Application and Development of Printing Polishing Technology

1、 Printing glazing vs traditional lamination

      The traditional film covering technology has gone through many years, and we are no longer unfamiliar with its technology. Compared with glazing technology, they have both similarities and differences. The so-called printing polishing is to use the field printing plate or graphic printing plate to reprint the polishing oil once or twice on the surface of the copy after completing the graphic printing, so as to obtain a bright and transparent film on the surface of the print. Common glazing methods include oily glazing, aqueous glazing and UV glazing.Application and Development of Printing Polishing Technology

      Printing glazing can enhance the light resistance of the ink, increase the heat and moisture resistance of the ink layer, protect the imprint, beautify the product and replace the film. Compared with film coating, printing glazing has low price and simple process. It can be either full plate glazing or local glazing.Application and Development of Printing Polishing Technology

（1） . environmental protection

     First of all, from the perspective of simple environmental protection, water-based and UV are in line with the trend. Because the film has two layers of pollution, white pollution and film covering glue pollution. The cover after water-based glazing and UV glazing can be recycled directly without any further treatment.Application and Development of Printing Polishing Technology

     In addition, from the perspective of the general environment of market application, in addition to the packaging of food, drugs and cosmetics, even those electronic products that do not come into direct contact with the human body are gradually required to adopt the pollution-free printing method of glazing because the corporate culture advocates environmental protection and is proud of it.Application and Development of Printing Polishing Technology

      With the economic exchanges and cooperation of various countries, a considerable number of printing and packaging enterprises in coastal and Mainland China have outsourcing business, while western countries have high requirements for environmental protection, and pollution-free Waterborne Glazing and UV glazing have developed quite mature. Especially in the fields of food packaging and drug packaging, Europe has formulated strict standards, and the living space of film coating and oily polishing that do not meet the standards has been very small.Application and Development of Printing Polishing Technology

       The traditional film coating process will not completely fade out of the market because it can increase the thickness and toughness of the paper and its good waterproof. However, in the face of the improvement of global environmental protection awareness, products are required to be recycled or biodegradable. The film coating process must strive to improve the pollution of products, working environment and external environment in order to have more living space.Application and Development of Printing Polishing Technology

（2） , cost and efficiency

      According to the actual application, the cost of film coating is higher than that of glazing. In the industry, the quotation of glazing generally does not exceed half of the film coating, so the traditional film coating has no advantage in cost.Application and Development of Printing Polishing Technology

      The coating speed of the traditional laminating machine is 30m / min-75m / min, while the current online polishing equipment can fully match the speed of the printing machine, and the stability of the polishing quality has been greatly improved. Without considering the specific requirements of customers, the glazing process is more economical from the perspective of efficiency.Application and Development of Printing Polishing Technology

      It is worth noting that the transfer membrane process, which has been used for many times in recent two years, has broken through the boundary of traditional coating, and has begun to show its advantages in the application of related color boxes and cigarette packs.Application and Development of Printing Polishing Technology

2、 Characteristics of varnish

      There are many kinds of varnishes, but the commonly used varnishes can be roughly divided into three categories: oily varnishes, waterborne varnishes and UV varnishes. According to the practical application trend of varnish and the improvement of environmental protection requirements, the use of oily varnish will be reduced day by day, while the application space of Waterborne Varnish and UV varnish is very broad. This section mainly introduces waterborne Varnish and UV varnish.Application and Development of Printing Polishing Technology

（1） Water based polishing oil

      Water based varnish (water based varnish or dispersed varnish in English) is mainly composed of water-soluble resin and water dispersed resin,Application and Development of Printing Polishing Technology

      Water based polishing oil is non-toxic and tasteless, eliminates the harm to human body and environmental pollution, and has the characteristics of fast drying speed, good film transparency, stable performance, wide equipment adaptability, good wear resistance and flatness of polishing surface, wide post press processing adaptability, good heat sealing performance, safe and reliable use, convenient storage and transportation, etc. it is more and more popular in food, medicine Attention of tobacco carton packaging and printing enterprises.Application and Development of Printing Polishing Technology

The following typical problems should be paid attention to when using UV waterborne Varnish:

① For the problem of how to ensure that the bottom ink can be fully dried after coating water-based varnish, first ensure the air permeability of water-based varnish, so that the wet ink layer can contact the air for oxidation conjunctiva drying; In addition, this problem can also be solved by appropriately increasing the hot air temperature.Application and Development of Printing Polishing Technology

(2) the gloss of waterborne gloss coating is lower than that of UV varnish. In practice, a small amount of high boiling point solvent can be added into water-based varnish, and the emulsion particles can be smoothed to form a smooth coating, thereby improving the surface smoothness of the coating and ultimately improving the gloss of Waterborne Varnish.Application and Development of Printing Polishing Technology

（2） UV varnish

     UV glazing is the use of UV (abbreviation of ultra violet, i.e. ultraviolet) irradiation is a method to cure glazing coating. It has the characteristics of rapid curing of coating and low temperature curing, and ink is not easy to fade.Application and Development of Printing Polishing Technology

       It is helpful to solve many problems in the gloss processing of paper printed matter. Therefore, it has been widely used in the gloss processing of printed matter such as paper container, trademark, book cover, packaging box and so on.Application and Development of Printing Polishing Technology

     UV varnish contains almost no solvent, and the emission of organic volatiles is very small, so it reduces air pollution; UV varnish does not contain solvent and does not need heat energy during curing. The energy consumption required for curing is relatively small. In addition, UV varnish has strong affinity for ink and firm adhesion; Application and Development of Printing Polishing Technology

      UV varnish has high effective components, less volatilization and relatively low dosage; UV cured printing surface has more wear resistance, drug resistance and chemical resistance, good stability, and can be scrubbed with water and ethanol; UV glazing products are not easy to adhere, and can be stacked after curing, which is conducive to post-processing operations.Application and Development of Printing Polishing Technology

The following typical problems should be paid attention to when using UV varnish:Application and Development of Printing Polishing Technology

① UV varnish is not suitable for operation on permeable paper. Because the low molecular materials in UV coatings are easy to penetrate into the paper, causing the paper to darken or even soak. At present, most UV varnishes are used on printed paper with aluminum coating.Application and Development of Printing Polishing Technology

② The main reasons for the poor adhesion of UV varnish are: the crystallization of printing ink layer or the improper use of ink additives and anti-skid agents. The printing process should be improved and ink additives should not be used or used less;Application and Development of Printing Polishing Technology

③ The main reasons for the poor brightness of UV varnish are: poor paper quality, different surface roughness, uneven coating, too thin varnish, low viscosity and so on.Application and Development of Printing Polishing Technology

3、 Glazing equipment

     Printing and polishing equipment is divided into polishing machine (including calender) and printing and polishing linkage machine. The polishing machine is generally operated by a single machine, with slow processing speed and slightly poor quality stability, and often needs to be calendered. At present, large offset printing manufacturers at home and abroad mostly use printing online polishing to improve the polishing speed and quality. It can be said that printing online polishing is the development trend of polishing machinery.Application and Development of Printing Polishing Technology