Abstract
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.
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