Abstract: According to one aspect of the present invention, provided is glass for use in substrate for information recording medium, which comprises, denoted as molar percentages, a total of 70 to 85 percent of SiO2 and Al2O3, where SiO2 content is equal to or greater than 50 percent and Al2O3 content is equal to or greater than 3 percent; a total of equal to or greater than 10 percent of Li2O, Na2O and K2O; a total of 1 to 6 percent of CaO and MgO, where CaO content is greater than MgO content; a total of greater than 0 percent but equal to or lower than 4 percent of ZrO2, HfO2, Nb2O5, Ta2O5, La2O3, Y2O3 and TiO2; with the molar ratio of the total content of Li2O, Na2O and K2O to the total content of SiO2, Al2O3, ZrO2, HfO2, Nb2O5, Ta2O5, La2O3, Y2O3 and TiO2 ((Li2O+Na2O+K2O)/(SiO2+Al2O3+ZrO2+HfO2+Nb2O5+Ta2O5+La2O3+Y2O3+TiO2)) being equal to or less than 0.28.

Abstract: A polymer thin film in which cylindrical phases are distributed in a continuous phase and are oriented in a pass-through-direction of the film includes at least: a first block copolymer including at least a block chain A1, as a component of the continuous phase, composed of polymerized monomers a1, and a block chain B1, as a component of the cylindrical phases, composed of polymerized monomers b1; and a second block copolymer including at least a block chain A2, as a component of the continuous phase, composed of polymerized monomers a2, and a block chain B2, as a component of the cylindrical phases, composed of polymerized monomers b2, with the second copolymer having a degree of polymerization different from that of the first copolymer. A film thickness of the polymer thin film and an average center distance between adjacent cylindrical phases have a relation represented by a predetermined expression.

Abstract: There is provided a method for fabricating a magnetic recording medium that provides high throughput, low manufacturing cost, and no degradation in accuracy in pattern size in fine pattern formation. A resist layer is formed on a substrate or cutting work layer. The surface of the substrate is divided into two or more areas using the center of rotation of the substrate as a reference point. An optical, contactless pattern transfer method is used to transfer a figure pattern contained in the divided area through a mask to the resist layer so as to form a latent image of the figure pattern. The pattern transfer is similarly carried out for the divided area. After the pattern transfer processes for all the divided areas are completed, the entire resist layer is developed to form a resist pattern. The resist pattern is used as a mask to cut the substrate or cutting work layer. As a result, there is provided the substrate or cut work layer onto which a fine pattern has been transferred.

Abstract: An information medium substrate is formed as a flat plate and includes a first convex part formed on one surface of the information medium substrate in a region between a rim part of a center hole and an inner circumferential edge of an information region and a second convex part formed on another surface of the information medium substrate at a position that overlaps a protruding end part of the first convex part in a thickness direction of the information medium substrate.

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: A main surface of a glass substrate for a magnetic disk is disk-shaped and has a ski jump on an outer peripheral end portion of the main surface opposing a magnetic head slider to be loaded. A rate of change of angles of tangents to a slope of the ski jump in a radial direction in a range between an inner circumferential side and a transition point on the slope is equal to or less than 10/W ?rad/mm where W is a width of the magnetic head slider.

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 invention uses an adhesion layer of an amorphous alloy of aluminum. A first aluminum titanium embodiment of the amorphous adhesion layer preferably contains approximately equal amounts of aluminum and titanium (+/?5 at. %). A second embodiment of the amorphous adhesion layer preferably contains approximately equal amounts of aluminum and titanium (+/?5 at. %) and up to 10 at. % Zr with 5 at. % Zr being preferred. A third embodiment is aluminum tantalum preferably including from 15 to 25 at. % tantalum with 20 at. % being preferred. The most preferred compositions are Al50Ti50, Al47.5Ti47.5Zr5 or Al80Ta20. The adhesion layer is deposited onto the substrate. The substrate can be glass or a metal such as NiP-plated AlMg. The preferred embodiment of media according to the invention is for perpendicular recording and includes a magnetically soft underlayer deposited above the adhesion layer.

Abstract: A glass for use in chemical reinforcement for use in a substrate of an information recording medium, having a composition comprising, denoted as mol %: SiO2 47 to 70%? Al2O3 1 to 10% (where the total of SiO2 and Al2O3 is 57 to 80%) CaO 2 to 25% BaO 1 to 15% Na2O 1 to 10% K2O 0 to 15% (where the total of Na2O and K2O is 3 to 16%) ZrO2 1 to 12% MgO 0 to 10% SrO 0 to 15% (where the ratio of the content of CaO to the total of MgO, CaO, SrO, and BaO is greater than or equal to 0.5) ZnO 0 to 10% (where the total of MgO, CaO, SrO, BaO, and ZnO is 3 to 30%) TiO2 0 to 10% and the total content of the above-stated components is greater than or equal to 95%.

Abstract: An aspect of the present invention relates to a magnetic recording medium comprising a coating layer on a nonmagnetic support, wherein the coating layer comprises a nonmagnetic layer comprising a nonmagnetic powder and a binder and a magnetic layer comprising a ferromagnetic powder and a binder in this order, the nonmagnetic support comprises a main component in the form of a resin obtained by mixing and/or copolymerizing a polyester and a polymer having compatibility with the polyester, has a glass transition temperature of equal to or higher than 80° C. but less than 125° C., and has a heat absorption peak, based on enthalpy relaxation, ranging from 0.5 to 2.0 J/g. Another aspect of the present invention relates to a method of manufacturing a magnetic recording medium.

Abstract: A perpendicular magnetic recording medium comprising a pair of soft magnetic layers that are laminated via a non-magnetic layer and antiparallel-coupled to each other and that are provided between a non-magnetic substrate and a magnetic recording layer, wherein spike noise and medium noise can be positively suppressed when information recording and reproduction are carried out at high recording surface density. At least one pair of soft magnetic layers are laid and formed via a non-magnetic layer on a substrate of a non-magnetic material so that magnetic characteristics obtained by integrating the pair of soft magnetic layers have a magnetic hysteresis to thereby prevent the formation of a magnetic domain wall.

Abstract: An object of the present invention is to provide a method of manufacturing a glass substrate containing alkali metals. A glass substrate manufactured by the method exhibits excellent performances including durability by virtue of suppressing elution of alkali metals. A method comprises a step of immersing a glass material in an aqueous solution containing a formate to suppress elution of component of the glass material.

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?2.0 (kg/mm).

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: A magnetic recording medium substrate has a polyester film having metallic oxide-containing layers (layers M) formed on both the surfaces, one layer on each surface, the layers M having a thickness of 50 to 200 nm each, characterized in that the magnetic recording medium substrate has a total light transmittance of 0 to 75% and a surface resistivity of 1×102 to 1×1013? on each surface.

Abstract: Substrates for perpendicular magnetic recording media, and perpendicular magnetic recording media using such substrates, are disclosed. By setting the substrate inclination angle, or a parameter related to substrate shape relating to this angle, within an appropriate range, magnetic recording media can be obtained with excellent read signal quality and signal quality stability, regardless of the final substrate machining method.

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 a CeO2 crystal powder, the CeO2 crystal powder being obtained in such a manner that a melt containing CeO2 is quenched to obtain an amorphous material, and the amorphous material is subjected to heat treatment to obtain a CeO2 crystals-precipitated amorphous material, which is subjected to acid treatment to separate and extract the CeO2 crystal powder from the CeO2 crystals-precipitated amorphous material.

Abstract: The present invention relates to a magnetic disk substrate, in which an amplitude Wa of a waviness on a surface measured by using an interferometer for a versatile disk at a measuring wave-length of 5.0 mm is within the range of 0.1 nm to 0.5 nm, an average amplitude Wb of a microwaviness generated on the waviness measured by using a microscopy for three-dimensional surface-structural analysis at a measuring wave-length of 30 ?m to 200 ?m is 0.3 nm or less, and a value calculated by dividing the average amplitude Wb of the microwaviness by the amplitude Wa of the waviness is 0.6 or more.

Abstract: In this invention, etching is not performed in the step of planarizing a polycrystalline Si wafer, but only mechanical grinding is performed for planarization. This is because, since the etching rate is crystal-face dependent, etching of the polycrystalline Si wafer unavoidably results in formation of steps due to different crystal face orientations of individual crystal grains exposed on a surface of the wafer, thus hindering precision surface planarization. Subsequently, the Si wafer surface is coated with an oxide film to form an Si wafer with oxide film prior to the final polishing stage and then a surface of the oxide film is planarized, to give a planar substrate (i.e., Si substrate with oxide film) having no step on the surface thereof.

Abstract: An information-storage media is provided that includes: (a) a substrate disk 312 having first and second opposing surfaces; (b) a first selected layer 304 on the first surface, the first selected layer having a first thickness; (c) a second selected layer 308 on the second surface, the second selected layer having a second thickness, wherein the first and second selected layers have a different chemical composition than the substrate disk; and (d) an information-storage layer 412 adjacent to one or both of the selected layers. The first and second thicknesses are different to provide an unequal stress distribution across the cross-section of the media.