Method of polishing a magnetic hard disc substrate

Abstract

Polishing particles are made of artificial diamond produced by a shock method, having density of 3.0-3.35 g/cm 3 and including secondary particles with average particle diameter of 30 nm-500 nm. Such polishing particles are produced by firstly obtaining a product containing artificial diamond by a shock method, then subjecting this product to an acid treatment by using one or more strong acids such as concentrated sulfuric acid, concentrated nitric acid and concentrated hydrochloric acid to thereby remove impurities from and wash the product, thereafter subjecting the product to a classification process to thereby separate artificial diamond of a first kind having secondary particles with particle diameters of 30 nm-500 nm and artificial diamond of a second kind having secondary particles with particle diameters in excess of 500 nm and selecting artificial diamond of a third kind having density of 3.0-3.35 g/cm 3 out of the artificial diamond of the first kind. It is the artificial diamond of the third kind that is to be used as the diamond polishing particles.

1 . A method of polishing a magnetic hard disc substrate, said method comprising the steps of:
 rotating said magnetic hard disc substrate;   supplying slurry to a surface of said magnetic hard disc substrate; and   causing a contact roller to press a polishing tape onto said surface of said magnetic hard disc substrate and to run said polishing tape;   wherein said slurry comprises diamond abrading particles and water or a water-based aqueous solution for dispersing said diamond abrading particles, said diamond abrading particles including primary particles of artificial diamond having density of 3.0-3.35 g/cm 3  and generated by a shock method and secondary particles that are agglomerates of said primary particles and have particle diameters of 30 nm-500 nm, said primary particles having particle diameters of 20 nm or less.