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 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%. A glass for use in chemical reinforcement for use in the substrate of an information recording medium employed in a perpendicular magnetic recording system, in which the glass exhibits the glass transition temperature is greater than or equal to 600° C.

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 method for manufacturing an optical glass element, comprising: annealing a press-molded product obtained by press molding into a lens shape a glass material comprised of a core portion comprised of an optical glass (first glass) with a transition temperature of 550° C. or higher and a covering portion comprised of a second glass covering the surface of said core portion; and then removing the covering layer from the surface of the press-molded product to obtain an optical glass element. To provide a method for manufacturing high-optical-performance mold-pressed lenses in which the defective external appearance of optical elements comprised of high-temperature glass materials with a Tg of 550° C. or higher is prevented.

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: An optical glass comprising, by mass %, 12 to 40% of SiO2, 15% or more but less than 42% of Nb2O5, 2% or more but less than 18% of TiO2, (provided that Nb2O5/TiO2 is over 0.6), 0.1 to 20% of Li2O, 0.1 to 15% of Na2O, and 0.1 to 25% of K2O, and having an Abbe's number ?d of 20 to 30, a ?Pg,F of 0.016 or less and a liquidus temperature of 1,200° C. or lower.

Abstract: An optical glass having high-refractivity and low-dispersion properties and containing, by mol %, 0.1 to 40% of SiO2, 10 to 50% of B2O3, wherein the mass ratio of the content of SiO2 to the content of B2O3, SiO2/B2O3, is 1 or less, 0.5 to 22% of ZnO, 5 to 50% of La2O3, and optionally other ingredients. The optical glass has a refractive index nd of 1.86 to 1.95 and an Abbe's number ?d of (2.36?nd)/0.014 or more but less than 38, and a glass transition temperature of equal to or greater than 640° C.

Abstract: A high-refractivity low-dispersion optical glass that can be stably supplied and has excellent glass stability and that has coloring reduced, composed of in mass %, 5 to 32% of total of SiO2 and B2O2, 45 to 65% of total of La2O2, Gd2O2 and Y2O2, 0.5 to 10% of ZnO, 1 to 20% of total of TiO2 and Nb2O5, and optionally other components. The optical glass has a refractive index nd of 1.89 to 2.0, an Abbe's number ?d of 32 to 38 and a coloring degree ?70 of 430 nm or less.

Abstract: An optical glass that is an oxide glass having a very high refractive index in spite of its low-dispersion property, having excellent glass stability and having less susceptibility to coloring.

Abstract: A glass material for mold pressing, comprised of a core portion and a covering portion. In one embodiment, the core portion comprises a multicomponent optical glass containing at least one readily reducible component selected from among W, Ti, Bi, and Nb and the covering portion comprises a multicomponent glass containing none or a lower quantity of the readily reducible component than is contained in the core portion. In another embodiment, the core portion comprises a fluorine-containing multicomponent optical glass, and the covering portion comprises a multicomponent glass containing none or a lower quantity of fluorine than is contained in the core portion. A method for manufacturing an optical glass element employing the above glass material that comprises heat softening a glass material that has been preformed into a prescribed shape, and conducting press molding with a pressing mold.

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 method for manufacturing a disklike glass material comprising the successive molding of multiple pieces of disklike glass material from glass melt. Being suppressed variation over time in the concentration of infrared radiation-absorbing ions contained in the glass melt being molded into the pieces of disklike glass material so that the variation in the sheet thickness of the multiple pieces of disklike glass material falls within a range of ±15 percent of a reference value. The reference value being the median between the maximum value and the minimum value of the sheet thickness of 1,000 pieces of the glass material. In the course of molding multiple pieces of disklike glass material comprised of glass containing 0.1 to 100 ppm of infrared radiation-absorbing ions, vaiiation over time in the concentration of the infrared radiation-absorbing contained in the glass melt is suppressed to suppress variation in the sheet thickness of the multiple pieces of sheet like glass material.

Abstract: A high-refractivity low-dispersion optical glass that can be stably supplied and has excellent glass stability and that has coloring reduced, composed of in mass %, 5 to 32% of total of SiO2 and B2O2, 45 to 65% of total of La2O2, Gd2O2 and Y2O2, 0.5 to 10% of ZnO, 1 to 20% of total of TiO2 and Nb2O5, and optionally other components. The optical glass has a refractive index nd of 1.89 to 2.0, an Abbe's number ?d of 32 to 38 and a coloring degree ?70 of 430 nm or less.

Abstract: An optical glass comprising, by mass %, 12 to 40% of SiO2, 15% or more but less than 42% of Nb2O5, 2% or more but less than 18% of TiO2, (provided that Nb2O5/TiO2 is over 0.6), 0.1 to 20% of Li2O, 0.1 to 15% of Na2O, and 0.1 to 25% of K2O, and having an Abbe's number ?d of 20 to 30, a ?Pg,F of 0.016 or less and a liquidus temperature of 1,200° C. or lower.

Abstract: An optical glass having high-refractivity and low-dispersion properties and containing, by mol %, 0.1 to 40% of SiO2, 10 to 50% of B2O3, wherein the mass ratio of the content of SiO2 to the content of B2O3, SiO2/B2O3, is 1 or less, 0.5 to 22% of ZnO, 5 to 50% of La2O3, and optionally other ingredients. The optical glass has a refractive index nd of 1.86 to 1.95 and an Abbe's number vd of (2.36?nd)/0.014 or more but less than 38, and a glass transition temperature of equal to or greater than 640° C.

Abstract: A high-refractivity low-dispersion optical glass that can be stably supplied and has excellent glass stability and that has coloring reduced, composed of in mass %, 5 to 32% of total of SiO2 and B2O3, 45 to 65% of total of La2O3, Gd2O3 and Y2O3, 0.5 to 10% of ZnO, 1 to 20% of total of TiO2 and Nb2O5, and optionally other components. The optical glass has a refractive index nd of 1.89 to 2.0, an Abbe's number ?d of 32 to 38 and a coloring degree ?70 of 430 nm or less.

Abstract: Disclosed is a glass material for press forming providing an optical element having a sufficient optical performance without surface cracks, cloudiness, scratches, and the like even when the glass material contains a highly reactive component. Also disclosed are an optical element having a sufficient optical performance without surface cracks, cloudiness, scratches, and the like and a method for manufacturing the same. Specifically disclosed is a glass material for press forming which comprises a core portion composed of multicomponent optical glass and a surface glass layer covering at least a region serving as an optical functional surface of the core portion. The surface glass layer contains more than 90 mass % of SiO2, and the thickness of the layer is less than five nanometers. Also specifically disclosed is a method for manufacturing a glass optical element by heating the glass material and by press forming the softened glass material using a forming die.

Abstract: An optical glass comprising, by mass %, 12 to 40% of SiO2, 15% or more but less than 42% of Nb2O5, 2% or more but less than 18% of TiO2, (provided that Nb2O5/TiO2 is over 0.6), 0.1 to 20% of Li2O, 0.1 to 15% of Na2O, and 0.1 to 25% of K2O, and having an Abbe's number ?d of 20 to 30, a ?Pg,F of 0.016 or less and a liquidus temperature of 1,200° C. or lower.

Abstract: An optical glass comprising, by mol %, 0.1 to 40% of SiO2, 10 to 50% of B2O3, 0 to 10% of total of Li2O, Na2O and K2O, 0 to 10% of total of MgO, CaO, SrO and BaO, 0.5 to 22% of ZnO, 5 to 50% of La2O3, 0.1 to 25% of Gd2O3, 0.1 to 20% of Y2O3, 0 to 20% of Yb2O3, 0 to 25% of ZrO2, 0 to 25% of TiO2, 0 to 20% of Nb2O5, 0 to 10% of Ta2O5, over 0.1% but not more than 20% of WO3, 0 to less than 3% of GeO2, 0 to 10% of Bi2O3, and 0 to 10% of Al2O3, the mass ratio of the content of SiO2 to the content of B2O3, SiO2/B2O3, being 1 or less, the optical glass having a refractive index nd of 1.86 to 1.95 and an Abbe's number ?d of (2.36?nd)/0.014 or more but less than 38.

Abstract: An optical glass that is an oxide glass having a very high refractive index in spite of its low-dispersion property, having excellent glass stability and having less susceptibility to coloring.