Patent ID: 7566745

Claim:
A photochemically refractive-index-changing polymer wherein the polymer is one of (a) a homopolymer comprising an acrylic vinyl monomer represented by the following formula (1): CH 2 ═C(R 1 )C(═O)O—R 2 ═CH 2 (1) wherein R 1 is a hydrogen atom or a methyl group and R 2 is a saturated hydrocarbon group having 1-20 carbon atoms, provided that the monomer may have one or more heteroatoms and one or more halogen atoms in the monomer, and (b) a copolymer comprising two or more acrylic vinyl monomers represented by formula (1), or (c) a copolymer comprising one or two or more acrylic vinyl monomers represented by formula (1) and one or more monomers other than the acrylic vinyl monomers, wherein the polymer has a radical-polymerizable side-chain vinyl group remaining in the monomer and, upon irradiation with a radiation, undergoes a refractive-index increase (Δn) through the irradiation of 0.005 or more, as measured by the m-Line method in the TE mode, the polymer has a number-average molecular weight of 20,000 or higher, and the polymer has a stereoregularity of 70% or higher in terms of syndiotacticity (rr).