Abstract: To form a disk substrate 42 having a no information area at low cost and without failure, a mold 12 is provided for forming a disk substrate 42 having a no information area 44. A cavity 32 of the mold 12 has a surface 50 corresponding to the no information area 44 and made of a mirror-surfaced plate 22. A cylindrical member (sleeve 35) is inserted in an inner hole 38 of the mirror-surfaced plate 22. An annular projection 33 is provided on the end surface of the cylindrical member adjacent to the cavity.

Abstract: The present invention aims at increasing service life of an inner circumferential stamper holder in a die for molding disc substrates that is used when the disc substrates are injection molded. To that end, in the die for molding the disc substrates in which a stamper 3 is supported by at least one of a stationary die 6 and a movable die 1, an abrasion resistant treatment is applied to at least a portion, which abuts against a side surface 3a of a center opening of the stamper 3, of an outer circumferential surface 4a of the inner circumferential stamper holder 4 supporting the stamper 3.

Abstract: It is an object of the present invention to provide a die assembly for molding optical disc substrates, wherein formation of a burr perpendicular to a reading surface that is opposite to a signal surface of each optical disc substrate can be prevented and two signal surfaces can be bonded together satisfactorily. To that end, in a die assembly for molding optical disc substrates that comprises an outer circumferential stamper holder 25 having: a stamper holding portion 34 that holds an outer circumferential edge portion 26E of a stamper 26 disposed on a specular plate 24; and an inner circumferential portion 33 that defines an outer circumferential end 27E of a molding cavity 27, the inner circumferential portion 33 of the outer circumferential stamper holder is provided with a projecting portion 35 having an acute cross-section that consists of a smooth surface projecting into the molding cavity 27 toward the stamper holding portion 34.

Abstract: A die for molding disc substrates, includes, in a stamper, a to-be-held surface that diverges continuously from an inner circumferential surface of a center hole. An inner stamper holder holding the inner circumferential side of the stamper includes a cylindrical body and a claw including a cavity forming surface substantially parallel to the inner circumferential side head surface, and a holding surface diverging tapered toward the cavity holding the to-be-held surface. In the cylindrical body portion, a cylindrical surface that is opposed to the inner circumferential surface of the stamper. The die prevents the claw of the inner stamper holder from projecting from a transfer surface of the stamper and solves a problem of insufficient strength of the inner circumferential side of the stamper.

Abstract: To improve a bad appearance due to an interconnection between a pair of disk substrates (20, 30) which are bonded with annular grooves (25, 35) being opposed to each other by a simple structure and at a low cost, which have annular grooves (25, 35) near their center openings (15), an outer groove end (26) of the annular groove (25) of one disk substrate (20) in the radial direction is registered in position with an outer end (36) of the annular groove (35) of the other disk substrate (30) and inner groove ends (27, 37) of the annular grooves in the radial direction are located in different positions. The annular grooves have different groove widths A, B.

Abstract: The present invention provides a stamper holding mechanism that is stable, cannot be loosened, that does not use frictional forces and is not affected by vibration and temperature variations. To that end, there is provided a die, for molding disc substrates, that forms a cavity 23 by providing a stamper 10 on either one or both of a stationary mirror plate 8 of a stationary die 1 and a movable mirror plate 16 of a movable die 11, including: rotation mechanism for allowing a holding member, which holds the stamper 10 on the mirror plate and which can be removable, to advance or retreat; and engagement mechanism for abutting on the rotation mechanism to be engaged therewith in a direction to remove the holding member when the rotation mechanism is rotated in the direction.

Abstract: It is an object of the present invention to provide a die assembly for molding optical disc substrates, wherein formation of a burr perpendicular to a reading surface that is opposite to a signal surface of each optical disc substrate can be prevented and two signal surfaces can be bonded together satisfactorily. To that end, in a die assembly for molding optical disc substrates that comprises an outer circumferential stamper holder 25 having: a stamper holding portion 34 that holds an outer circumferential edge portion 26E of a stamper 26 disposed on a specular plate 24; and an inner circumferential portion 33 that defines an outer circumferential end 27E of a molding cavity 27, the inner circumferential portion 33 of the outer circumferential stamper holder is provided with a projecting portion 35 having an acute cross-section that consists of a smooth surface projecting into the molding cavity 27 toward the stamper holding portion 34.

Abstract: The present invention aims at increasing service life of an inner circumferential stamper holder in a die for molding disc substrates that is used when the disc substrates are injection molded. To that end, in the die for molding the disc substrates in which a stamper 3 is supported by at least one of a stationary die 6 and a movable die 1, an abrasion resistant treatment is applied to at least a portion, which abuts against a side surface 3a of a center opening of the stamper 3, of an outer circumferential surface 4a of the inner circumferential stamper holder 4 supporting the stamper 3.

Abstract: To form a disk substrate 42 having a no information area at low cost and without failure, a mold 12 is provided for forming a disk substrate 42 having a no information area 44. A cavity 32 of the mold 12 has a surface 50 corresponding to the no information area 44 and made of a mirror-surfaced plate 22. A cylindrical member (sleeve 35) is inserted in an inner hole 38 of the mirror-surfaced plate 22. An annular projection 33 is provided on the end surface of the cylindrical member adjacent to the cavity.

Abstract: There is provided a die 1, for molding disc substrates, wherein, in a stamper 20, a to-be-held surface 33 that diverges continuously from an inner circumferential surface 32 of a center hole 31 is formed between the inner circumferential surface 32 and an inner circumferential side head surface 34 by punching the center hole 31, an inner stamper holder 16 that holds the inner circumferential side 20a of the stamper 20 includes a cylindrical body portion 41 and a claw portion 42, in the claw portion, a cavity forming surface 43 that is substantially parallel to the inner circumferential side head surface 34 of the stamper 20 and a holding surface 46 that diverges toward the cavity in a tapered fashion and holds said to-be-held surface 33 are formed, and, in the cylindrical body portion 41, a cylindrical surface 47 that is opposed to the inner circumferential surface 32 of the stamper 20 is formed.

Abstract: The present invention provides a stamper holding mechanism that is stable, cannot be loosened, that does not use frictional forces and is not affected by vibration and temperature variations. To that end, there is provided a die, for molding disc substrates, that forms a cavity 23 by providing a stamper 10 on either one or both of a stationary mirror plate 8 of a stationary die 1 and a movable mirror plate 16 of a movable die 11, including: rotation mechanism for allowing a holding member, which holds the stamper 10 on the mirror plate and which can be removable, to advance or retreat; and engagement mechanism for abutting on the rotation mechanism to be engaged therewith in a direction to remove the holding member when the rotation mechanism is rotated in the direction.

Abstract: A method of releasing thin discs during molding forms discs with a central aperture with a thin gate connecting the molded disc to a sprue. A male cutter advances under pressure control of an actuator operating the male cutter and implements releasing of the molded discs from the surfaces of a stamper and a mirror plate during mold closing. The molded disc and the sprue are ejected by a center pin in the mold opening operation.

Abstract: A disc base molding method and apparatus are provided for the injection molding of disc bases so as to produce thin disc bases having increased signal transfer clarity with a shortened molding cycle. Upon closure of a mold, a signal is sent to a mold clamping start delay timer and an injection start delay timer. Pressure is increased for mold clamping at approximately the same time that molten resin is introduced into the mold cavity. The time period from the start of pressure increase when the molten resin is initially introduced to the mold cavity until a specific mold clamping force is reached, is controllable. Upon completion of the injection of the molten resin, the mold clamping force is maintained until the molten resin is solidified.

Abstract: A process of manufacturing the optical discs by injection molding includes compulsive forced cooling of the molded discs, carried out after sputtering to shorten the cooling time in the mold, in consideration of keeping the replication errors in the pits on the molded discs. The process also includes metallizing the surface of the molded discs by sputtering (to make laser beams reflect). UV resin coating for protecting the metallized surface of the discs, and inspecting the pits for replication of information signals quality.

Abstract: A disc base formed concentrically in the recited order from its center opening to its outer circumferential edge with clamp areas on its two faces, a groove by a stamper holder and a signal area both leading from one of the clamp areas on its one face, and a stack rib on its other face. The diameter of the concentric circuit of the top of the stack rib is slightly larger than the diameter of the concentric circuit of the groove formed by the stamper holder, and the angle of the outer slope of the stack rib is larger than the angle of the inner slope of the same. Also disclosed is a mold for molding the disc base.