Influencing the ink color of printed matter Plate printing is a widely used production process. How to improve the quality and production efficiency of color prints is worthy of analysis and discussion. The visual effect of the ink color of the printed matter is one of the important factors to measure the quality of the printing. The following situations have a direct effect on the ink color of the printed matter. (ï¼) The effect of printing ink layer thickness and viscosity on ink color Appropriate printing ink layer is an important measure to ensure the quality of the ink color of the printed product and prevent the printed product from sticking. If the ink layer is too thick, its viscosity will inevitably increase, and it is easy to produce paper wool, which affects the uniformity of the ink color of the printed product. If the printed ink layer is thin and the ink viscosity is insufficient, the printed ink color will be lighter, and the visual effect of the printed product will also be light. Just bad. As the rotation time of the printing press increases or the printing speed increases, the coefficient of friction increases, and the ink temperature will gradually increase, so the ink will become thinner and its viscosity will decrease accordingly. Therefore, when adjusting the ink, these conditions must be considered comprehensively to ensure that the batch of products obtain a relatively balanced printing ink color. However, in the actual production process, the decrease in ink viscosity is inevitable. Often, the ink color of the printed product is thicker at the beginning of printing, and it will become lighter in the future. The supply angle can be increased by appropriately adjusting the rotation angle of the ink transfer iron roller. The amount of ink keeps the consistency of the ink density before and after. In addition, in order to prevent the ink viscosity from changing too much and affecting the balance of the ink color of the printed product, the contact between each rubber roller and the ink roller should not be too tight, and the colloid should not be too hard to minimize the friction and heat to keep the ink properly. concentration. (2) The effect of printing pressure on the ink color of printed products Printing pressure is one of the important conditions to achieve imprint transfer. Because the surface of the printing plate is not absolutely flat, the paper surface also inevitably has fine unevenness and uneven thickness. If the printing pressure is insufficient or uneven, the printing on the plate surface Ink color will inevitably appear uneven. Therefore, the ideal printing process is based on "three flats" (that is, the plate surface and the inking roller and the liner are relatively flat to obtain good contact conditions), with a thin ink layer through the role of balanced printing pressure , To get a more uniform ink color on the printed product. If the printing pressure is insufficient or uneven, there is a poor contact between the liner and the printing plate surface. By increasing the amount of ink delivery, the visual effect of the ink color of the printing surface can be met, but this not only increases the ink consumption, but also easily occurs. Prints are sticky and dirty, which is undesirable. (3) The effect of rubber roller quality on printed matter and ink color As far as the relief printing and flat printing processes are concerned, whether the printed product can obtain the ideal ink color is closely related to the quality of the rubber roller. The equipment for printing color prints is equipped with three types of ink transfer roller, ink leveling roller and inking roller. There are five or six or even more than 10 ink rollers. Among them, the ink roller and inking roller have the greatest influence on the color density of ink. The quality of the rubber roller is mainly manifested in the aspects of elasticity, viscosity, center of roundness and surface finish, etc., and the main effect of the ink color is the viscosity. In the printing process, the rubber roller only maintains a certain viscosity to ensure that the amount of ink applied to the plate surface is uniform every printing cycle. But in the actual production process, the viscosity of the rubber roller is not stable. One is that the increase of paper dust in the ink affects the viscosity of the colloid; the second is the viscosity increaser (ie, glycerin) on the surface of the colloid as the temperature increases and the use time When extended and lost, the viscosity of the rubber roller surface gradually decreases, and the ink absorption performance decreases accordingly, thereby affecting the balance of the ink color of the printed product. Therefore, printed plate products should use polyurethane rubber rollers with relatively stable quality. If printing bulk products, the rubber roller should be cleaned in a timely manner. (4) The effect of the difference in cleanliness on the paper on the ink color of the printed product In fact, the relationship between paper and ink is complicated. If you only consider the ink color density of a book, you should note that the smoothness of the paper surface has a certain relationship with the ink color. If the pressure of each version is the same, the smoothness of the paper surface is inversely proportional to the amount of ink consumption, and the amount of ink absorption by smooth enthusiasts is small, otherwise, the amount of ink absorption is large. Therefore, if there is a difference in the smoothness of the front and back sides of the paper, the method of increasing the ink volume and pressure should be adopted as appropriate to make appropriate adjustments. In printing, it is customary to print the glossy side first, and then increase the pressure and ink supply appropriately when printing the rough side, so that the ink colors on the front and back sides present the ideal visual effect. Practice shows that the effect of using the above method is much better than simply increasing the amount of inking, and the printing quality is relatively good. (5) The influence of light changes on the ink color of printed products Generally, there are three kinds of light sources for identifying the ink color of printed products: daylight, fluorescent lamp and electric light. The three light sources have different luminous conditions, and the color of the emitted light is also different. The gaze is pure white light, the fluorescent lamp is white with blue, and the electric light is reddish and slightly yellowish. Although the light sources of daylight and fluorescent lamps are somewhat similar, the difference between the two should be considered when identifying products of higher quality. The influence of light on the identification of ink color is not only related to the light source, but also related to the intensity of the light and the angle of illumination. Under the same light source, the strength of the reflected light on the proofs is mainly determined by the distance between the proofs and the light source, the closer is strong and the far is weak. The correct irradiation angle should be the angle of incidence equal to the angle of reflection. Irradiation of light on the proof sheet will inevitably cause some refraction, but it has little effect on the identification of the ink color. When identifying the ink color of the printed matter, it should be carried out under the same light source intensity and irradiation angle at day or night to prevent color shift or ink color variation caused by ink adjustment errors. (6) The impact of overprinting on ink color For products with halftone dots, whether the overprint of each color printing plate is accurate will have a great influence on the printing hue. The accurate hue effect of overprinting is also good, and the hue of printed products that are not overprinted will be deviated. This is due to the difference in the position of the overprint of each color dot, which will inevitably produce visual color difference. Therefore, when printing textured color products, overprinting must be precise to ensure that the printing hue meets the process requirements. In order to prevent inaccurate overprinting and color deviation caused by paper expansion and contraction variation, it is better to use multi-color machine to complete multi-color printing at one time for the high-quality halftone dot products, in order to improve the overprint quality. In addition, the paper should be hung up to reduce the occurrence of sheet variation during the printing process.
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