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: 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, La2O3Y2O3 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: 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: Provided are a process for the production of a precision press-molded article having a high transmittance a method of treating a glass to color or decolor the glass, the process comprising heat-treating a press-molded article containing at least one selected from WO3, Nb2O5 or TiO2 in an oxidizing atmosphere to produce a glass molded article, and the method comprising heat-treating a colored glass containing at least one oxide of WO3 and Nb2O5 in an oxidizing atmosphere to decolor the glass, or heat-treating a glass containing at least one oxide selected from WO3, Nb2O5 or TiO2 in a non-oxidizing atmosphere to color the glass.

Abstract: Provided is an optically uniform and high-quality optical glass that is free from the occurrence of striae when a precision press-molding preform is produced therefrom, and that is a fluorine-containing glass having a refractive index nd(1) wherein the refractive index nd(1) and a refractive index nd(2) are substantially equivalent to each other, said refractive index nd(2) being a refractive index of the fluorine-containing glass after the fluorine-containing glass is re-melted in a nitrogen atmosphere at 900° C. for 1 hour, cooled to its glass transition temperature and then cooled to 25° C. at a temperature decrease rate of 30° C./hour.

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 glass material for mold pressing, comprising a core portion comprised of an optical glass with a degree of abrasion FA of 200 or higher and a covering portion comprised of a second glass covering at least a portion of the surface of said core portion. A method for manufacturing an optical glass element, wherein a glass material that has been preformed to a prescribed shape is heat softened and press molded with a pressing mold and the outer perimeter portion of the molded product obtained is removed by mechanical processing. The above-mentioned glass material for mold pressing is used as the glass material. To provide a means whereby an optical element does not bear scratches on optically functional surfaces through contact during handling after the press molding of press molded glass products despite being comprised of a glass material with a high degree of abrasion, and a means whereby even when scratched, the function of the optical element finally obtained is unaffected.

Abstract: Provided are a process for the production of a precision press-molded article having a high transmittance and a method of treating a glass to color or decolor the glass, the process comprising heat-treating a press-molded article containing at least one selected from WO3, Nb2O5 or TiO2 in an oxidizing atmosphere to produce a glass molded article, and the method comprising heat-treating a colored glass containing at least one oxide of WO3 and Nb2O5 in an oxidizing atmosphere to decolor the glass, or heat-treating a glass containing at least one oxide selected from WO3, Nb2O5 or TiO2 in a non-oxidizing atmosphere to color the glass.

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: Provided is an optically uniform and high-quality optical glass that is free from the occurrence of striae when a precision press-molding preform is produced therefrom, and that is a fluorine-containing glass having a refractive index nd(1) wherein the refractive index nd(1) and a refractive index nd(2) are substantially equivalent to each other, said refractive index nd(2) being a refractive index of the fluorine-containing glass after the fluorine-containing glass is re-melted in a nitrogen atmosphere at 900° C. for 1 hour, cooled to its glass transition temperature and then cooled to 25° C. at a temperature decrease rate of 30° C./hour.

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: Provided is an optically uniform and high-quality optical glass that is free from the occurrence of striae when a precision press-molding preform is produced therefrom, and that is a fluorine-containing glass having a refractive index nd(1) wherein the refractive index nd(1) and a refractive index nd(2) are substantially equivalent to each other, said refractive index nd(2) being a refractive index of the fluorine-containing glass after the fluorine-containing glass is re-melted in a nitrogen atmosphere at 900° C. for 1 hour, cooled to its glass transition temperature and then cooled to 25° C. at a temperature decrease rate of 30° C./hour.

Abstract: A high-refractivity low-dispersion optical glass that can be stably supplied and has excellent glass stability and that has coloring reduced, comprises, by 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, 0 to 15% of ZrO2, 0 to 2% of WO3, 0 to 20% of Yb2O3, 0 to 10% of total of Li2O, Na2O and K2O, 0 to 10% of total of MgO, CaO, SrO and BaO, 0 to 12% of Ta2O5, 0 to 5% of GeO2, 0 to 10% of Bi2O3, and 0 to 10% of Al2O3, wherein the mass ratio of the content of SiO2 to the content of B2O3, (SiO2/B2O3), is from 0.3 to 1.0, and the mass ratio of the total content of Gd2O3 and Y2O3 to the total content of La2O3, Gd2O3 and Y2O3, (Gd2O3+Y2O3)/(La2O3+Gd2O3+Y2O3), is from 0.05 to 0.6, the optical glass having a refractive index nd of 1.89 to 2.0 and an Abbe's number ?d of 32 to 38 and having 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: 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: 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: Preforms for precision press molding made of optical glass, optical elements, and methods of manufacturing the same are provided. The preforms are suited to precision press molding having a broad range of dispersion characteristics, a low glass transition temperature, a low sag point, and good resistance to devitrification while containing no PbO. The optical element is obtained by precision press molding the preform. One example of the preform has a refractive index (nd) of greater than or equal to 1.7 and an Abbé number (?d) of less than or equal to 32. The other example of the preform has an Abbé number (?d) exceeding 32.

Abstract: Disclosed are a process for producing a glass shaped material having high quality and high mass accuracy and a process for producing an optical element, which includes the preparation of a glass shaped material having high quality and high mass accuracy, the heating of said glass shaped material and the precision-press-molding thereof.

Abstract: Preforms for precision press molding made of optical glass, optical elements, and methods of manufacturing the same are provided. The preforms are suited to precision press molding having a broad range of dispersion characteristics, a low glass transition temperature, a low sag point, and good resistance to devitrification while containing no PbO. The optical element is obtained by precision press molding the preform. One example of the preform has a refractive index (nd) of greater than or equal to 1.7 and an Abbé number (vd) of less than or equal to 32. The other example of the preform has an Abbé number (vd) exceeding 32.