In recent years, the laser pattern imprint transfer technology has been widely used in the packaging and printing industry. It uses natural light to achieve a colorful and colorful effect. This effect is looming and gives a novel aesthetic. It is a laser pattern coating and anodized aluminum. The new technology, which is incomparable to India, achieves anti-counterfeiting and environmental protection effects at the same time, which in turn improves the packaging level of the product. At present, this technology is mainly used in cigarette labels. Wine labels. Medicine standard and high-end books and other packaging products.
1 The principle of laser pattern imprinting transfer technology
The principle of laser pattern embossing transfer technology is: apply UV varnish on the surface of the printed matter, combine with the pre-made laser pattern transfer film through the pressure of the laser pattern embossing transfer machine, and transfer the laser pattern after UV varnish curing and setting The film is peeled off from the product. In this way, the application of UV varnish on the surface of the product facilitates the formation of a glittering and bright pattern corresponding to the laser pattern transfer film.
The laser pattern transfer film is covered with regular patterns, which are composed of countless tiny prism-like mesh holes. When the printed product coated with UV varnish is combined with the laser pattern transfer film, the UV varnish is not dried. By the pressure of the laser pattern imprinting transfer machine, the shape of the mesh on the laser pattern transfer film is transferred to the printed matter coated with UV Varnished place. The UV varnish happens to be transparent. It can be said that countless prisms are formed on the printed matter where the UV varnish is applied. By the instant UV drying, the transfer film and the printed matter are quickly peeled off. When we looked at the printed matter, we saw a colorful laser pattern effect in the place coated with UV varnish.
2 Materials and equipment related to laser pattern imprint transfer technology
The materials and equipment related to the laser pattern imprint transfer technology are: UV varnish. Laser pattern transfer film and laser pattern imprint transfer machine, etc. The author will give a brief introduction below to help you further understand the technology.
1) The UV varnish used in the UV varnish laser pattern imprint transfer technology consists of oligomers. Active thinner. The photoinitiator and other additives are composed of UV light. The photoinitiator in the ink absorbs the energy of ultraviolet light, generates free radicals after being excited, and initiates a polymerization reaction to solidify and form a film. The reason why the laser pattern imprinting transfer technology chooses UV varnish as the material is mainly because UV varnish has the advantage of instant drying.
The UV varnish used in the laser pattern printing transfer technology should have the following characteristics:
â‘ Viscosity is slightly higher, of course, this is closely related to the anilox roller of the coating part of the laser pattern imprinting and transfer machine. The anilox roller has a high mesh number, its ink load is low, and the anilox roller has a low mesh number. Its ink load is high;
â‘¡ In order to better achieve the color separation effect of the prism, the UV varnish must have a sufficiently high purity, so the dilute solvent must use anhydrous alcohol;
â‘¢The drying property of UV varnish must be good. This is the basic reason for choosing UV varnish instead of water-based varnish and alcohol varnish. Imprint transfer technology uses the instant drying of UV varnish to complete the laser pattern transfer film. Successfully peeled off from the printed matter, the laser pattern is cured on the surface of the printed matter. [next]
2) Laser pattern transfer film The base film of the laser pattern transfer film is a BOPP film, and the BOPP film must have a uniform thickness. Imaging transparency is good, so that the imprint effect can be completely transferred. The length and width of the laser pattern transfer film can be customized according to customer requirements, and there is no uniform standard. The laser pattern transfer film can be reused multiple times, and the number of uses can be determined according to the characteristics of the product. There is no fixed data. The holes of the laser pattern transfer film are in the shape of a prism. Different arrangement angles can show different shapes, and the depth and size of the holes are different. Most of them have transitions. At present, the pattern of the laser pattern transfer film has a fish scale shape. Slash-shaped. Diamond and various simple patterns and fonts, etc. The production process of the laser pattern transfer film is: using laser technology to engrave the pattern on the lithography plate, and then sticking the lithography plate to the plate roller using double-sided adhesive, and finally transferring the pattern on the printing plate to the BOPP film by pressing and heating. Therefore, the seam of the laser pattern transfer film is inevitable, but it can be minimized infinitely.
3) Laser pattern embossing and transferring machine Laser pattern embossing and transferring machine is a special equipment for laser pattern embossing and transferring process, which is composed of automatic paper feeding unit. UV varnish coating unit. Leveling conveyor unit. The imprinting transfer unit and the automatic paper collection unit are composed of five parts. Paper feeding of automatic paper feeding unit and automatic paper receiving unit with offset printing machine and die cutting machine. The paper collection part is similar, and I will not explain it in detail here.
â‘ UV varnish coating unit
The UV varnish coating unit adopts the flexographic printing method and is composed of anilox rollers. Plate roller. The impression roller and ink lees are composed of four parts. The anilox roller adopts ceramic anilox roller, which is driven by an independent motor, and adopts frequency conversion speed regulation and synchronous control of the main drive. The cylinder pushes the scraper to be pressed and disengaged. The pressure between the anilox roller and the plate roller can pass through the anilox roller Worm adjustment at both ends. There are two forms of printing plates-blanket version and resin version. The blanket version is a special blanket for offset printing, which is suitable for full-page printing. If the product requires leak printing, manual engraving is required. During imprint transfer, UV varnish will accumulate on the leaking edge of the product, affecting the quality of the product; Resin plate is special for flexographic printing, which is completed by film on the flexographic printing plate-making machine. No artificial engraving is needed. It is suitable for full-page printing and leak printing, without hidden quality problems. The plate holder is used to fix the printing plate and adjust the rules in a wide range. The platen roller is equipped with gripper teeth row, the role is to provide pressure and complete the paper transport function.
â‘¡Leveling conveyor unit
The leveling conveyor unit consists of conveyor belts. The conveying rack is composed of a spiral suction pump, and the power is provided by the pressure unit. The vacuum absorption between the conveying belt and the paper makes the paper conveying stable and accurate. The conveyor belt is very long, mainly to increase the leveling performance of the UV varnish on the surface of the product.
â‘¢imprint transfer unit
The film feeding mechanism and the film material recovery mechanism are composed of air expansion rollers. Magnetic powder brake. Guide rollers. Feed roller. Damping roller. Pressure Sensor. Tension controller. It consists of a static eliminator and a film-changing and film-aligning device. The magnetic powder brake is equipped with a slip clutch at the end of the mandrel, which can be separated from or coupled with the end coupling of the inflation shaft. . When the laser pattern transfer film deviates, the actuator is instructed to push the slider through the control button to align the laser pattern transfer film to the correct position to ensure the alignment of the laser pattern transfer film and the printed product. The tension of the laser pattern transfer film is automatically adjusted by the pressure sensor during the operation after the initial controller is adjusted to ensure that it is in the appropriate range from beginning to end. The film feeding mechanism and the film material recovery mechanism are provided with a film material clamping device, which is convenient to fix the film material alignment when the film is connected.
â‘£The imprint transfer mechanism The imprint transfer mechanism consists of an ultraviolet curing mechanism. Finished product stripping mechanism. The roller surface cleaning blade mechanism makes it possible to transfer the pattern on the film material and solidify it on the surface of the printed product where it is coated with varnish. The embossing roller is pressed or lifted by pneumatic control. The hand wheel below can adjust the distance between the embossing roller and the large transfer roller. The pressing force can be controlled by adjusting the pressure of the compressed air.
The UV light curing system consists of two 5.6kW UV light tubes and the matching reflecting device. cooling system. transformer. Capacitor composition. The UV light tube is installed in the reflection device to ensure that its ultraviolet light does not leak out and is reflected uniformly on the required irradiation surface. At the same time, the device is equipped with thermal insulation glass. Because the UV light power is large and the temperature is high, it is equipped with a cooling system to control the temperature in a state where the film is not deformed and is easy to peel. [next]
3 Quality problems of laser pattern imprint transfer technology
The application of laser pattern imprinting transfer technology in production will produce many quality problems. I want to use this opportunity to discuss with you.
1) The sequence relationship between the imprint transfer process and the bronzing bump process If the printed product does not need to be varnished in advance, the imprint transfer can be completed at once; if the printed product requires bronzing and bump, the sequence of the bronzing bump and imprint transfer should be considered.
â‘ Bronzing and bumping processes are used first, followed by embossing transfer process. There are two problems with this. First, the bronzing process is prone to galvanized aluminum burrs. Debris, they are easy to be stuck by the laser pattern transfer film. During repeated use, the anodized aluminum adhered to the transfer film is re-attached to the printed product, which affects the imprint transfer effect, causing the product to be unrecognizable. Second, the bump process is to The picture is raised and raised slightly above the surface of the printed product. When the product is combined with the laser pattern transfer film, the concave and convex portions are likely to damage the integrity of the transfer film mesh and affect the number of times and effect of the transfer film.
â‘¡ First use the imprinting transfer process, and then carry out the bronzing and bumping process. The embossing transfer uses UV varnish to form a smooth protective film on the printing surface. Hot stamping on it is more difficult, and it is easy to cause incomplete bronzing graphics and text, leaving hidden quality problems, so the printing company must contact the anodized aluminum manufacturer Jointly develop anodized aluminum with high adhesion. The above is the analysis of the two situations, both of which have pros and cons. Please print companies to choose carefully according to the actual situation.
2) The dot drop problem of the laser pattern The dot drop problem of the laser pattern is that there is no laser pattern effect on the surface of the UV varnish, just a simple UV varnish coating or no UV varnish coating, and the shape of the prism mesh on the transfer film is not. Transferred to the surface of the printed matter, there is no laser pattern effect. Can be divided into the following situations.
â‘ There is almost no change in the position of the drop point, and its shape is also fixed. This situation is caused by the laser pattern transfer film, and there is no mesh on the film. By adjusting the seam position of the laser pattern transfer film, the position without dots can be adjusted to the blank part of the printed product or not too important. In a conspicuous place, this kind of dropout is caused by the transfer film.
â‘¡ The position of the drop point is not fixed, and the shape change is unpredictable. This phenomenon is also called a discount phenomenon, which is mainly caused by the unstable longitudinal expansion and contraction rate of the base film of the laser pattern transfer film. In addition, it is also related to the film guide roller of the imprint transfer machine. Although the film guide roller only adjusts the film tightness of the transfer film of a large area, if the attraction force received at different positions is different, it will cause the transfer film speed to be different. Therefore, the problem of discounting is caused. Just like the wrinkling of clothes, the transfer film and the printed matter overlap when they are compounded, and are not tiled. Therefore, the prism effect cannot be formed on the UV varnish and there is no laser pattern effect.
â‘¢ The dot drop is caused by the problems of the printing plate and anilox roller of the printing unit. There is a problem with the printing plate or the anilox roller, which results in no UV varnish printed on the product, so the laser pattern cannot be transferred to the product.
3) The rough surface problem is mainly because the viscosity of the UV varnish is too low or the solvent used is not absolute alcohol; there are too many times that the transfer film is used, the mesh holes on the film are incomplete, and the effect of the prism cannot be formed, causing the layout It is not shiny, and it is relatively rough; UV varnish is easy to crystallize at a low temperature. You can use a heater to increase the temperature of the crystal.
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