Abstract: A stamper for making a read-only optical disk includes an irregular pattern for forming embossed pits based on recording information and an irregular pattern for forming dummy irregularities. The irregular pattern for the embossed pits is arranged in a region corresponding to an information area for recording information in the read-only optical disk. The irregular pattern for the dummy irregularities is arranged in a region corresponding to an area between the information area and the outer periphery of the disk.

Abstract: A large capacity recording medium is formed by bonding at least two disc-shaped recording plates to provide a structure adapted to absorb any manufacturing errors in the direction of the height of the recording medium.

Abstract: A space 12 is formed at a tip portion of a nozzle 1 so as to decrease a thermal transfer of the nozzle 1. Alternatively, a center portion of one of a semi-spherically protruded surface of the tip portion of the nozzle 1 and a semi-spherically recessed surface of a sprue bush protrudes so that the radius of curvature of one semi-spherical surface is the same as the radius of curvature of the other semi-spherical surface. As a result, since the nozzle 1 and the sprue bush 2 are surface-contacted, heat of the tip portion of the nozzle 1 absorbed to the sprue bush 2 is increased. Thus, the temperature of the tip portion of the nozzle 1 can be lowered easily. After the resin material injected into the molding cavity 11 is cooled, when the sprue portion is removed from the fixed die, a tip portion of a rod-shaped protrusion portion of the sprue can be properly cut.

Abstract: A resin ring 51 is press-fitted into a grove portion formed in an inner periphery surface of an interlocking ring 4. The resin ring 51 is made of a hard resin such as Teflon. The resin ring 51 as a low frictional lubricative member is interposed between the interlock ring 4 and an outer periphery ring 3. In addition, a cavity 6 as a closed space is formed between a stamper 1b as a molding surface of a fixed side mirror 1 and a mirror side molding surface 2b of a moving side mirror 2. While the moving side mirror 2 is being press-contracted to the fixed side mirror 1, when a resin material is filled into the cavity 6, the outer periphery ring 3 is slidably held in a groove of the moving side mirror 2 with predetermined clearances. In the interlock ring 4, a plurality of openings 4a which relieve gas produced by the disc resin material filled into the cavity 6 are formed.

Abstract: A large capacity recording medium is formed by bonding at least two disc-shaped recording plates to provide a structure adapted to absorb any manufacturing errors in the direction of the height of the recording medium.

Abstract: A clamping apparatus includes a fixed die plate (21) fixed to a frame (26), four tie rods (23), (24) extending in the horizontal direction and respectively fixed to the fixed die plate (21) in parallel to each other, a moving die plate (22) supported to the four tie rods (23), (24) so that the moving die plate (22) can slide freely and a clamping mechanism for moving the moving die plate (22) forward and backward along the four tie rods (23), (24). This clamping apparatus comprises a guide mechanism (25) for downwardly or upwardly supporting the moving die plate (22) and which allows the moving die plate (22) to move in the opposite direction of gravitation.

Abstract: The present invention is directed to an injection molding apparatus and method capable of preventing the occurrence of over-packing. The apparatus includes a pair of dies for forming a plurality of cavities therebetween; die closing devices for closing the pair of dies under a prescribed pressure; an injection device for injecting a molten resin into respective cavities under a prescribed pressure; and, a control device for controlling the die closing devices and the injection device. Further, the apparatus comprises a plurality of pressure sensors for detecting respective pressures in respective cavities and a control device that controls the injection device and/or the die closing devices to reduce the rate of injection of the molten resin and/or the force of closing the dies and, otherwise, stops the injection and/or the die closing operation when the pressure difference between cavities is found to be greater than a prescribed value on the basis of sensed values from the respective pressure sensors.

Abstract: A space 12 is formed at a tip portion of a nozzle 1 so as to decrease a thermal transfer of the nozzle 1. Alternatively, a center portion of one of a semi-spherically protruded surface of the tip portion of the nozzle 1 and a semi-spherically recessed surface of a sprue bush protrudes so that the radius of curvature of one semi-spherical surface is the same as the radius of curvature of the other semi-spherical surface. As a result, since the nozzle 1 and the sprue bush 2 are surface-contacted, heat of the tip portion of the nozzle 1 absorbed to the sprue bush 2 is increased. Thus, the temperature of the tip portion of the nozzle 1 can be easily lowered. After resin material injected into the molding cavity 11 is cooled, when the sprue is removed, a tip portion of a rod-shaped protrusion portion of the sprue can be properly cut.

Abstract: A resin ring 51 is press-fitted into a grove portion formed in an inner periphery surface of an interlocking ring 4. The resin ring 51 is made of a hard resin such as Teflon. The resin ring 51 as a low frictional lubricative member is interposed between the interlock ring 4 and an outer periphery ring 3. In addition, a cavity 6 as a closed space is formed between a stamper 1b as a molding surface of a fixed side mirror 1 and a mirror side molding surface 2b of a moving side mirror 2. While the moving side mirror 2 is being press-contracted to the fixed side mirror 1, when a resin material is filled into the cavity 6, the outer periphery ring 3 is slidably held in a groove of the moving side mirror 2 with predetermined clearances. In the interlock ring 4, a plurality of openings 4a which relieve gas produced by the disc resin material filled into the cavity 6 are formed.

Abstract: An optical disc capable of preventing damages on a printing plate and an injection compression molding die capable of producing such optical disc substrate without raising the accuracy of the die are provided. An optical disc substrate according to one embodiment of the present invention has a ring-formed projected portion on the outer periphery of the printable plane slightly recessed inwardly from the outer edge of the disc. Such optical disc substrate can be produced using a molding die in which a readout-side mirror has a ring-formed groove on the inner surface thereof in the vicinity of a sliding portion between such readout-side mirror and a cavity ring.

Abstract: A clamping apparatus includes a fixed die plate (21) fixed to a frame (26) , four tie rods (23), (24) extending in the horizontal direction and respectiely fixed to the fixed die plate (21) in parallel to each other, a moving die plate (22) supported to the four tie rods (23), (24) so that the moving die plate (22) can slide freely and a clamping mechanism for moving the moving die plate (22) forward and backward along the four tie rods (23), (24) . This clamping apparatus comprises a guide mechanism (25) for downwardly or upwardly supporting the moving die plate (22) and which allows the moving die plate (22) to move in the opposite direction of gravitation.

Abstract: There is provided an infection molding apparatus capable of preventing an occurrence of over-packing which is comprised of: a pair of dies for forming a plurality of cavities therebetween; die closing devices for closing the pair of dies under a prescribed pressure; an injection device for Injecting a molten resin into respective cavities under a prescribed pressure; and a control device for controlling the die closing devices and the Injection device, and further the apparatus comprises a plurality of pressure sensors for detecting respective pressures in respective cavities, wherein the control device controls the injection device and/or the die closing devices to reduce a rate of injection of the molten resin and/or a force of closing of the dies, otherwise to stop the injection and/or the die closing operation when a pressure difference between cavities is found to be greater than a prescribed value on the basis of sensed values from the respective pressure sensors.

Abstract: An optical disc capable of preventing damages on a printing plate and an injection compression molding die capable of producing such optical disc substrate without raising the accuracy of the die are provided. An optical disc substrate according to one embodiment of the present invention has a ring-formed projected portion on the outer periphery of the printable plane slightly recessed inwardly from the outer edge of the disc. Such optical disc substrate can be produced using a molding die in which a readout-side mirror has a ring-formed groove on the inner surface thereof in the vicinity of a sliding portion between such readout-side mirror and a cavity ring.

Abstract: A bonded pipe produced by using the liquid phase diffusion process in which the pipe ends of pipes to be bonded are butted with an insert material lower in melting point than the pipe material against each other, wherein the thickness is increased in such a manner that the outside diameter of the butted portion is expanded and the inside diameter thereof is reduced. A method for bonding pipes in which pipe ends of the pipes are butted through an insert material lower in melting point than the pipe material against each other, and the butted portion is heated to and held at a holding temperature higher than the melting point of the insert material, whereby the insert material is diffused in liquid phase into the pipe material, characterized in that at the time point when the outer pipe face temperature of the above-mentioned butted portion reaches a value which is not less than the A.sub.

Abstract: An optical disc molding device has a pair of molds for injection molding a disc substrate within cavities, and a stamper supported within at least one cavity, for molding a data recording surface in such a manner that the inside diameter side of the stamper supporting surface of the cavity protrudes inwardly in the disc thickness direction from the data recording surface. The flatness of a laminated reference plane has thus been deteriorated by burrs occurring on a disc substrate.

Abstract: A multi-cavity injection molding apparatus capable of simultaneously molding a plurality of optical disk substrates with a simple construction. The injection molding apparatus is constituted of a mold unit having a plurality of cavities and an injection unit for supplying a molten resin to the mold unit. The injection unit is provided with a plurality of nozzles for injecting the molten resin into the cavities, respectively.