Three-dimensional hot stamping technology in anti-counterfeiting packaging
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At present, hot stamping anti-counterfeiting technology has been widely used in anti-counterfeiting packaging of various tobacco and alcohol, food, medicine and cosmetics. Among them, three-dimensional hot stamping technology has obvious advantages for anti-counterfeiting packaging products. Here, the anti-counterfeiting packaging technology is introduced to introduce the related problems of the three-dimensional hot stamping technology.
The meaning of three-dimensional hot stamping technology
Three-dimensional hot stamping technology is also called bump hot stamping technology, three-dimensional hot stamping technology, three-dimensional hot stamping technology. The three-dimensional hot stamping, that is, the hot stamping process, has a distinctly high-dimensional image that protrudes above the surface of the printed matter. It is different from flat hot stamping and different from embossing. In essence, both hot stamping and embossing work simultaneously on printed matter. Therefore, the three-dimensional hot stamping technology can also be regarded as a "hot stamping + bump" combination process, which is a composite technology combining hot stamping technology and concave and convex embossing technology, that is, hot stamping and embossing using etching or engraving techniques. The graphic is made into a female gravure and a male die letter which are matched up and down, and the hot stamping and embossing embossing technology is completed at one time.
Anti-counterfeiting principle of three-dimensional hot stamping technology
Three-dimensional hot stamping, ie hot stamping and embossing, is completed once. Using hot stamping plate and bottom die, under a certain pressure and temperature, the printed substrate is plastically deformed, and at the same time, the electrochemical aluminum foil is transferred to printed matter or other substrates. The plastic deformation occurs, thus completing the artistic processing of the printed surface. The key technology of the three-dimensional hot stamping process is to produce a precise three-dimensional hot stamping plate, a counter-die and an easy-to-fit positioning system.
The three-dimensional hot stamping anti-counterfeiting technology not only can make the surface of the substrate imprinted with anodized aluminum, but also can display various colors and complicated fine patterns on the surface. At the same time, the anti-counterfeiting mark can be mixed in the middle of the complicated pattern according to the customer's requirements. And can make the pattern appear three-dimensional. Therefore, the three-dimensional hot stamping anti-counterfeiting technology can not only increase the decorative effect of the packaging (including the hot stamping effect and the stereoscopic effect of the graphic and text), but also has the characteristics of strong concealment, easy identification, and difficulty in being copied (complex and difficult). Has a good anti-counterfeiting effect.
Three-dimensional hot stamping process equipment selection
The three-dimensional hot stamping process needs to complete the two processes of hot stamping and embossing at one time. Therefore, the positioning accuracy of the bronzing machine is relatively high, and the flat pressing and bronzing machine is generally used, and the round pressing and bronzing machine can also be used. At present, the three-dimensional hot stamping machines are mainly Bobst hot stamping machines (flat flat) and Stowe hot stamping machines (circular pressing).
1. Flat pressing and ironing machine
The flat-pressing three-dimensional hot stamping machine is represented by the Swiss Bobst bronzing machine. It has the characteristics of high speed, high precision and convenient use. It is a commonly used three-dimensional hot stamping machine with a hot stamping speed of 7,500 sheets per hour, and a hot stamping hologram of 6,000 sheets per hour. The hot stamping accuracy can be maintained. Within ±0.1mm, it is the main type of three-dimensional bronzing, and it is also one of the most advanced hot stamping machines in the world. At the same time, if a holographic positioning probe is added and the precision control of the electrochemical aluminum is matched, the holographic positioning hot stamping can be completed.
The obvious disadvantage of the flat pressing and ironing machine is that the hot stamping effect is not as good as that of the round pressing hot stamping machine when printing large-area hot stamping. This is because the pressure of the flat pressing and stamping machine is the plane pressure, and the round pressing and stamping machine The pressure is linear pressure.
2. Round pressing hot stamping machine
Round press hot stamping machines are commonly used for web line processing. Due to the continuous rotation and line contact working mode, compared with the flat pressing hot stamping, the advantages of the round pressing hot stamping process are mainly reflected in the high speed, high production efficiency, good hot stamping quality, and can completely avoid flat pressing. Bubble phenomenon that may exist in the print.
The round and round stereo ironing equipment is represented by Stora, Germany. The maximum speed of FBR104 single-sheet round-pressing hot stamping machine can reach 12,000 sheets/hour, holographic hot stamping can reach 8000 sheets/hour, holographic hot stamping precision can reach 0.4mm, and holographic hot stamping and ordinary hot stamping can be completed at one time. Work with embossing, etc., and has the laser holographic electrochemical aluminum foil seam jumping function, which is extremely efficient. In addition, the machine's anodized aluminum guide shaft can produce a layer of air cushion, which can make the electrochemical aluminum free of friction transmission, and the tension is very small at high speed, so that the tensile deformation of the electrochemical aluminum is small.
However, the circular pressing and bronzing machine also has obvious shortcomings, mainly manifested in: 1 hot stamping plate is expensive, and the requirements are very high, must consider the thermal expansion coefficient of the material, the wear of the plate and other factors; 2 pairs of hot stamping foil High requirements, must be able to transfer quickly, and currently domestic aluminum foil is still difficult to meet this requirement, must use expensive imported materials to meet the requirements of high-speed production; 3 hot stamping plate and bottom die are round, difficult to process, The cost is high, and the heat transfer effect of the circular hot stamping plate is not very satisfactory. Therefore, it is often used in some long-running products with high output and high quality (such as tobacco and alcohol packaging, health care packaging, etc.); 4 hot stamping and embossing It must be implemented on both units, even if the registration error is not considered, at least two sets of molds are required, which incurs an increase in cost.
Selection and production of three-dimensional hot stamping plates
The key to the hot stamping process is plate making, and the high quality hot stamping plate guarantees the quality of hot stamping. Ordinary hot stamping plates are relatively simple to make, mainly using photographic corrosion plate making process and electronic engraving plate making process. Commonly used plates are copper plate or zinc plate.
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 hot stamping plate making process. The three-dimensional hot stamping plate should form a three-dimensional embossed pattern. The hot stamping plate is generally concave, and has a deep and shallow level change, and the depth is deeper than the ordinary hot stamping plate, and the precision is higher. The graphic part of the three-dimensional hot stamping plate should be rounded lines, which is different from the right angle line of the ordinary flat hot stamping plate. Therefore, the three-dimensional hot stamping plate needs secondary processing after corrosion, which is technically difficult, which also makes the three-dimensional hot stamping. Printing technology has a good anti-counterfeiting function.
1. Selection of plates
Commonly used hot stamping plates are metals such as brass, red copper, steel, zinc and magnesium. At present, the main method used in China is the copper plate photo etching method, and the brass plate electronic engraving plate has been widely used abroad.
(1) Corrosion copper plate. Corrosion copper plate thickness is generally 2mm, riveting it to another thick copper plate or aluminum plate. This hot stamping plate has lower cost and simple process, but has poor stereoscopic effect, short service life (generally less than 100,000 impressions), fine The hot stamping quality of the graphic is poor, generally suitable for flat hot stamping and some packaging products that do not require high relief effect. The corrosive copper plate is used for anti-counterfeiting packaging products with relatively few processing and anti-counterfeiting effects.
(2) Electric engraving brass version. Due to its high hardness and ideal processing properties, brass is the preferred material for stereo stamping. Currently widely used in foreign countries is the CNC engraving brass version, the thickness is generally up to 7mm, through the relevant software control, the pre-scanned image according to the customer's requirements for accurate three-dimensional engraving. The hot stamping plate thus produced is matched with the prefabricated bottom plate relief, which is suitable for three-dimensional hot stamping, and can ensure the hot stamping precision of the fine pattern on the printed matter and the sharpness of the edge of the graphic. Engraved brass version has a long service life (up to 1 million prints or more), high production efficiency, good repeatability, high hot stamping accuracy (especially for small patterns), suitable for making complex graphics, and very good for hot stamping. However, its production cost is very high, and it is generally suitable for long-lived three-dimensional hot stamping. The three-dimensional hot stamping process of the anti-counterfeiting packaging products adopts the electric carved brass version, which has better anti-counterfeiting effect.
2. Computer numerical control engraving and plate making technology
The three-dimensional hot stamping plate can be made by computer numerical control engraving and plate making technology. It adopts computer numerical control engraving and plate making, which can meet the high requirements of hot stamping in level and detail than the traditional etching process. 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. Female die intaglio.
Because CNC engraving and plate making needs to be equipped with high-grade electronic engraving machine, scanner, computer and software, engineering and technical personnel, etc., its production cost is much higher than photographic corrosion method. It is precisely because of its complicated production, technical difficulty and high cost, it can better prevent the counterfeiting behavior of some unscrupulous manufacturers and have certain anti-counterfeiting functions. For some high-quality and long-term activities that require anti-counterfeiting functions, such as high-grade tobacco and alcohol packaging, cosmetic packaging, health care packaging, etc., it is more suitable to use the computer numerical control engraving brass version for three-dimensional hot stamping processing.
Selection of the bottom mold
When the relief effect of the three-dimensional hot stamping product reaches a certain depth, it is necessary to have a bottom die relief. Both the three-dimensional hot stamping and the embossing embossing require the cooperation of the bottom mold, but the fundamental difference between the two requires the bottom mold: "The three-dimensional hot stamping process is always kept warm", which is also the primary working condition of the three-dimensional hot stamping. There are two main types of bottom molds, namely: traditional plaster punches and prefabricated punches of new polymer materials. Stereo hot stamping should generally use prefabricated punches of new polymer materials. The punch is made by pre-forming a punch with glass fiber, polyvinyl chloride or polystyrene. The plastic plate is superposed on the mold (die) and placed in a molding machine with a heating and cooling system. Adjust the temperature and pressure to obtain a punch that has the same shape as the mold (female) and has the opposite curvature.
One of the important features of the three-dimensional hot stamping process is that it must be kept warm during the hot stamping process. Since the three-dimensional hot stamping plate has a certain expansion variable when the temperature rises, the temperature of the bottom mold remains at room temperature, which will cause the hot stamping plate and the bottom mold to not cooperate during the actual working process, thereby causing the crushing of the bottom mold or Can't print. Therefore, in the production of the counter-embossing plate, the expansion ratio of the hot stamping plate should be fully considered, and precise calculation and new materials and special bottom-die manufacturing techniques are required to make the produced bottom mold and the hot stamping process to produce the expansion variable of the three-dimensional hot stamping. The version still has a fine and perfect match.
GPS
Compared with the embossing of the concave and convex, the fineness of the three-dimensional hot stamping is more strict, and the effect is more obvious. In order to change the inaccurate adjustment and positioning error during the assembly process of the imprinting plate and the bottom mold, the three-dimensional hot stamping generally adopts an easy positioning system consisting of a marking hole and a position display to shorten the installation of the embossing mold. Adjust the time to ensure the processing effect is beautiful. For example, the easy-to-fit positioning system developed and patented by KURZ can be used. With the marking hole and position display, it is easy to install the hot stamping plate and the bottom die, the plate loading time is shortened, and the installation is faster.
Key factors affecting quality
1. Influence of equipment accuracy
The three-dimensional hot stamping process requires two concave and convex stencils. It is necessary to use a high-precision bronzing machine, otherwise the punch will be damaged. For example, although the circular flattening hot stamping equipment has high precision, it is difficult to operate. It is necessary to pay special attention to the thickness of the drum liner and the height of the lower plate to ensure that the line speed of the equipment is consistent, otherwise it will cause slippage. Ordinary round flat stamping equipment is less used for three-dimensional hot stamping.
2. The influence of the quality of the electrochemical aluminum foil
The hot stamping speed and quality are mainly affected by the release coating and the coating layer. These coatings are sensitive to heat and can improve the hot stamping speed. Therefore, the aluminum alloy produced by the advanced adhesive formula can meet the high-speed hot stamping. The requirements to reduce the cost of hot stamping.
The development trend of three-dimensional hot stamping technology
Hot stamping is a commonly used process for finishing the surface of printed matter. To achieve better quality and effect of hot stamping, especially for high-grade commodity packaging and anti-counterfeiting packaging products, hot stamping technology is generally used, especially three-dimensional hot stamping technology. The development trend of three-dimensional hot stamping technology is mainly reflected in the following three aspects.
1. Online stereo stamping
The improvement of the chemical properties of the three-dimensional hot stamping foil provides a reliable guarantee for the sharp increase of the hot stamping speed. Therefore, the stereo hot stamping process has been completed online, and the application of the inline hot stamping process will become more and more common in the future. In addition, sheetfed folding carton printing is moving in the direction of web printing, which also creates conditions for the in-line three-dimensional stamping process.
2. After hot stamping
That is, after hot stamping, printing is performed on the hot stamping foil. The hot stamping process also benefits from the improvement and improvement of the chemical properties of the hot stamping foil, so that UV ink can be used for printing on hot stamping foil. The hot stamping process can provide better decorative effects and enhance the visual appeal of the image. After hot stamping, the opaque or transparent color ink is overprinted to achieve special effects, especially to enhance its anti-counterfeiting effect.
3. Improve hot stamping speed and reduce cost
The high price of the rotary three-dimensional hot stamping cylinder is a high cost factor of the three-dimensional hot stamping process, and the price of the three-dimensional hot stamping drum is gradually decreasing, which provides favorable conditions for the reduction of the cost of the three-dimensional hot stamping. In the past, due to the limitation of the three-dimensional hot stamping speed, most of the three-dimensional hot stamping work was completed offline, and at present, the speed can reach 7500-12000 sheets/hour whether it is a flat pressing hot stamping machine or a round flat stamping machine. The continuous increase in production speed will greatly reduce the cost of three-dimensional hot stamping.