JPH0250319A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve corrosion resistance, weatherability and lubricity by constituting a protective film consisting of a 1st layer consisting of specific Cr and the 2nd layer consisting of amorphous carbon. CONSTITUTION:The protective film constituted of the 1st layer consisting of the Cr film contg. at least >=1 kinds of boron (B) or carbon (C) and the 2nd layer consisting of the amorphous carbon formed on the front surface side of the 1st layer. The Cr film formed as the 1st layer may be more specifically any of a Cr-B film, Cr-C film and Cr-B-C film. The good corrosion resistance and weatherability are obtd. in this way and the sufficient protection of the magnetic film thickness is assured. The magnetic recording medium having the excellent durability is thus obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic recording medium having a magnetic thin film and a protective film formed on the surface of the magnetic thin film, and particularly relates to a disk in which the corrosion resistance of the protective film is improved. This relates to magnetic recording media of the form.

[Prior Art] In recent years, research and development of magnetic recording media having alloy magnetic thin films with high recording density has been greatly promoted.

One of them is to form a magnetic thin film layer on the surface of the substrate,
Furthermore, some have a protective film provided thereon.

Osmium and ruthenium are used as this protective film.

From metals such as iridium, manganese, and tungsten, various oxides, nitrides, or carbides such as silicon oxide, titanium oxide, tantalum oxide, and hafnium oxide, boron, carbon, alloys of carbon and boron, polysilicate, diamond structure carbon, etc. It is known to use a film of
1106).

[Problems to be Solved by the Invention] Among these protective films, carbon is often used because it has particularly excellent lubricity. but.

This carbon protective film has a relatively high property of transmitting H, O, 08, etc., and this makes it highly resistant to corrosion of the magnetic film layer.

There was a problem that the original protective effect of increasing weather resistance was somewhat lacking.

In addition, protective films made of materials other than carbon have a problem in that, although they have somewhat superior corrosion resistance and weather resistance, their lubricity is considerably inferior to that of carbon.

[Means for Solving the Problem] As a result of extensive research into the protective film formed on the magnetic thin film of a magnetic recording medium, the present inventors found that boron (B) or carbon (C) was used as the protective film. A first layer made of Cr containing at least one of these and a second layer made of amorphous carbon formed on this first layer has corrosion resistance,
It has been found that both weather resistance and lubricity are extremely excellent.

The present invention has been made based on this knowledge, and a magnetic thin film is formed on the surface of the substrate.

In the magnetic recording medium in which a protective film is formed on the surface of the magnetic thin film, the protective film layer includes a first layer made of Cr containing at least one of B or C, and a first layer formed on the surface side of the first layer. This magnetic recording medium is characterized by comprising a second layer made of amorphous carbon.

In the present invention, aluminum, an aluminum alloy containing several percent of magnesium, or a titanium alloy can be used as the substrate, but it is preferable to use an aluminum alloy because it is lightweight, inexpensive, and easy to process. . Also, in recent years.

Ceramic substrates are attracting attention, but the present invention may use such ceramic substrates or even glass substrates.

The substrate used is one whose surface has been finished to make it flat. It is preferable to provide a base layer such as alumite or N1-P on this substrate to prevent deformation of the disk surface due to head crashes. However, in the case of a ceramic substrate, such treatment is not necessarily necessary. .

When the substrate is made of aluminum or an aluminum alloy, an alumite layer can be formed on the surface of the substrate by anodizing, and this can be used as a base layer.In the present invention, the thickness of the alumite layer is not particularly limited. It is usually several micrometers to several tens of micrometers, for example, about 10 micrometers thick.

The N1-P underlayer is usually formed by electroless plating and has a thickness of about 10 to 100 μm. Further, it is preferable that the surface of these alumite underlayers and N1-P underlayers be polished before forming a magnetic thin film thereon.

In the present invention, a magnetic thin film is formed on the base film. As this magnetic thin film, an alloy magnetic thin film or an oxide magnetic thin film can be used.

Co, Go-Ni, and G are used as alloy magnetic thin films.

-Ni-Pt, Go-Ni-P, Co-Pt, etc. can be used. Examples of the oxide-based magnetic thin film include γ-Fe, 03, and the like.

These magnetic thin films can be formed by a conventional gas phase plating method such as sputtering or a liquid phase plating method as described in Japanese Patent Application Laid-open No. 56-41524. Note that the above composition and manufacturing method are merely examples, and the present invention is of course not limited to the above composition and manufacturing method. A protective film is formed of a first layer made of a Cr film containing at least one of the above, and a second layer made of amorphous carbon formed on the surface side of the first layer.

Specifically, the Cr film formed as the first layer is Cr-
B system film, Cr-C system 11. Any cr-B-C type film may be used.

This layer made of a Cr film containing one or more types of B or C has better corrosion resistance and weather resistance than a layer made of amorphous carbon. Further, the Cr film containing B or C is hard and has the effect of increasing the C8S resistance of the protective film.

In the present invention, the protective film has a thickness (first layer and second layer).
If the total film thickness exceeds 1000, the formation time becomes longer and the distance between the magnetic head and the magnetic thin film becomes larger, which deteriorates the electromagnetic conversion characteristics of the disk. Naturally, if it is too thin, it will not function as a protective film. Therefore, it is particularly preferable that the film thickness is 300 mm.
~1000 people. Note that the thickness of the first layer is 1
This is because if the thickness is thinner than 100, the effect of improving corrosion resistance and weather resistance will be reduced. On the other hand, if there are more than 300 people, corrosion resistance,
Although it is excellent in terms of weather resistance, as mentioned above, it is preferable that the overall thickness of the protective film be 1000 Å or less, so the second layer (amorphous carbon layer)
There arises a need to reduce the thickness of the material. Also, the second layer.

It is preferable to set the number to about 200 to 700; if it is thinner than 200, the lubricity improvement effect will be small;
This is because if the thickness exceeds that of a person, it may be necessary to limit the thickness of the first layer.

Further, in the present invention, B in the first layer Cr film is
Alternatively, the content of C is preferably 5 to 30 at%, and when it is in this composition range, B or C exhibits an effect as a metallizing element and produces excellent amorphous Cr.
Forms a film. Such a Cr film is superior in density and hardness to a Cr film that does not contain B or C, and not only has excellent corrosion resistance and weather resistance, but also has C8 resistance.
It also has the advantage of increasing S properties.

In the present invention, a lubricant made of various organic substances can also be further applied on the protective film.

[Example code] Hereinafter, the present invention will be explained in detail using specific examples.

In addition, in the examples described below.

Although magnetron R, F, and sputtering devices were used, it goes without saying that the effects of the present invention can be obtained by ion beam sputtering, etc., which can be said to be similar in terms of ion technology.

(Example 1) 3,000 Cr base films were deposited on a glass substrate using a flat plate magnetron r, f and sputtering device under the following conditions.
A Go-Ni thin film was immediately formed.

Initial pumping <3 X 10 Torr Target composition 30 atomic percent Ni, balance C.

Magnetic thin film 500 people Thin film formation speed 100 people/+*in substrate temperature
200°C After that, under the same conditions as above, the components and composition were changed by placing B and C chips on a Cr target with a purity of 99% or more, and a first layer of protective film mainly made of Cr was formed. In addition, a protective film of the amorphous carbon second layer was formed under the same conditions as above except that the Ar gas pressure was 5 mTorr and the thin film formation rate was 50 people/in.

The composition of the protective layer and the film thickness of each protective layer at this time are as shown in Table 1. After that, the sample was immersed in pure water with a specific resistance of 3 MΩ・C (25°C) for one week.
Corrosion resistance and weather resistance were tested by determining the reduction in saturation magnetic flux density (Br) (ΔBr). The results are also shown in Table 1.

(Comparative Example 1) A Cr film, a Cr-Ni film, and a C film were sequentially formed under the same sputtering conditions as in Example 1 to produce a protective film. This film was tested for corrosion resistance, weather resistance, etc. in the same manner as in Example 1. The results are shown in Table 1 as a comparative example.

Table 1 It is clear from Table 1 that the magnetic recording medium according to the present invention has superior corrosion resistance and weather resistance compared to the comparative example.

[Effects] As detailed above, the protective film of the magnetic recording medium of the present invention has the following effects:
Since it has excellent corrosion resistance and weather resistance, the magnetic film layer can be sufficiently protected, and a magnetic recording medium with excellent durability can be realized.

Claims (3)

[Claims] (1) In a magnetic recording medium in which a magnetic thin film is formed on the plate surface of a substrate and a protective film layer is formed on the surface of this magnetic thin film, the protective film layer contains at least one kind of boron or carbon. A magnetic recording medium comprising a first layer made of a Cr film containing the above, and a second layer made of amorphous carbon formed on the surface side of the first layer. (2) The thickness of the first layer in the above protective film layer is 100 to 3
00 Å, and the second layer has a thickness of 200 to 700 Å. (3) The magnetic recording according to any one of claims (1) and (2), characterized in that the content of boron or carbon in the Cr film constituting the first layer is 5 to 30 atomic % or less. Medium.