With the development of economy, the application of labels on commodities has become more and more extensive, and this has led to the rapid development of the label printing industry. However, at present, people's understanding of label printing inks is far less than the understanding of label materials, printing methods, and other aspects. Label printing inks need to be recognized and explored as a mysterious field. In this issue of the label theme, the author deliberately copied the first-line production staff and ink factory professionals of a number of label printing plants and asked them to briefly introduce the selection, use, and management of label printing inks. It plays a role in attracting valuable opinions and inspires readers. ■ Author: What are the main types of label printing inks? What are their advantages and disadvantages? ■ Guests: There are many types 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. Water-based ink is safe, sanitary, non-polluting, conforms to environmental protection requirements, and is beneficial to human health. However, it also has disadvantages, such as slow drying speed, low color saturation, poor stability, etc. It is not suitable to print large areas on the ground. It is prone to precipitation and separation for a long time. Layer phenomenon. Solvent label printing inks have strong adaptability to label materials, stable performance, and high printing quality, but there are environmental pollution problems. Some volatile solvents are harmful to the human body. UV label printing ink has excellent performance, reliable quality and wide application range, but the price is high, and it requires special drying equipment. It also has certain requirements for supporting materials. ■ I: What are the factors to consider when choosing a label printing ink? ■ Guests: In the selection of label printing inks, comprehensive consideration shall be given to the types of printing materials, printing methods and printing conditions, customer's special requirements, post-press processing, label usage, usage conditions, and cost factors. (1) The type and performance of printing materials are the most important factors in determining label printing inks. Different printing materials need different inks. For example, paper labels can be printed using aqueous inks, while film labels are usually printed using solvent-based inks. Even if the printing materials of the same kind have different types, grades, and surface properties, they should use different inks. (2) Printing methods and printing conditions are also one of the important factors affecting the selection of label printing inks. Different printing inks cannot be replaced or mixed; printing speed, type and performance of the printing equipment also have an impact on ink selection. (3) Sometimes customers have certain special requirements on the label, such as ice effect, sanding effect, anti-counterfeiting effect, etc., from the perspective of label printing ink to consider how to meet the special requirements of customers and products. (4) Whether the label has to follow its pasted product undergoes some special processing techniques, which also has an impact on the choice of ink. In some product processing processes, the label is subjected to a high temperature test, or contact with certain chemical reagents requires ink Has excellent high temperature resistance, chemical resistance, etc., to avoid causing label deformation or damage. (5) The use of labels and the use of the environment are also factors that can not be ignored for ink selection. For example, the labels used on daily chemical detergents require inks with good acid and alkali resistance, grease resistance, etc.; labels used outdoors must withstand the wind. To withstand the sun and rain, we must pay attention to the performance of light, water, high temperature, and acid and alkali resistance when selecting inks. (6) The cost factor, the company's goal is to maximize the pursuit of profits, which must involve the issue of cost. UV inks have the highest prices, followed by water-based inks, and solvent-based inks have the lowest prices. Also consider the costs and costs of transportation, storage, etc. ■ Author: What are the main performance requirements for label printing inks and how do they affect label printing? ■ Guests: The performance of label printing inks mainly includes hue, fineness, saturation, glossiness, adhesion, viscosity, and drying properties. These properties have an important influence on the printing process and print quality. (1) The stability of ink viscosity is the precondition to ensure the consistency of the quality of the printed matter. Too high or low viscosity of the ink is not conducive to printing. In general, during the printing process, as the water and solvent of the ink continuously evaporate, the ink viscosity will gradually To improve, we should always measure the viscosity of the ink, make a good record of changes, and make timely adjustments. (2) The dryness of the ink also has a great influence on the label printing. Drying too quickly may cause the pattern to become lighter or even dry. If the drying is too slow, it may cause the ink to stick or the print to become dirty. In general, the drying speed of the ink is compatible with the printing speed, the drying ability of the printing apparatus, and the area of the printing pattern. (3) The pH control of water-based inks is very important, usually between 8 and 9. Changes in the pH of water-based inks can cause changes in viscosity, and an appropriate amount of pH stabilizer is added to the ink at regular intervals during the printing process. ■ The author: How does the printing shop environment affect the performance of label printing inks and printing quality? ■ Guests: The impact of the printing shop environment on ink performance and print quality is mainly reflected in the following two aspects. (1) The viscosity and dryness of the ink are sensitive to the ambient temperature. When the temperature rises, the viscosity of the ink decreases and the drying speed becomes faster. On the contrary, the ink viscosity increases and the drying speed becomes slower. In addition, the humidity of the environment has an influence 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 best to install air conditioning and humidity control equipment in the printing shop so that the temperature and humidity in the workshop are kept constant. In general, the temperature of the printing shop is controlled at 18-25°C and the humidity is controlled at 55%-65%. (2) The hygienic condition of the printing shop is also very important. If the hygienic conditions of the workshop are poor, a large number of dust particles or various impurity particles may fall into the ink tank or adsorb on the surface of the label material, thereby affecting the printing quality. Therefore, the printing shop should be kept clean, dust-free and well ventilated and exhausted. ■ I: What problems have I encountered in using label printing inks and how can I solve them? ■ Guests: In the printing process, we often encounter problems such as poor adhesion of ink, poor drying of ink, adhesion of ink layer, bubbles, paste plate, dry plate, poor ink transfer, color shift, etc. These failures are analyzed as follows. (1) Poor adhesion of ink. Reason: The surface tension of the substrate is too low, the type of ink does not match the substrate, and ink properties are poor. Solution: surface treatment of substrate materials, adding wetting agent to reduce ink tension, replace ink. (2) Poor ink drying. Reasons: Improper ink solvent ratio, too fast printing speed, and high ambient humidity. Solution: Adjust the solvent ratio, reduce the printing speed, increase the drying temperature, and reduce the humidity. (3) Ink adhesion. Reasons: poor ink drying, ink is too soft, printing pressure is too large, the environment humidity is too high. Solution: Adjust ink solvent ratio, add appropriate amount of anti-adhesive agent, increase drying temperature, reduce printing pressure, and reduce environmental humidity. (4) Bubbles. Cause: The ink contains air, the surface tension of the ink is too large, the ink viscosity is too low, and the printing speed is too fast. Solution: Add an appropriate amount of defoamer, adjust the ink viscosity, and appropriately reduce the printing speed. (5) Paste. Cause: The ink pigment particles are too thick, the ink viscosity is too high, the amount of ink is too large, the printing pressure is too high. Solution: Replace the ink, reduce the viscosity of the ink, reduce the amount of ink, and reduce the printing pressure. (6) Dry version. Reason: The ink is drying too fast, the drying temperature is too high, the printing speed is too slow. Solution: Adjust the ink solvent ratio, reduce the drying temperature properly, and increase the printing speed. (7) Poor ink transfer. Cause: The type of ink and printing materials do not match, ink viscosity is too high, static electricity and so on. Solution: Replace ink, adjust ink viscosity, add antistatic agent. (8) Color cast. Reasons: Inaccurate hue of ink, improper ink drying speed, poor ink stability, performance of printing materials, and changes in the printing process. Solution: Replace the ink, adjust the solvent ratio, and adjust the printing process parameters. (9) Static electricity. Cause: 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, adjust humidity, etc. ■ The author: What issues should be noted during the use of label printing ink? ■ Guests: In the printing process, we should also pay attention to the following issues. (1) Use the same brand ink produced by the same ink manufacturer to avoid the printing failure of different manufacturers and different ink types. (2) The ink is fully stirred before use, and it is often stirred during the printing process to ensure that the ink system is evenly dispersed. (3) Each deployment of ink should not be too much, should follow the principle of "less increase, increase", not only is conducive to the stability of ink performance, but also can effectively avoid waste; In addition, for spot color inks, it should also be prepared recording. (4) In the printing process, in order to ensure the quality of the printed label and the smooth production of the product, some auxiliaries such as antistatic agents, defoamers, and rewinders should be added to the ink. Attention must be paid to the amount of addition. Within the prescribed range. ■ The author: What are the shortcomings of the label printing ink currently on the market? ■ Guests: The most prominent issue is the ink hue deviation problem. On the one hand, the hue of the same ink produced by different ink manufacturers is different, as is the primary color red ink, some manufacturers' hue is reddish, some manufacturers' hue is yellowish, and the degree of color shift is also different. On the other hand, even the same ink produced by the same manufacturer, with different batches, may deviate from the hue and sometimes become large. For this reason, label printing companies often have to stop the commissioning, which is very unfavorable for the stability of the printing quality, and it brings great inconvenience to production, which seriously hampers the improvement of the quality of printed matter. There is a certain gap between domestic inks and imported inks, 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 entire ink manufacturing industry. ■ Author: How to properly store label printing ink? ■ Guests: In order to achieve a better preservation effect, the label printing ink should be stored in a closed container under normal temperature, cool, dry, dark, and ventilated environment. ■ The author: What issues should be noted during the storage and management of label printing inks? ■ Guests: Should pay attention to the following questions. (1) Safety First, store ink as far away as possible from fire and heat sources to prevent accidents. (2) It is best to maintain a constant temperature in the ink depot. The temperature difference from the printing shop should not be too different. If the temperature difference between the two is large, the ink should be placed in the printing shop in advance, which is not only beneficial to the stability of the ink performance, but also ensures the high efficiency of production. (3) In some areas in the north, it is relatively cold in winter. Avoid storing the ink outdoors and prevent the ink from gelling at low temperatures. If gelation occurs, transfer it to a warehouse with high temperature, or put it in hot water to restore the insoluble matter. (4) The principle of "first in, first out" should be followed in ink storage and management, that is, the ink first purchased should be used first to prevent the ink from affecting its use effect due to the long storage time. (5) The ink also has a certain shelf life. If it is stored too long, various components of the ink will separate and precipitate. Therefore, the ink should not be stored for a long time. The general storage period is one year.
August 29, 2022
