Sheet glass flattening method, method of manufacturing glass substrate for an information recording disk using flattened glass, method of manufacturing a magnetic recording disk using glass substrate, and magnetic recording medium

Abstract

A glass substrate manufacturing method advantageously applicable to magnetic recording disk glass substrates, LCD glass substrates, photomask glass substrates, or optical memory glass substrates. This method includes the steps of forming a film of a solution on at least a principal surface of a sheet glass formed using a down-drawing method, the solution containing a water soluble inorganic material and a surface-active agent; sandwiching both sides of a single sheet glass on which the film is formed or of a laminated structure of plural sheet glasses with a densified sheet with a high flatness to pressure the single glass or laminated structure; and heating and annealing the single sheet glass or laminated structure to flatten the same. The end side of the flatten glass substrate is treated with a treating solution containing a hydrofluosilicic acid. The glass substrate is formed by chemically strengthen a glass substrate by immersing the glass substrate in a chemical reinforcement solution heated and then ion exchanging ions on the surface-layer of the glass substrate with ions in the chemical reinforcement solution; pulling up the substrate from the chemical reinforcement solution and then annealing it to a temperature higher than the crystallization temperature of a molten salt; annealing the glass substrate at a rate at which the crystallization of the molten salt is deposited on the surface of the glass substrate; and then cleaning the surface of the glass substrate. Moreover, the glass substrate is formed by chemically strengthen a glass substrate by immersing the glass substrate in a chemical reinforcement solution heated and then ion exchanging ions on the surface layer of the glass substrate with ions in the chemical reinforcement solution; and pulling up the substrate from the chemical reinforcement solution and then cleaning the surface of the glass substrate with a cleaning agent containing acid.

Dependencies are inferred from the claim text.