JPS61202324A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent the increase in DC erasing noise by forming a dry type magnetic film on a substrate having flaws in the direction along the traveling direction of a playback head. CONSTITUTION:The flaws 2 are provided approximately concentrically or spirally on the nonmagnetic substrate 1 along approximately the running direction of the playback head, in the case of, for example, a magnetic disk and the magnetic film 4 is constituted on the surface-treated surface of such substrate 1 by a dry type plating treatment, then the dry type plating magnetic film receives the influence of the substratum surface of the film and is provided with the magnetic anisotropy having the axis of easy magnetization in the direction along the traveling direction of the playback head. The increase in the DC erasing noise is thereby eliminated and the orientation is made constant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium such as a dry plating type magnetic disk.

[Prior art and its problems]

For example, magnetic disks used as storage media for computer peripherals include coated disks and plated disks using dry or wet plating means.

Among these, the plated type does not use a binder resin to form the magnetic film, in other words, it is a Co-based magnetic alloy material provided on a non-magnetic substrate by a plating method such as sputtering. Although it has a high packing density and is suitable for increasing density, this is not completely satisfactory, and further research is continuing.

In other words, conventional dry-plated magnetic disks are easily magnetized in the radial direction because the axes of easy magnetization within the film plane of the plated magnetic film are equidirectional, or due to the influence of the magnet of the sputtering device. Because the axes were oriented in different directions, problems remained in terms of playback output, resolution, etc.

[Disclosure of the invention]

The inventors of the present invention believe that the dry-plated magnetic film of a magnetic disk formed by a paper deposition method such as sputtering may be greatly affected by the surface condition of the underlying film during the film-forming process. As a result of continued research based on this idea, it was discovered that the direction of the axis of easy magnetization of a dry-plated magnetic film is influenced by the surface condition of the underlying film, and from this point of view, the present invention was achieved.

For example, in the case of a magnetic disk, scratches are made on the non-magnetic substrate in a substantially concentric or spiral pattern in a direction substantially along the running direction of the read head. When a magnetic film is formed by dry plating on the surface-treated surface of a non-magnetic substrate, this dry-plated magnetic film is influenced by the underlying surface of the dry-plated magnetic film and is They discovered that it has magnetic anisotropy with an axis of easy magnetization in the direction.

Note that the degree of scratches formed on this non-magnetic substrate is minute, and for example, as a standard for the depth of scratches, it is approximately 0.002 to 0.1 μm expressed as center line average roughness Ra. The pitch is preferably about 50 μm or less, more preferably about 0.1 to 10 μm.

In other words, if the center line average roughness Ra is smaller than 0.002 μm, the alignment effect will be small.
On the other hand, if the center line average roughness Ra is larger than 0.1 μm, it is difficult to ensure the flying stability of the reproducing head, and for example, head crashes are more likely to occur. Moreover, if the pitch of the scratches becomes too large, exceeding 50 μm, the alignment effect will be reduced.

Such scratches can be easily created by, for example, placing abrasive grains on the surface of the non-magnetic substrate and rotating the non-magnetic substrate. The magnetic recording medium of the present invention can be obtained by placing it in a sputtering device and sputtering magnetic particles to form a film on the surface of a nonmagnetic substrate under predetermined sputtering conditions.

[Examples 1 to 4] FIGS. 1a and 1b are explanatory diagrams of the manufacturing process of an example of a magnetic recording medium according to the present invention.

First, as shown in Figure 1a, Ni-P with a thickness of about 1.9
An At substrate 1 with a plating film is prepared, and a scratch 2 having a scratch direction substantially along the circumferential direction is formed on the surface of the substrate 1 using the polishing means described above.

Furthermore, the depth of this scratch 2 has a center line average roughness Ra of approximately 0.0029 to 0.0435 M' according to Kristetsub.
Moreover, the pitch of the scratches 2 is approximately 1 μm.

Thereafter, the substrate 1 with the scratches 2 is placed in a sputtering device, and the predetermined sputtering conditions (argon gas pressure 2 x 10 -
A Cr film 3 is formed to a thickness of about 400 OA (3 Torr), and then a Co--Ni magnetic film 4 is formed to a thickness of about 600 Å to form a magnetic disk.

[Examples 5 to 8] The center line average roughness Ra was approximately 0.00 in the same manner as in Example 1.
N with scratches of 36 to 0.0419 μm and a pitch of approximately 1 μm, with the scratch direction approximately along the circumferential direction.
The At substrate with the 1-P plating film was moved, the scratched substrate was placed in a sputtering device, and a Cr film was applied at a rate of about 40 mm under predetermined sputtering conditions (argon gas pressure of 5 x 10-3 Torr).
0OA thick, followed by Co-Ni magnetic film about 60OA thick.
The magnetic disk is formed thickly to form a magnetic disk.

〔Characteristic〕

Regarding the magnetic disks obtained from each side above, the playback output,
Resolution, Wlo (half width of isolated reproduced waveform), C/N,
Dse (frequency when the output becomes negative), Hc (coercive force) and noise (1' when recording a 5MHz signal,
The peak value near 5 MHz) is as shown in the table.

Table As can be seen from this table, magnetic recording media in which a magnetic film is formed by sputtering on a non-magnetic substrate surface with scratches along the circumference have a large Hc, a high reproduction output, and a low resolution. Good, even W5゜, C/N, D so
The performance is good, and the noise is also small.

In other words, a structure in which a dry plating magnetic film is formed on a surface with scratches along the running direction of the playback head can achieve high output. There is no increase in DC erase noise, probably because leakage magnetic fields are less likely to occur because it is along the same direction, and since the degree of scratches is almost constant, the orientation is almost constant, so there is no output fluctuation. It's small.

〔effect〕

It has high reproduction output, excellent resolution, and can perform high-density recording with little DC erase noise.

[Brief explanation of drawings]

FIGS. 1a and 1b are explanatory diagrams of the manufacturing process of an embodiment of the magnetic recording medium according to the present invention. 1... Substrate, 2... Scratch, 3... Cr film, 4...
Co-Ni magnetic film. Ding 1 diagram

Claims (1)

[Claims] A magnetic recording medium characterized in that a dry plating magnetic film is formed on a substrate having scratches in a direction substantially along the running direction of a reproducing head.