JPS61172219A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic disk, etc. having excellent resistance to corrosion and weather and which is also highly lubricative by forming a protective layer contg. chromium oxide and silicon oxide or germanium oxide on a magnetic thin film formed on a substrate. CONSTITUTION:A magnetic layer of a ferromagnetic metallic thin film, ferromagnetic oxide, etc. is formed on an Al (alloy) substrate, a ceramic substrate, etc., and then a protective film consisting of chromium oxide and silicon oxide (one between SiO2 and SiO or their mixture) or chromium oxide and germanium oxide (one between SiO2 and SiO or their mixture) or chromium oxide, silicon oxide and germanium oxide is formed on the magnetic layer. Chromium oxide enhances the hardness, and silicon oxide and germanium oxide have excellent resistance to corrosion and weather and considerably high lubricity. As the chromium oxide content increases, the lubricity decreases. Consequently, the chromium oxide content is regulated to 15%, the thickness of the protective film is controlled to 50-1,000Angstrom to control the spacing loss to a low value, and a magnetic recording medium having excellent CSS resistant characteristic, etc. and good durability is obtained.

Description

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

[Prior art 1] Research and development of magnetic recording media having alloy magnetic thin films with high recording density has been greatly promoted in recent years. Some have a protective film on them.

As this protective film, metals such as osmium, ruthenium, iridium, manganese, and tungsten, oxides such as silicon oxide, titanium oxide, tantalum oxide, and hafnium oxide,
It is known to use films made of various nitrides, carbides, boron, carbon, alloys of carbon and boron, polysilicic acid, and diamond structure carbon (Japanese Patent Laid-Open No. 59-61106).

[Problems to be Solved by the Invention] Among these protective films, carbon is often used because of its excellent lubricity.
It has a relatively high property of transmitting 2O, 02, etc., and therefore has a problem in that it lacks the original protective effect of increasing the corrosion resistance and weather resistance of the magnetic film layer.

In addition, a protective film made of a material other than carbon as described in item 2 has a problem in that although it has somewhat excellent corrosion resistance and weather resistance, its lubricity is considerably inferior to that of carbon.

[Means for Solving the Problems 1] As a result of extensive research into the protective film formed on the magnetic thin film of a magnetic recording medium, the inventors found that chromium oxide, silicon oxide, and/or oxidized It has been found that materials containing germanium have extremely excellent corrosion resistance and weather resistance, and also have considerably excellent lubricity.

The present invention has been made based on this knowledge, and provides a magnetic recording medium in which a magnetic thin film is formed on the plate surface -L of a substrate, and a protective film layer is formed on the surface of this magnetic thin film. The protective film layer is made of chromium oxide, e.g. Cr2O3
and silicon oxide (SiO.

1 and SiO (or a mixture thereof) and/or germanium butyride (G e O 2 and GeO or a mixture thereof).

The present invention will be explained in more detail below.

In the present invention, aluminum, an aluminum alloy containing several percent of magnesium, a titanium alloy, and the like are used as the substrate, and an aluminum alloy is preferable because it is lightweight, inexpensive, and easy to process. Note that although ceramic substrates have attracted attention in recent years, the present invention can also use such ceramic substrates and glass substrates.

The substrate used is one that has been finished so that its surface is flat. A hard underlayer of alumite, Ni--P, or the like is provided on this substrate to improve surface accuracy and to prevent deformation of the disk surface due to head crashes. (Note that this is not necessarily necessary in the case of a ceramic substrate.) When the substrate is made of aluminum or an aluminum alloy, an alumite layer can be formed as a base layer on the surface of the substrate by anodizing. The thickness of the alumite layer is not particularly limited, but is usually about several pm to several tens of gm, for example about 10 #Lm.

The N1-P underlayer is usually formed by electroless plating, and its thickness is approximately 10 to 1100 p. Further, it is preferable that the surface of these alumite underlayers and N1-P underlayers be polished before forming a magnetic thin film thereon.

A magnetic thin film is formed on the underlayer.

As this magnetic thin film, an alloy magnetic thin film or an oxide-based magnetic thin film can be used, but as an alloy magnetic thin film, C
o, Co-Ni, Co-Ni-Pt, Co-N1-P
, Co--Pt type, etc. can be used. Alternatively, a part of Co or Ni may be replaced with Fe. Examples of the oxide-based magnetic thin film include γ-Fe, 03, and the like.

These magnetic thin films can be formed by ordinary vapor phase plating methods such as sputtering or liquid phase plating methods as described in Japanese Patent Laid-Open No. 56-41524.

In addition, in the present invention, the above composition system and manufacturing method are as follows:
- This is an example and is not particularly limited to these.

A protective film made of chromium oxide, silicon oxide, and/or germanium oxide is formed on the magnetic thin film.

Specifically, there are three types: chromium oxide and silicon oxide, chromium oxide and germanium oxide, and chromium oxide, silicon oxide, and germanium oxide. The silicon oxide and germanium oxide have better corrosion resistance and weather resistance than the carbon, and also have considerably better lubricity.

Chromium oxide is hard and increases the wear resistance of the protective film. Note that since chromium oxide itself does not have lubricity, the content is preferably 15 mol% or less of the entire protective film so as not to reduce the lubricity of the protective film.

If the thickness of this protective film exceeds 1000 Å, 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. Also,
Naturally, if it is too thin, it will not function as a protective film. The preferred film thickness is 50 to 1000 Å, particularly preferred film thickness is 100 to 800 Å, especially 200 to 6
It is 00A. Furthermore, a lubricant made of various organic substances can also be applied onto this protective film.

Effect 1 A protective film formed on a magnetic thin film containing chromium oxide and silicon oxide and/or germanium oxide has excellent corrosion resistance and weather resistance, while silicon oxide, silicon oxide, and/or germanium oxide have excellent corrosion resistance and weather resistance. This increases the hardness of the entire protective film. Therefore, the magnetic recording medium of the present invention has corrosion resistance,
It has excellent weather resistance, excellent C3S resistance, etc., and is highly practical.

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

Although the embodiments described below are based on r, f, and magnetron sputtering devices, it goes without saying that the effects of the present invention can also be obtained by ion beam sputtering, etc., which can be said to be similar in terms of ion technology.

Example 1 Aluminum alloy substrate containing 4% magnesium (size: diameter 130 mm, inner diameter 40 mm, thickness 1.9 mm)
), the surface was lathed to make it flat. Next, an N1-P layer was formed on the processed substrate to a thickness of 25 gm by electroless plating, and after polishing one side by approximately 51 Lm, scratches with a depth of 0.05 to 0.171 m were randomly added ( Textured) and finished with mirror polish.

Next, using a r, f, flat plate magnet]・ron sputtering device,
A 4000A Cr film was formed, and then a Co--Ni thin film was immediately formed under the following conditions without exposing it to the air.

Initial exhaust 2 X I O”-6To
rr Atmosphere during sputtering Ar Atmospheric pressure during sputtering 12 mTorr Input power ILcw Target composition Ni 20 at% balance C
O Pole spacing 108mm Film thickness of magnetic thin film 500A Thin film formation rate 200A/min Substrate temperature 200°C Then, the target was heated to C
A chromium oxide-silicon oxide based protective film was formed at 40 OA by using the same method as above except that the argon atmosphere contained 2 to 3% oxygen (in partial pressure). A magnetic recording medium was formed by sputtering to a certain thickness. A #CSS property test of this magnetic recording medium was conducted. This test was conducted using a 5" diameter disk with a protective film attached to a 5" diameter disk drive.

The head used was an Mn-Zn Winchester type, and the head flying height at the inner circumference R = = 50 mm was set to 0.45.
A test was conducted at this point with the engine speed set at 3,600 rpm. The C3S cycle was as shown in FIG.

The life of the C8S resistance was defined as the point at which the reproduction output decreased by 10% compared to the starting point or the point at which the number of errors increased by even one.

Table 1 shows the test results.

Example 2 The target composition and sputtering time were variously changed, and the protective film material and protective film thickness were changed as shown in Table 1.
A magnetic recording medium was produced in the same manner as in Example 1.

The results of these fI#C5S tests are shown in Table 1.

Comparative Example 1 As a protective film, 5i02. Magnetic recording media were prepared in the same manner as in Example 1, except that osmium, silicon nitride, silicon carbide, and diamond structure carbon were used, and CSS resistance tests were conducted in the same manner.

The results are shown in Table 1.

From Table 1, it is clear that in the magnetic recording medium according to the present invention, the protective film has high lubricity.

Note that C3S resistance tests were similarly attempted for osmium, silicon nitride, silicon carbide, and diamond-structured carbon protective films with a film thickness of 40 OA, but all of them had lifetimes of IOK times or less. In addition, 1 fluorocarbon lubricant was added.
Even if it was about 00A, it was under rotation to 20A. Normally resistant to C3
Since the S property is required to be between 10K times and 20 times, these protective films are not sufficient in terms of C5S resistance when looking at safety.

The magnetic recording media according to the above Examples and Comparative Examples were tested for their corrosion resistance and weather resistance.

In this test, the sample (magnetic recording medium) was
The measurement was performed by immersing the sample in pure water at 25° C. for one week and determining the amount of decrease (ΔBr) in the residual magnetic flux density (Br). The results are shown in Table 2.

Table 2 It is clear from Table 2 that the magnetic recording medium according to the present invention has excellent corrosion resistance and weather resistance.

[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 layer can be sufficiently protected, and the magnetic recording medium has excellent durability.

Moreover, this protective film has high lubricity and C5S resistance, and is excellent in practicality.

[Brief explanation of drawings]

FIG. 1 shows the rotational characteristics of a drive for testing C8S resistance.

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 is made of chromium oxide, silicon oxide and/or or germanium oxide. (2) The magnetic recording medium according to claim 1, wherein the content of chromium oxide in the protective film layer is 15 mol% or less. (3) The magnetic recording medium according to claim 1 or 2, wherein the protective film layer has a thickness of 50 to 1000 Å.