Kenji Manabe

Molding Compounds For Optical Disk Substrates

Birefringence is generally caused by the orientation of the optical anisotropic molecular chain introduced during the injection molding of plastic substrates. It was found that the degree of birefringence of molded disk depends on the value of the difference between the polarizabilities parallel and perpendicular to the molecular chain. This difference in polarizabilities is proportional to the optical elastic constant of the polymer in the elastic state. It was determined that the negative and positive segmental polarizabilities may be fully compensated by mixing two polymers with opposite molecular optical anisotropy in an optimal ratio. Using this method an injection molded substrate was developed which demonstrated minimal birefringence.