Hot Stamping, should be called hot aluminum (Foil Stamping), because the most commonly used is gold, silver, so commonly known as hot stamping, hot stamping, hot stamping gold foil and so on.
Hot printing process of the printed matter, we have seen, book covers, real estate albums, business cards, packaging, are very like to use. However, if you have not entered the printing plant, you may not be very clear about the production process of hot stamping.
Hot stamping process is the use of the principle of hot pressing transfer, the aluminum layer in electrochemical aluminum transfer to the substrate surface to form a special metal effect, can be divided into cold stamping and hot stamping, hot stamping and there are points: ordinary flat stamping, three-dimensional stamping (commonly known as relief and embossed stamping), holographic positioning hot stamping and other processes.
Plain hot stamping
1. Printing plate (commonly known as "on the plate") production process
The quality of hot stamping plate is an important factor affecting the quality of hot stamping. The production of ordinary flat hot plate mainly uses photographic etching plate making process and electronic engraving plate making process, the former production process is simple, low cost, but the produced hot plate precision is also relatively low, limited to hot printing text, bold lines and patterns with low quality requirements; The latter produced a high precision stamping plate, can be rich and delicate performance of image level equipment operation, fine lines and uneven thickness of the graphic can be well reproduced, the cost is relatively high, the scope of application is relatively wide, the hot stamping effect requirements of higher cigarette bags, wine bags, medicine bags, cosmetics packaging are applicable.
2. Material selection of printing plate
The plate material commonly used for ordinary flat ironing plate is copper plate or zinc plate. The copper plate has fine texture, smooth surface, good thermal conductivity, wear resistance and pressure resistance, and is not easy to deformation, which is favored by most plate manufacturers. For a small number of print manufacturers, quality requirements are not high, hot plate plate material can be used zinc plate.
3. Material selection of the base version (commonly known as the "next version")
At present, most ordinary flat hot plate plate making factory only make hot plate, and because of the different hot printing media, plate making factory can not provide suitable matching plate, so most carton packaging companies are facing the problem of choosing what material ordinary flat hot plate. Comprehensive hot stamping media, printing resistance, adaptability, convenient operation and other factors are excessive packaging. Summary: For coated paper printed matter, ordinary flat hot printing can use waste PS plate, steel scraper blade, thick about 0.5mm solid texture of kraft paper as the base plate; For gold card paper, silver card paper, laser card paper, glass card paper, can use 0.8 ~ 1.5mm thick insulation board, steel ink scraper blade as the base plate; No matter what kind of material is used for the base plate, the pressure paper under the pad is indispensable.
4. Process requirements
Electrolyzed aluminum
Ordinary electrochemical aluminum is composed of 4 ~ 5 layers of different materials, including the base film layer, peel layer, coloring layer, aluminum plating layer, adhesive layer. Hot printing speed and quality are mainly affected by the stripping layer and adhesive layer packaging decoration, if the two coatings are not sensitive enough to heat, the hot printing speed will be reduced accordingly.
Temperature, pressure, speed
This is the three elements of the hot stamping process, only by controlling the relationship between the three, in order to control the quality of hot stamping. The temperature of ordinary flat hot stamping is generally 70 ~ 110℃, the temperature is too low, the adhesive layer and peel layer of electrolytic aluminum can not be fully melted, and the electrolytic aluminum can not be completely transferred during hot stamping, resulting in hot stamping. The temperature is too high, the paper deformation is serious, easy to produce overprinting is not allowed, graphic paste, writing flowers, electrochemical aluminum discoloration and other problems. Hot stamping pressure should be adjusted to appropriate according to the bearing capacity of the hot stamping medium and the upper and lower plates. Hot stamping speed: manual hot stamping gold is generally controlled at 600 ~ 700 sheets/hour; Automatic hot stamping machine is generally controlled at 3500 ~ 5000 sheets/hour.
Three-dimensional pressing
It can complete hot stamping and embossing at the same time, reduce the processing process and the amount of waste generated due to overprinting, improve production efficiency and product quality, mainly used in cigarette bags, wine bags, medicine bags, cosmetics packaging and other high-grade paper box packaging hot stamping.
1. Definition (also known as embossing, three-dimensional embossing, embossing)
Three-dimensional hot printing means that the graphic and text processed by hot printing has an obvious high three-dimensional level, which is abrupt on the surface of the print. Three-dimensional hot stamping technology is a combination of hot stamping technology and embossing technology of a composite technology, can also be seen as "hot stamping + embossing" combination process, is the use of corrosion or engraving technology to hot stamping and embossing of the graphic into a matching up and down of the negative mold intaglio and positive mold relief, to achieve hot stamping and embossing technology to complete the process.
2. Principles
Three-dimensional hot printing is hot printing and embossing once completed: the use of hot plate, bottom die, under a certain pressure and temperature, so that the print substrate plastic deformation, while the electrochemical aluminum foil printed on the print or other substrate plastic deformation of the part, so that the surface of the print art processing. Electric carving three-dimensional stamping plate with high precision, stamping effect is very exquisite. Electroengraving brass plate is widely used in post-press processing, through the control of computer software, three-dimensional engraving of the pre-scanned image, so that the hot plate with the prefabricated relief plate, can be three-dimensional hot printing. The key to the process is plate making, the graphic part of the hot plate should be rounded lines, which are different from the right Angle lines of the ordinary flat hot plate, so the three-dimensional hot plate needs to be processed twice after corrosion, and the technology is more difficult.
3. Embossing printing plate (commonly known as "upper version, negative version") production
The production principle of the embossing plate is more complex than that of the ordinary flat embossing plate, and because it also needs to achieve the embossing effect, the embossing plate has a depth change, and the embossing depth of the image is also deeper than the ordinary flat embossing plate, and the precision is higher. At present, the domestic plate making factory adopts the computer engraving brass plate making process typesetting, and the embossing and stamping plates produced are rich in level, fine and high in printing resistance.
4. The production of embossing underplate (commonly known as "next edition, Yang edition")
The base plate used for embossed stamping must be the positive die relief plate corresponding to the embossed stamping plate. At present, the base plate material usually selected by the plate-making factory is glass fiber, which can be pre-made according to the model of embossed stamping plate, and the positioning hole layout design is made with the processed copper plate to facilitate replacement and positioning.
The base plate must be precisely corresponding to the embossing plate, but in the embossing process, with the gradual increase in temperature, the embossing plate will expand, while the temperature of the base plate remains unchanged, which will cause the embossing plate and the base plate do not match, resulting in the bottom die being crushed or the embossing pattern is incomplete. Therefore, when making the base plate, the expansion rate of the embossing plate should be fully considered to ensure that a more accurate base plate is produced.
5. Process requirements for embossing and stamping
Electrolyzed aluminum
Special electrolytic aluminum for embossing should be selected, and ordinary electrolytic aluminum should not be used.
Temperature, pressure, speed
Embossing and embossing publishing should be completed at one time, so the embossing temperature is very high, usually in 110 ~ 140℃ to complete, but the temperature is too high in addition to causing paste plate, anodized aluminum discoloration and other problems, will also make gravo embossing plate expansion too much, can not be accurately matched with the base plate, there is bad embossing phenomenon. It can be said that the stamping temperature is the primary factor that determines the success or failure of stamping.
Holographic positioning hot stamping
Step 1 Define
The bronzing anodized aluminum is a holographic image, and the image needs to be accurately positioned on the printing product. There are two kinds of holographic hot stamping: ordinary hot stamping and positioning hot stamping.
Holographic positioning hot stamping is the integration of laser holographic image anti-counterfeiting technology with good anti-counterfeiting effect and hot stamping decoration technology, so that the product increases the anti-counterfeiting performance while improving the decoration. Laser hologram is based on the principle of laser interference, using the method of spatial frequency coding. Laser hologram has been widely used at home and abroad because of its vivid color, obvious level, vivid image, changeable optical transformation effect, high information and technology content. It is mainly used for anti-counterfeiting of various tickets, credit cards, passports, banknotes, trademarks, tobacco and alcohol packaging and important publications.
2. Principles
The hot melt adhesive layer and separation layer on the hot stamping material are heated and melted through the hot stamping die head on the hot stamping equipment. Under a certain pressure, the holographic grating fringe of the information layer of the hot stamping material is separated from the PET substrate, so that the aluminum foil information layer and the hot stamping surface are bonded and integrated to achieve a perfect combination.
3. Production of holographic positioning hot stamping plate
The manufacturing process of holographic positioning stamping plate is basically the same as that of ordinary flat stamping plate and embossing stamping plate.
4. Process requirements of hot stamping
Holographic positioning hot stamping must use a special laser electrochemical aluminum and advanced register detection system, which determines that the requirements of holographic positioning hot stamping materials and the performance of the hot stamping machine are stricter and higher than other hot stamping methods.
Adjust the alignment detection eye
In holographic positioning hot stamping, detecting the adjustment of the electric eye (sensor) is the most important step. The most 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 the cursor is not. However, in actual production, when the above adjustment method is used, it often encounters the problem of continuous alarm because the detection eye does not find the cursor, leading to shutdown and causing a lot of waste. The correct adjustment method is: we must first observe the reaction state of the detection eye when the machine is running, and then make the corresponding adjustment, so as to ensure that the response of the detection eye is sensitive and accurate, and cannot refer to the reaction state of the detection eye in the clear state.
Laser electrochemical aluminum plate seam treatment
Scanning in the holographic positioning hot stamping, because the vast majority of the holographic anti-counterfeiting patterns on the electrochemical aluminum are independently discontinuous arrangement, there will be a seam (plate seam) in the operation of the electrochemical aluminum at every other distance, at this time if the normal step of the holographic positioning hot stamping electrochemical aluminum is not controlled well, it will not be able to open the plate seam, resulting in hot stamping waste. Therefore, the control of the plate seam skip procedure of the holographic positioning hot stamping electrochemical aluminum is also an important factor for the success of the holographic positioning hot stamping.
5. Other considerations
(1) In the process of hot stamping, sometimes you will encounter the phenomenon that the print has been hot stamping because of UV glazing, which is caused by the incompatibility of electrolytic aluminum and UV varnish. At this time, it is necessary to take the first hot printing after UV glazing method.
(2) If the printed matter to be hot also needs to be processed by laser stamping transfer, then the method of first stamping and laser stamping transfer cannot be used, and the laser stamping transfer must be followed by hot stamping.
There are two main reasons: first, 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 stamping transfer; The second is the scattered electrolytic aluminum debris, paper scraps, dust, and oil stains on the machine before the process, which not only affect the laser impression transfer effect, but also may damage the glazing plate used for the laser impression transfer.