What are the conditions for color reproduction of printed matter

1. Substrate

The substrate is the basis for the bright color of the printed matter. According to the principle of the color of the printed matter, in addition to the spatial mixing of the various color dots to form people's visual colors, the color of the surface of the substrate without the printed dots. Actually also participated in this spatial mixing. Therefore, if the whiteness and gloss of the substrate are high, the brightness of the color can be improved. On the contrary, the gray substrate is like adding a small amount of black to each color ink, thus showing a dark color. In addition, the absorbency of the substrate will affect the color saturation. For the substrates with large absorption, the blots cannot form a sufficiently plump ink layer on the surface, and the binding material excessively penetrates into the substrates to dry the blots. Paper with large pores will cause some pigments to penetrate into the paper together with the binder, thus reducing the color saturation and affecting the vividness of the color.

2. Ink

The color characteristics of tri-primary inks directly affect the degree of vividness of printed products. Different types of tri-primary inks have different color deviation, grayscale and efficiency, so the degree of vividness of ink colors is also different. Use brightly colored inks of the same manufacturer and model. In addition, in the printing process, try not to add too much auxiliary agent to the original ink, so that the ink emulsification or saturation is reduced. When changing colors, if the previous color ink is not cleaned, it will cause the color shift of the latter color ink to increase, and the grayscale will increase, which will affect the color reproduction of the printed matter.

3. Plates

The plates used in water offset printing are mostly PS plates. The PS version is based on the polymer photosensitive layer as the graphics and text, and the printed graphics and text are slightly higher than the blank part. The hydrophilic part is an aluminum oxide film. The waterless offset printing uses a unique pre-coated photosensitive offset printing plate. The blank part is a kind of silicone that repels ink. The part with the image is a layer of slightly sunken polymer, and the surface of the plate is resistant to oxidation. The printing quality of the PS version directly affects the quality of the printed matter.

4. Ink layer thickness

In the actual printing process, the thickness of the ink layer affects the color reproduction. The thickness of the ink layer is thin, and the picture presented is dark and flat; the thickness of the ink layer is thick, the dot expansion value increases, the dark tone is easy to blur, and the picture presented is dull and unclear. Therefore, the thickness of the ink layer must take into account the tone reproduction. Generally speaking, under the premise of quality assurance of printing plate, the thickness of ink layer should be adjusted according to the provided sample. For monochrome machines, pay special attention to the first color of the sample. The thickness of the first color ink layer directly affects the color reproduction of the entire screen.

5. Overprint rate

Overprint rate indicates the ratio of the amount of ink printed by the next color to the previous color and the amount of ink printed by the latter color directly on the paper. This ratio is always less than 100%, which means that the amount of ink printed by the latter color on the previous color must be less than the amount of ink printed directly on the paper by the latter color.

Overprint rate will affect the color saturation of secondary colors. The higher the overprint rate, the greater the saturation of the color, and the brighter the color. For monochromatic machines, the overprint rate is generally higher, while for multi-color machines, not only is the overprint rate low, but it can also cause the mixing of front and back colors.

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