Kazuyoshi Shigematsu

Refractive Index Anisotropies of Constructive Units in Polycarbonates

The following methods were considered for decreasing refractive index anisotropies (RIA) of constructive units in bisphenol-A polycarbonate: 1) Substitution of side-chain methyl groups with atomic groups of large RIA to cancel those in constructive units. 2) Substitution of side-chain methyl groups by other alkyl groups to change conformations of main-chain phenyl groups in constructive units. Utilizing the above methods, polycarbonate systems with constructive units with low RIA were obtained.

Refractive Index Ellipsoids of a Polyformal Magneto-Optical Memory Disk Substrate

To investigate the generating mechanism of optical anisotropy in a polycarbonate (PC) magneto optical memory disk substrate, refractive index ellipsoids were measured for as-molded and annealed disk substrates. The shape of the refractive index ellipsoid for the as-molded disk substrate was muffin-shaped; that is, the thickness direction was substantially smaller than the other directions. Even after an annealing process to remove residual stress in the disk substrate, the shape of the ellipsoids remained anisotropic and muffin-shaped. This fact suggests that the molecular orientation of constructive units with anisotropic refractive indices is mainly responsible for the optical anisotropy in this PC substrate.

Stress-Optical Coefficients in Polycarbonates

Stress-optical coefficients in the glassy state (Cg) were measured in polycarbonates (PCs), and mechanisms of birefringence production by stress and relationships between Cgs and chemical structures were discussed.

Refractive Index Ellipsoids of a Modified Polycarbonate Magneto Optical Memory Disk Substrate

The refractive index ellipsoids (RIE) of a magneto optical memory disk substate made by a modified polycarbonate, in which the refractive index anisotropy (RIA) of the constructive units is 1/4 of that for bisphenol-A-polycarbonate (BisAPC), were measured. Similar to the RIE of the BisAPC disk substrate, the RIE of this disk substrate were muffin-shaped; that is, the thickness direction was substantially smaller than the other directions, and its RIA was almost 1/2 of that for BisAPC.1)

Optical Anisotropies in Modified Polycarbonates

A new series of modified polycarbonates were prepared by the substitution of ortho hydrogen (for carbonate group) of main chain phenyl group by methyl, phenyl and cyclohexyl groups. The relationships between chemical structures and stress-optical coefficients in the glassy state (Cg), refractive index anisotropy of constructive units (RIAC) and molecular motions were investigated in these systems.