At present, there is no mature UV gravure color ink to be put into the actual production of printing enterprises, generally, UV varnish is printed on the last color group of the rotary gravure production line. This is because rotogravure requires that the viscosity of the ink is low, about 20 seconds (measured with a 4 # cup), and the viscosity of the resin in the current UV color ink linking material will be too large after adding the color material, and cannot be added. Solvent to reduce viscosity. Because UV varnish does not need to add colorants, it can meet the viscosity requirements of rotogravure printing. Compared with the application of UV varnish by ordinary rollers, the application of UV varnish by gravure printing has many special technical problems, so special attention should be paid. (1) Adhesion between substrate and UV varnish If UV varnish is coated on the plastic film, the surface tension of the film must be 40-42mN / m, otherwise the UV varnish will not adhere firmly, and the varnish layer will easily fall off into small pieces under the action of external force. In addition, ensure that the ink is completely dry before glazing. For example, the front end is printed with water-based ink, and the substrate is paper. Although the ink on the surface of the paper seems to be dry, there may still be solvent left inside. If UV light is applied at this time After the UV varnish is cured, the alcohol in the residual solvent will reversely wet the UV varnish layer, causing the UV varnish layer to fall off in the next process. (2) Leveling problem of UV varnish Rotary gravure presses are fast and have poor UV varnish fluidity, which often results in varnish not leveling, so UV varnish layers with low brightness, dots or ripples often appear. The main factors affecting the leveling of UV varnish are the mesh number of the anilox roller, the viscosity and temperature of the UV varnish. (3) UV lamp irradiation generates a lot of heat, which is easy to deform or dehydrate the substrate Due to the high temperature of the UV lamp, the surface temperature of the substrate is high. UV curing generally uses the lampshade water cooling method, but it can only prevent the lamp from being burnt out, and cannot solve the problem of high surface temperature of the substrate. The following methods can be used to reduce the surface temperature of the substrate. ①Use high-efficiency UV lamp. The proportion of ultraviolet light released by imported high-power UV lamps accounts for about 30%, while most domestic UV lamps can only reach 15% to 20%. ②Insulation glass is added between the UV lamp and the substrate. Generally imported quartz glass with a thickness of 3mm can absorb 10% of ultraviolet light. Although the printing speed will be reduced after the installation of thermal insulation glass, it is indispensable for the printing of PVC film with a temperature resistance of 15 μm or less, and it is not necessary to install other materials when printing. ③ Reduce the number of UV lamps and increase the power of each UV lamp. The process of the substrate absorbing heat is from the inside to the inside. This process is slow, so passing through the high temperature area quickly can prevent heat from being transferred into the substrate. According to this principle, the shorter the time the paper passes under the UV lamp, the better. This requires a small number of UV lamps, a small opening width of the lampshade, and increases the power of each lamp. For example, the opening width of the UK Nordson UV lampshade is only 70mm, and the opening width of the Beijing Esterbo UV lampshade is 75mm, but the power of these two UV lamps is very high. At present, UV lamps with a power density of 400W / cm are sold in the US market. (4) Energy-saving problems of UV lamps ①Using high efficiency UV lamp. ② Correctly match the power, printing speed and varnish thickness of the UV lamp. ③Using a power supply with low internal consumption, the internal consumption of the transformer power supply is generally greater than 10%, while the internal consumption of the transformerless power supply (such as the UVC power supply produced by Pantoc, Switzerland) is less than 1%, and because of the quick start and the stepless power adjustment function, and Can save 30% of electricity. ④Use a UV lamp with a small diameter. The ultraviolet light is emitted from the center of the UV lamp tube, and the heat is gradually transferred to the outside through the molecular collision. The central temperature can reach 1700 ℃, but the molecular collision inside the UV lamp consumes a lot of energy and is useless, so a UV lamp with a smaller diameter should be used High-power water-cooled capillary UV lamp with a diameter of only 6mm. At present, many UV lamp tubes cannot be made smaller in diameter, because the diameter of the UV lamp tube becomes smaller, the load on the tube wall will increase, and the tube wall will swell and deform. The longer the tube, the more obvious the deformation. Therefore, it is recommended that enterprises use short and thin-diameter lamps after docking. ⑤ Reduce the UV light path. The UV path length is the product of the distance that the UV lamp radiates light to the surface of the substrate and the refractive index. To reduce the UV light path, the reflector should be as small as possible, and the distance between the UV lamp and the surface of the substrate should be as short as possible. The measurement results show that the ultraviolet light attenuation is proportional to the square of the UV light path, the UV light path increases by 10mm, and the ultraviolet light energy decreases by about 5%. Whitening Toothpaste,Dental Teeth Whitening Toothpaste,Natural Whitening Dental Paste,Whitening Deep Cleansing Toothpaste Huai 'an Bst Trade Co., LTD , https://www.bstoral.com