| 摘要 |
PROBLEM TO BE SOLVED: To provide a glass ceramic substrate for an information storage medium having good surface characteristics which can enough respond for a ramped loading (contact recording by a magnetic head) for high-density recording, improving in relation between a high Young's modulus and specific gravity to endure against fast rotation, and having thermal expansion characteristics suitable for any driving members, and to provide a production method of the substrate and an information storage medium using this substrate. SOLUTION: The glass ceramic substrate for an information storage medium has 95 to 120 GPa Young's modulus, 2.4 to 2.6 specific gravity, >=37 ratio of Young's modulus (GPs)/specific gravity, and 0 to 10% Al2O3 content (wt.% based on oxides). The glass contains lithium disilicate (Li2O.2SiO2) andα-quartz (α-SiO2) crystal as the main crystal phase, and 65 to 130×10-7/ deg.C coefficient of thermal expansion in -50 to +70 deg.C temperature range. The surface roughness Ra (arithmetic average roughness) of the substrate after polished can be controlled to <=9Å. |
