Abstract: An optical disk recording and reproducing method. In a system for reproducing unique information which specifies a medium vendor and prohibits use by a third party in a control information area of an optical disk, this method reproduces the control information during a start-up period for recording or reproduction after the optical disk is loaded into a drive unit and displays the unique information on a display unit which is connected to the drive unit.

Abstract: An optical recording medium includes a plane ring-shaped substrate in which a center hole is opened at the center thereof, a recording-retrieving function layer and a cover layer each having an outer diameter approximately equal to that of the substrate and an inner diameter larger than an outer diameter of the center hole, are stacked on the substrate, and as a separate entity from the cover layer, a clamp portion which is for holding and fixing the substrate and which has an outer diameter smaller than inner diameters of the recording-retrieving function layer and the cover layer, is provided around the center hole in a region where the cover layer is not formed.

Abstract: A magneto-optical recording head comprises a magnetic coil formed on a lower surface of a transparent substrate opposed to a magneto-optical disk. A heat sink layer is provided at the outside of the magnetic coil on the lower surface. An objective lens is supported on an upper surface of the transparent substrate. The heat, which is generated by the magnetic coil, is released via the heat sink layer to the space between the magneto-optical disk and the substrate. The release of the heat is facilitated by the air stream which is generated by the rotation of the magneto-optical disk. The heat can be effectively released from the magnetic coil without inhibiting optical characteristics of the objective lens.

Abstract: A magneto-optical recording head comprises a magnetic coil formed on a lower surface of a transparent substrate opposed to a magneto-optical disk. A heat sink layer is provided at the outside of the magnetic coil on the lower surface. An objective lens is supported on an upper surface of the transparent substrate. The heat, which is generated by the magnetic coil, is released via the heat sink layer to the space between the magneto-optical disk and the substrate. The release of the heat is facilitated by the air stream which is generated by the rotation of the magneto-optical disk. The heat can be effectively released from the magnetic coil without inhibiting optical characteristics of the objective lens.

Abstract: A magneto-optical recording medium comprises a recording layer 5, an intermediate layer 4, and a reproducing layer 3. The reproducing layer 3 is formed of a rare earth transition metal alloy in which rare earth metal is dominant, and each of the intermediate layer 4 and the recording layer 5 is formed of a rare earth transition metal alloy in which transition metal is dominant. The intermediate layer 4 exhibits in-plane magnetization at a temperature of not less than 140° C. Therefore, the intermediate layer 4 cuts off the exchange coupling force between the recording layer 5 and the reproducing layer 3 during the reproduction. A magnetic domain 3A, which is transferred to the reproducing layer 3, is expanded to a size of a minimum magnetic domain diameter by the magnetostatic repulsive force exerted between the magnetic domain in the intermediate layer 4 and the magnetic domain in the reproducing layer.

Abstract: An information recording medium has such error detecting codes that the distance between the codes of adjacent tracks of the medium is always 1. The bits E1-Em of the detecting codes, which are included by pre-format information, are generated as data trains of parity check bits constructed by dividing the bits S1-Sm of the sector numbers and the bits T1-T2 of the track numbers. If the generated detecting codes are compared between adjacent, tracks, the distance between the codes is always 1. Consequently, when the detecting codes of a desired track are read out, substantially no cross talk occurs from the detecting codes of the adjacent tracks. Therefore, even if the recording medium has a narrow track pitch, it is possible to reliably and accurately detect the errors of address data of the medium.

Abstract: There is provided a disk cartridge adaptable to an enlarged head by exposing an information recording disk extensively out of a cartridge case. In the disk cartridge, a cartridge case is divided on its plane into at least a first case portion and a second case portion, and the second case portion is arranged to be slidable relative to the first case portion. When the disk cartridge is not in use, the information recording disk is enabled to be covered by the first case portion and the second case portion by keeping the first case portion and the second case portion in a parallel state, and a disk freeing portion is so formed that, when the disk cartridge is in use, exposes parts of both inside face and outside face of the information recording disk are exposed from the cartridge case by moving the second case portion relative to the first case portion and overlapping the first case portion and the second case portion.

Abstract: A compact recording and reproducing apparatus includes a floating-type head movable in a fan shape in parallel with the surface of a disk recording medium in order to make faster access to the tracks and to record information at a higher density. A slider and a head are secured to the tip of a swing arm capable of fan-shaped swing movement, and a solid immersion lens is used for the head, so that the light beam can be passed along the arm from the fulcrum at the rotating pivot of the swing arm member.

Abstract: A magneto-optical recording head comprises a magnetic coil formed on a lower surface of a transparent substrate opposed to a magneto-optical disk. A heat sink layer is provided at the outside of the magnetic coil on the lower surface. An objective lens is supported on an upper surface of the transparent substrate. The heat, which is generated by the magnetic coil, is released via the heat sink layer to the space between the magneto-optical disk and the substrate. The release of the heat is facilitated by the air stream which is generated by the rotation of the magneto-optical disk. The heat can be effectively released from the magnetic coil without inhibiting optical characteristics of the objective lens.

Abstract: There is provided a disk cartridge adaptable to an enlarged head by exposing an information recording disk extensively out of a cartridge case. In the disk cartridge, a cartridge case is divided on its plane into at least a first case portion and a second case portion, and the second case portion is arranged to be slidable relative to the first case portion. When the disk cartridge is not in use, the information recording disk is enabled to be covered by the first case portion and the second case portion by keeping the first case portion and the second case portion in a parallel state, and a disk freeing portion is so formed that, when the disk cartridge is in use, exposes parts of both inside face and outside face of the information recording disk are exposed from the cartridge case by moving the second case portion relative to the first case portion and overlapping the first case portion and the second case portion.

Abstract: A magneto-optical recording medium comprises, on a substrate, a reflective layer, a first dielectric layer, a recording layer, and a second dielectric layer successively in this order, for being irradiated with a recording or reproducing light beam coming from a side of the second dielectric layer. A diamond-like carbon layer as a self-lubricating layer is formed on the second dielectric layer. An optical head comprises a floating type slider installed with a solid immersion lens. A protective film having a self-lubricating property may be also formed on a bottom surface of the slider opposing to the optical recording medium. Even when the floating position of the optical head is varied, and the optical head contacts with the surface of the optical recording medium, then the sliding scratch scarcely occurs, because the optical head smoothly glides on the recording medium surface. A lubricating layer may be further formed on the self-lubricating layer.

Abstract: A cavity surface-forming plate of a mold for injection-molding a plastic substrate is coarsely polished, and then a surface for defining a cavity is applied with electroless Ni—P plating. The surface of the plating is polished with abrasive grains to obtain surface roughness of Ra≦2.0 nm and Rmax≦22 nm. The plastic substrate molded with the mold has smoothness equivalent to the polished plating surface. A concave-convex pattern for forming pits may be formed on the cavity surface. A magnetic disk or an optical disk provided with the substrate makes it possible to realize the near contact system for a magnetic or magneto-optical head. Thus, it is possible to realize high density recording.

Abstract: A recording disk comprises a substrate including a plastic material, and an overlay arranged over the substrate and including a recording substance for recording therein an information, and a radially-outer periphery of the overlay is received within a radially-outer periphery of the substrate as seen in an axial direction of the recording disk.

Abstract: On a surface of a transparent substrate 1 having a preformat pattern 2 formed thereon are laminated a first recording layer 4 in which a recording state exists in one different magnetic field region of an applied external magnetic field and a second recording layer 6 in which two recording states exist in magnetic field regions different from that for the first recording layer. As required, dielectric layers 3, 5 and 7, a reflecting layer 8 and a protection layer 9 can be laminated. The 4-valued recording of information becomes possible by assigning information signals “1”, “0”, “3”, and “2” to H0, H1, H2 and H3, respectively.

Abstract: A magneto-optical recording medium comprises, on a substrate, a reflective layer, a first dielectric layer, a recording layer, and a second dielectric layer successively in this order, for being irradiated with a recording or reproducing light beam coming from a side of the second dielectric layer. A diamond-like carbon layer as a self-lubricating layer is formed on the second dielectric layer. An optical head comprises a floating type slider installed with a solid immersion lens. A protective film having a self-lubricating property may be also formed on a bottom surface of the slider opposing to the optical recording medium. Even when the floating position of the optical head is varied, and the optical head contacts with the surface of the optical recording medium, then the sliding scratch scarcely occurs, because the optical head smoothly glides on the recording medium surface. A lubricating layer may be further formed on the self-lubricating layer.

Abstract: A cavity surface-forming plate of a mold for injection-molding a plastic substrate is coarsely polished, and then a surface for defining a cavity is applied with electroless Ni-P plating. The surface of the plating is polished with abrasive grains to obtain surface roughness of Ra.ltoreq.2.0 nm and Rmax.ltoreq.22 nm. The plastic substrate molded with the mold has smoothness equivalent to the polished plating surface. A concave-convex pattern for forming pits may be formed on the cavity surface. A magnetic disk or an optical disk provided with the substrate makes it possible to realize the near contact system for a magnetic or magneto-optical head. Thus, it is possible to realize high density recording.

Abstract: An optomagnetic recording and reproducing system has been developed which demonstrates superior performance when used with multilayer recording substrates. The system features an optical head and magnetic head disposed opposite to each other on different sides of the recording substrate. The novel magnetic head can either incorporate a number of independently driven subheads, or alternately it can be constructed by placing multiple independently driven windings on a single head. Biasing of the magnetic head can either be performed externally using an external magnet or by providing a bias with one of the windings or sub-heads. The resulting optomagnetic recording and reproducing system is suitable for multi-valued recording of an optomagnetic recording medium.

Abstract: On a surface of a transparent substrate 1 having a preformat pattern 2 formed thereon are laminated a first recording layer 4 in which a recording state exists in one different magnetic field region of an applied external magnetic field and a second recording layer 6 in which two recording states exist in magnetic field regions different from that for the first recording layer. As required, dielectric layers 3, 5 and 7, a reflecting layer 8 and a protection layer 9 can be laminated. The 4-valued recording of information becomes possible by assigning information signals "1", "0", "3" and "2" to H.sub.0, H.sub.1, H.sub.2 and H.sub.3, respectively.

Abstract: A compact recording and reproducing apparatus includes a floating-type head movable in a fan shape in parallel with the surface of a disk recording medium in order to make faster access to the tracks and to record information at a higher density. A slider and a head are secured to the tip of a swing arm capable of fan-shaped swing movement, and a solid immersion lens is used for the head, so that the light beam can be passed along the arm from the fulcrum at the rotating pivot of the swing arm member.

Abstract: The present invention provides a magnetic recording medium with distinguished SNR and mechanical characteristics, which comprises an underlayer, a ferromagnetic thin film metallic layer and a protective film layer successively and continuously laminated on a non-magnetic resin substrate, where (A) at least one layer selected from the group consisting of an Si layer, an Si.sub.w N.sub.x C.sub.y O.sub.z layer and an Al.sub.w N.sub.x C.sub.y O.sub.z layer and (B) at least one layer selected from the group consisting of silicides, nitrides, oxides or their mixtures of Ti, Ta, Mo, V, Zr and their alloys are laminated on the non-magnetic resin substrate in the order of (A) and (B) or (i) a layer composed of at least one material selected from the group consisting of Ti, Ta, Mo, V, Zr, Nb and their alloys, (ii) at least one layer selected from the group consisting of an Si layer, an Si.sub.w N.sub.x C.sub.y O.sub.z layer and an Al.sub.w N.sub.x C.sub.y O.sub.z layer (where w+x+y+z=100 at. %, w.gtoreq.30 at. %, 0 .