What is Offset Lithography?

"Lithographic" and "offset printing" mean the same. This printing method uses a roller-type gel impression to transfer the ink adhered to the paper surface to the paper surface. Because the rubber surface is flat and there are no recessed patterns, the patterns and patterns on the printed paper surface are also flat, there is no three-dimensional effect, and the security is poor. Offset printing requires less ink, and the manufacturing cost of the mold is lower than that of gravure.

Offset printing

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"Lithographic" and "offset printing" mean the same. This printing method uses a roller-type gel impression to transfer the ink adhered to the paper surface to the paper surface. Because the rubber surface is flat and there are no recessed patterns, the patterns and patterns on the printed paper surface are also flat, there is no three-dimensional effect, and the security is poor. Offset printing requires less ink, and the manufacturing cost of the mold is lower than that of gravure.

Chinese name

Offset printing

Aka

Lithography

Technology Type

Printing Technology

Technology used in

The third set of RMB printing

In the third set of RMB, the 1960 version of the "Red Corner" and all banknotes above one yuan are used on the front and back

Generally, under the condition of wet pressure, the color of the ink printed first has the advantage. For example, if the green is printed first and then the magenta is printed, the overprint color will be greenish; if the magenta is printed first and then green, the overprint color will be reddish. In the case of wet pressing, the color of the post-printed ink is dominant. From an optical point of view, CMYK color sequence should be used for lithographic printing.

In general, for warm-tone prints dominated by figure painting, the color sequence should be black, cyan, magenta, and yellow;

The prints based on cold tones such as landscape paintings and snow scenes should be printed in black, magenta, cyan, and yellow;

The color sequence of the two-color machine is cyan + magenta, black + yellow, and the color sequence of the monochrome machine is cyan, magenta, yellow, black, or black, cyan, magenta, and yellow (generally, when the black version is a skeleton version, Black on the front);

In order to facilitate overprinting, the color sequence should be arranged according to the thickness of the ink layer from small to large, such as black ink 0.8umcyan ink 0.9ummagenta ink 1.0umyellow ink 1.1um;

Arrange the printing color sequence according to the order of ink viscosity, such as black ink 1188Pa.scyan ink 488Pa.smagenta ink 477Pa.syellow ink 147Pa.s. The viscosity of the ink is adjusted in advance;

The ink with a small coverage area should be printed first, and the dark ink should be printed first (due to its high viscosity and large hiding power, to avoid sticky dirt on the back);

When printing with UV inks, because of the different degree of UV photons absorption, the curing speed varies, so the color sequence should be black-cyan-yellow-magenta when printing.

a. Overprinting the color of the color block should try to avoid using too small percentage of dots, such as flat dots below 20%. Because the color block composed of small dots is easy to cause partial sun exposure due to insufficient air absorption or small particles adhered to the negative film and the glass of the plate exposure machine when printing, it is easy to cause excessive moisture and rubber blankets when printing. Dirty or worn plates can cause plate loss. The above two reasons will cause uneven ink color. As for the dots below 5%, the ordinary offset printing process is difficult to restore, and it should be avoided.

b. At the same time, try to avoid using halftone dots with too large percentages, such as flat dots with more than 80%. Because the color blocks composed of large dots are slightly insufficient in printing, or the blankets are dirty, it is easy to paste. As for more than 95% of outlets should be avoided.

c. To avoid overprinting of color blocks on the ground or high-dot dots with too many color numbers, it is easy to cause the back surface to be dirty due to the thick ink layer.

d. When using spot color printing technology, try not to choose color blocks that need to be mixed with too many basic color inks. Mixing too many inks will greatly increase the difficulty of blending the inks, which will increase the blending time and make it difficult to blend colors of similar hue.

e. When using spot color to print a large area of a certain color, try to avoid using that color to print small anti-white text and lines at the same time. Because printing a large area of the field tends to increase the thickness of the ink layer, the thicker the ink layer is, the easier it is to spread, but it will lead to small anti-white text and line paste.

f. For the text, when printing the small white characters in the middle of the field, customers should be advised to use the bold type.

g. When printing full plates on the field, you can use the printing plate left over from the last printing and stop the water supply instead of special plate making. However, because the photosensitivity of the graphic part on the PS version and the alumina on the blank part have a slight difference in the adsorption capacity of the ink, it is best to use a completely air-folded one when the full-print printing color is strong (such as dark blue) Printing plate.