JPH0711857B2 - Magnetic recording medium - Google Patents

Description

TECHNICAL FIELD The present invention relates to a magnetic recording medium suitable for high density magnetic recording.

2. Description of the Related Art A magnetic recording medium using a ferromagnetic metal thin film as a magnetic recording layer is usually a ferromagnetic metal thin film directly on a polymer film which is a substrate by electron beam evaporation, sputtering or the like or through an underlying thin film. It is expected to be a leading player in high-density magnetic recording because it can increase the reproduction output of signals recorded as short wavelengths.

[Foreign papers IEEE Transation on Magnetics]
vol.MAG-21, PP1217 to 1220 (1985)] On the other hand, in order to realize high density magnetic recording, direct high-speed sliding with a narrow gap length, narrow track magnetic head is essential. Abrasion and damage of the layer became a problem, and many proposals have been made for improvement.

For example, the method of applying a lubricant on the surface of a ferromagnetic metal thin film (see Japanese Patent Publication No. 39-25246) has poor durability because the lubricant is wiped off by the magnetic head, running system and the like.
A method of providing a back coat layer containing a liquid or semi-solid lubricant and an organic binder as a main component on the surface opposite to the magnetic recording layer (see Japanese Patent Publication No. 57-29769) is also proposed, but it is tape-shaped. However, the disadvantages are that the transfer amount differs depending on the environmental conditions, that it has no effect on the still state, and that it has no effect on the disk-shaped medium.

In addition, improvement of durability by a protective film such as a plasma polymerization protective layer of a fluorine-based organic compound, a plasma polymerization protection layer of a silicon-based organic compound, and a polymer coating layer containing particles, or the combined use of these protective film and a lubricant is strongly recommended. Magnetic metal thin film is Co-
A considerable improvement has been confirmed in the case where an Ni-O film or the like has an oxide layer on its surface (for example, JP-A-58-88828 and JP-A-57).
-82229, JP-A-58-60427, JP-A-61-11930).

Problems to be Solved by the Invention However, in the above-described configuration, the magnetic recording layer such as the Co--Cr system perpendicular magnetization film cannot be sufficiently protected, and therefore the error rate rapidly increases or the output is damaged due to repeated recording and reproduction. There was a problem that was not met. Further, even in the case of a Co-Ni-O-based film, when the magnetic head is made of an alloy, the above-mentioned problems occur in an environment with high humidity, and therefore improvement has been desired.

The present invention has been made in view of the above circumstances, and provides a magnetic recording medium having improved durability under a wide range of environmental conditions.

Means for Solving the Problems In order to solve the above problems, the magnetic recording medium of the present invention has a continuous film of diamond-like carbon and carbon formed on a ferromagnetic metal thin film.

Operation The magnetic recording medium of the present invention has the above-described structure, and because of the hardness of diamond-like carbon and the solid lubrication action of carbon, damage can be prevented even when it makes sliding contact with the magnetic head at high speed, and it is a continuous film. The lubricity of the connection property is extremely good, and excellent high density magnetic recording characteristics can be provided for a long time.

Examples Hereinafter, magnetic recording media according to examples of the present invention will be described with reference to the drawings.

FIG. 1 is an enlarged cross-sectional view of the magnetic recording medium of the first embodiment of the present invention. In FIG. 1, 1 is a polymer film such as a polyethylene terephthalate film having a thickness of 21 μm, and the surface roughness is 100 Å in peak toe valley value. 2 is a granular protrusion layer made of polymer latex having a particle size of 300 liters applied on the upper surface of the polymer film 1, and the particle density is 1 million particles / mm.
² (see, for example, JP-A-61-9822). Reference numeral 3 is a Co—Cr (Cr; 20 wt%) film having a film thickness of 0.15 μm and formed by high frequency sputtering. Reference numeral 4 is a protective film having a thickness of 150Å, which is a carbon film whose state changes in the thickness direction. I.e.
The one closer to the surface of the Co-Cr film 3 is a diamond-like hard carbon that gradually changes to carbon as it goes to the surface. The forming method is to start with hydrogen sputtering on graphite and add Ar to hydrogen. The carbon film under the above conditions is obtained by controlling the introduction position.

As a comparative example, such a magnetic recording medium of this example was prepared by sputtering a graphite film using hydrogen and Ar to form a constant carbon film in the thickness direction of 150Å.

As a result of forming both of them as a 3.5-inch disc and comparing them, it was found that the time required for the reproduction output of the rectangular wave having the bit length of 0.24 μm to decrease by 3 dB was 25 million passes in the outermost track of the 3.5-inch disc. However, the comparative example had 4.47 million passes.

FIG. 2 is an enlarged cross-sectional view of the magnetic recording medium of the second embodiment of the present invention. In FIG. 2, 5 is a polymer film such as a polyethylene terephthalate film having a thickness of 10 μm,
No. 6, for example, as described in JP-A-58-68224, a mixture of a silicone resin or styrene or butadiene rubber and a water-soluble polymer material is applied on a film to form a continuous film. Is a so-called earthworm-like film formed on the surface by stretching and has a height of 80Å. 7 is a Co film having a thickness of 0.12 μm formed by oblique vapor deposition in the incident angle range of 90 ° to 40 ° along a circumferential can with a diameter of 1 m.
-Ni-O film with coercive force of 1100 (Oe), squareness ratio of 0.78, Co; N
i; O was set to 63; 16; 21 in terms of atomic percentage. 8 is a carbon film formed by the sputtering method of graphite. The film thickness is 140 Å, and the sputtering atmosphere is mixed from hydrogen to argon so that it continuously changes from diamond-like hard carbon to graphite in the thickness direction. Optimum conditions were experimentally determined and configured by providing gas introduction nozzles at three locations in the longitudinal direction of the graphite target so that the gas atmosphere changes continuously. Reference numeral 9 is a myristic acid film having a thickness of 30Å formed on the carbon film 8 by a vacuum deposition method, and 10 is a back coat layer.
Binder polyester resin 11 and filler CaCO ₃ particles 1
It consists of two.

As a comparative example with respect to the magnetic recording medium of the present example, a constant carbon coating is formed in the thickness direction by 150 Å by sputtering of graphite using hydrogen and argon gas, and other configurations are the same as those of the above example. Prepared the one composed of.

Both of them were prepared as a magnetic tape of 8 mm width, and a signal with a recording wavelength of 0.75 μm was recorded by a sendust sputter composite ring head with a gap length of 0.29 μm, and the same track was repeatedly reproduced to observe the output state, The time to occur was measured. Temperature and humidity conditions are 40 ° C and 5% RH,
When carried out at 40 ° C. 84% RH and 0 ° C. 46% RH, respectively, it was 47 minutes, 44 minutes, 49 minutes in this example, compared with 16 minutes in the comparative example.
Minutes, 9 minutes, and 11 minutes.

Although polyethylene terephthalate is used as the polymer film in the above-mentioned examples, other materials such as polyimide, polyethylene naphthalate and polyamide imide may be used.

Further, as the ferromagnetic metal thin film, in addition to Co-Cr, Co-Ni-O, Co-O, Co-Pr, Co-Pt, Co-P, Co-Rh, Co-Ru, Co-Bi, C
It may be o-B, Co-Si, Co-Ti, Co-Mo, Co-W, Co-Cr-Nb or the like.

EFFECTS OF THE INVENTION As described above, according to the present invention, the hardness of diamond-like carbon provided on the ferromagnetic metal thin film and the solid lubrication effect of carbon cause a decrease in output during short wavelength recording / reproduction even after repeated use. It is possible to obtain a magnetic recording medium having excellent high density magnetic recording characteristics, and the effect is great.

[Brief description of drawings]

1 and 2 are enlarged cross-sectional views of the magnetic recording medium of each embodiment of the present invention. 1,5 …… Polymer film, 3,7 …… Ferromagnetic metal thin film, 4,8
...... Carbon film.

Claims (2)

[Claims] 1. A magnetic recording medium comprising a ferromagnetic metal thin film on which a continuous coating of diamond-like carbon and carbon is formed. 2. The magnetic recording medium according to claim 1, wherein the continuous film is formed by changing the composition ratio of carbon and diamond-like carbon in the thickness direction.