| 摘要 |
Optical glass having a refractive index (n<SUB>d</SUB>) of 1.75 or greater, and an Abbe number ( ?<SUB>d</SUB>) falling within the range of 15 to 40, which is suitable for molding by precision mold press is provided. The optical glass is characterized by including B<SUB>2</SUB>O<SUB>3</SUB> + SiO<SUB>2</SUB> in an amount of 10 to 70%, Bi<SUB>2</SUB>O<SUB>3</SUB> in an amount of 5% or more and less than 25%, RO + Rn<SUB>2</SUB>O in an amount of 5 to 60% (wherein R represents one or more selected from a group consisting of Zn, Ba, Sr, Ca, and Mg; and Rn represents one or more selected from a group consisting of Li, Na, K, and Cs), with each component in the range expressed in oxide-based mole, and is characterized in that transparency in the visible region is high, and that the transition point (Tg) is 520<SUP>o</SUP>C or lower. The optical glass is characterized by having a spectral transmittance of 70% or greater at a wavelength of 550 nm, for a thickness of 10 mm. |
