What Is Hot Stamping Process?
The hot stamping process is to use the principle of hot pressing transfer to transfer the aluminum layer in the anodized aluminum to the surface of the substrate to form a special metal effect. In terms of specifications, hot stamping refers to the hot stamping of the anodized aluminum foil ( Hot stamping paper) hot stamping process to the surface of the substrate, because the main material used for hot stamping is anodized aluminum foil, so hot stamping is also called anodized aluminum hot stamping.
Hot stamping on UV varnish
UV varnish can improve the gloss of printed products, and its unique high-gloss effect is recognized by customers. Although hot stamping on UV varnish can obtain very good visual effects, the process is difficult to control. This is mainly because Since the hot stamping suitability of UV varnish is not yet mature enough, the resin components and additives of UV varnish are not conducive to hot stamping.
However, when processing certain products, the process of hot stamping on UV varnish cannot be avoided. The original production process needs to go through three processes of offset printing, hot stamping and varnishing. After changing to new materials, offset printing and varnishing can be done once and then hot stamping, so that one process can be reduced and one UV curing can be reduced. The influence of paper die-cutting can avoid the phenomenon of bursting color, which greatly improves the production efficiency and reduces the scrap rate. But at this time, it is necessary to hot stamp on UV varnish, which puts forward quite high requirements for UV varnish and hot stamping anodized aluminum, and the following aspects should be paid attention to.
1) Pay attention to controlling the amount of varnish when glazing. UV varnish must have a certain thickness to achieve the effect of high brightness, but too thick varnish layer is not good for hot stamping. Generally, when the UV varnish layer is coated by offset printing, the amount of glazing is about 9g/m2. After reaching this value, if you need to increase the brightness of the UV varnish, you can adjust the coating process parameters (coating roller screen angle and screen line angle) number, etc.) and printing equipment performance (printing pressure and printing speed, etc.) to improve the flatness and glossy effect of the varnish layer.
2) Try to ensure that the varnish coating of the whole batch of products is relatively stable, and the varnish layer should be thin and flat.
3) Reasonable selection of hot stamping materials. It is required that the hot stamping material is resistant to high temperature and has good adhesion, and its adhesive layer must have good affinity with the resin of UV varnish.
4) Accurately adjust the temperature and pressure of the hot stamping plate, because excessive pressure and temperature will destroy the performance of the ink and make hot stamping more difficult.
5) The hot stamping speed should not be too fast.
Hot first and then printed
The process of hot stamping first and then printing is generally to enhance the metallic visual sense of the pattern after printing, and adopts a process method of hot stamping first, and then four-color printing on the hot stamping pattern. Usually, gradient and metallic color patterns can be overprinted with dots, which has good visual performance. The process needs to pay attention to the following matters in actual operation:
1) The requirements for hot stamping anodized aluminum are very high. At the same time, the hot stamping position is required to be very accurate. The surface of the hot stamping pattern is smooth and bright, without blistering, no paste, no obvious scratches and scratches, etc., and the edge of the hot stamping pattern cannot There are obvious indentations;
2) For white cards and glass cards, special attention should be paid to the protection of semi-finished products, and the influence of various unfavorable factors such as paper deformation should be minimized during the production process, which is conducive to the smooth progress of the hot stamping process and the improvement of the product qualification rate a great help;
3) The adhesive layer of anodized aluminum should have extremely high adhesion (if necessary, a special adhesive layer should be developed for cigarette pack products), and the surface tension of anodized aluminum should not be lower than 38mN/m;
4) Before hot stamping, the positioning film must be output first, and the accuracy of hot stamping and printing overprinting can be ensured by adjusting the exact position of the hot stamping plate;
5) Before mass production, the film-drawing test must be carried out on the products that are hot-stamped and then printed. The method is to use a 1-inch scotch tape to directly pull back the hot-stamped anodized aluminum, and observe whether there is gold powder falling off, incomplete or hot-stamped. phenomenon, which prevents a large amount of waste during the printing process;
6) When making film, pay attention to the range of unilateral contraction and expansion, which should usually be kept within 0.5mm.
Holographic positioning hot stamping
Holographic positioning hot stamping can be applied to printed products with anti-counterfeiting patterns, which greatly improves the anti-counterfeiting ability of products and at the same time improves the grade of products. Holographic positioning hot stamping has very high requirements on temperature, pressure and speed control, and the hot stamping model also has a great influence on its effect. In holographic positioning hot stamping, the accuracy of overprinting is directly related to the quality of the product, and the production of hot stamping film should be expanded by 0.5mm on one side. Usually holographic positioning hot stamping adopts hollow hot stamping. In addition, the cursor of the holographic positioning hot stamping material should be uniform, and the steps between the patterns should be uniform, so that the machine can track the hot stamping cursor accurately.
