Shadow-less adhesive, also known as photosensitive adhesive and ultraviolet curing adhesive, is a kind of adhesive that can only be cured by ultraviolet radiation. It can be used as adhesive and glue for paint, coating and ink. The curing principle of shadowless adhesive is that the photoinitiator (or photosensitizer) in UV (ultraviolet) curing material absorbs ultraviolet light under the irradiation of ultraviolet light, generates active free radicals or cations, and initiates the chemical reaction of monomer polymerization, crosslinking and grafting, so that the adhesive changes from liquid to solid in a few seconds.