UV ink application

UV inks (coatings) can be used regardless of the printing method (flexo, offset, gravure, screen printing). The use of flexo and offset printing has rapidly increased. The advantages of UV inks include the high speed of printing, the increase in the added value of printed products, the expansion of the printing market, the favorable environmental protection, and the good economy.

1 advantages of UV printing

1) The printing material for high-speed UV inks consists of liquid monomers and oligomers that cure instantaneously under UV light irradiation, unlike solvent inks that volatilize solvents by infiltrating the substrate or blowing hot air. To achieve drying. The printed ink will remain as it is after printed on the substrate, without shrinkage and deformation.
When UV light is irradiated, the photopolymerization initiator in the ink is activated and its energy initiates polymerization of the monomer. Since the polymerization reaction is completed instantaneously, drying is instantaneously achieved, and printing speed can be increased.

2) The increase in the added value of printing Because of the "homogenization" of printing technology (the level of technology and the quality of the products of the printing company have reached the same level), no matter which printing company can print out the same quality of printed matter, it will be printed out. Characteristic prints are a difficult job. Since UV inks (varnishes) remain printed after being printed on substrates, gloss and surface finishes can be improved, resulting in beautiful and beautiful prints. Employers will also hope to make prints that are different from other companies in the industry.

The use of UV varnish prints has a very good gloss or varnish effect, but also has the effect of protecting the printed product, which can increase its service life, thereby increasing the added value of the printed product. UV glazing can make printing products have the characteristics of wear resistance, water resistance, alcohol resistance, oil resistance and so on, which can protect the printed products. In addition, the coefficient of friction can be reduced by glazing to make the print product smoother.

3) Expansion of the printing market Since UV inks can be dried without having to penetrate into the substrate, they can also be printed on non-absorbent substrates. For printing such as plastic (styrene, PE, etc.) printing, foil printing, composite film, etc., printing by the conventional method may decrease the adhesive property or drying property and may not be printed. UV printing does not have these problems.

4) Environmentally friendly solvent-based inks release VOCs (Volatile Organic Compounds) and cause photochemical smog and suspended particles. Laws and regulations such as the Law on the Prevention and Control of Atmospheric Pollution also include the printing industry as a management object. Of course, VOCs have an impact on the health of printers. As long as you do not completely stop using solvent-based inks, these problems cannot be solved. Since UV inks do not contain VOCs, they are a good ink from an environmental point of view.

5) The price of economical UV inks is still high compared with ordinary inks. On the other hand, the UV ink system is economical. For example, UV lamps are cheaper than those that use thermal drying. From the perspective of reducing the floor space (equivalent to lowering the cost), it is more economical. In addition, satisfactory results are obtained when UV coating is applied once, and the efficiency is significantly improved compared to multiple coating methods.

2 Hybrid UV ink

The vehicle component of the UV ink includes a monomer, an oligomer, and a photopolymerization initiator, and an oily resin is added thereto to become a hybrid UV ink. UV printing is divided into two ways: using pure UV ink and using hybrid UV ink. Hybrid UV inks have many advantages of UV inks, but also have unique advantages: lower ink costs; can use the original ink roller, blanket and fountain solution; only a few UV lamps; odor less. When using UV ink, the ink roller, blanket, fountain solution, etc. must be UV-specific, UV ink will damage the ordinary ink roller or blanket, ordinary fountain solution can not be used with UV ink, hybrid UV ink can Use the original ink roller and blanket. Although no damage to the ink roller is possible because the UV ink composition is mixed therein, printing can be performed normally. When using pure UV ink, the UV lamp must be installed after each unit. To use the mixed ink, set a UV lamp only after the four-color printing, and set three UV lamps after the coating process. The next color printing (wet pressing wet) can be performed when the previous color of the hybrid ink is used, and the entire color ink is printed and then cured using a UV lamp.

Recent UV lamp improvements have reduced the odor of UV inks. Although there are still odors, they are not so odorous. Prints with odors sometimes cannot be used as commodities, for example, food related foods. UV inks are difficult to establish in these respects.

Hybrid UV inks still retain the advantages of UV inks in many ways, such as rapid drying. Drying of the ink film is slower than UV ink. However, since the drying of the ink film surface is instantaneous, there is no need to worry about dirt pick-up and high-speed printing can be performed.

There have been several methods of using a hybrid UV ink to express special effects, indicating that the ink can increase the added value of the printed product. In addition hybrid UV inks are less expensive than UV inks. Due to rapid drying, sheetfed offset presses can eliminate dusting operations.

The above introduced various advantages of UV inks, but UV systems still have some problems to be solved. For example, in the future, when UV inks are used, how can the price be reduced? Then there is the problem of odor and toxicity in UV inks. The UV system produces odors not only from the ink, but also from the UV lamp, but the odor comes mainly from the ink material. The main material involved—photopolymerization initiators—is not only odor but also toxic. Recently, with the advancement of technology, photopolymerization initiators having almost no odor have been developed. The reason why UV inks are expensive is because initiators are expensive, but initiators in UV systems are indispensable. However, the use of EB (electron beam) drying enables polymerization of the monomers even without initiators. This is due to the high energy of the electron beam, which allows direct transfer of energy to the monomer without the use of an initiator. The EB generating device is much more expensive than the UV lamp, thereby hindering its popularization and application. It is said that the EB device in the United States is about 1/10 of the UV system.

UV lamps have also been continuously improved, and it is expected that more efficient UV lamps will be produced. The improvements are improved, and the energy is greatly increased, and the fever is too small to meet the requirements.

The spectral radiation of the UV lamp is consistent with the spectral characteristics of the UV ink, and an effective curing effect is obtained. However, the characteristics of the UV ink are also changed when the type of the printing job is changed. Therefore, the drying is not always performed under optimum conditions. of. There are various UV devices that have been introduced, and everything is there, but its characteristics are consistent with the company’s product requirements. What kind of services are desired? It is necessary to investigate and understand in advance.

In addition, when using UV curing technology, we should also consider the possibility of using EB curing technology, I think this is the best policy.

(Translated by Yang Zhigang) Source: "Printing World"