The hottest special gravure printing technology

2022-10-14
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Special gravure printing technology process

gravure printing has always been an important part of the printing process, and forms four printing process systems with offset printing, flexo printing and silk screen printing. The advantages of gravure printing process are very obvious. The printing pattern is bright, the level reproduction ability is rich, the printing plate has strong printing resistance, and the high-speed operation reaches more than 250m/min. it is suitable for a wide range of printing substrates. In China, gravure printing is mainly used for plastic packaging printing. With the development of printing technology and the change of technology, gravure printing has expanded from plane printing to curved surface three-dimensional printing, especially in decorative printing. In the traditional gravure printing of plastic packaging, plastic film is the final printing substrate, while in the emerging decorative gravure printing, plastic film is the carrier of printing ink patterns, which is finally printed on flat or curved objects through various transfer methods. Based on the different printing carriers, there are many ways of transfer. This paper mainly uses plastic film as the carrier to introduce two new special gravure printing technologies: plastic film heat transfer printing and water transfer printing (water coating)

the heat transfer printing process of plastic film refers to taking plastic film (generally PET film) as the printing carrier, first coating the separation layer on pet, then printing various patterns on the separation layer, and then coating the hot-melt bottom layer on the pattern, so as to complete the printing process of heat transfer film. With this kind of transfer printing film, on a certain heat transfer machine, through instantaneous high temperature (generally ~c) extrusion, complete the transfer and attachment process of printed patterns. Heat transfer printing technology is applied in a wide range, such as architectural decorations, wood like panels for furniture, daily plastic products and stationery gifts

analyze the heat transfer printing process, which is basically the same as the traditional plastic flexible packaging printing, but the selection of raw materials should have targeted and professional requirements. PET film, the carrier of the film, is generally of ordinary/XM thickness. The selection of ink and coating is the key to the production of heat transfer printing film. Due to the short rise of this process in China and few professional manufacturers engaged in the production of heat transfer inks and coatings, Zhejiang New Oriental ink group has produced plastic film heat transfer supporting inks and coatings through technical exchanges and the introduction of foreign technology, which can fully meet the production requirements of this process. The separation layer requires high transparency and gloss, light color, blocking the adhesion of printing ink to PET film, good affinity with ink, and excellent wear resistance. Due to the instantaneous high temperature, the printing ink must not fade and stick, and can have adhesion fastness with various plastic substrates to ensure the smooth progress of the processing process after transfer. The hot-melt primer should have good instant hot-melt effect and excellent adhesion, and cooperate well with the ink layer. The heat transfer ink produced by New Oriental ink company is a003 ink, the separation layer (primer) is A001, and the hot melt adhesive is A007. The primer and hot melt adhesive produced in Taiwan or Japan are very expensive, which are poorly compatible with domestic heat transfer inks and lack of technical after-sales service support. However, this series of products of New Oriental ink company have been used and confirmed by many domestic manufacturers, and the coordination between the two is good, and the after-sales service is in place

the success of heat transfer printing film directly affects the effect of transfer processing. According to our application experience, whether the transfer of printing patterns is complete, in addition to temperature and contact time, the compatibility between the separation layer and printing ink is a key factor. The separation layer should not only have a certain adhesion fastness with PET film (2) admixture, but also ensure that the ink layer does not penetrate into the PET film during printing to produce adhesion fastness with PET film. If the compatibility between the separation layer and printing ink is not good, the printing effect of printing ink will be affected, There are even problems such as the printing pattern is not colored, and the transition point in the light version area is missing. In traditional plastic film printing, the transparency and gloss effect of the film itself greatly promote the gloss of the printed pattern. In heat transfer printing, because the final PET film is separated from the printed pattern, the gloss of the pattern itself mainly depends on the gloss and transparency of the ink itself and the separation layer (primer). Therefore, when selecting ink and coating, we need to consider the transparency and gloss effect of the separation layer, as well as its wear resistance, Especially in the production of heat transfer film for furniture panels and daily necessities plastic products. In addition, when making heat transfer films, we need to pay attention to the safety and hygiene of the printing ink itself, such as the content of heavy metals, especially when processing export products, there are relevant regulations and standards in Europe and the United States

water transfer process includes three parts: the production of water transfer film, water transfer and finishing. Water transfer film is made by printing patterns (such as wood grain and marble grain) on water-soluble film (PVA) with special ink through gravure printing machine. There is a complete set of special forming equipment for water transfer, and the general process is as follows: after the printing coil is sprayed with activator, it is immersed in hot water at a fixed temperature, and the object to be printed is pressed into water, which contacts the printing film, and the pattern covers the surface of the object. Due to the dissolution of water, the PVA film is dissolved, and the object is cleaned and dried. Finishing refers to the processes of polishing and painting objects with transfer patterns. Water transfer printing technology has not developed for a long time in China, but its development speed is very fast, and its application range is very wide, especially in automotive interior decoration, furniture and communication products

in the water transfer process, the most critical process is the production of water transfer film. At present, there is a considerable gap between domestic water-soluble printing films and imported products in film flatness and printing applicability, although the price of domestic films is only 1/2 of that of imported films. Polyvinyl alcohol (PVA) and soluble modified starch are the main raw materials of water-soluble printing film. The alcoholysis degree and polymerization degree of PVA are the main factors affecting the printing and post-processing properties of the film. Generally speaking, with the increase of alcoholysis degree, the solubility of the membrane in cold water decreases, and the solubility in hot water increases; With the increase of polymerization degree, the strength and solvent resistance of the film increase, the solubility in water decreases, and the tensile elongation of the film increases. Moisture and temperature have a great impact on the water-soluble film. It is best for the printing workshop to maintain constant temperature and humidity. Otherwise, due to the effect of moisture, the rewinding printing film is prone to anti sticking and stretching, resulting in a large amount of waste of film; During printing, the temperature of the drying channel is not allowed to exceed 50 degrees, otherwise the overprint will be inaccurate due to the softening and stretching of the film

the ink used for water-soluble film printing is special, and not all inks are suitable for PVA film printing. Abc001 produced by Zhejiang New Oriental ink is an ink specially used for water transfer printing. Compared with traditional plastic film printing, in addition to the above differences, the composition of the printing plate is also slightly different. Generally speaking, the number of overprint of the printing plate of water transfer printing will not exceed three colors, and the pattern is mainly some stripes such as wood grain. The last color needs to be coated with transparent varnish as the attachment basis of independent patterns, so as to prevent the floating loss of patterns caused by the dissolution of water-soluble films and affect the integrity of the printed patterns. Super force abc001 water transfer ink and its supporting varnish have good printability, excellent solvent release and excellent adhesion resistance. New Oriental ink has high impact strength and surface hardness in a relatively wide temperature range. The company is also the only manufacturer of water transfer (water coating) special ink in Chinese Mainland

plastic heat transfer printing and water transfer printing are new special printing processes derived from traditional plastic gravure printing, which expand gravure printing to the field of curved surface printing, inject new vitality into plastic gravure printing, and also provide new development opportunities for our color printing manufacturers. Due to the huge market potential, transfer printing technology has developed rapidly. However, due to the lack of relevant technologies and the insufficient supply of supporting raw materials, most of the transfer printing films in mainland China, especially the water transfer film, are mostly imported (including the results of the device analysis taken from the early clinical trials in Taiwan, suggesting that they are imported into the mainland), so its profit space is large, while the competition of ordinary color printing is fierce and abnormal, If our color printing manufacturers can speed up the technological development and occupy this market first by grabbing more than 20 "single champion" demonstration enterprises in the manufacturing industry, it will be a very good development opportunity. New Oriental ink company is willing to work together with our color printing manufacturers to plan for the development of national enterprises and jointly create a better tomorrow

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