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 printed ink is one of the important factors to measure the quality of printed matter. The following are the conditions that directly affect the ink color of printed products.
(I) Influence of the thickness and material of the printing ink layer on the ink color of the printing ink The proper printing ink layer is an important measure to ensure the ink quality of the printing ink and prevent the printing ink from being dirty. If the ink layer is thicker, its viscosity will inevitably increase, and it will easily lead to paper pull, which will affect the evenness of the printed ink. If the printing ink layer is thin and the ink viscosity is insufficient, the printed ink will be too light, and the visual effect of the printed product is also Just bad. As the printing machine's rotation time is extended or the printing speed is increased, the friction coefficient increases, and the ink temperature also gradually increases. Therefore, the ink becomes thin and its viscosity decreases accordingly. Therefore, these conditions must be taken into consideration when transferring ink to ensure that a batch of products can obtain a relatively balanced printing ink color. However, in the actual production process, the decrease of the ink viscosity is unavoidable, and the ink of the printing product is often thick at the beginning of the printing process, and is faded afterwards. The adjustment can be achieved by appropriately adjusting the rotation angle of the ink transfer roller. The amount of ink keeps the shades of ink before and after. In addition, in order to prevent the ink viscosity variation from being too severe and affect the balance of ink color, the contact between each roller and the iron roller should not be too tight and the glue should not be too hard to minimize frictional heat and keep the ink properly. concentration.
(B) the impact of printing pressure on ink color printing pressure is one of the important conditions for the imprint transfer, because the surface of the printing plate is not absolutely flat, the surface of the paper will inevitably have subtle uneven shape and uneven thickness, if When the printing pressure is insufficient or uneven, the printing ink will inevitably appear uneven. Therefore, the ideal printing process is based on the "three levels" (ie, the plate surface and the ink roller and the lining body are relatively flat to obtain good contact conditions), and the thinner ink layer is used to achieve a balanced printing pressure. , to get a more uniform ink on the print. If the printing pressure is insufficient or uneven, there is a poor contact between the lining body and the printing plate surface. By increasing the amount of ink to be fed, the visual effect of the ink on the printing surface can be satisfied, but this not only increases the consumption of ink, but also occurs easily. Dirty printed products are undesirable.
(3) The effect of the quality of the rubber roller on the ink color of the printing ink In terms of the printing and printing technology, whether the printing product can obtain the ideal ink color has a close relationship with the quality of the rubber roller. The equipment for printing color prints is equipped with an ink transfer roller, an ink roller and an ink roller. There are five or six or even more than ten ink meter rollers, of which the ink roller and the ink roller are the most influential factors in the ink shade. The quality of the rubber roller is mainly manifested in the aspects of elasticity, stickiness, roundness, and surface finish, while the main influence on ink density is stickiness. In the printing process, the rubber roller only maintains a certain viscosity to ensure that the amount of ink applied to the printing surface is uniform during each printing cycle. However, in the actual production process, the stickiness of the rubber roller is not stable, because of the ink The increase of paper dust affects the viscosity of the colloid; secondly, the viscosity agent (ie, glycerine) on the surface of the colloid loses as the temperature increases and the time of use increases, the stickiness of the surface of the rubber roll gradually decreases, and the ink absorption performance declines correspondingly. Printing ink balance. Therefore, the printing plate product should use a more stable quality polyurethane roller. If printing bulk products, clean the rollers at a proper time.
(4) The effect of differences in paper quality on the ink of printed products In fact, the relationship between paper and ink is complicated. If only considering the shade of ink in a book, it should be noted that the smoothness of the surface of the paper has a certain degree of ink. Relationship. If the pressure of each plate is the same, the smoothness of the surface of the paper is inversely proportional to the amount of ink consumed. If the smoothness is good, the amount of ink sucked is small, and vice versa, the amount of ink sucked is large. Therefore, if there is a difference in the smoothness of the positive and negative sides of the paper, the method of increasing the amount of ink and the pressure should be taken as appropriate and appropriate adjustments can be made. The printing is used to print glossy first, and when the rough surface is printed later, the pressure and the ink supply are appropriately increased, so that both the positive and negative ink colors have an ideal visual effect. Practice has shown that the effect of the above method is much better than simply increasing the amount of ink delivered, and the printing quality is better.
(5) The effect of light changes on the ink color of printed products Usually, light sources of printed ink are identified as sunlight, fluorescent light and electric light. The light emission of these three light sources is different, and the color of the emitted light is different. The daylight is pure white light, the fluorescent light is white with blue, and the electric light is reddish and slightly yellowish. Although sunlight and fluorescent light sources are somewhat similar, the differences between the two should be taken into account when identifying higher quality products. The effect of light on the identification of ink is not only the light source, but also the light intensity and the irradiation angle. Under the same light source, the intensity of the reflected light on the sample sheet is mainly determined by the distance between the proof sheet and the light source, and the strong and weak ones are weak. The correct angle of illumination should be the angle of incidence equal to the angle of reflection. Irradiation on the proofs will inevitably result in partial refraction, but it does not have much influence on the identification of ink. In the identification of ink color, whether it is day or night should be carried out in the same light intensity and irradiation angle, in order to prevent ink mis-correction caused by color cast or before and after the ink variation.
(6) Overprinting is not allowed to affect the color of ink. Products with dot quality, whether the overprint of each color plate is accurate, will have a great influence on the printing hue. The accurate hue effect of the overprinting is also good, and the overprint of the overprinted print will be deviated. This is due to the difference in the position of overprinting of each color dot, which inevitably produces a visual color difference. Therefore, for printing textured color products, overprinting must be precise to ensure that the printing hue meets the process requirements. In order to prevent the paper stretching and variability from causing misalignment and color deviation, for quality products with high quality requirements, multiple color machines should be used to complete the overlapping color printing at a time. (to be continued)
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Place of Origin: Guangdong, China(mainland)
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