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Holographic transfer film production and processing technology

the so-called holographic transfer technology refers to the production technology of using the strippability of chemical coating to transfer the aluminum layer with rainbow holographic effect evaporated on the film and molded to the paper surface to form metallized holographic paper. Because holographic transfer products have rainbow interference stripes, high metallic luster, and are degradable and easy to handle, they can meet the requirements of green environmental protection, so they have become the replacement products of foil burning and film covering products, and have broad market prospects. In recent years, the domestic holographic transfer material technology has been developing continuously, and the transfer projects have been launched continuously. However, due to the corresponding defects in the performance of holographic transfer products, there are still some concerns in the use of major cigarette factories, so the situation of large-scale use of holographic transfer packaging products has not been formed. Of course, the manufacturers of holographic transfer films also continue to study and improve the performance of products, and strive to achieve the green packaging effect satisfactory to users as soon as possible. Whether in terms of production process, product performance and use, holographic transfer process and the composition of chemical coating are the key technologies of holographic transfer production. If the maturity of the process technology and the use of raw and auxiliary materials are slightly inappropriate, the printing surface will have poor adhesion of the aluminum layer, cracking, color explosion at the die-cutting crease, poor ink adhesion and other phenomena. In October, 2002, our company introduced an Italian type 960 gravure printer, which can complete the tensile, peeling, tearing, tightening and other mechanical property experiments of the samples. This equipment can directly combine BOPP or pet transfer film with paper, dry, peel, print and put UV varnish on line, breaking the traditional production process of printing with transfer paper, It effectively avoids the problems on the printing surface of the above transfer packaging products, and can skip the horizontal plate seam of the holographic transfer film (positioning printing). Introduction to holographic transfer film

there are many kinds of holographic transfer films. In production, holographic transfer films with different prices and types should be selected according to different product structure, stripping effect, drying effect, ventilation volume of drying channel, length of drying channel and printing speed. The structures of commonly used OPP and pet holographic transfer films are shown in Figure 1 and Figure 2, and the properties of their base films are shown in Table 1

holographic transfer film production and processing technology

holographic transfer production and processing processes are various, and the process is relatively complex. The complete process flow is shown in Figure 3. For most holographic transfer film manufacturers, their products are a kind of substrate for printing. The processes to be completed include: batching, coating, molding, aluminizing, compounding, stripping, slitting and rewinding, etc. The processes to be completed for the equipment integrating wire compounding, transfer and printing include: compounding (holographic transfer film and paper), stripping (aluminum layer is transferred on the paper surface and separated from the base film), varnish coating and printing, which saves the process of purchasing transfer paper and then printing, and effectively reduces the paper cost. 1. In the batching process, the resin and solvent are mixed and stirred according to the formula and the corresponding COM port, and then the corresponding amount of dye is added according to the required color for color matching, and finally a colored or colorless coating liquid with certain viscosity and solid content (hereinafter referred to as color paste) is formed for coating. 2. The coating process uses the coating equipment (coater) to evenly coat the coating solution on the pet or BOPP base film to form a uniform and dense coating, which is used to separate the aluminum layer from the base film during stripping. In order to obtain a dense coating, several process standards need to be controlled during coating: ① viscosity of coating solution; ② Dry coating amount; ③ Coating effect; ④ Peeling property of coating. In addition, the coating speed should be adapted to the oven length of the coating equipment, hot air temperature and coating solvent, so as to ensure that the coating is fully leveled, and the solvent is volatilized as far as possible (to avoid residual odor). 3. The formation of holographic transfer products in the molding process cannot be separated from the molding process. Molding is the use of chemical coating thermal denaturation frequency tension and compression fatigue, change fatigue, detection and other six different detection methods: mechanical, electronic, electromagnetic, electro-hydraulic, electrical, electro-hydraulic servo and other six different loading methods; The range is 1n (5) 00kn. More than 1710 products of different specifications can be used to imprint the embossed pattern on the nickel plate on the coating or aluminum layer, including hard pressing and soft pressing. In order to get a clear and bright holographic pattern, we need to control the molding temperature, pressure, speed and other process parameters. Especially in the molding process, we must ensure that the indoor air is clean, because the base film itself has strong electrostatic adsorption. For example, if the base film is molded after absorbing dust, the holographic transfer film surface after aluminizing will leave small bright spots of non rainbow color. 4. Aluminizing process uses aluminizing equipment (aluminizing machine) to spray a uniform aluminum layer on the surface of the molded layer to form a holographic gloss surface effect with rainbow metal effect. The technical indicators to be controlled mainly include: ① the thickness of aluminum layer should be guaranteed to be 300 ~ 350A; ② The integrity of the aluminum layer shall be free of scratches, large bright holes, missing plating and other phenomena. 5. The process of bonding the holographic transfer film with the backing paper with an adhesive (water-based glue, environmentally friendly) in the composite process. Because the paper is breathable, it is generally used in the way of wet compounding, that is, first sizing, then fitting through the press roll, and then drying. The type of adhesive selected will affect the quality of the final product to a certain extent; The sizing method can be three roll sizing or corrugated roll sizing. In addition, the drying condition of the product is determined by the temperature of the oven and the running speed of the machine. The technical indicators that need to be controlled are: ① composite fastness; ② Surface flatness; ③ Peel integrity. 6. The stripping process separates the base film from the paper, leaving only the adhesive, aluminum layer and coating on the paper surface, but with glittering metallic luster, required colors and holographic patterns; The stripped pet or BOPP base film can be re coated and reused, greatly reducing the production cost. The quality of stripping process largely depends on the previous processes such as coating preparation, coating and compounding. The factors that need to be controlled by stripping itself include: ① the tightness of winding; ② Winding uniformity; ③ Surface abrasion; ④ Recycling management of recycling membrane, etc

performance of holographic transfer products

compared with foil and film coated products, whether the performance of holographic transfer products can reach or exceed the latter two is briefly introduced below. 1. The brightness of the product is covered with foil (aluminum foil, no base film). The product is divided into two types: positive mounting and reverse mounting. Film covered products are often used as bright products (with base film on the surface). At present, among holographic transfer products, the gloss of bright light transfer products cannot reach the brightness of bright aluminum coating composite products (belonging to polyester paperboard), but it has reached the brightness of holographic composite products; The gloss and matte effect of matte transfer products are basically the same as that of aluminum foil reverse mounting products. 2. Printability as a printing substrate, good printability is particularly important. For holographic transfer paper, this performance largely depends on the resin composition of the transfer coating. Good printability includes ink leveling effect and adhesion. At present, holographic transfer products can basically meet the requirements of printability. 3. Color explosion phenomenon after printing holographic transfer products, after post-processing, such as die-cutting indentation, placed for a period of time, there will be slight cracks in the ink layer and transfer layer at the indentation, which can transmit light. This phenomenon is unique to transfer products, but it will not occur in composite products, because there is a base film on the surface of composite products, and the surface has strong flexibility after die cutting and indentation. All the transferred products have slight color explosion, but the flexibility of the pulp fiber of the backing paper has a great influence on the color explosion degree. 4. High temperature resistance. Because high temperature is required during post printing processing, such as hot stamping, or in the OPP heat sealing stage of cigarette packaging, the surface resin of the transferred product is required to withstand a high temperature of 120 ~ 150 ℃, and can not change color or flower within 0.5 seconds. At present, the transferred product can basically meet the requirements. 5. Folding resistance requires that the transfer layer of holographic transfer paper will not be damaged after repeated folding, which mainly depends on the film-forming performance of the adhesive after drying. At present, the transferred products can basically meet this requirement. Exquisite and beautiful plastic bags with large amount of green packaging give people the enjoyment of beauty. The development of society and human progress also have higher requirements for environmental protection. Green holographic transfer new technology, combined with complex advanced production technology, reflects the current market demand. In order to be in line with international standards and responsible for human physical and mental health, we must start now and shoulder the sacred mission of serving human health. We should update products, introduce new technologies and create miracles

reprinted from: Printing Technology

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