JP2532517B2 - Magnetic recording media - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic recording medium having a ferromagnetic metal thin film suitable for high density magnetic recording as a magnetic recording layer.

2. Description of the Related Art In recent years, the progress of high density magnetic recording has been remarkable, and attention has been paid to the short wavelength output characteristics of a magnetic recording medium having a ferromagnetic metal thin film as a magnetic recording layer [IE Transactions on Magnetics (IEEE Transactions
on magnetics) vcl.MAG-21, No-3, PP1217-1220 (19
85)]. In particular, since the perpendicular magnetic recording method is suitable for high density recording in principle, development is being continued in various fields in order to realize narrow track in digital signal recording and high density by shortening bit length.

From the standpoint of production, such a magnetic recording medium is directly Co-Cr, Co-Cr-Nb, Co-Cr-Nb, by electron beam evaporation method or high-speed sputtering method on a flexible substrate such as polyester film.
It is strongly desired that a perpendicularly magnetized film of Co-O or the like be formed to have a C / N that can be practically used and to have satisfactory durability.

Therefore, it has been considered to release sufficient gas from the polymer film beforehand [Abstracts of Papers of the Japan Society for Applied Magnetics 26aA-8 (1985), Journal of the Japan Society for Applied Magnetics, vol.11, N.
o2, PP69-72 (1987), etc.] The crystal orientation has been improved.

Problems to be Solved by the Invention However, even if a commercially available polyamide-imide film, polyimide film, or polyethylene terephthalate film is sufficiently pre-gassed, the bit length is 0.3 μm.
There is a problem that a magnetic tape having a sufficient C / N cannot be obtained when it is less than m, and improvement has been desired.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a magnetic recording medium capable of obtaining a sufficient C / N in high-density recording / reproduction.

Means for Solving the Problems In order to solve the above problems, the magnetic recording medium of the present invention is formed on a film in which the crystal grain sizes of the crystal parts constituting the polymer film are substantially the same in the longitudinal direction and the orthogonal direction. It has a ferromagnetic metal thin film.

Action According to the above-mentioned configuration, since it is amorphous except for the crystal part and has no particular directionality, when it is macroscopically considered in terms of mechanical strength, even if there is directionality due to the strengthening stretching, the crystal is isotropic. There is no directivity in the direction, the gap of the magnetic head formed in the three-dimensional micro surface and the stable contact followability are obtained, and the spacing loss, which is a serious loss at shorter wavelengths, is significantly increased. As a result of the improvement, the C / N can be improved and secured even at a bit length of 0.3 μm and a recording wavelength of 0.6 μm or less, and there is no microscopic directionality, and the crystal growth of the ferromagnetic metal thin film is uniform, so the magnetic characteristics And the physical properties of thin films are improved,
C / N can be improved.

Examples Hereinafter, examples of the present invention will be described in detail with reference to the drawings. FIG. 1 is an enlarged cross-sectional view of a magnetic recording medium according to an embodiment of the present invention, and FIG. 2 is a characteristic diagram showing the relationship between crystal grain size anisotropy and C / N of a polymer film used in the present invention. .

In FIG. 1, 1 is polyethylene terephthalate,
A polymer film of polyethylene 2.6-naphthalate, polyphenylene sulfide, polyether sulfone, etc., having the same grain size in the longitudinal direction and in the direction orthogonal to it, such as when the crystal grain size was used to construct a magnetic tape. However, the other mechanical properties, optical properties, etc. are not particularly limited. However, the crystal grain size is 70 Å or less, more preferably 60 Å or less, because it has a slight correlation with the short wavelength C / N. The particle shape of this polymer film can be easily measured by X-ray diffraction. further,
The thickness of the polymer film is preferably 4 μm to 15 μm for a magnetic tape and 20 μm to 60 μm for a magnetic disk. If necessary, the fine particles may be arranged on the polymer film, but when a resin is used particularly for fixing the fine particles, it is preferable to thoroughly study the amount of adhesion and to suppress the amount. As for these fine particles, from 50Å
500Å SiO ₂ , Al ₂ O ₃ , CaCo ₃ , BaCo ₃ , MgO, TiO ₂ , ZrO ₂ , ZnO, Eu
_{A material in which 2} O ₃ , Cr ₂ O ₃ , Fe ₂ O _{3 and the} like are arranged in a range of 0.1 to 100 μm ² is suitable, but the fine particle substance is not limited to the above-mentioned inorganic fine particles, and may be organic fine particles.

Adjusting the particle size by heat-treating a film with a draw ratio of 1.5 to 2 times in the longitudinal direction (relative to the longitudinal direction) at a temperature near the glass transition temperature (68 to 72 ° C) for a long time (10 to 120h). By performing the above, a polymer film under the above conditions can be obtained.

2 is a ferromagnetic metal thin film, which is Co-Ni, Co-Fe, Co-Cr, Co-
O, Co-P, Co-Re, Co-Ta, Co-W, Co-Ni-O, Co-Cr-Nb, C
It consists of an obliquely evaporated film such as o-Ni-Pr-O, a perpendicular magnetization film, etc., and can be formed by electron beam evaporation method, ion plating method,
It is formed by a high-speed sputtering method or the like, and may have a film thickness of 300 Å to 3000 Å, and may have a multi-layer structure if necessary.

Reference numeral 3 is a protective lubricating layer composed of a combination of an amorphous carbon thin film, MoS ₂ , WS ₂ sputtered thin film, plasma polymerized film, fatty acid film, fatty acid amide film, perfluoroalkylcarboxylic acid film and the like.

Hereinafter, an example of the present invention will be described more specifically in comparison with a comparative example.

With a 10 μm thick polyethylene terephthalate film, the crystal grain size that constitutes the crystal part is 54 Å within the measurement error in the longitudinal direction and the direction orthogonal to it. Prepare a base B and a base C having a length of 52Å and an orthogonal direction of 56Å.
It was drawn by stretching 3.1 times and then heat-treated at 69 ° C for 8 hours. Base B was used 2.4 times in the longitudinal direction and 1.9 times in the orthogonal direction without heat treatment. Base C was 1.7 times in the longitudinal direction and orthogonal direction. 2.8 times used without heat treatment), all films had the same roughness as average roughness of 30Å and maximum roughness of 70Å, and Fe ₂ O ₃ fine particles with diameter of 60Å were dispersed in isopropyl alcohol and applied. , Dry, and dispose fine particles that can form protrusions with an average diameter of 15 μm ² by high frequency sputtering
Co-Cr (Co, 78wt% ) perpendicular magnetization film 0.1μm formation, graphite as a target, Ar and H ₂ partial pressure ratio Ar / H ₂ -2 /
Using discharge gas mixed with 1), 13.56MHz 2.2 at 0.05 Torr
A hard carbon thin film was placed 100 Å by a sputtering method using KW glow discharge, and 5% of perfluorooctanoic acid was placed on it.
0Å Vacuum deposition, each 8mm width, magnetic tape,
Gap length of 0.12μ due to the modified 8 mm VCR
A rectangular wave having a track width of 8 μm and a bit length of 0.22 μm was recorded by a sendust head of m, and the C / N at a band of 9 MHz was compared. The one using the base A was improved by 3.4 dB C / N as compared with the one using the base B, and the one using the base C was lower by 0.5 dB C / N than the one using the base B. That is,
When the polymer film base A made of crystals having substantially the same diameter in the longitudinal direction and the orthogonal direction is used, the best C /
You can get N.

Now, a ferromagnetic metal thin film using the same bases A, B, and C and changing from Co—Cr to Co—Ni will be described below. Minimum incident angle of 50 along a cylindrical can with a diameter of 1 m
And oxygen partial pressure of 5.9 × 10 ^-5 Torr in Co-Ni (Co; 80wt
%) Was evaporated to form a magnetic tape from a Co-Ni-O thin film. Bit length 0.28μm, Track width 6μm
And C / N is base B when OdB is the one using base C.
The one using + 1dB, the one using base A is + 4.2dB
And the one using the base A was the best.

FIG. 2 is a characteristic diagram showing the effectiveness of the present invention, including the second experimental example using a Co—Ni—O thin film. As can be seen from the figure, when the particle size ratio deviates from the range of 0.98 to 1.02, the average value of C / N and the variation become worse,
The usefulness of the product of the present invention can be understood. In the present invention, the grain size in the longitudinal direction and the grain size in the orthogonal direction are the same, which means an average value obtained by arbitrarily measuring at least 5 crystal grain sizes of the film, and the grain size ratio includes a range of 0.98 to 1.02. It is defined. The data shown in FIG.
It covers the range from 80Å to 47Å. Also,
Fig. 2 shows a comparison of initial values.
As a result of the experiment, it was found that, when used for 00 hours, the variation was further increased except for the products of the present invention. Therefore, it can be said that the product of the present invention ensures secure stable spacing, which is important in short wavelength recording and reproduction. It is also noteworthy that the product of the present invention is useful from a manufacturing standpoint, and the above-mentioned performance can be uniformly obtained in a large area within the range of degassing treatment which can be carried out by a person skilled in the art. In addition to polyethylene terephthalate, the above-described effects can be obtained similarly in the above-mentioned polymer films, if the crystal grain sizes are substantially the same in the orthogonal direction and the longitudinal direction.

EFFECTS OF THE INVENTION According to the present invention, excellent C / N in short wavelength recording / reproducing
Has an excellent effect that it can be obtained even in the initial stage and continuously in actual use.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of a magnetic recording medium of one embodiment of the present invention, and FIG. 2 is a characteristic diagram showing the relationship between the conditions and characteristics of this embodiment. 1 ... Polymer film, 2 ... Ferromagnetic metal thin film, 3 ...
Protective lubrication layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Osamu Obama 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Takashi Fujita 1006 Kadoma, Kadoma, Osaka Matsushita Electric Industrial Co., Ltd. Within

Claims (1)

(57) [Claims] 1. A magnetic recording medium in which a ferromagnetic metal thin film is provided on a polymer film having a crystal grain size of a crystal portion which is substantially the same in the direction orthogonal to the longitudinal direction.