JPH09231559A - Substrate for magnetic recording medium, its manufacture and magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a substrate for a magnetic recording medium capable of more reducing a contact area between a magnetic head and a magnetic disk by forming many ruggednesses on the substrate surface by an aggregate having the overlapping part of plural crater-like ruggednesses. SOLUTION: In this substrate 1 for the magnetic recording medium, the overlapping part 3 is formed by at least partly overlapping the projecting parts 6 of the two crater-like ruggednesses 2. The area of this overlapping part 3 is desirable to be small, and it is more preferable that a minor axis (r) of a circular arc which is a cross-sectional shape of the overlapping part 3 as formed if the substrate 1 for the magnetic recording medium is cut in a flat plane 4 or parallel to this flat plane 4 is less than a diameter D assuming the crater- like ruggedness 2 to be an approximate circle, and in particular, r<D/2 is most desirable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium substrate used for a magnetic recording medium mounted in a fixed magnetic disk device or the like, a method for manufacturing the substrate, and a magnetic recording medium using the substrate.

[0002]

2. Description of the Related Art Currently, personal computers generally have a built-in hard disk device as a recording device. Hard disk devices have two main types of operation. One is a so-called CSS method in which the magnetic head stays in contact with the magnetic disk when the apparatus is stopped and floats from the magnetic disk during operation. The other is the so-called CSS method when the magnetic head is outside the magnetic disk. It is a system of evacuating to the berth position and moving to the magnetic disk during operation.
Among these operation types, the CSS method can save space because it is not necessary to provide a place where the magnetic head is anchored in the hard disk device, and is advantageous for downsizing the device.

In a magnetic disk of a hard disk device adopting the CSS system, a textured surface is formed on the surface of the substrate of the magnetic disk to form a large number of irregularities.
The contact area between the magnetic head and the magnetic disk when the apparatus is stopped is reduced to prevent adsorption of the two. As a conventional texture processing method, a texture processing with a polishing tape or a texture processing by sputtering metal atoms has been performed. In addition to these texture treatments, recently, as disclosed in Japanese Patent Laid-Open No. 6-295433, the substrate surface is irradiated with a laser beam to form crater-like irregularities, and the crater-like irregularities at the peripheral edge are projected. Some departments have proposed a technique for anchoring a magnetic head.

However, in the method in which the magnetic head is anchored at the convex portion on the peripheral portion of the crater-like irregularities, the area of the convex portion contacting the magnetic head is relatively large, so that when the magnetic head floats above the magnetic disk. The friction energy is large, and the power consumption of the device may be large. Therefore, it is necessary to reduce the contact area between the magnetic head and the magnetic disk.

Therefore, an object of the present invention is to provide a substrate for a magnetic recording medium which can further reduce the contact area between the magnetic head and the magnetic disk. Another object of the present invention is to provide a magnetic recording medium having improved durability.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies and found that a large number of irregularities are formed on a substrate surface by an aggregate in which a plurality of crater-like irregularities have an overlapping portion. It has been found that the contact area between the magnetic head and the magnetic disk can be further reduced and the above object can be achieved.

The present invention has been made on the basis of the above findings, and in a magnetic recording medium substrate having a large number of irregularities formed on its surface, each of the irregularities has a plurality of crater-like irregularities overlapping with each other. The above object is achieved by providing a substrate for a magnetic recording medium, which is formed from an aggregated body.

The present invention also provides, as a preferable method for manufacturing the above-mentioned magnetic recording medium substrate, a crater-shaped substrate formed by one pulse laser beam when the substrate is irradiated with a plurality of pulse laser beams. The present invention provides a method for manufacturing a substrate for a magnetic recording medium, which comprises irradiating the pulsed laser beam so that the irregularities have overlapping portions.

Further, according to the present invention, as a magnetic recording medium using the magnetic recording medium substrate, at least a magnetic layer, a protective layer and a lubricant layer are provided in this order on the magnetic recording medium substrate. The present invention provides a magnetic recording medium.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A substrate for a magnetic recording medium according to the present invention,
A preferred embodiment will be described with reference to the drawings. Here, FIG. 1 is an enlarged perspective view of an essential part of the first embodiment of the magnetic recording medium substrate of the present invention, and FIG.
FIG. 3 is a sectional view taken along the line AA in FIG. 1, FIG. 3A is an enlarged plan view of an essential part of the first embodiment of the magnetic recording medium substrate of the present invention, and FIG. It is the sectional view on the AA line in 3 (a).

The magnetic recording medium substrate of this embodiment has a disk shape, and a large number of irregularities are formed on the surface thereof.
As shown in FIG. 1, each of the concavities and convexities is formed of an aggregate in which two crater-shaped irregularities 2 having substantially the same shape have an overlapping portion 3. That is, each of the irregularities on the surface of the magnetic recording medium substrate of the embodiment shown in FIG. 1 is composed of a plurality of crater-like irregularities 2 and 2, and the crater-like irregularities 2 and 2 have two overlapping portions. The crater-shaped irregularities 2 and 2 described above are collectively formed. Further, as shown in FIGS. 1 and 2, the overlapping portion 3 and the vicinity of the overlapping portion 3 have a convex shape to form a protrusion. In addition, as shown in FIG.
The crater-like unevenness 2 is formed of a substantially smooth surface.

As shown in FIGS. 1 and 2, the crater-like irregularities 2 are circles which are depressed inward from the flat surface 4 of the magnetic recording medium substrate 1 (that is, inward of the magnetic recording medium substrate 1). Shaped concave portion 5 and convex portion 6 protruding outward from the flat surface 4 so as to surround the concave portion at the peripheral portion of the concave portion 5.
Consists of The flat surface 4 is a mirror-finished surface, and its center line average roughness Ra is generally 0.3 to 1.2 n.
m.

As shown in FIG. 2, the crater-like irregularities 2 have a diameter D of 1 μm ≦ D ≦ 50 when they are approximated to a circle.
μm is preferable, and 1 μm ≦ D ≦ 20 μm is more preferable. As shown in FIG. 2, the diameter D is obtained by approximating the highest point of the convex portion 6 in the crater-like unevenness 2 as an outer circumference of a circle, and is measured by atomic force microscope (AFM) observation. It

In the magnetic recording medium substrate 1 of the embodiment shown in FIG. 1, at least a part of the convex portions 6 (peripheral portions) of the two crater-shaped concaves and convexes 2 and 2 overlap each other to form the overlapping portion. 3 is formed. The area of the overlapping portion 3 is preferably small, and more preferably, it is formed when the magnetic recording medium substrate 1 is cut in the flat surface 4 in parallel with the flat surface 4 as shown in FIG. The minor diameter r of the arc, which is the cross-sectional shape of the overlapping portion 3, is a diameter D when the crater-like unevenness 2 is approximated to a circle.
It is below, and it is particularly preferable that r <D / 2. When the overlapping portion 3 is in the above range, the area of the convex portion in which the magnetic head comes into contact with the magnetic recording medium can be reduced, and the power consumption at startup of the magnetic disk device can be reduced, which is preferable.

As shown in FIG. 2, the overlapping portion 3 or the vicinity thereof has a convex shape and forms a protrusion. The flying height of the magnetic head is such that the height H1 of the convex protrusion is 5 nm ≦ H1 ≦ 50 nm with reference to the average center line before the formation of the unevenness on the flat surface 4 of the magnetic recording medium substrate 1. Is sufficiently low and the durability of the magnetic recording medium is also good, and particularly 5 nm ≦ H1 ≦ 30.
It is preferably nm.

Further, as shown in FIG. 2, when the height of the peripheral portion (that is, the convex portion 6) of the crater-like irregularities 2 is H2, the flat surface 4 of the magnetic recording medium substrate 1 is formed. 2.5 nm based on the average centerline before unevenness formation
≦ H2 ≦ 40 nm, particularly 2.5 nm ≦ H2 ≦ 25 nm is preferable in order to control the height of H1 to a desired value. In addition, the concave portion 5 in the crater-like unevenness 2
Is the depth d of the flat surface 4 of the magnetic recording medium substrate 1.
5 nm based on the average centerline before the formation of irregularities in
<D <100 nm, especially 5 nm <d <60 nm to control the height of H2 to a desired value, and
It is preferable as a place for collecting lubricant.

Further, H1 and H2 are H1 / H2> 1.
1, in particular, 3> H1 / H2> 1.3 is preferable from the viewpoint that the power consumption at the start of the magnetic disk drive can be further reduced and the durability of the magnetic recording medium is improved. Above all,
It is preferable that 5 nm ≦ H1 ≦ 50 nm and H1 / H2> 1.1, because there are particular effects on the durability of the magnetic recording medium and the power saving of the power consumption at startup of the magnetic disk device.

As shown in FIG. 3A, in the magnetic recording medium substrate 1 of this embodiment, the crater-like irregularities 2 are formed.
.. are discretely present, that is, they are independent of each other at a predetermined interval, and a large number of irregularities are formed on the surface of the substrate 1. The aggregate 7 is formed by arranging the two crater-shaped irregularities 2 and 2 in parallel with the radial direction R of the disk (substrate) and having overlapping portions with each other. The aggregates 7 are radially arranged in multiple rows in the radial direction R of the disc (substrate) at a predetermined interval L. At the same time, the aggregates 7 are arranged in rows in a circumferential direction A of the disk (substrate) at a predetermined interval M, and are formed in multiple rows on a substantially spiral line.

As shown in FIG. 3B, in the radial direction R of the disk (substrate), the interval L between the convex protrusions formed in the overlapping portion between the adjacent aggregates 7 is: From the viewpoint of durability, L <200 μm is preferable, and more preferably 10 μm <L <150 μm.
And more preferably 20 μm <L <120 μm. On the other hand, in the circumferential direction A of the disk (substrate), the interval M between the adjacent aggregates 7 is M <200 as in the case of L.
From the viewpoint of durability, the thickness is preferably 10 μm, more preferably 10 μm <M <150 μm, and further preferably 20 μm <M <120 μm.

The irregularities formed from the aggregate 7 include a region including a portion where the magnetic head and the magnetic recording medium come into contact with each other when the magnetic recording medium is started and stopped (hereinafter, this region is referred to as a "head landing zone"). It is formed). In the head landing zone, the aggregate 7 is 45 to 10000 per 1 mm ² ,
Particularly, it is preferable that 70 to 2500 pieces are formed from the viewpoint of durability.

The material for the magnetic recording medium substrate is not particularly limited, and is generally made of a non-magnetic material. Specifically, the magnetic recording medium substrate is
It is composed of carbon such as glassy carbon, tempered glass, crystallized glass, aluminum and aluminum alloys, titanium and titanium alloys, ceramics, resins and composite materials thereof. Of the substrates made of these materials, the substrates made of brittle materials such as carbon and glass were susceptible to cracks and the like due to their brittleness in the texture treatment with the conventionally used polishing tape, According to the preferred method of manufacturing a substrate for a magnetic recording medium described later, it is possible to perform texture processing on a substrate made of such a brittle material without causing cracks or the like.

In the magnetic recording medium using the first magnetic recording medium substrate, when the magnetic disk device is stopped, the magnetic head comes into contact with the convex protrusion formed in the overlapping portion, so that the magnetic head and the magnetic The contact area with the recording medium is further reduced, and the power consumption required for starting the magnetic disk device can be reduced.

Next, the second magnetic recording medium substrate of the present invention
The third and third preferred embodiments will be described with reference to FIGS. 4 and 5, respectively. Here, FIG. 4 and FIG. 5 are enlarged plan views of essential parts in the second and third preferred embodiments of the magnetic recording medium substrate of the present invention, respectively. Regarding the magnetic recording medium substrate of the embodiment shown in FIGS. 4 and 5, only the points different from the magnetic recording medium substrate of the above-described first embodiment will be described, and the points that are not particularly detailed will be described. The detailed description of the magnetic recording medium substrate according to the first embodiment is applied as appropriate. 4 and 5
In FIG. 1, the same members as those in FIG. 1 are designated by the same reference numerals.

In the magnetic recording medium substrate of the second embodiment shown in FIG. 4, a large number of irregularities formed from an aggregate 7 in which three crater-shaped irregularities 2, 2, 2 are aggregated are formed on the surface thereof. Has been done. These crater-shaped concavities and convexities are arranged in a row in parallel with the radial direction R of the disk (substrate), and are gathered so that the convex portions at their peripheral portions have overlapping portions 3 with each other. As a result, two overlapping portions 3 and 3 are formed. And, the respective overlapping portions 3 and 3 and the vicinity thereof form a convex protrusion,
The height of the convex-shaped protrusion is higher than the height of the convex portion of the peripheral portion of the crater-shaped irregularities.

In the magnetic recording medium substrate of the third embodiment shown in FIG. 5, three crater-shaped irregularities 2, 2 and 2 are gathered, as in the magnetic recording medium substrate of the second embodiment. A large number of irregularities formed from the aggregate 7 are formed.
These crater-shaped irregularities have overlapping portions 3 at the convex portions of their respective peripheral portions, and the center points of the circles when the crater-shaped irregularities are approximated to circles are substantially located at the respective vertices of an equilateral triangle. Are gathered to do. As a result, three overlapping portions 3, 3, 3 are formed close to each other. By forming these three overlapping portions close to each other, the convex protrusions formed in these overlapping portions are overlapped and integrated with each other, and one having a maximum height at approximately the center of the equilateral triangle. To form a convex protrusion. Since the protrusion is formed by integrating the protrusions at the three overlapping portions,
Also, it is easier to fabricate the one having a larger ratio of H1 / H2 than the protrusion on the magnetic recording medium substrate of the second embodiment, and it is also easy to increase the height thereof.

In the magnetic recording medium substrates of the second and third embodiments, as in the magnetic recording medium substrate of the first embodiment, the magnetic head is formed in the overlapping portion when the magnetic disk device is stopped. Further, since the protrusions come into contact with each other, the contact area between the magnetic head and the magnetic recording medium is further reduced, so that the power consumption required for starting the magnetic disk device can be reduced.

Although the magnetic recording medium substrate of the present invention has been described above based on its preferred embodiment, the present invention is not limited to the above-described embodiment, and the number of crater-like irregularities in the aggregate and the aggregate thereof. The state, the arrangement of the aggregate, and the like can be appropriately changed within the range that does not impair the effects of the present invention. Further, the unevenness formed on the substrate surface is not limited to the landing zone and may be formed on other portions of the substrate surface. However, when unevenness is formed in the data zone, d ≦
It is preferably 20 nm.

Next, a preferred method of manufacturing the magnetic recording medium substrate of the present invention will be described with reference to the drawings, taking the method of manufacturing the magnetic recording medium substrate of the first embodiment as an example. Here, FIG. 6 is a schematic view showing an apparatus used in the method for manufacturing the magnetic recording medium substrate of the first embodiment.

In order to manufacture the magnetic recording medium substrate of the first embodiment, first, the surface thereof is mirror-polished using a known abrasive or the like so as to have a predetermined center line average roughness.
Next, a large number of concavities and convexities composed of the above-mentioned aggregate of crater-shaped concavities and convexities are formed in the head landing zone on the mirror-polished substrate surface. To form the irregularities, the laser processing device 20 shown in FIG. 6 is used.

The laser processing apparatus 20 shown in FIG.
A laser light source 21 composed of a YAG pulse laser (oscillation wavelength 1.06 μm), an attenuator 22 for adjusting the pulse laser light from the laser light source 21 to a predetermined output, a shutter 23 for appropriately blocking the pulse laser light, and a beam of the pulse laser light. Aperture 2 that narrows the diameter to a specified size
4, expander 25 that expands the luminous flux of pulsed laser light,
It has a first lens 26 for collimating the pulse laser light expanded by the expander 25 into parallel light, and a second lens 27 for condensing the pulse laser light collimated by the first lens 26 onto the substrate 31. ing. Further, the substrate 31 is adapted to be irradiated with pulsed laser light at a right angle. A half mirror 28 is arranged between the first lens 26 and the second lens 27, and a part of the pulsed laser light, which is substantially parallel light by the first lens 26, is part of the third lens 29.
It is led to. The third lens condenses the pulse laser light from the half mirror 28 and guides it to a power meter 30 that detects the output of the pulse laser light. Further, the laser processing apparatus 20 includes the spindle 3 for rotating the substrate 31 in the circumferential direction.
2 and a linear stage 33 for holding and fixing the spindle 32. The linear stage 33 is linearly movable in the radial direction of the substrate 31.

A method of forming irregularities using the above laser processing apparatus will be described. The irregularities are formed on the substrate by one pulse laser beam when the substrate is irradiated (simultaneously or sequentially) with a plurality of pulse laser beams. It is formed by irradiating the pulsed laser beam so that the crater-like concavities and convexities formed in 1) have overlapping portions. More specifically, first, the pulse period of the pulsed laser light and the rotation speed of the spindle are determined so that the distance between the processing spots of the pulsed laser light in the circumferential direction of the substrate becomes a predetermined distance M. This is easily determined from geometric calculations. By rotating the spindle at the determined number of revolutions and irradiating the pulsed laser light with the determined pulse period, as shown in FIG. 7A, the crater-like irregularities 2 are formed in a predetermined direction in the circumferential direction A of the substrate. The space M is formed. Next, the linear stage 33 is moved by a small distance in the radial direction of the substrate, and pulsed laser light is irradiated again at a predetermined pulse cycle under a predetermined rotation speed to further form crater-like irregularities, as shown in FIG. As described above, the two crater-shaped irregularities 2 and 2 are aggregated so as to form an overlapping portion in the convex portion of each peripheral portion (hereinafter, referred to as an aggregate 7).
This operation is called the first operation). Next, by moving the linear stage 33 in the radial direction of the substrate by a predetermined distance and irradiating a pulsed laser beam at a predetermined pulse period under a predetermined rotation speed, as shown in FIG. The crater-like unevenness 2 is formed in the direction at a predetermined interval L (hereinafter, this operation is referred to as a second operation). After that, by repeating the first operation and the second operation a predetermined number of times, as shown in FIG.
Many are regularly arranged.

The laser power of the pulsed laser beam, the pulse frequency, the processing spot diameter and the like in the above method are not particularly limited and can be appropriately selected depending on the material of the substrate, the degree of forming the unevenness and the like. Further, as the light source of the pulsed laser light, a CO ₂ laser, an excimer laser, a semiconductor laser or the like can be used in addition to the Nd: YAG laser.

According to the above method, there is no risk of cracks or the like even when unevenness is formed on the surface of a substrate made of a brittle material. Further, since the portion on the surface of the substrate where the unevenness is formed can be arbitrarily selected, the zone texture can be easily formed.

As an alternative to the above-mentioned method of forming irregularities, instead of using a single pulsed laser beam for irradiation, two pulsed laser beams are simultaneously irradiated so as to be close to each other, and two craters are thus irradiated. These two crater-like irregularities may be formed at the same time so that the concave-convex irregularities form an overlapping portion at least in the convex portions of the respective peripheral portions.

Further, as another method of forming the above-mentioned unevenness, a pulse laser is applied to the surface of the substrate through a mask material having an opening of a predetermined shape to form two crater-like unevenness. These two crater-like concavities and convexities may be simultaneously formed so as to form an overlapping portion at least in the convex portions of the respective peripheral portions.

The method of forming the unevenness is not limited to the above method, and any known method may be used.

Next, a magnetic recording medium using the magnetic recording medium substrate of the present invention will be described. The above magnetic recording medium comprises at least a magnetic layer, a protective layer and a lubricant layer provided in this order on the magnetic recording medium substrate of the present invention. That is, in the magnetic recording medium, at least a magnetic layer, a protective layer and a lubricant layer are provided in this order on the magnetic recording medium substrate on which the above-mentioned concavities and convexities are formed.

Examples of the magnetic layer include a metal thin film type magnetic layer formed by PVD (physical vapor deposition). As such a metal thin film type magnetic layer, a magnetic layer made of a Co alloy is preferable, and CoC is particularly preferable.
r-based alloys, and further CoCrPt-based alloys, especially CoC
rPtX (where X is B, Ta, Au, Ti, V, N
i, W, La, Ce, Pr, Nd, Pm, Sm, Eu,
Li, Si, Ca, As, Y, Zr, Nb, Mo, R
A magnetic layer made of an alloy represented by 1 or 2 or more metals selected from the group consisting of u, Rh, Ag, Sb and Hf) is preferable.

As the above-mentioned protective layer, those formed of substances usually used in magnetic recording media can be used without particular limitation, and a protective layer formed of a substance containing carbon or Si is preferably used. It Especially diamond like carbon, amorphous carbon, SiO ₂
And SiC are preferable from the viewpoint of excellent durability. The protective layer may be formed, for example, by sputtering in an atmosphere in which hydrogen or methane gas is mixed in argon gas, or may be formed from a carbon-based material by using CVD (chemical vapor deposition method). Good.

As the lubricant layer, those formed of substances usually used in magnetic recording media can be used without particular limitation, and particularly fluorine-containing lubrication having perfluoropolyether as a basic skeleton. A lubricant layer formed of a lubricant or a lubricant having a fatty acid skeleton is preferably used. Above all, a lubricant layer formed of a fluorine-containing lubricant such as Fomblin Z-03 or Z-dol (manufactured by Ausimont) is preferable.

In the magnetic recording medium, other layers may be provided, if necessary, in addition to the above layers. For example,
Between the substrate and the magnetic layer, enhance the adhesion between them,
In order to improve the magnetic characteristics of the magnetic recording medium, one or more underlayers made of a nonmagnetic metal or its alloy, an amorphous layer made of a nonmetal element, and the like can be provided. Examples of the nonmagnetic metal include transition metals such as Cr and Ti.

[0042]

The present invention will be described in more detail with reference to the following examples. However, it goes without saying that the present invention is not limited to such embodiments.

Example 1 Production of Magnetic Recording Medium Substrate The surface of an amorphous carbon substrate having a diameter of 2.5 ″ and a density of 1.5 g / cm ³ was precisely polished to reduce the center line average roughness Ra to 1 nm or less. After precision cleaning of the carbon substrate, laser processing was performed on the surface of the carbon substrate by the following procedure using the laser processing apparatus shown in Fig. 6 to form a large number of irregularities. Using an Nd: YAG laser, the processing spot diameter was set to about 20 μm, the Q switch frequency was fixed at 10 kHz, and the laser power was set in the range of 1 to 60 μW. The circumferential direction was controlled by the rotational speed of the spindle, and the radial direction was controlled by the moving amount of the linear stage.The laser processing area had a radius of 24 to 36 m from the center of the substrate. After setting the carbon substrate on the spindle, the number of revolutions of the spindle was set so that the distance M between the processing spots in the circumferential direction was 60 μm, and the pulse laser beam with the laser power set to 5 μW was used. The substrate was irradiated at right angles, and crater-like irregularities were formed at intervals of 60 μm in the circumferential direction of the substrate as shown in Fig. 7 (a) Next, the linear stage was moved by a minute distance and pulsed laser light was irradiated. Then, as shown in FIG. 7 (b), crater-shaped irregularities were further formed, and two crater-shaped irregularities were aggregated so as to form overlapping portions in the convex portions of the respective peripheral portions to form an aggregate. (First operation) Next, the distance L between the machining spots in the radial direction is 60 μ.
The linear stage was moved so as to be m, and pulsed laser light was irradiated to form crater-like irregularities as shown in FIG. 7C (second operation). After that, the first operation and the second operation are repeatedly performed, and as shown in FIG.
A large number of irregularities composed of the above-mentioned aggregates 7 were regularly arranged on the surface of the substrate.

With respect to the magnetic recording medium substrate thus obtained, the shape of the irregularities formed on the surface was observed by an atomic force microscope (AFM), and the height of the convex protrusions formed in the overlapping portion was observed. The height H1 and the height H2 of the peripheral portion of the crater-shaped irregularities were measured. As the AFM sample, a laser-processed portion cut out into about 10 × 10 mm was used. The field of view of the AFM was measured at 200 × 200 μm. Table 1 shows the results.

Manufacture of Magnetic Disk Next, the obtained magnetic recording medium substrate was precision cleaned, and then a magnetic disk was manufactured by the following procedure. (1) Using the above substrate, the ultimate vacuum of 1.0 × 10 ⁻⁷ Torr
It is introduced into a stationary opposed-type sputtering apparatus having the performance of. (2) The temperature of the substrate is 120 by the lamp heater.
The substrate is heated so that the temperature becomes ° C. (3) Ti layer as seed layer, Ar gas pressure 4 mTorr
A film having a thickness of 100 nm is formed by sputtering below. (4) As a base layer, a Cr layer is formed to a thickness of 50 nm by sputtering under an Ar gas pressure of 4 mTorr. (5) A CoCr ₁₃ Pt ₁₀ at% layer was formed as a magnetic layer by sputtering under an Ar gas pressure of 20 mTorr to a film thickness of 3
The film is formed to 0 nm. (6) As a protective layer, a C layer is formed to have a film thickness of 15 nm by sputtering under a mixed gas pressure (total pressure) of Ar and H _{2 of} 10 mTorr. (7) The substrate is taken out from the sputtering apparatus, and after tape burnishing, a fluorine-based lubricant (Fomblin Z-dol) is applied on the protective layer by dip coating (film thickness 2 nm) to obtain a magnetic disk.

The durability of the magnetic disk thus obtained was evaluated by the static friction coefficient after 100,000 CSS tests. Table 1 shows the results.

[Examples 2 and 3] A magnetic recording medium substrate was manufactured in the same manner as in Example 1 except that the laser powers were changed to 10 µW and 15 µW, respectively, and the obtained magnetic recording medium substrate was used. A magnetic disk was manufactured in the same manner as in Example 1. The same measurement as in Example 1 was performed on these magnetic recording medium substrates and magnetic disks. Table 1 shows the results.

[Embodiment 4] The processing spot diameter is about 10 μm.
A magnetic recording medium substrate was manufactured by the same operation as in Example 1 except for the above, and a magnetic disk was produced by the same operation as in Example 1 using the obtained magnetic recording medium substrate. The same measurement as in Example 1 was performed on the magnetic recording medium substrate and the magnetic disk. Table 1 shows the results.

[Embodiment 5] The processing spot diameter is about 10 μm.
Example 1 except that the laser power was 10 μW.
A magnetic recording medium substrate was manufactured by the same operation as in, and a magnetic disk was manufactured by using the obtained magnetic recording medium substrate by the same operation as in Example 1. The same measurement as in Example 1 was performed on the magnetic recording medium substrate and the magnetic disk.
Table 1 shows the results.

[Embodiment 6] The processing spot diameter is about 10 μm.
A magnetic recording medium substrate was manufactured in the same manner as in Example 1 except that the laser power was 10 μW and the distance between the processing spots in the radial direction was 80 μm, and the obtained magnetic recording medium substrate was used. A magnetic disk was manufactured in the same manner as in Example 1. The same measurement as in Example 1 was performed on the magnetic recording medium substrate and the magnetic disk. Table 1 shows the results.

[Embodiment 7] A magnetic recording medium substrate was manufactured in the same manner as in Example 1 except that the distance between the processing spots in the radial direction was 250 μm, and the obtained magnetic recording medium substrate was used. A magnetic disk was manufactured in the same manner as in Example 1. The same measurement as in Example 1 was performed on the magnetic recording medium substrate and the magnetic disk. Table 1 shows the results.
Shown in

[Comparative Examples 1 and 2] The same operations as those in Examples 1 and 2 except that the first operation was not performed and the laser processing was performed only by the second operation when the linear stage was moved in the radial direction. A magnetic recording medium substrate was manufactured in the above, and a magnetic disk was manufactured by the same operation as in Example 1 using the obtained magnetic recording medium substrate. The same measurement as in Example 1 was performed on these magnetic recording medium substrates and magnetic disks. Table 1 shows the results. Note that the magnetic recording medium substrate obtained in this comparative example does not have irregularities formed from an aggregate in which a plurality of crater-like irregularities have an overlapping portion.

[0053]

[Table 1]

As is clear from the results shown in Table 1, a magnetic recording medium substrate having a large number of concavities and convexities formed by an aggregate of two crater-like concavities and convexities having an overlapping portion was manufactured. Magnetic disk (Examples 1 to 1
In 7), it can be seen that the static friction coefficient is small and the durability is improved as compared with the magnetic disks (Comparative Examples 1 and 2) manufactured using the magnetic recording medium substrate on which such irregularities are not formed.

[0055]

According to the magnetic recording medium substrate of the present invention,
The contact area between the magnetic recording medium and the magnetic head using this is reduced, and the durability of the magnetic recording medium is improved.
Power consumption during operation is small. Further, according to the method for manufacturing a substrate for a magnetic recording medium, there is no possibility that cracks or the like will occur even when unevenness is formed on the surface of a substrate made of a brittle material. In addition, the zone texture can be easily formed because the portion where the unevenness is formed can be arbitrarily selected.

[Brief description of drawings]

FIG. 1 is an enlarged perspective view of a main part of a magnetic recording medium substrate according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA in FIG.

FIG. 3A is an enlarged plan view of an essential part of the magnetic recording medium substrate according to the first embodiment of the present invention.
3B is a cross-sectional view taken along the line AA in FIG.

FIG. 4 is an enlarged plan view of an essential part of a second preferred embodiment of a magnetic recording medium substrate of the present invention.

FIG. 5 is an enlarged plan view of an essential part in a third preferred embodiment of a magnetic recording medium substrate of the present invention.

FIG. 6 is a schematic view showing an apparatus used in the method for manufacturing the magnetic recording medium substrate of the first embodiment.

7 (a) to 7 (c) are schematic views showing a state of forming irregularities using the apparatus shown in FIG. 6, respectively.

[Explanation of symbols]

 1 substrate for magnetic recording medium 2 crater-like irregularities 3 overlapping portion 4 flat surface 5 concave portion 6 convex portion 7 aggregate

Claims (9)

[Claims] 1. A magnetic recording medium substrate having a large number of concavities and convexities formed on the surface thereof, wherein the concavities and convexities are each formed of an aggregate in which a plurality of crater-like irregularities have an overlapping portion. A magnetic recording medium substrate characterized by: 2. The magnetic recording medium substrate according to claim 1, wherein the overlapping portion and the vicinity of the overlapping portion have a convex shape. 3. The substrate for a magnetic recording medium according to claim 1, wherein the crater-like concavities and convexities have a diameter D in a circle approximation of 1 μm ≦ D ≦ 50 μm. 4. The height of the convex shape formed in the overlapping portion is H1, and the height of the peripheral edge portion of the crater-like irregularities is H1.
When 2 is set, 5 nm≤H1≤50 nm and H1 / H2
The magnetic recording medium substrate according to claim 2, wherein> 1.1. 5. The magnetic recording medium substrate according to claim 1, wherein the aggregates are discretely present. 6. The interval L between the convex shapes formed in the overlapping portion between the adjacent aggregates is L <2.
The substrate for a magnetic recording medium according to claim 5, which has a thickness of 00 μm. 7. The substrate for a magnetic recording medium according to claim 1, which is made of a brittle material. 8. A magnetic recording medium comprising at least a magnetic layer, a protective layer and a lubricant layer provided in this order on the magnetic recording medium substrate according to claim 1. 9. When irradiating a substrate with a plurality of pulse laser beams, the pulse laser beam is irradiated so that the crater-like irregularities formed on the substrate by one pulse laser beam have respective overlapping portions. A method of manufacturing a substrate for a magnetic recording medium, comprising: