Dry offset printing and offset printing of the hot

Dry offset and offset printing of material printing

dry relief offset

when printing in color, the ink layer thickness is only 2 ~ 3 m. if the ink is directly transferred from the printing plate to the plastic surface, it is difficult to be uniform, so dry offset printing is adopted. Dry offset printing is a printing method that combines embossing and offset printing. It is transferred from relief to blanket and then to the surface of the substrate. Because letterpress does not need water, the name of dry offset printing comes from this. Its advantage is that the ink transferred from the printing plate to the blanket can be transferred to the plastic surface evenly, no matter how concave and convex the printed plastic is, due to the elasticity of the rubber

the difference between dry offset printing and offset printing is that the offset printing plate is flat, which uses photosensitive materials to make lipophilic graphics and texts, and the remaining blank parts are hydrophilic, and then uses the principle of oil-water repulsion to make the ink stick only to the graphics and texts of the printing plate; The dry offset printing plate is a relief plate, with the blank ending 520 falling by 1.33%, and the part is concave. Without the use of fountain solution, the ink can only stick to the protruding graphic part

the dry offset printing plate for printing plastic is generally a resin plate with a metal base or a plastic base. After exposure, the resin of the image and text part solidifies, and the uncured blank resin is removed by developing, and finally the protruding image and text are left. During printing, the ink roller soaks the image and text of the relief plate with ink, and then it is transferred to the blanket to form color images and text respectively, and then the ink is transferred to the substrate through the blanket overflow cylinder and pure rolling. Because the printing plate is only in contact with rubber, its printing resistance is quite high, up to 1-2 million prints

there are two drying methods in the printing process: infrared drying and ultraviolet drying

infrared drying is to evaporate and dry the solvent in the solvent based ink, and the remaining binder and pigment adhere to the plastic surface. As the temperature of the printed plastic increases while heating and drying the volatile solvent, it should be noted that the temperature of the drying channel should not exceed the heat-resistant temperature of the plastic and cause plastic deformation

purple meal drying is the polymerization reaction and curing after UV ink printing and UV irradiation at a certain wavelength. The whole ink layer is a cross-linked structure. The ink layer is firm and dense, and its chemical resistance and friction resistance are better than solvent based ink. In recent years, it has been widely used at home and abroad because of its advantages of instant drying, low temperature curing and solvent-free emission

many plastic products are printed in circles. In order to fully irradiate the ultraviolet light, a short tunnel device is installed in the subsequent part of the printing machine, with a conveyor belt inside. While conveying the printed plastic parts forward, it rotates horizontally. The ultraviolet light irradiates all the ink film surfaces and solidifies instantly

plastic products are different from sheet printed materials. Many plastic products need to be repackaged one by one after printing. If inappropriate solvent ink is selected, there is residual solvent after ink film formation, which does not meet the requirements of environmental protection. And choose UV ink instant curing, there is no environmental protection problem; In addition, using UV ink, the printing adaptability is very good. Due to the existence of no solvent, the viscosity change on the ink bucket and inking roller is very small, the stability on the machine is good, the dot will not expand, and the printing image and text are clear; In addition, in the process of UV drying of welded products with the same steel grade, diameter and size, the consumption of building a factory in Suzhou, China in 1994 is only 1/5 of that of infrared drying, and the printing capacity is as high as 18000 ~ 2000 times/hour, which greatly shortens the working cycle and improves the working efficiency

in order to improve the adhesion of ink, the surface of plastic products must be pretreated during printing, especially the non-polar method with low surface tension is fire treatment. The flame contains excited o, no-, oh- and nh+4, which makes the plastic surface form a very thin oxide layer to improve its critical surface tension. The treatment is very good, generally up to 48 ~ 60 dynes per cm. Flame treatment is applicable to plastic products of various shapes. For circular plastic products, it can rotate so that each side can be treated. The main variables that affect the effect of flame treatment are air/gas ratio, the distance between the treated surface and the blue top of the visible flame, the speed of plastic products passing through the flame, and so on

this kind of printing machine is generally automatic multicolor machine, with satellite layout, compact structure and high production efficiency. A few years ago, such machines were still dependent on imports, but with the localization in recent years, the prospect of dry offset printing is promising

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