Specific application of the hottest printing chrom

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The specific application of printing chromatics

this paper will elaborate the application of chromatics in printing from three aspects: the production of printing chromatography, the measurement of printing hue, and the allocation of spot color ink

1 making printing chromatography with chromatics

in the whole process of color reproduction, it has gone through three processes: color analysis, color transmission and color combination. The correctness of color change control in each process is directly related to the final quality of printed matter, so a color standard, namely printing chromatography, is needed to regulate various hues in the printing process. Printing chromatography is to use the three primary colors of yellow, magenta, cyan and black to mix and stack them according to different proportions or dot percentages to form a Atlas of various color patterns for people to check in design, original copy, ink allocation, etc

the four-color chromatography is composed of yellow, magenta, cyan and black inks, overprinted and stacked with different dot area percentages (generally only eleven dot levels of 0, 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100%, or equally divided dot levels of 5%), and arranged in a certain order. It plays an important reference and guiding role in electronic color separation, proofing and printing processes. The spot color in printing is a kind of mixed color ink, which has no direct relationship with y, m, C and K. therefore, a set of standard primary color inks is first defined, and various color samples are generated according to different mixing ratios. Each color sample is marked with a scalar indicating the mixing ratio of primary colors, so that people can use the three primary color inks to mix the spot colors of various colors. This is spot color chromatography

at present, Pantone color matching chromatography of American CAITONG company is widely used internationally. However, printing chromatography uses pigments to express colors, and its production is usually affected by many factors such as ink, paper, printing process and equipment. Therefore, printing units should make their own special printing chromatography according to the raw materials, production process, equipment conditions, etc. used by the factory

2 measurement of color and color difference using chromatics

color measurement in color printing can be roughly divided into three methods: comparative visual measurement, density measurement and colorimetry measurement

in the printing process, the contrast visual method is used to measure the color, which mainly depends on the experienced operator to evaluate the color of the original, signal bar and printing sheet with the reference to the standard color rate by the contrast visual method. Due to the influence of the observer's own physiological and psychological factors, the accuracy of the comparative visual method is relatively poor. However, because it does not need to be equipped with fine measuring instruments, it is still widely used in general print reproduction work

density measurement method is a method that uses optical density value to measure the order and color value of color. In the process of color printing, the density value can well reflect the proportional relationship and superposition performance of three primary color inks, and the detection equipment is simple, so it is widely used. However, using optical density as a means of monitoring and measuring the printing process, we can only obtain the amount of each monochrome ink from the control strip, and cannot directly obtain the information of color error from the image, so it is difficult to communicate with printing customers, and it is also inconvenient to accurately control the color reproduction, so density measurement is only an indirect color measurement method

colorimetric measurement method is a color measurement method based on the principle of colorimetry, which takes the color of important parts of the printed image as the monitoring point, directly measures the three stimulus values of the color, obtains the highly intensive technology of new color materials, and develops the chromaticity information of different colors of the sun and the moon. This method can accurately express the color difference between the standard sample and the tested sample and the required proximity, without the need to increase the service life and reliability of the whole machine and add a check mark or control strip. However, it has not been popularized at present, mainly because of the high price of the instrument and the high requirements of color theory for users. As a large cigarette label printing enterprise, most of our products are related to spot color printing. Due to the good use of chromaticity measurement to control color difference, few customers have complained about the color in recent years

in color printing reproduction, we should not only understand the three attributes of color, but also understand the differences between colors, so as to compare and distinguish colors, which is color difference. The unit of color difference is NBS, which is the abbreviation of American National Bureau of standards. At present, the common color measurement standard in the world is CIE1976LAB uniform color space, which was proposed by Canadian weizeski at the 18th CIE conference in 1975. Where l represents psychological lightness, a and B represent psychological chromaticity, and its color difference is represented by △ E. when a is positive, it represents partial red, and when it is negative, it represents partial green; When B is positive, it means yellow, and when B is negative, it means blue; When l is positive, it means the color is lighter, otherwise it is darker. The color difference value △ e is generally less than 3. The color difference is not great, but it is also affected by dark and light colors and printing materials

3 use chromatics to mix spot color ink

ink is the color rendering material of printing, which is a mixture of pigments, binders, fillers and cosolvents. It is a colloid with complex structure. Ink blending refers to the whole process of blending one or more inks together and adding certain auxiliary materials to meet the needs of printing and color. Any color can be obtained by mixing three primary colors in different proportions

3.1 the rule that the color allocation of ink should follow

(1) the allocation of spot color ink should be carried out under the standard light source D65. In the daytime, it can be carried out in the North window with sunshine

(2) equal mixing of three primary color inks can approximate black. If you add different proportions of white ink or diluent, you will get different shades of gray ink

(3) trichromatic inks mixed in different proportions can obtain interchromatic or multicolor of different hues

(4) intermediate colors can be obtained by mixing the two primary inks in equal quantities; By mixing in different proportions, interchromatism with different hues can be obtained

(5) the more kinds of colors used in color matching, the worse the brightness. Add black ink to any hue ink, and the lightness value decreases; Add white ink to increase its brightness

(6) pay attention to the influence of the paper used, overprint color sequence, lighting source color on the ink color and the color changes before and after the imprint drying

(7) complementary colors can be used to correct color deviation, but only when the brightness value of the matched ink is high

(8) try not to use different kinds of original inks to reduce the complementary effect

(9) pay attention to the influence of ink viscosity on hue

(10) before the ink matching of more complex spot colors, a small amount of trial matching can be carried out to determine the ratio, and then the amount of ink used can be matched according to the ratio to avoid high reliability costs

3.2 deployment of dark ink

only use trichromatic or interchromatic primary ink without any diluent to deploy ink, which is collectively referred to as the deployment of dark ink. The deployment of dark ink has the following steps:

(1) determine which primary colors are contained in the original color sample and discharge the order of main colors, auxiliary colors and the approximate proportion of each color ink

(2) determine the mixing quantity according to the inking area, ink coloring power, printing plate depth, paper performance, ink viscosity, printing quantity and other factors of the printed matter

(3) add ink in the order of large to small according to the mixing proportion. First weigh the main primary color with the most content, then weigh the auxiliary color with less content, and then add the auxiliary color ink to the main color ink several times and mix it evenly

(4) after comparing the color and adjusting the proportion relationship of the three primary colors, the printability can be adjusted by printing aids after it conforms to the original

(5) record the proportional relationship of the primary color components used to ensure the consistency of the reconstituted ink in case of reprint or insufficient ink volume

3.3 deployment of light color inks

all spot color inks prepared by adding white oil, white ink, diluent, gloss paste and other diluted inks to the original ink are called light color inks. The deployment of light color ink is mainly based on diluted ink, supplemented by primary color ink. Select the appropriate diluent according to the requirements of the transparency of the color sample. Generally, the light ink used for dot printing should use transparent diluent. As a light ink diluent for field printing, white ink can be selected. The blending process is as follows:

(1) determine the type of primary color ink used and the ratio of diluent according to the primary color sample control chromatography

(2) according to the amount of ink required, first weigh the diluent in proportion, and then gradually add the selected primary color ink. If there is more than one primary color ink, add the one with a large amount first, and then the one with a small amount

(3) scrape the small color sample and check it against the original sample, constantly adjust the amount of original ink, and then adjust its printability through printing aids after it meets the original sample

(4) record the proportion of raw materials used

the key to mixing light ink is to master the dilution degree of ink. If the allocated ink color is too deep, the printing ink layer is required to be thin, which will cause the "flower plate" or the field color to be not bright; If the allocated ink color is too light, it needs a thicker ink layer to meet the color requirements during printing, which is easy to cause problems such as "pasting" and incomplete drying, dirty back, etc

the above is only a few aspects of the application of chromatics in the printing industry. In addition, printing chromatics also plays an important guiding role in point color, printing materials, printing technology and so on. This article just plays a role of throwing bricks and attracting jade for everyone. Please correct any improper omissions

source: PRINT world author: zhangzujiang

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