JPH079690B2 - Magnetic recording medium - Google Patents

Description

TECHNICAL FIELD The present invention relates to a magnetic recording medium having a ferromagnetic metal thin film as a magnetic recording layer, which is suitable for high density magnetic recording and reproduction.

Conventional technology Conventionally, those widely used as a magnetic recording layer are γ-Fe ₂ O ₃ , Co-doped γ-Fe ₂ O ₃ , CrO ₂ or,
Ferromagnetic metal or alloy fine powder magnetic material such as iron is dispersed in an organic binder such as vinyl chloride, vinyl acetate copolymer, styrene-butadiene copolymer, epoxy resin, etc., and coated and dried on a substrate such as polymer film. It is a coated magnetic layer.

However, since the saturation magnetic flux density of such a coating type magnetic layer is approaching the upper limit and the thickness cannot be made too thin, there is a limit to the signal-to-noise ratio (hereinafter referred to as S / N) in short wavelength recording / reproducing. In order to break through this limit, magnetic recording media using a ferromagnetic metal thin film as a magnetic recording layer have attracted attention and are being actively developed (for example, foreign journals, IEEE Trans.
actions on Magnetics Vol.MAG-21, No.3, 1217-1220
(1985)] In order to put a ferromagnetic metal thin film into practical use as a magnetic recording layer, it is possible to improve the durability against high-speed sliding with a magnetic head while maintaining excellent electromagnetic conversion characteristics. I have a suggestion. (For example, JP-A-53-88704
No., JP 59-121631, JP 59-171026) Based on the proposals so far, magnetic tapes and magnetic disks were prototyped and evaluated. If the magnetic head was a ferrite head, Although it is possible to approach the practical level, the recent trend is to improve the short wavelength output by increasing the coercive force, and the magnetic head material tends to shift to the alloy system.

Problems to be Solved by the Invention When the magnetic head is made of an alloy system, metal / metal contact is likely to occur and an adhesion phenomenon is likely to occur.
It is not possible to obtain the durability as obtained by combining with a ferrite head. Especially, the shorter the wavelength,
Due to the spacing loss, which increases the loss, a magnetic recording medium that is less likely to cause the phenomenon of foreign matter adhering to the head surface is required.

The present invention has been made in view of the above circumstances, and provides a magnetic recording medium that can sufficiently secure a stable S / N for high-density recording / reproduction due to a narrow wavelength and a narrow track even if an alloy head is used. .

Means for Solving the Problems In order to solve the above problems, the magnetic recording medium of the present invention is configured such that the thickness of the surface oxide layer of the columnar crystal grains forming the ferromagnetic metal thin film changes periodically. It has a magnetic recording layer.

The magnetic recording medium of the present invention has the above-mentioned structure, and the front surface of the magnetic head, the magnetic tape,
The hitting force of a flexible medium such as a magnetic disk has a repeated phenomenon. That is, microscopically, the hardness repeatedly becomes large, small, large, and small, and a short-time acting force, that is, an impact force repeatedly acts on the front surface of the head, and even if foreign matter adheres. However, the time to remove it is extremely short, and there is no problem in practical use, so even at extremely short wavelengths.
S / N can be maintained.

EXAMPLES Examples of the present invention will be described below with reference to the drawings. FIG. 1 is an enlarged sectional view of a magnetic recording medium according to an embodiment of the present invention, and FIG. 2 is an internal configuration diagram showing an example of a vapor deposition apparatus used for manufacturing the magnetic recording medium of the present invention.

In FIG. 1, reference numeral 1 is a polymer film, here a thickness of 10 μm.
Polyethylene terephthalate is used, and there is a mountain-shaped polymer coating layer on the surface, and the average height of the mountain range is 75
It is Å.

Reference numeral 2 is a magnetic recording layer composed of columnar crystal grains 3 and 4, that is, a ferromagnetic metal thin film. 5 is a surface oxide layer, particularly the surface oxide layer thickness d _A of the side in contact with the magnetic head, d _B is, it is larger than d _B of the d _A, the columnar crystal grains 3 and d _B having a thickness of d _A The columnar crystal grains 4 having a thickness are configured to be periodically repeated. Although FIG. 1 schematically shows three particles each, in reality, the number of particles is much larger.

Further, although related to a manufacturing method described later, d _A and d _B are not necessarily digitally changed and may have a gradually changing region, but in that case, the action and effect are not changed and are included in the present invention. It is what is done.

In FIG. 2, 6 is a polyethylene terephthalate film which is a polymer film, 7 is an unwinding shaft, 8 is a winding shaft, 9 is a cylindrical can, 10 is an evaporation source container, 11 is a vapor deposition material,
Reference numeral 12 is a vapor deposition flow, 13 is a mask, 14 is an oxygen introduction pipe, 15 is a needle valve, 16 is an oxygen ion source, 17 is a scanning coil, and 18 is an oxygen ion beam.

In FIG. 2, the cylindrical can 9 has a diameter of 1 m, the evaporation source is an electron beam evaporation source, the evaporation surface is arranged 40 cm directly below the can, and the mask 13 is set so that the minimum incident angle is 40 degrees. 16 uses Penning discharge, maximum 2mA,
At the cylindrical can position where the minimum incident angle was 40 degrees, the angle between the vapor flow and the ion beam was about 30 degrees. The ion beam was turned on and off by changing the grid potential in a pulsed manner to adjust the oxide layer thicknesses d _A and d _B. The film winding speed and the grid potential pulse interval were adjusted to adjust the period in which the thickness of the oxide layer changed.

Various media were prepared with a Co-Ni-O (Ni; 20 wt%) film of 0.15 μm, and a sendust sputter head (gap of 0.26 μm,
Recording / reproduction of 0.6 μm was performed with a track width of 10 μm, and the time when the output decreased by 6 dB or less was integrated and evaluated. The recording time is 120 minutes, and it is the integrated value for a total of 1,000 hours after repeated reproduction.

On the surface of the magnetic recording layer, about 50Å vacuum deposition of perfluorooctanoic acid was performed, and the recording / reproducing environment was 35 ° C 40% RH.

The following table also shows the results of relative comparison of S / N after 1,000 hours of driving with the initial one.

Almost the same results as shown in the above table are obtained under other environmental conditions, namely,
It can be obtained at 5 ℃ 15% RH, 20 ℃ 65% RH, 40 ℃ 80% RH,
Almost all data were obtained using an amorphous sputter head as a magnetic head and a bulk sendust head.

Although polyethylene terephthalate film is used in the above embodiment, polyethylene naphthalate, polysulfone film, polyphenylene sulfide, aramid film, polyimide film or the like may be used.

The magnetic recording layer does not depend on the direction of the easy axis of magnetization,
In addition, Co-Ag, Co-Cr, Co-Ti, Co-Mg, Co-Mo, Co-Cr-Nb,
A partial oxide film of Co-Ni-P may be used.

Further, it is needless to say that not only the magnetic tape but also a disk can be used to obtain the same effect.

As described above, according to the present invention, it is possible to effectively remove foreign matter from the front surface of the head, which causes instability of spacing loss at short wavelengths. Even if it is retained, it has an excellent effect.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view of a magnetic recording medium according to an embodiment of the present invention, and FIG. 2 is an internal configuration diagram of an example of a vapor deposition apparatus used for manufacturing the magnetic recording medium of the present invention. 1,6 ... Polymer film, 2 ... Magnetic recording layer, 5 ... Surface oxide layer, 11 ... Vapor deposition material, 14 ... Oxygen introduction pipe, 16
...... Oxygen ion source.

Claims (1)

[Claims] 1. A magnetic recording medium in which the thickness of a surface oxide layer of columnar crystal grains constituting a ferromagnetic metal thin film is periodically changed.