JPH0562171A - Magnetic disk - Google Patents

Abstract

PURPOSE:To increase the recording capacity of a magnetic disk by method wherein a magnetic head is levitated and scanned stably at the outer circumferential part of the magnetic disk. CONSTITUTION:In a magnetic disk, a magnetic layer 4 is formed on one main face of a substrate 1 whose outer circumferential face has been chamfered. In the magnetic disk, the chamfer dimension of said substrate 1 is regulated to be within 0.13mm, and a region where the face of the disk is made flat is expanded to the outer circumferential side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk suitable for use as a hard disk.

[0002]

2. Description of the Related Art For example, a hard disk used as a storage medium of a hard disk device such as a computer is
In general, a magnetic layer is formed on a disk substrate on the surface of which a non-magnetic undercoat film made of a Ni-P plating film or the like is formed, and a protective film made of a carbon film or the like and a lubricant are sequentially laminated on the magnetic layer. Have a configuration.

When performing recording / reproducing with respect to this hard disk, a so-called floating type magnetic head is used, which is levitated and runs with a minute gap (so-called flying height) with respect to the disk surface at the time of recording / reproducing.

In a magnetic disk on which recording / reproduction is performed by such a floating magnetic head, the magnetic gap portion of the magnetic head is brought as close as possible to the disk surface at the time of recording / reproduction in order to cope with recent high density recording. It is necessary to stabilize the levitation state as well as lower the glide height.

[0005]

By the way, in the conventional magnetic disk, the outer peripheral surface of the disk substrate to be used is usually slanted with respect to the surface of the disk substrate because of the handling convenience when using the magnetic disk. Chamfering is required to prevent damage to the magnetic disk that may occur when it comes into contact with the device. That is, as shown in FIG. 4, the disk substrate 1 of the magnetic disk
1 is chamfered with a predetermined chamfering dimension α (usually 0.18 mm ± 0.05 mm or more) from its outermost periphery 11a.

However, as described above, the disk substrate 11
When chamfering is performed on the disk substrate 11, the outer peripheral surface of the disk substrate 11 is notched obliquely with respect to the disk surface, and further the inner peripheral side is further cut from the chamfered portion A by polishing after the chamfering process. A slight surface sag (about 0.1 to 0.2 μm in the thickness direction of the disk substrate 11) also occurs in the portion B.

On the outer peripheral side of the disk substrate 1 whose surface has been shaved by chamfering in this way, the magnetic head cannot follow the shape of the disk surface during recording and reproduction, and the flying height of the magnetic head is kept constant. Therefore, the output characteristics at the time of recording / reproducing will be significantly deteriorated.

Therefore, the chamfered portion A of the disk substrate 1 (more accurately, the chamfered portion is also included).
Cannot be used as a writable area of an information signal, which is extremely disadvantageous in increasing the recording capacity accompanying the increase in recording density. Particularly in a small-diameter disc having a diameter of 3.5 inches or less, it is difficult to secure a sufficient recording capacity. Therefore, if the writable area of the information signal is restricted as described above, it is difficult to secure a sufficient recording capacity. Becomes

Therefore, the present invention has been proposed in view of the above-mentioned conventional circumstances, and a magnetic head capable of stably flying the magnetic head even on the outer peripheral side of the magnetic disk to secure a sufficient recording capacity. The purpose is to provide a disc.

[0010]

DISCLOSURE OF THE INVENTION The inventors of the present invention have conducted extensive studies to achieve the above-mentioned object. As a result, the chamfered area of the outer peripheral surface of the disk substrate is regulated so that the outer peripheral portion of the magnetic disk is protected. Further, the present invention has been found out that the magnetic head can be stably levitated during recording and reproduction, and the region where a sufficient output can be obtained can be remarkably expanded.

That is, the magnetic disk of the present invention is characterized in that a recording layer is formed on a disk substrate having a chamfered dimension of 0.13 mm or less.

[0012]

By limiting the size (chamfering dimension) of the chamfered portion of the outer peripheral surface of the disk substrate to 0.13 mm or less, when the magnetic head is floated over the disk surface during recording and reproduction, The flying height of the magnetic head can be kept constant even at a position extremely close to the outermost circumference of the disk, and good output can be obtained.

[0013]

EXAMPLES Preferred examples of the present invention will be described below based on experimental results. As shown in FIG. 1, the magnetic disk of the present embodiment has a magnetic layer 4 formed on a main surface 1a of a substrate 1 having a Ni-P plating film 2 formed on the surface thereof, with an underlayer 3 interposed therebetween. ..

The substrate 1 is required to have excellent responsiveness and a large storage capacity, and a hard material such as aluminum can be used as a material having such characteristics. ..

In this substrate 1, as shown in FIG. 2, its outer peripheral surface 1a is chamfered. On the outer peripheral side of the substrate 1 thus chamfered, the magnetic head cannot follow the shape of the disk surface during recording and reproduction, and the magnetic head cannot be stably run. Become.

Therefore, in this embodiment, the size of the portion A to be chamfered (chamfering dimension α) is set to within 0.13 mm. As described above, by suppressing the chamfer dimension α to be small, the magnetic head can be stably run even at a position extremely close to the outer peripheral surface 1a of the substrate 1. Therefore,
Since the non-recordable area is reduced, the recording capacity can be increased. The smaller the chamfer dimension α, the larger the recording capacity, but is limited to the above range due to the current chamfering process.

On the surface of the substrate 1, non-magnetic Ni-P is used.
The plating film 2 is formed. This Ni-P plated film 2 is
It is provided for the purpose of increasing the surface hardness of the substrate 1 and ensuring the adhesion to the magnetic layer 4.

The surface of the Ni-P plated film 2 is subjected to a texture treatment to give a texture mark having a predetermined shape. The surface roughness of the textured Ni-P plated film 2 is preferably selected as appropriate.

A base layer 3 made of a Cr film or the like is formed on the Ni-P plated film 2. The underlayer 3 is provided to control the crystallinity and the like when the magnetic layer 4 is formed by vapor deposition, sputtering or the like, and has the effect of improving the magnetic characteristics (for example, coercive force).

A magnetic layer 4 is formed on the underlayer 3. As the magnetic layer 4, a sputtered film, electrolytic plating,
Any conventionally known magnetic material can be used, such as a ferromagnetic metal thin film formed by electroless plating or ion plating, a magnetic film obtained by applying a magnetic paint mainly composed of magnetic powder and a binder. Is.

A protective film made of a carbon film or the like may be formed on the magnetic layer 4 for the purpose of improving weather resistance and durability.

Therefore, 3.5 having the above-mentioned structure
For a hard disk of inch (diameter r = 47.5 mm from the center to the outer edge), the chamfering dimension of the substrate is 0.1
The output characteristics at the time of recording / reproduction when changed in the range of 0.3 mm were examined.

FIG. 3 is a diagram showing a change in the number of head hits near the outer peripheral edge of the magnetic disk when the flying height of the magnetic head is set to 4 μm. In the figure,
The horizontal axis represents the position of the flying magnetic head as a diameter from the center of the magnetic disk, and the vertical axis represents the number of head hits measured at that position.

As shown in FIG. 3, the increase in the number of head hits tends to increase sharply as the position of the magnetic head approaches the outer peripheral surface. The increase in the number of hits occurred at a position 45 mm from the center of the magnetic disk, whereas when the chamfered dimension was 0.13 mm or less, the position was 46 mm.
The magnetic head was extended to mm or more, and the magnetic head could stably fly up to this position. Therefore, by setting the chamfering dimension within 0.13 mm, it is possible to enlarge the area in which the upper signal can be written by 1 mm or more as compared with the conventional magnetic disk, and it is possible to increase the recording capacity. I understood.

[0025]

As is apparent from the above description, in the magnetic disk of the present invention, the chamfered dimension of the disk substrate used is small, so that when the magnetic head is levitated on this magnetic disk, The magnetic head can be stably levitated and used even on the outer circumference side of the magnetic disk, and a large recording / reproducing output can be secured even at a position extremely close to the outermost circumference of the magnetic disk. Therefore, the writable area of the information signal can be expanded, and a magnetic disk suitable for high recording density can be provided.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration example of a magnetic disk of the present invention.

FIG. 2 is a cross-sectional view showing the structure of a disk substrate used for the magnetic disk of the present invention.

FIG. 3 is a characteristic diagram showing the relationship between the chamfered dimension and the number of head hits near the outer peripheral edge of the magnetic disk.

FIG. 4 is a cross-sectional view showing a configuration of a disk substrate used for a conventional magnetic disk.

[Explanation of symbols]

 1 ... Substrate 2 ... Ni-P plating film 3 ... Underlayer 4 ... Magnetic layer

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[Procedure amendment]

[Submission date] August 12, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0022

[Correction method] Change

[Correction content]

Therefore, 3.5 having the above-mentioned structure
For a hard disk of inch (diameter r = 47.5 mm from the center to the outer edge), the chamfering dimension of the substrate is 0.1
The flying head receives when changed in the range of 0.3 mm
The impact, the so-called head hit, was investigated.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0023

[Correction method] Change

[Correction content]

FIG. 3 shows a flying height of 0.1 μm.
FIG. 7 is a diagram showing a change in the number of head hits in the vicinity of the outer peripheral edge of the magnetic disk when the head is allowed to fly (4 micro inches) . In the figure, the horizontal axis represents the position of the magnetic head that is levitated and running, and the vertical axis represents the number of head hits measured at that position.

[Procedure 3]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenji Yazawa 6-5 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Magne Products Co., Ltd.

Claims (1)

[Claims] 1. A magnetic disk comprising a recording layer formed on a disk substrate having a chamfered dimension of 0.13 mm or less.