JPH08221733A - Magnetic disk medium - Google Patents

Abstract

PURPOSE: To relieve the attraction of a magnetic head to a magnetic disk medium and to reduce frictional force due to contact by forming a 2nd base film contg. dispersed nonmagnetic particles whose particle size is almost equal to the spacing of the magnetic head in the surface direction on a 1st base film on a nonmagnetic substrate. CONSTITUTION: A Cr layer 7 is formed as a 1st base film on a soda lime glass substrate 6 as a nonmagnetic substrate and a 2nd base film 8 for forming ruggedness is formed on the Cr layer 7. The base film 8 contains nonmagnetic particles 9 blown to and dispersed in the surface and has a desired film thickness. A Cr layer is further formed as a middle layer 10 under a magnetic layer 11 and a magnetic film of a Co-Cr-Ta alloy is formed as the magnetic layer 11. A protective layer 12 of carbon is then formed as the top layer of a disk. The surface of the protective layer 12 has fine ruggedness formed by the 2nd under film 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk medium mounted in a magnetic disk device, and more particularly to a film structure of a magnetic disk medium having good adsorption characteristics and wear resistance against contact with a magnetic head.

[0002]

2. Description of the Related Art A magnetic disk device equipped with a magnetic disk medium (hereinafter abbreviated as a disk) has a rotation control mechanism, a recording / reproducing magnetic head slider (hereinafter simply referred to as a head), and a head positioning mechanism. The recording / playback processing mechanism is the main configuration. For its operation, a head loading method generally called a contact start stop method (hereinafter abbreviated as CSS) is used. When the rotation of the disk is stopped, the disk is pressed and brought into contact by the force of a lightly weighted gimbal spring that is a supporting mechanism of the head that faces the disk. On the other hand, at the time of recording / reproducing, the head floats away from the disk due to the viscous air flow generated near the surface due to the rotation of the disk, and recording / reproducing is performed in this state.

As described above, in the CSS system, the disks come into contact with the heads at the time of starting / stopping and slide on the surface of each other.
The head and disk must be in a relationship that can withstand this contact and sliding.

Further, due to the presence of water molecules existing in the air in the disk device, the head and the disk may be attracted to each other when the disk rotation is stopped, and a large frictional force may be generated when the head is floated when the device is started. As a result, there is a possibility that the head and the disk may contact and wear due to the gimbal destruction and the unstable flying of the head, which may deteriorate the recording and reproducing characteristics.

On the other hand, the storage capacity of a magnetic recording device in a computer system in recent years has been increasing year by year, and in connection with the increase in recording density per unit area of the disk, the outermost surface of the disk at the time of recording and reproducing. The gap between the head and the recording / reproducing element portion of the head, that is, the head spacing (hereinafter abbreviated as the flying height) is required to be smaller. However, this requirement for low flying height may cause both the disk and the head to come into direct contact with each other, or indirectly when dust is present, resulting in an increase in frictional force.
There is also the problem of damaging each other. Conventionally, aluminum alloy substrates have been widely used as substrates for disks. However, in response to the above-mentioned demand for higher density, many magnetic disk devices equipped with a disk using a glass substrate have been reported and put into practical use in recent years. The reason is that the glass substrate has no surface protrusion, is excellent in ultra-smoothness, is hard, and has few surface defects as compared with the aluminum substrate.

On the other hand, on the other hand, since the smoothness is excellent, the contact area between the head and the disk is large, and it is easy to adsorb, which causes an increase in frictional force. As a result, there is a problem in that the wear resistance including the CSS characteristics described above decreases. As a method for solving the above-mentioned problems, many publicly known examples in which the outermost surface of the disk is made uneven to reduce the contact area between the head and the disk have been reported. As an example of forming irregularities on the protective film of the disk, Japanese Patent Laid-Open No. 4-137216 discloses a method using chemical etching (chemical corrosion). In a high-density magnetic disk medium, it is necessary to make the distance between the magnetic recording layer on the lower surface of the protective film layer and the read / write element portion of the head as short as possible, but it is desirable that the film thickness of the protective film be as thin as possible. . In the technique for stably forming irregularities of nm order on the protective film without variation, it is necessary to secure the initial film thickness of several tens of nm and then to form the convex portion by etching or the like. Only the initial thick film remains. For this reason, during operation in which the head floats above the disk (during recording / reproduction), the head and the convex portion of the disk are constantly in contact with each other and wear occurs, which may reduce durability. Further, Japanese Patent Laid-Open No. 5-20659 discloses that clusters are scattered on the protective layer to form irregularities on the outermost surface of the disk. However, in this case, it is not desirable from the viewpoint of the electromagnetic characteristics of the disk (increase in reproduction noise, decrease in S / N ratio) because clusters of non-magnetic metal or oxide or nitride, which are foreign matter, are present on the magnetic layer. . In addition, the magnetic disk medium for forming irregularities on the disk surface must be provided in consideration of the flying height required by the mounted magnetic disk device by any method. There is no example.

[0007]

As described above, in order to cope with the narrowing of the head and the disk magnetic layer and to prevent the electromagnetic characteristics from being impaired, the physical quantity of the flying height of the head and the disk surface state is If such a relationship is not taken into consideration, an excellent operating environment between the magnetic disk medium and the magnetic head slider, which has a characteristic of reducing the frictional force with the head, especially the attraction force with the disk, cannot be obtained.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a magnetic disk medium having excellent durability and slidability.

[0009]

In order to solve the above-mentioned problems, the present invention forms a second underlayer in which non-magnetic particles are dispersed, not on the magnetic film, but on the first underlayer, and the surface is made uneven. The intermediate film, the magnetic film, and the protective film are sequentially laminated to form a magnetic disk medium structure in which unevenness is reflected up to the outermost surface.
Further, the particle size of the non-magnetic particles dispersed in the second underlayer varies depending on the flying height of the magnetic head slider in the mounted magnetic disk device, and the value is equivalent to the flying height. Further, the thickness of the second underlayer is 0.8 to 1.0 times the size of the non-magnetic particles.

[0010]

In the magnetic disk medium according to the present invention,
Chemically strengthened soda lime glass and alumino silicate
A chrome layer is provided on the first underlayer film on the glass, and a layer in which nonmagnetic particles are dispersed on the surface of the disk is formed as the second underlayer film on the surface. The non-magnetic particles appropriately make the disk surface uneven, and the unevenness is reflected even on the chromium layer and the magnetic layer as the intermediate film, and further on the surface of the protective film as the uppermost layer of the disk. According to the present invention, as the first effect, the uneven shape reduces the contact area with the air bearing surface of the head which is opposed during non-recording / reproducing, so that the attraction force can be reduced. Further, as the second effect, by providing the unevenness forming means on the underlayer of the magnetic layer, the protective film layer can be thinned without impairing the electromagnetic characteristics. Dispersing the particles in the magnetic layer creates a magnetic space and causes noise. It is possible to shorten the distance between the recording / reproducing element portion of the head and the outermost surface of the disk, that is, to reduce the flying height and achieve high density.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The entire embodiment will be described below with reference to FIGS. FIG. 2 is a schematic enlarged view of a head / disk cross section at the time of general non-recording / reproduction in the magnetic disk device. At the time of non-recording and reproduction, the disk 1 faces the head 2 facing
2 shows a state in which they are pressed by the force of the light weighted spring 3 and are in constant contact with each other, that is, a contact stop state. In this state, since the surface smoothness of both the head and the disk is excellent, an adsorption phenomenon is likely to occur between the disk and the head through the lubricant 4, and further, the water molecules (H ₂ O) 5 in the atmosphere may be absorbed. The chemical bond further strengthens the adsorption force, and a large frictional force is generated when the head floats during recording and reproduction. For this reason, in the present invention, minute irregularities are formed in the protective layer on the outermost surface on the disk side, the contact area between the head and the disk is reduced, and the suction force is reduced.

FIG. 1 is a schematic sectional view of an embodiment of a magnetic disk medium according to the present invention. As a non-magnetic base substrate,
Ra with dhalime or aluminosilicate glass
A soda lime glass substrate 6 having a (center average surface roughness) of 1 nm or less, a chemically strengthened outer diameter Φ65 mm, and a plate thickness of 0.64 mm, which has been subjected to ultrasonic cleaning, degreasing, and the like, was used.
Further, a chromium layer having a thickness of 500 nm is formed as the first base film 7 by sputtering. This chromium layer has a function of protecting the influence of water molecules on the surface attached in the above-mentioned glass substrate transportation and cleaning steps. When the magnetic disk device is accidentally dropped, an impact force of 200G to 300G is generated in the magnetic disk device. However, since this chromium layer has good adhesion and toughness, it also has the effect of relaxing the impact force applied to the disk, preventing damage such as dents, and protecting the recording / reproducing data. .

Next, a second base film 8 for forming irregularities on the disk surface is formed on the layer. This second undercoat film is formed by spraying non-magnetic particles 9 in a general sputtering device while discontinuously dispersing the non-magnetic particles 9 in a desired sputtering film thickness. The size of the non-magnetic particles depends on the gap between the head and the disk required by the disk device, that is,
It must be a size that takes into account the flying height. For example, in this embodiment, a disk mounted on a disk device having a flying height of 50 nm is assumed, and the maximum particle size is 50 nm.
(40 nm on average) The film thickness is 0.8 times that of 40 nm. This is because if the particle size exceeds the floating spacing value, the frequency of contact between the head and the convex portion on the outermost surface of the disk at the time of recording / reproducing becomes high, causing wear of both. Further, the film thickness is shown in FIG.
As shown in FIG. 4, the result of measuring the adsorption force after the operation of the device,
We have come to the conclusion that 0.8-1.0 times the particle size is desirable. The non-magnetic particles are silica (SiO ₂ ), and the sputter target plate is SiO ₂ .

Next, a chromium layer having a film thickness of 200 nm was further formed as the intermediate film 10 under the magnetic layer. This chromium layer is for reducing the impact force as well as for improving the magnetic characteristics (high coercive force, squareness ratio, etc.) as in the case of the above-mentioned first underlayer. The magnetic layer 11 is a cobalt-chromium-tantalum alloy magnetic film having a thickness of 50 nm. The uppermost protective layer 12 of the disk was made of carbon from the viewpoint of durability. The reason for this is that the heat generated by contacting the disk and head is
Bonn is liable to burn and is less likely to cause abrasion powder to be transferred to a disk or a head, and has durability in combination with Al ₂ O ₃ —TiC and CaTiO ₃ sliders, which are the mainstream of high density magnetic head materials. Because it is excellent. In this embodiment, carbon is used for the protective film, but it is not limited to carbon as long as similar performance can be obtained. As the lubricating film 13 applied to the protective film, a fluorocarbon-based liquid lubricant is applied to a thickness of about 7 nm.

In this way, the surface of the protective film of the disk thus laminated is successively covered with the above-mentioned second undercoat film to form the minute irregularities 14.
Is reflected. FIG. 3 is a diagram showing an example of the effect of this unevenness. This figure is not a single product, but is actually mounted on a magnetic disk device, and after operating for a certain period of time, the device was stopped and left for 24 hours. The cycle was repeated. Incidentally, the mounted disk is the one in which the relationship between the non-magnetic particle size and the film thickness in the above-mentioned second underlayer film is changed and its effect is verified. The attraction force is VCM (voice coil mode) which is the drive system of the head.
(15) A current was slowly passed through the device 15 and the current value at which the head started to move in the radial direction was converted to measure the adsorption force. The disk has a constant film thickness of 40 nm, and the maximum particle size of non-magnetic particles is sample A: 30 nm, B: 40 nm, C: 50 nm,
D: 4 types that were changed to 60 nm. The spacing of the head is 50 nm. The larger the particle size, the greater the effect of reducing the adsorptive power, but conversely, as shown in FIG. 4, the head dirt becomes larger with the 60 nm particle size of sample D. This is because the protrusions on the surface of the disk project too much, and the frequency of contact increases with head spacing of 50 nm. As a result, it is considered that the carbon abrasion powder does not burn out and is transferred to the head. This head dirt is
During recording / reproduction, the flying height of the magnetic head is remarkably reduced, and disk and head wear are increased. As a result, it becomes a fatal problem that destroys the data on the disk. As a result of repeating the above-mentioned examination, in order to satisfy both the above-mentioned attraction force and reduction of head dirt, the maximum particle size of the non-magnetic particles is made equal to the flying height, and the film thickness thereof is 0.8 times to 1 times. We have found that 0.0 times is desirable. In order to further verify this finding, next, the flying height is 60 nm and the film thickness is 0.8 times 48 n.
m, maximum non-magnetic particle size is sample B: 40 nm,
Discs of C: 50 nm, D: 60 nm and E: 70 nm were prepared and studied. The operating time of the disk device is 10
It is 00 hr, and the method of measuring the suction force is the same as the previous time. Table 1 is an example of the examination results in the present invention.

[0016]

[Table 1]

The suction force and head contamination are 1 before the operation of the device.
And is a standardized numerical value. In the relationship between the increase in head dirt and the attraction force, the reduction effect is contradictory, the maximum size of non-magnetic particles is the same as the flying height, and the disk with 0.8 times the film thickness is the best as in the previous case. I have come to the conclusion.

[0018]

When the magnetic disk medium having the layer structure of the present invention is used, the attraction force with the magnetic head is reduced during non-recording / reproduction. Moreover, since the frequency of contact with the head can be reduced during recording and reproduction, there is an effect of suppressing head contamination. Further, the gap between the head and the head can be narrowed, and a low-flying high-density magnetic disk medium capable of high reproduction output can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an embodiment of a magnetic disk medium of the present invention.

FIG. 2 is a schematic sectional view of a conventional magnetic disk medium at the time of non-recording / reproduction.

FIG. 3 is a graph showing the relationship between device operating time and suction force.

FIG. 4 is a graph showing the relationship between apparatus operating time and head contamination.

[Explanation of symbols]

 1 magnetic disk medium 2 magnetic head 3 light load spring 4 lubricant (lubrication film) 5 water molecules 6 soda lime glass substrate 7 first underlayer film 8 second underlayer film 9 non-magnetic particles 10 intermediate film 11 magnetic layer (magnetic Film) 12 Protective layer (protective film) 13 Lubricating film 14 Micro unevenness 15 VCM (voice coil motor)

Claims (3)

[Claims] 1. A magnetic disk medium comprising a base film, an intermediate film, a magnetic film, and a protective film, which are sequentially formed on a non-magnetic substrate, and has a particle size equivalent to that of magnetic head levitation spacing in the in-plane direction on the front base film. A magnetic disk medium in which non-magnetic fine particles having the above are dispersed and a discontinuous minute projection film is formed as a second base film. 2. The magnetic disk medium according to claim 1, wherein the thickness of the second underlayer film is 0.8 to 1.0 times the size of the non-magnetic particles. 3. The magnetic disk medium according to claim 1, wherein the first underlayer and the intermediate layer are chromium layers.