It has been more than 30 years since the UV printing ink cured by irradiation with a UV lamp reached practical use today. Compared with traditional oil-based inks, its advantages of instant drying, energy saving, space saving, solvent-free, pollution-free and low odor have been highly evaluated and applied to various packaging products. Especially in the work efficiency, environmental protection, print corrosion resistance is recognized, and there are many applications in offset and flexo. This article discusses UV inks and UV varnish in the field of packaging and printing.
1 composition of UV ink
Comparing the composition of UV inks and oil inks, UV inks that cure instantly upon UV irradiation produce radically oily inks that rely on solvents that permeate paper for several hours of oxidative polymerization and dry by ordinary oily inks and solvents and water. The water-based ink that is evaporated and added to the paper to dry is different from the water-based ink except that the pigments are the same. If you want to make a brief description of the UV ink curing mechanism, it is that the photoinitiator in the UV ink absorbs the ultraviolet light of the UV lamp to generate a radical group. The group is converted into monomers, and the monomers are further obtained. This polymerization reaction proceeds continuously to form a hard ink film, which is an instant drying method.
2 Features of UV ink
â— Fast drying â— The ink does not become crusted â— Does not dry on the machine â— Does not require dusting â— Sheets can be piled up â— Can be post-processed immediately â— Resistant to abrasion, heat, solvents, chemicals, etc. â— Odors of prints Less â— Density does not decrease after drying â— Ink changes rarely â— Can be made into special inks Disadvantages â— High ink price â— Easy to expand outlets â— Water should not be too large â— Extremely deteriorated transferability of emulsified inks â— Not applicable for all PS plates â— Not suitable for all rubber rollers â— Many cases of ink splashes â— Sensitive to temperature changes â— Papers with poor adhesive properties are not suitable for most applications â— Gels are sometimes produced in ink â— Paper is easily cracked â— Metal foils and adhesives are picked Agent type â— Insufficient density of black ink â— Cannot be cleaned with general cleaning agent
3 UV ink (gloss) and application
1) Offset UV ink
When a sheet-fed offset press uses oil-based ink to print non-absorbent substrates or thick paper, it requires a lot of dusting and the use of a delivery separator in order to prevent the backside from sticking. UV ink can achieve instantaneous drying, no need to spray powder, you can pile up printed products, immediately into the post-processing, do not have to worry about the back of the sticky problem, the ink film hardness, emissions of odor is very small, does not contain VOC components, for Environmental protection is beneficial. UV inks are popularized by centering on packaging and printing, and have many applications in the printing of food packaging and cosmetics packaging using cardboard, polyethylene coated paper.
Compared to the oil-absorbing ink headache non-absorbent substrate, due to the UV ink has the characteristics of instant curing, in a metal foil, holographic film, synthetic paper printing; 2PP video box printing, packaging machine 'target = _blank> transparent film printing; 3PP, PVC, APET, PET, PS Polycarbonate Transparent packaging printing has more applications, especially PVC cash cards, credit cards or PET prepaid cards (phone cards, orange cards, rewrite cards, highway cards) cards Card printing has been widely used.
Since UV inks are compatible with the above applications, there are many varieties of UV inks used in offset printing, such as fast-drying, low-odor type UV inks for paper, inks with good film adhesion, and environmentally friendly SOY certified inks and markets. Corresponding UV hybrid inks and the like are required. Among them, the application of UV mixed inks in printing has attracted much attention in recent years. When the oil-based ink and the UV-varnish oil are used in combination on a printing lacquer production line, the gloss of the print gradually decreases due to the penetration and drying of the oil-based ink. To solve this problem, UV hybrid inks were introduced. The UV mixed ink can be used with cleaning agents and ink rollers used in oil inks. It is an ink with good compatibility. The printed paper can be recycled and has printability and reproducibility close to that of oil inks. In use can be more smoothly from the use of oily ink conversion. UV curing inks used in recent years have been improved in their UV curing performance. Due to poor abrasion resistance compared with ordinary UV inks, it is an issue faced by ink manufacturers in the future how to combine the curing performance of UV inks with the good printability of oil inks.
UV special ink, UV gold and silver ink, UV fluorescent ink, UV invisible light (infrared light, ultraviolet light) color ink, UV pearl ink, UV waterless ink, etc. have applications in the packaging field.
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