JPH08180400A - Magnetic recording medium and substrate - Google Patents

Abstract

PURPOSE: To lessen friction at the time of CSS by forming a surface shape controlled in the shape and height of projections and in the sectional area in the horizontal direction in their front end parts and the presence regions and density of the projections on the surface of a substrate or ground surface layer. CONSTITUTION: The height of projections is specified to be within a range of 1 to 40nm, the area of the graphic shape enclosed by the contour lines at the positions lower by 1nm from the tip ends of the projections is specified to <=0.5μm<2> , and the area of the graphic shape enclosed by the contour lines at the height of half the height of the projections is specified to <=3μm<2> on the front surface of the magnetic layer of the substrate or the ground surface layer. Further, the projections which are nearly circular in the shape of the section parallel with the surface of magnetic recording media are made to exist by 10 to 10<8> pieces per 1mm<2> . The height of the projections is specified to 1 to 30nm and further, preferably 10 to 25nm. Thereby, the contact area of the rear surface of the magnetic head with the surface of the magnetic recording medium is decreased. The sticking of the magnetic head on the medium surface is entirely obviated.

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 and a substrate, and more particularly to a magnetic recording medium such as a hard disk used in a magnetic disk device and a substrate therefor. In particular, the present invention relates to a thin-film magnetic recording medium and a substrate thereof, which can both improve good CSS (contact start and stop) characteristics, improve sticking characteristics of the magnetic head on the medium surface, and lower the flying height of the magnetic head.

[0002]

2. Description of the Related Art Normally, a hard disk is rotated at a high speed when it is used to levitate a magnetic head, and writing / reading of information to / from the hard disk is performed via the magnetic head. A hard disk is a NiP provided on the substrate surface or on the substrate surface in order to improve magnetic characteristics.
On an underlayer made of a non-magnetic material such as plating, mechanical polishing is performed in a substantially concentric shape in the circumferential direction of a magnetic disk to leave a processing mark (hereinafter referred to as mechanical texture).

With the recent increase in the amount of information and the demand for smaller and lighter devices, the linear recording density and track density have increased, and the area per bit has decreased. The flaw has a high probability of causing an error when reading information. For this reason, a method has been proposed in which the magnetic head on the inner circumference of the disk provides mechanical texture only to the CSS area in which CSS is performed, and the data recording area is left as it is, but the height of the surface of the data recording area is the CSS area. There is a problem that the height of the magnetic head becomes higher than that of the magnetic head and the magnetic head crashes when seeking.

Also, a method of making a texture pattern by a laser has been proposed in place of such a mechanical texture. Examples of the texture by a laser are disclosed in US Pat. Nos. 5,062,021, 5,108,781, etc., and the NiP layer is locally melted and melted by the intense pulsed laser light of Nd-YAG. The concave hole formed by the above and the surrounding NiP melted up due to surface tension and solidified to form a large number of crater-like irregularities composed of a rim portion with a diameter of 2.5 to 100 μm Attempts have been proposed to improve the CSS characteristics with the magnetic head by the convex rims. However, with this method, the contact area with the lower surface of the magnetic head is not drastically reduced, and it is hard to say that the problem of sticking between the magnetic head and the disk is improved as compared with the mechanical texture.

Further, a method of forming the protrusion by using photolithography has been proposed. An example of photolithography is the Tribology Proceedings of Japan Society of Lubrication (199
1-5, A-11), (1992-10, B-6), the area ratio to the entire surface of the disk is 0.
The CSS test results of a magnetic disk in which 1 to 5% concentric protrusions are formed by photolithography are shown. However, in this method, since the tops of the protrusions are smooth, there is a drawback that friction increases with the number of sliding of the magnetic head, and there is a problem that industrialization is not easy.

[0006]

As described above, in the CSS area of the magnetic recording medium, the area of the tip of the protrusion is reduced to eliminate sticking with the magnetic head, and the average surface height is set to the data recording area. When the magnetic head is sought between the data recording area and the CSS area at almost the same height as above, the fluctuation of the stable flying height of the magnetic head is small, and a head crash or instability in the space of the magnetic head occurs. No magnetic recording medium is desired. Particularly, as a high-density magnetic recording medium for extremely low flying of a magnetic head, the flying height of the magnetic head is 1.5 μinches or less even in the CSS area, and sticking of the magnetic head in the CSS area is prevented. There is a demand for a medium that can do this.

[0007]

The present invention has been made to such a medium for high density magnetic recording, and the first gist thereof is to have a magnetic layer on a substrate with an underlayer if necessary. In the magnetic recording medium, the height of the protrusion is in the range of 1 to 40 nm on the surface of the substrate or the underlayer on the magnetic layer side, and the area of the figure surrounded by the contour line at a position 1 nm lower than the tip of the protrusion is 0.5 μm. ^A protrusion having a size of ² or less, an area of a figure surrounded by contour lines at a height of ½ of the protrusion height of 3 μm ² or less, and a cross section parallel to the surface of the magnetic recording medium having a substantially circular shape is 10 per 1 mm ²
The magnetic recording medium characterized by the presence 10 ⁸ consists in.

A second aspect of the present invention is a substrate for a magnetic recording medium provided with an underlayer if necessary, wherein the height of the protrusion is 1 to 40 nm on the surface of the substrate or the underlayer on the magnetic layer side.
The area of the figure surrounded by the contour line at a position 1 nm lower than the tip of the projection is 0.5 μm ² or less, and the area of the figure surrounded by the contour line at a height of 1/2 of the projection height. Is 3 μm ² or less, and the protrusion whose cross section parallel to the surface of the magnetic recording medium is substantially circular is 1 mm.
^It exists in a substrate for a magnetic recording medium, characterized in that there are 10 to 10 ⁸ per ² .

The present invention will be described in detail below. In the magnetic recording medium and the substrate of the present invention, the height of the protrusion is in the range of 1 to 40 nm on the surface of the substrate or the underlayer on the magnetic layer side,
The area surrounded by contour lines at a position 1 nm lower than the tip of the protrusion has an area of 0.5 μm ² or less,
The area surrounded by contour lines at a height of / 2 is 3μ
m ² or less, and the magnetic recording medium surface substantially circular projection shape of a cross section parallel to the, 1 mm ² per 10 to 1
0 and ⁸ characterized by the presence of.

The height of this protrusion is preferably 1 to 30 n.
m, more preferably 10 to 25 nm, and if it exceeds 40 nm, the CSS characteristics are good, but it is difficult to reduce the stable flying height of the magnetic head to 1.5 μ inches or less, which is the object of the present invention, and it is less than 1 nm. Then, the substrate is buried in the fine irregularities which it originally has, and it becomes difficult to obtain a desired effect. In the present invention, the height of the protrusion represents the height of the protrusion with respect to the center line of the roughness curve defined by JIS surface roughness (B0601-1982).

In the present invention, the height is 1 to 40.
It is characterized by having 10 to 10 ⁸ nm protrusions per mm ^2, but if the existence density of the protrusions is less than 10, it is difficult to support the bottom surface of the magnetic head only by the protrusions due to the waviness of the substrate, and 10 ⁸ Since it is difficult to make the heights of protrusions interfere with each other when trying to make protrusions exceeding the number of protrusions, the preferable protrusion density is 10 per 1 mm ^{2.
It is 2} to 10 ^{6, and} more preferably 10 ³ to 10 ⁵ . Here, the protrusion density is not the average density of the entire medium,
It means the density per unit area in the protrusion existing portion.

Further, in the projection according to the present invention, the average value of the area of the figure surrounded by the contour line at a position 1 nm lower than the tip of the projection (hereinafter referred to as the contour line area) is 0.5 μm ^2.
Or less, preferably, 0.3 [mu] m ² or less, more preferably 0.2 [mu] m ² or less, more preferably 0.1 [mu] m ²
It has the following values: If the contour line area exceeds 0.5 μm ² and the protrusion density increases to 10 ⁵ or more per 1 mm ² , sticking easily occurs between the contour and the magnetic head, and it becomes difficult to operate the CSS.

Further, the size of the contour line area at a position half the height of the protrusion also affects the CSS characteristics depending on the environment such as the lubricant used and the humidity, and is therefore usually 3 μm.
² or less, preferably 2 μm ² or less, more preferably 1 μm
m ² or less is preferable. In addition, in the present invention, the cross-sectional shape of the protrusion is substantially circular and the tip shape of the protrusion is steep, so that the effect of preventing the lubricant from adsorbing to the medium surface of the magnetic head can be exhibited.

The contour line area and the cross-sectional shape are
It is possible to measure with a surface profile measuring device by laser interference, for example, Zygo [ZYGO] manufactured by Zygo Co., USA. As a preferred embodiment of the present invention, there is a magnetic recording medium in which the protrusion exists only in the area where the magnetic head performs CSS (CSS area) and not in the data recording area. With such a structure, it is possible to adopt a light texture in the circumferential direction or the like only for the orientation of the magnetic layer in the data recording area, and the surface can be made smoother. Therefore, it is possible to reduce errors due to deep scratches that are found in a mechanical texture having a rough surface for improving CSS as in the past.

Further, as a more preferable embodiment, there is a magnetic recording medium in which the height of the protrusions present in the data recording area is lower than the height of the protrusions present in the CSS area. Further, there is also a magnetic recording medium in which the density of the protrusions present in the data recording area is smaller than the density of the protrusions present in the CSS area. The height and density of the protrusions existing in the data recording area should be reduced so that the flying height of the magnetic head in the data recording area should be reduced as much as possible, and if the magnetic head should stop in the data recording area due to some trouble, it may be attracted to the medium surface. This is to prevent Normally, the CSS of the data recording area is 10
It is sufficient to perform 0 times, and normally, it is preferable that the height of protrusions in the data recording area is 1/2 or less of the height of protrusions in the CSS area, and the density is about 1/10 to 1/10 ⁴ .

Further, a magnetic recording medium in which the height of all protrusions in the CSS area or the height of protrusions in the vicinity of the data recording area of the CSS area decreases toward the data recording area is also a preferable embodiment. This makes it possible to stably seek the magnetic head from the data recording area to the CSS area or in the opposite direction. Further, a magnetic recording medium in which the protrusion density in the radial direction is smaller than the protrusion density in the circumferential direction in the CSS region is also mentioned as a preferable embodiment.

As a preferred method for producing the magnetic recording medium of the present invention, the substrate or the substrate for magnetic recording medium having an underlayer such as NiP provided thereon is rotated while the surface thereof is circumferentially extended. Then, a method of forming projections on the surface by irradiating an energy beam whose output is controlled with high precision can be cited. Examples of energy beams include pulse lasers, electron beams, and X-rays. Among them, it is preferable to use pulse lasers. Particularly, gas lasers such as Ar that have a uniform phase and a small spot diameter when condensed are used as a modulator. The pulsed form is preferable.

In the present invention, the mechanism of protrusion formation has not been fully clarified yet, but it is considered as follows. The locally overheated spot portion of the substrate or the underlayer irradiated with the pulse laser is partially melted, and the molten portion is moved by the rotation of the substrate or the laser scanning. The part where the laser first hits then cools down, creating a temperature gradient. Generally, in a molten liquid, the surface tension is higher on the low temperature side, and due to this difference in surface tension, the portion that was first irradiated with a laser and melted and then became low temperature takes up the liquid of the later melted portion and rises. . Therefore, a concave portion is formed in the last melted portion, and a concave portion is provided at the rear portion of the protrusion with respect to the laser scanning direction. That is, the vertical cross-sectional shape that passes through the center of the protrusion and includes the laser scanning direction is
A recess is provided on one side of the bottom of the protrusion. In addition,
In order to form a protrusion having a circular cross-sectional shape, which is a feature of the present invention, the spot diameter of the pulse laser is usually 2 μm.
m or less, and more preferably 1.5 μm or less. The lower limit is preferably 0.2 μm. Output is usually 200mW
Hereafter, it is more preferably 150 mW or less, and its lower limit is preferably 50 mW. The irradiation time for making one protrusion is usually 100 to 700 nsec, and particularly 1
0 to 500 nsec is preferable, and the distance over which the beam spot scans the substrate within the irradiation time is usually 0.
It is preferable to control in the range of 5 to 1.5 μm, preferably 0.75 to 1.25 μm.

NiP on an Al substrate or glass substrate
Alternatively, when a pulsed laser beam is scanned on a substrate having a Cr layer as an underlayer, the protrusions have the above-described characteristic shapes. In the present invention, the scanning direction of the energy beam is not only the direction in which the energy beam scans on the stationary disk, but also the rotational direction of the disk when the energy beam is stationary and the disk is irradiated in a rotated state. Is also shown.

When the scanning speed of the energy rays or the rotation speed of the substrate is slow, or when the power of the energy rays is large, there is a case where a concave portion is formed around the bottom of the protrusion due to thermal contraction. Although this phenomenon has not been fully clarified, it is considered that the locally heated spot part expands and the surrounding area is cold and difficult to deform, so the expanded part is immediately cooled by the outside air and remains as a protrusion. .

Further, the tops of the projections of the present invention are not flat and have an appropriate curvature. US Pat. No. 5,062,
In the methods described in Nos. 021 and 5,108,781, the irradiation range of the laser beam is wide and the laser output is a large output such as 1.5 W. Therefore, the melting range of NiP is wide and the melted liquid The center of the surface does not rise and becomes a crater.

On the other hand, in the present invention, since the energy rays are narrowed to a narrow range and the protrusions are accurately controlled under the condition of low output, the melting range of NiP is narrow and the center of the melted liquid surface is convex. The temperature rises in the liquid due to the scanning of the energy rays, and the shape of the liquid surface changes in a complicated manner. Therefore, the tip of the protrusion becomes steeper depending on the conditions, and when it is solidified, it has a characteristic protrusion shape, which is a big difference from the US patent. Therefore, the area of the tip is also very small, and a protrusion preferable for CSS can be formed.

The projection height can be freely controlled by adjusting the laser spot diameter, intensity, average irradiation time, disk linear velocity, and the like. It can be freely controlled by adjusting the number, the irradiation interval of the pulsed laser in the radial direction, and the conditions for controlling the height of the projections. For example, in order to change the irradiation area of the pulse laser, it is usually necessary to change the aperture ratio of the objective lens, and the aperture ratio is 0.1 to 0.
By using the 95 objective lens, the irradiation diameter of the pulse laser can be controlled to about 0.7 to 6 μm.

In the present invention, an aluminum alloy plate or a glass substrate is usually used as the substrate,
A metal substrate of copper, titanium, or the like, a ceramic substrate, a resin substrate, a silicon substrate, or the like can also be used. The underlayer is preferably a NiP alloy layer, and is usually formed on the substrate by electroless plating or sputtering. In addition, a Cr layer is usually formed on top of this, but this C
It is also possible to form protrusions on the r layer. The thickness of the underlayer is important in view of the relationship between heat generation by laser irradiation and heat dissipation by heat conduction, and is preferably 50 to 20,000 nm, particularly preferably 100 to 15,000 nm.

A Cr layer, a Cu layer, or the like is preferably provided on the underlayer between the magnetic layer and the Cr layer, and the thickness thereof is usually 20 to 200 nm, preferably 50 to 100 nm. The magnetic layer provided on the underlayer or the intermediate layer is usually
Co-P, Co-Ni-P, Co-Ni-Cr, Co-
Ni-Pt, Co-Cr-Ta, Co-Cr-Pt, C
It is formed by depositing a ferromagnetic alloy thin film such as an o-Cr-Ta-Pt-based alloy by a method such as electroless plating, electroplating, sputtering, vapor deposition, etc.
It is about 30 to 70 nm.

A protective layer is usually provided on the magnetic layer. As the protective layer, vapor deposition, sputtering, plasma CVD,
A carbon film, a hydrogenated carbon film, a carbide film such as TiC, SiC, etc., by a method such as ion plating or a wet method,
SiN, TiN, etc. nitride films, etc., SiO, Al ₂ O ₃ , Zr
An oxide film of O or the like is formed. Of these, a carbon film and a hydrogenated carbon film are particularly preferable. or,
A lubricant layer is usually provided on the protective layer.

[0027]

EXAMPLES Next, the present invention will be described more specifically by way of examples, but the present invention is not limited to the following examples unless it exceeds the gist. Examples 1 to 5, Comparative Examples 1 to 5 Film thickness 10 to 10 on a disk-shaped Al alloy substrate with a diameter of 95 mm
After NiP plating with a thickness of 20 μm, surface polishing was performed so that the surface roughness Ra was about 1 nm to obtain a NiP substrate.

Next, an argon pulse laser whose intensity is accurately controlled as shown in Table 1 was irradiated to the CSS region on the NiP substrate under the conditions shown in Table 1 to form protrusions, and the magnetic disk was formed. A substrate for use was obtained. FIG. 1 shows the first embodiment.
The surface shape of the NiP layer of the substrate obtained in 1. was measured by a laser interference surface shape measuring apparatus ("ZYGO" manufactured by Zygo, Inc., USA).
It is a figure showing the result observed by. 2A and 2B
1 is a vertical sectional view of the protrusion shown in FIG. 1 including a direction parallel to the laser scanning direction and a vertical sectional view including a direction (radial direction of the magnetic disk) perpendicular to the laser scanning direction. Where 1 is a protrusion and 2 is a recess on the rear side of the protrusion with respect to the scanning direction of the laser beam. FIG.
Shows the horizontal cross-sectional shape of the protrusion shown in FIG. 1, and it can be seen that it has a substantially circular shape.

That is, the protrusion of the present invention has a characteristic shape as shown in FIGS. 1 to 3, and the top of the isolated protrusion is not flat but has a proper curvature. Also, FIG.
Is the surface shape of the NiP layer of the substrate obtained in Comparative Example 3,
It is a figure showing the result of having observed with the surface shape measuring apparatus by laser interference ("ZYGO" by the US Zigo company). 5A and 5B are vertical sectional views of the protrusion shown in FIG. 1 including a direction parallel to the laser scanning direction and a direction perpendicular to the laser scanning direction (radial direction of the magnetic disk). FIG. 6 is a vertical cross-sectional view each including FIG.
It shows the horizontal cross-sectional shape of the protrusion shown by, and has an elliptical shape.

Next, the N of the substrate is sputtered.
A Cr intermediate layer (film thickness 100 n is formed on the iP underlayer in order.
m), a Co-Cr-Ta alloy magnetic film (thickness 50 nm) and a carbon protective film (thickness 20 nm) are formed, and then a fluorine-based liquid lubricant (trade name DOL-2000 manufactured by Monte Edison Co., Ltd. is prepared by an immersion method. Was applied to a film thickness of 2 nm to prepare a magnetic recording medium.

In Comparative Example 4, the texture A having Ra of about 2 nm was applied by the conventional mechanical texture method.
A magnetic recording medium was manufactured by the same process as in the example except that the 1-alloy substrate was used. Table 1 shows Examples 1 to 5
In Comparative Examples 2 to 4, the conditions when the protrusions were formed and the measurement results (the linear velocity of the substrate, the laser intensity,
Average laser irradiation time, average projection linear density (circumferential direction / radial direction), average projection height, contour area 1 nm lower than the tip of the projection (1), contour area 1/2 projection height ( 2), the shape of the horizontal cross section of the protrusion). The objective lens used for condensing the Ar laser having a wavelength of 488 nm had an aperture ratio NA of all 0.6. The spot diameter at which 84% of the energy is concentrated is 1.
It is represented by 22 × λ / NA.

[0032]

[Table 1] Table-1 ----------------------------------- Substrate laser average average projection average projection Contour line Asperity Linear velocity Intensity Irradiation time Density Elevation product (μm ² ) Horizontal cross section (mm / sec) (mW) (μsec) (pieces / mm) (nm) (1) / (2) Shape −−− −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− Example 1 3200 100 0.31 100/100 22 0.07 / 0.93 circular shape 2 3200 100 0.31 200/50 22 0.07 / 0.93 Circular 3 3200 100 0.31 50/50 22 0.07 / 0.93 Circular 4 3200 120 0.31 10/20 26 0.08 / 1.82 Circular Comparative Example 1 No laser irradiation 2 3200 20 0.31 100/100 1 or more 3 1600 220 1.24 100/100 29 0.21 / 3.05 Elliptical 4 Mechanical texture −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− −−−−−

Table 2 shows the obtained magnetic recording medium at room temperature,
The coefficient of static friction (initial stiction) before the CSS test at normal humidity and the friction force after 20,000 CSS cycles are shown. CS
In the S test, a thin film head (slider material: Al ₂ O ₃ TiC) having a head flying height of 2.5 μinch and a loadgram of 6 gf was used. The stable flying heights in the CSS area are all 1.2 to 1.
It was 6 μ inches. Table 3 shows the CSS test results of the magnetic recording media obtained in Example 1 and Comparative Example 3 at 30 ° C. and 80% humidity.

[0034]

Table 2 −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− Initial stiction CSS after 20,000 times ( Friction coefficient) Friction force ------------------------------------------ Example 1 0.17 3gf 2 0.18 3gf 3 0.37 12gf 4 0.23 16gf Comparative Example 1 Unmeasurable (head crash due to adsorption) 2 5.20 Adsorption and drive stop (200th time) 3 0.19 7gf 4 1.25 38gf ----- −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−

[0035]

Table 3 −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− Initial stiction CSS After 20,000 times ( Friction coefficient) Friction force --------------------------------------- Example 1 0.19 4 gf Comparative Example 30 .24 Adsorption and drive stop (18,000th time) -----------------------------------------------

As is clear from Tables 2 and 3, the magnetic recording medium according to the present invention has extremely small friction during CSS,
Also, it can be seen that the durability of the performance is excellent. Also, the CSS characteristics slightly change depending on the shape of the protrusions. For example, an elliptical protrusion long in the traveling direction of the magnetic head as in Comparative Example 3 has good CSS characteristics under normal temperature and normal humidity conditions. However, under the conditions of high temperature and high humidity, the characteristics deteriorate as the number of times of CSS is repeated. On the other hand, the protrusion having the substantially circular cross section of Example 1 in which the tip of the protrusion is steep has a gradual deterioration in characteristics even under high temperature and high humidity.

[0037]

According to the present invention, a surface shape is formed on the surface of a substrate or an underlayer in which the shape and height of the projection and the cross-sectional area at the tip portion thereof in the horizontal direction, the area where the projection exists and the density are controlled. Therefore, the contact area between the lower surface of the magnetic head and the surface of the magnetic recording medium is small, friction during CSS is extremely small, and sticking of the magnetic head to the medium surface does not occur at all.

Further, there is an advantage that the time required for forming the protrusions can be shortened by utilizing the property that the CSS characteristics are not significantly deteriorated even if the protrusion density in the circumferential direction is increased and the protrusion density in the radial direction is decreased. Further, when such a protrusion is formed only in the CSS area of the magnetic head, the average height of the surface is almost the same, so that the magnetic head is set to the data recording area C
There is almost no fluctuation in the stable flying height of the magnetic head when seeking to the SS area, and head crashes and instability in the space of the magnetic head do not occur. Further, since the height and density of the protrusions can be controlled as they approach the data recording area, the seek between the data recording area and the CSS area of the magnetic head can be performed extremely smoothly.

In this case, in the data recording area, since it is not necessary to make a scratch on the surface by mechanical texture for the purpose of improving CSS as in the conventional case, the flying height of the magnetic head can be made small, and the data due to the scratch can be reduced. Since the error is also reduced, it is possible to manufacture a high-density magnetic recording medium, which is of great industrial significance.

[Brief description of drawings]

FIG. 1 is a perspective view showing the shape of protrusions on the surface of a NiP substrate obtained in Example 1.

FIG. 2A is a vertical sectional view including a direction parallel to a laser scanning direction of a protrusion on a NiP substrate surface obtained in Example 1 and FIG. 2B is a vertical sectional view including a direction perpendicular to the laser scanning direction. ).

FIG. 3 is a view showing a horizontal cross-sectional shape of protrusions on the surface of a NiP substrate obtained in Example 1.

FIG. 4 is a perspective view showing the shape of protrusions on the surface of a NiP substrate obtained in Comparative Example 3.

5A is a vertical sectional view including a direction parallel to a laser scanning direction of a protrusion on a surface of a NiP substrate obtained in Comparative Example 3 and FIG. 5B is a vertical sectional view including a direction perpendicular to the laser scanning direction. ).

6 is a diagram showing a horizontal cross-sectional shape of protrusions on the surface of a NiP substrate obtained in Comparative Example 3. FIG.

[Explanation of symbols]

 1 protrusion 2 recess

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junichi Kozu 1000 Kamoshida-cho, Aoba-ku, Yokohama-shi, Kanagawa Mitsubishi Chemical Corporation Yokohama Research Institute

Claims (13)

[Claims] 1. In a magnetic recording medium having a magnetic layer on a substrate, optionally with an underlayer, the height of the protrusions is in the range of 1 to 40 nm on the surface of the substrate or the underlayer on the magnetic layer side, The area surrounded by the contour line at a position 1 nm lower than the tip of the protrusion is 0.5 μm ² or less, and the area surrounded by the contour line at half the height of the protrusion is 3 μm ² or less. The magnetic recording medium is characterized in that there are 10 to 10 ⁸ protrusions per 1 mm ² which have a substantially circular cross section parallel to the surface of the magnetic recording medium. 2. A recess is provided near the bottom of the protrusion.
3. The magnetic recording medium according to claim 1. 3. The magnetic recording medium according to claim 1, wherein the magnetic head has protrusions only in a CSS region where CSS (contact start and stop) is performed. 4. The height of the protrusion existing in the data recording area is lower than the height of the protrusion existing in the CSS area.
Alternatively, the magnetic recording medium according to 2. 5. The magnetic recording medium according to claim 1, wherein the density of the protrusions present in the data recording area is smaller than the density of the protrusions present in the CSS area. 6. The magnetic recording medium according to claim 1, wherein the protrusion height of the CSS area decreases toward the data recording area. 7. The magnetic recording medium according to claim 1, wherein the protrusion height near the data recording area in the CSS area decreases toward the data recording area. 8. The protrusion density in the radial direction is smaller than the protrusion density in the circumferential direction in the CSS region.
The magnetic recording medium according to any one of 1. 9. The magnetic recording medium according to claim 1, wherein the protrusions are formed by irradiation with energy rays. 10. The magnetic recording medium according to claim 9, wherein a vertical cross-sectional shape that passes through the center of the protrusion and is parallel to the scanning direction of the irradiation energy ray has a recess near one side of the bottom of the protrusion. 11. A substrate for a magnetic recording medium optionally provided with an underlayer, wherein the height of the protrusion is in the range of 1 to 40 nm on the surface of the substrate or the underlayer on the magnetic layer side, and is 1 nm lower than the tip of the protrusion. The area of the figure surrounded by the contour line at the position is 0.5 μm ² or less, the area of the figure surrounded by the contour line at the height of 1/2 of the protrusion height is 3 μm ² or less, and the surface of the magnetic recording medium A substrate for a magnetic recording medium, characterized in that there are 10 to 10 ⁸ protrusions per mm ² having a substantially circular cross section parallel to the substrate. 12. The magnetic recording medium according to claim 11, wherein the projection is formed by irradiation with energy rays. 13. The vertical cross-sectional shape, which passes through the center of the protrusion and is parallel to the scanning direction of the irradiation energy ray, has a recess near one side of the bottom of the protrusion.
2. The magnetic recording medium according to 2.