The difference between the spot color and the four-color overprint color block

The inks prepared by the spot color printing are obtained according to the mixing principle of the color reducing method, and the color brightness is low and the saturation is high. The spot color of the ink color is usually printed in the field, and the amount of ink should be appropriately increased. When the thickness of the ink layer of the plate is large, the change of the thickness of the ink layer is less sensitive to the color change, so it is easier to obtain a uniform and thick ink. Printing effect.

The color blocks superimposed by the four-color printing process, because the various colors constituting the color block are mostly composed of a certain proportion of dots, when printing the dots, the thickness of the ink layer must be strictly controlled, which is easy to change due to the thickness of the ink layer and printing. The change in process conditions causes a change in color intensity, a change in the degree of dot gain, resulting in a color change; and because any change in the color constituting the color block causes a change in the color of the color block, resulting in an uneven color of the ink. It will be multiplied, so the color blocks superimposed by the four-color printing process are not easy to obtain the uniform effect of the ink color. If the color of the color block cannot be overprinted by the multicolor machine at one time, it is easy to cause color shift due to the color of the semi-finished product being difficult to control. In addition, the four-color printing obtains the combined effect of the subtractive color mixing and the additive color mixing of the dots, and the color block has a high brightness and a low saturation. For the light color block, the four-color printing process is adopted, and since the ink coverage on the paper is low, the ink color is dull and lacks a thick feeling. Due to the angle of the cable, it is inevitable that people will feel the existence of the pattern.

2. From the perspective of improving product quality, what kind of products are suitable for spot color printing?

When printing a large area of ​​light-colored uniform color blocks, it is common to add a thinner to the original ink to adjust the spot color ink, and then perform the solid printing, so that the ink layer is thicker, and it is easier to obtain a uniform color and a thick effect. If a four-color printing process is used, a low number of flat screen dots must be used. However, the low number of flat net dots are likely to cause small dots at individual parts due to slight sand or a slight exhaustion during printing, resulting in uneven ink color. When printing, it is easy to cause excessive ink transfer at small dots due to excessive water supply on the plate, accumulation of paper powder on the printing plate and blanket, and low paper smoothness, resulting in lighter ink and uneven ink. For dark large-area color blocks, a four-color printing process may be used, which may require overprinting of high-numbered dots of several colors, and the ink layer is too thick to be smeared on the back side. With the spot color printing process, only one color is printed, and the back side is not easy to be dirty. Using a four-color printing process, some parts of the graphic may be synthesized by several colors. With the spot color printing process, only one color is printed in the corresponding part, which avoids the possibility of overprinting error.

3. What problems should be considered in the arrangement of color sequence in monochrome machine?

(l) The principle of facilitating registration. Since the paper generally elongates due to water absorption during the printing process, it also elongates under the printing pressure and the stretching tension, especially when printing the first color, which causes the first color to be the most difficult and the back printing color sleeve. Precise, so the first color should be printed with a color that is not required to be high.

(2) The principle of facilitating color change. The light ink is printed first, and the dark ink is printed later, so that it is easier to clean the inking device.

(3) The principle of importance of color. Putting important colors on the back prints, it is more color-developing, and it is easier to grasp the gray balance. Prints such as characters with warm colors, such as characters, are better for red and yellow after printing; prints with cool colors, such as glaciers, snow, landscapes, etc., are printed with cyan.

(4) The principle of small and large inking area. The color of the ink area is printed first, and the color of the ink area is printed first, so as to prevent the first color from being scratched when printing again. When printing large areas on the ground, if the paper is thin, paper curl may occur; in order to prevent back dirt, you may need to dust. These reasons require a large area of ​​solid color to be printed.

(5) The transparency of the ink determines the color sequence. Generally, the one with the least transparency is printed first, and the transparency is good.

(6) The degree of brightness of the overprinted color determines the color order. Generally, the dark color is printed first, and the bright color is printed later.

(7) If there is a flat net and a solid color on the printed matter, the flat net is printed first, and the solid color is printed on the back. The overprinted ink is more uniform.