Ink viscosity is an important factor for the printability of ink. It directly affects the entire printing process and the quality of the final printed matter, and has a decisive influence on the printability of ink. Therefore, it is required that the printing operator must fully understand the ink viscosity and various factors that affect the ink viscosity, and understand the relationship between the ink viscosity and these printing qualities to ensure reasonable control in printing. The influence of ink viscosity on printing effect The viscosity of ink is the main factor that determines the performance of ink. Generally speaking, the lower the viscosity of the ink, the less likely it is to cause dirty printing problems. The lack of gloss. For printed products to have better gloss, it is generally necessary to consider the use of larger ink viscosity 13 ~ 19s (Cahn No. 3 cup), that is, relatively more resin and pigment components to meet the needs of printed products. Under the condition of maintaining normal environmental humidity, the viscosity of the ink is above 16s (Cahn No. 3 cup), and the static phenomenon generally does not occur. The ink viscosity is below 16s (Zahn Cup No. 3), as the viscosity becomes smaller, static phenomena such as whiskers, stripes, edge repulsion, flying ink, poor transfer, and extremely irregular water stains of pigments will occur. . Therefore, in the actual printing process, special attention should be paid to the change of the printing ink viscosity. 2. Flying ink In gravure printing, when the printing speed exceeds 0.3m / s, if domestically produced chlorinated polylactone resin with a wide molecular weight distribution is used and the viscosity of the printing ink is low, it may bring flying ink The problem. The reason is that the viscosity of the ink is too low, the cohesion of the ink is greatly reduced, when the ink is transferred to the printed film, the low molecular weight resin is easily separated, and small ink dots can be seen in the blank part of the printed product. Solve the problem of flying ink, mainly from two aspects, one is to use chlorinated polypropylene resin with a narrow molecular weight distribution; the other is to appropriately increase the viscosity of the ink according to the printing situation. 3. Influencing the printing hue and adjusting the ink viscosity will make the color lighter and vice versa. However, in printing, you cannot change the color by adjusting the viscosity, otherwise it will cause other problems, such as water ripples and dull colors. When grading, it is necessary to grasp the variation of the viscosity of different colors to make better use of viscosity. For example, when the primary color yellow viscosity is large, there is a red side, and when the viscosity is small, it will show green; the green viscosity is blue, and the viscosity is yellow. 4. Produce watermark phenomenon Watermark phenomenon is mainly related to ink viscosity and printing speed, but usually the printing speed is fixed, so in most cases, the problem of watermark should be solved by increasing the ink viscosity. 5. Influencing the transfer rate and color saturation In gravure printing, the ink is transferred to the printing substrate by the ink of the indentation of the gravure, relatively speaking, India is too large, and the resistance between the ink molecules will be very large. It causes difficulty in splitting the ink layer, and there will be roughening or even peeling on the substrate, greatly reducing the service life of consumables such as blankets and printing plates. For example, in the printing of general UV inks, the reason why ordinary printing plates and blankets are easily damaged is because the viscosity of UV inks is particularly large. If the viscosity is too low, the cohesion in the system is also small, and the fountain solution easily penetrates into the ink during printing, emulsifying the ink, causing scumming and dot expansion. The ink is also not easy to adhere to the surface of the ink roller during transmission, causing poor ink transfer, and printing failures such as stacking, rubber, and ink stacking. Therefore, it is necessary to control the appropriate ink viscosity during production. Problems caused by improper adjustment of ink viscosity In plastic film printing, correct adjustment of ink viscosity is the key to ensuring printing quality. In summary, improper adjustment of ink viscosity will mainly cause the following problems. 1. Squeegee and plate cylinder are easy to be damaged. These larger particles are very easy to form linear or strip-shaped cutting lines during printing, and linear staining occurs. In addition, because the resin is also in a supersaturated state, a large amount of resin coalesces together, and the affinity of the resin to 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. Under the high-speed movement of the printing plate, the volume of the dot is basically fixed. As the viscosity of the ink increases, the viscosity of the ink also increases, and the more ink transferred from the dots, the higher the color density and saturation of the printed matter, but there are certain limits. When the viscosity of the ink continues to rise to a certain level, the transfer rate of the ink has also been synchronously increased. If the viscosity continues to rise, the viscosity will become stronger and stronger, and it will be difficult for the ink to enter small dots Less and less, the transfer rate of ink began to gradually decline, and the color density of the printed matter also began to decline. Generally speaking, when printing a shallow screen, a smaller viscosity is very helpful to improve the transfer of ink, to avoid the appearance of bad white spots. In general, the viscosity of gravure ink can be considered controlled at 13 ~ 19s. 6. Blocking plate When the viscosity of the ink is too large, the entire ink system is in a state of supersaturation, and the fluidity of the pigment and other substances is poor. When the viscosity of the ink is too high, the pigment cannot even enter the mesh at all, let alone—upward—moves, which is the so-called blocking phenomenon. Therefore, let the resin, pigment, etc. not be in supersaturated state in the colloid system composed of organic solvents, and let the pigment and other substances be well dispersed in it to form a uniform and delicate colloid system, and the pigment will enter and exit the mesh smoothly. Some ink manufacturers recommend that the viscosity of the ink be between 15 and 18 s (Cahn viscosity cup No. 3). But in practice, especially in high-speed gravure printing, in order to ensure a good forwarding effect, and at the same time can print for a long time, improve efficiency, the ink viscosity is generally controlled at 11 ~ 15s. 7. Affect the gloss of the printed matter When the viscosity of the ink is low (that is, more solvent is added to the original ink), the content of resin and pigment in the ink is reduced, and the ink is not easy to form a smooth ink after being transferred to the printing substrate and dried. membrane. Directly lead to lack of gloss in printed matter. Therefore, in order to obtain excellent gloss, it is necessary to ensure that the printing ink has a suitable resin and pigment content. 8. The phenomenon of cutting line occurs, especially when printing the gradation plate, there is no cutting line at the beginning of printing, or it is very small, and it will become more and more serious after not printing for a long time. There is also a situation where the knife lines all appear at the positions where there are nets, and they are all at the starting point. Smaller ink viscosity can prevent the occurrence of knife lines to a great extent. 9. Influencing the effect of scraping ink is large, and the effect of scraping ink is not good (referring to dirty scraping), especially for black ink, it is generally prevented with a lower viscosity Scraping is not clean. 10. One case is that the ink of the latter color cannot be printed on the ink of the previous color. At this time, the viscosity of the ink of the latter color should be adjusted down. 11. The viscosity of the printing ink is higher than 16s (Cahn Cup No. 3) generally does not generate static electricity; if the viscosity is lower than 16s, static electricity will be generated, and beard-like, streak-like, edge repulsion and other failures will easily occur. However, if the printing ink viscosity is below 15s, static electricity will be generated and affect printing. According to practice, try not to use the method of increasing the printing ink viscosity to reduce or avoid static electricity, because increasing the ink viscosity will not only increase printing costs but also bring printing transfer Due to difficulties, printing faults such as dirty plates are likely to occur. The purpose of eliminating static electricity can be achieved by changing the diluted solvent ratio or adding a small amount of antistatic agent as appropriate. The requirements for the viscosity of ink in printing mainly depend on factors such as the printing speed of the printing press, the degree of softness of the paper, and the temperature and humidity changes in the surrounding environment. The factors that affect the viscosity of the ink mainly include the temperature and pressure of the environment, the volume ratio of the pigment to the binder in the ink composition and structure, the size and shape of the pigment particles, the presence of the surfactant and the thixotropy of the ink. Generally speaking, it is mainly carried out from two aspects of adjusting the composition and structure of the ink and controlling the thixotropy of the ink. Bleached Poplar Commercial Plywood Bleached Poplar Commercial Plywood,Bleached Poplar Hardwood Plywood,Bleached Poplar Faced Plywood,White Bleach Poplar Plywood Shandong Yami Import and Export Co., Ltd. , https://www.yamiplywood.com