Discussion on Printing Color Sequence of Four-color Machine

At present, color printing is usually performed by using yellow, magenta, cyan, and black four-color plates and superimposing them in a certain order.
Theoretically speaking, four-color printing or twenty-four different printing color sequences, using the yellow, magenta, cyan, and black four-color versions, regardless of the printing sequence, should achieve satisfactory results. However, there are many factors that affect the color of printed materials, such as the printing area, ink performance, texture of the substrate, human visual effects, overprinting requirements, manuscript type, and so on, which will affect the quality of printed matter from different degrees. Printing color sequence is different, the color effect of the printed matter is not unpleasant: 淼 淼 ∷ ∷ (5) 颍崾 嫜 嫜 嫜 咏 咏 咏 咏 咏 咏 咏 澹踔粱 澹踔粱 芗 芗 芗 芗 芗 芗 芗 盅 盅    Endangered     骰蛘呓 骰蛘呓 骰蛘呓 骰蛘呓 骰蛘呓 骰蛘呓 骰蛘呓 岷 ? ? ? ? ? 3 猓 猓 猓 猓 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 妗 妗 妗谩 ? ? ?          (18) 乇鹗 ∷ ∷ ∷ ∷ ∷ ∷ ∷ ∷ ∷ ∷ ∷ ∷ ∷ ∷ ∷ ∷ ∷ i3.  蛴 蛴 蛴 蛴 蛴 蛴 坝 新 新 新 新 新 榭鱿 榭鱿 妥 妥 妥The following aspects of the machine's printing color sequence arrangement can be considered as a priority factor:
First, the color shift in the product process design, should be based on the original color of the original to determine the 45-degree color version, and then determine the other color version of the cable angle. For example, if the main color is a bluish, green landscape manuscript, the cyan cable is set to 75 degrees, the yellow cable is set to 90 degrees, and the color sequence is determined as: black-magenta-cyan-yellow. Different printing color sequences will affect the color tone of the final print. For example, yellow, magenta, and blue colors will be printed in magenta-blue-yellow order, and will be slightly greenish: if the color order is cyan-magenta - Yellow, it will form a slight reddish. The following table shows the effect of changes in the printing sequence on the color rendering effect, excluding black (see table below). For the color deviation after overprinting, the platemaking pair can be corrected. At the same time, in order to emphasize the main colors of print screens, we must also take full advantage of the special effects of the color deviations produced by different printing sequences.
Second, the reverse printing phenomenon For four-color offset printing press, the wet-wet printing method, to make the latter color ink can be better transferred to the ink substrate of the previous color substrate, should follow the order of printing ink color sequence of ink to reduce the adhesion , otherwise it will produce reverse printing phenomenon. Unit-type lithographic printing press (such as domestic four-color machine, Heidelberg four-color machine, etc.), the ink on each color group is directly transferred to the surface of the paper at the time of printing, fast fixing low viscosity components and solvent Penetrates into the voids of the paper, leaving high-viscosity ingredients and synthetic grease enveloping the pigments in a gelled state on the surface of the paper. The viscosity of the ink in this process is the same as or slightly larger than the ink viscosity of the previous color ink. The stickiness does not produce an inverse overprint. However, the viscosity of the ink is also affected by many factors, such as the thickness of the printed ink layer, the printing speed, the temperature, the degree of ink emulsification, the amount of ink accessories added, etc., which are likely to break the original normal ink transfer relationship. In order to ensure the normal transfer of ink, following the printing sequence, the viscosity of the ink should be reduced in turn. For the satellite lithographic printing machine, since the ink of each color is transferred to the paper cylinder in sequence, the ink is transferred to the paper, and the color ink of the preceding color does not increase in viscosity. This type of printing machine has a structure that is insignificant. Insufficient, it is easy to produce reversed overprinting phenomenon. Therefore, for this type of printing machine, printing must be strictly followed in accordance with the principle of decreasing ink viscosity in printing color sequence, and between the front and back colors, the viscosity of the ink should have a large difference. .
In addition, when printing smooth, low-absorbency paper, consider the effect of ink stickiness on ink transfer. For ink viscosity control, generally speaking, the sheet-fed offset press has a speed of 7-13 at a speed of 5000-10000rph or so, a viscosity of 4-5 when the speed is around 20,000rph, and a viscosity of 3 when the speed of the web offset press is over 20,000rph. -5. The general order of the stickiness of the four-color inks has been tested to be black-cyan-magenta-yellow. Ink is a special fluid. Since the same kind of color printing inks use the same kind of linking material, the dispersion state of each color pigment in the linking material is extremely similar. In the case that the ink ink property is not changed, it can be roughly assumed that the ink viscosity increases with the increase of the ink viscosity ( In fact, the stickiness of the ink and the two different physical quantities of the sticking ink cannot be mistaken for two different expressions of the same property of the ink). Therefore, in actual printing, the printing color sequence is often determined according to the size of the ink viscosity. For example, the viscosity of the Shanghai Mudan Brand Four-color version 05 ink is: BK 118.82pa.SC 48.85pa.SM 47.71pa.S Y14.70pa.S
Third, when the overprinting ability determines the printing color sequence, the overprinting ability of the ink is an important consideration factor. Because the transfer of ink on the surface of the paper is much better than the transfer of ink on another color ink film layer. Although the area of ​​the overprint is the same, if the small area is printed first and then the large area is overprinted, the overprinted part is good for the small area because it is directly printed on the paper, and the whole ink color transfer is very good. For a large area, although there is a small area, The part is overprinted on another color (small area) ink film layer, but the effect on the large area as a whole is not large, so the effect is better. On the contrary, if a large area is first printed and a small area is printed first, even though the large-area ink is well transferred, for a small area, the ink is all overprinted on another color (large area) ink film layer, and the performance is poor, and the overall color is In terms of effect, it is inferior to the former. It can be seen from here that when the area of ​​the plate on the printing plate is large, especially the full plate, it is usually left behind or printed at the end. Some people used to test the color amount of the four-color machine in the order of color and color inversion. The results are shown in the following table. When the four-color machine is wet and wet, the amount of color of the inverted color sequence is better than that of the color sequence. The amount of overlapping color is reduced by 11.7, and the amount of overlapping colors of the secondary and tertiary colors is lower, which objectively affects the saturation of the color, particularly in the midtones and shadows, and the color rendering effect is poor and the colors are not abundant.
Fourth, the transparency of the ink The ideal ink, which itself should be absolutely transparent, otherwise, in the multi-color printing, the light can not reach the underlying ink layer through the upper ink layer, then the overlay can not show the effect of mixing . The hue, saturation, and lightness of the composite color are severely affected. From the perspective of the transparency of the four-color inks used today, the black ink is the worst and the clear yellow ink is the best. The magenta and the blue inks depend on the pigments and binders used. The general situation is the ratio of the blue ink to the red ink. Poor ink transparency. When printing, inks with poor transparency are generally printed first, and inks with good transparency have to be printed. Of course, the four-color machine printing sequence usually used now puts the yellow ink on the last color printing. Besides the reason that the yellow ink has high transparency, there are also the following reasons:
1. Widely use the low-absorption coated paper and the practical needs of the four-color machine for rapid printing, which overcomes the wet overprint problem that is caused by the large area of ​​the yellow printing.
2. It avoids the tendency of the blue and black ink to have a bronze luster after the ink is dry. There is no longer a feeling of color impure.
3. Avoid excessive expansion of yellow dot.
V. Overprinting Problems In the design of certain print processes, overprinting problems may be a determinant factor in multicolor printing presses. This factor is mainly for the dimensional stability of the paper. For example, when the middle of a picture is an inverted white text with a black box, and the surrounding is a full-color version, the black bars are just in contact with the full version. At this time, if the paper is very stretched during printing, it may cause overprinting difficulties. Therefore, when arranging the printing color sequence, the black frame should be printed first, and then the printing ink should be printed. This is due to the smaller paper stretch caused by the first printing of the black frame, and it is easier to print the full version over black.
Sixth, double shadow situation Under normal circumstances, the first color of four-color machine printing color sequence is often black. However, some prints, such as product catalogs, often have most of the textual descriptions in the black version. If the substrate is a poor-quality coated paper during printing, the retractable width of each sheet is likely to be different, and the first color of black ink will be partially transferred to different positions on the surface of the second color blanket cylinder. There is a danger of double shadows. Double images can make the text blurry and affect product quality. In this sub-case, black should not be placed in the first color, but it should be more appropriate to put it in tricolor or final printing.
VII. Proofing and proofing is not only the final process of plate making, but also the “first mover” of printing. Proofing plays a role in the quality of plate making and also provides a reliable basis for the printing process. At present, the platform-type monochrome proofer widely used in proofing is very different from the printing machine in its machine structure, printing method, printing pressure, and operating speed. Therefore, it is difficult to make the quality of printed matter exactly the same as proofs. But as long as we can properly handle the relationship between the proofing and printing process, especially the printing sequence, we can completely reduce the gap between print quality and proofs. Monochromator printing and four-color printing, the print quality judgment process is consistent. For a monochrome machine, the printing effect can be judged according to the single pattern or the overlapping proofs for each color printed, and the printing method of the monochrome machine is the same as the printing method of the proofer, which belongs to the wet-dry printing method. Therefore, as long as the same print sequence is used, the print quality is easier to control. The four-color printing adopts the wet and wet printing method, and the print is formed once, so the printing effect is far from the proofs. In order to make the proofing more reliable for four-color machine printing and narrow the gap between proofing and printing, the following aspects should be paid attention to when proofing: 1. The color sequence of proofing is exactly the same as the color sequence of printing. 2. Use four-color proofer for proofing. 3. Use the same printing plate, paper, and ink as the printing.
VIII. Printing, Printing, Printing, Printing, Printing, Printing, Printing, Printing, and Printing Silver printing is generally performed in the field, with thick ink layers and high process requirements. They are usually printed at the end of the printing.
In summary, there are many factors affecting the printing sequence of four-color machines, and even some factors are in conflict with each other. Therefore, we can only take a compromise when determining the printing color sequence.
At present, many printing plants generally use the four-color printing sequence of black-cyan-magenta-yellow or black-magenta-cyan-yellow. The two kinds of printing color sequences are determined after combining many factors. They are the two basic color sequences of a four-color machine. Among them, the black-cyan-magenta-yellow color printing sequence is used more often. Called the standard color sequence of a four-color machine. However, this is not the only one. It should be determined according to the specific circumstances when printing. The new situation cannot be applied rigidly. Once the printing color sequence is determined, it should not be arbitrarily changed during printing so as not to affect the stability of the color balance reproduction of the screen.