| 摘要 |
This information recording medium glass substrate is used in an information recording medium which comprises a magnetic recording layer formed on the primary surface of a glass substrate and which has a recording density on the magnetic recording surface of 600Gbit/square inch or greater. If the information recording medium glass substrate undergoes first alkali treatment involving immersion for 30 minutes in a pH11 sodium hydroxide solution at 40°C, the average value of Ra change on the surface of the information recording medium glass substrate after said first alkali treatment is 0.50Å or less, and if the information recording medium glass substrate undergoes second alkali treatment involving immersion for 2.5 hours in a pH12 sodium hydroxide solution at 25°C, the average value of Ra change on the surface of the information recording medium glass substrate after said second alkali treatment is 2.00Å or less. |
