JPH0927109A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease noise during recording with high recording density by forming projections on the surface of a nonmagnetic substrate and forming a magnetic layer thereon to form a specified structure of the projections and the magnetic layer. SOLUTION: The magnetic recording medium 10 is produced by forming a magnetic layer 16 on a nonmagnetic substrate 14 having lots of projections 12 on the surface. The magnetic recording medium 10 satisfies the conditions I-IV, wherein (a) is the average grain size in the magnetic layer 16, (b) is the average diameter when the shape of the projection 12 is made to approximate to a circle, and (d) is the distance between adjacent projections 12. Further, the medium has >=80kfci high recording density. Projections 12 are formed on the substrate of the magnetic recording medium 10 in order to improve the durability against CSS of the medium 10. The nonmagnetic substrate 14 is made of, for example, an Al substrate, NiP-plated Al alloy substrate or reinforced glass substrate.

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 more particularly to a magnetic recording medium with reduced noise during recording at high recording density.

[0002]

2. Description of the Related Art
The following methods (1) to (5) have been mainly used as a method for reducing the noise of the magnetic recording medium. (1) Effect of magnetic layer Increasing the Cr concentration in an alloy containing CoCr that forms the magnetic layer, or adding Ta, B, an oxide, or the like to the alloy. (2) Effect of Underlayer The average crystal grain size of the magnetic layer is made fine by controlling the columnar structure in the underlayer, and the c-axis in-plane orientation is controlled by controlling the crystal orientation of the underlayer. (3) Effect of Heating Temperature Substrate heating or heat treatment promotes segregation of nonmagnetic substances such as Cr to the magnetic crystal grain boundaries, and weakens magnetic coupling between the magnetic crystal grains. (4) Effect of Ar gas pressure When forming a magnetic layer by sputtering, by forming the magnetic layer under a high Ar gas pressure, physical voids are created between the magnetic crystal grains, and magnetic gaps between the magnetic crystal grains are formed. Weaken the bond. (5) Effect of Magnetic Multilayer Film By interposing a non-magnetic intermediate layer between magnetic layers, magnetic coupling between magnetic crystal grains is weakened.

Noise is reduced by using the above methods (1) to (5) in combination. However,
As the recording density further increases, further noise reduction is required.

Therefore, an object of the present invention is to provide a magnetic recording medium which can achieve further noise reduction.

[0005]

The inventors of the present invention have earnestly studied a new method for realizing noise reduction in addition to the conventional method for reducing noise, and as a result, have formed a convex portion on the surface of a non-magnetic substrate. By forming the magnetic layer on top of this, and by forming the projection and the magnetic layer in a specific structure, noise at high recording density (especially 80 kfci or more) is not formed by the projection. It has been found that it can be extremely lowered as compared with the magnetic recording medium.

The present invention has been made based on the above findings, and in a magnetic recording medium in which a magnetic layer is formed on a non-magnetic substrate having convex portions formed on the surface, the average crystal grain size of the magnetic layer is a, an average diameter b when the shape of the convex portion is approximated to a circle, and a distance d between the adjacent convex portions satisfy the following relationship and have a high recording density of 80 kfci or more. The above object has been achieved by providing a medium. 2 nm ≦ a ≦ 30 nm 30 nm ≦ b ≦ 400 nm b ≧ 2a 0 <d ≦ b

The magnetic recording medium of the present invention is useful as, for example, a magnetic drum or a magnetic tape, but is particularly useful as a magnetic disk such as a fixed disk.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The magnetic recording medium of the present invention will be described below with reference to the drawings. Here, FIG. 1 is a schematic diagram showing the structure of the magnetic recording medium of the present invention, FIG. 2 is a schematic diagram showing the structure of a preferred embodiment of the magnetic recording medium of the present invention, and FIG. It is a schematic diagram which shows the structure of the other preferable Example of the magnetic recording medium of invention.

As shown in FIG. 1, the magnetic recording medium 10 of the present invention comprises a magnetic layer 16 formed on a non-magnetic substrate 14 having a large number of protrusions 12 formed on the surface thereof. In the magnetic recording medium 10, as shown in FIG. 1, the average crystal grain size a of the magnetic layer 16 and the convex portion 12 are
The average diameter b when the shape is approximated by a circle and the distance d between the adjacent convex portions 12 satisfy the following relationship, and
It is characterized by having a high recording density of 0 kfci or more. 2 nm ≦ a ≦ 30 nm 30 nm ≦ b ≦ 400 nm b ≧ 2a 0 <d ≦ b

The formation of concavities and convexities on the substrate of a magnetic recording medium is described in, for example, Japanese Patent Laid-Open No. 3-73419, but in that publication, the concavities and convexities form the CSS durability of the magnetic recording medium. It is intended to improve the magnetic property, and is not intended to reduce the noise of the magnetic recording medium like the present invention.

The magnetic recording medium 10 of the present invention shown in FIG. 1 will be further described. In FIG. 1, the non-magnetic substrate indicated by reference numeral 14 is, for example, an Al substrate or NiP plated Al.
Alloy substrate, tempered glass substrate, crystallized glass substrate, ceramics substrate, Si alloy substrate, Ti substrate, Ti alloy substrate,
A plastic substrate, a carbon substrate, a substrate made of a composite material of these, or the like can be used. In particular, carbon substrate,
Above all, the glassy carbon substrate is advantageous in reducing the diameter / thin plate, has excellent heat resistance, and has electrical conductivity, and is therefore preferably used in the present invention.

The projection 12 formed on the surface of the non-magnetic substrate 14 has a shape satisfying the above relationship.
The convex portion 12 is not particularly limited in its forming method as long as it satisfies such conditions.

The method of forming the protrusions 12 will be further described. On a non-magnetic substrate having a predetermined average surface roughness Ra, wet plating means such as electroless plating method; vapor deposition method, ion plating method or sputtering method. Physical vapor deposition (PVD) such as; or chemical vapor deposition (CV)
A method of forming the convex portion 12 by D) or the like can be given.
In this case, as the material forming the convex portion 12, for example, a low melting point metal such as Ag, Al, Au, Cu, Sn and In, and alloys thereof; a metal having a carbide forming ability; Al-M (M Can be a metal alloy having a carbide forming ability; silica [Si (O)] or the like.
Examples of the metal capable of forming a carbide include Si, Cr, Ta, Ti, Zr, Y, Mo, W and V. In this case, the thickness of the convex portion 12 (that is, the height of the convex portion 12) is 5 to 60 nm.
It is preferred that

The convex portion 12 thus formed
As described above, the average diameter b when the shape is approximated to a circle is 30 nm ≦ b ≦ 400 nm. The average diameter b
Is less than 30 nm, it becomes difficult to form discontinuous protrusions in the magnetic layer, and when the average diameter b exceeds 400 nm, spacing loss between the medium and the magnetic head becomes too large. The preferable range of the average diameter b is 50 nm.
≦ b ≦ 300 nm, more preferably 50 n
m ≦ b ≦ 200 nm. The average diameter b is
For example, the non-magnetic substrate 14 on which the projections 12 are formed is formed.
AFM (atomic force microscope) after cutting into a predetermined shape
It can be measured by observing the image.

The distance d between the adjacent convex portions 12 is 0 <d ≦ b as described above. That is, the individual projections 12 are substantially discontinuous on the surface of the non-magnetic substrate 14, and as a result, the projections 12 have a so-called island structure. Therefore, for example, when the convex portion 12 is made of an Al-M-based alloy formed on the surface of the non-magnetic substrate 14, the surface of the non-magnetic substrate 14 is covered with the alloy to form an island structure. There are portions and portions that are not covered by the alloy and whose surface is exposed.
The distance d between the adjacent convex portions 12 is equal to or less than the average diameter b. When the distance d exceeds the average diameter b,
The effect of low noise is diminished. The distance d between the convex portions 12 is preferably 2 to 200 nm.

The average surface roughness Ra of the protrusions 12 is not particularly limited, but is preferably 1 to 30 nm from the viewpoint of reducing the spacing with the magnetic head and achieving high recording density. More preferably, it is 20 nm.
As for the average surface roughness Ra, similar to the average diameter b, the AFM (atomic force microscope) image is observed after the nonmagnetic substrate 14 on which the protrusions 12 have been formed is cut into a predetermined shape. It can be measured by

Next, the magnetic layer 16 formed on the non-magnetic substrate 14 on which the convex portion 12 is formed will be described with reference to FIG. As shown in FIG. 1, the magnetic layer 1
6 is formed on the non-magnetic substrate 14 on which the convex portion 12 is formed, and has an uneven shape corresponding to the shape of the convex portion 12. The magnetic layer 16 is preferably made of
As shown in FIG. 1, it is an aggregate of discontinuous convex portions 18 corresponding to the convex portions 12 in the surface direction of the non-magnetic substrate 14. That is, there is a substantially discontinuous area between the adjacent convex portions 18, and the individual convex portions 18 are physically separated from each other. Since the magnetic layer 16 is an assembly of such discontinuous convex portions 18, the adjacent convex portions 18 are in a magnetically very weakly coupled state, so that the medium noise is further reduced. . At this time, the average crystal grain size a of the magnetic layer 16 is 2 nm ≦, as described later.
It is essential that a ≦ 30 nm, but the magnetic layer having such an average crystal grain size can be easily formed by controlling the type of metal (alloy) forming the magnetic layer and the conditions at the time of forming the magnetic layer. Can be formed.

In this case, the distance x between the adjacent magnetic layers (that is, the distance between the convex portions 18) is 0.2 ≦ x.
It is preferable that ≦ 30 nm. The distance x is 0.2n
If it is less than m, the magnetically coupled state between adjacent convex portions may be increased, which may lead to an increase in medium noise.
If the distance x exceeds 30 nm, the number of magnetic fluxes per unit area decreases, which may reduce the output. The distance x is 0.2
More preferably, ≦ x ≦ 10 nm. The distance x is, for example, a TEM (transmission electron microscope) in a longitudinal section and an in-plane of the magnetic recording medium on which the magnetic layer 16 is formed.
It can be measured by observing the image. Also,
The range of the distance x can be controlled by controlling the shape of the convex portion 12.

The magnetic layer 16 will be further described below.
As described above, the average crystal grain size a of the magnetic layer is 2 nm ≦
a ≦ 30 nm. If the average crystal grain size a is less than 2 nm, the magnetism of the magnetic crystal grains may become unstable,
If the average crystal grain size a exceeds 30 nm, it is disadvantageous at high recording density. Here, the average crystal grain size a is the average grain size of the magnetic crystal grains in each convex portion 18 of the magnetic layer 16 (therefore, the convex portion 18 is the magnetic crystal grain). Is a collection of). In the magnetic layer 16 of the magnetic recording medium 10 shown in FIG.
Has a columnar structure similarly to the magnetic crystal grains in a general magnetic layer formed by a thin film forming means such as PVD, and the average grain size corresponds to the diameter of the cross section in the columnar structure. . The average crystal grain size a is, for example, AFM
It can be measured by observing an image or an HR-SEM (high resolution scanning electron microscope) image.

The average crystal grain size a of the magnetic layer 16 has a relationship of b ≧ 2a with the average diameter b of the protrusions 12 described above. That is, as described above, the average crystal grain size a and the average diameter b are within the respective specific numerical ranges, but in addition to this, there is a relative relationship between them. Due to such a relationship between the two, the magnetic recording medium of the present invention has an effect of lowering noise at high recording density as compared with a medium in which the convex portions 12 are not formed.

The magnetic recording medium of the present invention exerts its effect particularly in a high recording density medium of 80 kfci or more.
In particular, in a high recording density medium of 90 kfci or more, especially 100 kfci or more, noise is significantly lower than that of a medium having a continuous magnetic layer.

The magnetic layer 16 is formed by a known thin film forming means,
For example, PVD such as a vapor deposition method, a sputtering method, and an ion plating method, or CVD can be used. In addition, examples of the material forming the magnetic layer 16 include CoCr, CoNi, CoCrX, and CoCr.
PtX, CoSm, CoSmX, CoNiX and CoW
X (where X is Ta, Pt, Au, Ti, V, C
r, Ni, W, La, Ce, Pr, Nd, Pm, Sm,
Eu, Li, Si, B, Ca, As, Y, Zr, Nb,
Mo, Ru, Rh, Ag, Sb, Hb, and the like, showing one or more metals selected from the group consisting of Hf, etc., and containing Co as a main component) Preferable examples include Co-based magnetic alloys and ferrite-based magnetic materials such as Ba-ferrite, Sr-ferrite, γ-ferrite, and Co-γ-ferrite.
Upon use, these can be used alone or in combination of two or more.

Next, the magnetic recording medium of the present invention will be described based on its preferred embodiment shown in FIG. Note that the same points as those in FIG. 1 will not be described in detail, but the description in detail regarding FIG. Further, in FIG. 2, the same members as those in FIG. 1 are designated by the same reference numerals as those in FIG.

The magnetic recording medium 10 shown in FIG. 2 is provided with a large number of convex portions 12 which are discontinuous in the plane direction of the nonmagnetic substrate 14 on the nonmagnetic substrate 14. And the convex portion 1
An amorphous layer 24 is provided on the amorphous layer 24, and a first underlayer 26 and a second underlayer 28 are provided on the amorphous layer 24.
Are sequentially provided. Further, the magnetic layer 16 is provided on the second underlayer 28, and the protective layer 30 and the lubricant layer 32 are sequentially provided on the magnetic layer 16.

The magnetic recording medium shown in FIG. 2 will be described in more detail. The amorphous layer denoted by reference numeral 24 preferably contains 3B to 5B elements.
It is composed of B, C, Si, P and the like. The amorphous layer 24 has an effect that the upper layer is not affected by the surface condition of the convex portion 12. This makes it easy to independently design the material forming the convex portion 12 and the material for controlling the magnetic film (that is, the material forming the underlayer described later).

Since the amorphous layer 24 has the above-mentioned function, the convex portion 12 and the magnetic layer 16 are provided.
It is preferable that it is formed directly on the convex portion 12 [particularly, on the convex portion 12 made of Si (O)] as shown in FIG. It is preferable from the viewpoint of further improving the squareness ratio.

The method for forming the amorphous layer 24 is not particularly limited. For example, when an amorphous carbon layer is used as the amorphous layer 24, it can be formed by PVD using a carbon material as a target. A crystalline carbon material such as graphite can be used as the carbon material, but a glassy carbon material is preferably used. Further, the carbon material is Si, Ti, W, Zr, C.
It is also preferable to contain a carbide, nitride, boride or oxide such as r, Nb, Mo, Ta or Al, or ceramic particles such as BN or B ₄ C. Generally, the thickness of the amorphous layer is preferably 5 to 50 nm.

Next, each of the first underlayer 26 and the second underlayer 28, which are sequentially provided on the amorphous layer 24, will be described. The first underlayer 26 is provided for the purpose of further reducing the medium noise. That is
It is preferably composed of Ti or a Ti alloy. On the other hand, the second underlayer 28 is provided for the purpose of improving the magnetostatic characteristics of the magnetic layer 16.
For this purpose, it is preferable to use a material having a lattice constant close to that of the substance forming the magnetic layer 16. In particular, it is preferable that the second underlayer 28 is made of Cr or a binary alloy containing Cr from the viewpoint of improving magnetostatic characteristics and reducing medium noise. Examples of the binary alloy containing Cr include CrTi, CrMo, CrW, CrNb,
Examples thereof include CrSi, CrCo, CrTa, and the like.
The thicknesses of the first underlayer 26 and the second magnetic layer are preferably 5 to 200 nm and 5 to 150 nm, respectively. The first base layer 26 and the second base layer 28 are
Both can be formed, for example, by PVD or the like.

Next, the protective layer 30 provided on the magnetic layer 16 will be described. The protective layer 30 is preferably made of a material having high mechanical strength from the viewpoint of abrasion resistance, and concretely, As a typical material, for example, A
1, oxides of metals such as Si, Ti, Cr, Zr, Nb, Mo, Ta and W (silicon oxide, zirconium oxide, etc.);
One or more selected from the group consisting of a nitride (boron nitride, etc.) of the metal; a carbide (silicon carbide, tungsten carbide, etc.) of the metal; carbon (carbon) such as diamond-like carbon and boron nitride. It is preferable. Among the above materials, carbon, silicon carbide, tungsten carbide, silicon oxide, zirconium oxide, boron nitride or a composite material thereof is preferable, carbon is more preferable, and diamond-like carbon and glassy carbon are particularly preferable. It should be noted that hydrocarbon such as hydrogen or methane may be mixed as a gas at the time of forming the carbon protective layer to form a hydrogenated carbon protective layer. The thickness of the protective layer 30 is generally 5 to 2
Preferably it is 5 nm. The protective layer 30
Can be formed by PVD or the like.

Next, the lubricant layer 32 provided on the protective layer 30 will be described.
It is used for improving the running property and durability of the magnetic recording medium. For example, a lubricant is applied by a coating means such as spin coating, dip coating, or spray coating so as to have a thickness of about 5 to 100Å. Method or a method of vapor phase polymerization (especially photo-CVD) of a fluorocarbon compound and oxygen (for example, Japanese Patent Application No. 6-28694).
No. 0) and the like). As the lubricant, a fluoropolymer can be preferably used. As the fluorine-based polymer, both those having a polar group in the molecule and those not having a polar group can be used alone or in combination. The fluoropolymer having a polar group in the molecule has a molecular weight of 2000 to
A 4000 perfluoropolyether polymer having an aromatic ring or an OH group at its terminal is preferably used. More _{particularly, - (CF 2 CF 2 O} ) n-
(CF ₂ O) m-skeleton with an aromatic ring or OH at the end
Those having a group and having a molecular weight of 2000 to 4000 are preferable. As a specific example, the Fomblin AM200
1, Fomblin Z-dol (Aojimont) and the like. On the other hand, as the fluoropolymer having no polar group in the molecule, a perfluoropolyether polymer having a molecular weight of 2000 to 10000 and having a perfluoroalkyl group at the terminal is preferably used. More _{specifically, CF 3 - (CF 2 CF} 2 O) n-
It is represented by (CF ₂ O) m-CF ₃ and has a molecular weight of 2000.
It is preferably from 1 to 10,000. As a specific example,
Fomblin Z03 (Aozimont) and the like can be mentioned.

Next, the magnetic recording medium of the present invention will be described based on another preferred embodiment shown in FIG. Note that the same points as those in FIG. 1 will not be described in detail, but the description in detail regarding FIG. Further, in FIG. 3, the same members as those in FIG. 1 are designated by the same reference numerals as those in FIG.

The magnetic recording medium 10 shown in FIG. 3 is similar to the magnetic recording medium shown in FIG. 2, but the distance d between the adjacent convex portions 12 is larger than that of the magnetic recording medium shown in FIG. (Note that d also satisfies the above relational expression in this embodiment). As a result, between the protrusions 12, the amorphous layer 24, the first underlayer 26, the second underlayer 28, the magnetic layer 16, the protective layer 30, and the lubricant layer 32 are sequentially laminated on the substrate 14. There is. Also in this embodiment, the distance between the adjacent magnetic layers (distance between the convex portions) x is as shown in FIG.
For the same reason as the example shown in FIG.
m is preferable.

As described above, in the magnetic recording medium of the present invention, the magnetic layer has a discontinuous convex portion and / or a discontinuous flat portion corresponding to the convex portion in the plane direction of the non-magnetic substrate. It is preferable that the aggregate includes

Although the preferred embodiments of the magnetic recording medium of the present invention shown in FIGS. 2 and 3 have been described above, the magnetic recording medium of the present invention is not limited to such embodiments, and various modifications can be made. It is possible. For example, the convex portion 1
After forming the amorphous layer 24 directly on the second
The second underlayer 28, the magnetic layer 1 without providing the underlayer 26
6, the protective layer 30 and the lubricant layer 32 may be sequentially formed. In addition, the first base layer 26 is directly formed on the convex portion 12 without providing the amorphous layer 24, and then the second base layer 26 is formed.
Underlayer 28, magnetic layer 16, protective layer 30, and lubricant layer 32
May be sequentially formed, or on the convex portion 12,
The second underlayer 28, the magnetic layer 16, the protective layer 30, and the lubricant layer 32 may be sequentially formed directly without providing the amorphous layer 24 and the first underlayer 26.

[0035]

EXAMPLES The magnetic recording medium of the present invention will be described in detail below with reference to specific examples.

Example 1 A magnetic recording medium having the structure shown in FIG. 2 was manufactured by the following procedure. That is, density 1.5g
/ Cm ³ of amorphous carbon substrate (size 2.
5 ″) and the average surface roughness Ra thereof is 0.5 to 1.
It was set to 0 nm. After precision cleaning of the carbon substrate, the carbon substrate was placed in a high vacuum electron beam vapor deposition apparatus, and a convex portion was first formed by the following procedure.

As the vapor deposition base material, Si degassed in a vacuum arc furnace was used. After mounting the carbon substrate in the apparatus and setting the Si base material in the hearth, the inside of the chamber was evacuated to a vacuum of 5 × 10 ⁻⁸ Torr or less. The temperature of the carbon substrate was set to 100 ° C. Next, in a high vacuum state, the Si base material was heated by an electron beam to degas. At this time, the shutter in the chamber was closed to prevent the vapor deposition film from adhering to the carbon substrate. After the degassing was completed, the inside of the chamber was evacuated again and the vacuum was reduced to 5 × 10 ⁻⁸ Torr or less. Next, after introducing Ar and O ₂ mixed gas into the chamber to 1 × 10 ⁻⁶ Torr, vapor deposition of Si was started. The film thickness of vapor-deposited Si (the above-mentioned convex portion) was measured by a film thickness monitor that had been calibrated. The film forming conditions are shown below.

(1) Convex portion-Material: Si (O) -Film thickness: 5 nm

When the convex portion reached the set film thickness, the shutter was closed and the vapor deposition was completed. Stop the above mixed gas,
After continuing the water cooling for 1 hour or more, the inside of the chamber is filled with N ₂
The carbon substrate leaked and the above-mentioned convex portion was formed was taken out.

Next, a cathode of a batch type sputtering apparatus having 4 cathodes was provided with a T of 5 ″ φ × 3 mmt.
Targets of i, Cr, CoCr ₁₂ Pt ₈ B ₄ at% and C were set. After setting the carbon substrate on which the convex portions were formed in the above apparatus, the inside of the sputtering chamber was evacuated and evacuated to 3 × 10 ⁻⁷ Torr or less. After introducing Ar gas to 5 mTorr, the carbon substrate was heated to 240 ° C. by a heater to form each layer in the following order.

(2) Amorphous layer-Material: C-Substrate bias voltage: -100V-Film thickness: 20 nm

(3) First Underlayer-Material: Ti-Substrate Bias Voltage: -100V-Film Thickness: 50nm (4) Second Underlayer-Material: Cr-Substrate Bias Voltage: -100V-Film Thickness: 40nm ( 5) magnetic layers and _{materials: CoCr 12 Pt 8 B 4 at} % · substrate bias voltage: -100 V, the film thickness: 30 nm (6) protective layer, materials: C-substrate bias voltage: -100 V, the film thickness: 15 nm

After forming the protective layer, Ar gas was stopped and the carbon substrate was left to stand until the temperature became 50 ° C. or lower. Then, the inside of the sputtering chamber was leaked with N ₂ , and the carbon substrate having the protective layer formed was taken out. In addition, tape burnish, followed by lubricant Fomblin A
M2001 (manufactured by Aojimont Co., Ltd.) was applied to a film thickness of 2 nm to obtain a magnetic recording medium having the structure shown in FIG.

The following evaluations were carried out on the obtained magnetic recording medium. Table 1 shows the results.

<Average Diameter b of Protrusions, Distance d between Protrusions, and Average Roughness Ra> A carbon substrate on which the protrusions have been formed is cut into a shape of about 8 × 8 mm, and then an AFM image shows that
The measurement was performed with a size of 10 × 10 μm.

<Average crystal grain size a of magnetic layer and distance x between convex portions> The average crystal grain size a was measured by an AFM image and an HR-SEM image of the carbon substrate on which the magnetic layer was formed. . The distance x between the convex portions was measured by a TEM image of a vertical cross section of the carbon substrate on which the magnetic layer was formed.

<Static Magnetostatic Characteristics and Noise of Magnetic Recording Medium>
The magnetostatic characteristics of the magnetic recording medium are about 8
After cutting into a shape of × 8 mm, measurement was performed with a maximum applied magnetic field of 10 kOe using a VSM (vibrating sample magnetometer). In addition, the noise of the magnetic recording medium is measured by using an inductive head, using a Guzik (recording / reproducing evaluation device),
The measurement was performed with an oscilloscope and a spectrum analyzer.

Example 2 The same measurement as in Example 1 was carried out except that the magnetic recording medium obtained in Example 1 had a recording density of 100 kfci (the shortest recording bit length was 254 nm). Table 1 shows the results.

[Embodiment 3] The thickness of the Si (O) film on the convex portion is set to 1
A magnetic recording medium was produced in the same manner as in Example 1 except that the thickness was set to 0 nm. The same measurement as in Example 1 was performed on this magnetic recording medium. Table 1 shows the results.

Example 4 The same measurement as in Example 1 was carried out except that the magnetic recording medium obtained in Example 3 had a recording density of 100 kfci (the shortest recording bit length was 254 nm). Table 1 shows the results.

Comparative Example 1 A magnetic recording medium was produced in the same manner as in Example 1 except that Si was not vapor-deposited and no convex portion was formed. The same measurement as in the example was performed on this magnetic recording medium. Table 1 shows the results.

Comparative Example 2 The same measurement as in Example 1 was carried out except that the recording density of the magnetic recording medium obtained in Comparative Example 1 was 100 kfci (the shortest recording bit length was 254 nm). Table 1 shows the results.

[Comparative Example 3] The substrate temperature during the formation of the protrusions was set to 26.
A magnetic recording medium was produced in the same manner as in Example 1 except that the temperature was 0 ° C. The same measurement as in the example was performed on this magnetic recording medium. Table 1 shows the results.

Comparative Example 4 The same measurement as in Example 1 was carried out except that the recording density of the magnetic recording medium obtained in Comparative Example 3 was 100 kfci (the shortest recording bit length was 254 nm). Table 1 shows the results.

[0055]

[Table 1]

As is clear from the results shown in Table 1, in the magnetic recording media of the present invention obtained in Examples 1 to 4, noise at a recording density of 100 kfci (shortest recording bit length 254 nm) was 2.3 to 2. It can be seen that it is extremely reduced to 8 μVrms. On the other hand, the distance between convex parts d
Of 0 for magnetic recording media (Comparative Examples 1 and 2), distance d between convex portions
In the magnetic recording media (Comparative Examples 3 and 4) having an extremely large
It can be seen that the noise at the same recording density is extremely large at 4.1 to 4.3.

[0057]

As described above in detail, in the magnetic recording medium of the present invention, the convex portion is formed on the surface of the non-magnetic substrate,
By forming a magnetic layer on this and forming the convex portion and the magnetic layer into a specific structure, noise at high recording density is significantly reduced as compared with a magnetic recording medium in which the convex portion is not formed. Can be made.

[Brief description of drawings]

FIG. 1 is a schematic view showing a structure of a magnetic recording medium of the present invention.

FIG. 2 is a schematic view showing the structure of a preferred embodiment of the magnetic recording medium of the present invention.

FIG. 3 is a schematic view showing the structure of another preferred embodiment of the magnetic recording medium of the present invention.

[Explanation of symbols]

 10 magnetic recording medium 12 convex part 14 non-magnetic substrate 16 magnetic layer 18 convex part 20 magnetic crystal grains 24 amorphous layer 26 first underlayer 28 second underlayer 30 protective layer 32 lubricant layer

Claims (4)

[Claims] 1. In a magnetic recording medium having a magnetic layer formed on a non-magnetic substrate having convex portions formed on its surface, the average crystal grain size a of the magnetic layer and the shape of the convex portions are approximated to a circle. And the average diameter b and the distance d between the adjacent convex portions.
Satisfying the following relation and having a high recording density of 80 kfci or more. 2 nm ≦ a ≦ 30 nm 30 nm ≦ b ≦ 400 nm b ≧ 2a 0 <d ≦ b 2. The magnetic layer is an aggregate including a discontinuous convex portion and / or a discontinuous flat portion corresponding to the convex portion in the surface direction of the non-magnetic substrate. Magnetic recording medium. 3. The distance x between adjacent magnetic layers is 0.2 ≦
The magnetic recording medium according to claim 2, wherein x ≦ 30 nm. 4. Between the convex portion and the magnetic layer 3B-5.
The amorphous layer containing B element is formed.
4. The magnetic recording medium according to any one of claims 1 to 3.