| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a glass substrate for an information recording medium having excellent specific modulus of elasticity without tempering treatment, eluting little alkali, having high heat resistance, having high fracture toughness and having specified surface hardness and to provide a glass composition using for it. <P>SOLUTION: The glass composition contains respective glass components comprising, by weight, 40-70% SiO<SB>2</SB>, 1-20% Al<SB>2</SB>O<SB>3</SB>, 0-10% B<SB>2</SB>O<SB>3</SB>, 60-90% (SiO<SB>2</SB>+Al<SB>2</SB>O<SB>3</SB>+B<SB>2</SB>O<SB>3</SB>), 3.0-15% total amount of R<SB>2</SB>O, 2.0-15% total amount of R'O (wherein, R' is Mg or Zn) and 1.0-20% MOx(TiO<SB>2</SB>+ZrO<SB>2</SB>+Ln<SB>x</SB>O<SB>y</SB>) and satisfies the equation denoted as 0.070<(total amount of R'O)/(SiO<SB>2</SB>+Al<SB>2</SB>O<SB>3</SB>+B<SB>2</SB>O<SB>3</SB>)<0.200. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
