Hoya Corporation

Nippon Sheet Glass Company, Limited

Kensuki Matsuno

Takeo Watanabe

Koji Okuhata

Masamichi Kezuka

Masamichi Kesuka

A substrate for use as a disk substrate in a hard disk drive or the like, an information recording medium such as a magnetic disk, and a starting material glass plate which is a starting material of the substrate for information recording media. The forming conditions of the starting material glass plate are controlled such that the starting material glass plate has a long-wavelength waviness of not more than 6 nm. This starting material glass plate is polished so as to have a long-wavelength waviness of not more than 6 nm using CeOabrasive grains having a mean grain diameter of not less than 0.01 &#x3bc;m and a 90% diameter of the volume grain size distribution of not less than 0.02 &#x3bc;m. The resulting substrate for an information recording medium has an excellent planarity, can be obtained in a short time and with a low polishing amount, and the resulting information recording medium is able to cope with increased data zone recording density.

Substrate for information recording media and manufacturing method thereof, information recording medium, and starting material glass plate

A substrate for use as a disk substrate in a hard disk drive or the like, an information recording medium such as a magnetic disk, and a starting material glass plate which is a starting material of the substrate for information recording media. The forming conditions of the starting material glass plate are controlled such that the starting material glass plate has a long-wavelength waviness of not more than 6 nm. This starting material glass plate is polished so as to have a long-wavelength waviness of not more than 6 nm using CeOabrasive grains having a mean grain diameter of not less than 0.0l &#x3bc;m and a 90% diameter of the volume grain size distribution of not less than 0.02 &#x3bc;m. The resulting substrate for an information recording medium has an excellent planarity, can be obtained in a short time and with a low polishing amount, and the resulting information recording medium is able to cope with increased data zone recording density.

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Osaka, Japan

Kensuki Matsuno