Three-dimensional bronzing - the new favorite in the field of post-press packaging
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In recent years, with the improvement of the appearance and quality requirements of commodity packaging, printing technology and packaging technology have made great progress, and the post-press processing technology has achieved vigorous development, while the electro-aluminized hot stamping is used as a post-press. Part of the processing, the changes in the past few years are even greater. The continuous emergence of new technologies, new processes and a combination of various technologies has enabled the printed printed matter to achieve good results in gloss, three-dimensional, metallic and anti-counterfeiting properties after hot stamping, especially at present. A wide range of three-dimensional hot stamping technology makes the packaging of the goods look high-grade, exquisite and full of personality. At present, the technology is mainly used for greeting cards, bookmarks, trademarks, tobacco and alcohol packaging and various high-end packaging boxes.
Bronzing and three-dimensional bronzing
Hot stamping
Bronzing is the use of a certain pressure and temperature, using the template mounted on the hot stamping machine, so that the printed matter and the hot stamping plate are pressed together in a short time, and the metal foil or color pigment foil is transferred to the image according to the graphic requirements of the hot stamping template. The processing technology of the surface of the hot material. Since hot stamping is mainly gold and silver, it is often called bronzing. This technology is an important process to increase the visual effects and grades of labels, trademarks, cigarette packets, wine bags and various high-end packaging boxes. It can be divided into hot stamping and hot stamping. First hot stamping is to first stamp the printed aluminum foil layer on the blank substrate, and then print the graphic on the surface of the aluminum foil layer, which is mostly used for packaging printed matter requiring large area hot stamping. The first print and then hot is on the printed matter, the hot stamping on the parts that need hot stamping, which is a widely used process. From the hot stamping method, it can be divided into hot stamping technology and cold stamping technology. Hot stamping technology is the above-mentioned hot stamping process that requires a certain temperature and pressure to complete the transfer of anodized aluminum foil. Cold hot stamping technology is a process of transferring an electrochemical aluminum foil to a surface of a packaged print by applying a UV adhesive to a portion where the printed matter needs to be stamped. Each of these two methods has its own characteristics and meets the requirements of different products.
2. Three-dimensional bronzing
The three-dimensional bronzing technology is a composite technology combining bronzing technology and embossing embossing technology. It uses corrosion or engraving technology to make the embossing and embossing of the embossing and embossing into a top and bottom gravure and positive embossing to achieve hot stamping and The process of embossing technology is completed at one time. This process simultaneously completes bronzing and embossing, reducing waste in the processing process and overprinting, and improving productivity and product quality.
Since the three-dimensional bronzing is a combination of bronzing and embossing technology, the effect of the product is a three-dimensional embossed pattern, which cannot be printed on it. Therefore, it is necessary to adopt a process of printing and then ironing, and at the same time, due to its high precision. And high quality requirements, not suitable for cold stamping technology, but more suitable for hot stamping technology.
Stereo stamping technology and features
The three-dimensional bronzing technology is quite different from ordinary bronzing. In addition to the three-dimensional pattern that can be formed into a relief shape, there are differences in plate making, temperature control and pressure control.
Plate making
(1) ordinary hot stamping plate
The high-quality hot stamping plate is the guarantee of the quality of hot stamping. The common hot stamping plate is relatively simple to produce, mainly adopting photo-etching plate making process and electronic engraving plate making process. Commonly used plates are copper or zinc plates. Due to its fine texture, smooth surface, good heat transfer performance, wear resistance and pressure resistance, the copper plate is the current hot stamping plate. The use of high-quality copper plate can improve the gloss and clarity of hot stamping. Zinc plates can also be used for some hot stamping of hot stamping and low quality printing.
Photographic etching is a traditional production method with simple process, low cost and low precision. It is mainly suitable for text, thick lines and images with low quality requirements. The hot stamping plate produced by electronic engraving can enrich the delicate image layer and reproduce the images with fine lines and uneven thickness, but the relative cost is relatively high.
(2) three-dimensional hot stamping version
The production principle of the three-dimensional hot stamping plate is the same as that of the ordinary hot stamping plate, but it is more complicated than the ordinary printing plate. Because it has to form a three-dimensional relief pattern, the hot stamping plate is generally concave, and has a deep and shallow level change, and the depth is also hotter than ordinary. The plate is deeper and has higher precision. At present, the main method used in China is the copper plate photographic etching method. The advantage of this method is low cost and simple process, but it is only suitable for flat bronzing. Because of its poor stereoscopic effect, short service life and printing durability of only about 100,000 impressions, it is often used in some packagings that do not require high relief effect. On the product.
At present, the engraving brass version has been widely used in foreign countries. The scanner first scans the pattern to be stamped, stores the data into the computer, and then performs stereo engraving through the control of the computer and software to form a concave die with a rich three-dimensional pattern. Because it is controlled by a computer, it can form a very fine pattern, and it is more ideal for subtle parts. The printing durability can reach more than 1 million impressions, so it is very suitable for making three-dimensional hot stamping with high quality and large printing volume. Die intaglio. Of course, due to the need for high-end electronic engraving machines, scanners, computers and software, engineering and technical personnel, etc., the production cost is higher than the photographic corrosion method. It is precisely because of its complicated production and technical difficulty that it can better prevent the counterfeiting behavior of some unscrupulous manufacturers and have certain anti-counterfeiting functions. Therefore, for some long-term activities that require high-quality anti-counterfeiting functions, such as cigarette packets, wine bags, health care packaging and greeting cards, it is suitable for stereo hot stamping. In the past, such hot stamping plates needed to be processed abroad, the cost was high, the delivery was not timely, and the design effect was unsatisfactory. At present, a small number of manufacturers in China can process this hot stamping plate, which effectively reduces the cost, especially the direct communication between the processing manufacturer and the designer, can correctly understand the design intent, and thus obtain satisfactory results.
(3) Countertype letterpress
The three-dimensional bronzing is different from the ordinary bronzing. The bottom plate of the ordinary bronzing is flat and does not need to be specially made. The bottom plate of the three-dimensional bronzing must be a male die letter corresponding to the hot stamping plate, that is, the concave part of the hot stamping plate should be on the bottom plate. It is convex, and the height of the protrusion corresponds to the depth of the hot stamping. The method of making the counter-embossing is the same as that of the embossing of the male embossing. The commonly used materials are gypsum and glass fiber. If gypsum is used, it must be finished on the machine, so the process is more complicated, and it is troublesome to replace the bottom plate, but the cost is lower, and it is more commonly used in China. If glass fiber is used, it can be pre-made according to the model of the bronzing plate, and the positioning hole can be made with the processed copper plate to facilitate the replacement of the positioning.
The bottom plate relief is formed to conform to the hot stamping gravure to form a three-dimensional relief pattern, which must correspond exactly to the hot stamping plate. However, the three-dimensional bronzing is different from the embossing, and most of the embossing does not require heating, while the three-dimensional gilding must be heated at a high temperature. In hot stamping, as the temperature rises, the hot stamping plate will expand, while the temperature of the bottom plate relief remains almost the same, which will cause the hot stamping plate and the bottom plate relief to be unmatched, resulting in crushing the bottom mold. Or the phenomenon that it cannot be stamped. Therefore, in the production of the counter-embossing plate, the expansion ratio of the hot stamping plate should be fully considered to produce an accurate bottom plate relief.
2. Process requirements for three-dimensional bronzing
(1) Electrochemical aluminum foil
The electrochemical aluminum foil is generally composed of 4 to 5 layers of different materials, such as a base film layer (polyester film), a release layer, a colored layer (silver anodized aluminum has no colored layer), an aluminum plating layer, and an adhesive layer.
The main functions of each layer are:
The 1 base film layer mainly functions to support the other layers.
The function of the 2 peeling layer is to separate the electrochemical aluminum foil layer from the base layer, which determines the transferability of the electrochemical aluminum layer.
3 The main role of the colored layer is to display the color of the anodized aluminum and protect the underlayer. Common colors are: gold, silver, brown, light blue, black, red, green, etc., among which gold and silver are the two most commonly used.
4 The role of the aluminized layer is to present a metallic luster.
5 The role of the adhesive layer is to bond the hot stamping material.
The adhesive materials constituting the adhesive layer are different, and the adhesiveness is also different. In order to adapt to the different surface properties of different hot stamping materials, the electrochemical aluminum will use different bonding layers to form different types of anodized aluminum.
The hot stamping speed and quality are mainly affected by the peeling layer and the adhesive layer. If these coatings are not sensitive to heat, the hot stamping speed will be reduced accordingly. In the past, due to the limitation of heat transfer speed, the flat stamping speed was lower, which was less than 5,000 sheets per hour. However, some of the world's leading suppliers of anodized aluminum have made the production of anodized aluminum sufficient for the industry. Printing speed requirements, Swiss Bobst hot stamping machine has achieved a hot stamping speed of 7,500 sheets / hour. Since the three-dimensional bronzing forms an embossed pattern, the control of temperature, speed and pressure is different from that of ordinary bronzing. Therefore, the requirements for hot stamping foil are also different from ordinary bronzing. When using hot stamping foil, it should be used for stereo hot stamping. Hot stamping foil, but can not use ordinary hot stamping foil as a three-dimensional hot stamping, otherwise it will produce poor quality or other unexpected phenomenon.
(2) temperature, pressure, speed
Temperature, pressure and speed are the three major elements of hot stamping technology. Only by controlling the relationship between the three can control the quality of hot stamping. Since the three-dimensional bronzing is a gilding and embossing at one time, the temperature requirement is higher, the ordinary bronzing temperature is only 70 ° C ~ 90 ° C, and the three-dimensional bronzing can be completed at about 150 ° C. If the temperature is too low, the electrochemical aluminum adhesive layer and the peeling layer may not be fully melted, and the electroformed aluminum foil may not be completely transferred during hot stamping, resulting in hot stamping or exposure. If the temperature is too high, the paper will be over-deformed, the image will be confusing, the writing will be unclear, and even the phenomenon of discoloration of the electrochemical aluminum will occur. At the same time, the hot stamping plate may expand too much due to the high temperature, but it cannot be accurately and bottomed. The mold is combined to produce a bad stamping phenomenon. Therefore, temperature control is the first of the three major factors.
Hot stamping pressure refers to the pressure on the hot stamping plate. In the hot stamping process, the melted anodized aluminum adhesive layer is pressed to complete the transfer of anodized aluminum, so the magnitude and uniformity of the pressure directly affects the quality of the hot stamping. In addition to the requirement that the electro-aluminized foil is transferred to the surface of the printed matter, the three-dimensional gilding also uses a large pressure to press the three-dimensional embossed pattern on the hot stamping part, so the pressure is greater than that of ordinary hot stamping, which requires the strength of the hot stamping foil to be better. With a crush that can withstand strong pressure. Of course, this is not to say that the bigger the pressure, the better. It must be appropriate. If the pressure is too large or too small, you can't get a beautiful pattern. Excessive pressure may crush the hot foil and even crush the bottom mold and the printed matter to be burned; if the pressure is too small, the transfer of the hot foil may be incomplete or hot stamping, so that the three-dimensional relief of the concave and convex is not achieved. Quality requirements. Therefore, pressure control is also critical.
The hot stamping speed is actually the contact time between the hot stamping and the electrochemical aluminum, that is, the heating time of the electrochemical aluminum. The hot stamping speed is fast, the heating time is short, the hot stamping temperature drops rapidly, the temperature is too low, the hot stamping fastness is affected; the hot stamping speed is slow, the heating time is long, the hot stamping temperature is slow, and the hot stamping fastness is good. However, if the control is not good, the hot stamping temperature will be too high. Therefore, a suitable hot stamping speed is also a guarantee for obtaining a high quality hot stamping effect.
Round pressing and bronzing methods are commonly used for web line processing.
Since the round pressing circle is a line contact, the bubble phenomenon which may exist in the flat pressing bronzing can be completely avoided, and the speed is fast and the quality is good. However, because the bronzing plate and the bottom plate relief are round, the processing is difficult and the cost is high. The heat transfer effect of the circular bronzing plate is not very satisfactory, so the use is not extensive, and often it is long in some large output and high quality. The version of the live, such as cigarette packets, wine bags, health products, etc.
Bronzing and embossing technology are traditional post-press processing technologies, which are indispensable processes in packaging and decoration. Now the two are used together, which not only reduces the production process, but also improves the production efficiency. The decoration effect and anti-counterfeiting function have been greatly improved. Therefore, this technology now shows a strong development momentum. As various conditions mature, it will gradually replace the process of forming a three-dimensional gold pattern by two processes of bronzing and bump imprinting. The three-dimensional bronzing process will become a very promising decoration technology in the field of post-press packaging and decoration.