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In the printing process, no matter what kind of printing, whether it is multi-color or monochrome printing, the first problem encountered before printing is the ink color adjustment to adapt it to the needs of the printed product. Therefore, the ink color is often Selection and deployment. No matter how bright the ink is, if the operator does not understand some ink performance and color matching knowledge, the mixed ink can not achieve a satisfactory appearance and due quality level. For this reason, this article wants to introduce some color adjustment methods for reference.
First, the simple principle of color matching
Any color is represented by the three characteristics of hue, lightness and saturation, so the above three factors must be considered in the color matching process. Although black is theoretically a complete absorption of light, black ink still has gloss. The ink is grinded by pigment (toner) and resin binder. The particles of pigment are surrounded by a layer of nearly transparent resin oil. This layer of resin oil has the effect of refracting and reflecting light, so we can feel the black ink printing It still has a certain gloss on the substrate. In the ink color matching process, the ink used should be determined according to the actual printing process, ink layer thickness, printing substrate and other conditions. When choosing an ink, consider the gloss, hue, tinting power, and hiding power of the ink itself.
1. Gloss Gloss can be measured with an instrument or judged with the naked eye. Usually, it is only observed with the naked eye during the color matching process. Gloss actually refers to the degree of the ability of an ink printed sample to reflect light in the same direction after being illuminated by light. It directly affects the appearance of printed matter and is a very important indicator. At the same time, when selecting the ink, it is necessary to distinguish whether the ink itself is bright, semi-gloss or matte type ink to avoid mixing errors.
2. Hue is the basic characteristic of color. It is used to distinguish between qualities. When matching colors, we must first consider whether the hue is consistent. The detection method is usually to scrape the color through scraping paper or simulate printing. Observe and compare.
3. The hiding power is the degree to which the ink covers its background color. The better the hiding power, the worse its transparency. The level of transparency affects the efficiency of ink chromatism and the degree of influence of the printing substrate.
4. Coloring power is a method of indicating the level of ink concentration. It is determined by adding a certain amount of ink and then adding a certain amount of standard white ink to dilute and mix, and then compare it with the standard sample. The difference in color strength reflects the degree of color mixing of the ink and affects the thickness of the printed ink film.
The difference between the ink sample and the standard sample in the three aspects of gloss, hue, and hiding power can be compared through the color identification scratch paper (Drowdown). Specific method: put the standard ink in the upper left corner of the identification paper and the color matching ink in the upper right corner. The distance between the two is about one centimeter. Force to quickly expand the thick part.
After the ink surface is dry, you can observe the hue of the ink in the thin part, identify the hiding power and transparency of the ink in the black belt, judge the difference in gloss between the two in the thick part, and observe the appearance of the entire color. Usually black and color inks use white scraped color paper, while white inks use black scraped color paper.
2. Problems that should be paid attention to when matching ink
1. Observe the color sample carefully, pay special attention to the substrate to be printed, and choose the ink from the roughness and smoothness of the substrate and the degree of reflection. For example, the ink is printed on a smooth, highly reflective aluminum plate or a can, and choosing a highly transparent ink will help greatly enhance the metallic luster of the ink.
2. When choosing the ink required for color matching, try to avoid mixing too much ink, and try to use inks that are close to the standard color and made of a single pigment. The more color inks are used for color matching, and the farther away from the standard color, the worse the brightness, and the higher the matte color of the mixed color. It is impossible to modulate the primary color by color matching.
3. Pay special attention to the coloring power of the ink. If the selected ink density is not high enough, no matter how it is blended, the standard color density cannot be achieved.
4. When it is necessary to add white and black ink, special attention should be paid to the amount added and the accuracy of weighing. Among all inks, the hiding power of white ink is extremely strong. Too much addition will not only dilute the color, but also prevent the reflective degree of the substrate. However, for printing uneven substrates such as nylon cloth and cardboard, in order to ensure the appearance of the printed product, it is best to print a layer of white as the background color. Due to the strong coloring power of black ink, if you add too much, you need to add a lot of other color inks to adjust the color, causing waste, so special attention is required.
5. When making light-colored ink, it should be judged from the light transmission degree of the ink film how much white ink or adjusting oil (diluent) should be added for color mixing. Never use solvents (dilution water) to dilute the color. Adding too much solvent will not only affect the printing performance, but also destroy the ink structure, causing the pigment and resin oil to separate, causing precipitation or greatly reducing the ink gloss.
6. Method for improving gloss of printing ink film
(1) Add proper amount of ink in the allowable range of color density.
(2) Apply a layer of varnish or ink to the surface of the printed ink film.
(3) Increase the transparency of the ink, such as the use of high-transparency high-ink ink or the addition of an appropriate amount of ink, to increase the gloss by the reflection of the smooth, highly reflective substrate.
(4) Prevent the adsorption of the substrate surface, and reasonably improve the smoothness of the printed surface of the substrate.
(5) Pay attention to the temperature and humidity of the printing environment. In the case of high humidity and low temperature, when plastic gravure printing is performed, due to the rapid evaporation of the solvent (usually the ink film surface is dried within 1 minute), the heat around the ink film is absorbed and the water vapor in the air is rapidly condensed. Fog is formed on the surface of the printed ink film, causing the ink layer to lose luster. During the rainy season, special attention should be paid to controlling the temperature and humidity of the printing environment to ensure good printing results.
7. Fluorescent inks cannot be mixed with a large number of non-fluorescent inks, otherwise the fluorescent effect of the ink will be lost.
Three, special color production
1. Gold and silver ink production: use the ink adjustment oil to add the appropriate amount of gold powder and silver powder and stir evenly. It is necessary to pay attention to the selection of gold and silver powder with appropriate fineness. At the same time, the ink adjustment oil suitable for the printing substrate should also be selected. Re-formulation to prevent the ink from settling and delamination due to the long standing time. Gold ink can also be mixed with silver powder, transparent yellow and ink.
2. Pearlescent ink: Pearlescent pigment is mixed evenly with a high proportion of high transparency ink or ink blending oil. The hiding power of the ink is strong, and the pearlescent effect may be lost.
3. Luminous ink: The ink has the effect of radiating light after a certain period of time after absorbing light energy, so it can often emit light at night, so it is called luminous ink or phosphorescent ink. Generally, the luminous pigment is dispersed in the ink with high transparency, and it can be stirred evenly.
The above inks cannot be ground. The grinding of gold ink and silver ink will damage the grinding equipment. The grinding of pearlescent and luminous ink will destroy the surface or crystal structure and lose the expected effect.
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