Abstract: Photopolymerization initiator for the visible light-polymerizing adhesives; and the visible light-polymerizing adhesives comprising the photopolymerization initiator, an aliphatic tertiary amine and a radical polymerizing monomer. The visible light-polymerizing adhesive of the invention has good transparency without coloring after photopolymerization as well as good adhering activity. It also has colorless, good transparency after photopolymerization and good adhering activity in an UV irradiation test, as well as excellent light resistance showing very little color change and deterioration in an UV irradiation test. The visible light-polymerizing adhesive of the invention is also excellent in photopolymerizing activity. Furthermore, the visible light-polymerizing adhesive of the invention has photopolymerizing activity not only to visible light but also to near-UV. It hardly has problems of such decrease in transparency caused by both kinds of lights as coloring and color change.

Abstract: This invention relates to a photocuring adhesive characterized in that a photoinitiator is added to a monomer composition comprising 20 to 50 wt % of the oligosiloxanyl di(meth)acrylate represented by the structural formula (1) shown below, 20 to 60 wt % of a hydrophobic mono (meth)acrylate having a hydrocarbon group containing no less than six carbon atoms in a side chain, and 1 to 80% of a hydrophilic monomer capable of undergoing free radical polymerization: ##STR1## R.sub.1 and R.sub.2 both being either hydrogen or methyl, m.sub.1 and m.sub.2 being an integer in the range 2 to 5, and n being an integer in the range 5 to 30.