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US 9,685,185 B2Granted
Glass substrate for magnetic disk and magnetic recording medium
AssigneesHoya Corporation, Hoya Glass Disk (Thailand) Ltd.
InventorKenichi Nishimori
Life of this patent
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Abstract
With regard to a glass substrate 1 according to the present invention, a value of an amendment concentricity AC that has taken into consideration Sk and/or Ku calculated from a shape profile over the whole circumference of an inside hole, or the skewness is within a predetermined range. The glass substrate for a magnetic recording medium can stably read servo information including track information stored on a magnetic disk when the glass substrate is used for an HDD.
Claims6
A glass substrate for a magnetic disk with an inside hole formed therein, wherein:
- a value (Ku−3) obtained by subtracting 3 from Ku calculated from a shape profile over a whole circumference of the inside hole is in a range of 1.6 to −1.6, and
- Ku is given by
- Ku
- =
- ∑
- i
- =
- 1
- n
-
-
- R
- i
- 4
- n
-
-
- σ
- 4
- (
- 2
- )
- where n is the number of samples, and n=3600, Ri is an ith difference between the shape profile and a least-square-approximated circle of the shape profile on a line drawn to the least-square-approximated circle of the shape profile from a center of a circle calculated by a least-square approximation of the shape profile of the inside hole, and σ is a standard deviation.
20 more elements
Dependencies are inferred from the claim text.