JPH10334459A - Magnetic disk substrate and magnetic disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease the polishing allowance of a hard dense layer even when a thin hard dense layer such as a NiP plating film is formed on an aluminum alloy disk surface, to obtain high recording density of a magnetic disk and to prevent sticking of a magnetic head to a magnetic disk surface in a halting state of a magnetic disk device. SOLUTION: This magnetic disk substrate comprises an aluminum alloy disk 1 the surface of which is concentrically roughened, and a hard dense layer 2 formed on the surface of the aluminum alloy disk 1. The surface roughness of the aluminum alloy disk 1 is controlled to <10 Å Ra measured in the perpendicular direction to the tangential lines of the concentric circles. The surface roughness of the CSS zone in the surface of the hard dense layer 2 is >=10 ÅRa. Then a recording medium 3 is formed on the obtd. substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention belongs to the technical field of magnetic disk substrates and magnetic disks.

[0002]

2. Description of the Related Art In recent years, the recording density of a magnetic disk has been increased, and the capacity of a magnetic disk device (HDD) as an external recording device has been increased.

When the recording density is improved from the magnetic head side, it is effective to reduce the flying height of the magnetic head in order to increase the recording density. To achieve this, the surface required for a magnetic disk substrate is required. It is necessary to make the roughness extremely small.
Under a high recording density of several Gbits / in ² or more, the flying height of the magnetic head needs to be set to 0.05 μm or less. In this case, the maximum surface roughness allowed for the magnetic disk substrate is said to be 1/10 or less of the flying height of the magnetic head, that is, 50 ° or less. For this reason, at present, as a magnetic disk substrate, an electroless NiP plating film is applied as a hard dense layer on the surface of an aluminum alloy substrate (disk) to improve the surface roughness, and the surface of this NiP plating film is further improved. What has been subjected to finish polishing to reduce the surface roughness, that is, a NiP / Al substrate is generally used.

A magnetic disk is obtained by forming a medium comprising a Cr underlayer, a Co-based alloy magnetic film, a C protective film and the like on the surface of such a magnetic disk substrate by a sputtering method or the like.

When the surface roughness of the magnetic disk substrate is reduced as much as possible to increase the recording density of the magnetic disk, in a general magnetic disk device, the magnetic head is attracted to the surface of the magnetic disk when stopped. Problem arises. In order to prevent this, conventionally, a texturing process has been performed to uniformly and finely roughen the entire surface of the magnetic disk substrate. Peripheral CSS (Cont
act Start Stop) Zone texture processing, which only finely roughens the zone, is becoming the mainstream. Under such circumstances, it is necessary to further reduce the roughness of the data recording area (data zone). ing.

In addition, a magnetic disk drive,
In order to reduce the cost of magnetic disks, NiP / Al substrates have also been reduced in thickness and polishing allowance for NiP plating films.
At this time, there is a new problem that the surface condition of the aluminum alloy (Al alloy) disk as the base material greatly affects the performance. In other words, when the surface roughness of the Al alloy disk is large, and when the NiP plating film formed on the surface is thin,
Since the surface roughness of the NiP plating film itself formed on the surface also becomes large, it is necessary to increase the polishing allowance of the NiP plating film, which causes a problem that the cost increases.
Also, as the polishing allowance for the NiP plating film increases,
The roll-off at the edge of the P / Al substrate also increases,
Many problems arise, such as the end of the magnetic disk not functioning as a data zone, which hinders an increase in capacity.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and its object is to provide
Even when a hard dense layer such as a NiP plating film is formed thinly, the polishing allowance of the hard dense layer after the formation is reduced, the recording density of the magnetic disk is increased, and the magnetic disk device is stopped. It is an object of the present invention to provide a magnetic disk substrate and a magnetic disk which can prevent the magnetic head from being attracted to the surface of the magnetic disk in the state.

[0008]

In order to achieve the above object, a magnetic disk substrate and a magnetic disk according to the present invention include a magnetic disk substrate according to claims 1 and 2, and a magnetic disk according to claim 3. It has the following configuration. That is, a magnetic disk substrate according to claim 1, comprising: an aluminum alloy disk whose surface is concentrically roughened; and a hard dense layer formed on the surface of the aluminum alloy disk. Wherein the surface roughness of the aluminum alloy disk is less than 10 ° in surface roughness Ra perpendicular to a tangent to the concentric circle, and a portion corresponding to a CSS zone in the surface of the hard dense layer. A magnetic disk substrate having a surface roughness of 10 ° or more in surface roughness Ra (first invention).

According to a second aspect of the present invention, in the magnetic disk substrate, the aluminum alloy disk has a surface roughness Ra of 1 °.
2. The magnetic disk substrate according to claim 1, wherein the angle is not less than 10 ° (second invention).

According to the third aspect of the present invention, there is provided a magnetic disk.
A third aspect of the present invention is a magnetic disk formed by forming a medium on the magnetic disk substrate of the second aspect.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is implemented, for example, as follows. The surface of the aluminum alloy disk is polished so as to be concentrically roughened. That is, the surface of the aluminum alloy disk is textured concentrically. At this time,
Surface roughness Ra perpendicular to the tangent of the concentric circle is 10 °
Finish to be less than. Next, a hard dense layer such as an electroless NiP plating film is formed on the surface of the polished aluminum alloy disk. Next, finish polishing is performed on the surface of the hard dense layer. At this time, CS in the surface of the hard dense layer
The portion corresponding to the S zone is roughened so that the surface roughness Ra becomes 10 ° or more. Then, the magnetic disk substrate according to the present invention (first invention) is obtained.

A medium including a Cr underlayer, a Co-based alloy magnetic layer, a C protective layer and the like is formed on the surface of the magnetic disk substrate by a sputtering method or the like. Then, a magnetic disk is obtained.

In order to achieve the object of the present invention, the present inventors have made thin hard dense layers such as a NiP plating film formed on the surface of an aluminum alloy disk and reduced polishing allowance of the hard dense layers. Even so, the intense research was conducted from the viewpoint that it is important to obtain a high-performance surface state as a magnetic disk. As a result, the surface of the aluminum alloy disk is roughened concentrically so that the surface roughness Ra in a direction perpendicular to the tangent line of the concentric circle is less than 10 °, and the surface of the aluminum alloy disk is When a hard dense layer such as a plating film was formed, and the surface roughness Ra of a portion corresponding to the CSS zone in the surface of the hard dense layer was 10 ° or more, the hard dense layer was formed thin on the surface. Even in such a case, the polishing allowance of the hard dense layer after the formation is reduced, and further,
It has been found that the recording density of the magnetic disk can be increased and that the magnetic head can be prevented from sticking to the surface of the magnetic disk when the magnetic disk device is stopped. The present invention has been completed based on such findings.

That is, as described above, the magnetic disk substrate according to the present invention comprises an aluminum alloy disk whose surface is concentrically roughened, and a hard dense layer formed on the surface of the aluminum alloy disk. Wherein the aluminum alloy disk has a surface roughness Ra of less than 10 ° in a direction perpendicular to a tangent line of the concentric circle, and a surface roughness of the hard dense layer. Has a surface roughness Ra of 10 ° or more in a portion corresponding to the CSS zone.

As described above, the surface of the aluminum alloy disk is roughened concentrically, the surface roughness Ra perpendicular to the tangent to the concentric circle is less than 10 °, and a hard dense layer is formed on this surface. Therefore, even when the hard dense layer is formed to be thin, the surface roughness of the hard dense layer is as small as the surface roughness of the aluminum alloy disk, so that the hard surface necessary to obtain a good surface state is obtained. The degree of polishing of the dense layer is reduced, and the polishing allowance of the hard dense layer is reduced.

When a medium is formed on the polished surface of the hard dense layer, a magnetic disk is obtained. In this magnetic disk, the magnetic properties in the circumferential direction are improved due to the concentric roughened surface of the aluminum alloy disk. In addition, due to the small surface roughness of the aluminum alloy disk, the surface properties (small waviness, surface roughness) of the magnetic disk are improved, so that the flying height of the magnetic head is reduced, and as a result, The recording density of the magnetic disk can be increased.

Further, since the surface roughness Ra of the portion corresponding to the CSS zone in the surface of the hard dense layer is 10 ° or more, the surface roughness of the CSS zone of the magnetic disk is large, and
0 ° or more, which prevents the magnetic head from sticking to the surface of the magnetic disk when the magnetic disk device is stopped.

Therefore, according to the magnetic disk substrate of the present invention, even when a hard dense layer such as a NiP plating film is formed thin on the surface, the polishing allowance of the hard dense layer after the formation is reduced. Further, the recording density of the magnetic disk can be increased, and the magnetic head can be prevented from sticking to the surface of the magnetic disk when the magnetic disk device is stopped.

Here, the reason why the surface roughness Ra of the aluminum alloy disk is less than 10 ° is that when the hardness is 10 ° or more, it is necessary to increase the polishing allowance of the hard dense layer after forming the hard dense layer. This is because the polishing allowance of the hard dense layer cannot be reduced.

That is, when tracking the magnetic head,
Particularly at high speed rotation, minute irregularities on the surface of the magnetic disk cause vibration of the magnetic head. In order to prevent this, the magnetic disk needs to have a smooth surface without such irregularities. Surface roughness Ra of aluminum alloy disk is 10
In the case of Å or more, unless the polishing allowance of the hard dense layer after the formation of the hard dense layer is increased, a magnetic disk having no such unevenness and a smooth surface cannot be obtained. It will not be possible to reduce the cost.

The reason why the surface roughness Ra of the portion corresponding to the CSS zone in the surface of the hard dense layer is set to 10 ° or more is as follows.
If the angle is less than Å, the surface roughness of the CSS zone of the magnetic disk is small, and Ra is less than 10 °. Therefore, it is not possible to prevent the magnetic head from being attracted to the surface of the magnetic disk when the magnetic disk device is stopped.

Surface roughness Ra of the aluminum alloy disk
Is less than 1 °, the degree of concentric surface roughening is small, and the degree of improvement in the magnetic properties in the circumferential direction of the magnetic disk is small. On the other hand, when the surface roughness Ra is 1 ° or more, concentric circles The degree of improvement in the magnetic properties in the circumferential direction of the magnetic disk due to the roughening is large. From such a point, it is desirable that the surface roughness Ra of the aluminum alloy disk be 1 ° or more and less than 10 ° (second invention).

The magnetic disk obtained by forming a medium on the magnetic disk substrate according to the present invention has excellent magnetic properties in the circumferential direction and a reduced flying height of the magnetic head. Thus, it is possible to prevent the magnetic head from sticking to the surface of the magnetic disk when the magnetic disk device is stopped (third invention).

In the present invention, the CS of the magnetic disk is
The S zone is the Conta located on the innermost circumference of the magnetic disk.
ct Start Stop zone. The portion corresponding to the CSS zone in the surface of the hard dense layer in the magnetic disk substrate is the surface of the hard dense layer corresponding to a region which becomes a CSS zone when a magnetic disk is obtained by forming a medium on the surface of the hard dense layer. Area.

The concentric shape of the aluminum alloy disk whose surface is concentrically roughened includes, but is not limited to, those in which the polished lines are completely round and their centers are the same. The meaning is that the eye is not a perfect circle but includes a substantially perfect circle or an ellipse whose centers are substantially the same.

The surface roughness Ra perpendicular to the tangent to the concentric circle is the surface roughness obtained by moving the stylus for measuring the surface roughness in the direction perpendicular to the tangent to the concentric circle and measuring the surface roughness. Degree Ra. If the concentric circles are perfectly perfect circles and their centers are the same, the radial surface roughness Ra, ie, from the center of the disk to the circumference (or from the circumference to the center of the disk) The surface roughness Ra is obtained when the surface roughness is measured by moving the stylus for measuring the surface roughness.

In the present invention, the hard dense layer is not particularly limited, and various layers can be used. For example, in addition to the NiP plating film, TiN, TiC, CrN, Cr
A surface treatment film (layer) such as C, NiCuP, NiWP, or a film capable of ensuring surface accuracy can be used. Furthermore, the method for forming these surface treatment films is not particularly limited, and various methods can be used, for example, ion plating, chemical vapor deposition, sputtering,
An evaporation method, an electrolytic plating method, an electroless plating method, a thermal spraying method, or the like can be used.

The method for setting the portion corresponding to the CSS zone in the surface of the hard dense layer to have a surface roughness Ra of 10 ° or more is not particularly limited. A method based on zone texture treatment for roughening the surface is preferred.

[0029]

[Table 1]

[0030]

EXAMPLE The surface of a 3.5 inch type aluminum alloy disk (substrate) that had been ground was polished using a polishing tape so as to be concentrically roughened. That is, concentric texture processing was performed. At this time, the surface was finished so that the surface roughness Ra in the direction perpendicular to the tangent to the concentric circle was 8 °.

Next, an electroless NiP plating film was formed on the surface of the polished aluminum alloy disk as a hard dense layer using a commercially available electroless NiP plating bath. Then this
Finish polishing was performed on the surface of the NiP plating film. At this time, N
The portion corresponding to the CSS zone in the surface of the iP plating film was roughened so that the surface roughness Ra became 10 ° or more. Thus, the magnetic disk substrate (No. 1) according to the example of the present invention was manufactured.

On the other hand, the surface roughness Ra in the direction perpendicular to the tangent line of the concentric circle is finished to be 10, 20, 100 °, and this is the same as the case of manufacturing the magnetic disk substrate according to the above embodiment except for this point. By the method described above, magnetic disk substrates (Nos. 2 to 4) according to comparative examples were produced.

Further, the surface roughness Ra of the portion corresponding to the CSS zone in the surface of the NiP plating film is set to be less than 10 °, and except for this point, the same as in the case of manufacturing the magnetic disk substrate according to the above embodiment. By the method, the surface roughness R of the substrate for the magnetic disk according to the comparative example (hereinafter referred to as the CSS zone equivalent portion)
a <10 °).

Further, the surface of a 3.5 inch type aluminum alloy disk (substrate) ground as described above is
Polishing is performed using a normal polishing method in which a random polishing pattern is formed without using a polishing tape, and the surface roughness Ra is 8,
Finished to be 10, 20, 100 mm. Next, an electroless NiP plated film was formed and the surface of the NiP plated film was finish-polished by the same method as described above for the polished aluminum alloy disk. Thus, the magnetic disk substrates (Nos. 5 to 8) according to the comparative example were manufactured.

With respect to the magnetic disk substrate according to the embodiment of the present invention and the magnetic disk substrate according to the comparative example, the surface roughness was measured, and the surface roughness Ra in the radial direction and the circumference were measured. The surface roughness Ra in the direction was determined. Table 1 shows the results.

After the surface roughness measurement, a 2,000-mm-thick Cr base film and a thickness of 2000 mm were formed on the surface of the magnetic disk substrate using an in-line DC magnetron sputtering apparatus.
A 400 mm Co _62.5 Ni ₃₀ Cr _7.5 magnetic film and a 100 mm thick C protective film were formed in this order to form a medium. Thus, a magnetic disk was manufactured. FIG. 1 shows a conceptual diagram of a cross-sectional structure of the magnetic disk. In FIG. 1, 1 is an aluminum alloy disk (substrate) and 2 is an electroless Ni as a hard dense layer.
The P plating film 3 indicates a medium.

The coercive force in the circumferential direction and the radial direction of the magnetic disk manufactured as described above was measured by a vibrating sample magnetometer (VSM). Table 1 shows the results. Further, the magnetic head was rotated at a high speed of 10,000 rpm using a low flying head, and the flying property of the magnetic head by tracking was investigated. Table 1 shows the results.

As can be seen from Table 1, among the magnetic disks manufactured using the aluminum alloy substrate for magnetic disk according to the comparative example as the aluminum alloy substrate for magnetic disk, those having Nos. The coercive force is the same as the coercive force in the radial direction, and is 1050 to 1100 Oe.
4 have a high coercive force in the circumferential direction and 1250 Oe.
This is because the surface of the aluminum alloy disk (substrate) was not concentrically roughened in Nos. 5 to 8;
In the case of No. 4, the surface of the aluminum alloy disk (substrate) was roughened concentrically.

However, in Nos. 2 to 4, traces of collision of the magnetic head against the surface of the magnetic disk during tracking were observed. This indicates that the flying height of the magnetic head cannot be reduced.

The magnetic disk (No. 1) manufactured by using the magnetic disk substrate according to the embodiment of the present invention has the above No. 2
As in the case of 4, the coercive force in the circumferential direction is high. In addition, no trace of the magnetic head colliding with the surface of the magnetic disk during tracking was observed. This indicates that the collision between the magnetic head and the magnetic disk does not occur even in the case of the high-speed rotation of 10,000 rpm, and the flying height of the magnetic head is reduced.

Further, the surface roughness Ra of the portion corresponding to the CSS zone
A magnetic disk manufactured using a substrate of less than 10 mm has a high coercive force in the circumferential direction as in the cases of Nos. 2 to 4 above, and shows a trace of the magnetic head colliding with the surface of the magnetic disk during tracking. However, the magnetic head was attracted to the surface of the magnetic disk when the magnetic disk device was stopped. On the other hand, a magnetic disk manufactured using the magnetic disk substrate according to the embodiment of the present invention (No. 1)
In the case of No. 1, the magnetic head did not stick to the surface of the magnetic disk when the magnetic disk device was stopped.

[0042]

According to the present invention, even when a hard dense layer such as a NiP plating film is formed thinly on the surface of an aluminum alloy disk at the time of manufacturing a magnetic disk substrate, the polishing allowance of the hard dense layer after the formation is reduced. Thus, the magnetic disk can be reduced in recording density and the recording density of the magnetic disk can be increased, and the magnetic head can be prevented from sticking to the surface of the magnetic disk when the magnetic disk device is stopped.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a cross-sectional structure of a magnetic disk.

[Explanation of symbols]

 1--Al alloy disk, 2--hard dense layer, 3--medium.

Claims (3)

[Claims] 1. A magnetic disk substrate comprising: an aluminum alloy disk whose surface is concentrically roughened; and a hard dense layer formed on the surface of the aluminum alloy disk. The surface roughness of the plate is less than 10 ° in surface roughness Ra perpendicular to the tangent to the concentric circle, and the surface roughness of the portion corresponding to the CSS zone in the surface of the hard dense layer is the surface roughness Ra. A substrate for a magnetic disk, wherein the substrate has a thickness of 10 ° or more. 2. The magnetic disk substrate according to claim 1, wherein the aluminum alloy disk has a surface roughness Ra of 1 ° or more and less than 10 °. 3. A magnetic disk formed by forming a medium on the magnetic disk substrate according to claim 1.