JPH1186279A - Magnetic recording medium and substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium which hinders possible crashing of a magnetic head and instability in a space of the head by minimizing changes in stable lifting height of the magnetic head at any seeking action. SOLUTION: This magnetic recording medium which has a magnetic layer on a non-magnetic substrate 4 through a ground layer as required has protrusions with the number of 10-10<8> at the height of 1 nm to 50 nm on the surface on the side of the magnetic layer of the non-magnetic substrate 4 or the ground layer per 1 mm<2> of the surface. The protrusions are so arranged to exceed 1 in the ratio (p) of the length between that at the right angle to and that parallel with the direction of running of a magnetic head on the recording medium as to cross sections surrounded by contour lines at the height a half as much as that of protrusions and 1/2 in the ratio (q) of the length between the protrusions at the right angle to the direction of running thereof as to cross sections surrounded by contour lines at the height 9/10 and 1/2 as much as that to the top thereof from the surface of an average roughness.

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 drive and a substrate therefor. In particular, the present invention relates to a thin-film magnetic recording medium and a substrate thereof capable of simultaneously improving good CSS (contact start and stop) characteristics, improving sticking characteristics of the magnetic head to the medium surface, and lowering the flying height of the magnetic head.

[0002]

2. Description of the Related Art Normally, writing / reading of information to / from a hard disk is performed via a magnetic head, and at that time, the hard disk rotates at a high speed to float the magnetic head. In order to improve the magnetic characteristics, the hard disk is mechanically arranged substantially concentrically in the circumferential direction of the disk on a nonmagnetic substrate surface or on an underlayer made of a nonmagnetic material such as NiP plating provided on the nonmagnetic substrate. Processing (hereinafter referred to as mechanical texture) that leaves a processing mark by polishing is performed.

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, the likelihood of scratches due to mechanical texture as in the prior art becomes an error when reading information increases. Therefore, a method has been proposed in which only the CSS area on the inner periphery of the disk is mechanically textured and the data recording area is kept as it is. In this case, the surface of the data recording area is higher than the height of the CSS area. There is a problem that the magnetic head crashes when seeking.

[0004] Instead of such a mechanical texture, a method of forming a texture pattern by using a laser has also been proposed. Examples of the texture by a laser are disclosed in U.S. Pat. Nos. 5,062,021 and 5,108,781, and the like. The NiP layer is locally melted by a Nd-YAG Q-Switch strong pulse laser beam. As a result, as shown in FIG. 1, a rim having a diameter of 2.5 to 100 μm formed by solidifying the concave hole 6 formed by melting and the molten NiP around the hole by surface tension. An attempt has been made to improve the CSS characteristics with a magnetic head by forming a large number of crater-shaped irregularities composed of the portion 7 and using an annular convex rim. However, this method does not drastically reduce the contact area with the lower surface of the magnetic head, 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.

[0005] The same laser texture technique is used, but a relatively long laser pulse is generated by using a laser light source capable of continuous oscillation and an external light modulator, and the laser beam is swept over the substrate surface to be asymmetric. Many protrusions with a very small area at the tip of the protrusion are made and CSS with the magnetic head
An attempt to improve the characteristics has been proposed in JP-A-8-106630. This technology is extremely effective in reducing the contact area between the disk and the head, and is extremely effective in stiction resistance. However, in special environments where wear is dominant, such as high temperatures and dry conditions, protrusions Wear at the tip could be a problem.

An example using photolithography is:
Proceedings of the Japan Society of Lubrication Tribology (1991-5A
-11), (1992-10, B-6), and a CSS test of a magnetic disk in which concentric protrusions having an area ratio of 0.1 to 5% to the entire surface of the disk are formed by photolithography. The results are shown. However, this method has a drawback that the coefficient of friction increases because the tops of the projections are smooth, and there is a problem that industrialization is not easy.

[0007]

As described above, in the CSS area of the magnetic recording medium, the area of the tip of the projection is reduced to eliminate sticking when the magnetic head stops,
In addition, there has been a demand for a projection shape in which the projection is less worn even in an environment such as a high temperature and a dry environment. Also, when the magnetic head is sought between the data recording area and the CSS area by making the average surface height almost the same as the data recording area, the fluctuation of the stable flying height of the magnetic head is small. There is a demand for a magnetic recording medium that does not cause a crash or instability in the space of the magnetic head.

[0008]

The present invention has been made for such a magnetic recording medium for high-density recording. The first gist of the present invention is to provide a magnetic recording medium on a non-magnetic substrate through an underlayer if necessary. A magnetic recording medium having a magnetic layer, the height of which is 1 nm or more,
0 nm or less, the ratio p of the length in a direction perpendicular to and parallel to the running direction of the magnetic head on the recording medium in a cross section surrounded by a contour line at a height of 突起 of the protrusion height is 1 or more; 9/1 from the average roughness surface to the projection top
There are 10 or more and 10 ⁸ or less projections having a length ratio q in the perpendicular direction of the projection cross section surrounded by the contour lines at heights of 0 and で of １ ／ or more per 1 mm ^{2 of} the surface. A magnetic recording medium.

A second gist of the present invention is a magnetic recording medium having a magnetic layer on a nonmagnetic substrate, if necessary, with an underlayer interposed therebetween, wherein the surface of the nonmagnetic substrate or the underlayer has a magnetic layer side. A section surrounded by a contour line having a height of 1 to 50 nm and a height equal to 1/2 of the height of the projection has a ratio p of lengths in a direction perpendicular to and parallel to the running direction of the magnetic head on the recording medium.
Is 1 or more, and the ratio q of the length in the perpendicular direction of the cross section of the projection surrounded by the contour at the height of 9/10 and 1/2 with respect to the projection top from the average roughness surface is 1/2. 10 or more protrusions per mm ^{2 of} the surface
The magnetic recording medium substrate, characterized in that it comprises 0 ⁸ or less consists in.

Hereinafter, the present invention will be described in detail. The magnetic recording medium and the substrate of the present invention have a height of 1 to 50 nm and a protrusion height of 1 to 50 nm on the nonmagnetic substrate or the surface of the underlayer on the magnetic layer side.
The ratio p of the length of the cross section surrounded by the contour line at the height of / 2 to the direction perpendicular to and parallel to the running direction of the magnetic head on the recording medium is 1 or more, and
Length ratio q in the perpendicular direction of the cross section of the projection surrounded by contour lines at heights of 9/10 and 1/2 with respect to the projection top
A projection but is 1/2 or more, the surface 1 mm ² per 10
It is characterized by having not less than 10 ⁸ pieces.

Here, p and q will be described in more detail. P in the present invention is, as described above, a cross section surrounded by contour lines at half the height of the projection,
The value obtained by dividing the length in the direction perpendicular to the running direction of the magnetic head by the length in the parallel direction is 1 or more. When the cross section surrounded by the contour line at half the height of the protrusion has an elliptical shape as shown in FIG. 9, the length in the perpendicular direction / the length in the parallel direction is calculated as Is the division between the maximum values of However, in the case where the oval has a distorted shape as shown in FIG. 10, simply dividing the maximum values does not make the length in the parallel direction match the actual shape.
In FIG. 10, γ-γ ′ is the maximum value, but it is clear that this value is incorrect as a value indicating the accuracy of the protrusion. Therefore, in the present invention, the length in the parallel direction at the midpoint of the length in the perpendicular direction is referred to as “the length in the direction parallel to the running direction of the magnetic head”. Thus, in FIG. 10, α-α ′ is the length in the parallel direction. On the other hand, as a repetition, “the length in the direction perpendicular to the running direction of the magnetic head” simply means the maximum value of the length in the direction perpendicular to the running direction.

The height of the projection is usually 1 nm or more and 50 n
m or less, preferably 1 nm or more and 30 nm or less, more preferably 5 nm or more and 25 nm or less. If it exceeds 50 nm, CSS characteristics are good even if the projection density is low, but it is difficult to lower the stable flying height of the magnetic head. If the protrusion height is less than 1 nm, the substrate may be buried in the fine irregularities inherent in the substrate, and it may be difficult to obtain a desired effect. In the present invention, the height of the protrusion is JIS
Defined by the surface roughness (B0601-1982),
It represents the height of the protrusion with respect to the center line of the roughness curve.

In the present invention, the projection is usually a projection.
Figure surrounded by contours at a height 1 nm below the top
Average value (hereinafter referred to as contour line area) is 0.01
μm ^Two10 μm or more^TwoOr less, preferably 0.
02 μm^Two5 μm^TwoOr less, more preferably 0.2
μm^Two3 μm^TwoIt has the following values: The contour area
Is 10 μm^TwoOver the magnetic head,
King tends to occur and 0.01μm^TwoLess than
Becomes prone to wear, the CSS may be activated
May be impossible.

In the present invention, the projection usually has a length in a direction perpendicular to the running direction of the magnetic head on the recording medium in a cross-sectional shape surrounded by a contour line at half the height of the projection. , Which are larger than the length in the parallel direction. Preferably, the ratio p between the perpendicular and parallel directions is 1 or more, preferably 2 or more and 20 or less, and more preferably 3 or more and 10 or less.

Further, it is preferable that the figure surrounded by contour lines at half the height of the projection is a bar. The cross-sectional shape of the protrusion in the present invention is, as described above, the ratio of the length in the perpendicular direction of the cross section of the protrusion surrounded by a contour line at a height of 9/10 and 1/2 with respect to the top of the protrusion from the average roughness surface. q is 以上 or more. That is, the projection shape according to the present invention is trapezoidal when viewed from the head running direction, and it is desirable that the top be as smooth as possible. In this way, when the slider portion of the head collides with the projection, Since the impact of the head can be received in as large an area as possible, the projection has excellent wear resistance.

When the head stops on the projection,
In order to reduce the contact area, the shape of the projection as viewed from the direction perpendicular to the head running direction is steep, and it is considered that the lubricating material exerts the effect of preventing the magnetic head from adsorbing to the medium surface. The contour area and the cross-sectional shape can be measured by a surface shape measuring device using laser interference, for example, “ZYGO” manufactured by Zigo USA.

A preferred embodiment of the present invention is a magnetic recording medium in which protrusions are present only in a region where the magnetic head performs CSS (CSS region), but not in a data recording region. By adopting such a configuration, a light texture in the circumferential direction for the purpose of only the orientation of the magnetic layer can be adopted in the data recording area, and the surface can be made smoother. Therefore, as before, CS
Errors due to scratches due to mechanical texture for the purpose of improving S can be reduced, and at the same time, the flying height of the magnetic head on the data surface can be reduced, and a medium for high density can be developed.

In a further preferred embodiment, the protrusions are present only in the region where the magnetic head performs CSS and are not present in the data recording region, and the heights of the protrusions on the side close to the data recording region or the heights of all protrusions Is decreasing toward the data recording area. By reducing the protrusion height toward the data recording area, the magnetic head can be stably sought from the data recording area in the CSS area or in the opposite direction. When the medium of the present invention is applied to a drive of a dynamic loading system, usually, the head is loaded from the outer peripheral portion of the disk. Therefore, it is desirable to form a projection on the outer peripheral portion.

Further, the protrusion may be present not only in the CSS area but also in the data recording area. With this,
Even when the magnetic head stops in the data recording area due to a trouble or the like, it is possible to prevent the magnetic head from being attracted to the medium surface. In this case, the protrusion height of the data recording area is preferably lower than the protrusion height of the CSS area, and the protrusion density of the data recording area is preferably lower than the protrusion density of the CSS area. By making the projection height and the projection density of the data recording area smaller than those of the CSS area, the flying height of the magnetic head in the data recording area can be reduced.

Normally, the CSS in the data recording area is
As long as it can be performed about 100 times, the projection height of the data recording area is usually 以下 or less of the projection height of the CSS area, and the projection density of the data recording area is 1/1 of the projection density of the CSS area.
It is preferable to set it to 0 or more and about 1/10 ⁴ or less. Also in this case, it is preferable that the heights of the protrusions in the CSS area closer to the data recording area or all the protrusions decrease toward the data recording area.

A preferred method for producing the magnetic recording medium of the present invention is to rotate a magnetic recording medium substrate provided with an underlayer such as NiP on a nonmagnetic substrate such as an Al substrate or on a nonmagnetic substrate. Along its circumference on its surface,
A method of forming projections on the surface by irradiating an energy ray whose output is controlled with high accuracy, and the like can be given. In this case, the shape of the energy distribution on the plate surface is set to be elliptical or rod-like in a direction perpendicular to the head traveling direction in the recording medium. Examples of the energy beam include a pulse laser, an electron beam, an X-ray, and the like. Among them, it is preferable to use a pulse laser. Hereinafter, the present invention will be described using a pulse laser as an example.

The mechanism for forming the projections in the present invention is considered as follows. FIG. 2 is a conceptual diagram showing an expected generation mechanism of a protrusion. In FIG. 2A, the spot portion 5 irradiated with the pulse laser 3 and locally heated is partially melted, and the melted portion is moved by rotation of the substrate (the direction is indicated by an arrow) or scanning of the laser beam. I do. As shown in FIG. 2 (b), the temperature of the portion where the beam first hits decreases thereafter, so that a temperature gradient occurs in the melted portion. In general, the surface tension of the molten liquid on the low-temperature side is higher.Therefore, due to the difference in the surface tension, the part that is first irradiated by the beam and melts, and then cools down, takes in the liquid from the molten part later. Excitement. Therefore, as shown in FIG. 2C, a concave portion is formed in the last melted portion, and a concave portion is provided at the rear portion of the protrusion in the scanning direction of the laser beam. In other words, a vertical cross-sectional shape that passes through the center of the projection and is parallel to the scanning direction of the laser beam has a concave portion on one side of the bottom of the projection. It should be noted that the cross-sectional shape surrounded by the contour line at half the height of the protrusion, which is a feature of the present invention, has a shape in which the length in the perpendicular direction is longer than the length in the traveling direction of the head. When the ratio q of the length in the perpendicular direction of the cross section of the projection surrounded by the contour at the height of 9/10 and 1/2 with respect to the top of the projection from the average roughness surface is not less than 1/2. In order to form a certain protrusion, the laser spot at the focal point is formed into an elliptical or rod-like shape that is long in the perpendicular direction, and the irradiation time of the pulse laser is controlled. Usually, it is desirable that the scanning distance on the substrate within the irradiation time be within twice the laser spot diameter in the sweep direction.

When a pulsed laser beam having the above laser spot shape is scanned on an aluminum substrate, a glass substrate, or a substrate on which a NiP layer, a Cr layer, or the like is provided as an underlayer as a nonmagnetic substrate, A projection having such a characteristic shape is obtained. In the present invention, the scanning direction of the laser beam means not only the direction in which the laser beam scans on the stationary substrate, but also the direction of rotation of the disk when the laser beam is kept stationary and the substrate is irradiated while rotating. Is also shown.

Depending on conditions such as the scanning of the laser beam or the rotation of the substrate is slow, or the power of the laser beam is large, a recess may be formed around the bottom of the projection due to thermal contraction. The locally heated spot expands and the area around it cools and is hard to deform, so the expanded part is immediately cooled by the outside air and remains as a protrusion, and the periphery of the protrusion can be dented by thermal contraction. Conceivable. The top of the projection of the present invention is relatively flat in the direction perpendicular to the sweep direction of the laser beam, and in the sweep direction, is not flat but has an appropriate curvature.

The aforementioned US Pat. No. 5,062,021,
In the method described in JP-A-5,108,781, the irradiation range of the laser beam is wide and the laser has a large output, so that the melting range of NiP is wide, and the central part of the melted liquid surface does not rise and has a crater shape. Will be. On the other hand, in the present invention, since the laser beam is narrowed down to a narrow range and has an elliptical or rod-like beam spot shape, the projection can be accurately controlled under a condition where the laser output is low. In addition, the center of the melted liquid surface rises, and a temperature difference in the liquid can be generated in the liquid by scanning the beam. Can be made steeper, and when solidified, it has a characteristic projection shape, which is greatly different from the above-mentioned U.S. Patent. Accordingly, the area of the tip of the protrusion, the width of the protrusion on the surface with which the head collides with CSS, and the like can be freely changed, and a preferable protrusion for the head CSS can be obtained.

Also, the height of the projection is the spot shape of the laser,
It can be controlled freely by adjusting the intensity, average irradiation time, and linear velocity of the disk. The density of the protrusions is determined by the number of protrusions per rotation, the irradiation interval in the radial direction of the pulse laser, and the protrusions described above. The height can be controlled freely by adjusting the conditions for controlling the height. In the present invention, a preferable laser intensity is 100 mW or more,
500 mW or less, particularly preferably 200 or more, 700 m
W or less, the average irradiation time is preferably 0.1 μsec or more and 5 μsec or less, particularly preferably 0.1 μsec or more and 1 μsec or less, and the laser spot diameter is preferably (parallel to the magnetic head traveling direction) × (magnetic head (Perpendicular to the direction of travel) (0.5-2)
× (2-100) μm, particularly preferably (1-2) ×
(5-10) μm, the linear velocity of the substrate is preferably 1 m / s
ec or more and 10 m / sec or less. Here, the average irradiation time of the laser indicates the time during which the laser is applied to the substrate or the underlayer surface to form one projection.

In order to change the shape and irradiation area of the laser beam, it is usually sufficient to control the beam by making it elliptical or rod-shaped by a cylindrical lens and changing the aperture ratio of the objective lens. For example, by using an objective lens having an aperture ratio of 0.1 or more and 0.95 or less, the beam irradiation diameter becomes 0.7
It can be controlled up to about 6 μm. By making the beam shape before entering the objective lens asymmetrical with respect to the center, the NA of the objective lens can be substantially reduced in the direction of the minor axis, and the condensing width can be several μm. From several tens of μm
Can be controlled.

In the present invention, an aluminum alloy plate or a glass substrate is usually used as the non-magnetic substrate.
A metal substrate such as copper or titanium, a ceramic substrate, a resin substrate, or the like can also be used. The underlayer is a layer made of a nonmagnetic material, preferably a NiP alloy layer, and is usually formed by electroless plating or sputtering. Usually, a Cr layer is formed thereon, but projections can be formed on the Cr 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.
20,000 nm, particularly preferably 100-15,000
0 nm.

It is preferable that an intermediate layer such as a Cr layer or a Ti layer is provided on the underlayer between the magnetic layer and the intermediate layer.
0 nm. The magnetic layer provided on the underlayer or the intermediate layer is usually made of Co-P, Co-Ni-P, Co-Ni-C.
r, Co-Ni-Pt, Co-Cr-Ta, Co-Cr
-Pt, a ferromagnetic alloy thin film such as a Co-Cr-Ta-Pt-based alloy is formed by forming a thin film by a method such as electroless plating, electroplating, sputtering, and vapor deposition, and the film thickness is usually 15 nm. Above, about 70 nm or less is preferable.

A protective layer is provided on the magnetic layer.
As the protective layer, a carbon film, a hydrogenated carbon film, a carbide film such as TiC or SiC, a Si film by a method such as vapor deposition, sputtering, plasma CVD, ion plating, or a wet method.
Nitride film such as N, TiN, etc., SiO, Al ₂ O ₃ , ZrO
Is formed. Of these, carbon films and hydrogenated carbon films are particularly preferred. Further, a lubricant layer is usually provided on the protective layer.

[0031]

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 and 2, Comparative Example 1) NiP having a film thickness of 10 to 20 μm was formed on a disk-shaped aluminum alloy substrate having a diameter of 95 mm.
After plating, the surface was polished so that the surface roughness Ra became 1 nm or less. Next, an argon pulse laser whose intensity was accurately controlled as described in Table 1 was used.
Irradiation was performed on the disk substrate under the conditions described in (1) to form projections, thereby obtaining a magnetic disk substrate. Figures 3 and 5
FIG. 3 is a diagram showing the result of observing the surface shape of the NiP layer of the substrate obtained in Examples 1 and 2 using a surface shape measurement device (“ZYGO” manufactured by Zigo USA, USA) using laser interference. 4 and 6 show the cross-sectional shapes of the protrusions shown in FIGS. 3 and 5 in the laser beam sweep direction (a) and the perpendicular direction (b).

That is, the projection of the present invention has a characteristic shape as shown in FIGS. 3 to 6, and the top of the isolated projection is relatively flat in the direction perpendicular to the laser sweep direction. It has a trapezoidal shape, and has an appropriate curvature in the sweep direction. Next, a Cr intermediate layer (film thickness of 10) was sequentially formed on the NiP underlayer of the substrate by sputtering.
0 nm), Co-Cr-Ta alloy magnetic film (film thickness 50 n)
m) and a carbon protective film (thickness: 20 nm)
Thereafter, a fluorine-based liquid lubricant (trade name "DOL-2000" manufactured by Monte Edison) was applied to a film thickness of 2 nm by an immersion method to manufacture a magnetic recording medium.

FIGS. 7 and 8 show the protrusion shape of Comparative Example 1. The protrusion is long in the direction perpendicular to the laser sweep direction.
The top of the isolated protrusion has a moderate curvature in the laser sweep and its perpendicular direction. Table 1 shows the conditions when forming the protrusions and the measurement results (the linear velocity of the substrate, the laser intensity, the beam shape, the average irradiation time of the laser, and the average protrusion linear density in Examples 1 and 2 and Comparative Example 1). (Circumferential / radial direction), average projection height, each parameter of the projection shape, and the shape of the figure (projection horizontal cross-sectional shape) surrounded by contour lines at half the projection height. Note that the aperture ratio NA of the objective lens used for focusing the laser is all 0.1.
5 were used. The beam shape was defined at a portion of 84% of the energy peak value, and was measured with a CCD type beam profiler (“AnalyzerPC” manufactured by Coherent).

[0034]

Table 1 Table-1 ------------------------------------ Projection Horizontal linear velocity Intensity Irradiation Projection Projection shape Cross-sectional shape Time density Height shape (mm / sec) (mW) (μm) (μsec) (pcs / mm) (nm) p, q, r values ----- -------------------------------------------------- ----------------- Example 1 1800 500 1.5 x 10 1.6 50/25 15 5.3,0.81,0.48 Rod-shaped Example 2 1800 500 1.5 x 10 4.8 50/25 17 2.3 , 0.85, 0.64 rod-shaped Comparative Example 1 1800 500 1.5 x 3.0 1.6 100/50 15 2.5, 0.29, 0.15 rod-shaped --- --- --- --- --- --- --- --- --- --- --- --- −−−−−−−−−−−−

Table 2 shows the room temperature of these magnetic disks,
Static coefficient of friction before CSS test at normal humidity (initial stiction) The friction force after 20,000 times of CSS at high temperature, low humidity, and high temperature and high humidity was also shown. For the CSS test, an MR head (a slider material of Al ₂ O ₃ TiC coated with DLC) having a head flying height of 1.6 μ inch and a load gram of 3 gf was used. The stable flying height of the CSS area was 1.0 to 1.2 μ inch.

[0036]

[Table 2] Table 2---------------------------------Initial stiction CSS after 20,000 times (Coefficient of friction) Frictional force Normal temperature 60 degrees, 10% 40 degrees, 80% ------------------------------------------------------------------------------- −− Example 1 0.33 4gf 7gf Example 2 0.45 8gf 10gf Comparative Example 1 0.21 Head crash (1300 times) 3gf −−−−−−−−−−−−−−−−−−−−−−−−−− −−−−−−−−−−−−

As is evident from Table 2, the magnetic recording medium according to the present invention does not cause a head crash during wear at CSS even at high temperature and low humidity, and has extremely low friction even at high temperature and high humidity. It can be seen that the durability of the performance is excellent without increasing. The characteristics of the CSS vary depending on the subtle shape of the top of the protrusion. For example, even if the protrusion is long in the head running direction as in Comparative Example 1, if the top is relatively sharp, it can be used at high temperature and high humidity. Under the conditions, the CSS characteristics are good, but under the conditions of high temperature and low humidity, wear occurs as the number of times of CSS increases, and eventually the head crashes.

[0038]

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 protrusion, the cross-sectional area in the horizontal direction at the tip portion, the region where the protrusion 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, the friction during CSS is small, and since the projection structure is received on a large surface in the flight direction of the magnetic head, Good CSS characteristics can be obtained even in a state where wear is likely to occur, such as low humidity.

Further, if the density of the protrusions in the circumferential direction is increased and the CSS characteristics are not significantly deteriorated even if the density of the protrusions in the radial direction is reduced, there is an advantage that the time required for forming the protrusions can be reduced. Further, when such protrusions are formed only in the CSS area, the average surface height hardly changes. Therefore, when the magnetic head is sought between the data recording area and the CSS area, the stable flying height of the magnetic head is reduced. There is almost no fluctuation, and no head crash or instability in the head space occurs. Further, since the height and density of the projections 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, it is not necessary to make a surface flaw due to mechanical texture for the purpose of improving CSS as in the prior art, so that the flying height of the magnetic head can be reduced, and Since data errors are also reduced, high-density magnetic recording media can be manufactured, which is of great industrial significance.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating the shape of crater-shaped irregularities on the surface of a magnetic recording medium.

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

FIG. 3 is a view showing the shape of protrusions on the surface of the NiP substrate of the substrate obtained in Example 1 observed by a surface shape measuring device.

FIG. 4 is a diagram showing a shape of a cross section perpendicular to a substrate surface of a protrusion shown in FIG. 3;

FIG. 5 is a view showing the shape of protrusions on the surface of the NiP substrate of the substrate obtained in Example 2 observed by a surface shape measuring apparatus.

FIG. 6 is a diagram showing a shape of a cross section perpendicular to the substrate surface of the projection shown in FIG. 5;

FIG. 7 is a view showing the shape of protrusions on the surface of the NiP substrate of the substrate obtained in Comparative Example 1 observed by a surface shape measuring apparatus.

FIG. 8 is an explanatory diagram of a shape of a cross section perpendicular to the substrate surface of the protrusion shown in FIG. 7;

FIG. 9 is an explanatory diagram of a length parallel to and perpendicular to a running direction of a magnetic head according to the present invention.

FIG. 10 is an explanatory diagram of a length parallel to and perpendicular to a running direction of a magnetic head according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Projection 2 Depression 3 Pulse laser 4 Non-magnetic substrate 5 Spot part 6 Concave hole 7 Rim

Claims (8)

[Claims] 1. A magnetic recording medium having a magnetic layer on a nonmagnetic substrate or an underlayer provided on the substrate, wherein the height of the magnetic recording medium is 1 nm or more on the surface of the nonmagnetic substrate or the underlayer on the magnetic layer side. 5
A ratio P of a length of a cross section surrounded by a contour line at a height equal to or less than 0 nm of the protrusion height to a direction perpendicular to and parallel to the magnetic head running direction on the recording medium on the recording medium is 1 or more; 9/1 from the average roughness surface to the projection top
There are 10 or more and 10 ⁸ or less projections having a length ratio q in a direction perpendicular to the cross section of the projections surrounded by contour lines at heights of 0 and で of １ ／ or more per 1 mm ^{2 of} the surface. A magnetic recording medium, comprising: 2. The ratio of 9 / to the top of the projection from the average roughness surface
2. The magnetic recording according to claim 1, wherein a ratio r between a length of a section surrounded by a contour line at a height of 10 in a direction parallel to the running direction of the magnetic head and a length thereof at a height of 1/2 is 3/4 or less. Medium. 3. The magnetic recording medium according to claim 1, wherein the projection has a recess around the bottom. 4. An area where the magnetic head performs CSS (contact start and stop) (CSS area).
The magnetic recording medium according to claim 1, wherein the magnetic recording medium is present only in the magnetic recording medium. 5. The magnetic recording medium according to claim 1, wherein the height of the protrusion near the data area side of the CSS area gradually decreases toward the data recording area. 6. The magnetic recording medium according to claim 1, wherein the projection is formed by irradiation with energy rays. 7. The magnetic recording medium according to claim 6, wherein a vertical cross-sectional shape passing through the center of the projection and parallel to the scanning direction of the irradiation energy beam has a recess near one side of the bottom of the projection. 8. A magnetic recording medium having a magnetic layer on a nonmagnetic substrate or an underlayer provided on the substrate, wherein the height of the magnetic recording medium is 1 nm or more on the magnetic layer side surface of the nonmagnetic substrate or the underlayer. 5
0 nm or less, the ratio p of the length in a direction perpendicular to and parallel to the running direction of the magnetic head on the recording medium in a cross section surrounded by a contour line at a height of 突起 of the protrusion height is 1 or more; 9/1 from the average roughness surface to the projection top
There are 10 or more and 10 ⁸ or less projections having a length ratio q in the perpendicular direction of the projection cross section surrounded by the contour lines at heights of 0 and で of １ ／ or more per 1 mm ^{2 of} the surface. A substrate for a magnetic recording medium, comprising: