Abstract: A disk production apparatus has a movable-side metal mold and a fixed-side metal mold provided as facing the movable-side metal mold, the fixed-side metal mold having a center hole. Inserted into the center hole is a retainer to attach a stamper on the fixed-side metal mold. The center of an inner diameter of the retainer and the center of an outer diameter of the retainer are eccentric with each other. The retainer may be inserted into a center hole of the movable-side metal mold for attaching the stamper on the movable-side metal mold. A disk has a substrate having a center hole; a first zone formed on the substrate, data being recorded on the first zone; and a second zone formed on the substrate but outside the first zone. Labeled on the second zone is a marker indicating an amount of eccentricity applied to the retainer used in production of the disk by injection molding.

Abstract: An optical disc has a support base and at least one information-retrieval layer formed over the support base. The information-retrieval layer is transparent and thinner than the support base. The information-retrieval layer exhibits variation in birefringence within ±20 nmpp (nano meter peak to peak) under double-pass measurements during one rotation of the optical disc.

Abstract: There is disclosed an optical disk apparatus to which a CD, DVD, and extra high density optical disk capable of recording/reproducing an information signal with a density higher than that of the CD or DVD are selectively attachable. The attached optical disk is irradiated with a laser beam for the CD from an optical pickup for the CD/DVD. A focus error signal is detected based on a return light from a signal surface, and the attached optical disk is judged to be the extra high density optical disk when an amplitude of the focus error signal is not more than a predetermined value. When the attached optical disk is judged to be the CD or DVD, a tracking error signal is detected based on the return light from the signal surface. When the amplitude of the tracking error signal is not less than another predetermined value, the attached optical disk is judged to be the CD.

Abstract: An information recording medium 11 is at least composed a substrate 8 having microscopic pattern 3C or 3E, which is constituted by a shape of continuous substance of approximately parallel grooves formed with a convex shaped section and a concave shaped section alternately on a surface of the substrate, a recording layer 9 that is formed on the microscopic pattern 3C or 3E and a light transmitting layer 10 having thickness of 0.05 mm to 0.12 mm that is formed on the recording layer 9. The microscopic pattern 3C or 3E is formed so as to satisfy a relation of P≦&lgr;/NA, wherein P is a pitch of the convex shaped section or the concave shaped section, &lgr; is a wavelength of reproducing light beam and NA is a numerical aperture of an objective lens. Further, the microscopic pattern 3C or 3E is characterized in that a modulated address information is formed on both side walls of the convex shaped section that is viewed form the light transmitting layer side as a wobble having same period and phase.

Abstract: The present invention provides an optical disc provided with a watermark inside, which is visible with naked eyes from a reproduction side of the optical disc, and the producing method and the production apparatus thereof. The optical disc comprises a transparent substrate having an information signal recorded surface, a reflective layer formed on the information signal recorded surface thereof, an adhesive layer formed on the reflective layer, a mask layer on the adhesive layer and a transparent dummy substrate on the mask layer stacked in this order. The adhesive layer is made of an adhesive of which curing speed is changed according to a controlled amount of radiation of ultraviolet rays. The watermark is recorded in the optical disc by irradiating the ultraviolet rays on the adhesive through the mask layer provided with light shielding members to cause the adhesive to be cured by controlling a curing speed of the adhesive corresponding to existence or nonexistence of the light shielding members.

Abstract: The present invention provides an optical disc provided with a watermark inside, which is visible with naked eyes from a reproduction side of the optical disc, and the producing method and the production apparatus thereof. The optical disc comprises a transparent substrate having an information signal recorded surface, a reflective layer formed on the information signal recorded surface thereof, an adhesive layer formed on the reflective layer, a mask layer on the adhesive layer and a transparent dummy substrate on the mask layer stacked in this order. The adhesive layer is made of an adhesive of which curing speed is changed according to a controlled amount of radiation of ultraviolet rays. The watermark is recorded in the optical disc by irradiating the ultraviolet rays on the adhesive through the mask layer provided with light shielding members to cause the adhesive to be cured by controlling a curing speed of the adhesive corresponding to existence or nonexistence of the light shielding members.

Abstract: This invention provides an optical disk effective in both precision and productivity, and to a process for the manufacture thereof. The optical disk allows reading of the information recorded on each information-recording surface of the two or more information-recording surfaces by varying the focal position of a playback laser beam incident on and passing through said light transmitting substrate; and the optical disk is provided with a transparent layer that is laminated onto the light transmitting substrate and is constituted of a thermoplastic resin sheet of uniform thickness and the transparent layer has an information-recording surface other than the surface of said light transmitting substrate formed thereon.

Abstract: An optical recording medium includes a transparent substrate having a surface formed with a track of pits. A reflecting layer extends on the surface of the transparent substrate. The pits include first-type pits and second-type pits. The first-type pits are devoid of projecting rims extending along edges thereof while the second-type pits have projecting rims extending along edges thereof.

Abstract: An information recording medium provides a first signal recording area (A) on which a first data is recorded, and a second signal recording area (B) which is a signal recording area outer from the first area in the radius direction, records a second data at a density higher than that of the first data, and wherein the second data includes the same contents of information as the first data. The recording density of the second data may be 2 to 10 times that of the first data. The sampling rate, the number of quantized bits, and the number of pixels of the second data may be more than the sampling rate, the number of quantized bits, and the number of pixels of the first data, respectively. The first data may be recorded at a fixed transfer rate, and the second data may be recorded at a variable transfer rate. A music signal of an audible band may be recorded for the first data, and a music signal up to an ultrasound band other than an audible band may be recorded for the second data.

Abstract: An optical disk on which information which can be optically read is recorded having a first information recording layer formed in the vicinity of the middle of the direction of the thickness of the disk, a second information recording layer formed in the vicinity of the surface of the optical disk for storing information at a lower density than the first information recording layer and a light incidence surface into which a first and second playback laser beam is irradiated for reading the information in the first and second information recording layers. The light incidence surface is formed on the side of the optical disk opposite the surface, where the second information recording layer is made. The thickness of the disk from the light incidence surface to the second information recording layer should preferably be substantially equal to the thickness of the optical disk.

Abstract: An optical recording medium includes a transparent substrate having a surface formed with a track of pits. A reflecting layer extends on the surface of the transparent substrate. The pits include first-type pits and second-type pits. The first-type pits are devoid of projecting rims extending along edges thereof while the second-type pits have projecting rims extending along edges thereof.

Abstract: The present invention relates to an optical disk having a high density information recording layer for recording information at high density and an information recording layer which stores information at a density lower than the high density information recording layer. The optical disk also has a light incidence surface which is formed on the opposite side from the second information recording layer, where, the thickness of the disk from the light incidence surface to the second information recording layer is made the same as the thickness of the disk.

Abstract: An optical recording medium includes a transparent substrate having a surface formed with a track of pits. A reflecting layer extends on the surface of the transparent substrate. The pits include first-type pits and second-type pits. The first-type pits are devoid of projecting rims extending along edges thereof while the second-type pits have projecting rims extending along edges thereof.

Abstract: A novel optodynamic method and apparatus for the manufacture of an optical record medium of the type having a multiplicity of pits or like optically detectable marks representative of digitized information to be reproduced wherein a stamper is provided which is of quartz glass or like material that transmits ultraviolet radiation and which has a stamping surface shaped as a negative of the optically detectable marks to be created, the stamping surface is pressed against a blank sheet of polycarbonate or like plastic that absorbs ultraviolet radiation the surfaces of blank sheet is irradiated with ultraviolet light through the stamper whereby the surface of the blank sheet gels, or softens, to permit the optically detectable marks to be impressed thereon. The stamping may be dome in a partial vacuum in order to assure closer contact between the stamper and the blank sheet.

Abstract: An electroconductive polymeric material comprises a dispersion of dicyclopentadienyl iron in a vinyl chloride resin having (--CH.sub.2 --CHCl--) structure in the molecular chain or a vinylidene chloride resin having (--CH.sub.2 --CCl.sub.2 --) structure in the molecular chain irradiated with light having ultraviolet rays. This electroconductive polymeric material can easily be molded because it gels under heating, and can also be formed into a film by dissolving it in an organic solvent and evaporating the solvent after casting or spreading. Doping the electroconductive polymeric material with an anionic dopant after the irradiation provides optical response characteristics with further improved electroconductivity.

Abstract: A recording medium of electrostatic capacitance type is recorded with an information signal thereon as variation of geometrical shape of the recording surface part of the recording medium. The signal is reproduced from the recording medium by the variation, in response to the variation of geometrical shape, of the electrostatic capacitance between an electrode of a reproducing stylus tracing relatively the recording surface of the medium and the surface part. At least the surface part of the recording medium having the geometric shape variation is formed by a synthetic resin into which an electroconductive material has been admixed. The synthetic resin forms an outer surface cover of the surface part of the medium thereby to prevent exposure of the electroconductive material to the outside.

Abstract: A high density information record of the electrostatic capacitance type which comprises a record substrate on which signal information is recorded as geometric variations. The substrate is made of a vinyl chloride resin, and carbon black which is purified by electrolysis to remove impurities therefrom.

Abstract: An information signal recording medium comprises a core material made of a non-conductive material, and a surface material made of a conductive material and in close adherence with at least one surface of the core material. Variations in geometrical configuration in accordance with information signals to be recorded on the recording medium are compression molded on the surface material. The materials constituting the surface material and the core material are selected so that a ratio V.sub.C /V.sub.N between a melt viscosity V.sub.C of the surface material and a melt viscosity V.sub.N of the core material at a temperature and a shear rate at the time of the compression molding is less than or approximately equal to 1.6.

Abstract: A constant velocity universal joint of the type having rollers carried by radial trunnions of an inner rotary member and which are received in axial grooves in an outer rotary member, including abutment members which engage abutment surfaces of the grooves and which prevent locking engagement of the rollers with both of the opposed walls of the axial grooves.

Abstract: An improvement is provided in and relating to a capacitance-type record medium wherein an information signal is recorded as a variation in the geometrical shape of its surface area, and is played back by the variation of the capacitance between its surface and an electrode of a reproducing stylus scanning the surface of the record medium relatively which occurs according to a variation in the geometrical shape of its surface area.