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

摘要

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 CeO₂ abrasive grains having a mean grain diameter of not less than 0.01 mum and a 90% diameter of the volume grain size distribution of not less than 0.02 mum. 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.