Application of spot color printing in packaging in

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Analysis on the application of spot color printing in packaging industry at present, economic globalization has become an irresistible trend of world development. With the accelerating pace of economic globalization, China has reached the threshold of the World Trade Organization (WTO). After joining the WTO, China's economic development will face greater tests and challenges of economic globalization. Economic globalization is actually a global market economy. Since it is a market economy, there is an objective law that cannot be overturned: opportunity and risk coexist, and opportunity is often bred in risk. After China's entry into WTO, what situation will China's packaging industry face, how to grasp the opportunities brought by China's entry into WTO for the development of China's packaging industry, how to promote the optimization and upgrading of the packaging industry structure and the improvement of the quality of packaging enterprises, and how to deal with the challenges brought by China's entry into WTO for the development of China's packaging industry, and how to form a cooperative war with environmental protection, safety supervision and other work, It will be a major issue for China's packaging industry to survive and develop better in the reform and opening up in the new century

at the same time, with the development of market economy and the improvement of people's living standards, manufacturers in the packaging industry are gradually moving towards industrialized large-scale production. Consumers have higher and higher requirements for the appearance quality of product packaging. It has become a trend to pursue the appearance decoration and performance specificity of products. Based on this, good packaging can beautify commodities, while bad packaging may bring adverse effects to commodities. The aesthetics of packaging is closely related to the value of the product itself. In order to better stimulate consumers' vision and stimulate their purchase desire, many manufacturers now like to use large-area color blocks for product packaging design. In particular, domestic tobacco and wine packaging design likes to use large areas of red and yellow blocks and large areas of gold and silver blocks. However, in order to make the commodity packaging meet the customers' expectations, manufacturers in the packaging industry need to pay close attention to the practical application of spot color in their production process, so as to avoid the production of products that do not meet the customers' expectations, which will cause customers' complaints, complaints, return compensation and even loss of supply

spot color printing is characterized by large-area on-site color block, good shelf display effect, reduced color difference caused by point overprint and point deformation, stable color, easy identification, etc

in order to correctly and reasonably use spot colors, packaging and printing manufacturers need to have a necessary understanding of the color presentation principle and several concepts (three primary colors of color and light, three primary colors of color material, color light addition method and color material subtraction method). Only by knowing the principle of color, can we reasonably control the use of color in the printing process. According to the physical stimulation characteristics of light, human visual physiological characteristics and a large number of color light mixing experiment results, red light, green light and blue light can be mixed in different proportions to obtain all other color lights, but they can not be mixed by any other color lights, because generally they are not less than 90% of the nominal maximum force FM of the whole steel strand; Red light, green light and blue light are identified as the three primary colors of color light. The new color light obtained by mixing two or more color lights is called color light additive method. The new color light is brighter than any color light participating in the mixing, and the color light addition method follows the principle that the brighter the color is, the brighter the color is. After mixing the three primary color lights in different proportions according to the color light plus color method, all the color lights in nature can be generated. Pigment refers to the material that has a certain color and can color other objects. 2. Guide pillar material. Pigments are non luminescent, and their color mainly depends on the reflection (or transmission) of their absorption of external light. The three primary colors of pigment refer to yellow, magenta and cyan, which are the complementary colors of blue, green and red. Yellow pigment can absorb blue light in white light, transmit or reflect red and green light in white light, magenta pigment can absorb green light in white light, transmit or reflect red and blue light in white light, and cyan pigment can absorb red light in white light, transmit or reflect blue and green light in white light. Pigment subtraction refers to the phenomenon that two or more pigments are mixed to obtain a new color. Based on the three primary colors and mixed in different proportions, it can be blended into all other colors, and the three primary colors cannot be blended with other colors. The essence of pigment subtraction method is to increase the number of selective absorption of pigments, so that the color light energy is weakened, so the brightness decreases and tends to dark while the color changes. Printing and packaging manufacturers generally use medium yellow, magenta (or magenta) and sky blue inks to replace the yellow, magenta and cyan in the three primary colors of pigments

in packaging printing, two color printing processes are generally used. One is normal four-color printing, which refers to the printing process of duplicating various colors of color originals by overprinting with medium yellow, magenta (or magenta), sky blue and black ink. The other is spot color printing, which only uses other color inks other than the normal four colors to copy the original color. It is more common to use spot color printing process to print a large area of background color. If the product original contains many pictures of different colors, it needs to be scanned and separated by the electronic color separation machine or color desktop system, and then produced by the normal four-color printing process. If the product original is composed of uniform color blocks of different colors and regularly graded color blocks and characters, spot color printing is sometimes used under the condition of improving printing quality and reducing overprint times

the ink prepared for spot color printing obtains the color according to the principle of pigment subtraction, with low lightness and high saturation. Spot color blocks with uniform ink color are usually printed on the spot, and the amount of ink should be appropriately increased. When the thickness of the ink layer of the layout is large, the sensitivity of the change of the thickness of the ink layer to the color change will be reduced, so it is easier to obtain a uniform and thick printing effect. Due to the uneven technical level of the current paper manufacturers, the color of the surface of the paper of the same specification will be more or less deviated, or blue, or yellow, which brings trouble to the printing and packaging manufacturers to control the color of the products. If we can reasonably and properly use the strong opacity of the spot color block, it can be well solved. The four-color printing results in the comprehensive effect of dot subtraction absorption and addition, with high brightness and low saturation. For the light color block, the four-color printing process is adopted. Due to the low coverage of the ink on the paper, the ink color is flat and lacks a thick feeling. Due to the point angle, people will inevitably feel the existence of patterns. In addition, for the color block overprinted by the four-color printing process, since most of the colors constituting the color block are composed of a certain proportion of dots, the ink layer thickness must be strictly controlled when printing dots. It is easy to change the color intensity and dot enlargement due to the change of ink layer thickness and the change of printing process conditions, resulting in color change. Moreover, the change of any color of the color block will lead to the change of the color of the color block, and the chance of uneven ink color will be doubled. Therefore, the color block printed by four-color printing process is not easy to achieve the effect of uniform ink color. If the multi-color machine can not be used to print the color of the color block at one time, it is easy to have color deviation because the color of semi-finished products is not easy to control. For example, the sky blue and magenta are overprinted into purple. If the sky blue ink volume is large, it will be blue, and if the magenta ink volume is large, it will be red, which will bring great trouble to the machine operator. If the operator's level is not very high, the printed products may be a variety of colors. At this time, it is advisable to change the overprint color block into a special purple version. Although there is one more version, the printing preparation time is shortened, the printing speed is improved, the hue control is stable, the production efficiency is improved, the waste products are reduced, and the overall production cost is reduced. Of course, this phenomenon should be considered in the process planning

in addition, when printing a large area of light uniform color blocks, it is usually used to add diluent to the original ink to prepare the spot color ink, and then carry out field printing. In this way, the ink layer is thicker, and it is easier to obtain the effect of uniform and thick color. If a four-color printing process is used, flat dots with a low number of layers must be used. However, a low percentage of flat spots are easy to be reduced by small sand particles or slightly poor air extraction during printing, resulting in uneven ink color. During printing, it is also easy to cause poor oil and ink transfer of small spots due to excessive water supply of the layout, accumulation of paper powder on the printing plate and blanket, and low smoothness of the paper. As a result, the ink color becomes shallow and uneven, resulting in batch color difference and increased waste products. For dark large-area color blocks, the four-color printing process may need to be formed by the superposition of high percentage points of several colors, and the ink layer is too thick, causing the back to rub dirty; The spot color printing process only needs to print one color, so it is not easy to get dirty on the back. With the four-color printing process, some parts of the picture and text may be composed of several colors, while with the spot color printing process, only one color is printed on the corresponding parts, avoiding the possibility of overprint error

the above describes the use of spot color inks prepared with three primary colors. In fact, in packaging and printing, in addition to the ink mixed with three primary colors, there is also an ink that people like to use very much, which is metal ink. Because of its special metallic luster, metal ink has been widely used in packaging and printing, especially in tobacco and alcohol packaging and printing. The commodity packaging printed with metal ink looks elegant and noble, which can well improve the grade of the commodity itself. However, due to the poor adhesion of metal ink itself, it is more difficult than ordinary spot color ink in actual printing

there are two common metal inks, namely, gold ink and silver ink. Gold ink is made of copper zinc alloy powder and gold blending oil. The color of gold ink varies with the content of copper and zinc in gold powder. The content of zinc is low, and the color of gold ink is red; If the zinc content is high, the gold ink color will be blue. At present, gold powder (ink) sold only in the market can be divided into red gold powder (ink), green red gold powder (ink) and green gold powder (ink). Silver ink is made of silver aluminum powder and silver blending oil. The metallic luster produced by different sizes of silver powder particles is also different. The metallic luster of silver powder with coarse particles is stronger. Appropriate addition of some light medium yellow, light oil, red drying oil, dibutyl ester and other auxiliary agents in the gold and silver ink. Rausberg uses aluminum alloy to build the framework additives, which can enhance the affinity, viscosity and fluidity of the gold and silver ink, improve the adhesion of the gold and silver ink, and thus improve the printing transmission performance of the gold and silver ink

there are generally two ways to print gold and silver ink. One is to make a base before printing gold and silver ink. That is, the ink with strong hiding power and similar color to gold (silver) ink is used as the background color. Gold printing ink uses light yellow ink, transparent yellow ink or false gold ink to make the background color. In order to improve the metallic luster, you can also add about 10% gold ink. The silver printing ink is generally made of false silver ink. The fake silver ink can be prepared by diluting agent, white ink, black ink, destaching agent, No. 6 ink mixing oil and white dry oil in a certain proportion. The printing adaptability of silver ink is better than that of gold ink. It can basically meet the requirements of general packaging printing products with only one printing. If touched

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