JPH03113722A - Production of magnetic disk - Google Patents

Abstract

PURPOSE:To improve lubrication property and to increase reliability by subjecting a substrate to heat treatment before and after applying a liquid lubricant on a protective film surface by dipping and thus, forming a lubricant layer of the liquid lubricant on the substrate. CONSTITUTION:There are successively formed a continuous, ferromagnetic metal thin film and a hard protective film on a disk type nonmagnetic substrate in this order, and then a lubricating layer is formed by coating the hard protective film with a liquid lubricant. Before applying the lubricant, the nonmagnetic substrate on which the magnetic film and hard protective film and provided is first subjected to heat treatment, then coated with the liquid lubricant by dipping, treated by heating and rotated by at least 3,600 rpm for at least 30 minutes around the center axis perpendicular to the substrate to form the lubricant layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a magnetic disk mounted in a fixed magnetic disk device used as an external memory of a computer or the like.

[Conventional technology]

In recent years, with the increase in information processing, the capacity of memory in computers and other devices has increased, and the storage elements of magnetic disk drives have become
In place of conventional coated magnetic disks, so-called thin-film magnetic disks, in which the recording layer is a continuous magnetic thin film made of ferromagnetic metal that enables higher-density recording, have become mainstream.

Fixed magnetic disk drives generally use the C8S system. The magnetic disk is built into the device in combination with a magnetic head, and when the device is stopped, the magnetic head comes into contact with the surface of the stopped magnetic disk, and when the device is running (
When recording/reproducing information), the magnetic disk travels slightly floating above the surface of a magnetic disk rotating at high speed, and slides into contact with the surface of the magnetic disk when starting and stopping drive of the device. Therefore,
A magnetic disk has excellent magnetic properties that can support high-density recording, and its surface has a suitable roughness that allows good sliding contact with the magnetic head and prevents the magnetic head from attracting the magnetic head when it is stopped. It has excellent lubrication properties on hard surfaces.
In addition, it is required that there be no minute protrusions that would disturb the low flying motion of the magnetic head to enable high-density recording.

For this reason, thin-film magnetic disks are usually manufactured using a non-magnetic substrate made of an A1 alloy substrate with an N1-P alloy layer formed by electroless plating, or a non-magnetic substrate made of glass. A non-magnetic metal underlayer 9 for example, a Cr underlayer is provided, and a continuous magnetic thin film made of a ferromagnetic metal 2, for example a CO alloy, and a similarly thin hard protective film are sequentially formed thereon by sputtering or vapor deposition. Films are laminated.

The hard protective film is provided to protect the magnetic thin film, and is made of oxides such as carbon and silicon dioxide.

Alternatively, it may be made of stable, hard materials such as other ceramic materials. The surface of this hard protective film has good lubrication properties and stable low flying motion of the magnetic head (flying height 0.1μl'11
~0.3 μm), the center line average roughness R
A has a finely roughened surface of 20 to 100 grains, and
Surface microprotrusions have been removed.

A lubrication layer coated with a liquid lubricant is then formed on the surface of this protective film to further improve the lubrication properties.

Examples of liquid lubricants include Fonpurin (product name: manufactured by Montegisson), Talitox (product name: manufactured by DuPont),
Fluorocarbon-based liquid lubricants such as Demnum (trade name; manufactured by Daikin Industries, Ltd.) are known to be effective. Further, as methods for applying liquid lubricants, spin cord methods, spray methods, puff methods, dipping methods, and the like are known, but the dipping method is often used because of its high productivity.

[Problem to be solved by the invention]

The thickness of the lubricating layer formed on the surface of the magnetic disk is required to be about 10 to 20 layers thick.

If it is thinner than about 10 people, it will be difficult to form a uniform and stable layer.
Good lubrication properties cannot be obtained. When the number of people increases to about 20 or more, the magnetic head tends to be attracted.

It is extremely difficult to apply liquid lubricant in such a thin and uniform manner.

In addition, once the liquid lubricant has formed a lubricating layer, it is necessary that the liquid lubricant adheres firmly to the disk surface and exists stably without causing migration or detachment during use. However, since the surface of the protective film underlying the lubricating layer is a rough surface with extremely fine roughness, the mechanical adhesion with the liquid lubricant is weak, and the material of the protective film is inert.
There was a problem that the physical and chemical bonding strength was weak, making it difficult to obtain strong adhesion.

Furthermore, liquid lubricants that are polymeric materials have a molecular weight distribution, and low molecular weight components are easily vaporized. For this reason, there is a problem in that the low molecular weight components of the liquid lubricant applied to the surface of the magnetic disk volatilize during use, changing the lubricating properties of the lubricating layer.

To eliminate these problems, protective film materials.

Many proposals have been made regarding lubricant materials and methods for forming lubricant layers, but none have yet reached a fully satisfactory state.

This invention was made in view of the above points, and
An object of the present invention is to provide a method for manufacturing a magnetic disk, which can form a lubricating layer with good adhesion, stability over time, and excellent durability on the surface of a magnetic disk.

[Means to solve the problem]

According to the present invention, the above problem can be solved by forming a ferromagnetic metal continuous magnetic thin film and a hard protective film in this order on a disk-shaped non-magnetic substrate, and then applying a liquid lubricant on the hard protective film to lubricate it. In a method for manufacturing a magnetic disk including a step of forming a layer, the non-magnetic substrate on which the hard protective film has been formed is heat-treated, a liquid lubricant is then applied to the surface by a dipping method, and then post-heat treatment is performed. However, the problem can be solved by forming a lubricating layer by subsequently rotating the disk-shaped nonmagnetic substrate about its vertical central axis at at least 3600 rpITl for at least 30 minutes.

[Effect]

The surface of the protective film is affected by the atmosphere during the period of time after the protective film is formed and until the liquid lubricant is applied, but generally the influence of moisture is the greatest. By performing heat treatment before applying liquid lubricant, the state of adsorbed water on the surface of the protective film or the state of deterioration due to moisture (for example, the state of hydrocarbon on the surface of the carbon protective film) can be changed depending on the length of time it is left. The lubricating layer can be kept constant without any fluctuation, and a uniform lubricating layer with good adhesion can be formed. Heating temperature is 110℃~20℃
The temperature may be within the range of 0°C, and heating for at least 1 hour is sufficient.

In addition, as mentioned above, liquid lubricants that are organic polymer materials have a molecular weight distribution, and low molecular weight components easily volatilize.
After applying the liquid lubricant, by performing post-heat treatment, the low molecular weight components in the applied liquid lubricant are volatilized and removed.
Only the liquid lubricant that can exist stably remains on the protective film, forming a stable lubricant layer over time. The low molecular components and their content vary depending on the liquid lubricant, but
By performing the heat treatment at a temperature of 100° C. or more and 200° C. or less for at least 1 hour, unstable low molecular weight components can be removed to the extent that they do not pose a practical problem.

Furthermore, by subsequently rotating at a high speed of at least 3600 rpm for at least 30 minutes, the liquid lubricant, which was not necessarily uniformly present on the protective film by mere immersion, is present in a highly homogeneous state. become. Usually, in fixed magnetic disk drives,
In many cases, the rotation of a magnetic disk is put into practical use at about 3600 rpm, and it can withstand practical use if it is stabilized at at least 3600 rpm. Also, at least 30
By rotating for a minute, the liquid lubricant will stably exist on the surface of the protective film with a uniform thickness, and no migration will occur thereafter.

In this way, good adhesion can be achieved by forming a lubricant layer through the steps of pre-heating the non-magnetic substrate on which a protective film has been formed, applying a liquid lubricant, then post-heating, and then rotating at high speed. , it is possible to obtain a magnetic disk having a lubricating layer that is stable over time and has excellent durability.

〔Example〕

Example 1 A Ni2 alloy layer was formed by electroless plating on the surface of a disk-shaped Al-Mg alloy substrate with an outer diameter of 95 mm, an inner diameter of 25 mm, and a thickness of 2.7 m+n, and the surface was polished to make it smooth. Further, texture was applied in the circumferential direction with an abrasive tape, and the surface roughness was made into a substrate for a magnetic disk of about 35 people with a center line average roughness Ra. On this substrate, a Cr underlayer with a thickness of 1500 layers and a Co-N layer with a thickness of 450 layers were formed by sputtering.
An i-Cr alloy magnetic layer and an 8102 protective layer having a thickness of 200 mm were sequentially formed.

The substrate on which the Sin and protective layers were formed was heat-treated at a temperature of 120° C. for 1 hour in a clean oven.

After that, fluorocarbon liquid lubricant (Fomblin Z
:Montegison>1) Lafron 113 (CF C113
Liquid lubricant was applied onto the 5102 protective layer by dipping it into a solution diluted to 0.2% with Subsequently, post-heat treatment was performed at a temperature of 150° C. for 1 hour in a clean oven.

Next, set the board on the spin stand and
00 rpm for 30 minutes to form a lubricating layer.
A magnetic disk was created.

Comparative Example 1 A magnetic disk was produced in the same manner as in Example 1, except that the final high-speed rotation treatment in the lubricant layer forming step was not performed.

Comparative Example 2 A magnetic disk was produced in the same manner as in Example 1, except that the heat treatment before and after applying the liquid lubricant and the high-speed rotation treatment after applying the liquid lubricant were not performed in the lubricant layer forming step.

For these magnetic disks, CS S (Contact
5tartStop) to measure the friction coefficient.

In the magnetic disk of Comparative Example 2, as soon as the magnetic head was brought into contact with the surface of the magnetic disk, the magnetic head was attracted.
I was unable to perform C8S.

The measurement results for Example 1 and Comparative Example 1 are shown in the diagram of FIG.

From FIG. 1, in the magnetic disk of Example 1, C3
Almost no change in the friction coefficient was observed up to 10,000 cycles of S, showing a sufficiently low value for practical use, indicating that a good and durable lubricating layer was formed. In contrast,
In the magnetic disk of Comparative Example 1, large fluctuations were observed in which the coefficient of friction increased and reached a maximum value during 10,000 cycles of C3S, indicating that the lubricating layer was unstable. Example 1
The superiority of this magnetic disk manufacturing method is obvious.

〔Effect of the invention〕

According to this invention, the substrate is heat-treated before and after dip-coating the liquid lubricant on the surface of the protective film of the magnetic disk, and after the coating is heated, the substrate is finally rotated at high speed to apply the liquid lubricant. Forms a lubricating layer consisting of By adopting this manufacturing method, a lubricating layer with good adhesion, stability over time, and excellent durability can be formed on the magnetic disk surface, resulting in highly reliable magnetic disks with excellent lubrication properties. can be obtained.

[Brief explanation of drawings]

Figure 1 shows C8 of the magnetic disks of Example 1 and Comparative Example 1.
In the diagram showing the relationship between S number and friction coefficient, C8S number (X
IO3) Figure

Claims (1)

[Claims] 1) A magnetic disk comprising the steps of forming a ferromagnetic metal continuous magnetic thin film and a hard protective film in this order on a disc-shaped nonmagnetic substrate, and further applying a liquid lubricant on the hard protective film to form a lubricating layer. In the manufacturing method, the non-magnetic substrate on which the hard protective film has been formed is heat-treated, and then a liquid lubricant is applied to the surface thereof by a dipping method, followed by post-heat treatment, and then at least 3600 rpm. A method for manufacturing a magnetic disk, which comprises forming a lubricating layer by rotating a disk-shaped nonmagnetic substrate about its vertical central axis for 30 minutes.