JPH09180179A - Magnetic recording medium and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a CSS (contact start and stop) characteristic and obviates the occurrence of head crash and to obviate the occurrence of unstablization in the space of a head. SOLUTION: This recording medium is formed by forming a magnetic layer via a ground surface layer at need on a nonmagnetic substrate and, in some cases, forming a lubricative layer via a protective layer on the magnetic layer. In such a case, projections having a height within the range of 1 to 100nm, a projection density of 10 to 10<8> pieces per mm<2> and the average value of <=2μm<2> in the area of the figure enclosed by the contour lines at a height of 1nm below the vertexes of the respective projections are formed on any of the nonmagnetic substrate, the ground surface layer, the magnetic layer or the protective layer. The recording medium is so formed that the surface of the protective layer is subjected to a surface treatment to increase its acid functional groups and thereafter the lubricative layer is laminated thereon.

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,
More specifically, it relates to a magnetic recording medium such as a hard disk used in a magnetic disk device. In particular, the present invention relates to a thin-film magnetic recording medium that enables good CSS characteristics, sticking characteristics of the head to the medium surface, and low flying height of the head, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Normally, a hard disk rotates at a high speed when used to float a magnetic head, and writing / reading to / from the hard disk is performed via the magnetic head. In order to improve the magnetic characteristics of the hard disk, the hard disk is provided on the substrate surface of the disk or on a substrate surface provided on the substrate surface.
On an underlayer made of a non-magnetic material such as iP plating, a process (hereinafter, referred to as mechanical texture) is performed by mechanically polishing the magnetic disk substantially concentrically to leave a processing mark in a circumferential direction.

With the recent increase in the amount of information and the demand for smaller and lighter devices, linear recording density and track density have increased.
As the area per bit becomes smaller, scratches due to mechanical texture as in the conventional case have a higher probability of becoming an error in reading information. There is also a method of mechanically texturing only the CSS zone on the inner periphery and leaving the data zone as it is, but the surface of the data zone becomes higher than the height of the surface of the CSS zone, and the head crashes when seeking. There was a problem.

[0004] Instead of such a mechanical texture, a method of forming a texture pattern by using a laser has also been proposed. An example of a laser texture method is disclosed in US Pat. Nos. 5,062,021 and 5,108,781, in which a NiP layer is locally melted by a strong pulsed laser beam of Nd-YAG, As shown in FIG. 3, the concave hole portion 6 formed by melting and Ni melted around it
The diameter of the solidified P that rises due to surface tension is 2.5 to 1
There has been proposed an attempt to form a large number of crater-shaped irregularities composed of a rim portion 7 of 00 μm and improve the CSS characteristics with the head by using an annular convex rim. However, this method does not drastically reduce the contact area with the lower surface of the head, and it is hard to say that the problem of sticking between the head and the disk has been improved as compared with the mechanical texture.

A method of forming protrusions using photolithography has also been proposed, and the tribology preliminary papers of the Japan Lubricating Society (1991-5, A-11), (1992).
-10, B-6) discloses the CSS test results of a magnetic disk in which concentric convex portions or projections having an area ratio of 0.1 to 5% to the entire surface of the disk are formed by photolithography. . But with this method,
Since the tops of the projections are smooth, there is a drawback that friction increases with the number of times the head slides, and there is a problem that industrialization is not easy.

Further, when a lubricant is applied to a textured disk by a method in which only the CSS zone on the inner peripheral portion is textured as described above, an appropriate amount of thickness is given to make the CSS zone durable. When the lubricating layer is formed, an excessive amount of the lubricant is added to the data zone, and the excessive lubricant is scraped from the data zone at the time of head seek, resulting in a problem that the flying stability of the head is impaired.

[0007]

Therefore, in the CSS zone, the area of the tip of the protrusion is reduced to eliminate sticking with the head, and the average height of the surface is made almost the same as that of the data zone. Data zone, CS
There is a demand for a magnetic recording medium in which fluctuations in the stable flying height of the head are small when a seek is performed between the S zones, and head crash and instability in the space of the head do not occur.

[0008]

The present invention provides such a high density.
It was made for a magnetic recording medium, and its summary
On the non-magnetic substrate, if necessary, through the underlayer,
A magnetic layer and a lubricating layer on the magnetic layer through a protective layer
A magnetic recording medium that is a magnetic recording medium
The height of the protrusion is 1 on either the protective layer or the protective layer.
Within 100 nm, the protrusion density is 1 mm^Two You
10-10⁸ 1n from the top of each protrusion
Average area of figures surrounded by contour lines at a height of m below
Value is 2 μm ^Two A magnetic recording medium formed with the following protrusions:
Body, the surface of the protective layer is surface-treated to prepare an acidic functional group.
After increasing, the lubricating layer is laminated.
Existing in a magnetic recording medium.

Further, the gist of the present invention is to provide a magnetic layer having a magnetic layer on a non-magnetic substrate, directly or via another layer provided as necessary, and having a lubricating layer on the magnetic layer via a protective layer. A method for manufacturing a recording medium, which comprises irradiating an energy beam on at least a part of the surface of a non-magnetic substrate or the surface of any other layer to obtain a height of 1 to 100 nm and a height of 1 n from the apex of a protrusion.
Mean value 10 per 1 mm ² of the projection group is 2 [mu] m ² or less of the area of a figure enclosed by contour line at height of lower m
A magnetic recording medium comprising: a step of forming protrusions having a density of 10 ⁸ ; and an step of oxidizing the surface of the protective layer to increase acidic functional groups before laminating a lubricating layer. It depends on the manufacturing method.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
As a substrate of the magnetic recording medium in the present invention, an aluminum alloy substrate, a glass substrate or a silicon substrate is preferably used, but other metal substrates such as copper and titanium, a carbon substrate, a ceramic substrate or a resin substrate is used. You can also As the silicon substrate, a silicon alloy substrate obtained by adding a trace element for increasing the strength to silicon can be used in addition to a pure silicon substrate. The substrate is usually formed in a disk shape, but may be in another shape, for example, a card shape.

Not only the above-mentioned non-magnetic substrate, but also the state after the underlayer, the magnetic layer, the protective layer, the lubricating layer and the like are provided on the non-magnetic substrate, or in the process thereof, the protrusions can be formed. Yes, hereinafter, the substrate may mean any one of these states.
The surface on which the protrusion is formed is the side where the magnetic recording medium comes into contact with the magnetic head.

In the present invention, the height of the protrusions on the non-magnetic substrate, the underlayer, the magnetic layer or the protective layer is a roughness curve defined by JIS surface roughness (B0601). Shows the height of the protrusion with respect to the center line. The height of this protrusion is preferably 1 to 100 n
m, more preferably 10 to 60 nm, and 100 nm
If the value exceeds 1, the CSS characteristics are good, but the stable flying height of the head cannot be lowered, and if it is less than 1 nm, it is buried in the fine irregularities that the substrate originally has, and the desired effect cannot be obtained.

Further, in the present invention, on a non-magnetic substrate,
Surface of either underlayer, magnetic layer or protective layer
In addition, the protrusion with a height of 1 to 100 nm is 1 mm^Two 10 per
-10 ⁸ I have one. If the number is less than 10, it may be due to the undulation of the substrate
It is difficult to support the lower surface of the head with only the protrusions.
⁸ If you try to make more than one protrusion, they will interfere with each other.
It is difficult to make the height of the protrusions uniform, and
Current density is 1 mm^Two 10 per^Three -10⁶ Individual.

The density of protrusions is not the average density of the entire medium, but the density per unit area of the protrusions. Further, each protrusion in the present invention is 1 from the top of the protrusion.
The average value of the area surrounded by contour lines at a height of nm below (hereinafter referred to as contour area) is 2 μm ² or less, preferably 0.001 to 1.0 μm ² , and more preferably 0.001 to ¹ μm ^2. 0.5 μm ² , more preferably 0.
It has a value in the range of 001 to 0.2 μm ² . If it exceeds 2 μm ² , sticking tends to occur between the head and the head, and it becomes impossible to operate the CSS.

The contour area is measured by a surface shape measuring device using laser interference, such as ZYG manufactured by Zago Co.
O] enables measurement. Further, the magnetic recording medium of the present invention is characterized in that a lubricating layer is laminated on a protective layer having a specific surface state while forming such a protrusion.

A preferred embodiment of the medium of the present invention is a magnetic recording medium in which the protrusion exists only in the CSS zone and does not exist in the data zone. With such a structure, the surface of the magnetic layer can be made smooth in the data zone, so that errors due to scratches as in the conventional case can be reduced.

In a further preferred embodiment, the magnetic recording medium in which the protrusion exists only in the CSS zone and does not exist in the data zone, and the height of the protrusion decreases toward the data zone, or An example is a magnetic recording medium in which the density of protrusions decreases toward the data zone. By decreasing the protrusion height toward the data zone, it is possible to stably seek the head from the data zone to the CSS zone or the opposite direction.

Further, by reducing the density of the protrusions toward the data zone, it is possible to obtain the same effect as when the height of the protrusions is sequentially changed. It is also a preferred method to reduce both the height and density of the protrusions towards the data zone.

As a preferred method for producing the magnetic recording medium of the present invention, while rotating the magnetic recording medium substrate, the surface thereof is irradiated with an energy beam whose output is precisely controlled along the circumferential direction. And a method of forming protrusions on the surface. Examples of the energy beam include a pulse laser, an electron beam, and an X-ray. Among them, it is preferable to use a pulse laser. Hereinafter, the present invention will be described using a pulse laser as an example. Also,
The present invention will be described by taking as an example the case where a magnetic recording medium substrate having an underlayer such as NiP provided on the substrate is used.

In the present invention, the mechanism of protrusion formation is not yet fully understood, but it is considered as follows. FIG. 2 is a conceptual diagram showing an expected generation mechanism of protrusions. FIG.
In (a), the locally overheated spot portion 5 of the underlayer 4 irradiated with the pulse laser 3 is partially melted, and the melted portion is caused by rotation of the substrate (direction is indicated by an arrow) or laser beam scanning. Moves. As shown in FIG. 2B, the temperature of the portion where the beam first hits then decreases and a temperature gradient occurs. Generally, in a molten liquid, the surface tension is higher on the low temperature side, and due to this difference in surface tension, the part that was first irradiated by the beam and melted and then became low temperature takes up the liquid of the melted part later and rises up. . Therefore, as shown in FIG. 2C, a concave portion is formed in the last melted portion, and the concave portion is provided at the rear portion of the protrusion in the scanning direction of the laser beam. That is, the vertical cross-sectional shape that passes through the center of the protrusion and includes the scanning direction of the laser beam has a concave portion on one side of the bottom portion of the protrusion.

In the present invention, the scanning direction of the laser beam is not limited to the scanning direction of the laser beam on a stationary disk, but the laser beam is stationary and the disk is irradiated in a rotated state. It also indicates the direction of rotation of.

Depending on conditions such as slow scanning of the laser beam or slow rotation of the substrate, or high power of the laser beam, there may be a case where a recess is formed around the bottom of the protrusion due to thermal contraction. Although this phenomenon has not been fully clarified, the locally heated spot portion expands, but the surrounding area is cold and difficult to deform, so the expanded portion is immediately cooled by the outside air and remains as a protrusion. Around the protrusion, a recess is formed due to heat shrinkage. Also, the top of the projection is not flat, but is hemispherical with an appropriate curvature.

US Pat. Nos. 5,062,021 and 5,5
In the method described in No. 108,781, since the irradiation range of the laser beam is wide and the laser output is a large output such as 1.5 W, the melting range of NiP is wide and the central part of the melted liquid surface is raised. Instead, it becomes a crater. On the other hand, in the present invention, since the laser beam is narrowed to a narrow range and the protrusions are accurately controlled under the condition where the output is low, the melting range of NiP is narrow and the center portion of the melted liquid surface rises in a convex shape. However, it differs greatly from the US patent in that it becomes a protrusion after solidification. Therefore, a projection having a very small area at the tip is formed.

The height of the protrusions can be freely controlled by adjusting the intensity of the laser, its average irradiation time, and the linear velocity of the disk, and the density of the protrusions can be determined by the number of protrusions per revolution and the radius of the pulse laser. The irradiation interval in the direction and the condition for controlling the height of the protrusions are adjusted to freely control. Usually the laser intensity is 20-500 mW,
Average irradiation time is 0.05 to 100 μsec, laser spot diameter is 0.2 to 4 μm, and substrate linear velocity is 0.8 to 1
5 m / sec is preferable. Here, the average irradiation time of the laser indicates the time during which the laser is applied to the surface of the underlayer to form one projection.

In order to change the irradiation area of the laser beam, it is usually necessary to change the aperture ratio of the objective lens.
By using the objective lens of 1 to 0.95, the irradiation diameter of the beam can be controlled to about 0.7 to 6 μm.

In the present invention, the laser irradiation is preferably applied to the underlayer (Ni-P layer) on the substrate, but even if it is applied to the surface of any layer up to the protective layer under substantially the same conditions, the desired protrusion is obtained. Can be formed. Of course, protrusions may be formed on the surface of the magnetic recording medium at the final stage.

In the method of manufacturing the magnetic recording medium of the present invention,
Although a magnetic recording medium can be formed by directly forming a magnetic layer on the surface of the substrate, an underlayer is usually formed on the surface of the substrate, and the magnetic layer is formed via the underlayer. As the underlayer, a non-magnetic underlayer made of a Ni-P alloy is preferable, and such an underlayer is usually formed by an electroless plating method or a sputtering method. The thickness of the underlayer is usually 50 to
20,000 nm, preferably 100-15,000 n
m.

The substrate is usually used after being mirror-finished (polished). Then, an underlayer (for example, Ni
In the case of using a substrate provided with -P underlayer), the surface of the underlayer is mirror-finished. Also, when using these substrates, prior to the formation of protrusions by irradiation of laser light,
It is also possible to previously form a low-height projection by subjecting the entire surface of the substrate to a slight mechanical texture. Such a mechanical texture has the following effects.

That is, when the height or density of the projections formed by the irradiation of the laser beam is small, that is, when the magnetic recording medium and the magnetic head are partially in contact with each other, the mirror-finished substrate is simply used. Compared with, sticking is less likely to occur and the coefficient of friction is also smaller. In addition, since the conditions for forming the protrusions can be widened, it is particularly preferable for mass production.

Between the substrate or the underlayer and the magnetic layer, C
It is preferable to provide an intermediate layer such as an r layer and a Cu layer. The thickness of the intermediate layer is usually 20 to 200 nm, preferably 50 to 200 nm.
100 nm. The magnetic layer (magnetic recording layer) is made of Co-
P, Co-Ni-P, Co-Ni-Cr, Co-Ni-
Pt, Co-Cr-Ta, Co-Cr-Pt, Co-C
It is composed of a ferromagnetic alloy thin film such as an r-Ta-Pt-based alloy and is formed by a method such as electroless plating, electroplating, sputtering, and vapor deposition. The thickness of the magnetic recording layer is usually about 30 to 70 nm.

A protective layer is provided on the surface of the magnetic recording layer. The protective layer is a carbon film, hydrogenated carbon film, Ti
Carbide films such as C and SiC, nitride films such as SiN and TiN,
It is composed of an oxide film of SiO, Al ₂ O ₃ , ZrO or the like, and is formed by a method such as vapor deposition, sputtering, plasma CVD, ion plating, or a wet method. As the protective layer, a carbonaceous protective film such as a carbon film or a hydrogenated carbon film is particularly preferable.

A lubricating layer is provided on the surface of the protective layer. As the lubricant, for example, a fluorinated liquid lubricant is preferably used, and the lubricant layer is usually formed on the surface of the protective layer by a dipping method or the like, but the lubricant layer of the magnetic recording medium having the protrusions of the present invention is used. By forming a lubricating layer after performing a surface treatment for increasing an acidic functional group on the surface of the protective film, for example, an oxidation treatment, the flight stability of the head seek of the obtained magnetic recording medium is further improved. improves.

Although the reason for this has not been fully clarified yet, since dirt on the head is reduced, dirt such as impurities adhering to the surface of the protective layer is removed by such surface treatment, and an acidic functional surface is used. It is considered that this is because the formation of the group increases the affinity with the lubricant, which makes it difficult for the lubricant to adhere to the head. In addition, it is considered that the protrusions satisfying the above-mentioned conditions contribute to improving the flight stability of the head.

As a method for increasing the acidic functional groups on the surface of the protective layer, for example, a wet method using a solution containing an oxidizing agent may be used, but a dry process is industrially preferable, and there is no particular limitation (for example, , Plasma oxidation treatment, etc.) and a treatment of irradiating ultraviolet rays in an oxygen-containing gas atmosphere (referred to as UV-ozone treatment) are easy and preferable methods.

When performing the UV-ozone treatment, the irradiation distance to the substrate to be processed, the irradiation power, the irradiation time, the irradiation atmosphere, etc. are important, and are greatly affected by the type of ultraviolet lamp used and the arrangement of the lamps. Determine the usage conditions in consideration of the factors.

That is, the effect is higher when the irradiation distance is closer to the processing substrate, but the closer the irradiation distance is, the narrower the irradiation range of the lamp becomes. Therefore, it is necessary to increase the number of lamps and consider the arrangement. The preferred lamp is 185
nm and 254 nm. Specifically, for example, in the case of a carbonaceous protective film, ultraviolet rays having an output of 90 W and having wavelengths of 185 nm and 254 nm are applied to the protective film from a distance of 5 mm to 50 mm for 5 seconds to 15 minutes.
Irradiation is preferably performed for 1 to 5 minutes.

The increase of the acidic functional groups on the surface is obtained by quantifying the oxygen atoms on the surface by X-ray photoelectron spectroscopy (XPS).
Or in the case of a carbonaceous protective film, C = O bond and C-C,
This can be confirmed by comparing the ratio with the C—H bond before and after the treatment. The carbonaceous protective film after the surface treatment was performed using an AlKα ray as an X-ray source and an extraction angle of 6
By XPS analysis at 5 degrees (analysis depth ~ 5 nm), C
It is preferable that the ratio of ═O bond to C—C and C—H bond is 0.05 or more. Usually 0.05 to 0.
It is selected from the range of 3, especially the range of 0.07 to 0.2.

In the magnetic recording medium having protrusions of the present invention, it is effective in terms of CSS characteristics and head flying stability that the protrusions are provided in the CSS zone and the surface treatment is applied to the data zone. As an industrial method in this case, a method of performing surface treatment selectively on the data zone by masking or the like can also be adopted.

[0039]

EXAMPLES Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the present invention. (Examples 1 to 5, Comparative Examples 1 to 6) Surface roughness Ra is 1 nm
A film having a thickness of 100 to 150 is sputtered on a disk-shaped glass substrate having a diameter of 95 mm whose surface is polished as follows.
A NiP underlayer of nm was formed. Next, an NiP layer with a wavelength λ = 514.5 nm of an argon pulse laser precisely controlled to the intensity shown in Table-1 was applied from the disc radius of 20 mm to 25 mm (CSS zone) under the conditions shown in Table-1. Then, the projections having substantially the same height were formed by irradiation to obtain a magnetic disk substrate.

FIG. 1 (a) is a diagram showing the results of observing the surface shape of the NiP layer of the substrate obtained in Example 1 with a surface shape measuring apparatus by laser interference ("ZYGO" manufactured by Zygo, USA). is there. 1B is a vertical cross-sectional view including the laser scanning direction of the protrusion of FIG. 1A, and FIG.
FIG. 3 is a cross-sectional view taken through the center of the protrusion in a direction perpendicular to FIG. 2B, where 1 is a protrusion and 2 is a recess on the rear side of the protrusion with respect to the laser beam scanning direction. The protrusion of the present invention is shown in FIG.
2C shows a shape as shown in FIG. 2C, and the tops of the isolated protrusions are not flat but hemispherical with an appropriate curvature.

Then, the N of the substrate is sputtered.
Cr intermediate layer (100 nm) and C on the iP underlayer in order
An o-Cr-Ta alloy magnetic film (50 nm) and a carbon protective film (20 nm) are formed, and then the CSS zone is masked so that only the data zone is irradiated.
Output 90 with wavelengths of 185 nm and 254 nm on the surface
Ultraviolet light of W was irradiated in the atmosphere for 5 minutes from a distance of 15 mm. A surface analysis by XPS was carried out to clarify how the carbon protective film was changed by the treatment, and it was found that oxygen atoms were contained at 20 atm% (X-ray source: AlKα ray, 14k-300W, use monochromator, analysis area: 0.8x3.5mm, take-out angle: 65 degrees (analysis depth 5nm).

Further, the C = O / C-H, C-C ratio was 0.04 before the surface treatment, but 0.10 after the treatment.
It was found that the number of acidic functional groups such as carboxyl groups on the carbon protective film increased remarkably. A fluorine-based liquid lubricant (trade name DOL-200 manufactured by Ausimont Co., Ltd.) was prepared by dipping the surface-treated substrate.
0) was applied to 2 nm to prepare a magnetic recording medium.

Table 1 shows Examples 1 to 5 and Comparative Examples 2 and 3.
Linear velocity of the substrate, laser intensity, average irradiation time of laser, average projection density (corresponding to laser irradiation interval), average projection height, contour area, and numerical aperture NA of the objective lens used for laser focusing Is shown. The spot diameter at which 84% of the energy is concentrated is represented by 1.22 × λ / NA.

[0044]

[Table 1]

Comparative Example 4 is a conventional mechanical texture method, in which Ra is a textured Al having a roughness of about 2 nm.
An alloy substrate was used. Examples 1 to 5 after sputtering
It was manufactured by the same process as. Table 2 shows the results of the static friction coefficient (initial stiction) of these discs before the CSS test and the frictional force after 20,000 CSS cycles. CSS
The test is a head flying height of 1.6μ inch, Roadgram 6
A gf thin film head (slider material AlTiC) was used. Stable flying heights in the CSS zone are all 1.0-1.
It was 1 μ inch.

[0046]

[Table 2]

Further, in order to investigate the flight stability in the CSS zone and the data zone, a head seek test was conducted from the inner circumference to the outer circumference of the disk to observe the degree of dirt on the head. Comparative Example 5 is Comparative Example 4 to clarify the effect.
In, the sample was prepared without performing the UV-ozone treatment. Comparative Example 6 was prepared in the same manner as in Example 1, except that the UV-ozone treatment was not performed.

The same head as that used in the CSS test was used. In the seek test, the head first floats in the CSS zone, then seeks from the CSS zone (inner circumference) to the data zone to the outer circumference of the disk, and then returns to the inner circumference. One seek is defined as the head after 50,000 seeks. Was observed. In this test, those that failed the CSS test were not tested (Comparative Examples 1 and 2). As a result, when the case of the comparative example 5 in which the head is extremely dirty is set to 100, the examples 1 to 5 are 5 or less, while the comparative example 3 is about 50, the comparative example 4 is about 80, and the comparative example 6 is It was about 40, and no improvement in head stain as in Examples 1 to 5 was observed. Thus, it can be seen that the magnetic recording medium of the present invention is resistant to head contamination.

[0049]

INDUSTRIAL APPLICABILITY In the present invention, the surface of the non-magnetic substrate, the underlayer, the magnetic layer, or the protective layer on which the height of the protrusion and the shape of the tip, the region where the protrusion exists, and the density are controlled. Since the shape is formed, 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 head to the medium surface does not occur at all. In addition, CSS of the head
If such protrusions are formed only in the zone, the average height of the surface will not change much, and by forming the lubrication layer after the surface treatment of the protective layer, the flight stability of the head will be improved. The head, data zone, CS
When seeking between the S zones, the fluctuation of the stable flying height of the head is small, and head crash and instability in the head space do not occur. Furthermore, since the height and density of the protrusions can be controlled as they approach the data zone, the seek between the data zone and the CSS zone of the head can be performed extremely smoothly. In this case, since it is not necessary to make scratches on the surface due to mechanical texture in the data zone, the flying height of the head can be reduced, and data errors due to the scratches can be reduced, so that high density magnetic recording media can be obtained. Can be manufactured,
Its industrial significance is extremely large.

[Brief description of the drawings]

FIG. 1 Ni of the present invention observed by a surface shape measuring apparatus.
The figure which shows the shape of the protrusion on the P substrate surface.

FIG. 2 is a conceptual diagram showing an expected generation mechanism of protrusions of the present invention.

FIG. 3 is a perspective view showing a shape of a medium surface according to a conventional method.

[Explanation of symbols]

 1 Protrusion 2 Recess 3 Pulse Laser 4 Underlayer 5 Spot 6 Recessed Hole 7 Rim

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area // C10N 40:18

Claims (12)

[Claims] 1. A magnetic recording medium having a magnetic layer on a non-magnetic substrate, optionally with an underlayer, and a lubricating layer on the magnetic layer with a protective layer, the non-magnetic substrate comprising: The height of the protrusions is in the range of 1 to 100 nm and the protrusion density is 1 on any of the substrate, the underlayer, the magnetic layer, and the protective layer.
A magnetic recording medium having 10 to 10 ⁸ protrusions per mm ² , and a protrusion group in which the average value of the area of a figure surrounded by contour lines at a height 1 nm below the apex of each protrusion is 2 μm ² or less. The magnetic recording medium is characterized in that a lubricating layer is laminated after the surface of the protective layer is surface-treated to increase the number of acidic functional groups. 2. The magnetic recording medium according to claim 1, wherein the projection has a recess around the bottom thereof. 3. The magnetic recording medium according to claim 1, wherein the magnetic head has protrusions only in a region (referred to as a CSS zone) where the magnetic head performs CSS (contact start and stop). Medium. 4. The magnetic recording medium according to claim 3, wherein the height of the protrusion decreases toward a data recording area (referred to as a data zone). 5. The magnetic recording medium according to claim 3 or 4, wherein the density of the protrusions decreases toward the data zone. 6. The magnetic recording medium according to claim 1, wherein the projections are formed by irradiation with an energy beam. 7. The magnetic recording medium according to claim 1, wherein the vertical cross-sectional shape passing through the center of the protrusion and including the scanning direction of the energy beam has a recess on one side of the bottom of the protrusion. Medium. 8. A magnetic recording medium according to claim 1, wherein only the data zone is surface-treated. 9. The magnetic recording medium according to claim 1, wherein the surface treatment method is an oxidation treatment. 10. The magnetic recording medium according to claim 9, wherein the oxidation treatment method is a treatment of irradiating ultraviolet rays in an oxygen-containing gas atmosphere. 11. A magnetic recording medium having a magnetic layer on a non-magnetic substrate, directly or via another layer provided as necessary, and a lubricating layer on the magnetic layer via a protective layer. A method comprising irradiating at least a part of the surface of the non-magnetic substrate or the surface of any other layer with an energy beam to a height of 1-10.
A protrusion forming step of providing a protrusion group having an average value of 2 μm ² or less of a figure surrounded by contour lines at a height of 0 nm and 1 nm below the apex of the protrusion at a density of 10 to 10 ⁸ per 1 mm ² , A method for producing a magnetic recording medium, comprising a step of surface-treating the surface of the protective layer to increase an acidic functional group before laminating the lubricating layer. 12. The protective layer is a carbonaceous protective film, and the surface of the protective layer after the oxidation treatment step is A as an X-ray source.
The above-mentioned oxidation was carried out so that the ratio of C═O bond to C—C and C—H bond was 0.05 or more in the analysis by XPS using the lKα ray at an extraction angle of 65 degrees (analysis depth ˜5 nm). 13. The method for manufacturing a magnetic recording medium according to claim 12, wherein a treatment is performed.