Printing color sequence
In multi-color overprinting, the process of monochromatic overprinting is overlaid in a certain order, and finally restored to the original document, which is called the ink color overprinting sequence, or color sequence for short.
In traditional offset printing, the same set of printing plates, the same type of paper, the same series of inks, the same type of offset press, the same temperature and humidity, the same operator, due to the difference in printing color sequence, the color effect of the printed product is It won't be the same.
There are 24 kinds of overprint color sequence according to the arrangement and combination of four-color printing.
If you add light or spot colors, the combination of overprint color sequence is more. Generally, the color sequence of the most common models in actual production is as follows:
Table 5-1 Color sequence arrangement of common models
Note; for reference only
The arrangement of printing color sequence is subject to various conditions. In order to obtain a good reproduction effect, the following basic principles are generally followed:
(1) Arrange the color sequence according to the brightness of the three primary colors: the dark color is printed first, and the bright color is printed later.
(2) Arrange the color sequence according to the transparency and hiding power of the three primary inks: ink with poor transparency is printed first, and ink with strong transparency is printed after.
(3) Arrange the color sequence according to how much the dot area occupies: Generally, the small dot area is printed first, and the large dot area is printed later.
(4) Arrange the color sequence according to the characteristics of the manuscript: the graphics with warm tone are printed first in black and cyan, then the magenta and yellow; the graphics with cold tone are printed first in black and yellow, and then the magenta, green.
(5) Arrange the color sequence according to the model: the color sequence of the monochrome or two-color offset press is generally yellow, magenta, cyan, black or black, cyan, magenta, and yellow.
(6) The color sequence is arranged according to the nature of the paper: smooth and tight paper is printed with dark colors first, and then bright colors; while thick and loose paper is printed with bright colors first, and then dark colors.
(7) Arrange the color sequence according to the dryness of the ink: slow drying ink is printed first, and fast drying ink is printed after.
(8) Arrange the color sequence according to the flat screen and field: the flat screen image and text are printed first, and the field structure is printed later.
(9) Arrange the color sequence according to light and dark inks: dark ink is printed first, and light or spot color ink is printed later.
(10) According to the rules, it is convenient to arrange the color sequence according to the registration and color change: the main color or strong color registration should be printed in one piece or next to each other, and cannot be separated at will. In addition, the color sequence must take into account the convenience of color change, otherwise it will increase the auxiliary time. [next]
For multi-color offset presses, in the wet press wet printing state, whenever the first color ink film printed on the paper will be overprinted in the second color, the third color and the fourth color, it will be sequentially erased The cloth roller sticks away some ink. Among them, only the third color ink is the least sticky, but the fourth color ink is 100% retained on the paper. It can be seen that the third color sequence and the fourth color sequence constitute the most critical two in the printing color sequence Color order. Therefore, the decisive colors must be arranged in the third and fourth color sequence, so that it can meet the requirements of any tone original and it is easy to restore the tone. At the same time, the effect of ink hiding is avoided. Therefore, it is necessary to better highlight the main tone of the picture. In short, the color sequence arrangement is a very important and complicated problem, which must be analyzed concretely and must not be done blindly.
For a monochrome offset press, it is printed in a wet press dry state, so the color sequence arrangement cannot replicate the color sequence of a multicolor offset press.
[Case: 5-4]
A unit printed a cigarette pack with a J2205 machine, the pattern is a large butterfly. It uses 80g /? Single-sided coated paper. The color sequence is black, blue, red, and yellow. As a result, it is found that the serious overprint is not accurate, and almost all the printed products are scrapped.
[Case Analysis]: The paper used in this product is the most easily stretchable paper, so special attention should be paid to the arrangement of color sequence and the control of the wetting fluid when printing. Obviously, the first two colors are black, blue, red, yellow After the group is printed in two colors, the blue and red points in the two-color group will inevitably cause overprinting. From this, it looks like this paper is printed with J2205 machine, and the color sequence should be yellow, black, red, blue better.
[Case 5-5]
A factory used a four-color monochrome offset press to print an advertising poster, using 128g /? Double copper, and the number of copies was 1,000. The color sequence adopted by the operator is black, sky blue, magenta, and yellow, and the overall picture displayed by the printed product is dull and dark.
[case study]:
For monochrome machines, this color sequence arrangement is unreasonable. One is that it is not conducive to color change and cleaning. The other is that the black and blue colors are too large and small, which cannot be compensated for behind. If the printed product is dull and dark overall, it means that black, sky blue and ink colors may be too large. So this color sequence arrangement is unreasonable. It should be more reasonable to print in the color sequence of sky blue, yellow, red and black.
[Case 5-6]
A factory used white embossed paper to print the color inserts of a magazine. The model used was the J2108 machine. The color sequence was sky blue, yellow, magenta, and black. As a result, the effect of the printed product was poor. The main reason is that the stereo experience of color pictures is not strong.
[case study]:
The above phenomenon often occurs. The surface of substrates like embossed paper is not smooth, and the black absorption is poor. Therefore, the color sequence should be corrected to: yellow, magenta, cyan, and black. The reason is that the yellow version generally has a longer tone and a larger area. Printed on embossed paper, it can play a good role in the background color, and then magenta, cyan, black ink in sequence. The effect is like this.
[Case 5-7]
A customer wants to print a batch of magazine covers, most of the background color of the cover is "Technical Blue", that is, the magenta is 25% network cable and the cyan is 100% solid. When printing on a four-color offset press, the conventional color sequence is black, cyan, magenta, and yellow. When printing, blue solids often appear dark. Later, the problem of reducing the viscosity of magenta ink and increasing the viscosity of cyan ink has not been solved.
[case study]:
Because the four-color offset printing machine is wet stacked wet printing, when another color ink is overprinted on the wet field, the transfer effect is poor, and the ink transfer rate is low. In this example, if the magenta is placed in front of the cyan, that is, the color sequence is black, magenta, cyan, and yellow, this sample red will be 100% transferred to the paper, the transfer rate is the highest, and the cyan solid Three quarters of the area is directly transferred to the paper, and the printed matter is relatively plain.
Treatment method: First, use good coated paper and high-grade ink to print. The second is to change the printing color sequence.
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