Glass-ceramic substrate for an information storage medium

Abstract

A glass-ceramic substrate for an information storage medium includes, as a predominant crystal phase, lithium disilicate (Li2O·2SiO2) or a combination of lithium disilicate and at least one crystal phase selected from the group consisting of α-quartz (α-SiO2), α-quartz solid solution (α-SiO2 solid solution), α-cristobalite (α-SiO2) and α-cristobalite solid solution (α-SiO2 solid solution). This substrate has Young's modulus (GPa)/specific gravity of 37 or over, surface roughness Ra (arithmetic mean roughness) of 5.0 Å or below, a coefficient of thermal expansion within a temperature range from −50° C. to +70° C. which ranges from +65×10−7/° C. to +130×10−7/° C. and bending strength of 400 MPa or over.

Dependencies are inferred from the claim text.