Hoechst Aktiengesellschaft

Kerdix, Inc.

Bernd F Fischer

Boris J Muchnik

Karl-Friedrich Doessel

Guenther Schmidt

Ernst G Schlosser

A magnetooptic layer made from rare-earth metals and transition metals exhibits a gradient in the alloy composition over the layer depth, and has a coercive field strength of more than 8 kOe in the temperature range of .DELTA.T=100.degree. C. around the compensation temperature T.sub.comp. The layer is fabricated with a dynamic sputter process, in which the substrates to be coated are led past one or a plurality of sputter targets, arranged in a common plane parallel to the track of the substrates. A mask is located between the sputter targets and the substrates.

Magnetooptic layer and a process for its fabrication

Apparatus for molding a substrate for use in supporting a magneto-optic recording structure includes a mold having a cavity that defines a plane and that is designed to form a thin disk-like magneto-optic substrate. The mold is mounted 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 horizontally and relatively uniformly and radially outwardly from the center of the mold to minimize azimuthal variations in birefringence. Such flowing is by injection molding. The molding apparatus for manufacturing such magneto-optic substrate includes 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 horizontally radially and symmetrically outwardly from the center of the mold, the fluid plastic moves substantially horizontally radially and uniformly through the mold. The resulting magneto-optic substrate has relatively small azimuthal variation in birefringence.

Apparatus for molding magneto-optic substrates

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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Wiesbaden, Germany

Bernd F Fischer