JP2610925B2 - Magnetic recording media - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium suitable for use as a recording medium for a magnetic disk and a magnetic tape.

[Conventional technology]

The magnetic recording medium adopts a configuration in which a protective film is laminated on a substrate with a magnetic film interposed therebetween, and various types have been proposed in which the alloy composition of the magnetic film is improved or the composition of the protective film is improved. I have.

As a material belonging to the former, the magnetic film material is "Co-Ni alloy" + Ti, Cr, Zr, Nb, Mo, Ta and W (Japanese Patent Laid-Open No. 55-105302), and the magnetic film composition is Co- 10-55at%
Ni-3 to 4.5 at% 0 (JP-A-56-15014), and the magnetic film composition was changed to Co-9 to 22.5 at% Cr-Y, Zr, Ti,
Mo, Hf, Ru, Al (JP-A-58-189349)
Further, there has been known a magnetic film having a composition of Co-Hf.Pt or Co-Zr-Pt (JP-A-59-116925). on the other hand,
As the latter, those in which the protective film is a mixed layer of graphite and diamond (JP-A-53-143206), graphite, diamond, SiC, WC, TiC , wbc, B ₄ and the one (JP 61-105720 JP) are known.

Those belonging to the former can improve the magnetic recording characteristics, and those belonging to the latter can improve the wear resistance.

[Problems to be solved by the invention]

However, in the above prior art, no consideration is given to the electrochemical action of the magnetic film or the protective film on the peripheral member, and the magnetic recording medium may be damaged by atmospheric corrosion.

That is, in the magnetic recording medium, as shown in FIG. 9, a protective film 3 is directly laminated on a substrate 1 with a magnetic film 2 interposed therebetween, and these layers are treated to suppress an electrochemical action. Is not given. That is, the magnetic film 2 is usually made of an alloy mainly composed of Co, and has a thickness of about 20 to 200 nm. The substrate 1 is made of glass, ceramics or Ni which is more corrosive to the atmosphere than the magnetic film 2.
Its thickness is thicker than the magnetic film 2 and several μm or more.
Further, the protective film 3 is made of graphite carbon, which is conductive and more excellent in atmospheric corrosion than the magnetic film 2, and has a thickness of about 20 to 200 nm. However, the protective film 3
Has small defects (pinholes) during manufacturing or use.
4 may be formed, and when moisture or corrosive components in the atmosphere dew on the protective film 3 on which the minute defects 4 are formed, the dew condensation water 5 penetrates into the magnetic film 2 through the minute defects 4. In some cases, the protective film 3 is corroded and damaged.

Here, when observing the form due to the corrosion damage in detail, the corrosion damage portion 6 proceeds along the protective film 3 or the substrate 1, and the magnetic film 2 or the protective film 3 bulges, whereby the progress of corrosion increases, and finally, In some cases, the corrosion damage portion 6 may be enlarged to such an extent that the magnetic recording medium cannot be used. The degree of the corrosion damage was more remarkably observed as the material of the substrate 1 or the protective film 3 was more excellent in atmospheric corrosion. This is presumably because corrosion was accelerated by the galvanic action in which the substrate 1 or the protective film 3 became a cathode and the magnetic film 2 became an anode.

An object of the present invention is to provide a magnetic recording medium that can suppress corrosion accompanying electrochemical action using a magnetic film as one electrode and a substrate or a protective film as the other electrode.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a method in which a protective film is stacked on a substrate via a magnetic film, and at least one of the substrate and the protective film has conductivity, and the conductive member and the magnetic film A layer of an insulating film is formed between at least one of the layers, and the electric resistance in the thickness direction of the layer is 10 ⁵ to 1
0 ¹⁰ Ω / cm ² .

Further, the protective film is made of graphite carbon, the magnetic film is made of an alloy mainly composed of Co, Ni and Zr, and the insulating film is made of an oxide mainly composed of ZrO ₂ or diamond-like carbon.

Further, the protective film is further divided into a plurality of regions, and the respective regions are dispersedly arranged in a discontinuous state.

[Action]

Even if micro-defects occur on the protective film and condensation water forms on the protective film, the circuit as an electrochemical action using the magnetic film as one electrode and the substrate or protective film as the other electrode is cut off by the insulating film. Thus, damage to the magnetic recording medium due to atmospheric corrosion is suppressed.

The magnetic film is made of an alloy mainly composed of Co, Ni and Zr,
If the insulating film is made of an oxide mainly composed of ZrO ₂ or diamond-like carbon, the adhesion of each layer is increased, and the progress of atmospheric corrosion can be further suppressed.

Further, when the protective film is divided into a plurality of regions, the area of the protective film in contact with the dew is reduced, so that the progress of atmospheric corrosion is suppressed as compared with the case where the protective film is not divided into a plurality of regions.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to FIG.

In FIG. 1, the holding plate 10 has a thickness of 3 mm and is made of an Al alloy. On the holding plate 10, a Ni plating substrate 12 having a thickness of 3 μm is laminated. On the substrate 12, a 100-nm-thick SiC insulating film 14 is laminated by plasma CVD. Further, a 50 nm thick magnetic film 16 is laminated on the insulating film 14. The magnetic film 16 is composed of a Co-based alloy containing 5% Cr and 9% Ni. Further, a 10-nm-thick insulating film 18 made of SiC is laminated on the magnetic film 16 by plasma CVD. Insulating film 1
A protective layer 20 made of graphite carbon having a thickness of 50 nm is laminated on the upper surface of FIG.

The magnetic recording medium having the above configuration includes a substrate 12 and a magnetic film 16.
The electrical resistance between the magnetic films is 5 × 10 ⁹ Ω / cm ^2.
And the protective film 20 has an electric resistance of 10 ⁸ Ω / cm ² .

The magnetic recording medium having the above configuration was kept in a desiccator at 85 ° C. and 95% RH for 100 hours, and the amount of corrosion damage was examined. As a result, the magnetic film 16 due to corrosion damage losing magnetism was 0.01% or less of the entire surface. Was. Under the same conditions as above, in the case where the protective film 20 is not provided, the corrosion damage of the magnetic film 16 is not affected.
2.3%.

Here, the reason why the electric resistance of the insulating film 14.18 is set to 10 ⁵ to 10 ¹⁰ Ω / cm ² is that if the electric resistance is set to 10 ⁵ Ω / cm ² or less, the progress of corrosion damage can be sufficiently suppressed. Is no longer possible. On the other hand, if the electric resistance is increased to 10 ¹⁰ Ω / cm ² or more, the progress of the corrosion damage only reaches the saturation region, the insulating film becomes thicker, the manufacturing cost increases, and the manufacturing work becomes difficult, resulting in an effect. Is not so good.

In the above embodiment, the insulating film 1 is formed on both sides of the magnetic film 16.
As described in FIG. 2, the insulating film 18 is formed only between the magnetic film 16 and the protective film 20, or as shown in FIG. Alternatively, the insulating film 14 can be formed only between the magnetic film 16 and the substrate 12.

In the case of the configuration shown in FIG.
However, the dew condensation water 24 does not infiltrate the magnetic film 16 until the minute defect 22 is generated in the insulating film 18 even if it occurs. On the other hand, in the case of FIG.
Penetrates into the magnetic film 16, but the insulating film 14 suppresses the dew condensation water 24 from entering the substrate 12. As a result, the second
3 and FIG. 3 were examined for corrosion damage under the same conditions as those shown in FIG. 1. The corrosion damage in FIG. 2 was 0.03%. Had a corrosion damage status of 0.07%.

Next, as shown in FIG. 2, as a magnetic recording medium, an insulating material 18 is formed only between the magnetic film 16 and the protective film 20, and the magnetic film 16 contains 5 to 15% of Ni and 2 to 10% of Zr. It is composed of a Co-based alloy, the insulating film 20 is composed of ZrO ₂ and diamond-like carbon, and the material of the other layers is composed of the same material as that of FIG. As a result of the test, it was confirmed that the amount of corrosion damage was 0.01% or less for both ZrO ₂ and diamond carbon. This allows
Even if the insulating film 18 is provided only on one side of the magnetic film 16, the same amount of corrosion damage as that shown in FIG. 1 can be obtained.
This magnetic film 16 Co, Ni, it was possible to improve the corrosion resistance of the magnetic film itself by the alloy of Zr, more of these by the ZrO ₂ and diamond carbon insulating film This is considered to be due to the fact that the adhesion between the layers was superior to those of other compositions.

Next, as shown in FIG. 4, the protective film 20 is divided into a plurality of island-shaped regions, and the size of each island-shaped protective film 20A is 10 to 3
1 μm × 50-100 μm, 50 nm thick, and the space between each island-shaped protective film 20A was filled with an insulating film 18 of ZrO ₂ , and a corrosion test similar to that of FIG. As a result, the amount of corrosion damage was 0.04%.

In the case of the present embodiment, even if the dew condensation water 24 occurs on the protective film 20, the island-shaped protective film 20A is dispersed and arranged, so that the protective film 20 is formed more than when the protective film 20 is formed on one surface. The contact area between 20 and the condensed water 24 is reduced, and the progress of atmospheric corrosion of the magnetic film 16 can be suppressed. This is because the amount of corrosion damage due to the galvanic action using the magnetic film 16 as one electrode and the protective film 20 as the other electrode is proportional to the contact area between the protective film 20 and the condensed water 24. This is considered to be due to a decrease in the amount of corrosion damage due to a decrease in the contact area between the water and the condensed water 24.

If the insulating film 18 is formed between the island-shaped protective film 20A and the magnetic film 16 as shown in FIG. 5, the dew water 24 penetrates into the magnetic film 16 more than in FIG. Can be suppressed.

In the case of laminating each film on the substrate 12, as shown in FIG. 6, an irregularity 12A or a groove is formed on the substrate 12, and an insulating material having a substantially similar shape to the irregularity 12A is formed on the irregularity 12A. film
By laminating the 14, the magnetic film 16, and the insulating film 18, the operation for laminating these layers can be easily performed.

Also, when forming the irregularities 12A on the substrate 12, as shown in FIGS. 7 and 8, if the irregularities 12A are formed in the circumferential direction of the magnetic disk, the radial speed of the magnetic head will increase the rotational speed of the magnetic disk. When the speed is higher than the direction, the movement of the magnetic head can be performed smoothly.

As described above, in each of the above embodiments, since the insulating film is formed on at least one of the two surfaces of the magnetic film 16, the progress of damage due to atmospheric corrosion is suppressed, and the life of the magnetic recording medium is extended. In addition, the reliability can be improved and the use environment can be expanded. Furthermore, the amount of corrosion damage due to atmospheric corrosion can be suppressed without using an expensive magnetic film having excellent corrosion resistance, which can contribute to cost reduction.

〔The invention's effect〕

As described above, according to the present invention, a film made of an insulating film is formed on at least one of the two surfaces of the substrate,
Since the circuit by electrochemical action using the magnetic film as one electrode and the substrate or the protective film as the other electrode is interrupted by the insulating film, corrosion damage due to atmospheric corrosion can be reduced and the length of the magnetic recording medium can be reduced. This can contribute to longer life and improved reliability. Further, by setting the magnetic film and the insulating film to specific compositions, the adhesion can be improved. Further, by dividing the protective film into a plurality of regions, it is possible to further reduce corrosion damage.

[Brief description of the drawings]

FIG. 1 is a sectional view of a principal part showing a first embodiment of the present invention, FIG. 2 is a sectional view of a principal part showing a second embodiment of the present invention, and FIG. 3 is a sectional view showing a third embodiment of the present invention. FIG. 4 is a fragmentary sectional view showing a fourth embodiment of the present invention. FIG. 5 is a fragmentary sectional view showing a fifth embodiment of the present invention. FIG. 6 is a sixth embodiment of the present invention. 7 is a perspective view of a magnetic disk, FIG. 8 is a cross-sectional view of a main part showing a seventh embodiment of the present invention, and FIG. 9 is a cross-sectional view of a main part of a conventional example. 10 ... holding plate, 12 ... substrate, 14, 18 ... insulating film, 16 ... magnetic film, 20 ... protective film, 22 ... minute defect, 24 ... condensation water.

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-55-8690 (JP, A) JP-A-60-258727 (JP, A) JP-A-62-46423 (JP, A)

Claims (4)

(57) [Claims] A protective film is laminated on a substrate via a magnetic film,
At least one of the substrate and the protective film has conductivity, and a layer of an insulating film is formed between at least one of the layers between the conductive member and the magnetic film, and the thickness direction of the insulating film is A magnetic recording medium having an electric resistance of 10 ⁵ to 10 ¹⁰ Ω / cm ^{2 in the above} . 2. The magnetic recording medium according to claim 1, wherein the protective film is made of graphite carbon. 3. The magnetic recording medium according to claim 1, wherein the magnetic film is composed of an alloy mainly composed of Co, Ni and Zr, and the insulating film is composed of an oxide composed mainly of ZrO ₂ or diamond-like carbon. 4. The magnetic recording medium according to claim 1, wherein the protective film is divided into a plurality of regions, and the regions are dispersed and arranged in a discontinuous state.