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AssigneeHoya Corporation
InventorsKouji Takahashi, Takemi Miyamoto, Hiroshi Tomiyasu, Genshichi Hata, Tomotaka Yokoyama
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A substrate for an information recording medium 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 measurement region of 50 μm□-4 mm□ on a surface of the substrate. The microwaviness average height Ra′ is given by: 1 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 said measurement points. Alternatively, the substrate has a waviness period between 300 μm and 5 mm and a waviness average height Wa of 1.0 nm or less as measured by the contactless laser interference technique for measurement points in a measurement region surrounded by two concentric circles which is spaced from a center of a surface of the substrate by a predetermined distance. The waviness average height Wa is given by: 2 Wa = 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 said measurement points.
A substrate for an information recording medium, said substrate having a microwaviness average height Ra′ not greater than 0.05 microinch as measured by a contactless laser interference technique for measurement points within a measurement region of 50 μm□-4 mm□ on a surface of said substrate, said microwaviness average height Ra′ being given by:
A substrate for an information recording medium, said substrate having a microwaviness period between 2 μm and 4 mm and a microwaviness average height Ra′ not greater than 0.05 microinch as measured by a contactless laser interference technique for measurement points in a measurement region on a surface of said substrate, said microwaviness average height Ra′ being given by:
A substrate for an information recording medium, said substrate having a disk-like shape, said substrate having a waviness period between 300 μm and 5 mm and a waviness average height Wa of 1.0 nm or less as measured by a contactless laser interference technique for measurement points in a measurement region surrounded by two concentric circles which is spaced from a center of a surface of said disk-shaped substrate by a predetermined distance, said waviness average height Wa being given by:
A method of producing a glass substrate for an information recording medium, said method comprising the steps of:
A method as claimed in any one of claims 9 through 13, wherein:
A substrate for a magnetic recording medium, said substrate having a predetermined microwaviness average height Ra′ determined by:
A method of controlling a principal surface of a substrate for a magnetic recording medium, said method comprising the steps of:
A substrate for a magnetic recording medium, said substrate having a predetermined microwaviness maximum height wa determined by:
A method of controlling the surface of a substrate for a magnetic recording medium, comprising the steps of:
Dependencies are inferred from the claim text.