In recent years, with the continuous development of the technology level of the printing and packaging industry, the product quality has been continuously improved. In particular, in the highly competitive tobacco industry, in order to strengthen the artistic visual effects of cigarette packets, various processes have been continuously innovated, and their design level, printing quality, and post-press processing have also been continuously improved. In the various post-printing processes of cigarette packs, the bronzing process is popular and widely used because of its unique surface finish.
The principle and characteristics of bronzing
Bronzing is the use of hot-press transfer principle, the aluminum layer in the electro-aluminum transfer to the surface of the substrate to form a special metal effect, because the main material used in hot stamping is the electro-aluminum foil, so bronzing is also called electro-aluminum hot stamping. Electrochemical aluminum foil is usually composed of multiple layers of material, the substrate is often PE, followed by the separation coating, color coating, metal coating (aluminum) and glue coating.
The basic process of bronzing is in the state of pressure, that is, under the condition that the galvanized aluminum is pressed by the printing plate and the substrate is pressed, the galvanized aluminum is heated to melt the upper-melting silicone resin layer and the plastic sizing agent, and the heated and melted organic material is melted at this time. Silicone resin becomes less viscous, and special thermo-sensitive adhesives increase in viscosity after being melted by heat, causing the aluminum layer and the aluminum base film to be detached and transferred onto the substrate at the same time. As the pressure is removed, the adhesive rapidly cools and solidifies, and the aluminum layer is firmly attached to the substrate, completing a hot stamping process.
Hot stamping mainly has two functions: First, the surface decoration can increase the added value of the product. The combination of bronzing and embossing and other processing methods can show the strong decorative effect of the product. The second is to give the product a higher anti-counterfeiting performance, such as the use of holographic positioning stamping trademark logo.
After the product is gilded, the pattern is clear, beautiful, colorful, eye-catching, wear-resistant and weather-resistant. At present, the bronzing process applied on printed cigarettes accounts for more than 85% of the application. In the graphic design, bronzing can play a role of finishing touch and highlight design themes, and is particularly applicable to the decoration of trademarks and registered names.
The development of bronzing technology
In recent years, with the increase in the processing level of bronzing materials and bronzing plates, and the use of new machinery and equipment, domestic bronzing processes have also seen some new developments. High-speed hot stamping, three-dimensional hot stamping, holographic positioning hot stamping, and hot stamping and other printing processes have begun to be widely used in cigarette pack production.
Three-dimensional hot stamping: The three-dimensional hot stamping technology is a composite technology that combines hot stamping technology and embossing and embossing technology. It uses corrosion or engraving technology to make hot stamping and embossing graphics into a concave and a convex mold and a positive mold. Realize the process of one-time completion of stamping and embossing stamping technology. This process also completes bronzing and embossing at the same time, which reduces the number of waste products that are not allowed to be processed and overprinted, and increases production efficiency and product quality.
Since the product formed by three-dimensional hot stamping is an embossed three-dimensional pattern and cannot be printed on it, it is necessary to adopt a process of printing and hot stamping, and because of its high precision and high quality requirements, it is not suitable for cold stamping. Technical production. Three-dimensional hot stamping equipment is usually flat and round pressure round two, round flat way is not suitable for three-dimensional hot stamping.
The flattening and three-dimensional hot stamping equipment is represented by BOBST equipment. It is developing in the direction of high speed, high precision and easy use. It is the main model of three-dimensional hot stamping. Bobst hot stamping machine has reached 7500 / hour stamping speed, accuracy can be maintained within 0.1 ~ 4mm, is one of the most advanced hot stamping machine.
Round calendering methods are commonly used for web in-line processing. Because the circle rounding is line contact, bubble phenomena that may exist in flat bronzing can be completely avoided, and at the same time, the speed is fast and the quality is good. However, because the bronzing plate and the bottom plate are all round, the processing is difficult, the cost is high, and the heat transfer effect of the round bronzing plate is not very satisfactory. Therefore, it is not widely used, and it is often used in large quantities and high in quality. Edition live, such as cigarette packs, wine bags, health products, etc.
Due to the prevalence of high-end cigarettes in the form of soft packaging, the original post-printing process applied to white card paper has also shifted to soft paper. The embossing and positioning of soft paper will be performed by hot stamping and embossing in one process. The product has features such as full hot stamping, fine graphics, beautiful appearance, and no pressure convexity. However, this process technology is difficult, and the accuracy requirements for hot stamping, holographic film, and stamping machines are particularly high, and all operating indicators are very strict. Because of this, it is difficult to imitate and the degree of security is high.
Hologram stamping: Laser holograms are based on the principles of laser interference and are produced using spatial frequency coding. Laser holograms are widely used in the field of anti-counterfeiting due to their good color, distinct layers, vivid images, good optical transformation effects, and high information technology content.
The latest optical variable pattern technology has been clearly distinguished from the widely used HOLOGRAM holograms (three-dimensional holograms), which have machine recognition capabilities. The mechanism of holographic bronzing is that the hot melt adhesive layer and the separation layer on the holographic hot stamping material are heated and melted on the hot stamping device through a heated hot stamping die, and under the action of a certain pressure, the information layer holographic grating of the hot stamping material is applied. The stripe is separated from the PET substrate, so that the information layer of the aluminum foil is adhered to the bearing surface and integrated into a single body to achieve a perfect combination.
Holographic hot stamping mainly includes ordinary hot stamping and positioning hot stamping. Among them, special edition hologram positioning hot stamping frequently appeared on high-grade cigarette packs in the past two years. It means that the hologram of the specific part of the holographic anti-counterfeit stamping electro-aluminum is accurately stamped on the hot stamping device to a specific position of the cigarette pack by photoelectric recognition. Holographic positioning hot technology is very difficult, not only requires the printing plant equipped with high-performance, high-precision positioning of hot equipment, but also requires a high-quality special positioning hot stamping of aluminum, the production process must also be strictly controlled in order to produce qualified Cigarette products.
Cold bronzing process: cold bronzing technology is the first in the European and American printing industry in recent years, the first application of new technologies, is the cold state of the completion of the transfer of aluminum foil. Cold foiling uses a special type of electro-aluminum. The back of the foil is not glued. The adhesive is directly applied to the required decoration at the time of printing. When transferred, the aluminum foil adheres to the surface of the printed material under the action of the adhesive.
The cold stamping process first prints the UV ink. After drying, a special UV curing adhesive is printed on the surface of the ink where gold is to be gilded. The UV drying device is then used to evaporate the moisture in the adhesive and form a thin layer of high-viscosity, pressure-sensitive adhesive. Then, under the action of a pair of metal rollers, the aluminum foil is brought into contact with the adhesive and pressed into one. Due to the large adhesive force between the adhesive and the aluminum foil, the parts where the aluminum foil and the adhesive are in contact with the adhesive remain on the surface of the printed matter when being discharged, and become integrated with the printed matter, while the other parts of the aluminum foil are discharged as the conventional bronzing. This completes the first part of the bronzing technique. Because the aluminum foil pattern transferred on the printed product floats on the surface of the printed product and has poor firmness, it is necessary to apply light or film on the printed surface to protect the aluminum foil pattern.
Compared with the traditional bronzing process, the cold bronzing process has the advantages of high speed and energy saving. The material has a wide range of applications and can perform cold bronzing on thermal paper and a part of film material. The use of a generic flexo plate instead of an expensive metal plate cylinder greatly reduces the production cost and cycle time of the bronzing plate and at the same time reduces the contamination during the corrosion of the metal plate.
The cold bronzing process is limited by the conditions of adhesives, metal foils, etc. There are also some shortcomings, such as: After the cold bronzing of the printing products, it must be glazing or laminating to protect the gilt pattern, which increases the cost and the complexity of the process. The cold-stencil process is not suitable for use on thin film materials such as PVC and PE that have shrinkage characteristics. Due to the poor leveling of the UV adhesive, the smoothness of the surface after drying is poor, resulting in poor brightness of the surface of the metal foil transferred thereon, and there is a phenomenon of diffuse reflection, which is not as effective as the conventional hot stamping process. The key technology of the cold stamping process is UV adhesives and special aluminum foils. The development prospects are broad.
First hot post-printing process: In order to highlight the specific patterns and logos on cigarette packs, in recent years, some printing companies have launched a new process of first stamping anodized aluminum, and then printing patterns on the anodized aluminum, which can make the topic of cigarette packs even more Lively and lively.
The first hot stamping is the new idea of ​​the cigarette label design and printing industry. The application of this process is very demanding for the aluminum. The key to the process is that the stamping of the aluminum foil must be firm. During the printing, the aluminum foil must not be pulled back by the printing ink. The anti-pull not only affects the quality of the cigarette pack, but also the anti-pulled aluminum will quickly accumulate on the blanket. If it is light, the image dots will be lost, and the image will not be printed on the screen. With the operation of the machine, the electro-aluminum powder Will be transmitted 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, select the appropriate aluminum, to ensure that the aluminum can be firmly attached to the surface of the paper.
In addition to the production of accurate bronzing position, surface smooth and bright, pressure balance, uniform, no blistering, no paste version and other requirements, but also special requirements bronzing pattern edge can not be marked indentation, bronzing of aluminum in the hot stamping surface to have Good adhesion, and no obvious scratches and scratches. As we all know, the bronzing process is actually a process in which paper is heated and pressurized. For white cards and glass cards, special attention should be paid to the protection of semi-finished products. Various unfavorable factors of paper deformation should be minimized in the production process, which will greatly help the smooth progress of post-bronze processes and the improvement of the product qualification rate.
Micro-embossing process: This process is used in the aluminum foil paper graphics part of the micro-press plate with a variety of fine lines required, the product obtained has the effect of hot stamping, embossing, metal texture is strong.
Bronzing quality control
At present, despite the emergence of various new bronzing processes, the traditional galvanized aluminum bronzing technology as an important process in postpress processing has not been neglected due to its unique decorative effect and mature process operation, but has been even more affected by people. More attention and preference.
The traditional hot stamping aluminum hot stamping foil mainly adopts the method of heating and pressing to transfer the pattern or text to the surface of the stamped material. To complete this process, you need a stamping machine, a template engraved with special words or patterns, the required temperature for heating, the pressure required for the transfer, and the corresponding 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 in order to achieve the desired hot stamping effect.
Hot Stamping: High-quality hot stamping is the primary factor in guaranteeing the quality of stamping. At present, the production of bronzing edition mainly adopts photographic etching technology and electronic engraving technology, and the material is mostly copper plate or zinc plate. Copper plate material is delicate, surface finish, heat transfer effect are better than zinc plate, the use of high-quality copper plate can increase the bronzing graphic gloss and outline definition.
The traditional photographic corrosion technology makes the bronzing plate with simple process, low cost and short service life. It is mainly used for hot stamping of characters, thick lines, and general images. The bronzing plate used for finer, unequal thickness of pictures and texts needs to use the second time. Or use electronic engraving technology. The electric carving production bronzing edition can express rich and delicate level changes and greatly expand the performance of the packaging. The process is conducive to environmental protection, but electric carving equipment investment is relatively large, the depth of the current sculpture is not ideal, easy to cause hot stamping "glue", but its high resistance to India, suitable for long version of cigarette bag type live. The holographic anti-counterfeiting and bronzing plate production technology requires higher technical requirements and the plate making cycle is longer. It is only used for the packaging of fixed and large-scale products.
Hot Stamping Equipment: The selection of hot stamping equipment is a key factor in determining the quality of stamping. Sheet-fed hot stamping machines are flat-pressed, round-pressed, and circular-pressed. There are three types of sheet-fed stamping machines.
Three types of embossing hot stamping machines have their own advantages and disadvantages. Circular round and round flattening Hot stamping is performed with line pressure, and the total pressure is small. It can easily complete large-area on-site hot stamping with a relatively small pressure and operates smoothly. The circular press type has high production efficiency and is suitable for hot stamping of large quantities of live parts. Since the copper circular plate surface is difficult to process and the production cost is high, the heating roller is also more difficult to heat than the flat surface. Flat press operation is flexible and convenient, and it is more suitable for short version products.
Compared with imported gilding equipment, domestic bronzing equipment has obvious advantages in terms of performance and price, but the overprint accuracy, stability, and function of imported machines are obviously better than that of domestic machines. They are also more durable than domestic machines and are more suitable for fixed bulk high-end packaging products. Processing.
Hot gilding suitability: The so-called bronzing suitability refers to the matching of the type of galvanized aluminum and the factors such as bronzing speed, temperature, and pressure. In the case of fixed hardware such as equipment, proper control of bronzing suitability is the most important means of improving the quality of bronzing. The hot stamping process is as follows: a stamping version is prepared for hot stamping, a hot stamping process parameter is adjusted, a stamping hot stamping sample is officially stamped.
From the gilding process, it can be seen that the three basic elements of bronzing are: temperature, pressure, and stamping time. In order to obtain the ideal hot stamping effect, the process parameters such as hot stamping temperature, hot stamping pressure, and hot stamping speed must be properly mastered and matched. In addition, the quality of raw materials related to bronzing must also be guaranteed, such as the adaptability of substrates for stamping, the properties of electro-aluminum materials, and the quality of hot stamping plates. If something goes wrong, it will affect the final hot stamping effect.
Hot stamping faults and exclusion
Hot stamping is not true or hot stamping is not true: This is related to the surface characteristics of the printed material, the nature of the electrochemical aluminum, the hot stamping temperature and pressure and other factors.
1 The surface of the print is dusted too much. The printing ink is not dry or the surface contains additives such as a releasant and a bright oil, which will hinder the adsorption of the aluminum foil and the paper. Can be printed on the surface of the powder or in the printing process.
2 Improper use of anodized aluminum will also directly affect the fastness of hot stamping. According to the size of the bronzing area, the characteristics of the stamped material should be considered in consideration of what type of galvanized aluminum is selected. There are many types of electro-aluminum materials in the market, and various types of substrates have different materials and the most appropriate range of hot stamping. They are mainly distinguished by adhesion and peeling during use. When the operator chooses the anodized aluminum material with poor fastness and tightness to perform the hot stamping, the hot stamping pattern on the cigarette pack will cause the misprinting and gold drop.
When selecting an electro-aluminum, the following classifications can be mainly referred to: General hot stamping (generally black) Electro-aluminum type 88 type I, KURZ PM type: Prints of cigarettes, cosmetics, etc. (including gold and silver) There are 88-2 type foil stamping aluminum; cigarettes, cosmetic packaging and other fine stroke hot stamping of electro-aluminum are 88-3, 88-4 type, PM288, etc. Suitable for 0PP or PET lamination paper and UV ink board , glazing paper and other products stamping electro-aluminum 88-4 type, K series, LK series, and SP series.
3 It is not possible to correctly grasp the matching between hot stamping equipment, hot press time and hot stamping temperature, which affects the fastness of the hot stamping and the sharpness of the graphic outline.
Due to the different equipment and hot stamping materials, the hot pressing time and hot stamping temperature are not the same. For example, a high-speed circular press has a fast speed and the embossing line contacts. The hot stamping temperature is higher than that of a round press or a flat press. Under normal circumstances, the round hot stamping temperature is between 190% and 220°C, the roundness is about 130°C～150°C, and the flat pressure is about 100°C～120°C. Of course, hot pressing time, hot stamping temperature and production efficiency are also largely constrained by the transferability of the electro-aluminum. Should also pay attention to check whether the pressure is balanced, some of the graphics are not on the hot stamping but also check whether the bronzing version is damaged.
Anti-pull: Reverse pull refers to the electro-aluminum after the stamping, which will pull the printing ink or printing oil on the print. The main reason is that the ink on the surface of the printed product is not dry, or the post-processing of UV on the surface of the printed product is improperly handled, resulting in the combination of the ink on the surface of the printed product, UV oil, and the surface of the paper.
It should be dried and then hot stamped. In addition, it is possible to use an electro-aluminum material with a low separation force and excellent thermal transferability.
Paste-printing and hot stamping of electro-aluminum discoloration pastes are mainly caused by poor bronzing production, looseness of the installation of anodized aluminum, or improper foiling of anodized aluminum. Discoloration of electro-aluminum after hot stamping is mainly caused by high stamping temperature. In addition, the wrinkling of anodized aluminum can also cause uneven color shift and hot stamping, which can be solved by appropriately lowering the temperature. For the round-flattening model, fans can be installed at the foil feeding place to keep the foils from floating, avoiding the aluminum foil touching the hot stamping and scorching before the stamping.
Destruction of the surface luster of the aluminum foil, the outline of the graphic is made imaginary: the foil stamping process requires foil stamping, and the foil is first hot stamped and re-laminated because it is feared that the gold foil will be easily wiped off. This can easily cause the film (especially the matt film) to destroy the surface luster of the electrodeposited aluminum. It is also not suitable to use water-soluble glue to coat the film. Otherwise, the surface of the electrodeposited aluminum will be black, and it will easily cause the gold powder to stick to the edge of the image and cause it to become false. phenomenon. After the bronzing, the dent is caused by the pressure, and the glue is not easy to penetrate the surface of the galvanized aluminum, which may easily cause separation of the bronzing unit 0PP from the paper and affect the product quality. The correct process is to apply foil and then hot stamping, choose the matching of aluminum and OPP.
In short, there are many factors affecting the quality of bronzing, making high-quality bronzing plates, and correctly grasping bronzing suitability is the key to improving the quality of bronzing. Cigarette bag production is different from other publications and has its unique requirements for printing and processing. The requirements for quality, decoration, and anti-counterfeiting are relatively high, and the batch production volume is large. Before the production of the company, it is necessary to carefully read the construction list, perform maintenance and maintenance of the machine daily, master the properties of the electrochemical foil, and be familiar with the relationship among temperature, pressure, and speed. Only in this way can the quality of cigarette packs be guaranteed.
The principle and characteristics of bronzing
Bronzing is the use of hot-press transfer principle, the aluminum layer in the electro-aluminum transfer to the surface of the substrate to form a special metal effect, because the main material used in hot stamping is the electro-aluminum foil, so bronzing is also called electro-aluminum hot stamping. Electrochemical aluminum foil is usually composed of multiple layers of material, the substrate is often PE, followed by the separation coating, color coating, metal coating (aluminum) and glue coating.
The basic process of bronzing is in the state of pressure, that is, under the condition that the galvanized aluminum is pressed by the printing plate and the substrate is pressed, the galvanized aluminum is heated to melt the upper-melting silicone resin layer and the plastic sizing agent, and the heated and melted organic material is melted at this time. Silicone resin becomes less viscous, and special thermo-sensitive adhesives increase in viscosity after being melted by heat, causing the aluminum layer and the aluminum base film to be detached and transferred onto the substrate at the same time. As the pressure is removed, the adhesive rapidly cools and solidifies, and the aluminum layer is firmly attached to the substrate, completing a hot stamping process.
Hot stamping mainly has two functions: First, the surface decoration can increase the added value of the product. The combination of bronzing and embossing and other processing methods can show the strong decorative effect of the product. The second is to give the product a higher anti-counterfeiting performance, such as the use of holographic positioning stamping trademark logo.
After the product is gilded, the pattern is clear, beautiful, colorful, eye-catching, wear-resistant and weather-resistant. At present, the bronzing process applied on printed cigarettes accounts for more than 85% of the application. In the graphic design, bronzing can play a role of finishing touch and highlight design themes, and is particularly applicable to the decoration of trademarks and registered names.
The development of bronzing technology
In recent years, with the increase in the processing level of bronzing materials and bronzing plates, and the use of new machinery and equipment, domestic bronzing processes have also seen some new developments. High-speed hot stamping, three-dimensional hot stamping, holographic positioning hot stamping, and hot stamping and other printing processes have begun to be widely used in cigarette pack production.
Three-dimensional hot stamping: The three-dimensional hot stamping technology is a composite technology that combines hot stamping technology and embossing and embossing technology. It uses corrosion or engraving technology to make hot stamping and embossing graphics into a concave and a convex mold and a positive mold. Realize the process of one-time completion of stamping and embossing stamping technology. This process also completes bronzing and embossing at the same time, which reduces the number of waste products that are not allowed to be processed and overprinted, and increases production efficiency and product quality.
Since the product formed by three-dimensional hot stamping is an embossed three-dimensional pattern and cannot be printed on it, it is necessary to adopt a process of printing and hot stamping, and because of its high precision and high quality requirements, it is not suitable for cold stamping. Technical production. Three-dimensional hot stamping equipment is usually flat and round pressure round two, round flat way is not suitable for three-dimensional hot stamping.
The flattening and three-dimensional hot stamping equipment is represented by BOBST equipment. It is developing in the direction of high speed, high precision and easy use. It is the main model of three-dimensional hot stamping. Bobst hot stamping machine has reached 7500 / hour stamping speed, accuracy can be maintained within 0.1 ~ 4mm, is one of the most advanced hot stamping machine.
Round calendering methods are commonly used for web in-line processing. Because the circle rounding is line contact, bubble phenomena that may exist in flat bronzing can be completely avoided, and at the same time, the speed is fast and the quality is good. However, because the bronzing plate and the bottom plate are all round, the processing is difficult, the cost is high, and the heat transfer effect of the round bronzing plate is not very satisfactory. Therefore, it is not widely used, and it is often used in large quantities and high in quality. Edition live, such as cigarette packs, wine bags, health products, etc.
Due to the prevalence of high-end cigarettes in the form of soft packaging, the original post-printing process applied to white card paper has also shifted to soft paper. The embossing and positioning of soft paper will be performed by hot stamping and embossing in one process. The product has features such as full hot stamping, fine graphics, beautiful appearance, and no pressure convexity. However, this process technology is difficult, and the accuracy requirements for hot stamping, holographic film, and stamping machines are particularly high, and all operating indicators are very strict. Because of this, it is difficult to imitate and the degree of security is high.
Hologram stamping: Laser holograms are based on the principles of laser interference and are produced using spatial frequency coding. Laser holograms are widely used in the field of anti-counterfeiting due to their good color, distinct layers, vivid images, good optical transformation effects, and high information technology content.
The latest optical variable pattern technology has been clearly distinguished from the widely used HOLOGRAM holograms (three-dimensional holograms), which have machine recognition capabilities. The mechanism of holographic bronzing is that the hot melt adhesive layer and the separation layer on the holographic hot stamping material are heated and melted on the hot stamping device through a heated hot stamping die, and under the action of a certain pressure, the information layer holographic grating of the hot stamping material is applied. The stripe is separated from the PET substrate, so that the information layer of the aluminum foil is adhered to the bearing surface and integrated into a single body to achieve a perfect combination.
Holographic hot stamping mainly includes ordinary hot stamping and positioning hot stamping. Among them, special edition hologram positioning hot stamping frequently appeared on high-grade cigarette packs in the past two years. It means that the hologram of the specific part of the holographic anti-counterfeit stamping electro-aluminum is accurately stamped on the hot stamping device to a specific position of the cigarette pack by photoelectric recognition. Holographic positioning hot technology is very difficult, not only requires the printing plant equipped with high-performance, high-precision positioning of hot equipment, but also requires a high-quality special positioning hot stamping of aluminum, the production process must also be strictly controlled in order to produce qualified Cigarette products.
Cold bronzing process: cold bronzing technology is the first in the European and American printing industry in recent years, the first application of new technologies, is the cold state of the completion of the transfer of aluminum foil. Cold foiling uses a special type of electro-aluminum. The back of the foil is not glued. The adhesive is directly applied to the required decoration at the time of printing. When transferred, the aluminum foil adheres to the surface of the printed material under the action of the adhesive.
The cold stamping process first prints the UV ink. After drying, a special UV curing adhesive is printed on the surface of the ink where gold is to be gilded. The UV drying device is then used to evaporate the moisture in the adhesive and form a thin layer of high-viscosity, pressure-sensitive adhesive. Then, under the action of a pair of metal rollers, the aluminum foil is brought into contact with the adhesive and pressed into one. Due to the large adhesive force between the adhesive and the aluminum foil, the parts where the aluminum foil and the adhesive are in contact with the adhesive remain on the surface of the printed matter when being discharged, and become integrated with the printed matter, while the other parts of the aluminum foil are discharged as the conventional bronzing. This completes the first part of the bronzing technique. Because the aluminum foil pattern transferred on the printed product floats on the surface of the printed product and has poor firmness, it is necessary to apply light or film on the printed surface to protect the aluminum foil pattern.
Compared with the traditional bronzing process, the cold bronzing process has the advantages of high speed and energy saving. The material has a wide range of applications and can perform cold bronzing on thermal paper and a part of film material. The use of a generic flexo plate instead of an expensive metal plate cylinder greatly reduces the production cost and cycle time of the bronzing plate and at the same time reduces the contamination during the corrosion of the metal plate.
The cold bronzing process is limited by the conditions of adhesives, metal foils, etc. There are also some shortcomings, such as: After the cold bronzing of the printing products, it must be glazing or laminating to protect the gilt pattern, which increases the cost and the complexity of the process. The cold-stencil process is not suitable for use on thin film materials such as PVC and PE that have shrinkage characteristics. Due to the poor leveling of the UV adhesive, the smoothness of the surface after drying is poor, resulting in poor brightness of the surface of the metal foil transferred thereon, and there is a phenomenon of diffuse reflection, which is not as effective as the conventional hot stamping process. The key technology of the cold stamping process is UV adhesives and special aluminum foils. The development prospects are broad.
First hot post-printing process: In order to highlight the specific patterns and logos on cigarette packs, in recent years, some printing companies have launched a new process of first stamping anodized aluminum, and then printing patterns on the anodized aluminum, which can make the topic of cigarette packs even more Lively and lively.
The first hot stamping is the new idea of ​​the cigarette label design and printing industry. The application of this process is very demanding for the aluminum. The key to the process is that the stamping of the aluminum foil must be firm. During the printing, the aluminum foil must not be pulled back by the printing ink. The anti-pull not only affects the quality of the cigarette pack, but also the anti-pulled aluminum will quickly accumulate on the blanket. If it is light, the image dots will be lost, and the image will not be printed on the screen. With the operation of the machine, the electro-aluminum powder Will be transmitted 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, select the appropriate aluminum, to ensure that the aluminum can be firmly attached to the surface of the paper.
In addition to the production of accurate bronzing position, surface smooth and bright, pressure balance, uniform, no blistering, no paste version and other requirements, but also special requirements bronzing pattern edge can not be marked indentation, bronzing of aluminum in the hot stamping surface to have Good adhesion, and no obvious scratches and scratches. As we all know, the bronzing process is actually a process in which paper is heated and pressurized. For white cards and glass cards, special attention should be paid to the protection of semi-finished products. Various unfavorable factors of paper deformation should be minimized in the production process, which will greatly help the smooth progress of post-bronze processes and the improvement of the product qualification rate.
Micro-embossing process: This process is used in the aluminum foil paper graphics part of the micro-press plate with a variety of fine lines required, the product obtained has the effect of hot stamping, embossing, metal texture is strong.
Bronzing quality control
At present, despite the emergence of various new bronzing processes, the traditional galvanized aluminum bronzing technology as an important process in postpress processing has not been neglected due to its unique decorative effect and mature process operation, but has been even more affected by people. More attention and preference.
The traditional hot stamping aluminum hot stamping foil mainly adopts the method of heating and pressing to transfer the pattern or text to the surface of the stamped material. To complete this process, you need a stamping machine, a template engraved with special words or patterns, the required temperature for heating, the pressure required for the transfer, and the corresponding 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 in order to achieve the desired hot stamping effect.
Hot Stamping: High-quality hot stamping is the primary factor in guaranteeing the quality of stamping. At present, the production of bronzing edition mainly adopts photographic etching technology and electronic engraving technology, and the material is mostly copper plate or zinc plate. Copper plate material is delicate, surface finish, heat transfer effect are better than zinc plate, the use of high-quality copper plate can increase the bronzing graphic gloss and outline definition.
The traditional photographic corrosion technology makes the bronzing plate with simple process, low cost and short service life. It is mainly used for hot stamping of characters, thick lines, and general images. The bronzing plate used for finer, unequal thickness of pictures and texts needs to use the second time. Or use electronic engraving technology. The electric carving production bronzing edition can express rich and delicate level changes and greatly expand the performance of the packaging. The process is conducive to environmental protection, but electric carving equipment investment is relatively large, the depth of the current sculpture is not ideal, easy to cause hot stamping "glue", but its high resistance to India, suitable for long version of cigarette bag type live. The holographic anti-counterfeiting and bronzing plate production technology requires higher technical requirements and the plate making cycle is longer. It is only used for the packaging of fixed and large-scale products.
Hot Stamping Equipment: The selection of hot stamping equipment is a key factor in determining the quality of stamping. Sheet-fed hot stamping machines are flat-pressed, round-pressed, and circular-pressed. There are three types of sheet-fed stamping machines.
Three types of embossing hot stamping machines have their own advantages and disadvantages. Circular round and round flattening Hot stamping is performed with line pressure, and the total pressure is small. It can easily complete large-area on-site hot stamping with a relatively small pressure and operates smoothly. The circular press type has high production efficiency and is suitable for hot stamping of large quantities of live parts. Since the copper circular plate surface is difficult to process and the production cost is high, the heating roller is also more difficult to heat than the flat surface. Flat press operation is flexible and convenient, and it is more suitable for short version products.
Compared with imported gilding equipment, domestic bronzing equipment has obvious advantages in terms of performance and price, but the overprint accuracy, stability, and function of imported machines are obviously better than that of domestic machines. They are also more durable than domestic machines and are more suitable for fixed bulk high-end packaging products. Processing.
Hot gilding suitability: The so-called bronzing suitability refers to the matching of the type of galvanized aluminum and the factors such as bronzing speed, temperature, and pressure. In the case of fixed hardware such as equipment, proper control of bronzing suitability is the most important means of improving the quality of bronzing. The hot stamping process is as follows: a stamping version is prepared for hot stamping, a hot stamping process parameter is adjusted, a stamping hot stamping sample is officially stamped.
From the gilding process, it can be seen that the three basic elements of bronzing are: temperature, pressure, and stamping time. In order to obtain the ideal hot stamping effect, the process parameters such as hot stamping temperature, hot stamping pressure, and hot stamping speed must be properly mastered and matched. In addition, the quality of raw materials related to bronzing must also be guaranteed, such as the adaptability of substrates for stamping, the properties of electro-aluminum materials, and the quality of hot stamping plates. If something goes wrong, it will affect the final hot stamping effect.
Hot stamping faults and exclusion
Hot stamping is not true or hot stamping is not true: This is related to the surface characteristics of the printed material, the nature of the electrochemical aluminum, the hot stamping temperature and pressure and other factors.
1 The surface of the print is dusted too much. The printing ink is not dry or the surface contains additives such as a releasant and a bright oil, which will hinder the adsorption of the aluminum foil and the paper. Can be printed on the surface of the powder or in the printing process.
2 Improper use of anodized aluminum will also directly affect the fastness of hot stamping. According to the size of the bronzing area, the characteristics of the stamped material should be considered in consideration of what type of galvanized aluminum is selected. There are many types of electro-aluminum materials in the market, and various types of substrates have different materials and the most appropriate range of hot stamping. They are mainly distinguished by adhesion and peeling during use. When the operator chooses the anodized aluminum material with poor fastness and tightness to perform the hot stamping, the hot stamping pattern on the cigarette pack will cause the misprinting and gold drop.
When selecting an electro-aluminum, the following classifications can be mainly referred to: General hot stamping (generally black) Electro-aluminum type 88 type I, KURZ PM type: Prints of cigarettes, cosmetics, etc. (including gold and silver) There are 88-2 type foil stamping aluminum; cigarettes, cosmetic packaging and other fine stroke hot stamping of electro-aluminum are 88-3, 88-4 type, PM288, etc. Suitable for 0PP or PET lamination paper and UV ink board , glazing paper and other products stamping electro-aluminum 88-4 type, K series, LK series, and SP series.
3 It is not possible to correctly grasp the matching between hot stamping equipment, hot press time and hot stamping temperature, which affects the fastness of the hot stamping and the sharpness of the graphic outline.
Due to the different equipment and hot stamping materials, the hot pressing time and hot stamping temperature are not the same. For example, a high-speed circular press has a fast speed and the embossing line contacts. The hot stamping temperature is higher than that of a round press or a flat press. Under normal circumstances, the round hot stamping temperature is between 190% and 220°C, the roundness is about 130°C～150°C, and the flat pressure is about 100°C～120°C. Of course, hot pressing time, hot stamping temperature and production efficiency are also largely constrained by the transferability of the electro-aluminum. Should also pay attention to check whether the pressure is balanced, some of the graphics are not on the hot stamping but also check whether the bronzing version is damaged.
Anti-pull: Reverse pull refers to the electro-aluminum after the stamping, which will pull the printing ink or printing oil on the print. The main reason is that the ink on the surface of the printed product is not dry, or the post-processing of UV on the surface of the printed product is improperly handled, resulting in the combination of the ink on the surface of the printed product, UV oil, and the surface of the paper.
It should be dried and then hot stamped. In addition, it is possible to use an electro-aluminum material with a low separation force and excellent thermal transferability.
Paste-printing and hot stamping of electro-aluminum discoloration pastes are mainly caused by poor bronzing production, looseness of the installation of anodized aluminum, or improper foiling of anodized aluminum. Discoloration of electro-aluminum after hot stamping is mainly caused by high stamping temperature. In addition, the wrinkling of anodized aluminum can also cause uneven color shift and hot stamping, which can be solved by appropriately lowering the temperature. For the round-flattening model, fans can be installed at the foil feeding place to keep the foils from floating, avoiding the aluminum foil touching the hot stamping and scorching before the stamping.
Destruction of the surface luster of the aluminum foil, the outline of the graphic is made imaginary: the foil stamping process requires foil stamping, and the foil is first hot stamped and re-laminated because it is feared that the gold foil will be easily wiped off. This can easily cause the film (especially the matt film) to destroy the surface luster of the electrodeposited aluminum. It is also not suitable to use water-soluble glue to coat the film. Otherwise, the surface of the electrodeposited aluminum will be black, and it will easily cause the gold powder to stick to the edge of the image and cause it to become false. phenomenon. After the bronzing, the dent is caused by the pressure, and the glue is not easy to penetrate the surface of the galvanized aluminum, which may easily cause separation of the bronzing unit 0PP from the paper and affect the product quality. The correct process is to apply foil and then hot stamping, choose the matching of aluminum and OPP.
In short, there are many factors affecting the quality of bronzing, making high-quality bronzing plates, and correctly grasping bronzing suitability is the key to improving the quality of bronzing. Cigarette bag production is different from other publications and has its unique requirements for printing and processing. The requirements for quality, decoration, and anti-counterfeiting are relatively high, and the batch production volume is large. Before the production of the company, it is necessary to carefully read the construction list, perform maintenance and maintenance of the machine daily, master the properties of the electrochemical foil, and be familiar with the relationship among temperature, pressure, and speed. Only in this way can the quality of cigarette packs be guaranteed.
patent pencil
Tonglu shangmei pen industry co.,ltd , https://www.shangmeipenindustry.com