JPH10162335A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a recording medium improved in coercive force by disposing ground surface films on a nonmagnetic substrate consisting of glass, silicon, titanium, etc., then forming a Co-base magnetic film and successively forming a first Cr thin film, Ti-base thin film and second Cr thin film as the ground surface films. SOLUTION: The first Cr thin film, the Ti-base thin film and the second Cr thin film are successively formed on the nonmagnetic substrate formed of the soda glass, aluminosilicate glass, silicon, titanium, ceramics or various kinds of resins. The first Cr thin film is preferably formed to 100 to 1000Å film thickness and the Ti-base thin film to about 100 to 2000Å film thickness. The second Cr thin film is adjusted preferably to 100 to 1000Å and are formed thereon. The perpendicular orientation of the Ti-base thin film is weakened by providing the substrate with the first Cr thin film and the influence of degassing from the substrate is eliminated by the Ti-base thin film. The crystalline structure of the Co thin film is made into intra-surface orientation by the second Cr thin film. The recording medium having the high coercive force is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium used for a magnetic disk drive or the like.

[0002]

2. Description of the Related Art A magnetic disk medium is formed, for example, on a NiP electroless-plated Al-Mg alloy substrate by a sputtering method using a Cr undercoat film, a Co magnetic film, or a protective layer mainly composed of C or the like. Are generally formed in this order. In recent years, from the viewpoint of impact resistance and surface smoothness, Al
-Substitute substrates such as glass, silicon, titanium, etc. have begun to be used instead of Mg-based alloy substrates.

However, in these alternative substrates, Al
-It is relatively difficult to obtain sufficient magnetic properties, especially coercive force, as compared to Mg-based alloy substrates. In order to solve this problem, attempts have been made to secure magnetic properties by previously applying a Ti thin film layer on a substrate such as glass, but it has not been possible to obtain a sufficient coercive force (Japanese Patent Application Laid-Open No. 2
No. 29923).

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic recording medium using such a substrate made of glass, silicon, titanium or the like and having an improved coercive force.

[0005]

Means for Solving the Problems In order to achieve the above object, the present invention has been found to solve the problem by providing a special base film on a substrate made of glass, silicon, titanium or the like, and completed the present invention. did. The gist of the present invention is to provide a magnetic recording medium in which at least a base film and a Co-based magnetic film are formed on a non-magnetic substrate.
A magnetic recording medium characterized in that an r-based thin film, a Ti-based thin film, and a Cr-based thin film are provided in this order.

For convenience, a Cr-based thin film on the substrate side is referred to as a first C
The r-based thin film and the Cr-based thin film on the Ti-based thin film will be referred to as a second Cr thin film. As the non-magnetic substrate in the present invention, a substrate other than the aluminum alloy substrate is preferably used. Substrates other than the aluminum alloy substrate include, for example, soda glass, aluminosilicate glass, silicon, titanium, ceramics, various resins, and the like.

Further, as the non-magnetic substrate, a substrate obtained by subjecting an aluminum alloy such as an Al-Mg alloy to NiP plating may be used. The surface of the substrate has a surface roughness (Ra) of 5
鏡 It is preferable to have the following mirror finish. Washing·
After drying, each film is provided on the surface of the substrate.

The surface of the substrate, the surface of the base film, the surface of the magnetic film and the like may be subjected to mechanical texturing or texturing using a laser beam or the like. It has no effect on the effect. When the texturing process is performed, usually, a material having a surface roughness (Ra) of about 5 ° to 50 ° is used.

In the present invention, a first Cr thin film, a Ti-based thin film, and a second Cr thin film are sequentially formed on a non-magnetic substrate. As materials for the first and second Cr thin films, in addition to pure Cr,
C for the purpose of improving the crystal matching with the Co layer
r is V, Ti, Mo, Zr, Ta, W, Ge, Nb, C
u and other second and third elements, and Cr oxide.

The optimum content of the second and third elements differs depending on the respective elements.
To 50 at%, preferably 5 to 30 at%, more preferably 10 to 20 at%. The first Cr thin film is provided for crystallographically controlling the magnetic characteristics (the orientation direction of the axis of easy magnetization) of the base film and the magnetic film. The layer has a crystal structure.

By making the crystal structure of the first Cr thin film into a body-centered cubic lattice, the Ti-based thin film provided thereon originally has the function of making the easy axis of magnetization a vertical orientation closer to an in-plane orientation. Seem. The thickness of the first Cr thin film is 100Å
If the degree is equal to or more than the above, an effect of in-plane orientation of the easy axis can be obtained, but it is practical to use usually about 10 to 5000 °. Desirably from 100 to 100 from the viewpoint of productivity and the like.
About 0 ° is preferable.

As the Ti-based thin film, pure Ti (including one containing another component as an impurity) is usually used. However, the affinity with the first Cr thin film and the second Cr thin film is improved. For the other purpose, the second and third components may be contained. In the present invention, the Ti-based thin film provided between the first Cr thin film and the second Cr thin film plays a role of adsorbing and blocking various impurity gases such as water vapor and oxygen generated from the substrate. It is provided for the purpose of preventing the deterioration of.

[0013] Compared to a conventionally used metal substrate,
These substitute substrates tend to generate this impurity gas, which significantly degrades the magnetic properties of the magnetic thin film. The Ti thin film functions to prevent this. The material of the Ti thin film is most preferably pure Ti, but the effect is not significantly affected even if the second and third elements are contained at 10 atomic% or less.

The effect can be obtained if the thickness of the Ti thin film layer is about 100 ° or more, and it is preferable from an industrial point of view to use it at about 100 to 2000 °. The second Cr thin film is Co
This is to make the magnetic properties of the thin film suitable for an in-plane magnetic recording medium. Specifically, the second Cr thin film has a body-centered cubic lattice structure, and has a (111) plane or a (20) plane.
0) Orient to the plane.

Then, a Co thin film continuously formed thereon is epitaxially grown, and its crystal structure is oriented strongly on the (110) plane or the (111) plane of a dense hexagonal lattice. If the second Cr thin film is not provided, the crystal structure of the Ti thin film has such a property that the dense hexagonal lattice is easily oriented to the (002) plane.
2) It becomes easy to orientate strongly on the surface.

In such a crystal structure, the Co-based thin film exhibits magnetic characteristics suitable for perpendicular magnetic recording rather than in-plane magnetic recording, and thus is not suitable as an in-plane (longitudinal) magnetic recording medium. The second Cr thin film alleviates the properties of the Ti thin film that are not suitable for such a longitudinal magnetic recording medium by utilizing the function of the Cr film to orient the Co film in the (111) or (110) plane. It is intended to be.

That is, by providing the first Cr thin film,
Weakens the vertical orientation of the Ti-based thin film, eliminates the adverse effects of outgassing from the substrate with the Ti-based thin film, makes the crystal structure of the Co thin film in-plane with the second Cr thin film, and provides an excellent in-plane high coercivity on the substrate. (Longitudinal) magnetic recording media can be provided. The thickness of the second Cr thin film can be arbitrarily set in accordance with the target magnetic properties of the medium, but is usually adjusted to about 100 to 1000 °.

The materials for the Co-based magnetic thin film include all commonly used materials for magnetic disks. For example,
CoNiCr, CoCr, CoCrTa, CoCrP
t, CoCrPtTa, CoCrPtB, CoNiP
t, an alloy such as CoNiCrBTa or CoSm.

An optional protective layer may be provided on the uppermost portion of these media. As a material of the protective layer, a C film such as an amorphous carbon film or a hydrogenated carbon film, or a Si film is used.
All commonly used protective layer materials such as O2 and Zr2O3 are included. Further, the protective layer may be composed of two or more layers. Further, an arbitrary lubricant such as a fluorine-based liquid lubricant is generally applied to the upper part of the protective layer.

A film forming method for forming a base film and a Co-based magnetic film on a non-magnetic substrate may be a physical vapor deposition method such as a direct current sputtering method, a high frequency sputtering method, and a vacuum evaporation method. Further, even if a film is formed while applying a constant voltage to the substrate, the effect of the invention is not affected at all. In this case, a voltage is applied to the substrate by applying a voltage to the conductive film formed in advance. The value of the substrate bias voltage can be set arbitrarily according to the characteristics of the target medium, but is usually about several hundred volts.

In the film formation, the film formation conditions are appropriately selected, and after forming the base film layer, the film is once taken out into the atmosphere, inserted again into the film forming apparatus, evacuated and heated, and then the Co-based magnetic layer is formed. Although the magnetic recording medium of the present invention can
It can be manufactured by continuous sputtering of an r thin film, a Ti thin film, a second Cr thin film, and a Co-based magnetic layer. In this case, mass production can be achieved by an in-line apparatus and the cost of the product can be reduced.

After the formation of the Co-based magnetic thin film, generally, an amorphous carbon protective film or a hydrogenated carbon protective film is continuously formed by an in-line apparatus, and thereafter, a liquid lubricant or the like is applied. It is. Note that it is preferable to form a film after preheating the substrate except for a substrate having no heat resistance, such as a resin substrate, at the time of film formation because excellent magnetic characteristics can be obtained.

[0023]

EXAMPLE A substrate for a magnetic disk having a diameter of 65 mm and a thickness of 0.645 mm made of aluminosilicate glass was prepared, and a medium was formed thereon using a high-frequency magnetron sputtering method. At this time, the degree of vacuum in the sputtering apparatus was exhausted to 1.5 × 10 ⁻⁶ torr in advance. Further, the substrate temperature during film formation is about 250
C. and the argon gas partial pressure was 5.0 × 10 ⁻³ torr.

As an example, a first Cr thin film, T
A medium formed in the order of an i-thin film, a second Cr thin film, and a Co-based magnetic thin film. As a comparative example, a medium formed by forming a Ti thin film, a second Cr thin film, and a Co-based magnetic thin film without forming a first Cr thin film. did. Here, Co ₇₆ is used as the material of the Co-based magnetic thin film.
Cr ₁₂ Pt ₁₂ alloy was used. Examples, layer configurations of comparative examples,
And the magnetic properties are shown in Table 1.

[0025]

[Table 1]

FIG. 1 is a plot of the coercive force Hc of the comparative example and the example with respect to the residual magnetic flux density Brt. In a region having an extremely small Brt value, the coercive force is low, which is a general phenomenon due to the influence of thermal fluctuation. As is evident from the comparative example data in the figure, even if glass was used for the substrate, a Ti base thin film was applied, and a second Cr thin film and C
A high coercive force can be obtained by forming an o-based magnetic thin film.

However, when the first Cr thin film was further provided under the Ti thin film as in the embodiment in the figure, the coercive force value of the medium was further increased. In particular, the residual magnetic flux density Brt is 70 Gm
It was found that the effect was great in the above region.

[0028]

According to the present invention, a sufficiently high coercive force can be obtained even when a glass, silicon, or titanium substrate is used.

[Brief description of the drawings]

FIG. 1 shows the coercive force Hc of a comparative example and an example as a function of residual magnetic flux density.
Graph plotted against Brt

Claims (2)

[Claims] 1. A non-magnetic substrate comprising at least a base film, Co
1. A magnetic recording medium comprising a magnetic recording medium on which a Cr-based thin film, a Ti-based thin film, and a Cr-based thin film are provided in this order from the substrate side as a base film. 2. The magnetic recording medium according to claim 1, wherein the non-magnetic substrate is a glass substrate.