Substrate for a magnetic recording medium and magnetic recording medium using the substrate

Abstract

A magnetic recording medium has a disk-shaped glass substrate less than or equal to 1 inch (27.4 mm) in diameter, wherein a ratio (t2/d) of a square of the thickness t (mm) to a diameter d (mm) is greater than or equal to 0.007. A deformation of the magnetic recording medium that occurs when it is mounted in the magnetic recording device and clamped can be made small. Therefore, the flying of the magnetic head can be made stable.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a flatness measurement result of a magnetic recording medium according to the present invention that was obtained in a state that it was mounted in a magnetic recording device and clamped;

FIG. 2 shows a flatness measurement result of a magnetic recording medium of Comparative Example in a state that it was mounted in the magnetic recording device and clamped; and

FIG. 3 shows a flatness measurement result of the magnetic recording medium of Comparative Example of FIG. 2 in a state that it was not clamped.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In a disk-shaped glass substrate for a magnetic recording medium whose diameter is less than or equal to 1 inch (27.4 mm), the deformation of the magnetic recording medium that occurs when it is clamped can be reduced by setting the ratio (t²/d) of the square of the thickness t (mm) to the diameter d (mm) greater than or equal to 0.007.

Example in which the flatness of a magnetic recording medium is measured and evaluated in a state that it is mounted in a magnetic recording device and clamped will be described below together with Comparative Example.

The flatness was measured by a phase shift interference type surface shape measuring instrument GPI, a product of Zygo Corporation (now Canon Marketing Japan Inc.).

EXAMPLE

A magnetic recording medium of Example is manufactured by using a glass substrate (for a magnetic recording medium) whose diameter d was 0.85 inches (21.6 mm) and thickness t is 0.508 mm (the ratio t²/d was 0.012) and its flatness is measured. FIG. 1 shows a flatness measurement result of the magnetic recording medium that is obtained in a state that it is mounted in a magnetic recording device and clamped. The flatness is 0.37 μm in the clamped state.

COMPARATIVE EXAMPLE

A magnetic recording medium of Comparative Example is manufactured by using a glass substrate (for a magnetic recording medium) whose diameter d is 0.85 inch (21.6 mm) and thickness t is 0.381 mm (the ratio t²/d is 0.0067) and its flatness is measured. FIG. 2 shows a flatness measurement result of the magnetic recording medium that is obtained in a state that it is mounted in the magnetic recording device and clamped. The flatness is 1.12 μm in the clamped state.

FIG. 3 shows a flatness measurement result of the magnetic recording medium of Comparative Example of FIG. 2 in a state where it is not clamped. The flatness without clamping is 0.15 μm.

As is apparent from the above results, in Example, the deformation of the magnetic recording medium that occurs when it is mounted in a magnetic recording device and clamped can be made much smaller than in Comparative Example, whereby the flying of the magnetic head can be made stable.

The disclosure as disclosed in Japanese Utility Model Application No. 2006-008311 filed on Oct. 12, 2006 is incorporated herein.

While the invention has been explained with reference to the specific embodiments of the invention, the explanation is illustrative, and the invention is limited only by appended claims.

Claims

1. A substrate for a magnetic recording medium which is a disk-shaped glass plate and is less than or equal to 27.4 mm in diameter, wherein a ratio (t2/d) of a square of a thickness t (mm) to a diameter d (mm) is greater than or equal to 0.007.

2. The substrate for a magnetic recording medium according to claim 1, wherein the ratio (t2/d) is greater than or equal to 0.012.

3. A magnetic recording medium comprising: the substrate according to claim 1, and a magnetic recording layer formed on the substrate.