Color printing is usually performed by using yellow, magenta, cyan, and black four-color plates and superimposing printing 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.
In fact, many factors affect the color of printed materials, such as the printing area, ink performance, the texture of the substrate, the visual effects of people, the requirements for overprinting, the type of originals, and so on, all affect the quality of prints to varying degrees. Different printing color sequence, the color effect of the print is not... For the arrangement of four-color machine printing color sequence, the following aspects 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, which does not include black.
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. (To be continued)
Discussion on Color Printing Sequence of Four Color Machines
September 18 21:00:54, 2024
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