Abstract: A high-refractivity low-dispersion optical glass that gives press-molding preforms excellent in high-temperature shapability and suitable for precision press-molding, including an optical glass comprising B2O3, La2O3, Gd2O3 and ZnO as essential components, substantially containing none of lead and fluorine, having a refractive index (nd) of 1.72 to 1.83, an Abbe's number (?d) of 45 to 55 and a glass transition temperature (Tg) of 630° C. or lower and having a viscosity of at least 0.6 Pa·s at its liquidus temperature, and an optical glass comprising, by mol %, 45 to 65% of B2O3, 5 to 22% of La2O3, 1 to 20% of Gd2O3, provided that the total content of La2O3 and Gd2O3 is 14 to 30%, 5 to 30% of ZnO, 0 to 10% of SiO2, 0 to 6.5% of ZrO2 and 0 to 1% of Sb2O3, substantially containing none of lead and fluorine, and having a refractive index (nd) of 1.72 to 1.83 and an Abbe's number (?d) of 45 to 55.

Abstract: A high-refractivity low-dispersion optical glass that gives press-molding preforms excellent in high-temperature shapability and suitable for precision press-molding, including an optical glass comprising B2O3, La2O3, Gd2O3 and ZnO as essential components, substantially containing none of lead and fluorine, having a refractive index (nd) of 1.72 to 1.83, an Abbe's number (?d) of 45 to 55 and a glass transition temperature (Tg) of 630° C. or lower and having a viscosity of at least 0.6 Pa·s at its liquidus temperature, and an optical glass comprising, by mol %, 45 to 65% of B2O3, 5 to 22% of La2O3, 1 to 20% of Gd2O3, provided that the total content of La2O3 and Gd2O3 is 14 to 30%, 5 to 30% of ZnO, 0 to 10% of SiO2, 0 to 6.5% of ZrO2 and 0 to 1% of Sb2O3, substantially containing none of lead and fluorine, and having a refractive index (nd) of 1.72 to 1.83 and an Abbe's number (?d) of 45 to 55.

Abstract: Disclosed is a method of manufacturing ultraprecise lenses, including aspherical lenses, not requiring grinding or polishing after press molding. The method comprises heating a glass material to a temperature corresponding to a glass viscosity of from 105 to 109 dPaS so that the glass material is softened, and press molding the glass material with the pressing molds which are heated to a temperature corresponding to a glass viscosity of from 108 to 1012 dPaS. Provided that the glass material is not heated to a temperature as high as that corresponding to a glass viscosity of 105 dPaS when the pressing mold is heated to a temperature corresponding to a glass viscosity of 108 and that the glass material is not heated to a temperature as low as that corresponding to a glass viscosity of 109 dPaS when the pressing mold is heated to a temperature corresponding to a glass viscosity of 1012 dPaS.

Abstract: A high-refractivity low-dispersion optical glass that gives press-molding preforms excellent in high-temperature shapability and suitable for precision press-molding, including an optical glass comprising B2O3, La2O3, Gd2O3 and ZnO as essential components, substantially containing none of lead and fluorine, having a refractive index (nd) of 1.72 to 1.83, an Abbe's number (?d) of 45 to 55 and a glass transition temperature (Tg) of 630° C. or lower and having a viscosity of at least 0.6 Pa·s at its liquidus temperature, and an optical glass comprising, by mol %, 45 to 65% of B2O3, 5 to 22% of La2O3, 1 to 20% of Gd2O3, provided that the total content of La2O3 and Gd2O3 is 14 to 30%, 5 to 30% of ZnO, 0 to 10% of SiO2, 0 to 6.5% of ZrO2 and 0 to 1% of Sb2O3, substantially containing none of lead and fluorine, and having a refractive index (nd) of 1.72 to 1.83 and an Abbe's number (?d) of 45 to 55.

Abstract: A high-refractivity low-dispersion optical glass that gives press-molding preforms excellent in high-temperature shapability and suitable for precision press-molding, including an optical glass comprising B2O3, La2O3, Gd2O3 and ZnO as essential components, substantially containing none of lead and fluorine, having a refractive index (nd) of 1.72 to 1.83, an Abbe's number (?d) of 45 to 55 and a glass transition temperature (Tg) of 630° C. or lower and having a viscosity of at least 0.6 Pa·s at its liquidus temperature, and an optical glass comprising, by mol %, 45 to 65% of B2O3, 5 to 22% of La2O3, 1 to 20% of Gd2O3, provided that the total content of La2O3 and Gd2O3 is 14 to 30%, 5 to 30% of ZnO, 0 to 10% of SiO2, 0 to 6.5% of ZrO2 and 0 to 1% of Sb2O3, substantially containing none of lead and fluorine, and having a refractive index (nd) of 1.72 to 1.83 and an Abbe's number (?d) of 45 to 55.

Abstract: Disclosed is a method of manufacturing ultraprecise lenses, including aspherical lenses, not requiring grinding or polishing after press molding. The method comprises heating a glass material to a temperature corresponding to a glass viscosity of from 105 to 109 dPaS so that the glass material is softened, and press molding the glass material with the pressing molds which are heated to a temperature corresponding to a glass viscosity of from 108 to 1012 dPaS. Provided that the glass material is not heated to a temperature as high as that corresponding to a glass viscosity of 105 dPaS when the pressing mold is heated to a temperature corresponding to a glass viscosity of 108 and that the glass material is not heated to a temperature as low as that corresponding to a glass viscosity of 109 dPaS when the pressing mold is heated to a temperature corresponding to a glass viscosity of 1012 dPaS.

Abstract: A high-refractivity low-dispersion optical glass that gives press-molding preforms excellent in high-temperature shapability and suitable for precision press-molding, including an optical glass comprising B2O3, La2O3, Gd2O3 and ZnO as essential components, substantially containing none of lead and fluorine, having a refractive index (nd) of 1.72 to 1.83, an Abbe's number (vd) of 45 to 55 and a glass transition temperature (Tg) of 630° C. or lower and having a viscosity of at least 0.6 Pa•s at its liquidus temperature, and an optical glass comprising, by mol %, 45 to 65% of B2O3, 5 to 22% of La2O3, 1 to 20% of Gd2O3, provided that the total content of La2O3 and Gd2O3 is 14 to 30%, 5 to 30% of ZnO, 0 to 10% of SiO2, 0 to 6.5% of ZrO2 and 0 to 1% of Sb2O3, substantially containing none of lead and fluorine, and having a refractive index (nd) of 1.72 to 1.83 and an Abbe's number (vd) of 45 to 55.