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 instant drying, energy saving, space-saving, solvent-free, pollution-free, low odor and other advantages have been highly evaluated and are applied to various armored 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
The composition of UV inks and oil inks is shown in Table 1.
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.
Table 1 Composition of UV ink and oil ink
2 UV ink features
advantage
Fast drying, no crusting on the ink, no drying on the machine, no need for dusting, stacking of printed sheets, post-processing at once, abrasion resistance, heat resistance, solvent resistance, chemical corrosion, etc. Less · No decrease in density after drying · Infrequent change in ink · Special inks can be made
Shortcomings
· High ink price · Dots are easy to expand · The amount of water cannot be too high · Once the transferability of emulsified ink is extremely deteriorated · Not applicable for all PS plates · Not all the rollers are applicable · In many cases, ink is splashed · Sensitive to temperature changes · Papers with poor adhesive properties are mostly unsuitable. · The ink may gel. · The paper may crack easily. · The metal foil and the type of adhesive are selected. · The density of the black ink is insufficient. · The general cleaning agent cannot be used for cleaning.
From - China's printing market