Analysis of the principles that should be followed

Analysis of the principles that should be followed in the selection of printing color sequence

1 greatly reduces the probability of screen fragmentation. The color sequence is arranged according to the lightness of the three primary colors

the lightness of the three primary colors ink is reflected in the lightness of the three primary colors ink. The test results are intuitively displayed to the user on the spectrophotometric curve. The higher the reflectivity, the higher the brightness of the ink. Therefore, the brightness of the three primary color ink is yellow> Green> magenta> black. Those with small lightness shall be printed first, and those with large lightness shall be printed later

2. Arrange the color sequence according to the transparency and hiding power of the three primary color inks

the transparency and hiding power of the inks depend on the refractive index difference between the pigment and the binder. The ink with strong covering has a great influence on the color after color superposition. As a post printing color, overprint is not easy to show the correct color and achieve a good color mixing effect. Therefore, the ink with poor transparency is printed first, and the ink with strong transparency is printed later

3. Arrange the color sequence according to the size of the dot area

generally, those with small dot area are printed first, and those with large dot area are printed later

4. Arrange the color sequence according to the characteristics of the original

each original has different characteristics, some are warm colors, some are cold colors. In the arrangement of color sequence, the color sequence dominated by warm tones is black, blue, magenta and yellow; The color sequence dominated by cold tones is black, magenta, cyan and yellow

5. Arrange the color sequence according to the different printing equipment

⑴ monochrome machine color sequence: when monochrome machine prints multi-color products, the ink transfer belongs to wet stacking and drying. When considering the color sequence, the ink viscosity can be put in a secondary position

under the condition of good paper and ink quality, the general printing color sequence is black, cyan, magenta and yellow. When the paper quality is poor, the surface is rough, the tightness is low, and the ink absorption is strong, the color sequence can be selected as yellow, magenta, cyan, and black. Due to the large area of the yellow plate, it can make up for the defects of the paper. Make the printing effect better. In addition, the sequence of yellow, magenta, cyan and black is conducive to color change and easy to clean the ink roller and ink tank. Another reason for monochrome Offset printing machine to print yellow version first is that human vision is not sensitive to yellow dots. When printing light color yellow version, even if there is a little inaccurate overprint, it is not easy to observe with the naked eye, which is conducive to the effect of four-color overprint

⑵ in the printing of two-color machine, the second color and the third color belong to wet stack dry overprint. The printing of 1-2 colors and 3-4 colors belongs to wet stacking and wet overprint. The printing color sequence of the two-color machine should be alternating between bright and dark colors, and the one with a large amount of ink should be placed in the second color group. Therefore, the following printing color sequence is generally used in printing: 1-2 color magenta green or green magenta; Color black yellow or yellow black, but also as needed. If the machine is in standby mode: heavy color, such as green, it should be printed according to the overprint color sequence of magenta yellow and green black, so as to obtain a better printing effect

the color sequence can also be black yellow, magenta green, which is easier to control

⑶ four color machine printing is a wet press wet printing method. In order to make the ink of the latter color be better transferred to the ink layer of the substrate of the former color, the adhesion of the ink should be reduced in turn along the printing color sequence, otherwise reverse printing will occur. Generally, the dark color with high ink viscosity is printed first, and then the bright color with low ink viscosity is printed. The commonly used color sequence is black, cyan, magenta, yellow, or black, magenta, cyan, yellow. While changing the color sequence, the viscosity of the ink should also be adjusted accordingly

in four-color machine printing, yellow ink is printed in the last color, which has three main advantages:

⑴ due to the good transparency of yellow ink, using it in the last color is conducive to sufficient light entering the upper and lower ink layers, making the printed matter more colorful

⑵ yellow ink has faster drying performance and larger printing area. Arranging the yellow ink as the last color can not only prevent the crystallization caused by the rapid drying of the yellow ink, but also take advantage of its large printing area and fast oxidation of the conjunctiva. Covering it on the surface of other ink layers can improve the gloss of the printed matter

⑶ yellow is arranged to be very perfect for each patient. The last color is convenient to control the ink amount of yellow, which can be adjusted against the sample at any time

6. Arrange the color sequence according to the nature of the paper

the smoothness, whiteness, tightness and surface strength of the paper are different. Flat and tight papers are printed with dark colors first and then bright colors; Thick and loose paper should be printed with bright yellow ink first and then dark color, because yellow ink can cover paper defects such as paper wool and powder