| 摘要 |
PROBLEM TO BE SOLVED: To provide a glass substrate which has high mechanical strengths without being tempered, a coefficient of thermal expansion close to that of a motor member, high fracture toughness, and a predefined surface hardness, from which little alkali component dissolves, and which is excellent in processability and productivity; and to obtain a glass composition used for the same. SOLUTION: The glass composition contains glass components of 45-75 wt.% (hereinafter expressed as %) SiO<SB>2</SB>, 1-20% Al<SB>2</SB>O<SB>3</SB>, 0-8% B<SB>2</SB>O<SB>3</SB>, 60-90% of SiO<SB>2</SB>+ Al<SB>2</SB>O<SB>3</SB>+ B<SB>2</SB>O<SB>3</SB>, 0-20%, in total, of R<SB>2</SB>O (R = Li, Na and K), and 0-15% of TiO<SB>2</SB>+ ZrO<SB>2</SB>+ Ln<SB>x</SB>O<SB>y</SB>(wherein, Ln<SB>x</SB>O<SB>y</SB>means at least one compound selected from the group of lanthanoid metal oxides, Y<SB>2</SB>O<SB>3</SB>, Nb<SB>2</SB>O<SB>5</SB>, and Ta<SB>2</SB>O<SB>5</SB>). COPYRIGHT: (C)2005,JPO&NCIPI
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