Fifth, the application of label ink 1, sticker ink. For common adhesive labels, flexographic printing is mainly used, and wire bonding is combined with die cutting and slitting; for those with special requirements, screen printing devices may also be added for special effects printing. . For sticker products, in fact, more issues need to be considered in terms of production efficiency. Therefore, high-speed flexographic printing equipment has become the first choice. In addition, for ordinary stickers, you can also choose special processing units such as Super glazing, to achieve a UV effect such as a mirror effect, in order to increase the added value of the product. The main reason for the UV ink curing is the irradiation of ultraviolet rays. The photopolymerization initiator in the UV ink absorbs a photon of a certain wavelength and then converts it into a free-form molecule to become a free radical, and then transmits the intermolecular energy to make the polymeric prepolymer. And the photosensitive monomer becomes an excited state, resulting in a charge transfer complex, and the complexes are continuously cross-linked and polymerized to form a film. The curing process of UV ink is a photochemical reaction process. Under the action of ultraviolet energy, the prepolymer is cured in a very short time. In addition to the surface curing of the ink, the ultraviolet ray can penetrate the liquid ultraviolet curing. In the ink, it stimulates further curing of the deep ink film. Conventional inks are solidified and dried under oxidation, while solvents based on water or water are cured by evaporation of water or solvent, and some of the ink can penetrate the paper. Therefore, compared with the traditional ink, the UV curing ink polymerization drying is more thorough, without any evaporation or solvent contaminants, 100% ink film curing. The main considerations in UV printing are: (1) For UV inks, UV light is generally easier to transmit through yellow and red, while blue and black, especially black, are difficult to penetrate. Therefore, if the printing density is increased too much in order to increase the printing effect, poor curing, ink wiping off, poor adhesion, and even a negative-stick roller may occur. In the UV printing, special attention should be paid to the printing density of the black ink. (2) Among various base materials, there are also a small amount of base materials that have poor adhesion to UV ink, scratch resistance, and flexural adaptability. In particular, synthetic paper and plastic substrates are quite diverse and there are also surface treated and untreated substrates. Ink is also quite different for various substrates, such as adhesion performance, so it is very important to choose a suitable substrate for UV ink, or to select an ink suitable for the substrate. UV inks are used for paper and plastic, and there are several types of UV inks for plastics. Be sure to test adhesion and other properties before use. Even if the substrate is paper, due to the difference in the type of paper, the type of ink, and the difference in curing conditions, accidents with low adhesion may occur. (3) Under normal circumstances, UV inks are basically usable without adjustment. However, depending on the quality of the paper, the room temperature, and the printing conditions, 2 to 5% of UV special varnish or debonding agent can be properly added. Another point is that if you use adjuvants or detergents, use special UV inks. (4) The UV ink should not be mixed with the oil ink. If it must be mixed with other inks, the ink must have fluidity, adhesion, printability, and degree of solidification before mixing. UV inks mixed with gold and silver inks and general UV inks will cause deterioration in the solidification of fluidity, faster speed, brightness and other phenomena. Therefore, please do not save the mixed ink for a long time. (5) If the ink is stored at a high temperature, solidification, hardening, etc. may occur, so be sure to store the UV ink in a dark place below 25 degrees Celsius. In particular, gold and silver inks are more prone to coagulation and weaker brightness than ordinary UV inks, and therefore do not store for a long time. (6) Compared with general oil-based inks, UV inks are relatively narrow, especially when the ink is emulsified, the emulsified ink will accumulate on the ink roller and remain on the plate and the blanket, resulting in dirt. At the beginning of printing, compared with oil ink, the supply of ink in the ink fountain is not very good compared to the oil ink, so there is a tendency to open the ink fountain excessively, the supply of ink is gradually increased on the way, and the excess ink on the printing press causes ink emulsification. . So pay special attention to the supply of ink and water. 2, shrink label ink. For thin-film labels, it is necessary to consider how to eliminate film deformation and static electricity in the equipment configuration. There are two main causes of deformation, one is tensile deformation and the other is thermal deformation. To solve the problem of film deformation, we must first choose a material with good quality and good uniformity. Secondly, in the equipment configuration, the best choice is to use a cold UV curing method, which not only has a fast curing speed, but also does not theoretically cause deformation of the material. In addition, we must consider whether the device has a device to distribute tension, such as the main power of the drive roller or roller device. There are four major categories of inks used for shrink label printing: solvent inks, water-based inks, cationic UV inks, and free radical UV inks. From the current application situation, solvent-based inks accounted for the largest market share, followed by aqueous inks and free radical UV inks. This is mainly due to the fact that the main customers of the shrinking label market are large companies, and their requirements are often long-lived in large quantities. In fact, solvent-based gravure inks are most suitable for long live printing, making solvent inks the best choice for the shrink label market. However, with the development of the shrink label market, some small customers have shown great interest in this, and the increase in small batches and short-lived editions has driven the increase in demand for water-based inks and free-radical UV inks. However, cationic UV inks are used in the shrink film field because of their high price and the troublesomeness of printing. Shrink label printing inks need to have strong adhesion, flexibility, and considerable heat resistance, and the pigments in the ink cannot be discolored or discolored at high temperatures. In the selection, the ink mainly considers the friction coefficient, shrinkage, adhesion, chemical residue and migration and other performance indicators. 3, RFID label ink. Conductive inks for RFID tags are composed of fine conductive particles or other special materials (such as conductive polymers, etc.) that, after being printed on the substrate, act as wires, antennas, and resistors. The ink is printed on a flexible or rigid substrate to make a printed circuit, and an antenna printed with conductive ink can receive RFID-specific radio signals. Conductive ink saves the cost of RFID tags in two ways. First of all, from the material cost, the ink is cheaper than stamping or etching metal coils. Second, from the material consumption, stamping or etching consumes a lot of metal, and the conductive ink printing antenna or circuit has high speed and low cost. efficient. In the past, conductive inks were only screen printed. Today, they have been extended to offset printing, flexographic printing, and gravure printing. VI. Precautions for Label Printing Site Management There are many deficiencies in the label printing ink on the market. The most prominent problem is the ink hue deviation problem: on the one hand, the hue of the same ink produced by different ink manufacturers is different; on the other hand, even the same ink produced by the same manufacturer. Depending on the batch, the hue can deviate, sometimes even large. For this reason, printing companies often have to stop the commissioning, which is very detrimental to the stability of the printing quality, and brings great inconvenience to production, which seriously hampers the improvement of the quality of printed matter. We have repeatedly suggested that we use the same brand of ink produced by the same ink manufacturer to avoid the printing failure of different manufacturers and different types of inks. 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. Each deployment of the ink should not be too much, should follow the principle of "less add, ground plus", not only is conducive to the stability of ink performance, but also can effectively avoid waste; In addition, for spot color inks, should also be prepared to record. In the printing process, in order to ensure the quality of label prints and smooth production, certain additives such as anti-static agents, defoamers, and rewinders should be added to the ink. Note that the amount to be added must be controlled within the specified range. Inside. 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 following issues should also be noted during the storage and management of label printing inks: 1. Keep away from fire and heat sources when storing ink. It is best to maintain a constant temperature in the ink depot, and 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. 2. In the winter in the north, avoid storing the ink outdoors to prevent gelation. Once gelation occurs, it should be transferred to a warehouse with high temperature, or placed in hot water to restore insoluble matter to its original state. 3. The principle of "first in, first out" should be followed in ink storage and management. Ink also has a certain shelf life, the general shelf life of one year is appropriate If the storage is too long, the various components of the ink will be isolated, precipitation phenomenon. The remaining ink after printing must be sealed and stored in a dark place. Before reuse, filter it with a filter of 100 mesh or more, mix it well with new ink. 4. The label printing factory shall set up a special material management department responsible for the unified management of raw and auxiliary materials including inks, establish a sound material management system, formulate reasonable feeding and picking procedures, and implement strict storage. Delivery procedures. That is, the person responsible for the management of the ink, the partition storage of ink products, to avoid false leads, misuse. In addition, detailed records on the type, origin, batch, quantity, and use of inks are required to ensure product traceability. Seventh, conclusion Due to the diversified needs of the label products in aesthetics, anti-counterfeiting, and personalization, the advantages of comprehensive printing methods are the best choices for embodying the printing effects. Therefore, there will be more and more designs and applications of the combined presses with flat, convex, flexible, and net multifunction. This is also the direction of the development of label equipment manufacturers. Every company is facing more and more severe challenges. Tomorrow's market will put forward higher requirements for today's label printing: multiple printing process combinations, flexible and diverse production, new varieties, high printing quality, high production efficiency, and low Production costs, etc. These are new opportunities and challenges for label printing companies. For us ink manufacturers, the development and production of various types of label inks suitable for the market needs, is also the only way to survive and re-development.
Analysis of Label Printing and Printing (II)