Definition, characteristics and application of UV

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Definition, characteristics and application of UV glazing oil for paper printing

1 what is printing glazing

the so-called printing glazing is to reprint once or twice with a field plate or a graphic plate on the surface of a replica that has completed graphic printing, so as to obtain a bright UV film on the surface of the print. Printing glazing can enhance the light resistance of the ink, increase the heat and moisture resistance of the ink layer, and play a role in protecting the imprint, beautifying the product, and replacing the film

compared with film coating, printing and glazing is not only cheap and simple, but also can be full version glazing or local glazing

2 characteristics of UV glazing oil for paper printing

uv glazing is a method of curing glazing paint by UV (abbreviation of ultra violet, namely UV). It has the characteristics of rapid curing and low-temperature curing of paint, which is helpful to solve many problems in the gloss processing of paper printing. Therefore, it has been widely used in the gloss processing of paper containers, trademarks, seals, pictures, tape envelopes and other printing materials. In foreign countries, UV glazing is widely used for glossy processing of the covers of books, periodicals and magazines

uv glazing is rising rapidly and has the potential to replace plastic coatings and solvents in many products. As for rough fracture zone glazing, this mainly depends on its own characteristics:

1) UV glazing oil contains almost no solvents, and the emission of organic volatiles is very small, so it reduces air pollution, improves the working environment, and reduces the risk of fire

2) UV varnish does not contain solvent, and does not need heat energy during curing. The energy consumption required for curing is only about 20% of that of infrared curing ink and infrared curing varnish. In addition, this kind of varnish has strong affinity for ink and firm adhesion, with ultraviolet radiation of 80 ~ 120W/cm. The curing speed can reach 100 ~ 300m/min under light irradiation

3) the color of the printed matter treated by UV glazing process is obviously bright and bright compared with other processing methods, and the cured coating is wear-resistant, more drug-resistant and chemical resistant, with good stability, and can be scrubbed with water and ethanol

4) UV varnish has high effective components and less volatilization, so the dosage is saved. Generally, the coating amount of varnish on coated paper is only about 4G/m2, and the cost is about 60% of the coating cost

5) it can avoid the common defects of plastic coating process, such as edge warping, blistering, wrinkling, delamination and so on. UV glazing products do not adhere, and can be stacked after curing, which is conducive to post process processing operations such as binding

6) can be recycled. It solves the problem of environmental pollution caused by the non recycling of plastic composite paper base

at present, a small amount of UV glazing oil on the domestic market is imported from Europe and the United States, and most of it is produced in Taiwan

3 composition and type of UV glazing oil UV glazing oil is made of UV photosensitive resin, photoinitiator, active monomer and additives through scientific compound processing. UV glazing oil can be divided into UV glazing oil for UV ink, UV glazing oil for oily ink and both types of UV glazing oil. It can also be divided into off-line UV glazing oil, on-line UV glazing oil or both types of UV glazing oil according to the coating processing method

4 application of UV glazing oil for paper printing

uv glazing oil can be widely used in off-line glazing of roller (roll coating) coaters, gripper coaters, gravure coaters and flexo coaters

high efficiency roll coater for thick paper is composed of rollers rotating in the same direction. It can be divided into many models according to different combinations of rollers and different central line angles between rollers. The gripper coater is suitable for paper with specifications of 80 ~ 120g/m2; Gravure coater and flexo coater are mainly local coating. Gravure coater coating can make the local image bright and the coating uniform. However, the coating amount can only be adjusted by dilution. As long as the number, depth and shape of gravure lines are not changed, the coating amount cannot be increased or decreased. When flexo coating, the image edge is easy to produce edge contour, which is lack of sharpness. However, the adjustment and revision of coating amount are relatively easy

after coating with any of the above coaters, it is generally necessary to use a hot-air oven or infrared oven to volatilize the solvent, and then cure it with ultraviolet light. When the paper is coated with UV varnish, the offline mode of printing first and coating varnish during post-processing can be adopted, and the processing speed is generally M/min

uv glazing oil online glazing mainly includes the following three ways:

1) blanket coating of offset printing machine, with a processing speed of 7000 ~ 9000 sheets/h

2) the last unit of gravure rotary printing machine is coated, and the processing speed is 100 ~ 200m/min

3) the final unit of flexographic printing machine and special coating machine are coated, and the processing speed is 100 ~ 200m/min

5 several problems that should be paid attention to when using UV varnish

1) light source. UV irradiation light source generally adopts high-pressure mercury lamp or metal halide lamp (electrodeless lamp is preferred), and the power of the light source also requires stability. The output power of high-pressure mercury lamp is generally 80 ~ 120W/cm, so as to ensure the curing speed of UV coating of 0.5s

2) paper uvpaint is not suitable for processing paper that is easy to penetrate. Because the low molecular materials in UV paint are easy to penetrate into the paper, causing the paper to darken or even soak. In this case, only to speed up the printing speed and increase the number of tubes. In order to prevent penetration, the bottom layer can be coated with infrared primer first to avoid penetration when coating uvpaint

3) ink. Pay attention to the combination of UV paint and ink, and apply a layer of primer first if necessary

4) coating. After UV radiation, the photoinitiator of the polished coating is initiated to produce free radicals or ions, which cross-linked with the double bonds in the prepolymer or unsaturated monomer to form monomer groups. These monomer groups turn on the chain reaction to produce polymer solid polymers, and complete the drying process of glazing paint. The coating layer is too thick, and the drying time is relatively long under the irradiation of the same power light source. On the one hand, it affects the drying of UV varnish, on the other hand, it relatively reduces the water content of the paper, which will make the paper brittle and easy to break, and affect the wear resistance of UV oil layer

5) diluent. UV glazing oil generally needs to use a special diluent, and the dilution is controlled at about 1:0.5 to 1:1. Too much will affect the glazing effect (depending on the amount of film)

6) poor gloss. ① If the paper quality is poor or the surface is rough, and the oil absorption is large, you should use a higher grade paper; ② If the coating is uneven or the polish is diluted too thin, and the viscosity is too low, the polish machine should be adjusted and the viscosity of the Polish should be increased

7) poor adhesion. ① If the crystallization of printing ink layer or the improper use of ink additives and antiskid agents, the printing process should be improved, and the ink additives should not be used or used less; ② If the viscosity of glazing oil is too low, adjust the glazing machine and improve the viscosity of glazing oil; ③ Improper type of UV varnish

8) the upper gloss layer is white and the crosslinking density is low. ① The diluent is not used properly. Because the alcohol solvent volatilizes rapidly in summer, the diluent should be replaced or replaced with ester diluent or special diluent

9) the coating layer is yellowish. ① If the polish coating is too thick and the viscosity is too high, the viscosity should be reduced; ② When the Polish expires (the service life is generally 6 months), it should be stopped

10) adhesion (incomplete drying). ① If the coating is too thick, the viscosity should be reduced; ② The UV lamp has insufficient power or aging (the service life of the UV lamp is generally about 800 hours, and the curing efficiency will be reduced after this time). The UV lamp should be replaced to reach the rated power; ③ The polish has expired and should be stopped

11) poor smoothness. If the coating roller of the glazing machine is damaged or the viscosity of the glazing oil is high, replace or regrind the roller to reduce the viscosity of the glazing oil

12) safety production. Some imported UV glazing oils are irritating to the skin, plus they are non-volatile, which is harmful to the skin. When the clothes are attached, if it is hot in summer, it may enter the skin with sweat and cause inflammation. Therefore, if the skin is stained with u "V Polish during the production process, wash it with soapy water as soon as possible and change the clothes in time

in addition, attention should also be paid to the temperature and humidity control of the environment and the hot stamping property of paper prints after UV polish

6 conclusion

uv curing technology has been widely used since its invention in the 1960s until the end of the 20th century when 2utm experimental machine includes one or more vertically loaded columns. In China, UV printing and UV glazing have been widely used in packaging and printing fields such as aluminum foil and aluminum foil cardboard printing, magnetic card printing, commercial printing, metal printing, food, medicine, cigarette packs, self-adhesive, etc. UV paper products glazing is increasing by more than 10% every year, so the application prospect of UV glazing oil is very broad

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