Analysis of Color Matching of Gravure Printing Inks (I)

Color matching principle

Each color has three characteristics of hue, lightness, and saturation. Therefore, the above three factors must be considered in the color matching process. Although black is theoretically the complete absorption of light, black ink still has a gloss. The ink is: "Pigment (toner) and resin connection material submerged." Pigment particles surrounded by a layer of nearly transparent resin oil, the light has refraction and reflection. So we can feel black ink printed on the substrate, still has a certain degree of gloss. Pigments often account for 8% to 5% of the ink composition. Its amount determines the concentration of the ink and has a great influence on the ink. Such as: the relative density of ink, transparency, heat resistance, light resistance and resistance to chemicals. In the ink color matching process, the ink used should be determined according to the actual printing process, the ink layer thickness, the printing substrate and other conditions. When selecting the ink, the gloss, hue, tinting strength, hiding power and the like of the ink itself must be considered. Gloss - Gloss can be measured either with the instrument or with the naked eye. It is usually observed with the naked eye only during the color matching process. Of course, for special situations, it must be measured with instruments, chromatographs, etc. Gloss is actually the extent of the ability of ink printing to reflect light in the same direction after being illuminated by light. Its direct influence on the appearance of printing is a very important indicator. At the same time, when selecting the ink, it is necessary to distinguish whether the ink itself is a bright, semi-glossy or matte type ink, and it should also be considered whether the ink of the same type is used. If the printing ink is printed in India (chlorinated polypropylene resin type) or table printing (polyamide resin) ink, it must be prepared for the same ink to avoid mixing errors and cause unnecessary losses. Hue - the basic characteristics of color, due to the quality of the difference, when color matching, first of all to consider whether the hue is consistent, and its detection method is usually observed through the scraping comparison.

The specific way to observe hue is:

1 Regarding the entire glass viewing platform, take the standard sample and the color pattern at a distance of 1-2 em. 2 Take a scraping paper to flatten the glass stand, and then take the color ink. Use a glass tamper to scrape and compare the results.

There are two important factors in the comparison of the color palette results:

1 hiding power - the degree of ink cover the background color, the better the hiding power, the worse the transparency. The level of transparency affects the efficiency of ink trapping and the extent to which it is affected by the printed substrate. In general dark inks have stronger hiding power than light colors. Such as the blue light yellow is better, and the ink hiding power is good, but also has a close relationship with the ink itself. Such as the thickness factor, under normal conditions, the hiding power of white ink is related to the thickness of titanium dioxide particles. The coarse particles have poor hiding power. The printing is easy to agglomerate; the particles are fine, the hiding power is good, the surface is uniform, smooth and delicate. The white ink generally requires a diameter of no more than 15p, m, and other colors of ink cannot exceed 12g, m.

2 coloring power - a method that represents the level of ink concentration. The determination is based on a certain amount of color ink, and then a certain amount of standard white ink is added. After mixing and comparing with the standard sample, the strength of coloring reflects the degree of color mixing of the ink. Through the color identification (scratch paper coloring experiment) can be compared, the ink sample and standard sample gloss, hue, hiding power of the three differences. The specific method is as follows: In the upper left corner of the fixed paper, the standard ink is placed, and the color ink is placed in the upper right corner. Using a spatula at a nearly vertical angle to the scraping paper, lightly force the standard and color matching inks that need to be compared. After the ink surface is dry, under a certain light source, determine the difference in gloss between the two and observe the appearance of the entire color. Normally black and color inks use white scraping paper, while white ink uses black scraping paper

When observing color samples, it is best to compare them under indirect light sources during the daytime, and not to be exposed to direct sunlight. It is recommended to use at night observation: “The price of fluorescent tubes and color temperature is 5000±200*K. Self-made hybrid light sources can also be used. The density of inks selected for 2 blue fluorescent tubes and 3 6500K400W daylight fruits is not high enough, no matter how they are blended. Nor can you reach the standard color concentration.

4 When it is necessary to add black ink, special attention should be paid to the accuracy of the added weight and weight. In all inks, the hiding power of white ink is particularly strong. Adding too much will not only dilute the color but will also prevent the substrate from reflecting. However, for the printing uneven substrate such as nylon cloth, cardboard, in order to ensure the appearance of the print, it is best to print a white layer as the background color. Due to the strong coloring power of black ink, adding too much ink to the ink requires adding a considerable amount of other color ink to adjust the color to cause waste. Therefore, special attention is required.

5 When producing light color inks, it should be judged from the degree of light transmission of the ink film, which should be added to the number of white ink or ink adjustment (dilute the economy) to color. It is absolutely not allowed to use solvents (dilutions) for light colors. Excessive solvent addition will not only affect the printing performance, but will also destroy the ink structure and cause separation of the pigment from the resin oil. Precipitation or greatly reduces the gloss and brightness of the ink.

(to be continued)