Improved plastic molding technology for magneto-optical disk substrate

George J. Galic

doi:10.1117/12.25849

1 March 1991 Improved plastic molding technology for magneto-optical disk substrate

George J. Galic

Proceedings Volume 1396, Applications of Optical Engineering: Proceedings of OE/Midwest '90; (1991) https://doi.org/10.1117/12.25849
Event: Applications of Optical Engineering: Proceedings of OE/Midwest '90, 1990, Rosemont, IL, United States

Abstract

A patented new injection-molding technology which already has been coninercially licensed nonexclusively to worldleading plastic magnetooptical (MO) mediamakers gives very high moldpacking pressures (needed for maximum microsurface replication) without high birefringence (minimized by reducing constrictiveness during fill) even with high viscosity plastics. I . " STATFMENT OF ThE PROBLIM" FOB ERASABLE OPTICALDI 5K MOLDINQ Al though gl ass and new cross 1 inkabl e p1 as t i cs are cont ending wi th polycarbonate and other injection moldable thermoplastics for this new market polycarbonate has prevailed as " first generation" erasable media substrate (although product life considerations may require added barrier coat to the MO coating stacks thereof). If performance of all these substrate contenders were equal the injection moldable thermoplastics will be preferred due to lowest cost and most automatable production If molded thermoplastics don''t ultimately win out a main reason will have been that these disk products require a long narrow mold cavity to be filled by the thermoplastic of choice then packed at double the pressures used for digital audio compact disks (CDs) in order to force the molten thermoplastic against the staner microsurface until detailed microreplication is assured yet only very low moldedin stresses can be tolerated (typically 1/2 to 1/5 those of audio CDs) 1. 1 Fillrelated Molding Problems M-O disks typically are 130am or 86nin in diameter and as molded thickness of a single

Citation Download Citation

George J. Galic "Improved plastic molding technology for magneto-optical disk substrate", Proc. SPIE 1396, Applications of Optical Engineering: Proceedings of OE/Midwest '90, (1 March 1991); https://doi.org/10.1117/12.25849

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