Introduction: The hot stamping process is widely used in cosmetic packaging materials, because it does not use ink, it is environmentally friendly and clean, and it is suitable for various materials such as plastic, glass, paper, etc. The hot stamping process is used in plastic bottles, glass bottles, cartons and other cosmetic packages. The surface of the material is applied, and it is an important part of the post-processing technology of the packaging material. This article introduces the basic knowledge of bronzing for the reference of friends:
Hot stamping process: It is a process in which metal foil is transferred to the surface of printed matter or other objects by hot pressing to increase the decorative effect.
Cold bronzing process: It is a process of transferring metal foil to the surface of printed matter or other objects without heating, but only through the force of pressure, bonding and peeling, to achieve a decorative effect.
Make the printing surface have a variety of colors and metallic patterns at the same time, and it can also combine different pressing effects. In addition to its surface decoration function, bronzing also has an important role in anti-counterfeiting.
Advantages and disadvantages of bronzing process
1) Hot stamping products on the whole surface, no ink residue;
2) There is no unpleasant smell such as ink, and the air is pollution-free;
3) The color pattern can be hot stamped at one time, reducing loss;
4) The process is simple, the production management and flow are smooth, and the product quality insurance coefficient is large;
5) Wide processing range, suitable for paper, wood, plastic, leather, etc.
1) Not suitable for hot stamping substrates with uneven surface or matte surface;
2) Metal, glass, ceramic, nylon and other products are generally not suitable for hot stamping, unless they are painted or screen printed;
3) Matching the pattern color and the background color of the workpiece: during hot stamping, the color of anodized aluminum (gold, silver, copper, inner red, inner blue) has a strong hiding power, even if the background color of the workpiece is black, it can be completely covered; but When using lighter color transfer paper such as white and yellow for hot stamping on a black background, its covering effect is not as good as pad printing and screen printing.
Plain hot stamping
1. The production process of ordinary flat hot stamping plate (commonly known as “shangban”)
The quality of the hot stamping plate is an important factor affecting the quality of hot stamping. The production of ordinary flat hot stamping plates mainly adopts the photo-etching plate-making process and the electronic engraving plate-making process. The former has simple production process and low cost, but the precision of the hot stamping plate produced is also relatively low, which is limited to hot stamping text, thick lines and quality requirements. Not high patterns; the hot stamping plate produced by the latter has high precision, can express the image level in a rich and delicate manner, and can reproduce the fine lines and uneven thickness of graphics and texts well. The cost is relatively high, and the scope of application is relatively high. It is more extensive, suitable for cigarette packs, wine packs, medicine packs, cosmetic packaging, etc., which require higher hot stamping effects.
2. Material selection of ordinary flat hot stamping plates
Commonly used plates for flat hot stamping plates are copper plates or zinc plates. The copper plate has fine texture, smooth surface, good thermal conductivity, wear resistance and pressure resistance, and is not easy to deform, and is favored by most plate manufacturers. For the information of the printed product manufacturers with a small quantity and low quality requirements, the hot stamping plate can be a zinc plate.
3. Material selection of ordinary flat hot stamping base plate (commonly known as “lower plate”)
At present, most ordinary flat hot stamping plate making factories only produce hot stamping plates, but due to different hot stamping media, plate making factories cannot provide suitable matching master plates. Therefore, most carton packaging companies are faced with choosing which material for ordinary flat surfaces. The problem of hot stamping the master plate. Comprehensive hot stamping media, printing durability, adaptability, convenient operation and other factors are over-packed. The summary is as follows: For copperplate paper printings, used PS plates, steel squeegee blades, and kraft paper with a thickness of about 0.5mm can be used as the base plate for ordinary flat hot stamping; for gold cardboard, silver cardboard, and laser cardboard , Glass cardboard, you can use 0.8-1.5mm thick insulating board, steel squeegee blade as the base plate; no matter what kind of material the base plate is used, it is indispensable to padded pressure paper underneath.
4. Process requirements for ordinary flat hot stamping
1) Anodized aluminum
Ordinary anodized aluminum is composed of 4 to 5 layers of different materials, including a base film layer, a peeling layer, a colored layer, a aluminum plating layer, and an adhesive layer. The hot stamping speed and quality are mainly affected by the peeling layer and the adhesive layer. If the two coatings are not sensitive enough to heat, the hot stamping speed will be reduced accordingly.
2) Temperature, pressure, speed
These are the three major elements of the hot stamping process. Only by controlling the relationship between the three can the quality of hot stamping be controlled. The temperature of ordinary flat hot stamping is generally 70～110℃. If the temperature is too low, the adhesive layer and peeling layer of the anodized aluminum cannot be fully melted, and the anodized aluminum cannot be completely transferred during hot stamping, causing the hot stamping to fail; if the temperature is too high, the paper Severe deformation, easy to cause problems such as inaccurate overprinting, slurried graphics, handwriting, and discoloration of the anodized aluminum. The hot stamping pressure should be adjusted according to the ability of the hot stamping medium and the upper and lower plates. Hot stamping speed: manual hot stamping is generally controlled at 600-700 sheets/hour; automatic hot stamping machine is generally controlled at 3500~5000 sheets/ Hour.
It can complete hot stamping and embossing at the same time, reducing the processing procedures and the amount of waste caused by inaccurate overprinting, and improving production efficiency and product quality. It is mainly used in various high-end cigarette packages, wine packages, medicine packages, cosmetics packages, etc. Hot stamping of carton packaging.
1. Definition (also called concave-convex ironing, three-dimensional ironing, embossing)
Three-dimensional hot stamping means that the images and texts processed by hot stamping have obvious high-level three-dimensional layers, which are prominent on the surface of the printed matter. Three-dimensional hot stamping technology is a composite technology that combines hot stamping technology and embossing technology. It can also be regarded as a “hot stamping + embossing” combined process, which uses corrosion or engraving technology to make the hot stamping and embossing graphics into one top and bottom The matched female gravure and male relief realize the process of bronzing and embossing technology at one time.
Three-dimensional hot stamping is the completion of hot stamping and embossing at one time: using a hot stamping plate and a bottom mold, under a certain pressure and temperature, the substrate of the printed matter is plastically deformed, and at the same time, the electrochemical aluminum foil is printed on the printed matter or other substrates to produce plasticity Deformed parts, so as to perform artistic processing on the surface of the printed matter. The electro-engraved three-dimensional hot stamping plate has high precision, and the hot stamping effect is very exquisite. Electrically engraved brass plates are commonly used in post-press processing, and are controlled by computer software to perform three-dimensional engraving on pre-scanned images. The bronzing plates made in this way can be used for three-dimensional bronzing with prefabricated relief plates. The key to this process is plate making. The graphic part of the hot stamping plate should have rounded corners, which is different from the right-angled lines of the ordinary flat hot stamping plate. Therefore, the three-dimensional hot stamping plate needs secondary processing after corrosion, which is more technically difficult. .
1) Production of concave-convex hot stamping plate (commonly known as “upper plate, negative plate”)
The production principle of concave-convex hot stamping plate is more complicated than that of ordinary flat hot stamping plate, and because it also needs to realize the concave-convex effect, the concave-convex hot stamping plate has deep and shallow layer changes, and the embossing depth of graphics and text is also deeper than that of ordinary flat hot stamping plate. Some, higher precision. At present, all domestic plate making factories adopt computer-engraved brass plate making technology and typesetting, and the embossed hot stamping plates produced are rich in layers, fine, and high in printing durability.
2) Production of concave-convex hot stamping master (commonly known as “lower version, positive version”)
The base plate used for embossing hot stamping must be a male relief plate corresponding to the embossing hot stamping plate. At present, the plate making factory usually chooses glass fiber as the base plate material, which can be pre-made according to the embossed hot stamping plate model and matched with the processed copper plate. Positioning hole layout design to facilitate replacement and positioning.
The master plate must correspond exactly to the concave-convex hot stamping plate, but during the concave-convex hot stamping process, with the gradual increase in temperature, the concave-convex hot stamping plate will expand, while the temperature of the master plate remains unchanged, which will cause the concave-convex hot stamping The plate does not match the base plate, causing the base mold to be crushed or the hot stamping pattern to be incomplete. Therefore, the expansion rate of the concave-convex hot stamping plate should be fully considered when making the master plate to ensure a more accurate master plate.
3) Process requirements for embossing hot stamping
① Anodized aluminum. Special anodized aluminum for embossing hot stamping should be used instead of ordinary anodized aluminum.
②Temperature, pressure, speed. Concave and convex hot stamping needs to complete the hot stamping and pressing of the embossed press at one time, so the hot stamping temperature is very high, usually at 110～140℃, but too high temperature will cause problems such as pasting and discoloration of the anodized aluminum. It will cause the gravure hot stamping plate to swell too much, and it will not be able to accurately match with the base plate, resulting in poor hot stamping. It can be said that hot stamping temperature is the primary factor that determines the success or failure of embossing hot stamping.
Holographic positioning hot stamping
Holographic positioning hot stamping is a special hot stamping process, which uses the anti-counterfeiting pattern on the anodized aluminum, which can not only greatly improve the anti-counterfeiting performance of the product, but also improve the quality of the product. It is mainly used for various carton packaging that requires anti-counterfeiting function.
Bronzing anodized aluminum is a holographic image, and the image needs to be accurately positioned on the printed product. Holographic hot stamping mainly includes ordinary hot stamping and positioning hot stamping.
Holographic positioning hot stamping is a combination of laser holographic image anti-counterfeiting technology with good anti-counterfeiting effect and hot stamping decoration technology, so that the product has an added anti-counterfeiting performance while improving the finishing and decoration. The laser hologram is made according to the principle of laser interference and the method of spatial frequency coding. Because the laser hologram has magical colors, obvious layers, vivid images, changeable optical transformation effects, and high information and technology content.
The hot-melt adhesive layer and the separation layer on the holographic hot stamping material are heated and melted on the hot stamping equipment through the heated hot stamping die head. Under a certain pressure, the holographic grating stripes of the information layer of the hot stamping material and the PET base The material is separated, so that the aluminum foil information layer and the ironing surface are bonded and integrated to achieve a perfect combination.
1. Production of holographic positioning hot stamping plate
The production process of the holographic positioning hot stamping plate is basically the same as the ordinary flat hot stamping plate and the concave-convex hot stamping plate.
2. Process requirements for hot stamping
Holographic positioning hot stamping must use special laser anodized aluminum and advanced registration detection system, which determines that the holographic positioning hot stamping has stricter and higher requirements for the hot stamping material and the performance of the hot stamping machine than other hot stamping methods.
① Adjustment of the registration detection electric eye: In the holographic positioning and hot stamping, the adjustment of the detection electric eye (sensor) is the most important step. The more common adjustment method is: in the clear state, the indicator light is on when the cursor is encountered, and the indicator light is off when there is no cursor. However, in actual production, when the above-mentioned adjustment method is adopted, it is often encountered that the detection electric eye does not find the cursor and keeps alarming, resulting in downtime and causing a lot of waste. The correct adjustment method is: you must first observe the reaction state of the detection electric eye when the machine is running, and then make corresponding adjustments, so as to ensure that the reaction of the detection electric eye is sensitive and accurate, and cannot refer to the reaction state of the detection electric eye in the clear state.
② Treatment of laser anodized aluminum plate seams: scanning in holographic positioning and hot stamping, since most of the holographic anti-counterfeiting patterns on the anodized aluminum are arranged independently and intermittently, a seam will appear every some distance in the running anodized aluminum (Panel seam), if the normal stepping of holographic positioning and hot stamping of anodized aluminum is not well controlled at this time, the seam will not be avoided, resulting in hot stamping waste. Therefore, it is also an important factor for the success of holographic positioning and hot stamping to control the seam skipping procedure of holographic positioning and hot stamping of anodized aluminum.
3. Other matters needing attention:
① During the hot stamping process, sometimes the printed matter cannot be hot stamped due to UV glazing. This is caused by the incompatibility between the anodized aluminum and the UV varnish. At this time, it is necessary to adopt the method of hot stamping and then UV glazing.
②If the printed matter to be hot needs to be processed by laser embossing transfer, then the method of first hot stamping and then laser embossing transfer cannot be used, and the laser embossing transfer must be performed first and then hot stamping. There are two main reasons: one is that the surface of the printed matter after hot stamping is often uneven, and the paper is deformed, which will seriously affect the effect of laser embossing transfer; the other is scattered anodized aluminum scraps, paper scraps, dust, and the previous process machine The oil stains on the belt will not only affect the transfer effect of the laser imprint, but may also damage the glazing plate used for the laser imprint transfer.
4. Holographic positioning hot stamping technology, also known as holographic marking hot stamping technology or dedicated hologram positioning hot stamping technology, is a new type of laser anti-counterfeiting technology, which has been widely used at home and abroad. Mainly used for anti-counterfeiting of various tickets, credit cards, passports, banknotes, trademarks, tobacco and alcohol packaging and important publications. According to the characteristics of holographic hot stamping logo, holographic hot stamping is divided into continuous pattern hot stamping and independent trademark hot stamping.
①Continuous holographic logo hot stamping; ②Independent pattern holographic logo hot stamping;
Material selection for bronzing version
High-quality bronzing version is the primary factor to ensure the quality of bronzing. Bronzing plate materials are commonly used copper plates. The material of the copper plates is fine and smooth, and the surface finish and heat transfer effect are good. The use of high-quality copper plates can improve the gloss of the bronzing graphics and the definition of the outline. The plates currently used for bronzing are stainless steel, brass, copper, magnesium and zinc. Which type of plate material to choose should be considered comprehensively according to the order quantity and production efficiency of the product.
1. Selection of plates
①There are generally two kinds of plates for hot stamping, namely copper plate and zinc plate. Among them, copper plate is divided into brass plate and red copper plate.
②The brass plate is suitable for hot stamping large quantities of harder objects, has a certain degree of heat resistance and heat transfer, and is firm, durable and not easily deformed. If the hardcover book cover with cardboard is hot-stamped, a brass plate can be hot-stamped more than 200,000 pieces.
③The copper plate is a darker and slightly red plate. The red copper plate has good heat transfer, heat resistance, firmness, durability, and resistance to deformation. Red copper is a neutral metal and has a certain degree of flexibility. The writing and patterns produced by this hot stamping plate are soft and plump, which is different from other plates.
④Zinc plate is another kind of metal plate. Its texture is softer than copper plate, and its durability and heat resistance are worse than copper plate. Zinc plate is suitable for hot stamping of general paper and cardboard products in small batches (such as several thousand pieces). If the hot material is hard or the number of hot stamping is large (such as more than 10,000 pieces), the imprints on the hot stamping plate It will gradually become blurred and damaged, and the hot stamping traces of the hot items will not be clear, and even defective products and waste products will be caused.
⑤From the price point of view, the zinc plate is slightly cheaper than the copper plate. However, considering the durability, the copper plate is more affordable. The printing endurance of a copper plate is dozens of times that of a zinc plate. Therefore, when selecting hot stamping plates, various factors must be considered in order to ensure quality and save costs.
2. The thickness of the hot stamping plate
The thickness of the hot stamping plate should be selected according to the texture of the hot stamped object and the size of the hot stamping area. Now the thickness of the hot stamping plate is relatively thin, generally about 1.5mm, which can be used for hot stamping general plain paper, etc. If you want to hot stamp the following items, the thickness of the hot stamping plate will be increased.
1) The surface of the ironed object is velvet, satin and hemp textiles. The velvet in the textiles, especially the thick velvet, has very high piles on the surface (about 3mm); while the satin and hemp textiles are thick and have great elasticity. If the hot stamping plate is too thin, the thickness can reach If the requirements are not met, problems such as paste and dirty plates after ironing will occur, causing undue losses. When hot stamping such materials, the thickness of the hot stamping plate should be thickened to about 3.5mm before it can be used.
2) The surface of the ironed object is uneven or has protruding patterns. Some hot objects, such as lacquer coating, PVC coated paper, special pattern paper, etc., some of these materials have plain patterns on the surface, and some have protruding patterns of various shades, and the hot stamping plate needs to be enlarged when hot stamping The pressure on the object being scalded. When hot stamping such items, the thickness of the hot stamping plate is generally increased to 2.5mm.
3) Hot stamping leather, recycled leather and synthetic leather items. This kind of scalded objects are generally expensive and flexible. Especially leather (usually sheepskin), the skin is thick, a sheepskin costs one or two hundred yuan, if the hot stamping plate is too thin, it will cause a lot of losses. When hot-stamping such items, the thickness of the hot-stamping plate should also be about 2.5mm.
4) Images with larger hot stamping area. Some items need to be hot stamped with a large area. The hot stamping pressure required is relatively high. The thin hot stamping plate cannot withstand greater pressure, and even if it can barely withstand greater pressure, dirty plates are prone to appear. Phenomenon, the ideal hot stamping effect cannot be achieved. When performing large-area hot stamping, a hot stamping plate with a thickness of about 2.5mm should also be used.
Mastering of bronzing pressure, temperature and time
In addition to the proper selection and handling of hot stamping plates and reasonable selection of hot stamping materials in hot stamping processing, the control of pressure, temperature and time during hot stamping is also very critical. Correctly and flexibly mastering these three points in actual operation is an important condition for doing a good job of hot stamping.
1. Master the stamping pressure
①The size of the hot stamping pressure should be determined according to the nature, thickness, hot stamping form, and the size of the hot stamped area. The hot stamping pressure should be so high that the stamping after ironing is clear, sharp, bright and not sticky; the stamping pressure should be low, so that the stamping pressure should be firm, not falling off, no pattern, clear print, and sharp edges and corners. . If you want to hot stamp more than two kinds of pictures and texts with large differences in area size on the same plate at the same time, you must master the pressure per unit area and the force of the hot object. The larger the hot stamping area. The pressure should be higher, and vice versa.
②The hot stamping pressure of the automatic hot stamping machine can be adjusted automatically according to the required pressure of the hot object. It is more convenient to adjust, but it will be restricted by factors such as uneven thickness of the hot object. Once the thickness of the ironed object is uneven, the phenomenon of paste or pattern will appear.
③Hot stamping with a manual hot stamping machine mainly needs to grasp the pressure after the hot stamping plate contacts the hot object. The pressure should be increased during indentation, which is very necessary in operation. Although manual hot stamping is cumbersome, the pressure can be adjusted freely according to needs, and it is not affected by factors such as the thickness of the object to be ironed, and it can be used for hot stamping items that are difficult to process.
2. Mastering the hot stamping temperature and stamping time
The hot stamping temperature and hot stamping time should be determined according to the hot stamping material and the hot stamping form. In the actual hot stamping, if the hot stamping temperature is too high and the hot stamping time is too long, there will be staleness, unclear graphics, and dullness; otherwise, it will not be hot, fall off after hot, and patterned. Phenomenon. The hot stamping time and hot stamping temperature can be fine-tuned each other during work. For example, when the temperature of the hot stamping plate is slightly higher, the hot stamping time can be slightly shortened; when the hot stamping temperature is slightly lower, the hot stamping time can be adjusted appropriately Lengthen it. The adjustment range of the two should not be too large and should be controlled within a certain range. As long as the adjustment is appropriate, a good hot stamping effect can also be obtained. If embossing is to be performed while hot stamping, the hot stamping temperature can be appropriately reduced by 10-20°C, and the hot stamping time can be increased by 1 second, which can increase the fastness of the print.
For bronzing, the most important auxiliary material is bronzing paper font, which is what we call anodized aluminum. The types of anodized aluminum are roughly divided into ordinary and laser, and laser is divided into plain surface and patterned version. The performance of various models of anodized aluminum is not the same, some of the same model but different batches, its comprehensive performance will also be changed.
Laser anodized aluminum: The film material is PET ticket printing, and the film thickness is 14-18μ. The laser anodized aluminum is beautiful, bright, and colorful. The applicable temperature is between 110°C and 150°C. There is also a laser holographic positioning hot-dip aluminum online publication, which is mainly used for cigarette labels, wine boxes, cosmetic packaging, etc. It is the most popular anti-counterfeiting method in the hot-stamping industry, and the applicable temperature is between 110°C and 150°C.
Ordinary anodized aluminum. The material is more PEF film, the thickness is 12-14μ, there are gold, red, copper, blue, black and other colors, and the applicable temperature is between 90℃-120℃.
Anodized aluminum usually uses PET film as the base; the bottom layer is a stripper and color coating, the middle is a vacuum spray electrolytic aluminum powder layer, and the surface layer is an adhesive (hot sol). As shown in the figure:
3. When choosing, choose according to the size of the bronzing pattern. The following points should be paid attention to when choosing:
1) Adhesion performance (ie bronzing adhesion).
3) The ability to withstand hot stamping patterns.
4) Adaptability to ink.
4. Identification of the tightness of anodized aluminum primer
Simple method: stick with transparent adhesive paper, or rub it with your hands. If the color layer is easy to fall off, it means that the adhesive layer is loose and easy to hot stamp, and it is suitable for ironing large areas. Otherwise, it is suitable for ironing small text and lines. But it is not absolute gravure, it is more reliable to choose after trial. The hot stamping suitability of anodized aluminum includes surface finish, brightness, clarity, hot stamping suitability for graphics and small text, surface fly gold and burrs and other inks. It should be based on different printing materials, packaging product levels, and electrochemical The price of aluminum and the suitability of hot stamping are weighed.
5. High-quality anodized aluminum should meet the following points:
1) The color layer is evenly painted, and there is no visible color after ironing.
2) Good color and no black spots.
3) The viscose coating is uniform, smooth and without obvious streaks. The second important material for bronzing is the bronzing plate, which is generally made of aluminum-zinc-magnesium-copper alloy, brass and other materials. The pattern surface of the bronzing plate and the non-embossed surface have a depth of 1-1.5mm, and the inclination angle is between 15 degrees and 30 degrees.
6. The layout must be smooth, and tiny spots and scratches will be reflected on the printed product after hot stamping.
The formation process of the bronzing process: when the hot stamping is heated, the adhesive changes into a liquid state, and the electrochemical aluminum is imprinted on the printed matter with an electroplate, and then the tape base is separated from the aluminum layer and the color layer to complete the bronzing, as shown in the figure:
7. Hot stamping paper performance
① The hot stamping performance of anodized aluminum depends on the isolation layer and the adhesive layer.
②The looser the isolation layer, the easier it is to separate and attach to the printed product.
③The thicker the adhesive layer is, the easier it is to bond with printed products.
④The hue of anodized aluminum depends on the dyeing layer
8. Appearance quality of bronzing paper
①There are no obvious scratches and flaws on the front of the anodized aluminum (the side showing the color).
②The hue of the same model of anodized aluminum is basically the same and there is no difference.
③The adhesive layer is evenly coated without obvious streaks.
9. Hot stamping requirements for hot stamping paper
① Firm adhesion: The adhesive layer on the surface of the electrochemical aluminum foil can be firmly adhered to a variety of hot stamping materials with different characteristics, and should not fall off or contiguous under certain temperature conditions; for special hot stamping materials, electrochemical The aluminum foil adhesive layer should use special adhesive materials to meet special needs; the adhesion firmness is also related to the hot stamping time, hot stamping temperature, and hot stamping pressure. Adjusting the hot stamping process can also improve the firmness of the hot stamping of the electrochemical aluminum foil. degree.
②Foil film performance is stable: the chemical properties of the dyed layer of the electrochemical aluminum foil should be stable. It will not change color when hot stamping, laminating, and glazing, and the surface film will not be damaged. After stamping into graphics, it should have a long-term durability Heat resistance, light resistance, humidity resistance, corrosion resistance and other properties.
③The separation layer is easy to separate: the separation layer should be adhered to the base layer, but also easy to separate; the electrochemical aluminum foil product must not be separated from the base during the production, transportation, and storage; when it encounters a certain temperature and pressure, it will be separated from the base immediately , The heated and pressurized parts should be separated thoroughly, so that the aluminum layer and the dyed layer can be transferred to the surface of the hot stamping material smoothly to form a clear picture and text. The part that is not heated and pressed is still adhered to the base layer and cannot be transferred. The transfer part and the non-transfer part should be clearly demarcated and neat.
④Pictures and texts are clear and clean: in the allowable working temperature range of hot stamping, the electrochemical aluminum foil does not change color, and the pictures and texts of the size of “Four size” are clear and clean when hot stamping, and the lines and strokes are not connected or less connected. The dyeing layer of the anodized aluminum foil should be evenly coated, and the aluminized layer has no blisters, no creases, and no obvious streaks; clear imprinting is an important performance of the anodized aluminum foil. The hot-stamped handwriting should be free of burrs, which is related to the adhesion between the separating layer and the adhesive layer and whether the coating is even.