Birefringence distribution in magneto-optical disk substrate fabricated by injection compression molding

Abstract

Shinill KangJong Sung KimHyun KimYonsei UniversityCenter for Information Storage Device134 Shinchon-dong, Seodaemoon-kuSeoul 120-749, KoreaE-mail: snlkang@yonsei.ac.krAbstract. It is necessary to improve optical and mechanical propertiesin optical disk substrates as information storage devices with high stor-age density using short-wavelength lasers are being developed. Injec-tion compression molding is regarded as the most suitable process tomanufacture optical disk substrates with high dimensional accuracy, lowresidual stress, and superb optical properties. Polycarbonate magneto-optical disk substrates are fabricated by injection compression molding,and the birefringence, regarded as one of the most important opticalproperties for optical disk, is measured. The effects of various process-ing conditions on the development of birefringence distribution are ex-amined experimentally. It is found that the values of the birefringencedistribution are very sensitive to the mold wall temperature history. Bycontrolling the compression process, the overall birefringence value canbe reduced.