Patent attributes
Chemical strengthening treatment is performed by first providing a granular chemical strengthening salt so as to prevent spread in atmosphere at the time of introduction of chemical strengthening salt in a treating vessel, introducing the chemical strengthening salt in a treating vessel, melting the chemical strengthening salt into molten chemical strengthening salt and bringing a glass disc into contact with the molten chemical strengthening salt. The granular chemical strengthening salt is, for example, one obtained by forming of a powdery chemical strengthening salt material into grains. A chemically strengthened glass substrate for magnetic disk can be obtained through the process of carrying out chemical strengthening treatment of magnetic disk glass substrates. A magnetic disk can be obtained by forming at least a magnetic layer on the chemically strengthened glass substrate for magnetic disk.
