Patent ID: 8413464

Claim:
A method for producing a glass substrate for a magnetic disk comprising: a glass substrate polishing step; a chemically strengthening step in which a glass substrate is immersed in a chemically strengthening salt solution prepared by dissolving a chemically strengthening salt under heating, and metal ions in the glass substrate are ion-exchanged with metal ions in the chemically strengthening salt; and a cooling step of cooling the glass substrate after the chemically strengthening step, wherein the chemically strengthening step is carried out using the chemically strengthening salt solution comprising KNO 3 and NaNO 3 as a main component of the chemically strengthening salt and an additive component other than the chemically strengthening salt, which is added in an amount of 6% by weight or more in the chemically strengthening salt solution so that the chemically strengthening salt solution does not start to solidify until a temperature decreases to a predetermined temperature at which a surface shape of the glass substrate is not deformed by a force applied to the glass substrate when the chemically strengthening salt having adhered onto the glass substrate after the chemically strengthening step solidifies in the cooling step, whereby, as a result of said steps, a maximum value of micro-waviness on a principal surface of the glass substrate is made to be less than 5 nm when waviness is measured having a frequency with a wavelength of 4 μm to 1 mm and is measured in a rectangular measurement area with sides of 800 μm and 980 μm of the principal surface of the glass substrate.