JPS61222024A - Magnetic disk - Google Patents

Abstract

PURPOSE:To improve running property and durability as well as corrosion resistance by forming a carbon protective film on a thin magnetic metallic film and setting the contact angle of the carbon protective film surface with water at a specific value or above. CONSTITUTION:The thin metallic film is formed on a substrate and the carbon protective film is formed on the thin metallic film. The carbon protective film is subjected to a bombardment treatment so that the contact angle with water is made >=75 deg.. The contact angle with the water is an index for the affinity of the carbon protective film with the water and the affinity with the water is lower as the contact angle is larger. The corrosion of the thin magnetic metallic film is effectively prevented if the contact angle of the carbon protec tive film with the water is >=75 deg.. The running property and durability are thus improved and the excellent corrosion resistance is provided as well.

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.

[Conventional technology]

For example, disc-shaped magnetic disks that can be randomly accessed are widely used as storage media in computers, etc., and are particularly reliable due to their excellent responsiveness, large storage capacity, good storage stability, and reliability. Because of their high performance, magnetic disks whose substrates are made of hard materials such as A1 alloy plates, glass plates, plastic plates, etc., so-called hard disks, have come to be used as fixed disks or external disks.

The hard disk has, for example, an A4 alloy substrate on which a magnetic layer involved in recording and reproduction is formed, and rotates at high speed to record and reproduce information on a large number of concentric tracks.

By the way, when performing recording and reproduction on the above-mentioned hard disk, after the magnetic head and the magnetic layer surface are mounted in contact with each other at the start of operation, the distance between the head and the magnetic layer surface is established by applying a predetermined rotation to the hard disk. The CSS method (which forms a minute air layer in the air and performs recording and playback in this state)
The contact start/stop method is generally used.

In such a C8S system, the magnetic head is in frictional contact with the magnetic layer surface at the start and end of operation, and the frictional force generated between the head and the magnetic disk causes wear on the magnetic head and magnetic disk. Become. Or, if there is dust or peeled matter from the magnetic layer on the magnetic head,
Head crashes (falling of the magnetic head) are more likely to occur, and the magnetic head may suddenly come into contact with the magnetic disk during recording and playback due to head jumping, etc., which can cause large shocks to be applied to the magnetic disk. It also causes damage to disks and magnetic heads.

In particular, a method in which the magnetic layer is formed by thinning an alloy such as Co-Ni using a vacuum thin film forming technique such as vacuum evaporation or sputtering, or a method in which an alloy such as Co-N1-P is formed into a thin film by a wet method such as electroless plating. This tendency is remarkable in the case of a continuous thin film formed by et al.

Deterioration of durability caused by such sliding contact between the magnetic disk and the magnetic head is not desirable because it causes noise, and an impact on the magnetic disk can cause damage to the magnetic head or disk surface. This impedes good recording and playback.

In addition, since the magnetic layer of the above-mentioned magnetic disk is made of a continuous thin film of ferromagnetic metal, the surface of the magnetic layer tends to corrode during storage, especially if it is left in high temperature or high humidity conditions. Therefore, there is a problem that the magnetic properties deteriorate over time.

Conventionally, therefore, it has been considered to form a carbon protective film on the surface of the metal magnetic thin film of the above-mentioned magnetic disk to improve the durability of this magnetic disk, but simply forming a carbon protective film will not improve the corrosion resistance. The improvement cannot be said to be sufficient, and further improvement is desired.

[Problem that the invention seeks to solve]

In view of this situation, an object of the present invention is to provide a magnetic disk that has excellent runnability and durability as well as excellent corrosion resistance.

[Means for solving problems]

As a result of intensive research to achieve the above-mentioned objectives, the present inventors have found that by setting the contact angle of the surface of the carbon protective film to water within a predetermined range, the corrosion resistance of the metal magnetic thin film can be greatly improved. The present invention was completed by discovering that it is possible to improve running performance and durability by forming this carbon protective film. The present invention is characterized in that a carbon protective film having a surface contact angle with water of 75° or more is formed on the metal magnetic thin film.

The magnetic disk to which the present invention is applied has a continuous film of ferromagnetic metal as a magnetic layer on a disk substrate, and the material of the disk substrate may be a light alloy such as an aluminum alloy or a titanium alloy, Thermoplastic resins such as polystyrene and ABS resin, ceramics such as alumina glass,
Single crystal silicon etc. can be used.

Here, when a relatively soft material is used as the disk substrate, it is preferable to form a nonmagnetic metal underlayer to harden the surface. The material of the non-magnetic metal underlayer is N1-P alloy + Cu +
Cr t Z n , stainless steel, etc. are preferable. These are deposited on the surface of the substrate by methods such as plating, sputtering, and vapor deposition to a film thickness of about 4 to 20 μm. For example, A
When N1-P plating is applied to the surface of a l-Mg alloy substrate, its hardness becomes approximately 400, and the magnetic layer formed on this substrate has excellent magnetic properties.

In addition, the above magnetic layer can be formed by plating or sputtering.

It is formed as a continuous film using techniques such as vacuum evaporation.

For example, a metal magnetic thin film is formed as a magnetic layer by plating Go-P, Go-Ni-P, or the like.

Alternatively, a vacuum thin film forming technique such as a vacuum evaporation method, an ion blating method, or a sputtering method may be used.

In the vacuum evaporation method described above, a ferromagnetic metal material is evaporated by resistance heating, high frequency heating, electron beam heating, etc. under a vacuum of 10-' to 10-' Torr, and the evaporated metal (
ferromagnetic metal material), and is roughly divided into oblique deposition method and vertical deposition method. The above oblique evaporation method is
In order to obtain a high coercive force, the above-mentioned ferromagnetic metal material is deposited obliquely on the substrate, and in order to obtain a higher coercive force, the above-mentioned ferromagnetic metal material is deposited in an oxygen atmosphere.

In the above-mentioned vertical deposition method, Bt, sb,
pb, Sn, Ga, In, Cd, Ge.

St,Tj! The above-mentioned ferromagnetic metal material is vertically deposited on the underlying metal layer.

The above ion blating method is also a type of vacuum evaporation method, and D
C glow discharge, RF Glow discharge is caused to evaporate the ferromagnetic metal material on the disk during discharge.

The above sputtering method involves causing glow discharge in an atmosphere mainly composed of argon gas at 101 to 10 Torr, and using the generated argon gas ions to knock out atoms on the target surface. 2-pole, 3-pole sputtering method, high frequency sputtering method,
Alternatively, there is a magnetron spunter method using magnetron discharge.

In the case of this sputtering method, Cr or W is used.

A base film such as V may be formed in advance.

In any of the above methods, Bi, Sb, Pb, Sn, Ga, and In are preliminarily deposited on the substrate.

By pre-depositing a base metal layer such as Cd, Ge, St, T1, etc., and depositing the film in a direction perpendicular to the substrate surface, excellent magnetic properties can be obtained in an in-plane manner without magnetic anisotropy orientation. It can be a disc.

When forming a metal magnetic thin film using such vacuum thin film forming technology, the ferromagnetic metal materials used include Fe,
In addition to metals such as Co and Ni, C.

-Ni alloy, Co-Pt alloy, Co-Ni-Pt alloy +
Fe-Co alloy, Fe-Ni alloy, Fe-Co-Ni
Gold alloy Fe Co-B alloy, Co-N1-Fe
-B alloy, Co-Cr alloy, or these with Cr, A1
Examples include those containing metals such as. In particular, Co
When a -Cr alloy is used, a perpendicularly magnetized film is formed.

The thickness of the magnetic layer formed by such a method is 0.
It is about 0.04 to 1 μm.

A carbon protective film is formed on the metal magnetic thin film.

The carbon protective film has excellent lubricity, corrosion resistance, etc., and is usually formed by a method such as a vacuum deposition method or a sputtering method.

For example, in the case of vacuum evaporation, the pressure is 5 x 10-5
The conditions may be as long as the degree of vacuum is Torr or less and the substrate temperature is 50 to 250° C., and the heating method may be an electron beam heating method, a resistance heating method, an induction heating method, an arc discharge method, or the like. Here, if the substrate temperature is too high, problems such as crystallization of the Ni--P plating layer formed as a base film on the substrate surface may occur.

In addition, when using the sputtering method, an inert gas such as Ar is introduced and the pressure is
Under the conditions of vacuum degree of RR and substrate temperature of 50 to 250°C, using a carbon plate (thickness of about 1 to 4 fi) as a target, RF power of 1 to 10 Kw or DC power of 500 w-1
It is sufficient to apply 0Kw.

The carbon protective film may have any structure such as graphite, diamond, or rad, or may be a mixed layer of these.

In addition, it is preferable that the film thickness of this carbon protective film falls within the range of 100 to 800 people.

What is important in the present invention is that the contact angle of the surface of the carbon protective film with water is set to 75° or more.

This contact angle with water is an index of the affinity of the carbon protective film with water, and it can be said that the larger the contact angle, the lower the affinity with water. According to experiments conducted in the present invention, it has been found that if the contact angle of the carbon protective film with water is 75° or more, it is effective in preventing metal magnetic thin films/four meals.

An example of a method for controlling the contact angle of the surface of the carbon protective film with respect to water is bombardment treatment.

The above-mentioned bombardment treatment is a process in which a physicochemical surface treatment is applied to the surface of the carbon protective film, such as dry etching by irradiating the surface of the carbon protective film with gas ions. The contact angle of the membrane surface to water can be increased.

[Effect]

By setting the contact angle of the surface of the carbon protective film to water at 75'' or more in this way, the affinity of the carbon protective film to water is reduced, and corrosion of the metal magnetic thin film is prevented.

〔Example〕

Example First, an Al-Mg substrate (thickness about 1.5 mm, outer diameter 95 wm) was prepared.
, inner diameter 25 mm, average surface roughness 20), and on this substrate, a pressure I x 10-'Torr and a substrate temperature 15
Bi was vacuum-deposited at 0° C. to form a low melting point metal base film with a thickness of 200 μm.

Next, a pressure of 1xlO-'70 was applied on this base film in the same manner.
CO was deposited by electron beam under the conditions of r r +substrate temperature of 150° C. to form a metal magnetic thin film with a thickness of 1000 μm.

Furthermore, a carbon protective film was formed on the metal magnetic thin film to a thickness of about 200 by electron beam evaporation (acceleration voltage: 7 KeV) as shown in the following table.

Further, this carbon protective film was subjected to direct current bombardment treatment under a pressure of 0.05 Torr by introducing nitrogen gas.

Thereafter, it was taken out into the atmosphere and stored at a temperature of 20° C. and a humidity of 50% for 12 hours or more.

Comparative Example 1 As in the previous example, first, an Al-Mg substrate (thickness approximately 1°
．． 5m, outer diameter 95mm, inner diameter 25fl2, average surface roughness 20
(person) and apply pressure IX 10-'Tor on this substrate.
A low melting point metal undercoat film having a thickness of 200 μm was formed by vacuum evaporating Bi under the conditions of 150° C. and a substrate temperature of 150° C.

Then, a pressure of lXl0-'Tor
A metal magnetic thin film having a thickness of 1000 nm was formed by electron beam evaporation of CO under conditions of 150° C. and a substrate temperature of 150° C.

Furthermore, as shown in the following table, a carbon protective film was formed on the metal magnetic thin film to a thickness of about 200 by electron beam evaporation (acceleration voltage: 7 KeV). It was formed like this.

Thereafter, it was taken out into the atmosphere and stored at a temperature of 20° C. and a humidity of 50% for 12 hours or more.

Comparative Example 2 As in the previous example, first, an Al-Mg substrate (thickness of about 1
．． 5 ms, outer diameter 95 N, inner diameter 25 Tsuru 1 surface average roughness 20) was prepared, and a pressure of IX 10-'T was applied on this substrate.
Bi was vacuum-deposited at a substrate temperature of 150° C. to form a low melting point metal base film with a thickness of 200 μm.

Then, a pressure of lXl0-'Tor
A metal magnetic thin film having a thickness of 1000 nm was formed by electron beam evaporation of CO under conditions of 150° C. and a substrate temperature of 150° C.

Thereafter, it was taken out into the atmosphere and stored at a temperature of 20° C. and a humidity of 50% for 12 hours or more.

A corrosion test was conducted on the sample disks obtained in the above examples and comparative examples. In addition, this corrosion test
A 96-hour accelerated corrosion test was conducted in an environment with a temperature of 60° C. and a relative humidity of 90%, and pitting corrosion loss per unit area after the test was measured using an optical microscope. The results are shown in the table below.

Table From this table, by bombarding the surface of the carbon protective film and making the contact angle with water 756 or more,
It can be seen that corrosion is significantly reduced and corrosion resistance is improved.

Although specific embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to these embodiments.

〔Effect of the invention〕

As is clear from the above description, in the magnetic disk of the present invention, the contact angle of the surface of the carbon protective film with water is set to 75" or more, so the affinity of this carbon protective film to water is small, and the metal magnetic Corrosion of the thin film is prevented, greatly improving corrosion resistance.Also, since a carbon protective film is formed, running performance and durability are ensured.

Claims (1)

[Claims] 1. A magnetic disk characterized in that a metal magnetic thin film is formed on a substrate, and a carbon protective film having a surface contact angle with water of 75° or more is formed on the metal magnetic thin film.