In plastic gravure printing, how to control the ink printing viscosity is a very critical issue. Especially in high-speed rotogravure printing, whether the ink printing viscosity is properly controlled is directly related to most quality problems such as pigment transfer, dirty plate, gloss and brightness of the printed product, pigment adhesion fastness, and static electricity, which affects printing. Product yield and work efficiency. Factors affecting ink viscosity The factors that affect the viscosity include the influence of the diameter, hardness and elastic modulus of the elastic roller, the nature of the roller, the speed of the roller, the temperature of the roller, the ambient temperature and humidity, the temperature of the sample, the thickness of the ink film, the ink, or the binder on the elastic roller , The condition of the elastic roller during the cleaning process, the nature of the test sample, etc. The factors that affect viscosity are that viscosity is closely related to its temperature, concentration of component particles, particle size, etc., and has little relationship with humidity and air pressure. The measurement accuracy and measurement units of different measurement methods are different and cannot be converted to each other. From the above four points, we can see that there is a big difference between ink printing viscosity and viscosity, but the two are still related. The main performance is that the viscosity is a physical quantity that measures the viscosity of the fluid. The dynamic viscosity of the fluid is determined by the inherent physical properties of the fluid. Its value is a direct measure of the viscosity of the fluid. It is also the resistance of the fluid to shear deformation in motion. A measure of ability. Under the same environmental conditions, a large viscosity means a high viscosity and vice versa. How to control ink printing viscosity in high-speed rotogravure printing The ink consists of organic solvents, binders, pigments, additives, additives, etc. When these raw materials have been determined, the processing degree, method and composition of each component have been determined, the quality of the pigment transfer is mainly related to the printing viscosity of the ink. Practice has proved that the ink printing viscosity has a certain range (11 ~ 24S, using Zahn viscosity cup No. 3), the greater the ink printing viscosity, the worse the pigment transfer effect. Because the role of the solvent is to dissolve the resin or additives and additives, etc., to give it fluidity, so that the pigment is easy to disperse. When the printing viscosity of the ink is too high, the entire ink system is in a state of supersaturation, and the fluidity of the pigment and other substances is poor. They cannot be evenly dispersed, but appear in clusters, which are easy to pile up together, so that the pigment cannot smoothly enter and exit the mesh. When the ink printing viscosity is too high, the pigment cannot even enter the mesh, let alone transfer. This is the so-called blocking phenomenon. Therefore, as long as the colloid system composed of resin, pigment and organic solvent is not in a state of supersaturation, but a saturated or unsaturated state, the pigment and other substances can be well dispersed in it to form a uniform and delicate colloid system In this way, the pigment can enter and exit the mesh smoothly, and the problem can be solved. Some ink manufacturers recommend that the ink printing viscosity be between 15 and 18S (Zahn Viscosity Cup No. 3). However, in practice, especially in high-speed gravure printing machines (printing speed is 100 ~ 260m / min), in order to ensure a good transfer effect, and can print for a long time, improve efficiency, ink printing viscosity is generally 11 ~ 15S ( Zahn Viscosity Cup No. 3) to find its ideal point. In plastic gravure printing, dirty plate problems often occur. The phenomenon is that the non-printing surface of the cylinder will also be stained with a hazy layer of resin (resin entrapped in the resin), and transferred to the substrate to make the substrate appear to be sheet-like stains or linear stains. In addition to the hardness of the doctor blade, the doctor blade pressure, the contact angle of the doctor blade, and the quality of the plate cylinder, the root cause of the dirty plate phenomenon is mainly related to the printing viscosity of the ink. As mentioned above, when the printing viscosity is too high, resin pigments and other substances have poor fluidity and are not evenly dispersed. They are easy to pile up together. Under the relatively high-speed movement of the blade and the plate cylinder, the blade and the plate cylinder are easily damaged, which is easy Linear stains occur. At the same time, because the resin is also in a supersaturated state, a large amount of resin coalesces together, and the affinity of the resin for the roller, under the pressure of the blade, the resin will stick tightly to the roller (the resin is entrained with pigment), In this way, sheet-like dirt appears. Generally speaking, if the printing viscosity of ink is small, the dirty version will not happen easily. However, if the printing viscosity of the ink is too low, it means that the organic solvent content in the ink is large, and the resin, pigment and other components are relatively small, so that it cannot form a smooth film layer when dried, and the printed product will be white and become dull. Light, lack of luster. Therefore, if the printed product needs to have a good gloss, generally consider using a larger ink printing viscosity (13 ~ 19S, Zahn No. 3 cup), that is, the resin and pigment components are relatively more to meet the requirements of the printed product need. At the same time, when the ink is printed on the plastic and dried and becomes an ink film, the wrapped pigment can be firmly attached to the surface of the plastic, and resin is the main material for firmly attaching to the plastic. Therefore, the fastness of pigment adhesion is also related to the printing viscosity of the ink. This shows that the ratio of resin and pigment in the ink can not be too large, nor too small, but should be within the normal range, the pigment adhesion is only strong. Under normal ambient humidity, the printing viscosity of ink is above 16S (Cahn No. 3 Cup), and static phenomenon generally does not occur. The printing viscosity of the ink is below 16S (Zahn Cup No. 3), as the viscosity becomes smaller, static phenomena such as whiskers, streaks, edge repulsion, flying ink, poor transfer, and extremely irregular water stains will follow. It happens and gets worse. In view of the above reasons, people in the industry believe that it is common to find the ideal point of ink printing viscosity between 11 and 17S (Zahn Cup 3). If static phenomenon occurs within this range, in accordance with the principle of mutual consideration, generally do not need to increase the printing viscosity of the ink to eliminate static electricity, but by maintaining normal environmental humidity, changing the structure of the thinner composition, installing anti-static brushes, using static electricity Antistatic agents and other methods to eliminate static electricity. Only in this way can we improve the efficiency and yield rate while guaranteeing the quality, and lay the necessary foundation for the printing enterprises to make profits. Tinted Aluminum Mirror,Tinted Aluminum Mirror Uv,Tinted Aluminum Mirror Tint,Tinted Aluminum Mirror Reflector Dongguan Huahui Glass Manufacturing Co.,Ltd , https://www.antiquemirrorsupplier.com