Abstract: Methods of forming and operating phase change memory devices include adjusting an activation energy barrier between a metastable phase and a stable phase of a phase change material in a memory cell. In some embodiments, the activation energy barrier is adjusted by applying stress to the phase change material in the memory cell. Memory devices include a phase change memory cell and a material, structure, or device for applying stress to the phase change material in the memory cell. In some embodiments, a piezoelectric device may be used to apply stress to the phase change material. In additional embodiments, a material having a thermal expansion coefficient greater than that of the phase change material may be positioned to apply stress to the phase change material.

Abstract: An electric bicycle is provided that can increase the diameter of the joining section between a crankshaft and a crank arm, suppress an increase in manufacturing cost, and minimize a size increase of a hanger with a torque sensor disposed in the hanger. A crankshaft 17 is divided into a crankshaft body 17A on the periphery of which a torque sensor 23 is disposed, and an auxiliary crankshaft 17B connected to one side of the crankshaft body 17A. A diameter D1 of the joining section between the auxiliary crankshaft 17B and a crank arm 18B and a diameter D3 of the joining section between the crankshaft body 17A and a crank arm 18A are larger than a diameter D2 of the connecting section between the crankshaft body 17A and the auxiliary crankshaft 17B.

Abstract: A transported medium transporting apparatus includes a transported medium transporting device and at least one pressing driven roller. The transported medium transporting device transports a transported medium in a predetermined transportation direction. The pressing driven roller is driven so that the pressing driven roller contacts one surface of the transported medium, which is transported by the transported medium transporting device. The pressing driven roller includes a rotary body and a shaft portion, both of which are made of elastic synthetic resin and formed integrally with each other. A plurality of protrusions are formed on the rotary body at regular intervals in a circumferential direction of the rotary body. The shaft portion rotatably supports the rotary body so that the rotary body can be driven. The pressing driven roller has a shape such that the rotary body contacts the transported medium with a predetermined pressing force owing to an elastic force of the shaft portion.

Abstract: A clip without UMID is transmitted to a disc drive from an editing device. The disc drive generates the UMID and NRT with respect to the transmitted clip, and stores the UMID in association with the NRT. The editing device edits the NRT, and transmits the NRT that is edition results to the disc drive. The disc drive overwrites the NRT that has been transmitted from the editing device on the generated NRT, and stores the NRT in association with the clip with the UMID. The present invention can be applied to a disc recording and reproducing device.

Abstract: A fluid bearing device 40 comprises a sleeve 1, a shaft 2, a thrust plate 4, a radial bearing component 21, and a thrust bearing component 22. A bearing hole 1a is formed in the sleeve 1. The shaft 2 has a shaft main component 5 that is inserted in the bearing hole 1a, and a flange 3 provided on the axial lower side of the shaft main component 5. The thrust plate 4 is fixed to the sleeve 1 and covers the shaft 2 from the axial lower side. A screw hole 5a that is coaxial with the shaft main component 5 is formed in the shaft main component 5 from the end face on the axial upper side toward the axial lower side. An annular concave component 3c that is coaxial with the shaft 2 is formed in the end face on the axial lower side of the shaft 2.

Abstract: An optical disk apparatus records information by irradiating a laser beam from a pickup onto an optical disk. A scanning section scans the laser beam relative to the optical disk. A recording control section controls the scanning section to effect recording of information. A drawing control section is provided for controlling the pickup and the scanning section to effect drawing of a visible image on the optical disk according to image information, such that the laser beam is changed between a first intensity incapable of acting on the optical disk and a second intensity capable of acting on the optical disk. A servo section periodically detects the laser beam reflected back from the optical disk when the laser beam has the first intensity, and servo-controls the irradiating of the laser beam during the drawing of the visible image based on the detection of the laser beam.

Abstract: An optical disk of the type rotated by a spindle positioned in a centrally-located hole, and including a disk body including an annular data area, and a centrally-located, integrally-formed annular web positioned radially inward from the annular data area and covering a hole formed in the disk body. The annular web is formed sufficiently thin to be deflected upwardly out of the plane of the disk body by the spindle during placement on the spindle and during rotation. The web may be broken away from the disk, or made sufficiently thin and resilient that it will deform upwardly when placed on the spindle and resume its former position when removed.

Abstract: In case of manufacturing a disk having a two-layer structure, a glass substrate 13 is bonded to a cover layer 11 through an adhesive layer 12, and a mount hole 14a is formed in a center thereof to form a bonded substrate 14 having a three-layer structure (a). In a state where a stamper 15 formed a predetermined pit pattern is set to a center boss 16, the bonded substrate 14 is pressed downward in a vertical direction while the mount hole 14a of the bonded substrate 14 is aligned with the center boss 16(b). Whereby an information recording surface 11a is transferred onto the cover layer 11(c). Subsequently, after the bonded substrate 14 has been bonded to another layer substrate of the disk, the adhesive layer 12 is removed to separate the glass substrate 13. Finally, there is manufactured the disk having the two-layer structure.

Abstract: A glass substrate for a magnetic disk of the present invention is one in which a laser beam is irradiated on a main surface thereby forming a large number of protrusions thereon to form texture thereon, each of said protrusions being formed by a protruded portion having a convex shape, said glass having a composition in which 0.2 to 3 wt % of an oxide of a transition metal is contained and an absorption coefficient with respect to a wavelength of a light at 266 nm being within a range of 0.03 to 2 .mu.m.sup.-1, and by setting the absorption coefficient of the glass with respect to a wavelength of a light at 266 nm within a range of 0.03 to 2 .mu.m.sup.-1 and irradiating a laser beam having a wavelength in a range of ultraviolet rays selectively on the main surface of a glass substrate at predetermined intervals, texture comprising a large number of protrusions formed by protruded portions each having a small diameter and a convex shape is formed.

Abstract: A glass substrate for a magnetic disk of the present invention is one in which a laser beam is irradiated on a magnetic recording surface side thereby forming a large number of protrusions thereon to form texture thereon, each of the protrusions having a convex shape, an optical absorption coefficient of a glass with respect to a wavelength of a laser beam at 266 nm being within a range of 20 to 2000 mm.sup.-1, the glass having a composition by weight of:silicon oxide (SiO.sub.2): 58 to 66%,aluminum oxide (Al.sub.2 O.sub.3): 13 to 19%,lithium oxide (Li.sub.2 O): 3 to 4.5%,sodium oxide (Na.sub.2 O): 6 to 13%,potassium oxide (K.sub.2 O); 0 to 5%,R.sub.2 O: 9 to 18% (provided R.sub.2 O=Li.sub.2 O+NaO+K.sub.2 O),magnesium oxide (MgO): 0 to 3.5%,calcium oxide (CaO): 1 to 7%;strontium oxide (SrO): 0 to 2%;barium oxide (BaO): 0 to 2%,RO: 2 to 10% (provided RO=MgO+CaO+SrO+BaO), andiron oxide (Fe.sub.2 O.sub.3): 0.05 to 2%,titanium oxide (TiO.sub.2): 0 to 2%,cerium oxide(CeO.sub.

Abstract: A back-up power device for a microcomputer which can supply back-up power to a microcomputer in the event of a power failure. The power device is installed in a standard disc or hard disc drive slot of the computer. Switches and alarm lights of the power device are visible and accessible to the user without opening the case of the computer. The power device outputs a signal related to its operating status to the computer. The power device also measures the output voltage from the power source of the computer to compensate the voltage drop in the cables between the power device and the computer's power supply, and can be programmed to restart the computer after a power break if required.

Abstract: There is provided an information recording apparatus having a vacuum system. The apparatus includes a vacuum chamber connected with a first evacuator device. An electronic beam producing device is partially enclosed in the vacuum chamber for emitting an electronic beam for recording information on a recording medium. A moving stage is provided in the vacuum chamber for linearly moving the recording medium in a vacuum atmosphere within the vacuum chamber. A spindle is disposed in the vacuum chamber for rotating the recording medium. The spindle is supported on an air bearing and is rotatably driven by a spindle motor. A magnetic fluid seal producing device is provided around the spindle close to the vacuum chamber side. A pressure differential chamber is provided around the spindle close to the air bearing side. The pressure differential chamber is connected with a second evacuator device.

Abstract: A glass substrate for a magnetic disk having an inner peripheral edge and an outer peripheral edge, wherein the surface of at least the inner peripheral edge is treated by etching to have a surface roughness such that, as measured by a three dimensional scanning electron microscope at randomly selected at least four places with a reference length of 240 .mu.m and a cut-off wavelength of arithmetic mean roughness (Ra) of 80 .mu.m, the mean value of arithmetic mean roughness (Ra) is from 1.0 to 6.0 .mu.m, and the mean value of the number of peaks is within a range of from 8 to 30.

Abstract: An optical recording medium is disclosed, which comprises a substrate having thereon a recording layer which is capable of forming regions having an increased reflectivity by spinodal decomposition of the recording layer upon application thereto of energy of a threshold value or higher. Writing of information is achieved by irradiating the recording layer with no phase separation caused by spinodal decomposition with an energy beam having an intensity causing spinodal decomposition-induced phase separation in accordance with the information to be written. Reading of the information, on the other hand, is achieved by irradiating the recording layer with phase separation caused by spinodal decomposition with an energy beam having an intensity causing no spinodal decomposition-induced phase separation. The medium and the recording system using the same exhibit high sensitivity, high reflectivity, and high contract and conform to the CD or LD standard.

Abstract: An optical memory material includes a two-photon storage component which can be written from a first to a second state in response to WRITE light, mixed with a signal component which fluoresces by one-photon absorption only at the written locations in response to READ light. The storage material may be a fulgide. The memory material may also include a frequency upconversion material to aid writing. Writing is performed by a spatial light modulator (SLM) with a dynamic focussing system, for concentrating sufficient power at WRITE locations for nonlinear two-photon absorption. Crosstalk is avoided during simultaneous writing in some embodiments, by spacing the individual WRITE beams apart by an integer number of inter-beam spacings, so that non-adjacent datels are written simultaneously in a "paragraph," and the non-written areas are written at a different time with different paragraphs.

Abstract: An optical recording medium has a mask layer 4, an intermediate dielectric layer 5, a recording layer 6, and a reflective layer 8 on a transparent substrate 2. The recording layer 6 contains a recording material which changes its crystallographic structure upon exposure to recording light for recording information. The mask layer 4 contains a mask material which increases its light transmittance when melted and has a complex refractive index (n.sub.0 -ik.sub.0), of which the real part n.sub.0 drops by 1.0 or less and the imaginary part k.sub.0 drops by 0.25-1.0 when the mask material converts from a crystalline state to an amorphous or microcrystalline state. Signals can be reproduced from the medium with high C/N without resorting to reading light of shorter wavelength or an optical pickup objective lens having a larger numerical aperture and even when the linear velocity of the medium relative to recording and reproducing light is low.

Abstract: An optical recording medium comprising a substrate and a thin organic film containing at least one kind of dye selected from polymethine family dyes, perylium family dyes, and cyanine family dyes, and a recording process comprising scanning the optical recording medium with a high intensity light beam such as a laser beam to form optically detectable pits on the recording medium.

Abstract: An optical recording medium comprising a substrate and a thin organic film containing at least one kind of dye selected from polymethine family dyes, perylium family dyes, and cyanine family dyes, and a recording process comprising scanning the optical recording medium with a high intensity light beam such as a laser beam to form optically detectable pits on the recording medium.

Abstract: A web feeding and handling system for feeding a two-ply web to a printer and winding one of the webs about a take-up spool and directing the remaining web into a cutter. The printer and web feed system are arranged in a housing having an access opening sealed by a door. The printer and a feed roller holder assembly are mounted upon a plate movable between a position enhancing access to the printer and supply roll holder to facilitate supply roll replacement and feeding the web into the printer, and a position placing the printer web output end closer boa cutter and a take-up assembly mounted upon the door and including a rotatable drive disk and a spindle support which support a removable spindle to wind up one web. A motor drive mounted within the housing engages the drive disk when the door is closed and is disengaged from the disk when the door is open. The supply roll holder receives and automatically aligns the web to prevent skewing.

Abstract: A double-side optical disc formed by a pair of optical disc halves bonded together, and a process for producing the double-side optical disc. An adhesive is applied to the disc halves, which are then bonded together at an angle relative to each other in which the direction of the adhesive flow on one disc half will intersect the direction of the adhesive flow on the other disc half. In this manner, satisfactory flatness of the optical disc may be achieved without being affected by surface irregularities of the adhesive layer.

Abstract: An optical recording medium comprising a substrate and a thin organic film containing at least one kind of dye selected from polymethine family dyes, perylium family dyes, and cyanine family dyes, and a recording process comprising scanning the optical recording medium with a high intensity light beam such as a laser beam to form optically detectable pits on the recording medium.

Abstract: An information recording disc including a plurality of disc substrates (2), at least one of which has a recording medium containing layer (1), two pieces of hubs mounted over the center hole of said disc substrates on both sides thereof, each hub having a portion to be inserted into said center hole and a flange portion to cover a portion of said disc substrate in the vicinity of said center hole, and an adhesive layer (13, 14) formed between said hubs and said disc substrates and between said two hubs. An adhesive layer (7) laminates the substrates (2a, 2b) to one another.

Abstract: An optical recording medium comprising a substrate and a thin organic film containing at least one kind of dye selected from polymethine family dyes, perylium family dyes, and cyanine family dyes, and a recording process comprising scanning the optical recording medium with a high intensity light beam such as a laser beam to form optically detectable pits on the recording medium.

Abstract: An encoder system for providing a large number of actual positional control pulses per revolution utilizes an optical digital disc. The disc is driven by the work piece transport system. A playback unit similar in construction to audio disc players can be used. The positional control information is recorded on the disc as the disc is being driven by the transport system with which the disc is to be associated. Mechanical anomalies of the drive system are compensated for in the recording process. The accuracy of the positional information is improved. The system is especially useful for high resolution ink jet printing system.

Abstract: The present invention provides a thermoplastic composition excellent in heat resistance and water resistance which includes a thermoplastic saturated norbornene polymer which has a number-average molecular weight (Mn) of 50,000-500,000 and a weight-average molecular weight (Mw) of 100,000-2,000,000 which are measured by high performance liquid chromatography, and a molecular weight distribution (Mw/Mn) of 2.2 or more, and a volatile content of at most 0.3% by weight higher. The composition is suitable for optical materials, electroconductive composite materials and optical recording media.

Abstract: Recording and erasing optical information can be done by using an alloy film capable of forming two stable crystalline states differing in crystal texture and optical characteristics by being irradiated with optical energies under different conditions. A thin memory film preferably including 60 to 90 atom % of Indium (IN) and 10 to 40 atom % of Bismuth (Bi) is formed on a substrate.

Abstract: In a large capacity memory disk of the type in which data are read out by an optical system, the invention provides a large capacity memory disk characterized in that a methyl methacrylate copolymer consisting of 99 to 20 percent by weight methyl methacrylate and 1 to 80 percent by weight of a monomer copolymerizable with methyl methacrylate is used as the disk substrate.

Abstract: An optical recording medium comprising a substrate and a thin organic film containing at least one kind of dye selected from polymethine family dyes, perylium family dyes, and cyanine family dyes, and a recording process comprising scanning the optical recording medium with a high intensity light beam such as a laser beam to form optically detectable pits on the recording medium.

Abstract: An optical recording medium comprising a substrate and a thin organic film containing at least one kind of dye selected from polymethine family dyes, perylium family dyes, and cyanine family dyes, and a recording process comprising scanning the optical recording medium with a high intensity light beam such as a laser beam to form optically detectable pits on the recording medium.

Abstract: A method for producing an optical disc including the step of transferring a pattern of alternate projections and recesses from a stamper to a glass base plate by photopolymerization of a resin curable with ultraviolet rays, wherein the glass base plate is previously processed by surface processing by a suitable coupling agent. Before or after the surface processing with the coupling agent, the glass base plate is heated under a reduced pressure for improving bonding properties between the glass base plate and the resin curable with ultraviolet rays.

Abstract: Recording and erasing optical information can be done by using an alloy film capable of forming two stable crystalline states differing in crystal texture and optical characteristics by being irradiated with optical energies under different conditions. The thin memory film preferably includes not more than 60 atom % of Gallium (Ga) and not less than 40 atom % of Antimony (Sb).

Abstract: Recording and erasing optical information can be done by using an alloy film capable of forming two stable crystalline states differing in crystal texture and optical characteristics by being irradiated with optical energies under different conditions. The memory film includes 35-45 atom % of indium (In) and 55-65 atom % of antimony (Sb). The memory film may include an additional element M selected from the group consisting of Al, Si, P, S, Zn, Ga, Ge, As, Se, Ag, Cd, Sn, Te, Tl, Pb, Bi, and a combination of these elements, the composition of the memory film being expressed by the formula (In.sub.x Sb.sub.1-x).sub.1-y M.sub.y.

Abstract: An optical information signal record medium which comprises a substance of a desired form having information signals encoded on at least one side thereof, a reflection thin layer of a Cu alloy, and a protective layer formed on the substrate in this order. The reflection thin layer is made of an alloy such as a Cu-Ni alloy, a Cu-Al alloy or a Cu-Ni-Al alloy each having a defined composition.

Abstract: An optical resin material comprising a polymer containing as an essential component at least one norbornyl acrylate or methacrylate or a derivative thereof is excellent in properties, particularly in moisture resistance and can be used for molding optical elements such as lenses, optical discs, etc.

Abstract: A compatible optical disk in which information can be reproduced by a player normally used exclusively for reproduction, and writing, rewriting and erasure can be performed, comprises a recording film material characterized in that the reflectivity of a flat portion of the disk is lower than 50% in an erased or unrecorded state and the reflectivity of a recorded area is increased by recording by an irradiation of light, a light beam-guiding groove (12) formed on the surface of the disk substrate so that information is recorded or read out along the trough portion (12) or crest portion (17) of the guiding groove, and the reflectivity is enhanced in the crest portion (17) between the troughs or in the trough portion (12) between the crests.

Abstract: Disclosed is a process for producing an information recording medium of air-sandwich type for optically recording or reproducing information which comprises an information recording disc and hubs provided on both sides at the center thereof. In the process, using a receiving tool provided with a disc-shaped raised portion for receiving a substrate at its center and a hub-receiving center axis extended upward from the center, a circular hole of the disc is fitted to the raised portion of the receiving tool, then a magnetizable hub having a magnetizable substance and a clamping hole at the center is fitted coaxially to the recording disc, and the hub is joined to the disc. Thereafter, the disc joined with the hub is turned over and fitted onto other receiving tool, and the other hub is joined to the disc.

Abstract: An optical disc is disclosed in which a pair of circular disc substrates are arranged in confronted relation with each other with their signal recording layers being directed inwardly and are bonded to each other through spacers at inner and outer peripheral portions. A vent hole is formed in a main surface of one of the disc substrates. A disc label is bonded on the disc substrate so as to cover the vent hole.

Abstract: A process for manufacture of a second surface optically recordable disk is disclosed. A reflective sheet of aluminum, flow process produced by precipitation of a layer of aluminum from gasified triisobutyl aluminum onto a layer of molten indium, is mated with a polymer substratum sheet. In completion of the process, an optically active layer which is applied over the reflective layer is embossed with an optically transparent polycarbonate, protective cover, the mating surface of which, may be, pregrooved and coded with data relative to address and sector codes. Covers with bonded laminae are then successively severed from the lamina sheet to yield independent second surface optically recordable media.

Abstract: An improvement of an information recording medium comprising a disc-shaped resin substrate having an inner-side non-recording zone and an outer-side non-recording zone, a laser-sensitive recording layer, and a flexible resin film (for protection of the recording layer, having protruded and depressed portions on at least the surface facing the recording layer is disclosed. The improvement comprises joining the substrate and the flexible resin to each other on the inner-side and outer-side non-recording zones through fusion by ultrasonic welding or thermal welding in such manner that at least one joining of the flexible resin film to the substrate on the outer-side non-recording zone and the inner-side non-recording zone is effected through a fused portion in the form of a discontinuous ring.

Abstract: Recording and erasing optical information can be done by using an alloy film capable of forming two stable crystalline states differing in crystal texture and optical characteristics by being irradiated with optical energies under different conditions. The memory film includes 35-45 atom % of Indium (In) and 55-65 atom % of antimony (Sb).

Abstract: A process for producing an information recording medium such as an optical disc comprises the steps: putting a disc-shaped flexible resin film having a hole at its central part upon a surface of the recording layer-side of a disc-shaped resin substrate; placing them on a ultrasonic welding machine between its applying horn and its receiving tool in such a manner that the resin film and the applying horn are opposed to each other, wherein the horn has a ring-shaped protrusion provided with a raised portion; and applying ultrasonic wave to them while pressing the resin film to weld the resin film to the substrate.

Abstract: An optical resin consisting essentially of a radical polymerization polymer of an ethylenically unsaturated monomer, characterized in that at least a major part of the ethlenically unsaturated monomer is an ester of 1 mole of tricyclo[5,2,1,0.sup.2,6 ]decanedimethanol with 2 moles of a mixture of acrylic acid and metharcylic acid. Because the resin is a polymer obtained from the restricted monomer as specified above, the resin possesses high thermal resistance and high heat stability as well as low hygroscopic property. Dimethanol compounds from higher Diels-Alder adducts of cyclopentadine are also used in place of the tricyclo [5,2,1,0.sup.2,6 ]decanedimthanol which is a Diels-Alder adduct of two moles of cyclopentadiene.

Abstract: An optical information recording medium comprising a substrate, an optical recording layer formed over the surface of the substrate, and a protective layer covering the optical recording layer. The protective layer incorporates an antireflection means, such as a laser beam absorbing means, a laser beam scattering means or a laser beam transmitting means, for preventing the reflection of a laser beam applied to the optical recording layer.An optical information recording medium of a second embodiment of the present invention, comprises a substrate, an optical recording layer formed over the surface of the substrate, a protective layer covering the optical recording layer, and a buffer layer interposed between the optical recording layer and the protective layer.

Abstract: An arrangement is presented which permits a record chart bundle to be deflected into a recording position at a relatively short distance from an input slot of a respective recording device at an angle of approximately 90.degree.. For this purpose, a resilient, continuous transporting belt or a transporting belt pair driven by a motor is provided, deflecting rollers being assigned on the one hand and contact pressure rollers which are supported in a springing manner and engage in a working connection with a belt roller being assigned on the other hand to the transporting belt or transporting belt pair in such a way that a transfer gap between the belt rollers or between the transporting belts engaging around the belt rollers respectively, and the contact pressure rollers is located in the recording plane.

Abstract: An optical recording disc which includes a pair of recording disc substrates opposed to each other with a space therebetween, with a hub situated at the central portion of the disc substrates so that there is formed the closed space between the disc substrates, thereby providing a dual sided recordable optical recording disc. The hub may be formed by a pair of hub halves. There is disposed an annular inner spacer and annular outer spacer around the hub so as to separate the pair of recording disc substrates.

Abstract: A process for producing an information recording disc of an air sandwich structure by ultrasonic welding two disc substrates, at least one of which has a recording medium containing layer, to each other through outer and inner peripheral spacers lying therebetween, which process is characterized in that the outer peripheral spacer is first welded to the disc substrate on one side, the disc substrate on the other side is then superposed through the inner peripheral spacer on said outer peripheral spacer-welded disc substrate turned inside out, and said outer peripheral spacer and disc substrate on the other side, and said inner peripheral spacer and disc substrates on both sides are ultrasonic welded together simultaneously.

Abstract: The arrangement, according to the invention, includes a positioning drive with which a record chart bundle is drivable in a recording movement direction when it is received on a centering pin which can be raised and lowered, an adjustable stop which rotates at the recording speed and compensates for an angular difference between the recording angle per record chart and a complete revolution of this record chart, a catch arm, which is formed on at the stop, cooperating in turn with a radial edge of a sector-shaped cut-out portion of the uppermost record chart in the bundle during the positioning, the sector shape being conventional in record chart bundles, and driving means which are active when a record chart bundle is positioned and which couple the record chart bundle with the recording drive, the driving means being rotatably supported at a web which is movable vertically at the centering pin.

Abstract: A process for producing an information recording medium such as an optical disc comprises the steps of: putting a disc-shaped resin film having a hole at its central part upon a surface of a recording layer-side of a disc-shaped resin substrate having a hole at its center; and joining the resin film to the resin substrate by thermal welding in an outer-side non-recording zone of the substrate and by ultrasonic welding in an inner-side non-recording zone of the substrate.

Abstract: A clamp for attaching a plate such as a memory disk onto a spindle comprising a segmented clamp that may be withdrawn within the projected boundary of the interior hole in the disk for convenient unloading and a two part piston clamping means that applies a moderate clamping force followed by a larger clamping force.

Abstract: Stretched surface recording disk (SD) 10 comprises an annular support 12 having raised annular ridges 42 and 28 at its inside and outside diameters 22 and 30 with a base portion 24 in between the two ridges, and an annular recording medium film 14 held in radial tension and stretched across the base portion by adhering the film to attachment surfaces 48 and 36 near the inside and outside diameters respectively. The SD is annealed twice .[.duringmanufacture.]. .Iadd.during manufacture .Iaddend.to relieve stress in the stretched film 14. This annealing results in SD essentially free from track anisotropy and stress distribution anisotropy in the plane of the disk. As a result, data tracks are more stable than in previous SD, track density can be greater, and the SD is generally more reliable.