| 摘要 |
<p>Disclosed are a glass substrate (2), an information-recording medium (1), and an information disk device, wherein the glass substrate (2) includes chemically strengthened layers and has been formed from a plate-shaped glass material having a glass composition which comprises, in terms of mass%, 55-75% SiO2, 5-18% Al2O3, 1-10% Li2O, 3-15% Na2O, 0.1-5% K2O, the total amount of Li2O+Na2O+K2O being 10-25%, 0.1-5% MgO, 0.1-5% CaO, and 0-8% ZrO2, the mass ratio of (MgO+CaO) to (Li2O+Na2O+K2O) being 0.10=(MgO+CaO)/(Li2O+Na2O+K2O)=0.80. The glass substrate has warpage formed so that the radially inner area of the first surface (21a) of the glass substrate (2) projects outward. As a result, even when the information recording medium warps when mounted in an information disk device while being held between parts of a clamping member, the peripheral edge of the information recording medium is less apt to hit against the ramp of the information disk device upon reception of impact force.</p> |
