Patent ID: 6852010

Claim:
A method of producing a glass substrate for an information recording medium, said method comprising the steps of: preparing a glass substrate having a flatness of 4 μm or less; and polishing a principal surface of said glass substrate by the use of a soft polisher and abrasive grains having an average grain size of 1.0 μm or less, said soft polisher having a hardness such that said glass substrate has a microwaviness average height Ra′ not greater than 0.05 microinch as measured by a contactless laser interference technique for measurement points within a range of 50 μm×50 μm to 4 mm×4 mm on the principal surface, said microwaviness average height Ra′ being given by: Ra ′ = 1 n ⁢ ∑ i = 1 n ⁢ | xi - x _ | , where xi represents a measurement point value of each measurement point {overscore (x)} representing an average value of the measurement point values, n representing the number of the measurement points.