GLASS SUBSTRATE FOR MAGNETIC DISK AND MAGNETIC RECORDING MEDIUM

摘要

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.

主权项

1. 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 byKu=∑i=1nRi4nσ4(2)where n is the number of samples, 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.