General printed manuscripts can be divided into monochrome and color manuscripts, and monochrome manuscripts are also called black and white manuscripts. In addition to the monochromatic manuscripts printed with the primary color ink, these manuscripts have problems of color. In this case, according to different manuscripts, the actual conditions thereof are analyzed, and different coloring methods are used for printing. The usual color forming methods include a stacking color method, a mixing color method, and a dot color forming method.
First, stacking color method
Plain-colored manuscripts, such as the picture, have only saturated primary colors, equal amounts of mixed saturated colors, and complex colors. Such manuscripts can be printed by the method of superimposed colors. The advantages of this coloring method are:
1. The stacked part is thick in ink and very bright in color.
2. You can save the number of plates, save costs, and increase printing efficiency.
3. Since the original ink is used, there is no waste of ink.
However, this method of coloring also has many drawbacks:
1. The poorly-colored image means that the ink is white and dull, or the former color of the first printing is peeled off by the color of the after-printing, so that a "flowering point" or hue change occurs due to the non-transferability of the ink. The solution is to adjust and control the viscosity of the ink. The viscosity of the ink changes with the degree of drying of the ink. At the beginning, as the degree of drying increases, when it reaches a certain maximum value, it gradually decreases with the increase of the degree of drying. When the ink is completely dry, it loses its viscosity, so by controlling the degree of drying of the ink The viscosity of the ink can be controlled. The degree of drying is mainly controlled by the use of drying air volume, temperature, and preparation of fast (slow) dry solvents. The viscosity of the previous color ink should be greater than the latter color. In addition, the overprint defect can also be solved by increasing the ink supply amount of the latter color printing plate.
2. The hue is easy to change and difficult to control, especially when multiple colors overlap, a slight change in the ink transfer of any one color will affect the hue change of the results of the overlap.
The following problems should be noted when using the achromatic synthesis method:
1. The various inks used must be transparent and the bleaching agent must not be white ink.
2. The overlapped area should not be too large, and the plated holes should not be too deep. Otherwise, the pull-off phenomenon is likely to occur, making the ink inhomogeneous and the hue very difficult to control. At this time, another coloring method should be adopted.
3. The stacked ink is preferably the same ink factory, so as to avoid mutual exclusion due to the different characteristics of the ink.
4. When overlaying, it is necessary to fully consider whether overprinting is difficult.
Second, mixed color method
Some of the colors on the original screen are not saturated and mixed in equal amounts, but mixed colors and complex colors in different proportions. Such manuscripts cannot be printed by the above-mentioned composite color method, but like the painter, they must be based on the original. The color samples are mixed with the color inks to print the desired colors. Due to the low color saturation obtained by the hybrid color method, it is impossible to print a very bright inter-color in this way. The black color on the screen and the lowest-tone color are not good with the hybrid color method. The effect is that because of the juxtaposition of the various ink particles in the color mixture, there will always be a white light component, so the black is not dark, and the dark place does not go dark.
The advantage of the hybrid coloring method is that because of the spot color ink, the hue is easy to maintain - and it is easy to control. The disadvantage is that the waste of ink is large, especially when the amount of printing is small. In addition, its color is not thick enough, easy to produce water-like phenomenon or some fine whisker, especially complex ink. When printing mixed spot inks, they should maintain a relatively high viscosity and properly add some isopropyl alcohol or antistatic agent. The printing effect will be good - some.
Third, network color method
The method of superposition and color mixing of three primary colors of ink can only be used for the reproduction of manuscripts with relatively simple color and flat color, such as layout, paper cutting, pattern painting, and decorative background and pattern printing, in case of color and shade, The manuscripts with continuous changes in shade and hue, such as watercolours and oil paintings, cannot do anything. This is because there are tens of thousands of colors on the screen and it is impossible for printing to prepare so many colors for overprinting. Moreover, the colors on the screen are continuously changing. It is also impossible for printing to use the same shade of ink while printing different shades of color.
In fact, the dot coloring method is a special coloring method. It has both the method of superimposition and color mixing. The light-colored parts on the screen are very small. Each color point is juxtaposed and does not overlap. At this time, the color is mainly formed by the mixed color method. The dark part of the screen-death is dark, and the color is dark. Also large, most of each idea overlaps with each other, so this part is dominated by overlapping colors, and the middle tone part, both half and half.
The dot quality method has very high quality requirements for printing plates. Without high quality printing plates, it is difficult to print high-end products. In particular, some shallow screen printing plates reflect the technical level of a platemaking plant. At the same time, the printing of these outlets is also an inspection of the printing level. The ink transfer rate, fine intermittent line marks, hue change and other issues are often involved in dot printing in the dot color forming method.
To print high-end products in addition to requiring the printing operator to have a higher level of technology, but also the need for design, plate-making personnel, that is, according to the characteristics of the manuscript to choose a reasonable color method for printing convenience. (Text / Dai Chun)