Glass substrate for magnetic disk

A glass substrate for a magnetic disk having a disk shape, wherein

• the glass substrate has a diameter D of 85 mm or more and 100 mm or less, and a thickness T of 0.3 mm or more and 0.5 mm or less,
• regarding a Young's modulus E and the thickness T of the glass substrate, a value of E·T3 is 3 to 18 (GPa·mm3),
• a glass of the glass substrate has a ρ·(1−ν)2·Q/E value of less than 25 (g/cm3/GPa), where ρ represents a density (g/cm3) of the glass at room temperature, Q represents a Q-value of the glass under conditions of 3000 Hz and room temperature, E represents a Young's modulus (GPa) of the glass at room temperature, and ν represents a Poisson's ratio of the glass at room temperature, and
• the glass of the glass substrate has a glass transition point of 680° C. or higher.

A glass substrate for a magnetic disk having a disk shape, wherein

• the glass substrate has a diameter D of 85 mm or more and 100 mm or less, and a thickness T of 0.3 mm or more and 0.5 mm or less,
• regarding a Young's modulus E and the thickness T of the glass substrate, a value of E·T3 is 3 to 18 (GPa·mm3),
• a glass of the glass substrate has a Q-value of 1500 or less under conditions of 3000 Hz and room temperature,
• the glass of the glass substrate has a glass transition point of 650° C. or higher, and
• the glass of the glass substrate contains 0 to 4 mol % of B2O3.

A glass substrate for a magnetic disk having a disk shape, wherein

• the glass substrate has a diameter D of 85 mm or more and 100 mm or less, and a thickness T of 0.3 mm or more and 0.5 mm or less,
• regarding a Young's modulus E and the thickness T of the glass substrate, a value of E·T3 is 3 to 18 (GPa·mm3),
• a glass of the glass substrate has a ρ·(1−ν)2·Q/E value of less than 25 (g/cm3/GPa), where ρ represents a density (g/cm3) of the glass at room temperature, Q represents a Q-value of the glass under conditions of 3000 Hz and room temperature, E represents a Young's modulus (GPa) of the glass at room temperature, and ν represents a Poisson's ratio of the glass at room temperature,
• the glass of the glass substrate has a glass transition point of 650° C. or higher, and
• the glass of the glass substrate contains 0 to 4 mol % of B2O3.

A glass substrate for a magnetic disk having a disk shape, wherein

• the glass substrate has a diameter D of 85 mm or more and 100 mm or less, and a thickness T of 0.3 mm or more and 0.5 mm or less,
• regarding a Young's modulus E and the thickness T of the glass substrate, a value of E·T3 is 3 to 18 (GPa·mm3),
• a glass of the glass substrate has a Q-value of 1500 or less under conditions of 3000 Hz and room temperature,
• the glass of the glass substrate has an average linear expansion coefficient in a range of 100° C. to 300° C., and the average linear expansion coefficient is 70×10−7 (1/K) or less, and
• the glass of the glass substrate contains 0 to 4 mol % of B2O3.