Experience in the adjustment of ink color during the printing process
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In the printing process, no matter how it is printed, whether it is multi-color or monochrome printing, the primary problem encountered before printing is the color matching of the ink to adapt to the needs of the printed product. Therefore, the color of the ink is often required. Selection and deployment. No matter how bright the ink, if the operator does not understand some ink properties and color matching knowledge, the mixed ink can not achieve a satisfactory appearance and the level of quality that should be. To this end, this article would like to introduce some coloring methods for reference.
First, the principle of color matching
Any color is represented by three characteristics of hue, lightness and saturation, so 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 luster. The ink is made of pigment (toner) and resin binder. The pigment particles are surrounded by a layer of nearly transparent resin oil. This layer of resin oil has a refractive and reflective effect on light, so we can feel black ink printing. There is still a certain gloss on the substrate. In the ink color matching process, the ink used is determined according to the actual printing process, the thickness of the ink layer, the substrate to be printed, and the like. When selecting inks, consider the gloss, hue, tinting strength, and hiding power of the ink itself.
1. luster
Gloss can be measured either by instrument or by the naked eye, usually by visual inspection during color matching. Gloss actually refers to the extent to which an ink print sample reflects 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 a bright, semi-light or matte ink to avoid mixing errors.
2. Hue is the basic feature of color. It is used for the difference of quality. When matching color, it is necessary to first consider whether the hue is consistent. The detection method is usually to scratch the color by scraping paper or simulate printing, and the standard and sample are made by human eyes. Observe and compare.
3. The hiding power is the extent to which the ink covers its background. The better the hiding power, the worse the transparency, and the transparency affects the efficiency of ink coloring and the degree of influence on the printed substrate.
4. The tinting strength is a method of indicating the concentration of the ink. The measurement is performed by diluting and mixing a certain amount of ink and adding a certain amount of standard white ink, and then comparing with the standard sample. The intensity of the difference color reflects the degree of color mixing of the ink and affects the thickness of the printed ink film.
Drowdown can be used to compare the difference between gloss and hue and opacity of ink samples and standard samples by color identification. Specific method: put the standard ink in the upper left corner of the identification paper, and put the color ink in the upper right corner. The distance between the two is about one centimeter. Use a scraper to flatten the thin part and the angle of inclination at a nearly vertical angle with the scraping paper. The force quickly spreads over the thick part. After the surface of the ink is dried, the hue of the ink can be observed in a thin portion, the hiding power and transparency of the ink are identified in the black strip portion, and the difference in gloss between the two is judged in the thick portion and the appearance of the entire color is observed. Black and color inks are usually white-scratched paper, while white inks are black-scratched paper.
Second, the problem should be paid attention to when the ink color matching
1. Carefully observe the color samples, pay special attention to the substrate to be printed, and select the ink from the roughness and smoothness of the substrate. For example, ink printing on a smooth, highly reflective aluminum sheet or can, and selecting a highly transparent ink will help to greatly enhance the metallic luster of the ink.
2. When choosing the inks required for color matching, avoid mixing too much ink as much as possible, and try to use inks that are close to standard colors and made from a single pigment. The more colors used in color matching, the farther away from the standard colors, the worse the brightness, and the higher the matte level of the mixed colors, it is impossible to modulate the primary colors by matching colors.
3. Pay special attention to ink tinting strength. If the selected ink concentration is not high enough, the standard color density cannot be achieved no matter how it is blended.
4. When it is necessary to add white and black ink, the component added and the accuracy of weighing should be specially injected. Among all the inks, the white ink has a strong hiding power, and adding too much will not only dilute the color, but also prevent the substrate from being reflected. However, in the case of printing irregularities such as nylon cloth or cardboard, in order to ensure the appearance of the printed product, it is preferable to print a layer of white as a ground color. Since the black ink has a strong coloring power, if it is added too much, it is necessary to add a considerable amount of other color inks to adjust the color, resulting in waste, so special attention is required.
5. When making a light-colored ink, it should be judged from the degree of light transmission of the ink film to determine how much white ink or varnish (dilution agent) should be added for coloring. Solvents (dilution water) are never allowed to dilute colors. Too much solvent addition will not only affect the printing performance, but also destroy the ink structure, causing the pigment to separate from the resin oil, causing precipitation or greatly reducing the gloss of the ink.
6. Method for improving printing ink film gloss
(1) Add an appropriate amount of varnish to the allowable range of color density.
(2) Apply a layer of varnish or varnish to the surface of the printing ink film.
(3) Increasing the transparency of the ink, such as using a high-transparency high-ink ink or adding an appropriate amount of varnish, and using a smooth, reflective strong substrate to increase the gloss.
(4) Prevent the adsorption of the surface of the substrate 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 the gravure printing is performed, the solvent volatilizes quickly (usually the surface of the ink film is dried in 1 minute), and the heat around the ink film is absorbed to cause the water vapor in the air to condense rapidly. The surface of the printing ink film is fogged, causing the ink layer to lose its luster. In 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 ink fluorescence will be lost.
Third, special color production
1. Gold and silver ink production: use tempered oil to add appropriate amount of gold powder and silver powder to stir evenly. Pay attention to selecting the fine powder and silver powder, and also choose the varnish suitable for the printing substrate, and should be in printing. Reconstituted to prevent precipitation and delamination of the ink due to excessive residence time. Gold ink can also be made by mixing silver powder, transparent yellow and varnish.
2. Pearlescent ink: The pearlescent pigment is mixed with a suitable proportion of highly transparent ink or varnish to form a uniform. The ink has a strong hiding power and is likely to lose the pearlescent effect.
3. Luminous ink: The ink has the effect of absorbing light energy for a certain period of time, so it can often emit light at night, so it is called luminous ink or phosphorescent ink. The luminescent pigment is usually dispersed in a highly viscous varnish and stirred well.
All the above inks can't be ground. The grinding of gold ink and silver ink will damage the grinding equipment. The polishing of pearlescent and luminous ink will destroy the surface or crystal structure and lose the desired effect.