Abstract: This optical glass contains, as represented by mol %, 18 to 38% P2O5, 0 to 15% B2O3, 23 to 40% P2O5+B2O3, 4 to 28% Nb2O5, 0 to 20% TiO2, 10 to 30% Nb2O5+TiO2, 15 to 35% Li2O+Na2O+K2O, and 21 to 38% ZnO, but does not contain BaO, WO3, Bi2O3 or SiO2, and the ratio of the mol % of ZnO to the total mol % of Li2O+Na2O+K2O (i.e., ZnO/(Li2O+Na2O+K2O)) is 0.8 to 2.0.

Abstract: The present invention relates to the glass substrate for an information recording medium comprising the following glass components: SiO2: 52 to 67; Al2O3: 8 to 20; B2O3: 0 to 6, with these three oxides FMO: 70 to 85; Li2O: 0.5 to 4; Na2O: 1 to 8; K2O: 0 to 5; and with these three oxides R2O: 5 to 15; MgO: 2 to 9; CaO: 0.1 to 5; BaO: 0 to 3; SrO: 0 to 3; ZnO: 0 to 5; and with these five oxides: 5 to 15; Y2O3: 0 to 4; La2O3: 0 to 4; Gd2O3: 0 to 4; CeO2: 0 to 4; TiO2: 1 to 7; HfO2: 0 to 2; ZrO2: 0 to 5; Nb2O5: 0.2 to 5; and Ta2O5: 0 to 5, and satisfies Li2O/R2O: 0.05 to 0.35; Li2O/FMO: 0.005 to 0.035; Li2O/(MgO+ZnO): less than 2 and Nb2O5/SiO2: 0.01 to 0.075.

Abstract: This optical glass contains, as represented by mol %, 18 to 38% P2O5, 0 to 15% B2O3, 23 to 40% P2O5+B2O3, 4 to 28% Nb2O5, 0 to 20% TiO2, 10 to 30% Nb2O5+TiO2, 15 to 35% Li2O+Na2O+K2O, and 21 to 38% ZnO, but does not contain BaO, WO3, Bi2O3 or SiO2, and the ratio of the mol % of ZnO to the total mol % of Li2O+Na2O+K2O (i.e., ZnO/(Li2O+Na2O+K2O)) is 0.8 to 2.0.

Abstract: The present invention relates to the glass substrate for an information recording medium comprising the following glass components: SiO2: 52 to 67; Al2O3: 8 to 20; B2O3: 0 to 6, with these three oxides FMO: 70 to 85; Li2O: 0.5 to 4; Na2O: 1 to 8; K2O: 0 to 5; and with these three oxides R2O: 5 to 15; MgO: 2 to 9; CaO: 0.1 to 5; BaO: 0 to 3; SrO: 0 to 3; ZnO: 0 to 5; and with these five oxides: 5 to 15; Y2O3: 0 to 4; La2O3: 0 to 4; Gd2O3: 0 to 4; CeO2: 0 to 4; TiO2: 1 to 7; HfO2: 0 to 2; ZrO2: 0 to 5; Nb2O5: 0.2 to 5; and Ta2O5: 0 to 5, and satisfies Li2O/R2O: 0.05 to 0.35; Li2O/FMO: 0.005 to 0.035; Li2O/(MgO+ZnO): less than 2 and Nb2O5/SiO2: 0.01 to 0.075.

Abstract: An optical glass has a composition including: 40 to 65 mass % of P2O5, and 0 to less than 5 mass % of Li2O+Na2O+K2O. In the optical glass, (MgO+CaO)/(Li2O+Na2O+K2O) which is a ratio of the total content expressed in mass % of MgO and CaO to the total content expressed in mass % of Li2O, Na2O, and K2O, is in a range from 6 to 38.

Abstract: The disclosed optical glass contains, by weight, 20-32% SiO2, 6-10% Li2O (exclusive of 6%), 3-18% Na2O, 3-20% K2O, 8-30% TiO2, 10-55% Nb2O5, 0.3-3% B2O3, 0-3% Gd2O3, 0-3% Y2O3, 0-3% La2O3 (with Gd2O3+Y2O3+La2O3?0.5%), 0-2% Bi2O3, 0-2% WO3, 0-2% SnO2, and has a refractive index (nd) of 1.78-1.85, and an Abbe number (vd) of 23-35.

Abstract: An optical glass includes P2O5, B2O3, Li2O, Na2O, K2O, CaO, TiO2, Bi2O3, Nb2O5 and WO3 each of which is in an amount in a predetermined range.

Abstract: An optical glass includes, based on a total weight of the optical glass: 15 to 40 weight percent of P2O5; 0 to 10 weight percent of Li2O; 0 to 20 weight percent of Na2O; 0 to 20 weight percent of K2O; more than 2 weight percent and not more than 15 weight percent of TiO2; 0 to 15 weight percent of CaO; 0 to 32 weight percent of BaO; 0 to 20 weight percent of SrO; 0 to 15 weight percent of ZnO, not less than 0 weight percent and less than 3 weight percent of Bi2O3; 0 to 50 weight percent of Nb2O5; not less than 0 weight percent and less than 20 weight percent of WO3; and 0 to 1 weight percent of Sb2O3. A total weight of Li2O, Na2O and K2O is in a predetermined range of weight percents and the optical glass does not comprise B2O3.

Abstract: An optical glass has a composition including: 40 to 65 mass % of P2O5, and 0 to less than 5 mass % of Li2O+Na2O+K2O. In the optical glass, (MgO+CaO)/(Li2O+Na2O+K2O) which is a ratio of the total content expressed in mass % of MgO and CaO to the total content expressed in mass % of Li2O, Na2O, and K2O, is in a range from 6 to 38.

Abstract: An optical glass contains as glass ingredients, by weight: 0-8% SiO2; 34.5-46% B2O3; 2.6-6% Li2O; 21-38% ZnO; 0-40% La2O3; 0-35% Gd2O3; and 0-15% Y2O3, with the total content of La2O3+Gd2O3+Y2O3 accounting for 10-40%. The optical glass also has a predetermined index of refraction and a predetermined dispersion.

Abstract: An optical glass contains as glass ingredients, by weight: 10-35% SiO2; 8-30% B2O3; 4-9% Li2O; 26-40% ZnO; 1-25% La2O3; and 6-22% Nb2O5.

Abstract: An optical glass includes, based on a total weight of the optical glass: 15 to 40 weight percent of P2O5; 0 to 10 weight percent of Li2O; 0 to 20 weight percent of Na2O; 0 to 20 weight percent of K2O; more than 2 weight percent and not more than 15 weight percent of TiO2; 0 to 15 weight percent of CaO; 0 to 32 weight percent of BaO; 0 to 20 weight percent of SrO; 0 to 15 weight percent of ZnO, not less than 0 weight percent and less than 3 weight percent of Bi2O3; 0 to 50 weight percent of Nb2O5; not less than 0 weight percent and less than 20 weight percent of WO3; and 0 to 1 weight percent of Sb2O3. A total weight of Li2O, Na2O and K2O is in a predetermined range of weight percents and the optical glass does not comprise B2O3.

Abstract: An optical glass includes P2O5, B2O3, Li2O, Na2O, K2O, CaO, TiO2, Bi2O3, Nb2O5 and WO3 each of which is in an amount in a predetermined range.

Abstract: An optical glass contains as glass ingredients, by weight: 10-35% SiO2; 8-30% B2O3; 4-9% Li2O; 26-40% ZnO; 1-25% La2O3; and 6-22% Nb2O5.

Abstract: An optical glass contains as glass ingredients, by weight: 0-8% SiO2; 34.5-46% B2O3; 2.6-6% Li2O; 21-38% ZnO; 0-40% La2O3; 0-35% Gd2O3; and 0-15% Y2O3, with the total content of La2O3+Gd2O3+Y2O3 accounting for 10-40%. The optical glass also has a predetermined index of refraction and a predetermined dispersion.

Abstract: Disclosed herein is a glass whose viscosity index (A) defined as a value obtained by dividing the viscosity of the glass at the liquidus temperature thereof by the liquidus temperature of the glass is in the range of 0.0004 to 1.5. Such a glass is melted in a melting furnace equipped with a nozzle, and the molten glass is dropped from the nozzle intermittently and regularly to obtain glass droplets. The glass droplet naturally dropped from the nozzle is received by a receiving mold to form a glass gob. The glass gob can be used as a preform for reheating molding. Further, it is possible to produce an optical glass element having no plane defect such as a shear mark by press-molding a hot glass gob with an upper mold just after the glass gob is received by the receiving mold.