Abstract: The object of the invention is to provide a method of polishing the end surfaces of a substrate for a recording medium, which is capable of efficiently polishing the inner peripheral end surface and/or the outer peripheral end surface of the substrate preventing the reliability of performance of the recording medium from being impaired by the adhesion of the residual polishing material. According to the invention, there is provided a method of polishing end surfaces of a substrate for a recording medium wherein an inner peripheral end surface or an outer peripheral end surface of a substrate for a disk-like recording medium having a circular hole at the central portion thereof is brought into contact with a polishing medium obtained by dispersing polishing grains in a viscoelastic resin carrier and the polishing medium flows, thereby to polish the inner peripheral end surface or the outer peripheral end surface.

Abstract: There is provided a glass substrate for a magnetic disk in which a maximum height of bumps forming a roughness pattern at a period of smaller than 2 ?m is 6 nm or lower in an annular area having a width of 30 ?m on a main surface on which a magnetic recording area is formed, a number of bumps having a height of 3 nm or higher in a unit area having a circular arc length of 30 ?m within the annular area is one or less, and a difference in arithmetic average roughness between unit areas within the annular area is 0.2 nm or smaller.

Abstract: The present invention is a magnetic recording medium substrate made of amorphous glass of B2O3—Al2O3—SiO2—Li2O type, wherein a chamfer is formed between an edge face at an outer circumference side or an inner circumference side of the substrate and a principal plane of the substrate, and a content of sodium and potassium at a surface area of the inner or outer circumference side edge face and a surface area of the chamfer is greater than a mean content of sodium and potassium of the magnetic recording medium substrate. With the present invention, it is possible to prevent generation of projections on a magnetic film, a protective film or the like due to movement of lithium ions in a magnetic recording medium substrate made of amorphous glass which includes lithium.

Abstract: A method for producing a glass substrate for a magnetic disk by polishing a circular glass plate, which comprises a step of polishing the principal plane of the circular glass plate by using a slurry containing at least one water-soluble polymer selected from the group consisting of a water-soluble organic polymer having amino groups, a water-soluble organic polymer having amine salt groups and a water-soluble organic polymer having quaternary ammonium salt groups, and colloidal silica.

Abstract: A substrate for use as a disk substrate in a hard disk drive or the like, an information recording medium such as a magnetic disk, and a starting material glass plate which is a starting material of the substrate for information recording media. The forming conditions of the starting material glass plate are controlled such that the starting material glass plate has a long-wavelength waviness of not more than 6 nm. This starting material glass plate is polished so as to have a long-wavelength waviness of not more than 6 nm using CeO2 abrasive grains having a mean grain diameter of not less than 0.01 ?m and a 90% diameter of the volume grain size distribution of not less than 0.02 ?m. The resulting substrate for an information recording medium has an excellent planarity, can be obtained in a short time and with a low polishing amount, and the resulting information recording medium is able to cope with increased data zone recording density.

Abstract: A substrate for an information recording medium, which has high heat resistance and high acid resistance and is formed of a glass having a glass transition temperature (Tg) of 600° C. or higher and having an etching rate of 0.1 ?m/minute or less with regard to a hydrosilicofluoric acid aqueous solution that is maintained at a temperature of 45° C. and has a hydrosilicofluoric acid concentration of 1.72% by weight, and an information recording medium having an information recording layer formed on the above substrate.

Abstract: Provided are a glass substrate for an information recording medium, which has both high strength and high flatness and can be manufactured at low cost, a method for manufacturing such glass substrate and an information recording medium using such glass substrate. The glass substrate for the information recording medium satisfies inequalities of 0.1?(W1?W3)/W2?5, where, W1 is an ion concentration at the center portion in the thickness direction of the glass substrate in a chemically reinforced region at the outer circumference end surface and the inner circumference end surface of the glass substrate and is the maximum value of K+ ion concentration, W2 is a Na+ ion concentration at a position where the K+ ion concentration is maximum, and W3 is a K+ ion concentration in a glass substrate region not chemically reinforced.

Abstract: To provide glass for a data storage medium substrate, whereby high heat resistance can be obtained. Glass for a data storage medium substrate, which comprises, as represented by mol percentage based on the following oxides, from 55 to 70% of SiO2, from 2.5 to 9% of Al2O3, from 0 to 10% of MgO, from 0 to 7% of CaO, from 0.5 to 10% of SrO, from 0 to 12.5% of BaO, from 0 to 2.5% of TiO2, from 0.5 to 3.7% of ZrO2, from 0 to 2.5% of Li2O, from 0 to 8% of Na2O, from 2 to 8% of K2O and from 0.5 to 5% of La2O3, provided that the total content of Al2O3 and ZrO2 (Al2O3+ZrO2) is at most 12%, and the total content of Li2O, Na2O and K2O (R2O) is at most 12%.

Abstract: A plurality of recording magnetization portions is arranged in a concentric manner around a center of a glass substrate. A plurality of non-magnetization portion having a thermal conductivity lower than that of the recording magnetization portions is formed each between adjacent recording magnetization portions along a circumferential direction on a main surface of the glass substrate. A mean squared roughness of a surface of an area where each of the non-magnetization portions is formed is equal to or smaller than 1 nanometer.

Abstract: The present invention provides an inorganic composition for use in information recording medium disc substrate and such, having an excellent surface property capable of sufficiently corresponding with a ramp load system for high density recording, a high degree of tolerability to high speed rotation, and high productivity at a low melting point. Specifically, this invention provides an inorganic composition containing one crystalline phase selected from the group consisting of ?-quartz (?-SiO2), lithium disilicate (Li2Si2O5) and lithium monosilicate (Li2SiO3), or that contain at least a crystalline phase of lithium monosilicate (Li2SiO3), in which a mean particle diameter of a particle showing a crystalline phase contained in the inorganic composition is 1 ?m or less, a ring flexural strength is 300 MPa or more, and a surface roughness (an arithmetic mean roughness) thereof after a polishing process is 10 ? or less.

Abstract: A perpendicular magnetic recording medium having a soft magnetic backing layer is disclosed. The medium has reduced Co elution, improved corrosion resistance, and satisfactory electromagnetic transducing characteristics, without providing constraints on the configuration of the protective layer such as, for example, the thickness of the protective layer, film deposition processes or layer configuration.

Abstract: Disclosed are a glass substrate for an information recording medium, having excellent scratch resistance and a light weight and having high fracture toughness, the glass substrate having a fragility index value, measured in water, of 12 ?m?1/2 or less or having a fragility index value, measured in an atmosphere having a dew point of ?5° C. or lower, of 7 ?m?1/2 or less, or the glass substrate comprising, by mol %, 40 to 75% of SiO2, 2 to 45% of B2O3 and/or Al2O3 and 0 to 40% of R?2O in which R? is at least one member selected from the group consisting of Li, Na and K), wherein the total content of SiO2, B2O3, Al2O3 and R?2O is at least 90 mol %, and a magnetic information recording medium comprising a magnetic recording layer formed on the glass substrate.

Abstract: A chemically strengthened glass substrate for use as the substrate of an information recording medium such as a magnetic disk, magneto-optical disk, DVD, or MD, wherein a strengthened formed by chemical strengthening exists on the outer edge surface and on the inner edge surface but substantially not on a surface on which an information recording layer is formed.

Abstract: A glass substrate for a magnetic recording medium, having a chamfer face between the surface of the substrate for forming thereon a film comprising a magnetic layer, and the outer peripheral end face (straight face) of the substrate, wherein an R face having a curvature of 0.013 to 0.080 mm is provided between the data face and the chamfer face of the glass substrate.

Abstract: The present invention provides a magnetic recording medium which enables improvement of the layer quality of magnetic layer grown on the surface of a soft magnetic underlayer by conducting excellent control of crystal orientation by imparting an optimal half-width of the Rocking curve (??50), as well as obtainment of SNR that suppresses generation of TA and enables realization of high-density recording. The magnetic recording medium includes a soft magnetic underlayer, an orientation control layer, a perpendicular magnetic recording layer, and a protective layer, which are disposed on top of a non-magnetic substrate; wherein the magnetic anisotropy ratio (Hmr/Hmc) of the soft magnetic underlayer is 1 or less, and ??50 is 1 to 6 degrees.

Abstract: A magnetic recording media with a multilayer structure and methods for forming the media are described. The magnetic recording media includes a substrate, an underlayer on top of the substrate and a magnetic layer over the underlayer. The underlayer includes a CrN film formed by sputter depositing chromium in the presence of nitrogen or nitrogen containing compounds.

Abstract: A glass substrate for a magnetic disk satisfies Ra1?0.8 [nm], 0 [nm]?Ra1?Ra2?0.2 [nm], Wa1?0.6 [nm], and 0 [nm]?Wa2?Wa1?0.2 [nm]. Ra1 is an average surface roughness of a first annular area between 1 mm and 3 mm outward from an inner periphery of a main surface of the glass substrate, Ra2 is an average surface roughness of a second annular area between 1 mm and 3 mm inward from an outer periphery of the main surface, Wa1 is an average waviness of the first area in a circumferential direction of the glass substrate having a cycle of 300 ?m to 5 mm, and Wa2 is an average waviness of the second area in the circumferential direction having a cycle of 300 ?m to 5 mm.

Abstract: The invention can provide a production method for a magnetic disk substrate capable of reducing the number of surface defects of a glass substrate. When a magnetic disk is produced by using the resulting magnetic disk substrate, the yield and, furthermore, the reliability can be improved. When a surface of a magnetic disk substrate is washed after it is polished, the glass substrate is dipped into a washing solution while the surface of the glass substrate polished is held under a wet condition. The wet condition of the surface of the glass substrate includes a condition in which the glass substrate is dipped into water that may contain a surfactant, and a condition in which a liquid film is formed substantially on the entire surface.

Abstract: The perpendicular magnetic recording medium of the present invention includes a substrate, a non-magnetic layer, a ferromagnetic layer and an antiferromagnetic oxide. The non-magnetic layer is formed on the substrate and the ferromagnetic layer is formed on the non-magnetic layer. The antiferromagnetic oxide is formed in the ferromagnetic layer after the perpendicular magnetic recording medium is annealed by an annealing process. An exchange coupling interaction between the antiferromagnetic oxide and the ferromagnetic materials is introduced.

Abstract: Provided is a surface-treated substrate in which the roughness of the surface of the substrate is controlled. The surface-treated substrate can form a magnetic recording medium in which head flying stability is maintained and which has a magnetic film that can achieve high recording densities. Also provided is a method for roughening the surface of the substrate. More specifically, provided is a surface-treated silicon substrate for a magnetic recording medium in which a surface used for forming a recording layer has 40 to 1000 protrusions per 1 ?m2 with a maximum height of 10 nm or less and an average roughness of 0.3 to 2.0 nm, and in which there are no defects or spots on any of the surface. Furthermore, provided is a method for manufacturing the surface-treated silicon substrate for the magnetic recording medium, comprising a step of etching a surface of a silicon substrate, wherein ultrasound is applied to the surface of the silicon substrate with the substrate shaken or rotated.

Abstract: A glass substrate for a magnetic recording medium is formed to have a disc shape and includes ridge shaped textures 13 extending along concentric circles on a main surface. When measuring a 10 ?m square range with an atomic force microscope, the textures have a width W that is between 10 and 200 nm. The textures have a height H that is between 2 and 10 nm. Further, the textures have a ratio (Rp/RMs) of a maximum mountain height with respect to a root mean square roughness that is less than or equal to 15. The textures include high frequency components superimposed on the low frequency components. It is preferable that the textures of the high frequency components have a width W? that is between 0.1 and 20 nm, and the textures of the high frequency components have a height H? that is between 0.1 and 1 nm.

Abstract: A substrate for an information recording medium, which substrate is made of a highly heat-resistant and low-alkali-elution glass and is suitable as a substrate for forming a perpendicular-magnetic-recording-mode layers thereon at a high temperature with a sputtering machine, the substrate being made of an alkali-metal-oxide-containing glass having a glass transition temperature (Tg) of 620° C. or higher and satisfying a requirement that the alkali ion elution amount per a unit area when the glass is immersed in water having a temperature of 80° C. for 24 hours is 0.2 ?mol/cm2 or less, an information recording medium having an information recording layer formed on the substrate, and a process for producing the information recording medium.

Abstract: This magnetic recording medium has a substrate, a nonmagnetic granular layer formed above the substrate and a recording layer formed on the nonmagnetic granular layer. The nonmagnetic granular layer is made of CoCr alloy with an hcp or an fcc crystal structure in which a nonmagnetic material segregates virtually-columnar magnetic grains. The magnetic recording medium and the magnetic storage apparatus in which the medium is used have improved reading/writing performances.

Abstract: Glass-ceramics include SiO2, Al2O3 and Li2O on oxide basis. In the glass-ceramics, total amount in mass % of SiO2 and Al2O3 is less than 77% and Li2O/(SiO2+Al2O3) which is the ratio in mass % of the amount of Li2O to the total amount of SiO2 and Al2O3 is 0.064 or over. The glass-ceramics include at least one crystal phase selected from the group consisting of ?-quartz, ?-quartz solid solution, ?-eucryptite, ?-eucryptite solid solution, ?-spodumene and ?-spodumene solid solution.

Abstract: Provided is a perpendicular magnetic recording medium and a method of manufacturing the same. The perpendicular magnetic recording medium includes a substrate, a buffer layer formed on the substrate, a soft magnetic underlayer formed on the buffer layer, and a recording layer formed on the soft magnetic underlayer.

Abstract: A magnetic disk glass substrate including compressive stress layers at main surfaces and a tensile stress layer between the compressive stress layers formed by chemical strengthening. When the glass substrate has a thickness of less than 0.5 mm and the tensile stress layer has a thickness L and a tensile stress of Pt (kg/mm2), the following relation holds: 0.4 (kg/mm)?L·Pt?2.

Abstract: A glass substrate for a magnetic recording medium, having a chamfer face between the surface (data face) of the substrate for forming thereon a film comprising a magnetic layer, and the outer peripheral end face (straight face) of the substrate, wherein the outer peripheral chamfer face has a dub-off of 120 ? or less in the radial direction.

Abstract: A method for producing a glass substrate for a magnetic disk by polishing a circular glass plate, which comprises a step of polishing the principal plane of the circular glass plate by using a slurry containing at least one water-soluble polymer selected from the group consisting of a water-soluble organic polymer having amino groups, a water-soluble organic polymer having amine salt groups and a water-soluble organic polymer having quaternary ammonium salt groups, and colloidal silica.

Abstract: A glass substrate of the present invention for magnetic recording media having high heat resistance and easy chemical strengthening ability at once has not been obtained, which is a glass composition essentially comprising 60 to 70 wt % SiO2, 5 to 20 wt % Al2O3, 0 to 1 wt % Li2O, 3 to 18 wt % Na2O, 0 to 9 wt % K2O, 0 to 10 wt % MgO, 1 to 15 wt % CaO, 0 to 4.5 wt % SrO, 0 to 1 wt % BaO, 0 to 1 wt % TiO2 and 0 to 1 wt % ZrO2, wherein the sum of Li2O, Na2O and K2O is from 5 to 25 wt %, and the sum of MgO, CaO, SrO and BaO is from 5 to 20 wt %.

Abstract: The invention relates to crystallizable aluminosilicate magnesium-containing glass which is used for producing extremely solid and break-resistant glass-ceramics having an easily polished surface. The inventive crystallizable glass contains 5-33 mass % of SiO2, 25-40 mass % of Al2O3, 5-25 mass % of MgO, 0-15 mass % of B2O3, 0.1-30 mass % of Y2O3, Ln2O3, As2O3 and/or Nb2O5 and 0.1-10 mass % of P2O5.

Abstract: An information storage apparatus includes a storage media including a plurality of information tracks. Each storage medium has a head assembly having a substantially planar surface and a plurality of read/write heads positioned in registry with the information tracks. The read/write heads are arranged substantially in the plane of the planar surface. The information storage medium and the head assembly are arranged in mutually sliding abutment such that the heads are substantially in sliding contact with the outer surface of the information storage medium. In another aspect an information storage and retrieval apparatus includes an information storage medium including an information storage area, and an array of information read/write heads. The information storage medium and array of heads are arranged to be oscillated with respect to each other in use such that each region of the information storage area is aligned with at least one of the heads during oscillation.

Abstract: The present invention provides a glass composition that has excellent heat resistance and ion exchange ability and can be provided with high strength by a chemical strengthening treatment through an ion exchange. This glass composition includes, in terms of mass %: 59 to 68% of SiO2; 9.5 to 15% of Al2O3; 0 to 1% of Li2O; 3 to 18% of Na2O; 0 to 3.5% of K2O; 0 to 15% of MgO; 1 to 15% of CaO; 0 to 4.5% of SrO; 0 to 1% of BaO; 0 to 2% of TiO2; and 1 to 10% of ZrO2. The glass composition of the present invention is suitable for a glass substrate for magnetic recording media and also can be formed as a chemically strengthened glass article through an ion-exchange treatment.

Abstract: Enclosed are crystallized glasses suitable for a substrate for an information recording medium such as a magnetic disc, optical disc, or optomagnetic disc, a substrate for information recording medium using such a crystallized glass substrate, and an information recording medium using such a substrate for information recording medium. The crystallized glasses are capable of providing a glass substrate having a high Young's modulus, as well as excellent mechanical strength, surface flatness, and heat resistance and having an excellent surface smoothness upon polishing. Glass substrate having an excellent surface smoothness using such a crystallized glass are also disclosed.

Abstract: On a principal surface of a glass disk substrate, a texture comprising a combination of an isotropic texture for stabilizing a flight of a magnetic head flying and traveling over a magnetic disk and an anisotropic texture for imparting a magnetic anisotropy to a magnetic layer of the magnetic disk is formed.

Abstract: A substrate for a magnetic recording medium made of a glass or crystallized glass which has a specified spectral light transmittance and a process for producing an information recording medium.

Abstract: A glass substrate for use as the substrate of an information recording medium such as a magnetic disk, magneto-optical disk, DVD, or MD or of an optical communication device, and a glass composition for making such a glass substrate, contains the following glass ingredients: 45 to 75% by weight of SiO2; 1 to 20% by weight of Al2O3; 0 to 8% by weight, zero inclusive, of B2O3; SiO2+Al2O3+B2O3 accounting for 60 to 90% by weight; a total of 0 to 20% by weight, zero inclusive, of R2O compounds, where R=Li, Na, and K; and a total of 0 to 15% by weight, zero inclusive, of TiO2+ZrO2+LnxOy, where LnxOy represents at least one compound selected from the group consisting of lanthanoid metal oxides, Y2O3, Nb2O5, and Ta2O5.

Abstract: A member of supporting magnetic disc substrates is provided, comprising a ceramic sinter containing a ceramic component and at least one conductive component selected from a group consisting of iron, niobium, tin zinc, copper, nickel, cobalt, and chromium, wherein the ceramic sinter has conductive aggregates on its peripheral surface. In the member, the ceramic component may be forsterite and the conductive component is iron oxide, wherein the ceramic sinter comprises a main phase of 2MgO.SiO2 and a secondary phase of at least one of MgFe2O4, Fe3O4 and Fe2O3.

Abstract: Disclosed are a glass substrate for an information recording medium, having excellent scratch resistance and a light weight and having high fracture toughness, the glass substrate having a fragility index value, measured in water, of 12 ?m?1/2 or less or having a fragility index value, measured in an atmosphere having a dew point of ?5° C. or lower, of 7 ?m?1/2 or less, or the glass substrate comprising, by mol %, 40 to 75% of SiO2, 2 to 45% of B2O3 and/or Al2O3 and 0 to 40% of R?2O in which R? is at least one member selected from the group consisting of Li, Na and K), wherein the total content of SiO2, B2O3, Al2O3 and R?2O is at least 90 mol %, and a magnetic information recording medium comprising a magnetic recording layer formed on the glass substrate.

Abstract: There are provided low expansion transparent glass-ceramics obtained by heat treating a base glass produced at a relatively low melting temperature of 1530° C. or below. The glass-ceramics have an average linear thermal expansion coefficient within a range from +6×10?7/° C. to +35×10?7/° C., 80% transmittance wavelength (T80) of 700 nm or below internal transmittance of 75% or over at light wavelength of 1550 nm, heat resisting temperature of 800° C. or over and Young's modulus of 90 GPa or over. The glass-ceramics comprise SiO2, Al2O3, MgO, CaO, BaO, ZnO, Li2O, TiO2 and ZrO2 and contain ?-quartz or ?-quartz solid solution as a predominant crystal phase.

Abstract: Provided is a substrate for information recording medium composed of such a crystallized glass as having high Young's modulus, strength and heat resistance, being excellent in surface smoothness, surface homogeneity and surface processability, as well as having a relatively low temperature of glass liquid phase and being capable of producing cheaply, and an information recording medium using this substrate. The crystallized glass substrate for information recording medium comprising 35–65 mol % of SiO2, 5–25 mol % of Al2O3, 10–40 mol % of MgO and 5–15 mol % of TiO2, in which the total amount of aforementioned composition is at least equal to or higher than 92 mol % and the main crystals are enstatite and/or its solid solution. The information recording medium having this substrate and a recording layer formed on said substrate.

Abstract: A magnetic recording medium which includes a substrate having a front side and a backside, a longitudinal direction and a cross-web direction, with a particulate/binder or thin film magnetic layer formed over the front side of the substrate, wherein the magnetic medium has a cross-web dimensional difference from the magnetic recording head used therewith of less than 900 ?m/meter over a 35° C. temperature range, and over a 70% relative humidity range. Preferred substrates include thin metals, metal alloys, and thin glass films.

Abstract: A method of manufacture of thin film magnetic disks and other useful articles of similar planar geometry in which a non-magnetic layer is first deposited on one or both sides of the disk or article substrate to mask chemical and mechanically induced heterogeneities introduced by pre-polishing to achieve a smooth finish, typically resulting in cold-working of the surface, and to also bind to the substrate and is then coated with a thin layer of metal selected to either reactively or catalytically initiate smooth, electroless deposition of a non-magnetic nickel alloy which is subsequently polished and coated with additional thin layers to provide magnetic read-write capability. A disk drive using one or more of such disks is provided.