PURPOSE: To prepare the titled resin composition having high refractive index, low chromatic abberation, and excellent abrasion resistance, transparency, etc., and suitable for eye glasses, camera lens, etc., by copolymerizing a halogenated styrene and a functional monomer having a naphthalene ring.

CONSTITUTION: A monomer mixture composed of (A) a halogenated styrene of formula I (X is halogen other than F; a is 1W5), e.g. o-chlorostyrene, (B) a functional monomer having a naphthalene ring and represented by formula II (R1 is H or methyl; R2 is 1W6C alkyl or halogen other than F; m, m', and n are 0W4), e.g. monochloronaphthalene ethoxymethacrylate, and pref. (C) a third component having an Abbe number of ≥30, e.g. 2,2-bis(4-methacroyloxyethoxyphenyl)propane, is subjected to the preliminary polymerization, cast in a lens mold, and cured.

EFFECT: Processability, dyeability, etc. are also good.