In gravure printing, spot colors are used more often. Spot color inks are generally formulated by ink factories according to certain standards. Even so, the spot color ink will produce a difference in printing hue and color swatch when it is printed on the machine. Here, take the red ink as an example to introduce the preparation techniques of spot color ink.
For a big red, in the CIEL * a * b * color space, L * = 40.80, a * = 59.80, b * = 42.11. From this, we generally know its position in the color space. The basic ink that needs to be selected for the preparation of this color is mainly red, and the color ink is dark red, gold red, black and diluent.
In the comparative measurement, when one of ΔL *, Δa *, and Δb * is close to Z in the tristimulus value or greater than or equal to Z, the color difference is more obvious when the color is observed with the naked eye. Therefore, L * is a key chromaticity index, which determines the main position of the color in the CIEL * a * b * color space.
1. If ΔL *> 0, and the value of ΔL * is large, it means that the color is bright, and the ink layer looks thin from the printing point of view; from the composition of the ink, the proportion of dark red ink in the ink is too small. In this regard, there are two ways to adjust, one is to increase the thickness of the ink layer by increasing the printing viscosity of the ink and reducing the printing speed; the other is to increase the proportion of dark red ink, then a very small amount of purple ink or The black ink can be adjusted, and the yellow phase can be adjusted with gold and red ink.
2. If ΔL * <0 is large, it means that the color is too dark with too many ingredients. And the absolute value of ΔL * and the brightness of the color in the ink will have some influence on the saturation of the color. Therefore, while adjusting the brightness, you can add a little gold and red ink for fine adjustment, but it will not cause too much impact on the red and yellow cabinets in the color. Of course, you cannot adjust the hue alone. When adjusting the yellow phase in red ink, you can use orange ink or gold-red ink instead of yellow ink for fine-tuning.
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