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Abstract

A method for molding a substrate for use in supporting a magneto-optic recording structure includes the steps of providing a mold having a cavity that defines a plane and that is designed to form a thin disk-like magneto-optic substrate and mounting such mold with such plane horizontal and an axis of circular symmetry thereof substantially vertical. Hot fluid plastic flows from the center of such horizontal mold so that the fluid plastic flows relatively uniformly and radially outwardly from the center of the mold to minimize azimuthal variations in birefringence. Such flowing may be by injection or compression molding. Molding apparatus for manufacturing such magneto-optic substrate includes such mold and a support for positioning such mold with the plane thereof horizontal. Hot fluid plastic is injected to the center of such mold, as for example from the vertical axis of symmetry of such mold. With the plane of the mold horizontal and the hot fluid plastic flowing radially and symmetrically outwardly from the center of the mold, the fluid plastic moves substantially radially and uniformly through the mold. The magneto-optic substrate has relatively small azimuthal variation in birefringence.

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First Claim