JPH1196547A - Magnetic recording medium and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form projections of a uniform size and shape in a short time by irradiating the prescribed range of a glass substrate surface with a laser beam, thereby simultaneously forming the plural projections. SOLUTION: The exit light emitted from a kaleidomirror is reflected by a reflection mirror. This reflected light advances toward the substrate D held in a substrate holder 13 and passes a lens, by which the light is made into parallel light beams having a spread of a certain range. When the prescribed range of the surface of the substrate D held in the substrate holder 13 is irradiated with these paralleled laser beams, energy is applied without unevenness on the substrate surface within the range irradiated with the laser beams. The temp. elevation by the irradiation with the laser beams occurs only in the extremely shallow regions near the surface of the substrate D and, therefore, the projecting parts after the irradiation are immediately cooled by the outdoor air or thermal diffusion and the crystal grain parts and amorphous parts are cured without the decrease in their volume, by which the plural projections are formed on the substrate D surface.

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 used in a magnetic disk drive and the like and a method for manufacturing the same, and more particularly, to a magnetic recording medium having excellent CSS characteristics.
And a manufacturing method capable of efficiently manufacturing the magnetic recording medium.

[0002]

2. Description of the Related Art The progress of high-density magnetic recording has been steadily increasing, and the speed of improving the recording density of a hard disk drive (HDD), which was once said to be 10 times in 10 years, has recently been 100 times in 10 years. Voices have also been heard.
For the HDD, a CSS (contact start / stop) system, which is basically called a Winchester style and has a basic operation of contact sliding, head floating and contact sliding between a magnetic recording medium and a magnetic head, is mainly adopted. Although this system is a revolutionary one that has rapidly accelerated the increase in the recording density of HDDs, it has also led to serious tribological issues. HD
The recent improvement in recording density in D is accompanied by an increase in the rotation speed of the magnetic recording medium and a decrease in the flying height of the magnetic head. The demand for smoothness is currently increasing.

The key to improving the sliding durability between the magnetic head and the magnetic recording medium lies in the reduction of the coefficient of friction. In terms of the magnetic recording medium, the conventional topcoat technology has been studied (diamond-like carbon (DLC) protection). It has been studied to reduce the coefficient of friction by roughening the surface of the magnetic recording medium along with the film and various kinds of applied lubricants. This is called texture processing, and the surface of the substrate is roughened to form irregularities on the surface of the magnetic recording medium, reducing the contact area between the magnetic head and the magnetic recording medium, lowering the friction coefficient, and The purpose is to increase CSS durability and stability. This texture processing is an important elemental technology of the magnetic recording medium manufacturing technology.

[0004] The above-mentioned texture technique is properly used depending on the material of the substrate. When texturing is performed on a NiP-coated Al substrate or the like, a method of forming irregularities by mechanical polishing using a polishing powder or the like is mainly used. Used. In the case where a glass substrate is used, lithography or an etching technique that combines the lithography and a printing technique has been proposed as a texture technique, and some of them have been put to practical use.

In the texture technology, it is important to increase the production efficiency in addition to the precise unevenness control. However, the two are often in an antagonistic relationship, and particularly, as described above, the increase in the recording density of the HDD is surprisingly rapid. In the current situation of progressing, the above-mentioned texture technique is not only unable to satisfy the demand, but also exposes various problems that can no longer be covered by accumulating ideas and improvements.

[0006] For example, the mechanical polishing method is already near the limit of fine processing control, and has encountered fundamental difficulties not only in the height difference of unevenness but also in the precise control of the texture area which is important in zone texturing and the like. . Specifically, there may be a problem that irregularities (over-polishing, burrs, etc.), which occur at a fixed rate and show a height difference outside a predetermined range, and a decrease in CSS characteristics due to blurring of a texture boundary or the like. In addition, although the lithographic method has no problem in terms of unevenness level control, the complexity of the process is unavoidable, which may cause a reduction in production efficiency.

Further, in order to achieve high recording capacity and high quality of the HDD, high cleanliness of the magnetic recording medium manufacturing environment is indispensable. This is the ultimate task. From this viewpoint, it is desirable that the manufacturing process is a dry process, which is a system in which impurities are hardly mixed.

[0008] It can be said that an attempt to apply laser light to material processing and measurement started from the beginning of the invention of the laser, but the recent development of laser light sources has brought about remarkable improvements in basic characteristics and handling properties. ,
It forms a wide base of application technology up to precise measurement. Laser ablation (erosion) or laser etching, which forms a material by laser light or processes a material surface, is a technology that has been actively studied since the 1980s. In recent years, there has been a great interest in texture technology (for example, US Pat. No. 5,620,221, Japanese Patent Application Laid-Open No. 62-209).
788, JP-A-3-272018, JP-A-7-182655, and JP-A-8-129949.

In the laser texture processing, usually, a pulsed laser beam is irradiated onto the substrate surface after squeezing the laser spot size to several μm to several tens μm to form a very small projection at the irradiation position. By performing the irradiation of the pulse laser beam while shifting the irradiation position on the substrate, projections are formed one by one on the substrate surface, and a large number of projections are formed in a predetermined region of the substrate surface. Laser texture technology can not only accurately set the height of the protrusions, the interval between the protrusions, the formation position, etc., but also can prevent impurities from being mixed into the magnetic recording medium because it is basically a dry process. There is an advantage that it becomes possible.

As for a method of performing texture processing on a NiP-plated Al substrate using a laser, effective methods have been proposed in the above publications and the like, and some of the methods have been successfully commercialized in a mass production stage. ing. For laser texture processing of NiP-plated Al substrate, normal wave of YAG laser (wavelength 1.06 μm), second harmonic wave (wavelength 0.53 μm),
Alternatively, laser light from an Ar laser (wavelength 0.33 to
0.53 μm) is used.
No. 72018 discloses that the Nd-
YAG laser (wavelength 1.06 μm, oscillation frequency 12KH
z), crater-like projections having a diameter of 2.5 to 100 μm are formed with NiP plating Al
A method for forming on a substrate is described.

In recent years, a glass substrate has been widely used instead of an Al substrate as a substrate having high surface hardness and excellent durability. Laser light having a wavelength generally used in texturing on the Al substrate has a low absorptivity to silicon oxide (SiO ₂ ), which is a main component of glass, and therefore has a high absorptivity of silicon oxide in texturing to a glass substrate. Long wavelength, for example, 5 μm
Many methods using the above laser light or a laser light having a short wavelength, for example, 0.3 μm or less have been proposed.

For example, Japanese Patent Application Laid-Open No. Hei 7-182655 discloses a method of performing texture processing on a glass substrate surface using a CO ₂ laser and a laser beam having a long wavelength (10.6 μm). Also, Japanese Patent Application Laid-Open No. 6-295433
In the publication, a non-metallic substrate such as a glass substrate is irradiated with an ultraviolet laser beam having a short wavelength (0.248 μm), and a convex portion composed of a deposit of atoms and molecules of the non-metallic substrate is formed by ablation. A method for performing the processing is disclosed.

[0013]

However, the above-mentioned texture technique has the following problems. As described above, the laser texture technique generally performs pulse laser beam irradiation while shifting the irradiation position on the substrate, thereby forming projections one by one on the substrate surface, and forming a large number of protrusions on a predetermined region of the substrate surface. A projection is formed. For this reason, there has been a problem that the operation requires a long time and the production efficiency is low.

In general, when the diameter of a projection formed by texture processing increases, the impact applied to the head when the head comes into contact with the projection during CSS tends to increase, and the CSS characteristics of the magnetic recording medium tend to deteriorate. is there. For this reason, it is important to keep the diameter of the projections below a certain value in order to enhance the CSS characteristics of the magnetic recording medium. To reduce the diameter of the protrusion in laser texturing, a method of reducing the laser spot size is effective. The laser spot size is approximately defined as (laser spot size) = 4 × (focal length) × (wavelength) / (π × incident beam diameter). Therefore, in order to reduce the laser spot size, the focal length, the wavelength, and the diameter of the incident beam may be increased.

However, it is often difficult to reduce the laser spot size to a certain value or less in a method using a long-wavelength laser beam when performing laser texturing on a glass substrate. For example, Japanese Patent Application Laid-Open No.
In the method using a CO ₂ laser described in Japanese Patent No. 182655, it is difficult to reduce the laser spot size to 50 μm or less because the wavelength of the laser light is large, and there is a certain lower limit to the diameter of the protrusion that can be formed. . In the above publication,
Although it is reported that the diameter of the formed protrusion is smaller than the laser spot size, it is extremely difficult to reduce the diameter of the protrusion to 10 μm or less even if the laser spot size is minimized as much as possible. This is because, if the focal length, the incident beam diameter, and the like are adjusted so that the diameter of the projection becomes smaller, the depth of focus becomes shallower in inverse proportion to the square of the diameter.

In a method using a laser beam having a short wavelength, for example, a method using an ultraviolet laser disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 6-295433, the laser spot size is reduced because the laser beam has a short wavelength. However, when the repetition frequency is increased, the output tends to fluctuate, that is, there is a problem that the repeatability is reduced, and the height of the formed projections is likely to vary, and a magnetic recording medium having excellent CSS characteristics is obtained. There was a problem that it was difficult to manufacture efficiently. As described above, when performing the laser texturing on the glass substrate, it is difficult to efficiently manufacture a magnetic recording medium having excellent CSS characteristics while keeping the diameter of the projections to a certain level or less and making the projection height uniform. Met. The present invention has been made in view of the above circumstances, and
It is an object of the present invention to provide a magnetic recording medium having excellent S characteristics and a manufacturing method capable of efficiently manufacturing the magnetic recording medium.

[0017]

According to a method of manufacturing a magnetic recording medium of the present invention, a laser beam is applied to a predetermined area of a surface of a crystallized glass substrate having a structure in which a number of crystal grains are separated from each other by an amorphous portion. Irradiation forms a plurality of protruding structures in which crystal grain portions or amorphous portions protrude from the substrate surface on the substrate surface in the laser light irradiation range. It is preferable that the laser beam has a uniform energy density, and has a wavelength of 200 to 6 nm.
It is preferably set to 00 nm or 5000 to 12000 nm. Further, the magnetic recording medium of the present invention has a structure in which a large number of crystal grains are separated from each other by an amorphous portion. The present invention is characterized in that a shape-like structure is formed. The grain size (average grain size) of the crystal grain portion is 0.1.
It is preferable that the thickness be 1 to 5.0 μm. The number of crystal grains per unit area of the substrate is 1,000 to 100,000,000.
It is preferable to set the number of pieces / mm ² .

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a method for manufacturing a magnetic recording medium according to the present invention will be described below with reference to FIGS. FIG. 1 shows an apparatus used for carrying out an embodiment of a method for manufacturing a magnetic recording medium according to the present invention. This apparatus comprises a laser light source 11 and the energy of laser light emitted from the laser light source 11. It comprises a kaleidoscope 12 for making the density uniform, and a substrate holding device 13 for holding a substrate D to be subjected to texture processing.

The laser light source 11 used here has a wavelength of 200 to 600 nm or 5000 to 1200.
It is preferable to use a laser that can emit a laser beam of 0 nm. Specific examples include CO ₂ laser, C
An O laser, a YAG laser, or the like can be used.

The reason why the preferable wavelength range of the laser light is indicated is as follows. Although laser light having a wavelength of less than 200 nm has a good absorptivity to glass, lasers emitting laser light having a wavelength of less than 200 nm often have poor stability, and it is difficult to stably produce a magnetic recording medium. Is not preferred. Over 600 nm, 5
When a laser beam having a wavelength of less than 000 nm is used, the absorptivity to glass is low, protrusions of a sufficient size cannot be formed, and the CSS characteristics of the obtained magnetic recording medium deteriorate.

A laser beam having a wavelength exceeding 12000 nm has a good absorptance with respect to glass but has a wavelength of 12000 nm.
Many lasers emitting laser light having a wavelength exceeding 2,000 nm are inferior in stability, such as lead compound semiconductor lasers that operate only at extremely low temperatures (15 to 90 K), so that a magnetic recording medium can be stably manufactured. It is not preferable because it becomes difficult.

The kaleidoscope 12 is an optical device for converting laser light into parallel light having a uniform energy density. As shown in FIG.
Callide mirror 21 for multiple reflection and parallelization of incident light
And a reflection mirror 22 for changing the direction of the light emitted from the callide mirror 21, and a lens 23 for adjusting the optical path of the light reflected from the reflection mirror 22 is provided on the outer periphery of the main body 20. The substrate holding device 13 is configured to be able to rotate a substrate to be subjected to texture processing at a predetermined rotational speed in a circumferential direction.

Next, taking the case where this device is used as an example,
One embodiment of a method for manufacturing a magnetic recording medium according to the present invention will be described. First, the substrate D is held by the substrate holding device 13 and rotated at a predetermined rotation speed, for example, 25 to 1000 rpm.

As the substrate D, a crystallized glass substrate such as a lithium silicate crystallized glass is used. A commercially available product suitable as the crystallized glass substrate is TS-10 manufactured by Ohara Corporation. Crystallized glass is a polycrystal in which crystals are precipitated inside the glass by heating the glass, and has a structure in which many crystal grain parts are separated from each other by amorphous parts. As the crystallized glass substrate D used here, it is possible to use a substrate in which the grain size of the crystal grain portion, the number per unit substrate area, and the like are appropriately set by adjusting the manufacturing conditions such as the heating temperature during crystallization. preferable. The grain size (average grain size) of the crystal grain portion is 0.1.
It is preferable that the thickness be 1 to 5.0 μm. The number of crystal grains per unit area of the substrate is 1,000 to 100,000,000.
It is preferable to set the number of pieces / mm ² .

When the grain size of the crystal grain portion is less than 0.1 μm, the height difference between the irregularities on the surface of the magnetic recording medium is insufficient, and the CS
In S, the contact area between the head and the medium increases, and the magnetic head is more likely to be attracted to the magnetic recording medium. On the other hand, when the particle size exceeds 5.0 μm, the maximum surface roughness of the magnetic recording medium becomes large, and head crash is likely to occur. Further, the number of the crystal grains per unit area is 1000 /
If it is less than mm ² or more than 100,000,000 pieces / mm ² , the height difference of the unevenness on the surface of the magnetic recording medium is insufficient, and the magnetic head is likely to be attracted to the magnetic recording medium.

Next, the laser light from the laser light source 11 is incident on the kaleidoscope 12. As the laser light, a laser light having a wavelength of 300 to 600 nm, for example, YAG
When using the second harmonic (532 nm) of the laser,
Cr, Co, M
It is preferable that the glass substrate be colored by adding an appropriate amount of a pigment containing n or the like to increase the laser light absorption.

The laser light entering the kaleidoscope 12 enters the kaleidoscope 21 from the entrance 21a, and travels toward the exit 21b while being repeatedly reflected on the inner wall thereof. At this time, the laser light is emitted from the emission port 21b as parallel light having a uniform energy density while being reflected multiple times in the callide mirror 21.

Light emitted from the callide mirror 21 is reflected by a reflection mirror 22, and the reflected light is reflected by a lens 23.
And proceeds toward the substrate D held by the substrate holding device 13. Here, the laser light passing through the lens 23 becomes parallel light having a certain range, for example, a range of 2 to 20 mm square.

The collimated laser beam is applied to a predetermined area on the surface of the substrate D held by the substrate holding device 13, for example, from 2 to
Irradiation is performed on a 20 mm square area. When the substrate D is irradiated with the laser beam, energy is applied to a very shallow region near the surface of the substrate D, and the temperature of the crystal grain portion and the amorphous portion in this portion increases. At this time, since the laser light has a uniform energy density, energy is imparted to the substrate surface within the laser light irradiation range without bias.

In general, glass has the property of softening as the temperature rises and increasing in volume due to thermal expansion, and hardening as it cools from this state without reducing the volume. In general, it is known that, in a polycrystalline material such as crystallized glass, physical properties such as a coefficient of thermal expansion often differ between a crystal grain portion and an amorphous portion.

When the temperature of the crystal grain portion and the amorphous portion in the substrate D rises, they soften and increase in volume due to thermal expansion and the like. At this time, of the crystal grain portion and the amorphous portion, those having a large volume change rate protrude more from the substrate surface. Since the temperature rise occurs only in a very shallow region near the surface of the substrate D due to the laser light irradiation, the protruding portion after the end of the laser light irradiation is immediately cooled by the outside air or thermal diffusion, and the crystal grain portion and the amorphous portion Is cured without reducing its volume, whereby a plurality of protrusions are formed on the surface of the substrate D.

The rotation of the substrate D irradiates the laser beam without any deviation in the circumferential direction of the substrate D, and a projection is formed on the surface of the substrate in the irradiation range to obtain a textured substrate. At the time of the laser beam irradiation, the laser beam is shaped into a fan shape with the circumferential direction coinciding with the substrate circumferential direction using a mask (not shown), and the laser beam irradiation amount per substrate area is biased in the substrate radial direction. It is preferred that this does not occur. Further, the laser light may be a continuously oscillated laser beam or a pulsed laser beam.

A non-magnetic underlayer made of Cr, Cr / Ti alloy, a magnetic layer made of Co / Cr alloy, Co / Cr / Ta alloy, carbon, etc. Is formed by a technique such as sputtering, vacuum deposition, ion plating, and plating. Further, a lubricating layer made of perfluoropolyether (PFPE) or the like may be provided on the protective layer. Since the magnetic recording medium obtained in this way has been subjected to texture processing on the substrate, it has irregularities on its surface.

FIG. 3 shows an example of a magnetic recording medium manufactured by the above method. In the magnetic recording medium shown here, a crystal grain portion 1 near a surface protrudes from the surface of a substrate D on a surface of a crystallized glass substrate D having a structure in which crystal grain portions 1 are separated from each other by an amorphous portion 2. No. 3 is formed. In the magnetic recording medium of this example, the projections 3 are formed by the crystal grain portions 1 protruding from the surface of the substrate D. Conversely, the amorphous portions 2 protrude from the surface of the substrate D. The protrusion may be formed by.

In the above manufacturing method, a plurality of projections are simultaneously formed in the laser beam irradiation range by irradiating a predetermined range on the surface of the glass substrate D with the laser beam. Since the plurality of protrusions are formed under certain conditions, the size of the protrusions due to the fluctuation of the laser light output is smaller than those formed by the conventional method of forming the protrusions one by one on the substrate surface. It has a uniform size and shape without any variation in shape. Further, in the above method, since a plurality of protrusions are simultaneously formed within the laser beam irradiation range, the substrate can be textured in a short time. Further, by adjusting the production conditions of the crystallized glass substrate, for example, the setting of the heating temperature during crystallization, etc., the particle size of the crystal grain portion, the number per unit substrate area, etc., the shape, size, unit substrate The number per area and the like can be arbitrarily set. Therefore, protrusions having a uniform height and a small diameter are formed on the surface of the magnetic recording medium, thereby enabling a magnetic recording medium having excellent CSS characteristics to be manufactured, while improving productivity and reducing manufacturing costs. be able to.

Further, by making the energy density of the laser beam uniform, the energy given to the substrate within the laser beam irradiation range can be made uniform. For this reason, the height of the projections formed in the irradiation range can be further uniformed. Therefore, C of the magnetic recording medium
The SS characteristics can be further improved.

[0037]

【Example】

Example 1 A magnetic recording medium was manufactured using the apparatus shown in FIG. Using a CO ₂ laser as the laser light source 11, a repetition frequency of 5 kHz, a pulse width of 30 μsec, and a wavelength of 1
A 0.6 μm pulse laser beam was passed through the kaleidoscope 12 to make the energy density uniform, and then irradiated onto the substrate surface.

As this substrate, crystallized lithium silicate glass (TS-10, manufactured by OHARA CORPORATION, component ratio: 75% silicon oxide, 10% lithium oxide, 4% aluminum oxide)
%, Magnesium oxide 2%, phosphorus pentoxide 2%)
Crystal grains having a diameter (average value) of 0.5 μm, a number per substrate unit area of 1,000,000 / mm ² , an average surface roughness Ra of 7 °, and a maximum surface roughness Rmax of 80 ° with a diameter of 65 mm. Was used. The substrate rotation speed during laser light irradiation was 500 rpm, and the irradiation time was 2 seconds. The laser power on the substrate was 40W. The laser light irradiation position was in a range of a radius of 12 to 16 mm on the substrate. The laser beam was irradiated with a fan-shaped beam so that adjacent irradiation positions did not overlap.

As a result of the above operation, a projection having a diameter of 0.5 to 1.0 μm was formed in the laser beam irradiation range on the substrate surface.
A substrate having a18 ° and Rmax of 250 ° was obtained.

On the substrate obtained by the above operation, a 100 nm thick underlayer made of Cr, a 20 nm thick magnetic layer made of a CoCrTa alloy, and a 20 nm thick carbon
m protective layers were sequentially provided by sputtering, and a lubricating layer having a thickness of PFPE material was provided thereon to obtain a magnetic recording medium. For the obtained magnetic recording medium, 1000
CSS for measuring the friction value after performing 0 times of CSS using a CSS tester (KT501, manufactured by Koyo Co., Ltd.)
A characteristic test was performed.

Example 2 CO ₂ was used as the laser light source 11.
Example 1 was performed using a laser shown in FIG. 1 under the conditions of a repetition frequency of 50 kHz and a pulse width of 10 μsec.
Laser light irradiation was performed on the same substrate as that used in the above.
The laser beam irradiation position was the same as in Example 1. The substrate rotation speed at the time of laser beam irradiation was 1000 rpm, and the irradiation time was 5 seconds. The laser power on the substrate was 20W. As a result of the above operation, the laser beam irradiation range is set to 0.5 to 1.
A projection of 0 μm is formed, and Ra16Å, Rmax200
A substrate that became Å was obtained. On this substrate, an underlayer, a magnetic layer, a protective layer, and a lubricating layer were provided in the same manner as in Example 1.
A magnetic recording medium was obtained. This magnetic recording medium was subjected to the CSS characteristic test.

(Embodiment 3) As the laser light source 11, CO ₂
Using the apparatus shown in FIG. 1 using a laser, laser light irradiation was performed on the same substrate as that used in Example 1 under the conditions of a repetition frequency of 5 kHz and a pulse width of 30 μsec. The laser beam irradiation position was the same as in Example 1. The substrate rotation speed during laser light irradiation was 500 rpm, and the irradiation time was 5 seconds. The laser power on the substrate was 10W. As a result of the above operation, the diameter of the laser beam irradiation range is 0.5 to 1.0 μm.
m was formed, and a substrate having Ra16 ° and Rmax220 ° was obtained. An underlayer, a magnetic layer, a protective layer, and a lubricating layer were provided on this substrate in the same manner as in Example 1 to obtain a magnetic recording medium. This magnetic recording medium was subjected to the CSS characteristic test.

(Embodiment 4) As the laser light source 11, YAG
Using the apparatus shown in FIG. 1 using a laser, the substrate was irradiated with laser light under the conditions of a repetition frequency of 50 kHz and a pulse width of 6 nsec. The laser beam irradiation position was the same as in Example 1. In this substrate, the grain size (average value) of the crystal grain portion is 0.5 μm, and the number per substrate unit area is 1000 μm.
000 pieces / mm ² , the average surface roughness was Ra8Å, and the maximum surface roughness was Rmax100Å. The substrate rotation speed during laser light irradiation was 60 rpm, and the irradiation time was 5 seconds. The laser power on the substrate was 20W. As a result of the above operation, the diameter of the laser beam irradiation range is 0.5 to 1.0 μm.
Thus, a substrate having m projections formed thereon and having Ra20 ° and Rmax270 ° was obtained. An underlayer, a magnetic layer, a protective layer, and a lubricating layer were provided on this substrate in the same manner as in Example 1 to obtain a magnetic recording medium. This magnetic recording medium was subjected to the CSS characteristic test.

Comparative Example 1 A CO ₂ laser was used as a laser light source, a repetition frequency was 10 kHz, and a pulse width was 10 μm.
The substrate is irradiated with laser light under the conditions of sec.
A substrate having a projection of 0 ° and a diameter of 10 μm was obtained. At this time, a laser beam having an incident beam diameter of
The surface of the substrate was irradiated through a 3.5 mm lens to form projections one by one at the irradiation position. The substrate rotation speed during laser beam irradiation was set at 250 rpm, and the substrate was rotated at a speed of 0.
Laser light irradiation was performed for 20 seconds while moving at 2 mm / s. The laser power on the substrate was 0.5W. The laser light irradiation range was the same as in Example 1.
The substrate used here was 65 mm in diameter made of amorphous glass made of alumina silicate. An underlayer, a magnetic layer, a protective layer, and a lubricating layer were provided on the substrate obtained by the above operation in the same manner as in Example 1 to obtain a magnetic recording medium. This magnetic recording medium was subjected to the CSS characteristic test.

(Comparative Example 2) Using a YAG second high frequency laser as a laser light source, the substrate was irradiated with a laser beam under the conditions of a repetition frequency of 40 kHz and a pulse width of 120 nsec to form a projection having a height of 200 ° and a diameter of 10 μm. A substrate was obtained. At this time, the surface of the substrate was irradiated with a laser beam having an incident beam diameter of 10 mm through a lens having a focal length of 40 mm to form projections one by one at the irradiation position. In addition, the rotation speed of the substrate during laser light irradiation was set to 250 rpm, and the laser light irradiation was performed for 4 seconds while moving the substrate in the radial direction at a speed of 0.8 mm / s. Laser power on substrate is 0.3
W. The substrate used here was the same as in Comparative Example 1. Example 1 was placed on the substrate obtained by the above operation.
An underlayer, a magnetic layer, a protective layer, and a lubricating layer were provided in the same manner as described above to obtain a magnetic recording medium. This magnetic recording medium is
It was subjected to SS characteristic test. Table 1 shows the results of subjecting the magnetic recording media of Examples 1 to 4 and Comparative Examples 1 and 2 to CSS property tests.

[0046]

[Table 1]

As shown in Table 1, it can be seen that the magnetic recording media of Examples 1 to 4 had lower friction values and better CSS characteristics than the magnetic recording media of Comparative Examples 1 and 2.

Although the present invention has been described based on the embodiments, the present invention is not limited to the above-described embodiments, and can be implemented in any manner unless the configuration described in the claims is changed. it can. For example, the layers formed on the substrate, the underlayer, the magnetic film, the protective film, the lubricant, and the like are not particularly limited to the material and composition, the film forming method, and the like, and may be formed of a known material or a known method. They can be appropriately selected and combined for use.

[0049]

As described above, in the method of manufacturing a magnetic recording medium according to the present invention, a plurality of projections are formed on the surface of the glass substrate by irradiating the laser light onto a predetermined region of the surface of the glass substrate. Are simultaneously formed, so that a projection having a uniform size and shape can be formed in a short time. Therefore, it is possible to efficiently manufacture a magnetic recording medium having excellent CSS characteristics. Further, by making the energy density of the laser light uniform, it is possible to further uniform the height of the protrusions formed within the laser light irradiation range, thereby further improving the CSS characteristics of the magnetic recording medium. Becomes

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a manufacturing apparatus used for carrying out a magnetic recording medium manufacturing method according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of the manufacturing apparatus shown in FIG.

FIG. 3 is a sectional view showing a main part of an example of the magnetic recording medium of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Grain part, 2 ... Amorphous part, 3 ... Protrusion, 11 ... Laser light source, 12 ... Kaleidoscope, D ... Substrate (crystallized glass substrate)

Claims (4)

[Claims] A laser beam is applied to a predetermined area of a surface of a crystallized glass substrate having a structure in which a large number of crystal grain parts are separated from each other by an amorphous part. A method for manufacturing a magnetic recording medium, comprising forming a plurality of protruding structures in which grain portions or amorphous portions protrude from a substrate surface. 2. The method for manufacturing a magnetic recording medium according to claim 1, wherein the laser beam has a uniform energy density. 3. The method for manufacturing a magnetic recording medium according to claim 1, wherein the laser beam has a wavelength of 200 to 600.
nm or 5000 to 12000 nm. 4. A protruding structure in which a crystal grain portion or an amorphous portion protrudes from the surface of a crystallized glass substrate having a structure in which a number of crystal grain portions are separated from each other by an amorphous portion. A magnetic recording medium characterized in that: