| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical glass having excellent devitrification resistance, high refractive index, and high dispersibility; a glass material for press molding comprising the optical glass; and an optical element. SOLUTION: The optical glass contains SiO<SB>2</SB>of≥18 and <30, BaO of≥12 and <23, TiO<SB>2</SB>of 22-37, Nb<SB>2</SB>O<SB>5</SB>of≥7 and <16, Na<SB>2</SB>O of 5-20, K<SB>2</SB>O of 0-6, CaO of 0-5, SrO of 0-5, ZrO<SB>2</SB>of 0-4, Ta<SB>2</SB>O<SB>5</SB>of 0-3, Sb<SB>2</SB>O<SB>5</SB>of 0-1, and P<SB>2</SB>O<SB>5</SB>of≥0 and <0.5, in terms of wt.%, and does not substantially contain PbO, As<SB>2</SB>O<SB>3</SB>and F. Alternatively, the optical glass contains SiO<SB>2</SB>, BaO, and TiO<SB>2</SB>as indispensable ingredients, and has a refractive index (nd) of≥1.80, an Abbe's number (νd) of≤30, and such a devitrification resistance that the numerical density of crystallized particles is≤12pieces/mm<SP>3</SP>deposited after heated at a temperature by 20°C higher than the glass transition temperature for 5 hours and then kept at 900°C for 5 minutes. The glass material for press molding and the optical device are composed of the optical glass. COPYRIGHT: (C)2004,JPO
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