Abstract: A recording medium for information signals including a substrate, a signal recording layer provided on one major surface of the substrate and a clamp member having a positioning unit at its center portion and formed of a material that can be magnetically attracted by a magnet. The clamp member is unified to the center portion of the substrate so that the surface of the clamp member will be flush with the substrate surface.

Abstract: An optical recording medium capable of suppressing warps arising during a long time use and a method of producing the same, which has the configuration of comprising a substrate 13, an optical recording layer 14 formed on the substrate 13 and a light transmitting protective film 17 formed on the optical recording layer 14, wherein the protective film 17 includes a polymer film 16 having a thermal shrinkage coefficient of 0.02% or less and an adhesive layer 15 for adhering the polymer film 16 to the optical recording layer 14. As the polymer film 16, those produced by a melt cast method, subjected to annealing processing in advance or having a residual solvent of 0.3% by weight or less in the film may be preferably used.

Abstract: Heat sink has fins on the top surface thereof and pin portions on the bottom surface thereof. Rivets having longitudinal through-hole are inserted into holes in a retention module. When the heat sink and the retention module are simultaneously pressed downward, the rivets are inserted into the corresponding holes formed in a base board. The pin portions are inserted into the through-holes of the rivets so that the retention module is locked onto the base board and the heat sink is fixed and the bottom surface of the heat sink is contacted with an integrated circuit element, at the same time.

Abstract: The present invention relates to a multi-layered disc-shaped information recording medium having a plurality of signal recording layers each carrying information signals. In preparing the recording medium, a first substrate obtained on punching a sheet obtained in turn by having a signal recording pattern transcribed on it from a first stamper and by forming a semi-transparent film on a signal surface is bonded to a second substrate obtained on injection molding a synthetic resin material. The second substrate is prepared by having transcribed to it a signal recording pattern formed on a second stamper provided on an injection molding device. A reflective film is formed on a signal surface having the transcribed second substrate. The first and second substrates are bonded together on their signal recording layers by a transparent adherent layer.

Abstract: An optical disc includes a substrate, and a recording layer and transparent layer formed in this order on the substrate. A light is incident from the transparent layer to write and/or read an information signal. The substrate comprises a first resin layer forming a surface of the substrate on which the recording layer is formed, and a second resin layer having a higher flexural modulus is formed on the first resin layer.

Abstract: An optical disc and its manufacturing method in which humps may be prohibited from being formed on an outer rim area of the disc to assure optimum surface properties of a light transmitting layer of the disc to contribute to further increase in recording capacity. On a substrate 2 of an optical disc 1 are sequentially formed a recording portion 6 and a light transmitting layer 5. The light falls on the light transmitting layer 5 to record and/or reproduce information signals for a signal recording area 6a of the substrate 2. The radial distance D from the outermost rim of the substrate 2 to the signal recording area 6a is selected to be larger than the radial width L of a hump 5a formed on the outer rim of the light transmitting layer 5. The hump 5a has a height h from the surface of the light transmitting layer 5 not larger than 70 &mgr;m.

Abstract: An optical disc comprising a substrate and a recording layer and a light-transmitting layer, laid on a substrate one upon the other in the order mentioned. A light beam is applied to the recording layer through the light-transmitting layer, to record and/or reproduce data on the disc. The light-transmitting layer is composed of at least two material layers laid one on the other and having different refractive indices. The disc is designed to set the spherical aberration caused by an objective lens that focuses the light beam used to record and/or reproduce data, at a value close to a minimum.

Abstract: An optical disk has a groove formed in the direction of a recording track and a first information signal is recorded by forming a row of marks or dots on the groove or land. A second information signal can also be recorded on the groove or land without adversely affecting the playback characteristic of the first information signal. A groove is formed in the direction of the recording track and a row of marks or dots corresponding to the first information signal is formed on the groove or land, so that the first information signal can be recorded. Further, by forming a wave having a spatial frequency higher than a cut-off frequency of a playback optical system corresponding to a second information signal on a part or all of the groove, the second information signal is recorded. The second information signal can represent visible information.

Abstract: A method of production of a multilayer optical recording medium capable of avoiding difficulties in separating a stamper and forming a semi-transparent film on a thin flexible film and a production method thereof, comprising steps of forming a first optical recording layer on a substrate formed with a pattern of irregularities for a first optical recording layer on a surface thereof, forming a transfer substrate comprised of an acrylic resin formed with a pattern of irregularities on a surface thereof, forming a second optical recording layer on the pattern of irregularities of the transfer substrate, adhering a flexible film at the upper portion of the second optical recording layer by an adhesive layer, separating the second optical recording layer and the transfer substrate at their boundary to transfer the second optical recording layer to the flexible film, and bonding together the first optical recording layer and the second optical recording layer with them facing each other.

Abstract: An optical disc consisting of a substrate and at least a recording layer formed on the substrate is recycled by peeling off the recording layer from the substrate; and bonding another substrate having a recording layer formed thereon to the substrate from which the recording layer has been removed, whereby a renewed optical disc is provided.

Abstract: A recording medium for information signals including a substrate, a signal recording layer provided on one major surface of the substrate and a clamp member having a positioning unit at its center portion and formed of a material that can be magnetically attracted by a magnet. The clamp member is unified to the center portion of the substrate so that the surface of the clamp member will be flush with the substrate surface.

Abstract: An optical recording medium, in which a signal is recorded in both of a groove and a land, has a disconnected portion of a predetermined interval in the groove and the land so that a control signal is detected by this disconnected portion.

Abstract: A beam irradiation apparatus includes a beam generation source (41) for generating at least either of an optical beam, an electron beam and an ion beam, and a focusing lens (48) for focusing a beam emitted from the beam generation source (41). The beam irradiation apparatus includes at least first and second focus control mechanisms (71) and (72) each controlling a focus position of the beam with respect to the same lens system forming the focusing lens, so as to focus the beam onto an irradiation object (40) by using the focusing lens (48), whereby it possible to obtain a minute beam spot and to conduct a reliable, and stable focus control.

Abstract: An optical disc having a light transmitting layer of a reduced uniform thickness. The optical disc has a transparent film bonded via a pressure-sensitive adhesive sheet or a dry photopolymer sheet on a substrate to serve as a light transmitting layer. The signal recording surface is formed on the substrate and/or the transparent film. The light transmitting layer may be constituted solely by a pressure-sensitive adhesive sheet or a dry photopolymer sheet. In the present optical disc, recording and/or reproduction is performed from the light transmitting layer with respect to the signal recording surface. The pressure-sensitive adhesive sheet or the dry photopolymer sheet is itself in a sheet form and is previously formed into a layer (sheet) of a pre-set thickness, in a manner different from the case in which a UV light curable resin is coated on a substrate.

Abstract: An optical recording medium capable of improving uniformity of thickness of a protective film and suppressing warping. The medium is configured to comprise a substrate, an optical recording film formed on the substrate, and a light transmitting protective film formed above the optical recording layer, wherein the protective film comprises a polymer sheet produced by melt casting and an adhesive layer for bonding the polymer sheet to the-optical recording layer. As the polymer sheet, a polycarbonate sheet, a cyclic polyolefin sheet, etc. can be used. As the adhesive layer, an ultraviolet curing resin, a heat curing resin, an epoxy resin-based adhesive agent or a pressure-sensitive tackiness agent may be used alone or mixed or stacked.

Abstract: An optical disc prepared so that, in bonding a disc substrate to a light transmitting sheet, an air bubble incidentally trapped on a bonding surface between the disc substrate and the light transmitting sheet may be reduced in size. An apparatus used for the preparation of the optical disc includes a sheet holding mechanism (32) for holding a light transmitting sheet (19) to be bonded to a signal recording surface (14) of a disc substrate (11), a disc holding mechanism (33) for holding the disc substrate (11) on the light transmitting sheet (19) held on the sheet holding mechanism (32) so that its signal recording surface (14) will face the light transmitting sheet (19), and a thrusting mechanism (34) for thrusting the disc substrate (11) held on the sheet holding mechanism (32) onto the light transmitting sheet (19). The thrusting mechanism (34) progressively thrusts the disc substrate (11) from its center side to its outer peripheral side to drive the air bubble towards the outer peripheral side.

Abstract: A method of production of a multilayer optical recording medium capable of avoiding difficulties in separating a stamper and forming a semi-transparent film on a thin flexible film and a production method thereof, comprising steps of forming a first optical recording layer on a substrate formed with a pattern of irregularities for a first optical recording layer on a surface thereof, forming a transfer substrate comprised of an acrylic resin formed with a pattern of irregularities on a surface thereof, forming a second optical recording layer on the pattern of irregularities of the transfer substrate, adhering a flexible film at the upper portion of the second optical recording layer by an adhesive layer, separating the second optical recording layer and the transfer substrate at their boundary to transfer the second optical recording layer to the flexible film, and bonding together the first optical recording layer and the second optical recording layer with them facing each other.

Abstract: The present invention provides an optical recording medium including a recording layer and a light-transmitting layer successively formed on one side of a substrate, so that a light is applied from the side of this light-transmitting layer for performing an information recording and/or reproduction. On the opposite side of the substrate not having the light-transmitting layer, a water-proof film consisting of at least one layer is formed. This suppresses the skew, enabling to improve the information recording and/or reproduction characteristics for a higher recording density. Furthermore, if the light-transmitting layer has a thickness t=3 to 177 micrometers in an information signal section of the recording medium, and a thickness fluctuation &Dgr;t ≦±5.26 (&lgr;/NA4) micrometers (wherein NA is a numerical aperture and &lgr; is a wavelength of the recording/reproduction optical system), it is possible to realize a high NA and a high capacity.

Abstract: An optical disc and its manufacturing method in which humps may be prohibited from being formed on an outer rim area of the disc to assure optimum surface properties of a light transmitting layer of the disc to contribute to further increase in recording capacity. On a substrate 2 of an optical disc 1 are sequentially formed a recording portion 6 and a light transmitting layer 5. The light falls on the light transmitting layer 5 to record and/or reproduce information signals for a signal recording area 6a of the substrate 2. The radial distance D from the outermost rim of the substrate 2 to the signal recording area 6a is selected to be larger than the radial width L of a hump 5a formed on the outer rim of the light transmitting layer 5. The hump 5a has a height h from the surface of the light transmitting layer 5 not larger than 70 &mgr;m.

Abstract: An optical recording medium includes a first recording member having a first light-transmissive substrate and a first semi-light-transmissive information area disposed on a surface of the first light-transmissive substrate, and a second recording member having a second substrate and a second reflective information area disposed on a surface of the second substrate. The first recording member and the second recording member are joined to each other with the transparent layer interposed therebetween with the first and second information areas facing each other.