JPH0628657A - Magnetic disk - Google Patents

Abstract

PURPOSE:To provide a magnetic disk having satisfactory electromagnetic transducing characteristic and excellent corrosion resistance by successively forming a magnetic recording layer, a Cr or Cr-Co alloy layer having a prescribed thickness and a protective film having a prescribed thickness. CONSTITUTION:A Cr or Cr-Co alloy layer having 10-100Angstrom thickness is formed on a magnetic recording layer formed on a nonmagnetic substrate. This Cr or Cr-Co alloy layer acts as a dense passive film to the magnetic recording layer, inhibits pitting corrosion on the surface of the resulting magnetic disk and enhances corrosion resistance. The pref. Cr content of the Cr-Co alloy layer is 15 or more atomic%. A film of carbon, SiO2 or SiN, etc., is then formed as a protective film on the Cr or Cr-Co alloy layer in 90-200Angstrom thickness. Since the protective film is formed, wear resistance is improved and corrosion resistance can be considerably improved while maintaining satisfactory electromagnetic transducing characteristic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of a magnetic disk having a protective film on a magnetic recording layer.

[0002]

2. Description of the Related Art A magnetic disk applied to a hard disk drive device adopting a contact start and stop (CSS) system comes into contact with a magnetic head surface during operation, and therefore wear or damage occurs on the disk surface. Easy to do. In addition, this magnetic disk is likely to corrode depending on the environment to which it is applied and how it is handled.

Therefore, conventionally, a magnetic recording layer, which is a ferromagnetic metal thin film, is formed on a non-magnetic substrate, and a film thickness of 2 is formed on the magnetic recording layer.
Carbon film, SiO ₂ film, SiN of 00-400Å
A magnetic disk provided with a protective film such as a film or a ZrO ₂ film is known.

However, in such a magnetic disk,
In order to realize high-density recording, it is required to reduce the distance between the magnetic disk and the magnetic head during magnetic recording / reproduction, that is, the so-called head flying height. Therefore, it is desirable that the thickness of the protective film can be further reduced.

[0005]

However, it has been found that the above-mentioned magnetic disk has a problem that when the thickness of the protective film is reduced, the corrosion resistance is significantly deteriorated.

In view of the above circumstances, an object of the present invention is to provide a magnetic disk excellent in corrosion resistance even if the thickness of the protective film is reduced.

[0007]

In order to achieve the above object, the present invention provides a magnetic recording layer on a non-magnetic substrate and a Cr layer or C having a thickness of 10 to 100Å on the magnetic recording layer.
A magnetic disk having an r-Co alloy layer and a protective film having a film thickness of 90 to 200Å on the Cr layer or the Cr-Co alloy layer.

[0008]

In the present invention, as the material of the non-magnetic substrate,
A non-magnetic material having rigidity such as non-magnetic metal such as aluminum or its alloy, glass, resin or the like is used.

Next, a hardened layer having high hardness and good machinability is formed on the entire surface of the substrate made of such a material. This hardened layer can be formed by, for example, providing an Ni-P alloy layer or a Ni-Cu-P alloy layer by an electroless plating method, or performing an alumite treatment when using aluminum or its alloy.

Further, the substrate provided with the hardened layer is subjected to polishing processing for flattening the surface thereof, for example, lapping processing or polishing processing. By this flattening polishing process, the substrate surface is made a flat mirror surface.

Then, the surface of the substrate subjected to the flattening polishing process is roughened by the texture process.

After that, an underlayer made of Cr or a Cr alloy is formed on this substrate in order to adjust the magnetic characteristics of the magnetic recording layer.

A magnetic recording layer made of a predetermined ferromagnetic metal thin film is formed on the formed underlayer. Examples of the magnetic recording layer include Co-based, Co-Ni-based, Co-
There are Pt type, Co-Cr-Ta type, and Fe type.

In the present invention, it is important that a Cr layer or a Cr--Co alloy layer having a film thickness of 10 to 100Å is formed on this magnetic recording layer. It is considered that this layer serves as a dense passivation film with respect to the magnetic recording layer and suppresses pits formed on the surface of the magnetic disk to improve the corrosion resistance. If the film thickness is less than 10Å, the above-mentioned action is not sufficiently exhibited, while if it exceeds 100Å, the requirement for reducing the distance between the magnetic disk and the magnetic head, that is, the so-called head flying height, is not satisfied. . The Cr content of the Cr-Co alloy layer is preferably 15 atomic% or more.

A protective film such as a carbon film, a SiO ₂ film, a SiN film and a ZrO ₂ film is formed on the Cr layer or the Cr—Co alloy layer. In the present invention, at this time,
It is also important to set the film thickness to 90 to 200Å. If the film thickness is less than 90Å, the wear resistance of the obtained magnetic disk is deteriorated. On the other hand, if it exceeds 200Å, the requirement for the head flying height is not satisfied.

By thus forming the Cr layer or the Cr-Co alloy layer on the magnetic recording layer, the corrosion resistance is improved, and at the same time, the protective film is formed on the Cr layer to reduce the wear resistance. It is possible to provide a magnetic disk satisfying the requirement for the flying height of the head without causing the above problem.

A lubricating layer such as perfluoroalkyl polyether is further formed on the protective film to obtain the desired magnetic disk.

[0018]

【Example】

Example 1 A Ni—P alloy layer of about 15 μm was formed by an electroless plating method on an aluminum substrate having an outer diameter of 130 mm, an inner diameter of 40 mm and a thickness of 1.9 mm, and then polished to obtain a mirror surface having a surface roughness Ra of about 5 nm. And

The following texture processing was performed on this substrate. That is, while rotating the substrate at 100 to 500 rpm, a polishing tape made by binding alumina abrasive grains having an average particle size of 6 μm on a polyethylene base film was pressed against the substrate surface.

Next, Cr was deposited as a base layer to a thickness of 500 Å by a DC magnetron sputtering method.
At this time, the substrate temperature is 300 ° C. and the Ar gas pressure is 10 mTo.
rr and DC input power were set to 5 W / cm ² .

Further, a Co—Cr—Ta magnetic recording layer having a potential of −150 V with respect to the potential of the sputtering chamber of the substrate was formed on the underlayer to a thickness of 300 μm.

After that, a Cr--Co alloy layer (Cr content 25 atomic%) was formed on the magnetic recording layer to a thickness of 20Å. At this time, the Ar gas pressure was 10 mTorr, the DC input power was 3 W / cm ² , and the film formation time was 2 seconds.

Then, on this Cr-Co alloy layer, a carbon protective layer having a thickness of 100Å was formed under the same conditions as the layer, and a perfluoroalkylpolyether lubricating film was sequentially formed by spin coating.

The magnetic disk thus obtained was subjected to reproduction output measurement and corrosion resistance test. The reproduction output measurement measures the reproduction output when recording with the shortest recording bit length, and the corrosion resistance test uses a magnetic disk at a temperature of 85 ° C.
After left for 1000 hours in a non-condensing environment with a humidity of 80% RH, perform a signal error inspection under the following conditions over the entire surface, measure the number of errors, and perform the same measurement for the magnetic disk that was not left under the corrosive environment. Compared to the number of errors made. That is, (1) evaluation area: 25.0 to 45.4 mm,
(2) Test pitch: 10 μm, (3) Recording frequency:
6.75MHz, (4) Cutoff frequency: 20.3M
Hz, (5) current switching radius: 32.4 mm, (6) recording current (inner / outer circumference): 15/18 mA.

Examples 2 to 6 and Comparative Examples 1 to 4 Cr—Co alloy layers were formed by setting DC power and film forming time as shown in Table 1, and the Cr content and film thickness thereof are shown in Table 1. The same test as in Example 1 was carried out except that the above was carried out.

Conventional Examples 1 and 2 Tests were carried out in the same manner as in Example 1 except that the Cr-Co alloy layer was not provided on the magnetic recording layer and the carbon protective layers were directly formed at 230Å and 350Å.

Table 1 shows the results obtained as described above.

[0028]

[Table 1]

As is clear from the above, the conventional example does not have the Cr layer or the Cr-Co alloy layer, but has the carbon protective layer directly provided, so that the corrosion resistance is not sufficient. On the other hand, in all the examples, although the thickness (sum) of the Cr layer or the Cr-Co alloy layer and the carbon protective layer is smaller than the thickness of the carbon protective layer of the conventional example, the corrosion resistance is significantly improved. In addition, the fluctuation of the reproduction output with respect to the film thickness (sum) is the same as that of the conventional example. Further, in the comparative example, when the thickness of the Cr—Co alloy layer is too thin, the corrosion resistance is insufficient, while when it is too thick, the reproduction output becomes insufficient.

[0030]

As is apparent from the above, according to the present invention, there is provided a magnetic disk whose corrosion resistance is significantly improved while maintaining good electromagnetic conversion characteristics even when the protective film is made thinner. be able to.

Claims (1)

[Claims] 1. A magnetic recording layer on a non-magnetic substrate, and a Cr layer or a Cr- layer having a thickness of 10 to 100Å on the magnetic recording layer.
A magnetic disk comprising a Co alloy layer and a protective film having a film thickness of 90 to 200Å on the Cr layer or the Cr-Co alloy layer.