OPTICAL RESIN COMPOSITION AND OPTICAL RESIN

PROBLEM TO BE SOLVED: To obtain an optical resin compsn. which can produce an optical resin having high refractive index and Abbe number and excellent in transparency and heat resistance by alkylsulfidizing a part of thiol groups of a polythiol compd. and converting the rest into thio(meth)acrylate groups. SOLUTION: This compsn. is a mixture of polymerizable compds. having on average 1.5-3.5 (meth)acryloyl groups per molecule and represented by formula I (wherein R1 is a group represented by formula II; R2 is 4C or lower alkyl or benzyl; R3 is H or methyl; and n is 0-3). The compsn. may further contain another polymerizable compd. [e.g. a (meth)acrylate compd. or a vinylphenyl compd.] copolymerizable with the foregoing compds. Photopolymn. with ultraviolet rays, whereby the curing is completed in a few seconds or minutes, is suitably used for the free-radical polymn. of the compsn. A free-radical initiator, i.e., a sensitizer, used here is not specifically limited, an example being 4- phenoxydichloroacetophenone.