| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-refractive and low-dispersive glass composition having a refractive index (n<SB>d</SB>)≥1.70 and an Abbes's number (ν<SB>d</SB>)=35-55, having a glass transition temperature (Tg) low enough to exhibit an excellent ability to be press-molded, and having excellent moldability. SOLUTION: The glass composition contains 10-35 wt.% B<SB>2</SB>O<SB>3</SB>, 10-40 wt.% La<SB>2</SB>O<SB>3</SB>, 10-60 wt.% ZnO+ZnF<SB>2</SB>(0-45 wt.% ZnO), and 0.5-9 wt.% Li<SB>2</SB>O+LiF, provided that the total content of fluorine compounds is 9-15 wt.%. To attain a still lower Tg, it is desirable that the composition further contains at least either 0-5 wt.% K<SB>2</SB>O or 0-5 wt.% Na<SB>2</SB>O. To attain an improvement an mechanical strengths, the adjustment of optical constants, and an improvement in chemical tolerance, the composition may further contain one or more components selected from among 0-20 wt.% SiO<SB>2</SB>, 0-20 wt.% Y<SB>2</SB>O<SB>3</SB>, 0-15 wt.% Nb<SB>2</SB>O<SB>5</SB>, 0-20 wt.% Bi<SB>2</SB>O<SB>3</SB>, 0-5 wt.% ZrO<SB>2</SB>, 0-15 wt.% BaO+BaF<SB>2</SB>, 0-10 wt.% CaO+CaF<SB>2</SB>, 0-15 wt.% Ta<SB>2</SB>O<SB>5</SB>, 0-15 wt.% WO<SB>3</SB>, 0-10 wt.% TiO<SB>2</SB>, and 0-10 wt.% Al<SB>2</SB>O<SB>3</SB>. COPYRIGHT: (C)2003,JPO
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