Explore color overprint

"Printing in the United Kingdom" No. 9 of 2000 Printing is no longer an art. It is science and it is a full-fledged technology. Before computers can replace printing, there are still a lot of things that need to be printed. Printing is the fastest-growing technology at this stage and goes hand in hand with computer science, information technology and electronics. In order to computerize and standardize processes, various key factors need to be monitored in controlling quality factors. Offset printing is still the most popular printing process. Therefore, considering the environmental, health and safety issues, we must also be aware of technology development. In today's modern printing press environment, there are a large number of technical parameters that need to be controlled in order to monitor the finished product and standardize it. One of the areas of concern in wet-press wet color printing with nested inks is the overprinting of the ink. This is a measure of how much color an ink can overprint when it passes from the blanket to the paper. This is very important from the perspective of controlling color values. As the overprint value changes, the color value also changes. Therefore, controlling this parameter makes it difficult to control the color value. In addition, other issues of management and printability will arise. In the measurement, it is assumed that the thickness of the ink layer is proportional to the optical thickness of the ink layer. In other words, it is assumed that the thickness of the ink layer is proportional to the amount of light absorbed by a given ink layer. The concept behind this relationship is to inspect the actual ink film thickness indirectly because it is not possible to measure the thickness of each layer of ink using any known method. When measuring the density of four-color inks and their density when they are superimposed in different combinations, only the brightness value can be measured. Single-layer spectral color values ​​are not taken into account. This is because the purpose is to simulate the thickness of the ink film, in which case the hue of a single color block is not a concern. If the overprint value is also calculated when the density value is measured, an error occurs. When determining the color sequence of the process color in printing, the relationship between stickiness, overprint and color sequence must be considered. In terms of printability factors, the tack values ​​of four set colors are considered. First, the viscosity of the lower color ink should be the largest. The stickiness of the second color ink should be slightly smaller. Finally, the viscosity of the third and last color inks is minimal. This is essential because if the stickiness of the first color ink is less than the stickiness of the second color, it will be stick back from the paper by the second color ink during overprinting. This not only deteriorates the color value, but also creates printability problems. Undesirable pattern failures occur due to anti-overprinting of the ink. There are many other factors that dominate the color sequence of four-color printing. In general, it is best to place the darkest color on the final print to reduce backordering and produce dirty print defects. For example, the black version should be printed on the last color. Other colors should be arranged according to the order of their colors. According to this logic, the color sequence should be YCMK. However, if the color of the image is not superimposed on the color, then this logic obviously does not hold water. For example, clear text overprinting on other colors is generally not normal and therefore does not produce a dirty layout. Considering that the color ink is translucent, the color sequence of the ink should be CMYK. However, yellow is the color that gives the image its overall brightness and should be printed as the last color so that its transparent nature is not overwhelmed by other overprint colors. For a test, the same image is printed on the same type of ink and paper using the same machine with the same machine settings, but one is printed in CMYK color sequence and the other is YCMK color sequence, in CMYK color order. Printed sheets will appear brighter because the CMYK color sequence places yellow on top of the cyan and magenta inks. Therefore, compared with other printed sheets printed in YCMK color sequence, yellow has a greater chance of enhancing the overall brightness value of the image. Also, if you want to reduce anti-overprinting and subsequent printing failures, yellow should be printed last in the color sequence. Yellow appears more colors in most images, so the possibility of yellow ink being overprinted by magenta, cyan, or black ink back onto the blanket is reduced by printing it as the last color. Therefore, any color sequence should leave yellow in the last color print. Little yellow is printed as the first color. If in a job, there are large solid patches on either side of the web, and there is a problem of loosening, then placing the yellow in the first color may reduce its spread or overprint. Not allowed to produce visual interference problems. Since the largest spread occurs in the first color, yellow will have the largest spread. Yellow is a bright color and a weak color, so its problem of visual disturbance caused by the scattering can be minimized. It should be noted that the importance of four-color printing overprints. When the second color ink is printed on the first color ink, the entire thickness of the second color ink on the blanket does not completely transfer to the substrate, and part of the ink is transferred to the substrate. The rest remains. On the blanket. The purpose is to determine the percentage of ink delivered to the substrate, which is achieved through indirect methods, and assumes that the density of the ink patch is proportional to the ink film thickness. First measure the density of the overprint. This density value is formed by combining the first color and the subsequent color. Since a transparent ink is used, the density of the first color ink still has some effect, although the second color and the third color ink are superimposed, and it also absorbs a part of the overall superimposed light. If the density of the first color ink is subtracted from the total superimposition density, the degree of absorption of light by the subsequent ink is obtained. This of course makes it possible to obtain a single value again, which results in a difference, which indirectly represents the amount of the second color ink or the subsequent color ink transferred to the first color ink. The amount of ink that the subsequent color ink adheres to the previous color is always less than the amount of the same ink printed on the substrate. The amount of ink delivered depends on the ability of the first color ink when overprinting the second color ink, that is, the amount of the second color ink overprinted onto the first color ink. In most cases, the actual situation is completely different. When reading the density reading, it is assumed that the ink patch has a uniform thickness over the entire image. Then, it can be assumed that the solid patches of ink are the same everywhere on the printed paper. However, this is not actually the case. The fiber properties of paper theoretically do not have a perfectly uniform density over the entire surface. Therefore, reading readings of optically non-uniform substrates can result in changes in density values. Due to the nature of the translucent ink being translucent, this disadvantage is inherited when measuring ink density. Therefore, it is considered that the ink ink film thickness is theoretically perfect and completely uniform. It is important to understand that theory and practice are interrelated. Theory and practice can be different to a great extent, so theory or practice cannot exist independently. We can use theory as the backing and practice to achieve success.