Determination of printing color sequence and overp

2022-08-24
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Determination of newspaper printing color sequence and overprint efficiency

the overprint efficiency of ink is closely related to the printing color sequence. Because the color newspaper printing speed is high, the ink overprint time is short, the paper absorption is large, and the ink is a penetration drying method, its overprint color sequence should be different from that of other printing methods, so it is particularly important to choose a suitable color sequence for color newspaper printing. The determination of printing color sequence and overprint efficiency of newspapers is preliminarily discussed from the following aspects

1. Wet press wet printing

newspaper printing belongs to high-speed printing; From the perspective of ink overprint time, it belongs to wet pressing method; Due to the rapid absorption of paper, from the perspective of ink drying, the first and second colors belong to the wet press drying method, while the third and fourth color overprint belongs to the wet press wet method

2. Brightness of ink

put the ink with high brightness at the end, and the picture is more beautiful

3. Adhesion of ink

the adhesion of ink is: K ink, m ink, C ink, y ink. Generally, those with high adhesion are printed first. In addition to the biggest tack value, the reason why black is printed first is that the color of post printing is easy to register for black

when the requirements of the structural material of the water purifier for water plastics and the experimental requirements are the same as the printing state, the tack value will change, and it is usually difficult to accurately control the tack value of the printing ink. When the binder of the ink is absorbed by the paper, the tack value of the ink will increase, which occurs in a short time between the first color and the second color. The increased tack value during this time may have appropriately transferred the ink volume of the second color (the lower tack value) to the first color ink film. Therefore, each color of ink can have the same tack value

in addition to the minimum tack value, yellow ink must be post printed. The lack of visual concentration is also a reason for post printing. Because its ink film is thick, if you print yellow first, there will be an efficiency problem of transferring a thin ink film to a thick ink film. In this way, the tack value will be reduced and the viscosity grade between the first color and the second color will be destroyed

4. Absorption of paper

due to the large absorption of paper, in order to prevent through printing, it is not suitable to use the color sequence of printing black ink first

when printing, the ink film of the former color must reach a fixed viscosity before the latter color is successfully transferred to the former color. The fixing time must be shortened by using fast drying ink and adjusting tack value and density

the surface absorption of the substrate actually refers to the absorption of the second color and the last few colors overprint. On paper, when printing the first color, the ink film is almost completely absorbed immediately. For the second color ink, the surface characteristics formed by the first color ink film are almost similar to the surface of the unprinted substrate. In this case, even if there is no difference in the tack value of various inks, a high overprint rate can be obtained in wet overprint printing

5. Effect of dot increase

dot increase may be caused by excessive printing pressure or too thick ink layer on the printing plate. In two-color or four-color printing, it may be caused by reverse printing. When printing the next sheet, the ink film of the background color thickens or diffuses after printing because the rubber drum of the latter color is attached with the ink of the previous color. This situation is more serious for magenta ink, so magenta ink is usually printed later. To reduce the point increase phenomenon, you can print a special color after the ink that is easy to lead to the increase of the starting point; Or after the four-color printing, print a special color

6. Transparency of ink

the ink with the lowest transparency shall be printed first. Generally, the transparency of yellow ink is the lowest, and the absorption of paper is strong, which improves the printing of wet overprint

yellow ink is printed first, while dark ink is printed later. It is easy to overcome problems such as concentration change and registration error

now the transparency and gloss of yellow ink have been improved. When black ink is dry, it will produce a bronze luster hue, which makes people feel that the color is not pure, and the back printing of yellow ink can overcome this effect. Because the yellow ink usually has a large area and a wide coverage range, the yellow ink printing on the top layer can play the role of glossy surface, so as to destroy the influence of surface light scattering, and has the characteristics of brightening prints

the color reproducibility of yellow ink is weak. Therefore, the ink film is thicker when printing yellow first. Because the tack value of post printing cannot be higher than that of the previous color ink, yellow cannot be printed first

another reason not to print yellow first is to avoid dot enlargement. Because yellow ink usually needs to be printed thick and has a large coverage, especially in full plate printing, if it is printed first, it will change the hue of the substrate surface and increase the possibility of other post printing ink spots

7. Overprint problem

mainly for the size of the substrate, printing ink that causes small paper flexibility first is conducive to registration

8. Color deviation

different printing color sequences will affect the final hue, which generally depends on the characteristics of the printed matter

9. Overprint area

for post printing with large area, unless the ink used has high opacity, because the transfer ability of the ink on the paper surface is much better than that on the ink film. If you print a small area first and then a large area, the overprint part is directly printed on the paper for a small area, and the ink color transfer is good, so this kind of overprint effect is good. On the contrary, if you print a large area first and then a small area, performance management can be free. Although the problem of thankless performance is transferred well in a large area, for a small area, the printing ink is all stacked on another color (large area) ink film, and the color performance is poor. For the overall effect, it is not as good as the former

10. Ghosting problem

usually in four-color printing, black is the first color printing. The black version of the newspaper is the same as the text, and black ink accounts for a large part, and the paper is poor, which is prone to reverse transfer, causing the risk of ghosting. Ghosting will blur the text. In this case, black should not be placed in the first color, preferably in the last or third color printing

analyzing the above factors, there are contradictions in some places. For any example, all conditions cannot be met. The determination of printing color sequence depends on the specific situation

nowadays, most newspaper printing houses use c-m-y-k printing color sequence, because compared with other color sequences, this printing color sequence is easier to control. Generally, the black version of color newspaper printing is short, and the paper has strong absorption. If black ink is printed first, the black ink on the black version will be immediately absorbed by the paper, which will not play the role of increasing the density and contrast of the black version; Newspapers are mainly written, with a large amount of black ink. The strong absorption of paper leads to that if the black ink is printed first, it is easy to cause through printing and reverse transfer printing, while printing last can reduce the impact of these adverse factors and is conducive to the drying of the ink; In addition, in the text area, non graphics and text account for the main part, and there is more fountain solution. Under the same processing conditions, the third stage of strong absorption of paper smelling is 2026; (2) the year 030 is easy to cause sticky dirt, and the paper will deform after absorbing a large amount of fountain solution, affecting the registration of other ink colors and producing ghosting. Therefore, black is usually printed last

source: Printing Technology

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