Abstract: The present invention relates to an optical glass having a refractive index (nd) of greater than or equal to 1.65 and an Abbé number (? (nu)d) of greater than or equal to 50 for use in precision press molding. The glass exhibits that a ratio ? (alpha)1/? (alpha)2 is less than 17 when temperature denoting maximum value of differential in amount of elongation of glass relative to temperature differential DELTAT (where DELTAT denotes a constant value of 1° C. or less) over a temperature range from glass transition temperature (Tg) to sag temperature (Ts) is denoted as T1, average coefficient of linear expansion over a range from T1-5° C. to T1+5° C. is denoted as alpha1, and average coefficient of linear expansion over a range from the glass transition temperature (Tg)?160° C. to the glass transition temperature (Tg)?140° C. is denoted as alpha2.

Abstract: A substrate for an information recording medium, which is made of a glass or crystallized glass, (1) which has a region that has a spectral light transmittance of 50% or less converted in terms of a thickness of 2 mm in a wavelength range of 2,750 nm to 3,700 nm, (2) which shows a spectral light transmittance of 70% or less converted in terms of a thickness of 2 mm over whole wavelength range of 2,750 nm to 3,700 nm, (3) which contains an infrared absorbent that is a specific metal oxide and is for use in a perpendicular magnetic recording medium, (4) which is to be heated by irradiation with infrared ray and contains more than 200 ppm of water, or (5) which contains an infrared absorbent that is a specific metal oxide and is used as a substrate to support a multi-layered film including an information recording layer to be formed by sputtering after heating by irradiation with infrared ray, an information recording medium comprising a multi-layered film including an information recording layer formed on any o

Abstract: Provided are optical glass exhibiting a refractive index (nd) in a range of 1.75 to 1.87, an Abbé number (?d) in a range of 80 to 45, and excellent low-temperature softening properties even when not incorporating Th2O5 as well as permitting a low production cost; a precision press molding preform and an optical element comprised of such glass; a method of manufacturing the preform; and a method of manufacturing the optical element. The optical glass comprises, in a molar percent, 30 to 45 percent of B2O3, 2 to 15 percent of SiO2, 10 to 20 percent of La2O3, 1 to 10 percent of TiO2, 10 to 30 percent of ZnO, 2 to 15 percent of Li2O, higher than 0 percent and 10 percent or less of WO3, 0 to 15 percent of Nb2O5, and 0 to 10 percent of ZrO2, wherein the total amount of the above-mentioned components is higher than 95 percent, the glass exhibits a refractive index (nd) in a range of 1.75 to 1.87, and an Abbé number (?d) in a range of 80 to 45.

Abstract: In a near-infrared ray absorption glass lot made of a copper-containing near-infrared ray absorption glass material, a near-infrared ray absorption glass lot is constituted of a glass material of which the tolerance of the refractive index (ne) at a wavelength of 546.07 nm is less than ±0.001.

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 process for stably producing a glass shaped material as a base material for a crystallized glass material, which includes casting a molten glass into a through hole of a mold, the through hole having a straight central axis, said central axis being vertical or slanted relative to a horizontal, and shaping the molten glass into a rod-like glass shaped material as a base material for a crystallized glass material.

Abstract: Provided are near-infrared light-absorbing glass in which good color compensating characteristics are maintained even without containing harmful arsenic, permitting the thinning of the glass, and having good weatherability and forming properties; a near-infrared light-absorbing element comprised of such glass; a near-infrared light-absorbing filter employing such glass. Also provided, at low cost, are near-infrared light-absorbing glass permitting good color compensating, a near-infrared light-absorbing element comprised of such glass, and a near-infrared light-absorbing filter comprising such elements. The glass comprises cationic components with a certain composition as well as F? and O2? as anionic components. Alternatively, the glass is near-infrared light-absorbing glass, wherein the glass exhibits properties, based on a thickness of 0.

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: The optical glass has a refractive index of equal to or greater than 1.65 and an Abbé number ranging from 50 to 60. In the optical glass, as molar basis, a ratio of SiO2 content to B2O3 content is greater than 0.5 and equal to or less than 0.90; a total content of SiO2 and B2O3 ranges from 50 to 70 percent; Li2O content ranges from 5 to 20 percent; La2O3 content ranges from 0.5 to 22 percent; a ratio of ZnO content to RO (MgO, CaO, SrO and BaO) is equal to or greater than 0.5; a total content of Gd2O3, Y2O3 and Yb2O3 ranges from 1 to 15 percent; Sb2O3 content ranges from 0 to 1 percent; and no BaO is comprised, or a ratio of the total content of La2O3, Gd2O3, Y2O3 and Yb2O3 to the content of BaO is equal to or greater than 10.

Abstract: An optical glass being free of lead and fluorine, having a low glass transition temperature permitting press-molding with a mold formed of stainless steel and having high climate resistance includes an optical glass comprising, by mol %, 25 to 44% of P2O5, 10 to 40% of a total of Li2O, Na2O and K2O, 5 to 40% of ZnO, 1 to 35% of BaO and at least one components selected from Nb2O5, Bi2O3 and WO3, having a glass transition temperature (Tg) of 370° C. or lower and being free of lead and fluorine and an optical glass which is free of lead and fluorine, has a mass loss ratio of less than 0.25% when immersed in pure water, and has a glass transition temperature (Tg) of 370° C. or lower.

Abstract: A high-refractivity high-dispersion optical glass for producing an optical element, which requires no machining, such as polishing or lapping, of an optical-function surface after precision press molding, containing B2O3, SiO2, La2O3, Gd2O3, ZnO, Li2O, ZrO2 and Ta2O5 as essential components, containing 0 to 1 mol % of Sb2O3 as an optional component, substantially containing none of PbO and Lu2O3, having a glass transition temperature of 630° C. or lower, and (1) having a refractive index nd and an Abbe's number ?d which satisfy all of the following relational expressions, 1.80<nd?1.90, 35??d?50, and nd?2.025?(0.005×?d) or (2) having an nd of greater than 1.85 and a ?d of greater than 35.

Abstract: A low-dispersion optical glass suitable for producing a quality preform from a molten glass and suitable for precision press-molding, which is a fluorophosphate glass containing, as essential cationic components, P5+, Al3+, at least two members selected from Mg2+, Ca2+, Sr2+ and Ba2+ as divalent cationic components (R2+) and Li+ and containing, by cationic %, 10 to 45% of P5+, 5 to 30% of Al3+, 0 to 20% of Mg2+, 0 to 25% of Ca2+, 0 to 30% of Sr2+, 0 to 33% of Ba2+, 1 to 30% of Li+, 0 to 10% of Na+, 0 to 10% of K+, 0 to 5% of Y3+, and 0 to 15% of B3+, the molar ratio of the content of F? to the total content of F? and O2?, F?/(F?+O2?) being 0.25 to 0.85, the optical glass having a refractive index (Nd) of 1.40 to 1.58 and an Abbe's number (?d) of 67 to 90.

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: 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: 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: An optical glass having a refractive index (nd) of 1.57 to 1.67, an Abbe's number (?d) of 55 to 65 and a glass transition temperature (Tg) of 560° C. or lower and having a low-temperature softening property and excellent climate resistance or a haze value of 3% or less, or an optical glass comprising, by mol %, 22 to 40% of B2O3, 12 to 40% of SiO2, 2 to 20% of Li2O, 5 to 15% of CaO, 2 to 14% of ZnO, 0.5 to 4% of La2O3, 0 to 3% of Gd2O3, 0 to 3% of Y2O3, the total content of La2O3, Gd2O3 and Y2O3 being at least 1%, 0 to 5% of Al2O3, 0 to 3% of ZrO2 and 0 to 5% of BaO, the total content of the above components being more than 96%, and having a refractive index (nd) of 1.57 to 1.67 and an Abbe's number (?d) of 55 to 65.

Abstract: A peripheral portion of a molding material 50 on its lower side is supported on a support member 40 provided around a molding surface 21 of a lower mold 20 and an open space is ensured outward of an edge portion of the molding material 50 supported on the support member 40. In this state, the molding material 50 is press-molded between an upper mold 10 and the lower mold 20.

Abstract: Phosphate optical glass having an Abbé number, ?d, of greater than 59. A preform for precision press molding being comprised of the phosphate optical glass. An optical glass being comprised of the phosphate optical glass and manufacturing method of the same. Provided are low-dispersion phosphate optical glass having a low-temperature softening property and good weatherability, suited to precision press molding, and further having good devitrification stability, a preform for precision press molding comprised of the above glass and a method of manufacturing of the same, a glass optical element having the above optical characteristics as well as good weatherability and a method of manufacturing the same.

Abstract: An optical glass having high refractivity and a low sag temperature and having a low-temperature softening property that enables precision press-molding is provided, and the optical glass contains, by mol %, 5 to 50% of B2O3, 3 to 50% of SiO2, 5 to 40% of TiO2, 1 to 40% of ZnO, 5 to 20% of La2O3, 0 to 10% of Gd2O3, 0 to 15% of Nb2O5, 0 to 10% of ZrO2, 0 to 5% of Ta2O5, 0 to 10% of Bi2O3, 0 to 10% of MgO, 0 to 8% of CaO, 0 to 10% of SrO, 0 to 10% of BaO, provided that the total content of MgO, CaO, SrO and BaO is 15% or less, 0 to 20% of Li2O, and 0 to 5% of Na2O, optionally containing Sb2O3 as a refining agent, and having a refractive index (nd) of 1.8 or more and an Abbe's number (vd) of 35 or less.

Abstract: An optical glass having a high refractive index and high dispersion characteristics that is suited to application to precision press molding to precisely mold the shape of final products for objectives not requiring grinding or polishing. An optical glass exhibiting a refractive index in the range of from 1.75 to 2.0, an Abbé number in the range of from 20 to 28.5. Optical parts comprised of this glass; press-molding materials comprised of this glass; methods of manufacturing the same; and methods of manufacturing molded glass products employing these materials.