JPS62114119A - Magnetic disk - Google Patents

Abstract

PURPOSE:To obtain a magnetic disk which corrodes less and has an excellent shelf life and reliability by forming an insulator coating layer having prescribed specific resistance on a substrate and forming a thin magnetic metallic film thereon. CONSTITUTION:The insulator coating layer 3 is provided on the substrate 1 consisting of Al, Al alloy such as Al-Mg, Ti alloy, etc., and the thin magnetic metallic film 2 is formed thereon. An insulator such as SiO2, Al2O3 or Ta2O3 having >=10<11>OMEGA.cm specific resistance is used as the material of the layer 3. The surface of the substrate 1 may be oxidized and the alumite layer may be used as the insulator coating layer 3 if the substrate consists of the Al alloy material. The layer 3 is preferably provided in such a manner as to expose part of the substrate 1 in order to prevent electrostatic noise. The contact of the metallic materials with each other is eliminated and the progression of the electrical corrosion is suppressed by providing the insulation coating layer 3 between the substrate 1 and the thin magnetic metallic film 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic disk used as a storage medium in a magnetic storage device such as a magnetic disk device.

[Summary of the invention]

The present invention provides a magnetic disk having a metal magnetic thin film as a magnetic layer, with a specific resistance of 1011Ω between the substrate and the metal magnetic thin film.
・By forming the second insulating coating layer described below, the present invention aims to provide a magnetic disk with excellent corrosion resistance.

[Conventional technology]

For example, disk-shaped magnetic disks that can be randomly accessed are widely used as storage media in computers, etc., and among them, they have excellent responsiveness, large storage capacity, good storage stability, and reliability. Because of the high resistance, magnetic disks whose substrates are made of hard materials such as An-Mg alloy plates, so-called hard disks, have come to be used as fixed disks or external disks.

The hard disk has, for example, a magnetic layer involved in recording and reproducing formed on an An alloy substrate, and rotates at high speed to record and reproduce information on a large number of concentric tracks.

On the other hand, it goes without saying that high-density recording and short-wavelength recording are progressing in this type of magnetic disk as well. , magnetic disks using this as a magnetic layer are being developed.

Magnetic disks with such metal magnetic thin films as magnetic layers do not need to mix an organic binder, which is a non-magnetic material, so the packing density of the magnetic material can be dramatically increased, and recording demagnetization and thickness loss are reduced. It has many excellent properties such as being extremely small.

[Problem that the invention seeks to solve]

By the way, in the above-mentioned magnetic disk, for example, AA-
When a metal magnetic thin film is formed as a magnetic layer on a metal substrate such as an Mg alloy substrate, a contact potential is generated between the substrate and the metal magnetic thin film, which promotes electrochemical corrosion under high humidity. Ru. Of course, corrosion phenomena are not only electrochemical (as mentioned above), but there are also those that proceed due to pure chemical reactions, but the use of rust preventives is being considered to prevent corrosion caused by these chemical reactions. However, in order to prevent electrochemical corrosion, it is necessary to use materials that do not generate contact potential between the substrate material and the metal magnetic thin film material, or to make the substrate itself an insulator. .

Here, the condition listed in (2) cannot be realized because a contact potential will occur unless the substrate material and the metal magnetic thin film material are of the same metal. On the other hand, the conditions listed in (2) can be realized by using an insulator such as glass, plastic, or ceramics for the substrate, but this is not realistic from the viewpoints of performance, price, etc.

Therefore, in view of the conventional situation, the present invention provides Aβ-Mg
An object of the present invention is to provide a magnetic disk that exhibits less corrosion and excellent storage stability and reliability even when a general-purpose substrate such as an alloy substrate is used and the magnetic layer is a metal magnetic thin film.

[Means for solving problems]

In order to achieve this object, the magnetic disk of the present invention is characterized in that an insulating coating layer having a resistivity of IQ Ω·C111 or more is formed on a substrate, and a metal magnetic thin film is formed on this insulating coating layer.

A magnetic disk to which the present invention is applied includes Aβ as a substrate,
An aluminum alloy such as AJ-Mg or a metal material such as a titanium alloy is used.

The material of the metal magnetic thin film formed as a magnetic layer on the substrate includes metals such as Fe + Co + Ni, Co-N1 alloy, and Co-Pt alloy.

Co-Ni-Pt alloy, Fe-Co alloy, Fe-Ni alloy, Fe-Co-N1 alloy, Fe-Co-B alloy, Co
-N1-Fe-B alloy, Co-Cr alloy, or Cr, Aj! Any ferromagnetic metal material that is normally used in this type of magnetic disk may be used, such as those containing metals such as.

The above-mentioned metallic magnetic Tit film is usually deposited and formed by a vacuum thin film forming technique such as a vacuum evaporation method, a sputtering method, or an ion blating method.

In any of the above methods, Bi, Sb, Pb, Sn, Ga, and In are formed on the substrate in advance.

To efficiently manufacture a magnetic disk with excellent in-plane method by first depositing a base metal layer such as Cd, Ge, Si, or Ti, and then depositing the film in a direction perpendicular to the substrate surface. I can do it.

In the present invention, as shown in FIG. 1, an insulator coating layer (3) is provided between the substrate (1) and the metal magnetic thin film (2),
Metal materials are prevented from coming into contact with each other.

The material of the insulator coating layer (3) has a specific resistance of IQ
An insulator with a resistance of IIΩ・(2) or more is used, for example, Si
Ox, Al1203. T a 20s etc. can be used. These insulating materials can be easily deposited on the surface of the substrate (1) by methods such as sputtering and vacuum deposition. Alternatively, when the substrate (1) is formed of an A1 alloy material, the surface thereof may be oxidized to provide an alumite layer, and this may be used as the insulator coating layer (3).

If the specific resistance of the insulator coating layer (3) is less than IQIIΩ·0, the desired effect cannot be expected.

The insulating coating layer (3) may be formed on the entire surface of the substrate (1), but if the substrate (1) is completely covered, electrostatic noise will occur, so the insulating coating layer (3) may be made of a metal material. substrate(
It is desirable that part of 1) is exposed. For example, the insulator coating layer (3) is placed so that the inner peripheral part of the substrate (1) is exposed.
The above-mentioned electrostatic noise can be prevented by covering the disc with a disc so that conduction can be established through the inner circumferential part when the disc drive is mounted on the disc drive.

[Effect]

By providing an insulator coating layer between the substrate and the metal magnetic thin film, there is no contact between the metal materials, and the generation of contact potential is suppressed. Therefore, progress of electrochemical corrosion is suppressed.

〔Example〕

Hereinafter, specific examples of the present invention will be described, but the present invention is not limited to these examples.

Example 1゜AJ! - Alumite layer on the surface of the Mg alloy plate (specific resistance ≦10
After coating the alumite layer with 12 μm of Ω·Cl11), the alumite layer was mirror-polished to a thickness of 10 μm, and this was used as a substrate.

After a bismuth underlayer with a thickness of 100 layers was deposited on the substrate, a film 1'! was formed under the following sputtering conditions. 500 cobalt-nickel thin films (Ni35
atomic %) was formed as a magnetic layer.

Sputtering conditions Argon gas pressure 5 x 10-”Torr
Input RF power 1. OKW substrate temperature
150℃ target diameter
100wnφ target-substrate distance 95
TsuruNext, a film thickness of 300 mm was deposited on this cobalt-nickel thin film.
A sample disk was prepared by applying a human carbon protective film by vacuum evaporation.

Example 2゜A7 with mirror finish! A 5 μm film of SiO (specific resistance≦10+2Ω·C) was sputtered on the surface of the -Mg alloy plate, and this was used as a substrate.

A sample disk was produced in the same manner as in Example 1 except for the above.

Example 3゜Mirror-finished Am! -Al t0 on the surface of the Mg alloy plate
3 films (specific resistance≦1013Ω·Cl11) were sputtered to a thickness of 4 μm, and this was used as a substrate. A sample disk was prepared in the same manner as in Example 1 except for 1 and 1.

Comparative example.

After coating the surface of the mirror-finished Af-Mg alloy plate with a 15 μm N1-P layer by electroless plating, it was mirror-polished and
The 1-P layer had a thickness of 12 μm and was used as a substrate.

A sample disk was produced in the same manner as in Example 1 except for the above.

For the sample disks produced according to the above examples and comparative examples, after holding them in an atmosphere at a temperature of 60°C and a relative humidity of 90% for one week, the amount of residual magnetization φ,' was measured using a vibrating sample magnetometer (VSM). and the initial residual magnetization φ, °
We investigated the changes since.

As a guideline for corrosion resistance, the rate of change in residual magnetization Δφ, [-(
φ, ゛-φ,'')/φr''X100%] were compared. The results are shown in Table 1. Note that three sample disks were produced for each sample disk, and the average values thereof were compared.

Table 1 Next, changes in the number of defects on electromagnetic conversion signals of missing pulses and extra pulses on the sample disk surface after the accelerated test were investigated. i.e. temperature 50℃, relative humidity 80%
After being kept in the atmosphere for one week, the increase in the number of defects from the initial number was examined. The results are shown in Table 2. Note that in measuring the number of defects, the average of three sample disks was also taken.

Table 2 From these test results, it was confirmed that the corrosion resistance was improved by providing the insulating coating layer.

〔Effect of the invention〕

As is clear from the above description, in the magnetic disk of the present invention, an insulating coating layer having a resistivity of 1Ω·0 or more in 10 divisions is provided between the substrate made of a metal material and the metal magnetic thin film serving as the magnetic layer. Since it is formed and electrically insulated, the generation of contact potential due to contact between metals is suppressed, and the progress of electrochemical corrosion is suppressed. Therefore, it has excellent corrosion resistance,
It becomes possible to provide a magnetic disk with excellent storage stability and reliability.

Further, according to the present invention, a general-purpose Al1-Mg alloy substrate or the like can be used, which is advantageous in terms of performance, cost, etc.

[Brief explanation of drawings]

FIG. 2 is a schematic enlarged sectional view of the main part showing the structure of a magnetic disk to which the present invention is applied. 1...Substrate 2...Metal magnetic thin film 3...Insulator coating layer

Claims (1)

[Claims] A magnetic disk characterized in that an insulating coating layer having a specific resistance of 10^1^1 Ω·cm or more is formed on a substrate, and a metal magnetic thin film is formed on the insulating coating layer.