Q & A on the most popular printing ink for labels

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With the development of economy, labels are more and more widely used in commodities, which drives the rapid development of label printing industry. However, at present, people's understanding of label printing ink is far less than that of label materials, printing methods and other aspects. Label printing ink is a mysterious field that needs us to understand and explore. In this issue of the special topic on labels, the author specially imitated the first-line production personnel of many label printing plants and the professionals of the ink factory, and asked them to make a brief introduction on the selection, use and management of label printing ink, hoping to play a role in attracting jade and enlighten the readers. I would like to express my heartfelt thanks to Mr. luopingping of Huangshan Xinli ink factory, Mr. wangnianci of Hefei process label factory, Mr. Li Lianjun and Mr. liyunfei of Shenzhen Jinjia color printing group and Mr. Hu of Shenzhen jiaoguan technology industry for their strong support

■ Author: what are the main types of label printing inks? What are the advantages and disadvantages of each

■ guest: there are many kinds of label printing inks. According to the different solvents used, they can be divided into three categories: water-based label printing inks, solvent based label printing inks and UV label printing inks

the water-based ink is safe, hygienic, pollution-free, meets the requirements of environmental protection, and is conducive to human health; However, it also has some disadvantages, such as slow drying speed, low color saturation, poor stability, etc. it is not suitable to print a large area of the field, and precipitation and stratification are easy to occur after a long time

solvent based label printing ink has strong adaptability to label materials, stable performance and high printing quality, but there are environmental pollution problems. Some volatile solvents are harmful to human body

uv label printing ink has excellent performance, reliable quality and wide application range, but the price is high, and special drying equipment is required, and there are certain requirements for supporting materials

■ Author: what factors should be considered when selecting label printing ink

■ guests: when selecting label printing ink, we should comprehensively consider the types of printing materials, printing methods and conditions, special requirements of customers, post press processing technology, uses and conditions of labels, costs and other factors

(1) the type and performance of printing materials are the most important factors to determine the label printing ink. Different printing materials need different inks. For example, paper labels can be printed with water-based ink, while film labels are usually printed with solvent based ink. Even if the printing materials of the same kind have different varieties, grades and surface properties, different inks should be used

(2) printing method and printing conditions are also one of the important factors affecting the selection of label printing ink. Ink of different printing methods cannot be replaced or mixed; Printing speed, type and performance of printing equipment also have an impact on ink selection

(3) sometimes customers have some special requirements for labels, such as ice flower effect, frosting effect, anti-counterfeiting effect, etc., so we should consider how to meet the special requirements of customers and products from the perspective of label printing ink

(4) whether the label should go through some special processing process with the product it is attached to also has an impact on the selection of ink. In the processing process of some products, the label must withstand the test of high temperature or contact with some chemical reagents, so the ink is required to have excellent high temperature resistance and chemical resistance, so as to avoid deformation or damage to the label

(5) the use and use environment of the label are also factors that cannot be ignored in the selection of ink. For example, the label used on daily chemical washing products requires that the ink has good acid and alkali resistance, grease resistance, etc; Labels used outdoors should withstand the test of wind, sun and rain. When selecting ink, we must pay attention to the performance of light resistance, water resistance, high temperature resistance, acid and alkali resistance, etc

(6) cost factors. The goal of the enterprise is to maximize profits, which inevitably involves cost issues. UV ink is also the highest price that can be used, followed by water-based ink, and the price of solvent based ink is the lowest. Also consider the costs and costs of transportation, storage, etc

■ Author: what are the main performance requirements for label printing ink? How do they affect label printing

■ guest: the performance of label printing ink mainly includes hue, fineness, saturation, gloss, adhesion, viscosity, dryness, etc., which have an important impact on the printing process and printing quality

(1) the stability of ink viscosity is the premise to ensure the consistency of print quality. Too high or too low ink viscosity is not conducive to printing. Generally speaking, during the printing process, with the continuous volatilization of ink moisture and solvent, the ink viscosity will gradually increase. The ink viscosity should be measured frequently, recorded and adjusted in time

(2) the dryness of the ink also has a great impact on label printing. Too fast drying is easy to cause the pattern to become shallow or even dry; Too slow drying is easy to cause ink adhesion or dirty prints. Generally speaking, the drying speed of the ink is compatible with the printing speed, the drying capacity of the printing equipment and the area of the printed pattern

(3) for water-based inks, the control of pH value is very important, generally between 8 and 9. The change of pH value of water-based ink will cause the change of viscosity. An appropriate amount of pH stabilizer should be added to the ink every certain time during the printing process

■ Author: how does the printing workshop environment affect the performance of label printing ink and printing quality

■ guest: the impact of printing workshop environment on ink performance and printing quality is mainly reflected in the following two aspects

(1) ink viscosity and dryness are sensitive to ambient temperature. When the temperature increases, the ink viscosity decreases and the drying speed becomes faster; On the contrary, the ink viscosity increases and the drying speed slows down. In addition, the environmental humidity also has an impact on the dryness of the ink. Too high humidity in the workshop is not conducive to the drying of the ink; If the workshop is too dry, it is easy to cause printing failure due to static electricity. It is better to install air conditioning and humidity control equipment in the printing workshop to keep the temperature and humidity in the workshop constant. Generally speaking, the temperature and humidity of the printing workshop should be controlled at 18 ~ 25 ℃ and 55% ~ 65%

(2) the sanitary condition of the printing workshop is also very important. If the sanitary condition of the workshop is poor, a large number of dust particles or various impurity particles may fall into the ink tank or adsorb on the surface of label materials, thus affecting the printing quality. Therefore, the printing workshop should be kept clean, dust-free and well ventilated

■ Author: what problems have you encountered in using label printing ink? How to solve it

■ guests: during the printing process, we often encounter problems such as poor ink adhesion fastness, lower stage 1, poor ink dryness, ink layer adhesion, bubbles, plate pasting, dry plate, poor ink transfer, color deviation, etc. the analysis of these failures is as follows

(1) poor ink adhesion fastness. Reasons: the surface tension of the substrate is too low, the ink does not match the type of the substrate, and the ink performance is poor. Solution: surface treatment of printing materials, addition of wetting agent to reduce ink tension and replacement of ink

(2) poor ink dryness. Causes: improper ink solvent ratio, printing speed is too fast, environmental humidity is too high. Solution: adjust the solvent ratio, reduce the printing speed appropriately, increase the drying temperature, reduce the environmental humidity, etc

(3) ink layer adhesion. Causes: poor drying of ink, too soft ink, excessive printing pressure and high environmental humidity. Solution: adjust the ink solvent ratio, add an appropriate amount of anti adhesion agent, increase the drying temperature, reduce the printing pressure, reduce the environmental humidity, etc

(4) bubbles. Reasons: the ink contains air, the surface tension of the ink is too large, the viscosity of the ink is too low, and the printing speed is too fast. Solution: add an appropriate amount of defoamer, adjust the ink viscosity, and properly reduce the printing speed

(5) paste. Reasons: the ink pigment particles are too thick, the ink viscosity is too high, the ink amount is too large, and the printing pressure is too high. Solution: replace the ink, properly reduce the ink viscosity, reduce the amount of ink, and reduce the printing pressure

(6) dry plate. Reasons: ink drying speed is too fast, drying temperature is too high, printing speed is too slow, etc. Solution: adjust the ink solvent ratio, properly reduce the drying temperature, apply windows98/me/2000/xp operating system platform, and improve the printing speed

(7) poor ink transfer. Cause: the type of ink and substrate does not match, the ink viscosity is too high, there is static electricity, etc. Solution: change the ink, adjust the ink viscosity, and add antistatic agent

(8) color deviation. Causes: deviation of ink hue, improper ink drying speed, poor ink stability, change of substrate material performance, printing process, etc. Solution: change the ink, adjust the solvent ratio, adjust the printing process parameters, etc

(9) static electricity. Reasons: the ink is too thin, the printing speed is too fast, and the environment is too dry. Solution: add antistatic agent, increase ink viscosity, reduce printing speed appropriately, adjust environmental humidity, etc

■ Author: what problems should be paid attention to in the use of label printing ink

■ guest: during the printing process, we should also pay attention to the following problems

(1) use the same brand of ink produced by the same ink manufacturer to avoid the printing failure of mixing different manufacturers and different types of ink

(2) the ink shall be fully stirred before use and frequently stirred during the printing process to ensure uniform dispersion of the ink system

(3) do not mix too much ink each time. Follow the principle of "adding less and adding more frequently", which is not only conducive to the stability of ink performance, but also can effectively avoid waste; In addition, for spot color inks, deployment records shall also be made

(4) during the printing process, in order to ensure the quality of label printing and the smooth production, some additives, such as antistatic agent, defoamer, and adhesive remover, should be added to the ink. Note that the addition amount must be controlled within the specified range

■ Author: what are the shortcomings of label printing inks in the current market

■ guest: the most prominent problem is the ink hue deviation. On the one hand, the same kind of ink produced by different ink manufacturers has different hues, such as the primary color red ink. Some manufacturers have red hues and some manufacturers have yellow hues, and the degree of color deviation is also different. On the other hand, even if the same ink produced by the same manufacturer has different batches, the hue will deviate, sometimes even very large. For this reason, label printing plants often have to stop for debugging, which is very unfavorable to the stability of printing quality, brings great inconvenience to production, and seriously hinders the improvement of printing quality

there is still a certain gap between domestic ink and imported ink, especially in high-end products. Domestic ink manufacturers should improve their technical level and production capacity as soon as possible to drive the improvement of the whole ink manufacturing industry

■ Author: how to store label printing ink correctly

■ guest: in order to achieve better preservation effect, the label printing ink should be stored in a closed container in a normal temperature, cool, dry, dark and ventilated environment

■ Author: what problems should be paid attention to in the storage and management of label printing ink

■ guest: we should pay attention to the following problems

(1) safety first, store the ink away from fire and heat sources as far as possible

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