.

After the water-based coating products waterproof, moisture resistance, folding resistance are better, but the wear resistance is poor, but if you choose a better glazing equipment (such as extrusion coating glazing equipment), with the use of Better glazing oil can also be overcome.

Ordinary varnish oil also has certain waterproof properties, depending on the nature of the material, but generally the overall effect is relatively poor. In the field of packaging and printing, ordinary coating oils are generally used only on very ordinary packages that do not have any functional requirements, or simply to prevent the printing ink layers from being scratched.

III. Application of Coating Technology in Arts and Crafts Works

In the processing of arts and crafts, glazing can provide the finishing touch.

With offset printing and glazing, last year we made about 20,000 square meters of oil painting. As it is the first time, I feel that the effect is not very satisfactory. But it can be said with certainty that through the improvement, the effect of simulating oil painting is still feasible.

To achieve the effect of oil painting through the glazing process, cloth, ink and glazing materials and equipment must be well matched. We have made continuous efforts to make this batch of activities. Due to the tight time frame, some process problems have not been dealt with very well, but the users are still very satisfied. This year we have signed a contract with us to do 40,000 square meters of oil painting.

Fourth, the development prospects of polishing technology

Whether it is UV coating, water-based coating, ordinary coating, or polishing (also known as calendering), each has its own advantages and disadvantages. It has a certain market demand, but comprehensive consideration of environmental protection, human health impact and human nature. After the convenience and low cost of chemicalizing and glazing operations, waterborne glazing is undoubtedly the most advantageous. At present, in the developed countries, waterborne coating has become the mainstream of coating technology. The surface of paper treated with water-based varnish can be post-treated whether it is bright or dark, such as adding a partial coating, or performing finishing operations such as bronzing, gold sweeping, and embossing.

At present, the application of coating technology has gone far beyond the publishing, printing, packaging and printing industries. It can be used not only for gravure printing, offset printing, glossing, screen printing, but also for paper printing. Spraying and other technologies are applied to mobile phones, decorative materials, and PVC sheets. The polishing technology has a bright future.