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The importance of color to packaging

Time:2023-11-13 Views:464
Color science is the science of the production, reception, and application of color. Because form and color are the two major elements of image and art image, color science is the primary and basic subject of art theory. It is based on optics and involves disciplines such as psychophysics, physiology, psychology, aesthetics and art theory. In the history of color application, decoration function appeared before reproduction function.
The study of color only began in the 19th century, it is based on the development of optics, Newton‘s daylight - prism refraction experiment and Kepler laid down the modern experimental optics for color science provided a scientific basis, and psychophysics solved the problem of visual mechanism to reflect light.

1、Use color science to produce printing chromatography

In the whole process of color reproduction, there are three processes: color analysis, color transmission and color combination. The correct control of color change in each process is directly related to the final quality of the print, so a color standard, printing chromatography, is needed to regulate the various shades in the printing process.

Printing chromatography is the use of three primary colors yellow, magenta, blue and black, according to different proportions or dot percentage mixed, laminated together to form a variety of color patterns of the atlas, for people in the design, original copy, ink deployment and other aspects of reference.

Four-color chromatography is the use of yellow, magenta, green, black four-color inks, with different dot area percentage overprint superposition, and arranged in a certain order, it has an important reference and guidance for electronic color separation, proofing and printing processes.

The spot color in printing is a kind of color ink that has been mixed, which is not directly related to the color of Y, M, C, and K, so a set of standard primary color ink is first defined, which produces a variety of color color samples according to different mixing ratios, and each color sample is marked with a scalar that indicates the mixing ratio of primary colors, so that people use the three primary colors ink to blend a variety of color spot colors. This is spot color chromatography.

However, printing chromatography is the use of color to indicate color, its production is usually affected by ink, paper, printing process and equipment and many other factors, so the printing unit should be based on the use of raw materials, production process, equipment conditions and other production of their own special printing chromatography.

2、Use chromatics to measure color and color difference
Color measurement in color printing can be roughly divided into: contrast visual measurement method, density measurement method and chrominance measurement method.
In the printing process, contrast visual method is used to measure the color, mainly relying on experienced operators to evaluate the color of the original manuscript, signal bar and printed sheet by contrast visual method with reference to the standard color rate. Due to the influence of the observer‘s own physiological and psychological factors, the accuracy of contrast visual measurement is relatively poor. However, because it does not need to be equipped with fine measuring instruments, it is still widely used in the general printing copy 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 the three primary colors of ink, and the detection equipment is simple, so it is widely used. However, the use of optical density as a means of monitoring and measuring the printing process, only from the control strip to obtain the size of each monochromatic ink, and can not directly obtain the color error information from the image, so it is difficult to communicate with printing customers, it is not convenient to accurately control the color reproduction, so the density measurement is only an indirect color measurement method.

Based on the principle of colorimetry, colorimetric method takes the color of the important part of the printed image as the monitoring point, directly measures the value of the three stimuli of the color, and obtains the color chromaticity information. The method can accurately express the color difference and the desired approximation between the standard sample and the tested sample, without the need to add a standard or control bar. However, it has not been promoted and popularized at present, mainly because of the high price of the instrument, which has high color theory requirements for users.

In the color printing and reproduction work, it is not only necessary to understand the three attributes of color, but also to understand the difference between colors in order to compare and distinguish colors, which is color difference. The unit of color difference is NBS, which stands for National Bureau of Standards.

At present, the universal color measurement standard in the world is CIE1976Lab uniform color space, which was put forward by Canadian Wizerski at the eighteenth CIE Conference in 1975. Where L represents psychological brightness, a, b represents psychological chroma, and its color difference is expressed by △E, when a is positive, it indicates red, and when it is negative, it indicates green; When b is positive, it is yellow; when B is negative, it is blue; If L is positive, the color is lighter; otherwise, it is darker. The color difference △E is generally less than 3, and the color difference is not very big, but it is also affected by deep, light and substrate materials.

3、Use chromatics to blend special color inks

Ink is the color of printed matter, is a mixture of color, binder, filler and co-solvent components, is a complex structure of the colloid. 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. Printing any color can be obtained by mixing the three primary colors in different proportions.

★ The color of ink should follow the law

(1)The deployment of special color ink should be carried out under the standard light source D65, if it is daytime, it can be carried out in the north window with sunshine.

(2)The three primary colors of ink equal mixing, can be approximately black. If different proportions of white ink or diluent are added, grey ink of different tones can be obtained.

(3) The three primary colors are mixed in different proportions to obtain different shades of intermediate or compound colors.

(4) The two primary colors can be mixed in equal amounts to obtain intermediate colors; Mixed in different proportions, different hues can be obtained.

(5) The more color types used in color matching, the worse the brightness, adding black ink to any color ink, the brightness value is reduced; Add white ink, its brightness increases.

(6)Pay attention to the influence of the paper used, the color sequence of the printing, the color of the lighting source on the ink color and the color change before and after the printing is dried.

(7)Complementary colors can be used to correct color bias, but only when the ink brightness value is high.

(8)Try to use different varieties of original ink as little as possible to reduce the complementary effect.

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

(10)Before the more complex spot color matching ink, a small amount of test matching can be done to determine the ratio, and then the amount of ink used can be matched according to the ratio to avoid waste.

★ Dark ink deployment

Only the use of three primary colors or intercolor primary ink, without any diluent to carry out ink deployment, collectively referred to as the deployment of dark ink. The deployment of dark ink has the following steps:

① Determine the primary colors contained in the original color sample and the order of the main colors, auxiliary colors and the approximate proportion of each color ink.

② According to the inking area of the printed matter, ink coloring force, plate depth, paper performance, ink viscosity, printing quantity and other factors, to determine the amount of deployment.

③ Add ink according to the proportion of deployment, according to the order of large to small. 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 blend evenly.

④ After comparison, adjust the proportion of the three primary colors, meet the original, and then adjust its printability through printing additives.

⑤ Record the proportional relationship of the primary color components used in order to ensure the consistency of the rematching ink color when the amount of ink is not enough.

★ Light ink deployment

All in the original ink to add white oil, white ink, diluent, light paste and other diluting inks are called light ink. The deployment of light ink is mainly based on diluted ink, and the original color ink is supplemented. According to the requirements of the transparency of the color sample, the appropriate diluent is selected. Generally used for dot printing light ink should be selected transparent diluent. White ink can be used as the diluent of light color ink for field printing. The deployment process is as follows:

① According to the primary color sample control chromatography to determine the primary color ink type and diluent ratio relationship.

② According to the amount of ink required, first weigh the diluent in proportion, and then gradually add the selected original ink, if the original ink is more than one, add the large amount first, and then add the small amount.

③ Check the small color sample with the original, constantly adjust the amount of the original ink, and then adjust its printability through the printing additives.

④ Record the ratio of raw materials used.

⑤ Deployment of light ink, mastering the degree of ink dilution is the key. If the ink color is too deep, the printing ink layer is required to be thin, which will cause the "flower plate" or the field color is not bright; If the ink color is too light, the printing needs a thicker ink layer to meet the color requirements, which is easy to cause problems such as "paste plate" and drying is not thorough, and the back is sticky.
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