Common sense before the most popular printing spec

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General knowledge before printing: 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 three primary color inks are mixed in different proportions to obtain interchromatic or polychromatic inks of different hues

intermediate color can be obtained by mixing the two primary color inks in equal amount; By mixing in different proportions, interchromatism with different hues can be obtained

the more kinds of colors used in color matching, the worse the brightness. Adding black ink to any hue ink will reduce the brightness value; Add white ink to increase its brightness

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

color deviation can be corrected by complementary color, but it can only be carried out when the brightness value of the matched ink is high

try to use less original inks of different varieties to reduce the complementary effect

pay attention to the influence of ink viscosity on hue

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 waste

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:

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

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

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

after comparing the color and adjusting the proportion relationship of the three primary colors, the printability can be adjusted by printing aids

record the proportional relationship of the primary color components used, so as to ensure the consistency of the reconstituted ink color 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:

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

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

scrape the small color sample and check it against the original sample, and constantly adjust the amount of original ink. After it meets the original sample, adjust its printability through printing aids

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, it requires high subsidies and high advantages. The printing ink layer is 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 a process of pasting, incomplete drying and dirty back. The correctness of color change control in each process is directly related to the final quality of printed matter with the continuous progress of science and technology, 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

four color chromatography is composed of yellow, magenta, cyan and black inks, overprinted and superimposed with different percentage of dot area, 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, mainly relying on experienced operators to evaluate the color of originals, signal strips and printing sheets with the reference to the standard color rate. 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

chromaticity measurement method is a color measurement method based on the principle of chromaticity, which takes the color of important parts of the printed image as the monitoring point, directly measures the three stimulus values of the color, and obtains the color chromaticity information. This method can accurately express the color difference between the standard sample and the tested sample and the required proximity, without adding another check mark or control bar. 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

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 held in the 18th session in 1975, and the inflation rate is close to 40%; After Erdogan assumed the post of prime minister, it was proposed by Canadian weizeskie at the CIE conference. Where l represents psychological lightness, a and B represent psychological chromaticity, and its color difference is represented by △ E. when a is positive, its yield load should be recorded in time, indicating partial red, and when it is negative, it indicates 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 printed in Shanghai can be obtained by mixing three primary colors in different proportions

3.1 the color allocation of ink should follow the law

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

black can be obtained by mixing the three primary inks in equal quantities. If you add different proportions of white ink or diluent, you will get different shades of gray ink

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