Optical Disc Corporation

Discovision Associates

Mca Disco-vision, Inc.

John R Holmes

Richard L Wilkinson

John H Rilum

Carlyle J Eberly

Roy G Jordan

Improvements in the shape of three-dimensional features displayed in optical recording structures, particularly in such structures displaying features of differing dimensional characteristics. The shape improvements include reductions in berm height and width, dual level data marks and tracking guides, and land areas projecting above or into the surface of the recording structure.

Configuration of three-dimensional features in data recording structures

A method to produce improvements in the shape of three-dimensional features displayed in optical recording structures, particularly in such structures displaying features of differing dimensional characteristics. The shape improvements include reductions in berm height and width, dual level data marks and tracking guides, and land areas projecting above or into the surface of the recording structure. The method includes dual and/or dithered beam writing onto the structure and improved composition of the active layer of the structure.

Method of producing improved three-dimensional features in data recording structures

Disclosed are improvements in the transverse sectional shape of three-dimensional features displayed in optical recording structures&mdash;discs, cylinders, cards, multi-layered devices and structures replicated from them&mdash;to increase Figure of Merit. The cross-sectional shape improvements include reductions in berm height and width, dual level data marks and tracking guides, and land areas projecting above or into the surface of the recording structure. Disclosed methods include dual and/or dithered beam writing onto the structure and improved composition of the active layer of the structure. Also disclosed are apparatus for producing such improved features on optical recording structures, according to one or more of the disclosed methods.

Figure of merit in optical recording structures

A video disc member is described having a uniform value of birefringence over the entire information storage surface of the disc. This value of birefringence is the same at the inner information storage radius as at the outer information storage radius. The preferable composition of the video disc is a specially prepared polymethylmethacrylate, referred to as PMMA. The method of molding the improved video disc member includes an extended drying time for said composition and increasing the melting temperature. The increase in melt temperature provides a low and uniform value of birefringence. The improved drying cycle eliminates splay marks, blisters and other surface imperfections as compared to manufacturer recommended drying times.

Method for making a video disc

An injection molding apparatus for use in producing centrally-apertured video disc records. The apparatus includes first and second mold halves reciprocally movable with respect to each other between a closed position, wherein the two mold halves are in proximity to each other and molten plastic material is injected into a planar, annular cavity defined therebetween to form the record disc, and an open position, wherein the two mold halves are spaced apart from each other and the molded record disc can be removed. The molding apparatus further includes first and second annular rings carried by the respective first and second mold halves and defining the outer perimeter of the cavity. Each ring has an abutment face for compressive engagement with the abutment face of the other ring, when the apparatus is in the closed position, and one of the rings includes a plurality of spaced, radially-aligned grooves in its abutment face, defining ports for venting air from the cavity when the molten material is injected therein. The first mold half includes two plates reciprocally movable with respect to each other, with a plurality of compression springs in the form of polyurethane blocks interposed between the two plates, to bias the two annular rings into compressive engagement with each other when a central aperture is being punched in the molded record disc. When the apparatus is in the closed position, the two mold halves are aligned with respect to each other by a plurality of frusto-conical posts mounted on one mold half and conformably received by corresponding recesses formed on the other mold half, such posts and recesses not being subject to wear from sliding friction when the apparatus is moved, reciprocally, between the closed and open positions.

Apparatus for producing centrally apertured record discs

Heated material is injected into an annular cavity, defined by a pair of mold halves, through a sprue passage, defined by a sprue bushing and an end portion of a punch. The annular cavity and the sprue passage form, respectively the centrally apertured part and a sprue. After partial cooling of the heated material, the punch is locked in place while the annular cavity is displaced relative to the sprue passage so that the sprue is severed from the part along the peripheral surface of the punch end portion. The mold halves are separated to open the annular cavity while the sprue is resting on the punch end portion, and while the part is held by the punch end peripheral surface. After the mold halves are separated, a sprue ejector member is actuated to eject the sprue from the punch end portion. The finished video disc is then removed, carried by the moving platen of the moving mold assembly.

Method and means for replicating centrally apertured video disc records

Heated material is injected into an annular cavity, defined by a pair of mold halves, through a sprue passage, defined by a sprue bushing and an end portion of a punch. The annular cavity and the sprue passage form, respectively, the centrally apertured part and a sprue. After partial cooling of the heated material, the punch is locked in place while the annular cavity is displaced relative to the sprue passage so that the sprue is severed from the part along the peripheral surface of the punch end portion. The mold halves are separated to open the annular cavity while the sprue is resting on the punch end portion, and while the part is held by the punch end peripheral surface. After the mold halves are separated, a sprue ejector member is actuated to eject the sprue from the punch end portion. The finished video disc is then removed, carried by the moving platen of the moving mold assembly.

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Garden Grove, CA, United States of America

John R Holmes