JPH0762894B2 - Base substrate for magnetic disk - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a base substrate for a magnetic disk on which a thin film magnetic medium is formed on a plate surface, and particularly to a base for a magnetic disk having improved sliding resistance against a magnetic head. Regarding the substrate.

[Background of the Invention]

As a base substrate for a magnetic disk for forming a thin film magnetic medium on a conventional plate surface, an Al substrate subjected to Al anodization treatment or a substrate subjected to Ni-P system plating treatment has been used. These substrates have a surface hardness of Hv≈200 to 600, which has been subjected to a hard coating treatment, and is finished by machine processing such as diamond turning or polishing to have a surface roughness of 0.1 μmRmax or less. A thin film magnetic medium is formed on this substrate, for example, a thickness of 0.1 μm
The following Ni-Co-P magnetic plating is applied, or the thickness is approximately
For a disk substrate with 0.2 μm γ-Fe ₂ O ₃ formed by sputtering, CSS (Contact-Start-Stop) for the magnetic head
There is a problem that the sliding resistance such as characteristics cannot be sufficiently satisfied.

[Object of the Invention]

An object of the present invention is to provide a base substrate for a magnetic disk having improved sliding resistance against a magnetic head.

[Outline of Invention]

According to the present invention, in a base substrate for a magnetic disk, an Al substrate having a hard film formed on a plate surface is polished, and an intermediate film is formed on the Al substrate, and the protrusion of the hard film has an intermediate film in the intermediate film. The distance from the surface of the forming surface to the top of the protrusion is 0.01 to 0.05.
It is intended to improve the sliding resistance against the magnetic head by being scattered at the height of μm, and the principle thereof will be described below.

First, the sliding strength of the magnetic disk will be described. In magnetic disk devices, in order to increase the areal recording density, the gap between the magnetic head and the disk surface has become smaller, and the frequency of contact between the magnetic head and the disk surface has increased dramatically. Therefore, the sliding resistance of the disk surface is increased. There is a need to. As shown in FIG. 4, in the coating type magnetic disk generally used at present, magnetic material 7 of γ-Fe ₂ O ₃ which is needle-shaped fine particles, alumina fine particles 8 as a reinforcing material, and resin 9 as a binder are used. It has a structure in which a mixture of and is applied to the Al substrate 1, and the alumina fine particles 8 in this coating film are dispersed on the substrate surface to improve durability against friction and wear due to contact with the magnetic head. This improves the durability of the magnetic disk.

On the other hand, in the thin film magnetic disk in which the thin film magnetic medium is formed on the plate surface according to the present invention, since the magnetic layer is extremely thin at 0.05 to 0.2 μm, the surface accuracy and hardness are greatly affected by the substrate,
Adhesion strength with the substrate, substrate hardness, etc. greatly affect durability. In addition, the magnetic properties and mechanical properties of the thin film magnetic medium are greatly influenced by the properties of the underlying substrate. From such a point of view, the inventors of the present invention have found that Mo, Ti, and Ni are deposited on a mirror-polished anodized Al substrate or a Ni-P plated substrate.
We are studying the process of forming an intermediate film such as Cr and forming a thin film magnetic medium on this intermediate film. In this research process, it is dispersed on the Ti intermediate film formed on the Ni-P plated surface. It was found that crystal grains having a diameter of 5 to 50 μm were present. The hardness of this crystal grain is larger than the hardness of other parts of the interlayer film, and the crystal grain has a height of 0.01 to 0.1 from the surface.
The convex portion of μm was formed. The present invention has been made based on such findings and the results of research.

In the present invention, as described above, the height of the protrusion is 0.01 to 0.05.
μm, which is due to the following reason. That is,
With the increase in recording density of magnetic disk devices, the gap between the magnetic head and the disk surface has become smaller, and in recent years this gap has become less than 0.1 μm. Therefore, the height of the protrusion on the disk surface is Considering head shake and disturbance, 0.05 μm or less is required. Further, in a comparative example described later, an example in which the CSS characteristics obtained for a magnetic disk using a mirror-finished substrate is poor is described. However, when the height of the convex portion of this magnetic disk is 0.01 μm or less, there were. From these things, the upper limit of the height of the protrusion is set to 0.05 μm,
The lower limit is 0.01 μm.

For the intermediate layer, an invention has heretofore been proposed in which Cr, Ti, Mn or the like is formed between the substrate and the magnetic medium (JP-A-49-74912). It shows that the magnetic properties are improved by the interlayer film. However, the technology disclosed therein was made after recognizing the problem of the adhesion between the substrate and the magnetic medium, the crystal grains existing in the intermediate film, and the relationship between the crystal grains and the sliding resistance. is not.

Example of Invention

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a view showing a model of a cross section of a base substrate for a magnetic disk of the example, and an Al alloy disk made of an Al alloy disk having a thickness of about 2 mm.
A base substrate is shown in which a Ni-P plated film 2 having a thickness of about 20 μm is formed on both surfaces of a substrate 1, mirror-polished, and then an intermediate film 3 is formed by a sputtering method, and the surface is finished. In addition,
Reference numeral 4 is a protrusion. Further, FIG. 2 is a model of a cross section of a magnetic disk in which iron oxide is sputtered to a thickness of about 0.2 μm on the above-mentioned base substrate to provide a magnetic medium 5 and a lubricating film 6 having a thickness of 1 nm or less is formed on the surface thereof. FIG.

Hereinafter, a method for manufacturing the above-mentioned magnetic disk base substrate will be described in detail. First, after polishing both surfaces of an Al substrate 1 which is an Al alloy disk having an outer diameter of 210 mm, an inner diameter of 100 mm and a plate thickness of 2 mm, Ni-on both surfaces.
The P plating film 2 was formed to a thickness of about 20 μm. Both surfaces of this Ni-P plated substrate were polished to give a mirror surface having a surface roughness of 0.01 μmRa or less. Next, Ti is applied to both surfaces of the substrate by Ar gas pressure.
Under the conditions of 5 mTorr, substrate temperature of 200 ° C., and input power of 2 kW, sputtering was performed to form an intermediate film 3 having a thickness of 0.05 μm. On the surface on which the intermediate film 3 is formed, as shown in FIG.
The projections 4 having a height of about 0.02 to 0.03 μm and a size of about 10 to 20 μm were scattered all over the surface. The protrusion 4 is formed on the intermediate film 3
It is harder than the Ti film which is the other part, and even if the surface of the intermediate film 3 was surface-finished with a polishing cloth, it did not decrease. next,
An iron oxide magnetic medium 5 having a thickness of 0.2 μm is formed on the substrate in Ar—O ₂ gas, and a fluorine-based lubricating film 6 having a thickness of 1 μm.
It was formed with a thickness of nm or less. As shown in FIG. 3, the cross-sectional shape of this surface shows that a projection of about 0.02 μm is formed, and the projection 4 when the intermediate film 3 is formed remains on the surface. A CSS characteristic test using a magnetic head was performed on this sample, and good results were obtained.

On the other hand, for comparison with the base substrate of the above example, both surfaces of the Ni-P plated substrate were polished to obtain a surface roughness of 0.01 μmR.
On a mirror-finished substrate of a or less, a magnetic medium of iron oxide was formed in Ar-O ₂ gas to a thickness of about 0.2 μm, and a fluorine-based lubricating film was formed to a thickness of about 1 nm or less to prepare a sample. This sample was subjected to the same CSS characteristic test as described above, but the result was worse than that of the above example, and only a characteristic value lower by about one digit was obtained.

〔The invention's effect〕

According to the present invention, in the magnetic disk base substrate, since the hard and minute height protrusions are uniformly dispersed on the substrate surface, the sliding resistance strength such as CSS characteristics due to the slider portion of the magnetic head is significantly increased. Has the effect of improving. Also,
This minute protrusion does not affect the noise error in the electromagnetic conversion characteristics, and the height of the minute protrusion is 0.03 μm or less, which does not affect the flying characteristics of the magnetic head. It is possible to achieve great reliability improvement.

[Brief description of drawings]

FIG. 1 is a diagram showing a model of a cross section of a base substrate for a magnetic disk according to an embodiment of the present invention, and FIG. 2 is a model showing a cross section of a magnetic disk having a magnetic medium and a lubricating film formed on the substrate. FIG. 3 is a diagram showing a sectional curve of the surface of the base substrate according to the present invention, and FIG. 4 is a sectional view of a conventional coated magnetic disk. Explanation of symbols 1 ... Al substrate, 2 ... Ni-P plating film 3 ... Intermediate film, 4 ... Protrusions 5 ... Magnetic medium, 6 ... Lubrication film

Claims (3)

[Claims] 1. A base substrate for a magnetic disk in which a thin film magnetic medium is formed on a plate surface by sputtering or plating, an aluminum substrate having a hard film formed on the plate surface is polished, and an intermediate film is formed thereon. The magnetic film is characterized in that the projections of the hard film are scattered in the intermediate film at a height of 0.01 to 0.05 μm from the surface of the surface on which the intermediate film is formed to the top of the projections. Base substrate for disks. 2. A base substrate for a magnetic disk according to claim 1, wherein the hard film is formed by a Ni-P plating process. 3. A base substrate for a magnetic disk according to claim 1, wherein the intermediate film is made of any one of Ti, Mo and Cr.