JPH03250424A - Magnetic disk - Google Patents

Abstract

PURPOSE:To obtain a magnetic disk excellent in CSS durability by specifying and optimizing the surface roughness so that the profile of roughness in the radial direction of the magnetic disk has a specified relation between the maximum depth and the maximum height from the arithmetic mean center line. CONSTITUTION:The magnetic disk has at least a magnetic layer formed on a disk rigid substrate which is subjected to texturing treatment in the circumferential direction. Surface roughness of the disk is measured in the radial direction to obtain the arithmetic mean as the center line L. The surface roughness is specified to have the relation of Rp/Rv>=0.6, wherein Rv is the maximum depth and Rp is the maximum height of the roughness profile from the center line L in the measured area. By specifying this relation, damages on a magnetic head or the magnetic disk can be reduced and CSS durability is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic disk (so-called hard disk) in which a magnetic layer is formed on a disk-shaped rigid substrate.

[Summary of the invention]

The present invention provides a value Rv from the arithmetic mean center line to the bottom of the deepest valley in the radial direction and a value Rp to the highest peak in the magnetic disk whose surface roughness is defined by texturing.
The aim is to improve C8S (contact start stop) durability by optimizing the relationship between the two.

(Prior art) For example, disk-shaped magnetic disks that can be randomly accessed are widely used as storage media in computers, etc., and in particular, aluminum alloys are used for the substrate.So-called hard disks have a high responsiveness. Due to its excellent storage capacity and other reasons, it is used as a fixed disk or an external disk.

By the way, in the above-mentioned magnetic disk (hard disk), from the viewpoint of running performance, durability, etc., it is necessary that the contact surface with the magnetic head has an appropriate surface roughness due to minute irregularities. The technique of controlling the surface roughness by lapping the surface of a rigid substrate in the circumferential direction and creating minute scratches is known as texturing.

In this case, the surface roughness of the magnetic disk is mainly restricted by the flying height of the magnetic head and the C8S characteristics. If the surface roughness is too large, it will cause a so-called head hit, and conversely, if the surface roughness is too small, the magnetic head will This results in the inconvenience that the coefficient of friction between the two ends increases.

Therefore, until now, the surface roughness of the magnetic disk surface has been evaluated using center line average roughness Ra, etc., and by optimizing this, the maximum frictional force with the magnetic head can be lowered, durability can be increased, and so-called sticking can be achieved. Resolving this issue is being considered.

(For example, Japanese Unexamined Patent Publication No. 6246429) [Problems to be Solved by the Invention] However, the inventors of the present invention repeatedly studied the C8S durability, which is the most important characteristic to be applied to a magnetic head, and found that the We have come to the conclusion that it is insufficient to simply specify the line average roughness, etc.

The present invention has been proposed based on the results of such studies, and an object of the present invention is to provide a magnetic disk that not only has a small coefficient of friction with respect to a magnetic head but also has excellent C8S durability.

[Means to solve the problem]

The inventors of the present invention have made extensive studies to achieve the above-mentioned object, and have discovered that the time during which frictional force acts between the magnetic head and the surface of the magnetic disk varies depending on the unevenness of the surface of the magnetic disk. Ta. Then, C3S applied to the magnetic head
A detailed study of the temporal change in the frictional force shows that when the value Rv from the arithmetic mean center line of the surface irregularities in the radial direction of the magnetic disk surface to the bottom of the deepest valley and the value Rp to the highest peak have a predetermined relationship. It was found that the time required for frictional force to work was shortened, and the best C8S characteristics could be obtained.

The present invention was completed based on the above findings, and provides a magnetic disk in which at least a magnetic layer is formed on a circumferentially textured disk-shaped rigid substrate. It is characterized in that the value Rv from the arithmetic mean center line of the surface unevenness in the radial direction to the deepest valley bottom and the value Rp to the highest peak satisfy the relationship Rp/Rv≧0.6.

Value R from the arithmetic mean center line of the above surface unevenness to the deepest valley bottom
As shown in Fig. 1, the value Rp from v to the highest peak is determined by calculating the arithmetic average of the heights of the surface irregularities in the measurement section and using this as the center line. It is measured as the depth to the bottom of a deep valley and the height from the center line to the top of the highest mountain within the measurement area.

These values Rv and Rp vary greatly depending on the amplitude distribution of the surface irregularities even if the center line average roughness and the like of the magnetic disk surface are the same.

In the present invention, by controlling the surface condition of the rigid substrate, the Rv in the surface unevenness of the magnetic disk surface,
The setting is made so that the relationship Rp or Rp/Rv≧0.6 is satisfied. The problem here is whether the surface is uneven or not, because it is the surface of the magnetic disk that actually comes into contact with the magnetic head.For example, if the surface of the magnetic layer is in direct contact with the magnetic head, the surface condition of the magnetic layer is the problem. However, if a carbon protective film is formed on the surface of the magnetic layer, it is necessary that the surface condition of the carbon protective film satisfy the above relationship.

At this time, the values of the center line average roughness Ra, maximum height R, and y are arbitrary, or if the surface is too rough, it will interfere with the running of the magnetic head and the electromagnetic conversion characteristics will deteriorate, so the center line Average roughness Ra is 20 nm or less, maximum height R□8
is preferably 200 nm or less.

The surface condition of the rigid substrate is controlled by texturing, and a preferred method for texturing is to rub a wrapping tape in the circumferential direction of the substrate to make minute scratches in the circumferential direction of the substrate. Here, you can change the type of wrapping tape (for example, surface roughness, etc.)
By combining treatments using different types of lapping chives, it is possible to control the values of Rv and Rp in the surface unevenness of the magnetic disk surface.

The substrate to be textured is a rigid substrate, such as an aluminum substrate, an aluminum alloy substrate, an aluminum substrate with N1-P plating, an aluminum alloy substrate,
Alumite-treated aluminum substrates, aluminum alloy substrates, glass substrates, plastic substrates made of materials such as polyetherimide, polycarbonate, polysulfone, polyethersulfone, polyacetal, and polyphenylene sulfide can be used.

On the other hand, the magnetic layer formed on the rigid substrate may be a magnetic powder film formed by coating a magnetic paint mainly composed of magnetic powder, a binder, etc., or a ferromagnetic metal material ( For example, Co-Ni alloy, Co-Cr-Ta alloy, C
It may be a metal thin film formed by forming an o-Cr-Ni alloy, etc.) by a thin film forming technique such as plating or evaporation sputtering, and there is no restriction at all.

Further, when forming a metal thin film as the magnetic layer, a base film may be formed as necessary. In this case, the material of the base film includes Bi, Cr, etc., and the film thickness is about tens to thousands of layers (for example, in the case of a Cr base film, 700 to 10
00 people).

Furthermore, a carbon protective film, a lubricant layer, etc. may be formed on the surface of the magnetic layer, if necessary. The type of lubricant used may be arbitrary, but perfluoropolyether-based lubricants are particularly preferred. Further, the thickness of the carbon protective film is preferably in the range of 200 to 500 layers, and the thickness of the lubricant layer is preferably in the range of 20 to 60 layers.

[Effect]

When the rotational speed of the magnetic disk is gradually increased as shown in Figure 2 (A) with the magnetic head in contact, C8S
The frictional force acting between the magnetic head and the magnetic disk surface at the start is as shown in FIG. 2(B). and,
At this time, the amount of damage applied to the magnetic disk or magnetic head is given by the integral value of the frictional force.

Here, the curve of the frictional force changes depending on the Rv and RpO values of the surface unevenness of the magnetic disk surface, and Rp
When the value of /Rv is small, the maximum frictional force F applied to the magnetic head does not change much, or the time t required for the frictional force to become zero as the magnetic head flies tends to become longer. This means that when the value of Rp/Rv becomes smaller,
The frictional force acting on the magnetic head tails off, indicating that the time it takes for the magnetic head to pull on the magnetic disk surface becomes longer.

Therefore, for example, if the surface roughness is increased in order to lower the maximum frictional force, the value of Rv will usually increase and Rp
/ The value of Rv becomes smaller, the time t until the frictional force becomes zero becomes longer, the integral value becomes larger, and as a result, C
8S durability will deteriorate.

On the other hand, in the present invention, since the value of Rp/Rv is set to 0.6 or more, the time t until the frictional force becomes zero is short, and C8S durability is ensured.

〔Example〕

The present invention will be explained below based on specific experimental results.

Experimental Example 1 The sample disk used in this experimental example was N1-
A magnetic layer, a carphone protective film, and a lubricant layer are sequentially formed on an aluminum substrate which has been plated with P and whose surface roughness has been changed by texturing. The magnetic layer is
It is a sputtered film of Co--Ni alloy, and has a thickness of 500 mm. Further, a bismuth underlayer film having a thickness of 100 mm was formed as an underlayer film for the magnetic layer. On the other hand, the thickness of the carbon protective film was 350 to 400, and the thickness of the lubricant layer was 40.

The lubricant used was perfluoropolyether (trade name Niphonpurin).

Tables 1-1 and 1-2 show Rp, Rv, Rp/Rv of each sample disk, and the time t until the maximum frictional force Fllll applied to the magnetic head becomes zero due to the floating of the magnetic head. Here, the sample disks shown in Table 1-1 correspond to examples of the present invention, and the sample disks shown in Table 1-2 correspond to comparative examples.

Note that Rp and Rv on each sample disc.

Each value of Rp/Rv was measured with the magnetic layer and carbon protective film formed, and the measurement length was 0.6 m.

In addition, when measuring the maximum frictional force F and time t, the magnetic disk rotation speed was set to 3600 rpm, and the time to rise to the rotation speed [T in FIG. 2(A)] was set to 4 seconds.

(Margins below) Table 1 Table 1-2 As is clear from these tables, when the surface condition of the magnetic disk is controlled and the value of Rp / Rv is set to 0.6 or more, the frictional force becomes zero. It can be seen that the time t required for this to occur becomes shorter, and the integrated frictional force becomes smaller.

Experimental Example 2 A sample disk was prepared in the same manner as in Experimental Example 1 using a Co--Cr--Ta alloy as the magnetic layer and a Cr base film.

The thickness of the Co-Cr-Ta alloy is 500 mm, and the thickness of the Cr base film is 700 mm. Note that Co is suitable for the magnetic layer.
The composition range of -Cr-Ta alloy is Cowcr yT
a g (x, y, z are all weight %), 4≦y≦20 0<z≦5

These sample discs are also Rp.

Rv, Rp/Rv, the maximum frictional force F applied to the magnetic head, and the time t until the frictional force becomes zero due to the floating of the magnetic head were measured. The results are shown in Table 2-1 and Table 2-2.
Shown below. Again, the sample disks shown in Table 2-1 correspond to examples of the present invention, and the sample disks shown in Table 2-2 correspond to comparative examples.

(Left below) Table 2 1 Table 2 The magnetic layer is made of a Co-Cr-Ta alloy (COs*Cr+tTa
x), it can be seen that by setting the value of Rp/Rv to 0.6 or more, the integrated frictional force becomes smaller.

Furthermore, when a similar experiment was conducted using COs4Cr 12T a 4 as the magnetic layer, the same results as in the case of C05gCr+Jai were obtained.

〔Effect of the invention〕

As is clear from the above description, in the present invention,
The value of Rp/Rv in the surface unevenness of the magnetic disk is 0.
Since it is set to be 6 or more, it is possible to reduce the damage (particularly the integral value of frictional force) applied to the magnetic head and magnetic disk, and it is possible to improve the C8S durability.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram for explaining Rp and Rv. FIG. 2(A) is a characteristic diagram showing the change in the rotational speed of the magnetic disk at the start of C8S, and FIG. 2(B) is a characteristic diagram showing the change in the frictional force at that time.

Claims (1)

[Scope of Claim] In a magnetic disk in which at least a magnetic layer is formed on a disk-shaped rigid substrate textured in the circumferential direction, A magnetic disk characterized in that a value Rv to the bottom of the valley and a value Rp to the highest peak satisfy the following relationship: Rp/Rv≧0.6.