Screen printing is known as "all things except air and water can be printed." It has such a wide range of printability, printing ink thickness, layout soft, and not subject to the limitations of the size, shape, and material of the printed object, which cannot be replaced by other printing methods. It is also for these reasons that there are a wide variety of screen printing products, from smooth surfaces to rough surfaces, from paper, fabrics to sheet metal, glass, and so on. With the advent of high-quality photosensitive adhesives and inks, people hope that screen printing can print things that can only be printed by offset printing in the past. Therefore, many people directly take the color separation sheets of offset printing to print, but the printed results are always inexhaustible. It is not a serious loss of tone, but a serious color cast that produces a moire pattern that is difficult to see. The reason why this phenomenon occurs is that they are not very clear about the factors affecting the change of the screen printing point, and thus cannot be quantitatively controlled. For this reason, this paper makes a simple analysis of the factors that influence the change of screen printing dots, such as dot shape, number of screens, printing materials, ink, exposure time, etc., to provide a certain reference for color screen printing tone reproduction.
1 Effect of dot shape on dot changes
First of all, using Coreldraw8 as a test tool for gray-scale testing - gray scale ladder, its tone range is 5% -100%. The production line uses 40lpi, 60lpi, 80lpi, and 100lpi screen respectively, and the screen angle is 45 degrees. The screen points are selected as circular and square dots. The experimental materials used were coated paper, offset paper, 300 mesh screens, screen printing inks (fluorescent peach, fluorescent yellow, fluorescent blue), offset printing inks (red, sky blue, medium yellow, magenta), loved with X-RITE 528 Selenium densitometers and transmission densitometers measure the percentage of dots. Experiments were performed using the above experimental materials and instruments to obtain experimental data (as shown in the following tables). Based on these data, the percentage of dots on the film (F0) was taken as the abscissa, the percentage of dots on the printed matter (F-print) and the percentage of dots. Delta (â–³F) is the vertical axis (difference between the percentage of the print dot and the percentage of the film dot) Draw the dot change curve
2 Influence of the number of network lines on the change of network points
Experiment 2 Printed with the same number of screens, the same exposure time, the same substrate, the same exposure time, the same substrate, the same type of ink (40lpi, 60lpi, 40s, square dot, coated paper, offset red ink), The measured data are shown in Table 2.
From the data of Experiment 2 (Table 2) and the dot change curve (Figure 2), it can be seen that the higher the number of screen lines is, the higher the dot gain value is, and the larger the dot gain value is, indicating that the image is clear In this case, the greater the difference between the number of color separation screen lines and the number of screen meshes, the better the tone of the picture can be maintained; and the possibility of repetitive interference patterns is smaller, because 300 points of wire were used in this experiment. The net, when using a 100 lpi screened dichroic film, a moiré pattern has appeared on the produced plate.
1 Effect of dot shape on dot changes
First of all, using Coreldraw8 as a test tool for gray-scale testing - gray scale ladder, its tone range is 5% -100%. The production line uses 40lpi, 60lpi, 80lpi, and 100lpi screen respectively, and the screen angle is 45 degrees. The screen points are selected as circular and square dots. The experimental materials used were coated paper, offset paper, 300 mesh screens, screen printing inks (fluorescent peach, fluorescent yellow, fluorescent blue), offset printing inks (red, sky blue, medium yellow, magenta), loved with X-RITE 528 Selenium densitometers and transmission densitometers measure the percentage of dots. Experiments were performed using the above experimental materials and instruments to obtain experimental data (as shown in the following tables). Based on these data, the percentage of dots on the film (F0) was taken as the abscissa, the percentage of dots on the printed matter (F-print) and the percentage of dots. Delta (â–³F) is the vertical axis (difference between the percentage of the print dot and the percentage of the film dot) Draw the dot change curve
2 Influence of the number of network lines on the change of network points
Experiment 2 Printed with the same number of screens, the same exposure time, the same substrate, the same exposure time, the same substrate, the same type of ink (40lpi, 60lpi, 40s, square dot, coated paper, offset red ink), The measured data are shown in Table 2.
From the data of Experiment 2 (Table 2) and the dot change curve (Figure 2), it can be seen that the higher the number of screen lines is, the higher the dot gain value is, and the larger the dot gain value is, indicating that the image is clear In this case, the greater the difference between the number of color separation screen lines and the number of screen meshes, the better the tone of the picture can be maintained; and the possibility of repetitive interference patterns is smaller, because 300 points of wire were used in this experiment. The net, when using a 100 lpi screened dichroic film, a moiré pattern has appeared on the produced plate.