Bronzing and its quality control
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With the improvement of the national economy and the development of the printing and packaging industry, people are required to package products: high-grade, exquisite, environmentally friendly and personalized. In the post-press processing of packaged products, the electro-aluminized hot stamping process has been loved by people for its unique surface finishing effect, and is applied in high-end packaging such as banknotes, cigarette labels, medicines and cosmetics. Electro-aluminum hot stamping refers to hot stamping, hot silver and other hot stamping materials. For the sake of convenience, the following hot stamping is called electro-aluminum hot stamping. Hot stamping has two main functions, one is surface decoration, which increases the added value of the product. Hobbies and glory are the national traditions of China, and the combination of bronzing and embossing techniques to show their luxury; second, to give products a higher anti-counterfeiting performance, using holographic positioning hot stamping trademark logo, anti-counterfeiting, insurance brand. At the same time, hot stamping is very representative of the individualization of the product packaging and is safe and environmentally friendly. Therefore, many high-end packaging have adopted the bronzing process, so how to improve the quality of bronzing? This article discusses from the following aspects.
First, the bronzing version of the high-quality hot stamping version is the primary factor to ensure the quality of bronzing. At present, the gilding plate is mainly made of photographic etching process and electronic engraving technology, and the material is commonly used in copper plate or zinc plate. The copper plate is fine, the surface finish and heat transfer effect are better than the zinc plate. The high-quality copper plate can improve the gloss and contour definition of the bronzing. The traditional photographic etching technology makes the gilding plate simple and low-cost, mainly used for text, thick lines and general images. For the finer, uneven image thickness, the gilding plate needs to use the second bad depth or adopt the electric carving technique. The electric gilding version can express rich and delicate layer changes, greatly expanding the packaging performance ability. This process is beneficial to environmental protection, but the investment in electric carving equipment is large. At present, the depth of engraving is not ideal enough, which is easy to cause bronzing. The holographic anti-counterfeiting hot stamping plate has high technical requirements. It was mainly produced in Taiwan or abroad, and the plate making cycle is long. It is only used for the packaging of fixed and bulky products. At present, there are several units in China's Shanxi Yuncheng, Beijing and Shanghai.
Second, bronzing equipment "Workers want to do their best, they must first sharpen their tools." The selection of bronzing equipment is a key factor in determining the quality of bronzing. The sheet-fed hot stamping machine has three models: flat flat, round flat and round pressed. The most widely used one is the flat press type, and the maximum bronzing speed is 5000 sheets/hour. The FOLLJET FBRl04 type bronzing machine is a circular pressing circle. With the design concept of the offset printing machine, the maximum hot stamping speed can reach 10,000 sheets/hour. It is currently the fastest single sheet bronzing machine in the world. The three embossing methods of round pressing, round pressing and flat pressing have their advantages and disadvantages: round pressing, round pressing and hot stamping are line pressure, the total pressure is small, and the pressure is easily completed with relatively small pressure. Large-area hot stamping, smooth movement, and round and round production efficiency is high, especially suitable for large-volume hot stamping, but because the copper plate arc surface processing is more difficult, the production cost is higher, the heating roller is also more difficult than the plane heating. The flat pressing operation is flexible and convenient, and is suitable for short-run products. Compared with imported bronzing equipment, domestic bronzing equipment has obvious advantages in performance and price. The price of domestically produced machine is only equivalent to l/5~1/4 of the price of similar foreign products, but the precision, stability and function of the imported machine are all overprinting. Obviously better than domestically produced machines, it is also more durable than domestically produced machines, and is more suitable for processing fixed-package high-end packaging products. Therefore, product type and batch size are the key to determining the selection of hot stamping equipment.
Third, bronzing adaptability The so-called bronzing fitness, refers to the choice of electrochemical aluminum model and bronzing speed, temperature, pressure and other factors to match. In the case of fixed hardware such as equipment, correct understanding of bronzing suitability is the most important means to improve the quality of bronzing. The following is an analysis of some quality problems reflected in the actual operation, in order to scientifically grasp the hot stamping suitability.
1. Hot stamping or hot stamping is related to various factors such as the surface characteristics of the print, the nature of the anodized aluminum, the hot stamping temperature and the pressure. 1 The surface of the printed matter is too dusty or the surface contains additives such as detacking agent and brightening paste, which will hinder the adsorption of the electrochemical aluminum and the paper. Solution: Surface de-powder treatment or solution in the printing process. 2 improper use of electrochemical aluminum directly affects the bronzing fastness. According to the size of the bronzing area, the type of the electroplated material should be considered comprehensively. The domestically produced anodized aluminum is mainly the Peacock brand series produced by Shanghai Shenyong Hot Stamping Material Co., Ltd. The imported electro-aluminized aluminum is mainly the PM and LK series of KURZ, the A, K and H series of Japan, and the SP series of KOLON of South Korea. . According to our practice and testing, the electrification of aluminum can mainly refer to the following classifications: bronzing on ordinary products (general ink color), electroforming aluminum with 88-1 type, KURZ PM type; cigarettes, cosmetics and other thick ink prints (including printing) Gold, printing silver) bronzing aluminum has 88-2 type; cigarettes, cosmetics packaging and other fine handwriting of electro-chemical aluminum has 88-3, 88-4, PM288, etc.; suitable for OPP or PET laminated paper As well as paperboard and glazing paper with UV ink, there are 88-4 type, K series, LK series and SP series. 8 does not correctly grasp the bronzing equipment and the matching between the pressing time and the hot stamping temperature, affecting the hot stamping fastness and the sharpness of the graphic outline. Due to the difference in equipment and hot stamping materials, the pressing time and hot stamping temperature are not the same. For example, the high-speed circular pressing machine is fast, the embossing line is in contact, and the hot stamping temperature is higher than the round flat or flat flat. Under normal circumstances, the round stamping temperature is between 190 ° C and 220 ° C, the round flat is about 130 ° C ~ 150 ° C, and the flat pressure is about 100 ° C ~ 120 ° C. Of course, the hot pressing time, hot stamping temperature and production efficiency are also largely restricted by the transfer performance of the electrochemical aluminum.
2. Anti-pull and pull-back means that the electro-aluminum removes the printing ink or the varnish of the printing after hot stamping. The main reason is that the ink on the surface of the printed product is not dried or the UV processing on the surface of the printed product is improperly processed, resulting in poor bonding of the ink on the surface of the printed product and the surface of the UV oil. Solution: After the product is dried, bronze. In addition, an electrochemical aluminum having a low separation force and excellent thermal transferability can be selected.
3. After the paste plate and hot stamping, the anodized color paste plate is mainly caused by the poor production of the bronzing plate, the slack of the electrified aluminum installation or the incorrect aluminum foil. After hot stamping, the discoloration of anodized aluminum is mainly caused by excessive hot stamping temperature. In addition, the wrinkling of the anodized aluminum is also likely to cause discoloration and discoloration of the hot stamping, which can be solved by appropriately lowering the temperature. For the round flattening machine type, a fan can be installed at the foil feeding position to keep the foil floated, avoiding the enamelling of the aluminum foil before the hot stamping.
4. The process arrangement is not proper, destroying the gloss of the surface of the electrochemical aluminum, and the outline of the graphic is faint. There is a need for gilding for film processing. People often worry that the gold foil is easy to be wiped off and then hot stamped and then coated. This easily causes: 1 film (especially matt film) will damage the surface gloss of the electrochemical aluminum, and it is not suitable to use water-soluble glue film. Otherwise, the surface of the electrochemical aluminum will be blackened, and at the same time, it will easily cause the gold powder to stick to the edge of the image to cause fading. 2 After bronzing, it is dented by pressure, and the glue is not easy to penetrate the surface of the electrochemical aluminum, which is easy to cause the separation of the OPP and the paper at the bronzing and affect the product quality. The correct process is to apply the film and then bronzing, and choose the electrochemical aluminum that matches OPP.
In short, there are many factors affecting the quality of bronzing, making high-quality bronzing plates, and correctly grasping the bronzing suitability is the key to improving the quality of bronzing.