In the colloidal silica slurry which is used in production manner of the glass substrate for information record media which includes with the colloidal silica grinding

摘要

PROBLEM TO BE SOLVED: To provide an information recording medium glass substrate having small Ra in a method for manufacturing the information recording medium glass substrate by passing a glass disk made of an alkaline aluminosilicate glass through a polishing step using a slurry containing colloidal silica abrasives.;SOLUTION: A colloidal silica slurry is used in a method for manufacturing an information recording medium glass substrate, including a wrapping step of wrapping a main surface of a glass disk, a cerium oxide polishing step of executing polishing by using a slurry containing cerium oxide abrasives, and a colloidal silica polishing step of executing polishing by using a slurry containing colloidal silica abrasives. In the colloidal silica slurry, for colloidal silica abrasives, a BET particle size obtained by BET specific surface measurement is equal to or less than 40 nm, and a smoothness index represented by BET particle size (nm)/circularity is equal to or less than 50 nm. Also provided are an information recording medium glass substrate manufactured by using the colloidal silica slurry, and a magnetic recording medium having a magnetic recording layer formed on a main surface of the information recording medium glass substrate.;COPYRIGHT: (C)2012,JPO&INPIT