JPS63175219A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To prevent adsorption of a magnetic head by forming a magnetic thin film having 40-100Angstrom surface roughness on a nonmagnetic substrate of <=40Angstrom surface roughness. CONSTITUTION:A magnetic thin film having 40-100Angstrom surface roughness Rmax is formed on a substrate having a super-position surface of <=40Angstrom Rmax. The 40-100Angstrom Rmax is controlled by an effective heat treatment. The Rmax of the magnetic thin film is increased with increase of the heat treatment temperature and the heat treatment time. In such a case, the increase of the treatment temperature is more effective than the increase the treatment time. The heat treatment is carried out at about 300 deg.C. In such a way, the adsorption can be avoided between a magnetic head and the surface of a magnetic thin film.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording medium with good surface properties used in an apparatus.

Prior Art As the capacity of magnetic disk storage devices increases, magnetic properties,
Sputter-type magnetic disks, which are more advantageous than coating-type magnetic disks in terms of recording density, are attracting attention.

In coating type magnetic disks, the magnetic layer thickness is relatively thick, about 1 to 2 μm, so the surface properties of the disk medium are not significantly affected by the surface properties of the substrate. In contrast, in sputter type magnetic disks, Since the magnetic layer thickness is as thin as α5μ or less, the surface properties of the substrate significantly affect the surface properties of the disk medium. Therefore, by using a substrate with excellent surface precision, it is possible to improve the surface properties of a thin film magnetic disk medium. As a result, the flying height of the magnetic head can be reduced and the recording density can be improved.
A N1-P plated layer with a thickness of about 0μ is formed and this surface is polished, or an aluminum alloy surface is anodized to form a hardened alumite layer with a thickness of about 2μ, and the alumite surface is polished. The substrate is something. These substrates have a surface roughness (Rxnhx) of 115 pW'.
A surface of about L is obtained.

When forming magnetic thin films on these substrates, for example, Co
- When forming a magnetic thin film mainly composed of Ni, Cr is sputtered on the substrate, a magnetic thin film mainly composed of Co-Ni is sputtered on top of this at about 1000A, and then C etc. A theoretical lubricating film of about 200A is formed. The surface of the medium thus obtained has a surface roughness (Rxnhx) of approximately α15μ, reflecting the surface properties of the substrate. When forming a magnetic thin film whose main component is iron oxide,
A target containing F as a main component is sputtered in an Ar + Ox atmosphere, and a sputtered film containing α-F@203 as a main component is formed on a substrate to a thickness of about 2000 Å. This was heated to about 500°C in a reducing atmosphere and g-F@! A film containing Os as a main component is changed to a film containing F@304 as a main component, and further heated to about 300°C in an oxidizing atmosphere to form r-F.
The film is mainly composed of gos.

A retaining W1 lubricating film is further formed on this to serve as a medium.

The surface of the medium thus obtained also has a surface roughness (Rmax) of approximately α15 pm, reflecting the surface properties of the substrate.

For substrates in which an Nt-P plating layer is formed on an aluminum alloy and the surface is polished, it is necessary to activate the aluminum alloy surface before performing N1-P plating, and the process of forming the substrate is It becomes sloppy. Further, the steps after the activation process account for more than 50% of the substrate price, making the substrate relatively expensive. Furthermore, when the N1-P plating layer is heated above 150°C, it crystallizes and becomes magnetic, so this substrate can be used when a heating process is required, such as when forming a magnetic iron oxide film. Can not.

When a substrate with an alumite film formed on an aluminum alloy is subjected to heat treatment, cracks are likely to occur in the alumite film due to the stress generated due to the difference in thermal expansion coefficient between the aluminum alloy and the alumite film. kp upper ↓ te 7 ヱ The heating temperature for each Eva store m hard work I and class cat 9 is 300
It is limited to temperatures below about ℃. Furthermore, the alumite film has a large number of current-carrying holes and has a porous structure.

Therefore, when a thin film magnetic layer is formed on this substrate, magnetic defects are likely to occur in the portions of the conductive holes, and the surface precision is not sufficient as Rmax is Q, about 15 pm.

Despite the above drawbacks, the present invention has a rough surface Rmax
), and a magnetic recording medium in which a magnetic thin film for magnetic recording is formed on a glass substrate with an ultra-precision surface processing, and at least a portion of the surface is strengthened or the surface is roughened.
) has been published and a patent application has been filed for a magnetic recording medium in which a magnetic thin film for magnetic recording is formed on a glass substrate whose surface has been processed with ultra-precision so that the current is 100 A or less (preferably 50 A or less). (Patent Application No. 6O-185022) L, Kaji, Further study of the magnetic recording medium according to the above invention revealed that the surface roughness (Rmax) of the glass substrate was set to less than 40A, and even less than 20A, and a magnetic thin film for magnetic recording was formed on the surface roughness (Rmax) of the glass substrate. It has become clear that when a magnetic head slider surface is formed, an adsorption phenomenon occurs between the magnetic head slider surface and the magnetic thin film surface.

In other words, due to the attraction phenomenon, the magnetic head does not float for a short time when the magnetic disk starts rotating, and the disk rotates while the magnetic head slider surface is in contact with the magnetic thin film surface.
If the surface is damaged or there is significant Ti adhesion, the magnetic head slider surface remains stuck to the magnetic thin film surface and does not move, causing problems such as the inability to start rotation of the magnetic disk.

OBJECTS OF THE INVENTION An object of the present invention is to provide a magnetic recording medium that has high surface precision and does not have to worry about being attracted by a magnetic head, and a method for manufacturing the same.

Structure of the Invention In magnetic disks, it is effective to reduce the flying height of the magnetic head in order to improve the recording density, and in recent disk drives there is a movement to reduce the flying height to less than (L2μ false).

If a magnetic disk with poor surface properties is used and the flying height of the head is reduced, the magnetic head will come into contact with protrusions on the surface of the medium, resulting in the magnetic thin film being scraped off or the magnetic head being destroyed. In other words, the ultra-precise surface properties of the medium are an important point for stably flying the magnetic head and determining how small the flying height can be.

However, when a magnetic thin film is formed on a substrate having an ultra-precision surface with a surface roughness (Rmax) of 4 QA or less, the surface of the magnetic thin film also rebels against the surface properties of the substrate, resulting in an ultra-precision surface (surface roughness (Rmax)). (Rmax) 40 A or less), and as described above, the attraction phenomenon between the magnetic thin film and the magnetic head appears.

The magnetic recording medium in the present invention has a surface roughness (Rmax)
Despite using a substrate with an ultra-precise surface of 40λ or less, the surface roughness of the magnetic thin film is
) is 40 to 100 people, so that the magnetic thin film and the magnetic head do not attract each other, and the flying height of the magnetic head of 12 μm or less can be realized.

The surface roughness (Rmax) of the magnetic thin film is 40 to 1ooX
This can be effectively achieved by heat treatment. The surface roughness (Rmax) of the magnetic thin film can be increased by increasing the heat treatment temperature and heat treatment time, but the heat treatment temperature is more effective.
Temperatures around 300°C are used.

As the material of the glass substrate used in the present invention, almost any glass can be used, such as borosilicate glass, aluminosilicate glass, quartz glass, titanium silicate glass, etc. However, glass that does not contain crystalline components is preferable. This is because the strength of the grain boundaries is relatively weak, so when mechanochemical finishing is performed, the grain boundaries are polished quickly and an ultra-precise surface cannot be achieved.

For substrates with N1-P plating layer or alumite layer on aluminum alloy, there are restrictions on heating temperature, but the glass substrate according to the present invention can be used up to about 400℃, so magnetic oxidation is possible. It can be used particularly effectively when a heating process is required, such as when forming an iron film.

In a magnetic disk device, the magnetic disk is
fj l'l +++++ s+=+
t+l# 11% 1i'dl! ';J
12 -w hq L J,, sh
'Q>1ze The SD disk must have sufficient strength to withstand it.

For such applications, there are concerns about strength since a glass substrate is used, but as a result of intensive study by the present inventors, it is possible to make a magnetic disk by strengthening at least a portion of the surface of the glass substrate. O 2 surface strengthening, which has been shown to be able to impart strength, is generally carried out by replacing ions on the glass surface with larger ions at a temperature below the glass transition point. The ion replacement method is carried out by immersing the glass in a potassium nitrate solution heated to about 450°C. As a result of this substitution, a compressive stress layer with a steep distribution is formed on the surface as shown in Figure 1.
The surface of the substrate is strengthened. The thickness of this stress layer can be adjusted from 10 to 2 by controlling the temperature and time during ion replacement.
Make 00P false.

When considering magnetic disks, the areas where the surface should be strengthened are:
Inner diameter edge, inner diameter edge periphery, outer diameter edge, outer diameter kl! I can think of cutting off the button or removing the button.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

[Example 1] Aluminosilicate glass was used as a substrate. The shape is a disc with an outer diameter of 15Qwm, an inner diameter of 4Qsss, and a thickness of t911m. This glass substrate was subjected to mechanochemical boring for 20 minutes using a polishing liquid containing colloidal silica. The surface roughness (Rmax) was 55λ.

A 2000X Cr thin film was formed on this substrate by sputtering, and a Co-20vt%N1 magnetic thin film was further formed.

The roughness (Rmay) of this magnetic UPA surface was 55, the same as that of the substrate, and an adsorption phenomenon between the magnetic thin film and the head was observed.

Regarding this magnetic disk, the surface roughness of the magnetic thin film R
max), heat treatment was performed at each temperature for 1 hour in a nitrogen atmosphere. The surface roughness of magnetic *i at this time
Figure 1 shows the changes in Rmax). In addition, we investigated the flying stability of the magnetic head for the disk after heat treatment, and as the flying height was reduced, the critical flying height for stable flying was determined to be the first.
It is shown in the figure. As can be seen from the figure, by tuning the surface roughness (Rrn*x) of the magnetic thin film to 40 to 100 A, it is possible to stably levitate the magnetic head with a flying height of Q, 2 μm or less. It is possible to obtain a magnetic disk that does not cause the phenomenon of attraction between the magnetic head and the surface of the magnetic thin film.

[Example 2] When the same glass substrate as in Example 1 was subjected to mechanochemical boring for 30 minutes, the surface roughness was found to be Rxn*x
) became 171.

On this substrate, as in Example 1, a Cr thin film and a Co-20v
t%N1 magnetic thin films were sequentially formed and further heat treated, and changes in surface roughness (Rmax) of the magnetic thin films and flying stability of the magnetic head were investigated. The results are shown in FIG.

FIG. 6 shows an example of surface roughness measurement. Figure 3 (a) shows the surface roughness measurement results after the film formation of C.
This is the surface roughness measurement result after heat treatment at 0° C. for 1 hour. From the results in FIG. 2, as in Example 1, by adjusting the surface roughness (Rmax) of the magnetic thin film to 40 to 100A,
The magnetic head can be stably floated with a flying height of α2ptn or less without being attracted.

In addition, in an example in which the surface roughness (Rmax) of the substrate is 20 Å or less, the surface roughness (Rmax) of the substrate is 4
It can also be seen that the flying height can be made smaller than in Example 1, which is 0 Å or less, which is more advantageous.

In addition, the surface roughness (Rmax) of the magnetic N film is 50 to 8
In order to adjust the magnetic head to zero, it is sufficient to perform heat treatment at a reasonable temperature of around 500° C., and the flying height of the magnetic head can also be made relatively small in this region, so that it can be used more effectively.

[Example 3] Aluminosilicate glass was used as the glass substrate material.

The shape is the same as in Example 1, which is a disk shape.

The surface of this glass substrate was strengthened. This is done by applying a mask to the areas that are not to be strengthened, and soaking them in molten potassium nitrate salt at 450℃ for 10 hours. ? ,'M
TJjL is 160μ duck. This substrate was subjected to mechanochemical boring for 30 minutes using a polishing liquid containing colloidal silica. Substrate surface roughness Rmax)
There were 17 people, almost the same.

On top of this, a Cr thin film was applied as in Example 1, and then a Co-
20w*%-N1 magnetic thin films were sequentially formed and further heat treated, and changes in the surface roughness (Rmax) of the magnetic thin films and flying stability were investigated. Example 2 was found before and after heat treatment.
We obtained results that were substantially the same as those shown in Figure 2. The strength of the substrate in this example has been proven in the earlier application cited above.

4 Brief Description of the Drawings FIG. 1 is a graph showing the relationship between the heat treatment temperature of the recording medium, the surface roughness of the magnetic surface, and the flying height in Example 1 of the present invention, and FIG. 2 is a graph showing the relationship between Example 2 of the present invention. A graph showing a similar relationship in Figure 5 shows surface roughness, (1) before heat treatment and (b)
) indicates the surface roughness of the magnetic surface after heat treatment.

Figure 1 Binbahi Suyu earth 15 haj ('C) Figure 2

Claims (8)

[Claims] (1) In a magnetic recording medium formed by forming a magnetic thin film on a non-magnetic substrate, the surface roughness (Rmax) of the non-magnetic substrate is 4
less than 0 Å, and the surface roughness (Rmax) of the magnetic thin film is 4
A magnetic recording medium characterized in that it has a thickness of 0 to 100 Å. (2) The magnetic recording medium according to claim 1, wherein the nonmagnetic substrate has a surface roughness (Rmax) of 20 Å or less. (3) The magnetic recording medium according to claims 1 and 2, wherein the nonmagnetic substrate is a glass substrate with at least a portion of its surface reinforced. (4) Surface roughness (Rmax) of magnetic thin film is 50 to 80 Å
A magnetic recording medium according to any one of claims 1 to 3, characterized in that: (5) After forming a magnetic thin film on a non-magnetic substrate with a surface roughness (Rmax) of 40 Å or less, the surface roughness (Rmax) of the magnetic thin film is adjusted to 40 to 100 Å by heat treatment. A method for manufacturing a magnetic recording medium. (6) The method for manufacturing a magnetic recording medium according to claim 5, wherein the surface roughness (Rmax) of the nonmagnetic substrate is 20 Å or less. (7) The method of manufacturing a magnetic recording medium according to claims 5 and 6, wherein the nonmagnetic substrate is a glass substrate having at least a portion of its surface reinforced. (8) Surface roughness (Rmax) of magnetic thin film is 50 to 80 Å
8. The method of manufacturing a magnetic recording medium according to claim 5, wherein the heat treatment conditions are selected so that the following results are obtained.