With the improvement of the processing level of bronzing materials and bronzing plates, as well as the use of new machinery and equipment, the domestic bronzing process has also achieved some new developments. High-speed bronzing, three-dimensional bronzing, holographic positioning bronzing, and printing after bronzing have begun to be widely used in the production of cigarette packets.
The three-dimensional bronzing technology is a composite technology of bronzing technology and concave-convex embossing technology. It is a method of etching and engraving to make the embossing and the embossing of the embossing and the embossing. The process of embossing technology is completed at one time. This process simultaneously completes bronzing and embossing, reduces waste in the processing process and overprinting, and improves production efficiency and product quality.
Since the effect of the product formed by the three-dimensional bronzing is a three-dimensional embossed pattern, it can no longer be printed on it. Therefore, it is necessary to adopt a process design of pre-printing and hot-pressing. At the same time, due to its high precision and high quality requirements, it is not suitable for cold stamping. Technical production. Three-dimensional bronzing equipment usually has two kinds of flat pressing and round pressing, and the round flattening method is not suitable for three-dimensional hot stamping.
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.
Due to the popular soft packaging form of high-end cigarettes, the mature post-press processing technology originally applied to white cardboard has also been transferred to soft paper. The process of embossing and positioning of soft paper is to complete the process of bronzing and embossing in a process. The product has the characteristics of full bronzing, fine graphics, beautiful appearance and no pressure convexity. However, this process is technically difficult, and the precision requirements for hot stamping plates, holographic films, and hot stamping machines are extremely high, and various operational indexes are strict. Because of this, it is difficult to imitate and the degree of anti-counterfeiting is high.
Hologram bronzing: Laser holograms are fabricated using spatial frequency coding based on the principle of laser interference. The laser hologram is widely used in the field of anti-counterfeiting because of its good color, obvious level, vivid image, good optical transformation effect and high information technology content.
The latest optical variable pattern technology has been clearly distinguished from the widely used HOLOGRAM hologram (three-dimensional hologram), which has machine recognition. The mechanism of holographic bronzing is to heat and melt the hot melt adhesive layer and the separation layer on the holographic hot stamping material through a hot stamping die on a hot stamping device, and under certain pressure, the information layer holographic grating of the hot stamping material is used. The stripe is separated from the PET substrate, so that the information layer of the aluminum foil is bonded to the surface of the ironing surface and integrated into one to achieve a perfect combination.
Holographic hot stamping mainly has two kinds of common hot stamping and positioning hot stamping. Among them, the special version of the hologram positioning hot stamping has appeared frequently on high-grade cigarette packets in the past two years. It refers to the accurate printing of a hologram on a specific part of the holographic anti-counterfeit anodized aluminum to a specific position of the cigarette package by photoelectric recognition on the hot stamping device. Hologram positioning hot technology is very difficult, not only requires the printing factory to be equipped with high-performance, high-precision special positioning hot equipment, but also requires high-quality special positioning hot stamping aluminum, the production process must be strictly controlled to produce qualified Tobacco package products.
Cold bronzing process
Cold bronzing process: Cold bronzing technology is the first new technology achievement in the printing industry in Europe and America in recent years. It is the transfer of electrified aluminum foil under cold pressure. Cold bronzing uses special anodized aluminum. The back side is not coated with glue. The adhesive is directly applied to the position to be decorated when printing. When transferred, the electrochemical aluminum adheres to the surface of the printed matter under the action of the adhesive.
The cold stamping process first prints UV inks. After drying, a special UV-curing adhesive is printed on the surface of the ink surface where bronzing is required; the moisture in the adhesive is evaporated by a UV drying device to form a high-viscosity thin pressure-sensitive adhesive layer. Then, under the action of a pair of metal rollers, the aluminum foil is brought into contact with the adhesive and pressed into one body. Since the adhesive force between the adhesive and the aluminum foil is large, when the waste is discharged, the portion where the aluminum foil contacts the adhesive remains on the surface of the printed matter, and is integrated with the printed matter, and the other portions of the aluminum foil are discharged like the traditional hot stamping. Thereby completing the first part of the bronzing technology. Since the aluminum foil pattern transferred on the printed matter floats on the surface of the printed matter, the degree of firmness is poor, so it is necessary to light or cover the surface of the printed matter to protect the aluminum foil pattern.
Compared with the traditional bronzing process, the cold bronzing process is fast and saves energy: the material is suitable for a wide range of applications, and can be used for cold bronzing on heat-sensitive paper and a part of film materials. The use of a general flexo plate instead of an expensive metal plate cylinder greatly reduces the cost and cycle of the hot stamping plate while reducing contamination during the corrosion of the metal plate.
The cold stamping process is limited by the conditions of adhesives, metal foils, etc., and there are also some shortcomings, such as: printing cold stamping must be glazed or coated to protect the bronzing pattern, increasing the cost and complexity of the process. The cold-hot process is not suitable for use on film materials such as PVC and PE which have shrinkage properties. Due to the poor leveling property of the UV adhesive, the surface smoothness after drying is poor, and the surface of the metal foil transferred thereon is poor in brightness and diffuse reflection phenomenon, and the effect is not as good as the conventional hot stamping process. The key technology of the cold stamping process is UV adhesives and special anodized aluminum foil, which has broad development prospects.
First hot stamping process: In order to highlight the specific patterns and logos on the cigarette packs, in recent years, some printers have introduced a new process of first stamping anodized aluminum and then printing patterns on the anodized aluminum, which can make the cigarette pack theme more Vivid and lively.
The first hot stamping is a new idea in the tobacco label design printing industry. The application of this process has high requirements for electrochemical aluminum. The key to the process is that the stamping of the electrochemical aluminum must be firm. The aluminum should not be pulled back by the printing ink during printing. The reverse pulling not only affects the quality of the cigarette pack, but also the reversed pull of the electrochemical aluminum will quickly accumulate on the blanket, which will cause the image dot to be lost, and the partial image will not be printed. As the machine runs, the electrochemical aluminum powder is still Will be transferred to the ink roller system to accelerate the wear of the ink roller. Therefore, this process should be based on the characteristics of printing paper, and choose the appropriate anodized aluminum to ensure that the electrochemical aluminum can be firmly attached to the surface of the paper.
In addition to the position of the hot stamping, the surface is smooth and bright, the pressure is balanced, uniform, no foaming, no paste, etc., but also the edge of the hot stamping pattern can not be obviously indented. The hot stamping aluminum has to be on the hot stamping surface. Good adhesion and no obvious rubbing and scratching. As everyone knows, the hot stamping process is actually a process in which the paper is heated and stressed. For white cards and glass cards, special attention should be paid to the protection of semi-finished products. In the production process, various unfavorable factors of paper deformation should be minimized, which will greatly help the smooth progress of the bronzing process and the improvement of the product qualification rate.
Micro embossing process
Micro-embossing process: This process is to press various micro-presses on the image of the aluminum foil to press various fine lines. The obtained products have the effect of hot stamping and embossing, and the metal texture is very strong.
Hot stamping quality control
At present, despite the emergence of various new bronzing processes, the traditional anodized aluminum hot stamping technology, as an important process in post-press processing, with its unique decorative effects and mature process operations, has not been left out, but has been more More attention and preference.
Conventional thermo-piezoelectric aluminum hot stamping foils use heat and pressure to transfer patterns or text to the surface of the hot stamped material. To complete this process, you need a stamping machine, a stencil with special text or graphics, the temperature required to heat it, and the pressure required to transfer it for the appropriate amount of time. It should be noted that when hot stamping different materials, the appropriate type of anodized aluminum should be selected, and the appropriate temperature, pressure and hot stamping time should be selected to achieve the desired hot stamping effect.
Hot stamping version: The high quality bronzing 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 mostly 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 corrosion technology makes the bronzing plate simple in process, low in cost and short in service life. It is mainly used for bronzing of text, thick lines and general images: for the finer, uneven image thickness, etc. Or use electronic engraving technology. The electric engraving production of the bronzing plate can express rich and delicate layer changes, greatly expanding the performance of the packaging. The process is conducive to environmental protection, but the investment in electro-engraving equipment is relatively large. At present, the depth of engraving is not ideal enough, which is easy to cause bronzing “paste plate”, but its high printing durability is suitable for long-life activities of cigarette packets. The holographic anti-counterfeiting hot stamping plate has high technical requirements and a long plate making cycle, and is only used for packaging of fixed and bulky products.