JPH117626A - Magnetic recording medium and recording / reproducing method thereof - Google Patents

Abstract

(57) [Summary] A material used for a ferromagnetic layer is rarely limited, and high-density and sharp recording can be performed, and recording and reading (reproduction) can be repeatedly performed. A long-life magnetic recording medium is provided. Further, the present invention provides a magnetic recording medium which can be used as a polarizer and can be used as a display because an image can be viewed by applying light and a magnetic field. SOLUTION: A substrate 1, a plurality of grooves 3 formed on the surface of the substrate and having a side wall surface 2 perpendicular to the substrate surface, the side wall surfaces 2 being parallel to each other, and a height formed on the side wall surface of the groove 0.1
The ferromagnetic layer 4 has a thickness of 5 μm to 5 μm and a thickness of 5 nm to 200 nm.
A magnetic recording medium formed so as to be equally spaced (L1 = L2) in the range of μm to 2.0 μm.

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 high-density magnetic recording medium capable of repeatedly performing recording, reading (reproducing), and erasing with a magnetic head and a laser beam. The present invention also relates to a magnetic recording medium which is excellent in transparency, can be used as a polarizer, and is suitable for application to a display or the like which can be viewed by applying a magnetic field and light.

[0002]

2. Description of the Related Art With the development of the information-oriented society, the demand for high-density information recording media capable of storing a large amount of information and inputting / outputting at high speed is increasing, and perpendicular magnetic recording media is being studied as one of them. . The ferromagnetic layer of the perpendicular magnetic recording medium has C
Materials with large perpendicular magnetic anisotropy, such as an o-Cr film and a Ba ferrite film, have been developed. However, it is necessary to develop a material having a larger perpendicular magnetic anisotropy. There is a disadvantage that the materials used are limited. When a conventional perpendicular magnetic recording medium is magnetized and recorded perpendicularly to the ferromagnetic layer surface, the magnetized portion spreads in a direction parallel to the ferromagnetic layer surface. However, it is difficult to perform high-density and sharp recording. Further, in order to perform high-density recording on a perpendicular magnetic recording medium, it is necessary to strongly press the magnetic head against the surface of the ferromagnetic layer, which has the disadvantage that the ferromagnetic layer is scraped and the life of the perpendicular magnetic recording medium is shortened. Was.

When a magnetic material is magnetized and linearly polarized light is incident parallel to the magnetization direction, the plane of polarization of the linearly polarized light is rotated by passing through the magnetic material, and this is known as the Faraday effect. A magnetic recording medium, a light modulation element, and the like are manufactured using a material having the Faraday effect. For example, (1) JP-A-56-15125
No. 1 discloses a magnetic recording medium using yttrium and rare earth iron garnet and its derivatives.
No. 05 has a magnetic recording medium using hexagonal ferrite,
(3) Japanese Patent Application Laid-Open No. 62-119758 discloses a coating type magnetic recording medium using yttrium iron garnet particles, and (4) Japanese Patent Application Laid-Open No. 4-132029 discloses a coating type magnetic recording medium using rare earth iron garnet fine particles. Is introduced.
These magnetic recording media have a structure in which a magnetic material or magnetic fine particles are formed as a thin-film recording layer on a substrate. According to these magnetic recording media, recording, reading (reproduction), and erasing can be performed satisfactorily. However, on the other hand, these magnetic recording media are limited to the use of the above-described recording, reading (reproducing), and erasing, and have a drawback that they are unsuitable for application / diversion to other uses.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve such a problem, to reduce the material used for the ferromagnetic layer and to perform high-density and sharp recording. Yes, recording and reading (reproduction)
Is to provide a long-life magnetic recording medium that can be repeatedly performed. Another object of the present invention is to provide a magnetic recording medium that can be used as a polarizer and that can be viewed as an image by applying a magnetic field and light and can be applied as a display.

[0005]

According to the present invention, first, a substrate, a plurality of grooves formed on the surface of the substrate and having a side wall surface perpendicular to the substrate surface, and the side wall surfaces are parallel to each other; It is formed of a ferromagnetic layer having a height of 0.1 μm to 5 μm and a thickness of 5 nm to 200 nm formed on the side wall surface of the groove, and the ferromagnetic layer extends in a direction of 0.2 μm to 2.0 μm across the groove. There is provided a magnetic recording medium characterized by being formed at equal intervals.

Secondly, there is provided a magnetic recording medium according to the first aspect, wherein the groove is filled with an inorganic or organic material and the surface of the magnetic recording medium is smooth. .

Thirdly, there is provided a magnetic recording medium according to the first or second aspect, wherein the substrate is transparent to laser light.

Fourth, there is provided a magnetic recording medium according to the second or third aspect, wherein the inorganic or organic material is transparent to laser light.

Fifth, in the magnetic recording medium according to any one of the first to fourth aspects, the ferromagnetic layer is made of Fe, Co,
A magnetic recording medium comprising ultrafine particles of Ni or an alloy of any combination thereof having an average particle diameter of 2 nm to 50 nm is provided.

Sixth, in the magnetic recording medium according to any one of the first to fifth aspects, there is provided a magnetic recording medium characterized in that a large number of grooves whose side wall surfaces are parallel to each other are linear grooves. Is done.

Seventh, in a magnetic recording medium recording method for recording information by applying a bias magnetic field to a magnetic recording medium and irradiating the magnetic recording medium with a laser beam, a substrate transparent to the laser beam and formed on the surface of the substrate. A number of grooves having side wall surfaces perpendicular to the substrate surface and having parallel side wall surfaces, and a height of 0.1 μm to 5 μm and a thickness of 5 μm formed on the side wall surfaces of the grooves.
a ferromagnetic layer of a magnetic recording medium formed of ferromagnetic layers having a thickness in the range of 0.2 μm to 2.0 μm in a direction crossing the groove. There is provided a recording method for a magnetic recording medium, wherein information is recorded by magnetizing in a direction perpendicular to a substrate surface.

Eighth, in the method for recording a magnetic recording medium according to the seventh aspect, a large number of grooves having side walls parallel to each other are linear grooves, and the grooves are discontinuous in the recording direction and perpendicular to the substrate surface. A method for recording information on a magnetic recording medium, comprising: using a magnetic recording medium having a magnetic layer, recording the information by magnetizing the ferromagnetic layer in the recording direction with one bit in the recording direction and perpendicular to the substrate surface. Is provided.

Ninth, in a method for reproducing information recorded on a magnetic recording medium by utilizing the rotation of the plane of polarization of the laser light applied to the magnetic recording medium, a substrate transparent to the laser light, A plurality of grooves formed on the surface of the substrate and having side walls perpendicular to the surface of the substrate and having mutually parallel side walls; and a height of 0.1 μm to 5 μm and a thickness of 5 nm to 200 nm formed on the side surfaces of the grooves. The ferromagnetic layers of the magnetic recording medium, which are formed at regular intervals in the range of 0.2 μm to 2.0 μm in the direction crossing the groove, are formed on the substrate surface. On the other hand, there is provided a method of reproducing a magnetic recording medium, characterized in that information is recorded by being magnetized in a perpendicular direction.

Tenth, a substrate transparent to visible light, a large number of linear grooves formed on one surface of the substrate and having a side wall surface perpendicular to the substrate surface, the side wall surfaces being parallel to each other; And a height of 0.1 μm to 5 μm formed on the side wall surface of the groove,
A magnetic recording layer comprising a ferromagnetic layer having a thickness of 5 nm to 200 nm, wherein the ferromagnetic layers are formed at regular intervals in a range of 0.2 μm to 2.0 μm across the groove. A medium is provided.

Eleventh, there is provided a magnetic recording medium according to the tenth aspect, wherein a light reflecting film is formed on a grooved surface of the substrate.

Twelfthly, there is provided a magnetic recording medium according to the tenth aspect, wherein a light reflecting film is formed on a surface of the substrate opposite to the surface having the grooves. You.

Thirteenth, in the magnetic recording medium according to the eleventh or twelfth aspect, an antireflection film is provided on a surface opposite to a surface on which the light reflection film is provided. A magnetic recording medium is provided.

Fourteenthly, there is provided a magnetic recording medium according to any one of the tenth to thirteenth aspects, wherein the ferromagnetic material has conductivity.

Fifteenth, in the magnetic recording medium according to any one of the tenth to fourteenth aspects, the ferromagnetic layer is made of Fe, C
A magnetic recording medium is provided, comprising ultrafine particles of an alloy of o, Ni or any combination thereof, having an average particle diameter of 2 nm to 50 nm.

Sixteenthly, in the magnetic recording medium according to any one of the tenth to fifteenth aspects, a nonmagnetic semiconductor layer or a nonmagnetic semiconductor layer having the same height and a thickness of 5 to 10 nm in contact with the ferromagnetic layer is provided. A magnetic recording medium provided with a metal layer is provided.

Seventeenthly, there is provided a magnetic recording medium according to any one of the first to sixteenth aspects, wherein the substrate is a plastic film.

The magnetic recording medium of the present invention has a substrate, a plurality of grooves formed on the surface of the substrate and having a side wall surface perpendicular to the substrate surface, the side wall surfaces being parallel to each other, and formed on the side wall surface of the groove. Height 0.1 μm to 5 μm, thickness 5 nm to 200
nm, and the ferromagnetic layers are formed at equal intervals in a range of 0.2 μm to 2.0 μm in a direction crossing the groove, whereby Since recording can be performed by magnetizing the ferromagnetic layer in the direction perpendicular to the substrate surface, high-density and sharp recording can be performed using a magnetic head or laser light, and the resolution is good. Reading (reproduction) can be performed favorably.

Further, according to the magnetic recording medium of the present invention, recording and reading (reproduction) thereof can be repeatedly performed,
The service life can be extended.

Further, the ferromagnetic layer in the magnetic recording medium of the present invention is formed perpendicular to the substrate surface (parallel to the side wall surface) and can be magnetized in the direction perpendicular to the substrate surface for recording. A magnetic material having magnetic anisotropy in a direction perpendicular to the substrate surface (a direction parallel to the side wall surface), that is, a magnetic material having in-plane magnetic anisotropy can be used. More magnetic material can be used. That is, it is not necessary to use a magnetic material having a particularly large perpendicular magnetic anisotropy, and the material used for the ferromagnetic layer is rarely limited.

In the magnetic recording medium of the present invention, the plurality of grooves whose side walls are parallel to each other may be linear, spiral, or concentric.

Further, in the magnetic recording medium of the present invention, a substrate transparent to visible light is used, and the ferromagnetic layers are arranged at regular intervals in the range of 0.2 μm to 2.0 μm across the groove. By forming a polarizer, it can be used also as a polarizer, and can be applied as a display because an image can be viewed by applying a magnetic field and light.
That is, a substrate transparent to visible light, a number of linear grooves formed on one surface of the substrate and having a side wall surface perpendicular to the substrate surface, the side wall surfaces being parallel to each other, and a side of the groove. 0.1 μm to 5 μm height, 5 nm thickness formed on the wall
A magnetic recording medium comprising a ferromagnetic layer having a thickness of from about 200 nm to about 200 nm, wherein the ferromagnetic layers are formed at equal intervals in a range of 0.2 μm to 2.0 μm in a direction crossing the groove. It can also be used as a polarizer, and can be applied as a display because an image can be viewed by applying a magnetic field and light.

According to the experiment, the light absorptivity depends on the thickness × height area of the ferromagnetic layer (in the case of the same material and the same area). However, even with the same area, the degree of polarization improves as the thickness is smaller and the height is higher, that is, the aspect ratio (height / thickness) is larger. In the present invention, a value having a polarization degree of 70% or more and close to 80% can be obtained.

According to the above-described magnetic recording medium, since the ferromagnetic layer is provided on a substrate transparent to visible light and arranged perpendicular to the substrate, high light transmittance and a polarization function can be simultaneously obtained. As a result, a high contrast is formed between the magnetized portion and the non-magnetized portion, and an image or the like can be recorded and observed in a large area.

The thickness of the ferromagnetic layer is 5 nm to 200 nm.
It is preferable that the magneto-optical effect is reduced to an unusable level when the thickness is less than 5 nm or exceeds 200 nm,
On the other hand, when the thickness exceeds 200 nm, the polarization function in the visible light region is reduced. Further, the thickness of the ferromagnetic layer is 200 nm.
When the value exceeds, the transparency is lowered and a light transmittance of 50% or more cannot be obtained.

The height of the ferromagnetic layer is suitably from 0.1 to 5 μm. Since the amplification of the polarization plane rotation angle by the magneto-optical effect can be controlled by this height, the contrast design of the image can be easily performed. When the height of the ferromagnetic layer is less than 0.1 μm, only the same effect (polarization function and magnetic function) as that of a general magnetic recording medium having a continuous layer of ferromagnetic material is exerted, and
When the thickness exceeds μm, the transparency is reduced and it is difficult to use the display as a display.

The distance between the ferromagnetic layers is 0.2 to 2 μm.
m is appropriate. When the layer spacing is less than 0.2 μm, the transparency is reduced, the polarizing function is reduced, and the use as a display or the like becomes difficult. When the distance between layers exceeds 2 μm, the polarizing function becomes the same as that of a continuous solid film of a ferromagnetic layer, and it is difficult to use it as a display or a polarizer.

Since the ferromagnetic layer is formed on the side wall surface perpendicular to the groove provided in the substrate, the ferromagnetic layer is formed to be perpendicular to the substrate surface. The vertical or equidistant terms in this specification have such meanings, since the bending, bending, and variations in the interlayer distance do not affect the functional aspect.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the drawings. FIG. 1 is an enlarged cross-sectional view schematically showing an example of the magnetic recording medium of the present invention. The substrate 1 has a plurality of straight lines having a side wall surface 2 perpendicular to the substrate surface and having side wall surfaces parallel to each other. And the height H formed on the side wall surface of the groove 3 is 0.1 μm to 5 μm, and the thickness M is 5 nm to 20 μm.
A ferromagnetic layer 4 having a thickness of 0 nm, and the ferromagnetic layers 4 are formed at equal intervals in a range of 0.2 μm to 2.0 μm in a direction crossing the groove at right angles. The ferromagnetic material layer 4 is formed such that the distance L1 between the ferromagnetic material layers formed on the substrate 2 and the width L2 of the substrate between the grooves are equal, and L1 and L2 are 0.2 μm to 2.0 μm.
It is in the range.

The substrate 1 may be formed of either an organic material or an inorganic material. Examples of the material include acrylic materials such as polyacrylate, polymethacrylate, polyacrylic acid, and polyacrylamide. Resin, polycarbonate resin, polystyrene, styrene resin such as ABS resin, polysulfone,
Polyether sulfone, polypropylene resin, polyarylate, epoxy resin, poly-4-methylpentene
1, fluorinated polyimide resin, fluororesin, phenoxy resin, polyolefin resin, diethylene glycol bisallyl carbonate, nylon resin, fluorene polymer, cellulose acetate, glass, quartz, alumina, aluminum, nickel, stainless steel, ceramics and the like. In a magnetic recording medium on which recording and reproduction are performed by laser light, a substrate made of a material transparent to laser light may be used.

The material of the ferromagnetic layer 4 in the magnetic recording medium of the present invention is preferably a magnetic material having magnetic anisotropy (in-plane magnetic anisotropy) parallel to the ferromagnetic layer, but is not limited thereto. Not done. Examples of the material of the ferromagnetic layer 4 include MnBi, γ-Fe ₂ O ₃ , Fe ₃ O ₄ , Ba ferrite, Pb ferrite, Co ferrite, rare earth iron garnet, PtCo, or Fe, Co, Ni, or any of these. Alloys, etc., by any combination are mentioned.

In particular, the ferromagnetic layer 4 includes Fe, Co, N
It is preferable to use ultrafine particles having an average particle diameter of 2 nm to 50 nm of an alloy made of i or an arbitrary combination thereof. By using these, interaction with new light such as a quantum size effect appears, and a large magneto-optical effect is obtained, and high-density recording with a large S / N can be easily obtained.

The groove 3 in the magnetic recording medium of the present invention
May be a space or may be filled with an inorganic or organic material as described below. Examples of the inorganic material include CaF ₂ , NaF ₂ , Na ₃ AlF ₆ , LiF,
MgF ₂ , SiO ₂ , LaF ₃ , NdF ₃ , Al ₂ O ₃ , Ce
F ₃ , PdF ₂ , MgO, ThO ₂ , SnO ₂ , La ₂ O ₃ ,
SiO, In ₂ O ₃ , Nd ₂ O ₃ , Sb ₂ O ₃ , ZrO ₂ , C
eO ₂ , TiO ₂ , ZnS, Bi ₂ O ₃ , ZnSe, Cd
S, Sb ₂ S ₃ , CdTe, Si, Ge, Te, PdTe
And the like, and as the organic material, for example, acrylic resin, epoxy resin, polyether sulfone resin,
Examples include polypropylene resin, acetyl acetate resin, fluorine resin, styrene resin, polycarbonate resin and the like.

In particular, in a magnetic recording medium on which recording and reproduction are performed by a magnetic head, the grooves 3 are preferably filled with an inorganic or organic material, and the surface 5 of the magnetic recording medium is preferably smooth. The surface can be prevented from being scraped by the contact of the magnetic head.
In a magnetic recording medium on which recording and reproduction are performed by laser light, the groove 3 needs to be filled with a space or a material that is transparent to laser light and has a different refractive index from the substrate.

In order to perform recording on the magnetic recording medium of the present invention by using a magnetic head, a so-called perpendicular magnetic recording medium, which has high sensitivity to magnetic flux in a direction perpendicular to the substrate surface, even with the most commonly used ring head. A head may be used, and an MR (magnetoresistive effect) head or a GMR (giant magnetoresistance effect) head may be used for reproduction. To erase the recording, a uniform magnetic field (upward, downward or lateral to the ferromagnetic layer) may be applied to the ferromagnetic layer, or an alternating magnetic field may be applied and the magnetic field may become zero. You may keep it away.

In order to perform recording on the magnetic recording medium of the present invention by laser light, a bias magnetic field is applied to the magnetic recording medium, the laser light is irradiated, and the ferromagnetic layer is magnetized in a direction perpendicular to the substrate surface. Often, this enables high-density and sharp recording.

The recorded information can be reproduced by irradiating the magnetic recording medium with reproduction laser light and utilizing the rotation of the polarization plane of the laser light. In addition, as a method of reproducing information recorded by a laser beam, a method of reading the direction of a magnetic flux with a magnetic head can be used. To erase the recording, a uniform magnetic field (upward, downward or lateral to the ferromagnetic layer) may be applied to the ferromagnetic layer, or an alternating magnetic field may be applied and the magnetic field may become zero. The recording may be performed by a method of irradiating a laser beam with the direction of the bias magnetic field being reversed in recording.

In the method of performing recording reproduction by applying linearly polarized laser light to the recording portion and using the rotation of the polarization plane, both sides of the magnetized ferromagnetic layer (the groove portion or the substrate portion forming the groove) are used. Recording can be reproduced by reading the rotation of the polarization plane of the laser light passing through the laser beam or the laser light reflected by the ferromagnetic layer. Also, by providing a light reflecting film on the surface of the substrate of the magnetic recording medium opposite to the laser light incident side, the polarization plane of the reflected laser light is further rotated and the rotation angle is increased. Reproduction can be performed better.

According to the magnetic recording medium of the present invention, unlike a conventional magnetic tape or magnetic disk, it has a ferromagnetic layer perpendicular to the substrate surface, so that the recorded magnetized portion can be miniaturized. And high-density and sharp recording can be performed. That is, in a conventional magnetic recording medium such as a magnetic tape or a magnetic disk, the magnetized portion spreads in a direction parallel to the surface of the ferromagnetic layer, but according to the magnetic recording medium of the present invention, the magnetized portion is formed on the substrate surface of the ferromagnetic layer. Since the direction can be limited to the perpendicular direction, the magnetized portion can be miniaturized, and high-density and sharp recording can be performed.

Further, in the magnetic recording medium of the present invention,
When using a magnetic recording medium in which a large number of grooves having side walls parallel to each other are linear grooves, and a ferromagnetic layer perpendicular to the substrate surface formed on the side walls is discontinuous in the recording direction, ,
Since the magnetized portion can be limited to each of the discontinuous ferromagnetic layers, the magnetized portion can be miniaturized, and the ferromagnetic layer formed on the side wall surface of the groove can be reduced by one bit in the recording direction. By recording as, high-density and sharp recording can be performed. When such high-density recording is reproduced by the above-described method, a reproduced signal having a good S / N ratio is obtained by a large magneto-optical effect (rotation of the polarization plane) due to the interaction between the ferromagnetic layer and the reproduced laser beam. Can be obtained.

In general, when a magnetic material is made thin, the magnetic anisotropy (in-plane magnetic anisotropy) increases in parallel with the film surface.
In the thin ferromagnetic layer formed on the side wall surface of the groove provided on the substrate surface like the ferromagnetic layer in the magnetic recording medium of the present invention, the magnetic anisotropy becomes extremely strong in the direction perpendicular to the substrate surface. Therefore, according to the magnetic recording medium of the present invention, the magnetic flux of the recorded portion tends to emerge on the surface of the magnetic recording medium, and there is no disadvantage that the magnetic flux is weak as in the conventional perpendicular magnetic recording medium, and high-density recording can be performed. Can be.

Further, according to the magnetic recording medium of the present invention,
Even if the magnetic head is slightly away from the surface of the magnetic recording medium,
Reproduction can be performed, and the surface of the magnetic recording medium can be prevented from being scraped. Also, even if the magnetic recording medium surface is worn by repeatedly performing recording and reproduction while the magnetic head is in close contact with the surface of the magnetic recording medium, the ferromagnetic layer is formed deeply perpendicular to the substrate surface. And recording and reproduction with high density and sharpness can be repeatedly performed over a long period of time.

In the magnetic recording medium shown in FIG. 1, when a substrate transparent to visible light is used as the substrate 1, it can be used as a polarizer.

FIG. 2 is an enlarged sectional view schematically showing a typical example of the magnetic recording medium of the present invention which also has a function as a display. In FIG. 2, a magnetic recording medium has a substrate 1A transparent to visible light, a large number of linear grooves formed on one surface of the substrate and having side walls 2 perpendicular to the substrate surface and having mutually parallel side walls. 3 and a ferromagnetic layer 4A having a height H formed on the side wall surface of the groove of 0.1 μm to 5 μm and a thickness M of 5 nm to 200 nm, wherein the ferromagnetic layer 4A extends in a direction perpendicular to the groove. The distance L1 between the ferromagnetic layers formed on the side wall surface 2 of the groove 3 and the substrate portion between the grooves are formed at equal intervals in the range of 0.2 μm to 2.0 μm. The ferromagnetic layer 4A is formed so that the width L2 is equal, and L1 and L2 are in the range of 0.2 μm to 2.0 μm. The light reflection film 6 is provided on the surface of the substrate 1A on which the ferromagnetic layer 4A is formed, and the antireflection film 7 is provided on the surface opposite to the surface on which the light reflection film 6 is provided. I have. The light reflection film 6 can be formed by bonding the light reflection film 6 formed on another substrate 1B to the surface of the substrate 1A on which the ferromagnetic layer 4A is formed.

As the substrate 1A transparent to visible light,
MMA resin, PMMA resin, polycarbonate resin, polypropylene resin, acrylic resin, styrene resin,
ABS resin, polyarylate, polystyrene, polysulfone, polyethersulfone, epoxy resin, poly-4-methylpentene-1, fluorinated polyimide resin,
Fluorine resin, phenoxy resin, polyolefin resin,
Organic transparent materials such as transparent plastics such as diethylene glycol bisallyl carbonate, nylon resin, and fluorene-based polymer, and inorganic transparent materials such as glass, quartz, and alumina are used. The thickness of the substrate 1A is 50 to
500 μm is appropriate, and the thinner the thickness, the closer the distance between the ferromagnetic layer 4A and the magnetic head is. If it is thicker than 500 μm, it is possible to record with a magnetic head from the light reflection film 6 side.

The material of the ferromagnetic layer 4A has a large magneto-optical effect, has magnetic anisotropy in the film plane, and has a coercive force of 3
Suitable for 00-2000 Oersted and magnetic recording,
In order to provide the magnetic recording medium with a function as a polarizer, it is preferable to use a conductive material, a semiconductor material, a metal material, or the like that allows electrons to move through the ferromagnetic layer by an electric field of light.

As a ferromagnetic layer made of such a material, Fe having an average particle diameter of 2 nm to 50 nm,
Layers containing ultrafine particles of an alloy of Co, Ni or any combination thereof are particularly preferred.

An alloy made of Fe, Co, Ni or any combination thereof has the largest Faraday rotation angle and is a good conductor because it is a metal, and these metals or alloys make it finer. By setting the average particle diameter (preferably, 2 nm to 50 nm), it is possible to impart magnetic anisotropy in the film surface of the ferromagnetic layer and increase the coercive force. This means that the coercive force can be arbitrarily changed by controlling the particle size of Fe, Co, Ni or an alloy thereof. That is, by using ultra-fine particles of Fe, Co, Ni or their alloys and controlling the particle size, information can be easily recorded and erased, and an image having high contrast when applied to a display or the like can be obtained. A displayable magnetic recording medium can be obtained.

The ferromagnetic layer containing ultrafine particles of an alloy of Fe, Co, Ni or any combination thereof can be formed by a vapor deposition method in a gas. It is preferable to introduce (several hundred mtorr) air.

As a ferromagnetic material, an insulator such as an oxide (eg, Fe ₂ O ₃ , CoFe ₂ O ₄ , Bi ₂ DyFe _3.8 A
l _1.2 O ₁₂ ), a nonmagnetic semiconductor layer or a nonmagnetic metal layer is provided on the oxide ferromagnetic layer so as to be in contact with the oxide ferromagnetic layer to form an electron transfer layer. is necessary. When the thickness of the electron transfer layer is large, light absorption is increased. Note that if a ferromagnetic layer having conductivity is used, such as an alloy of Fe, Co, Ni, or any combination thereof,
The ferromagnetic layer and the electron transfer layer can be used together, which is more preferable.

FIG. 3 is an enlarged sectional view schematically showing an example of a magnetic recording medium having a ferromagnetic layer provided with a nonmagnetic semiconductor layer or a nonmagnetic metal layer. In order to provide the non-magnetic semiconductor layer or the non-magnetic metal layer 8 in contact with the oxide ferromagnetic layer 4B, the oxide ferromagnetic layer 4B formed on the side wall surface of the groove as shown in FIG. Even if a non-magnetic semiconductor layer or a non-magnetic metal layer 8 is provided thereon, an oxide ferromagnetic layer may be formed on the non-magnetic semiconductor layer or the non-magnetic metal layer 8 formed on the side wall surface of the groove as shown in FIG. A body layer 4B may be provided.

In the magnetic recording medium applied as a display, the groove 3 must be a space or be filled with a material that is transparent to visible light and has a different refractive index from the substrate.

The light reflection film 6 is made of a material having a high reflectance at a specific visible light wavelength, such as Cu, Al, Ag, Au,
Pt, Rh, TeOx, TeC, SeAs, TeAs,
It can be formed by a vacuum evaporation method, a sputtering method, an ion plating method, or the like using TiN, TaN, CrN, or the like. The thickness is preferably 50 to 500 nm. In addition, alternating multilayer films of SiO ₂ , TiO _2, etc., alternating multilayer films of metal and dielectric, inclined reflectors, hologram reflectors (“Holo Bright” manufactured by Nippon Polaroid Co., Ltd.)
Etc. can also be used.

Further, in particular, when the magnetic recording medium is used for recording and reproduction by a laser beam or used as a display, the transmittance of light is improved, and the magnetic recording medium is subjected to chemical corrosion and chemical change due to light. To protect,
It is desirable to provide an anti-reflection film on the surface opposite to the surface on which the light reflection film is provided. The antireflection film is shown in Table 1 below.
It can be formed by a vacuum deposition method or the like using the materials described above.

[0059]

[Table 1]

FIG. 4 is an explanatory view schematically showing how contrast is exhibited when the magnetic recording medium of the present invention is used as a display. The magnetic recording medium shown in FIG. 4 includes a substrate 1A that is transparent to visible light, a magnetized portion 4X and a non-magnetized portion 4Y of a ferromagnetic layer formed on the side wall surface of a groove provided on one surface of the substrate. The light reflection film 6 is provided on the other surface of the substrate.

The light 11A is circularly polarized light, and the light 11B that has passed through the portion of the ferromagnetic layer having the magnetized portion 4X (the ferromagnetic layer, its surrounding substrate and space, etc.) has its polarization plane rotated. Linearly polarized light. The light 11B is reflected by the light reflection layer 6, and the reflected light 11C again passes through the portion of the ferromagnetic layer having the magnetized portion 4X. Here, since the polarization plane of the light 11C is rotated, the light 11C cannot pass through a portion of the ferromagnetic layer having the magnetized portion 4X (which serves as an analyzer).

On the other hand, the light 12A is also circularly polarized light, and the light 12A that has passed through the portion of the ferromagnetic layer having the non-magnetized portion 4Y.
B is linearly polarized light, but the light 12 reflected by the light reflecting layer 6
In C, the polarization plane is not rotated. The linearly polarized light can pass through the portion of the ferromagnetic layer having the non-magnetized portion 4Y because the polarization plane is matched. The degree of light passage depends on the degree of magnetization of the ferromagnetic layer.

Thus, the magnetized portion of the ferromagnetic layer looks dark, and the non-magnetized portion looks bright. A magnetic recording medium having this phenomenon can also serve as a polarizer, and can form a desired magnetized portion and irradiate it with light to form various visible images, which can be changed and erased. It can be applied to displays that do not require lights.

It is to be noted that a commercially available polarizer may be fitted to the surface of the substrate opposite to the surface on which the light reflecting film 6 is provided, or a ferromagnetic material may be formed on the side wall surface of the groove without providing the light reflecting film 6. A display can also be obtained by sandwiching the substrate 1A having a layer between a pair of polarizers.

The magnetic recording medium of the present invention can be manufactured by the following steps. That is, (1) a step of forming a large number of rows of concave grooves so as to be linear and parallel to each other by photolithography on the surface of the substrate, and (2) forming a plurality of concave grooves on the substrate on which the grooves are formed. Forming a ferromagnetic thin film (ferromagnetic layer); (3) only the portion of the formed ferromagnetic thin film (ferromagnetic layer) formed on the surface of the side wall of the concave groove (4) a step of performing an etching treatment so as to remain, and a film of an inorganic material is formed on the substrate by sputtering or the like so that the concave groove is filled as necessary after the step of (3), and the surface of the substrate is formed. A step of polishing to make it smooth, (5) a step of forming a light-reflecting film on one surface of the substrate of the magnetic recording medium as required after the step of (3) or (4), or Laminates the formed light reflection layer to the substrate of the magnetic recording medium Step, can be manufactured.

FIG. 5 is an explanatory view showing an example of a process for manufacturing the magnetic recording medium of the present invention. First, a resist film 9 is laminated on the substrate 1 (a), a photomask having a large number of linear thin line patterns parallel to each other is arranged on the resist film 9 and exposed to UV light, and then wet etching is performed. To form a resist film 9 having a constant equal width m ₁ and an interval m ₂
(B), the substrate 1 is etched to a specific depth to form a groove 3 (c), and then the resist film 9 is stripped (d). In this way, the groove 3 can be formed relatively easily and vertically (up to about 10 μm) perpendicular to the processing surface. In addition, if a lithography method is used, a fine linear groove having clean linearity can be formed.

When a plastic plate is used as the substrate, for example, an SiO ₂ thin film may be formed on the plastic plate by a PVD method, and a groove may be formed on the surface of the SiO ₂ thin film.

Next, a thin film (ferromagnetic layer) 4 made of a ferromagnetic material is formed on the substrate on which the groove is formed (e). As a method for forming the thin film (ferromagnetic layer), a PVD method, a CVD method, or a plating method is suitably adopted, but the production method is not particularly limited.

Next, the formed thin film (ferromagnetic layer) 4
(F) by removing the portion parallel to the substrate surface by etching with Ar ions 10 (whether wet or dry, but preferably applying a reverse bias voltage to the substrate side and performing reverse sputtering). A thin film (ferromagnetic layer) 4 can be formed on the side wall surface of the groove (g). Next, a light reflection layer is formed on one surface of another substrate 1B, and the light reflection layer side of the substrate with the light reflection layer and the ferromagnetic thin film (ferromagnetic layer) of the substrate 1
The magnetic recording medium of the present invention can be obtained by laminating the surface on which the surface 4 is formed (h). Further, by using a plastic film as a substrate, a deformable magnetic recording medium can be obtained.

[0070]

Next, the present invention will be described more specifically with reference to examples.

Example 1 Two layers of a Cr ₂ O ₃ film and then a Cr film were provided on a surface of a glass substrate having a thickness of 1 mm so as to have a total thickness of 120 nm, and a positive resist film was further provided thereon. A photomask having a large number of linear thin line patterns parallel to each other is arranged on this resist film, and a large number of photomasks are formed on the resist film using UV light so that L1 = L2 = 0.5 μm in FIG. A linear thin line pattern is exposed, the resist film is etched using a wet etching method, and the glass substrate surface is further etched using a fluorine-based gas to a depth of 0.4 μm (H = 0 in FIG. 1). .4μ
m) was formed. Next, the two layers of the Cr ₂ O ₃ film and the Cr film and the resist layer were peeled off.

Next, iron was vapor-deposited on the processing surface of the glass substrate by using an in-gas vapor deposition method without heating the substrate to form an iron ultrafine particle film (ferromagnetic layer). The gas used is a mixed gas of Ar and air, Ar gas is 50 CCM,
Dry air is flowed at a flow rate of 2 CCM and the total pressure is 1.3 Pa
And The average thickness of the iron ultrafine particle film (ferromagnetic layer) thus formed was 81 nm.

When the cross section of the ultrafine iron particle film (ferromagnetic layer) was observed with a transmission electron microscope (TEM), the average particle diameter of the ultrafine iron particles was 6 nm, and each fine particle was separated by a nonmagnetic phase. . The composition of the iron ultrafine particle film measured by X-ray photoelectron spectroscopy (XPS) is 53% iron, and the others are O, C, N
Met. The coercive force measured on the flat portion (the ultrafine iron film formed on the glass plate placed on the same plane as the processing surface of the glass substrate at the time of forming the ultrafine iron film) is 450 Oersted, and the in-plane direction Had a squareness ratio of 0.80 and a large in-plane magnetic anisotropy.

Next, dry etching using an Ar gas is performed, and a portion parallel to the substrate surface (plane 2a in FIG. 1,
The iron ultrafine particle film (ferromagnetic layer) on the side 2b) was removed, and the iron ultrafine particle film (ferromagnetic layer) was left only on the side wall surface (side wall surface 2 in FIG. 1) of the groove. For dry etching, the Ar gas flow rate was 6 CCM, the degree of vacuum was 1.5 Pa, and the input power was 450.
W, applied voltage -500V for 25 minutes.

Then, using a sputtering apparatus, the target was SiO ₂ , and an Ar gas and an O ₂ gas were introduced, whereby the glass substrate surface (the 2a surface, 2b surface and the ferromagnetic layer in FIG. 1) was formed. After the side wall surface 2) is covered with the SiO ₂ film to fill the groove, the surface of the SiO ₂ film is polished so as to be smooth by using both chemical polishing and mechanical polishing to obtain a magnetic recording medium. Was.

A magnetic recording apparatus equipped with a commercially available narrow gear coupling magnetic head was manufactured. Using the magnetic recording medium obtained as described above, each ferromagnetic layer as shown in FIG. Magnetic recording (upward or downward magnetization perpendicular to the substrate surface) was performed. Further, for the magnetic recording medium after recording, a clear reproduction signal can be obtained by determining the position of the magnetic head so that the signal intensity due to the magnetization from the ferromagnetic layer is maximized in the magnetic recording device. did it. Also, the surface of the magnetic recording medium is
The reproduction output hardly changed even after polishing to a certain degree.

Comparative Example 1 A ZnO film having a thickness of 100 nm was formed on a quartz substrate having a smooth surface using a sputtering apparatus. Then, a Ba ferrite (BaCo _0.5
A substrate was heated to 650 ° C. to form a perpendicular magnetic film (Ti _0.5 Fe ₁₁ O ₁₉ ) (perpendicular magnetic anisotropy magnetic field Hk = 4.5 KOe) with a thickness of 300 nm to obtain a magnetic recording medium.
When recording and reproduction were performed on this magnetic recording medium using the magnetic recording apparatus in Example 1, when the recording unit was reduced to 81 nm, the reproduction output was 3 in Example 1.
This was one-half, and almost no reproduction was possible after polishing the surface of the magnetic recording medium by about 400 °.

Example 2 Using a glass substrate having a groove having a depth of 0.4 μm (H = 0.4 μm in FIG. 1) produced in Example 1, a surface replica of the glass substrate was formed on a 50 μm-thick polycarbonate film. By taking L1 = L2 = 0.5 μm in FIG.
Periodic irregularities of m and H = 0.4 μm were formed. A magnetic recording medium was obtained in the same manner as in Example 1 except that this was used in place of the glass substrate produced in Example 1. When this magnetic recording medium was recorded and reproduced by using the magnetic recording apparatus in Example 1, a clear reproduced signal was obtained. Also, the surface of the magnetic recording medium is
The reproduction output hardly changed even after polishing for about Å.

Comparative Example 2 Comparative Example 1 using the polycarbonate film of Example 2
Tried to make a magnetic recording medium with a perpendicular magnetization film of
Since the polycarbonate film could not be heated at 650 ° C., Ba ferrite did not crystallize and a magnetic recording medium could not be produced.

Example 3 A magnetic field (0.5 KG) was applied to the magnetic recording medium manufactured in Example 1 in the direction perpendicular to the substrate surface, and He with a wavelength of 633 nm was used.
Each of the ferromagnetic layers in FIG. 1 was heated by perpendicularly incident -Ne laser light on the substrate surface to perform digital magnetic recording (upward or downward magnetization perpendicular to the substrate surface) with a width of 1 μm. When this magnetic recording medium was reproduced in the same manner as in Example 1 using the magnetic recording device in Example 1, a clear reproduced signal was obtained. Also,
Even after polishing the surface of the magnetic recording medium by about 400 °, the reproduction output hardly changed.

COMPARATIVE EXAMPLE 3 Using the magnetic recording medium of Comparative Example 1, a magnetic field (0.5 KG) was applied in the direction perpendicular to the substrate surface, and He-
When Ne magnetic laser light was applied to heat the Ba ferrite perpendicular magnetization film to perform digital magnetic recording (upward or downward magnetization perpendicular to the substrate surface) with a width of 1 μm, the Ba ferrite had too good transparency and the laser was Since the absorption of light is small and the thermal sensitivity decreases, and the diffusion of heat to the film surface is large,
Could not record.

Example 4 A magnetic field (0.5 KG) was applied to the magnetic recording medium manufactured in Example 1 in a direction perpendicular to the substrate surface, and He having a wavelength of 633 nm was used.
Each of the ferromagnetic layers in FIG. 1 was heated by perpendicularly incident -Ne laser light on the substrate surface to perform digital magnetic recording (upward or downward magnetization perpendicular to the substrate surface) with a width of 1 μm. The magnetic recording medium is irradiated with He-Ne laser light having a wavelength of 633 nm to pass through the ferromagnetic layer, and the direction of rotation of the polarization plane of the laser light (the rotation angle in the magnetized portion was 3.6 degrees) is analyzed by an analyzer. When the reproduction was performed by the magneto-optical head detected in step (1), high-density recording reproduction was possible.

Example 5 A magnetic recording medium was manufactured in the same manner as in Example 1 except that a cobalt ultrafine particle film (ferromagnetic layer) was formed using cobalt ultrafine particles instead of iron ultrafine particles. . The average particle diameter of the ultrafine cobalt particles in the ultrafine cobalt particle film was 75 °, and the cobalt content was 78%. When recording and reproduction were performed on this magnetic recording medium in the same manner as in Example 4, the rotation angle was 2.0 degrees, and high-density recording and reproduction were possible.

Comparative Example 4 A glass substrate having a smooth surface was used, and a continuous cobalt film was formed by a vacuum deposition method (degree of vacuum: 2 × 10
^-4 Pa) to provide a magnetic recording medium on the surface of the glass substrate. When this magnetic recording medium was recorded with laser light in the same manner as in Example 4, the rotation angle was 0.5 degrees, and recording and reproduction could not be performed.

Example 6 One surface of a 500 μm thick quartz substrate was
m, two layers of a Cr ₂ O ₃ film and a Cr film are provided.
Further, a positive resist film was provided thereon. A photomask having a large number of linear thin line patterns parallel to each other is arranged on this resist film, and a large number of linear masks are formed on the resist film using UV light so that L1 = L2 = 1 μm in FIG. Exposing the fine line pattern, then etching the resist film using a wet etching method,
Further, the quartz surface is etched using a fluorine-based gas,
A groove having a depth of 0.4 μm (H = 0.4 μm in FIG. 2) was formed. Next, the two layers of the Cr ₂ O ₃ film and the Cr film and the resist film were peeled off.

Next, a vapor deposition method in gas (a gas is a mixed gas of Ar and air, air / Ar = 200 mtorr / 50 mt)
orr), iron was deposited on the processed surface of the quartz substrate without heating the substrate. The film thus formed contained ultrafine iron particles having an average particle size of 55 °, iron oxide and carbide, and had an average thickness of 76 nm. The coercive force of this iron ultrafine particle film measured at a flat portion (iron ultrafine particle film formed on a glass plate placed on the same plane as the quartz substrate surface at the time of forming the iron ultrafine particle film) is 630 Oersted,
The film had in-plane magnetic anisotropy.

Next, −40 was applied to the substrate side using a sputtering apparatus.
A portion parallel to the substrate surface by reverse sputtering by applying 0 V and introducing Ar gas (planes 2a and 2b in FIG. 2)
The ultrafine iron film (ferromagnetic layer) was removed, and the ultrafine iron film (ferromagnetic layer) was left only on the side wall surface (side wall surface 2 in FIG. 2) of the groove. A layer of MgF ₂ (n = 1.38) was provided as an anti-reflection film on the surface of the quartz substrate opposite to the surface having the grooves so as to have a thickness of 100 nm by a vacuum evaporation method. With this antireflection film, the reflectance in the visible light range is 3
%.

The case where the direction of the electric vector is perpendicular to the thin lines of the ferromagnetic layers which are linear and parallel to each other is S-polarized light,
Assuming that the parallel case is P-polarized light, the S-polarized light transmittance (T ₁ ) of the magnetic recording medium manufactured as described above has a wavelength of 550 n.
m was 60% or more, and the P-polarized light transmittance (T ₂ ) was 2% or less at a wavelength of 550 nm. The degree of polarization [(T ₁ −T ₂ ) / (T ₁ + T ₂ )] was 80% or more at a wavelength of 550 nm. This value confirms that the obtained magnetic recording medium is also useful as a polarizer.

A magnetized portion was formed by drawing a character from a surface having the antireflection film of the magnetic recording medium with a cylindrical bar magnet having a diameter of 1 mm. When the magnetic recording medium was sandwiched between a pair of film polarizers and visualization was attempted, the magnetized portion appeared black because Faraday-rotated linearly polarized light could not pass through the film polarizer, while the non-magnetized portion was rotated by the polarization plane. Because of the absence of text, I could read characters that looked bright and had a clear contrast.

Further, another quartz substrate (thickness: 1 mm) was
A film (thickness: 200 nm) is provided by a vacuum evaporation method, and the Al film side of the pair of film polarizing plates having the groove of the quartz substrate is replaced with the surface having the groove of the quartz substrate. By providing a light reflecting film in the same manner as above and drawing characters with a bar magnet in the same manner as described above, it was possible to read characters with good contrast.

Example 7 Instead of the vapor deposition method in Example 6, the target was changed to Bi ₂ Gd ₁ Fe ₄ Al ₁ O ₁₂ by sputtering, and the substrate temperature was set to 300 ° C. Similarly, an oxide magnetic material film (ferromagnetic material layer) was provided on the side wall of the groove so as to have a thickness of 57 nm. After heating at 650 ° C. for 3 hours, the coercive force measured at the flat portion was 540 Oe. Then, a Ge layer is formed by sputtering with a thickness of 80 ° without heating the substrate (sputtering pressure: 6.7 × 10 ^−3).
(torr, input power: 200 W), and a magnetic recording medium was manufactured by the reverse sputtering method in the same manner as in Example 6, leaving the Ge layer only on the oxide magnetic film on the wall surface. By using this magnetic recording medium in the same manner as in Example 6 and drawing characters with a bar magnet, characters with good contrast could be read. When the Ge layer was not provided, characters could not be read.

Comparative Example 5 A magnetic recording medium was manufactured by depositing an ultrafine iron film to a thickness of 67 nm on a quartz substrate having a smooth surface in the same manner as in the vapor deposition method in Example 6. Example 6 Using a Magnetic Recording Medium in Example 6
When a bar magnet image was drawn in the same manner as described above, the visible light transmittance of this ultrafine iron particle film was 40% or less, and it was a black film by visual observation, and the image could not be seen.

Comparative Example 6 In the same manner as in the sputtering method in Example 7, a 100-nm thick oxide magnetic film was formed on a 1 mm-thick quartz substrate having a smooth surface.
m and a thickness of 900 nm to produce a magnetic recording medium. In both magnetic recording media, the oxide magnetic film was a yellow film, and a transmittance of about 80% was obtained with red light.
Light having a short wavelength of 0 nm or less had a transmittance of 30% or less. After magnetizing with a bar magnet in the same manner as in Example 7, visualization was attempted between two commercially available film polarizing plates. When the thickness of the oxide magnetic film was 100 nm, an image was not visible, and at 900 nm, an image could be observed. However, since the light transmittance was low, in the case of a reflection type (a light reflection film was provided on one surface of the magnetic recording medium). Was not observed.

[0094]

According to the first aspect of the present invention, since the ferromagnetic layer is provided as an ultra-thin film perpendicular to the substrate surface, there is no blurring (bleeding) of recording in a direction parallel to the substrate surface and high density. And sharp recording can be performed. Further, even if the surface of the magnetic recording medium is worn due to repeated recording and reproduction, since the ferromagnetic layer is formed deeply perpendicular to the substrate surface, there is little influence on the reproduction output, and the recording and reproduction are performed for a long period of time. Can be repeated. Further, since the ferromagnetic layer is provided perpendicular to the substrate surface, the ferromagnetic layer only needs to have in-plane magnetic anisotropy, and the material used for the ferromagnetic layer is less restricted. It is easy to manufacture.

According to the second aspect of the present invention, even when recording and reproduction are repeatedly performed, the wear on the surface of the magnetic recording medium is small, and recording and reproduction can be repeatedly performed for a long period of time. According to the third or fourth aspect of the present invention, recording and reproduction with a laser beam can be performed. According to the fifth aspect of the present invention, since the ferromagnetic layer is made of Fe, Co, Ni or an ultra-fine particle of an alloy made of any combination thereof having a particle diameter of 500 ° or less, it is possible to obtain a new light such as a quantum size effect. Interaction appears, a large magneto-optical effect is obtained, and high-density recording with a large S / N can be easily obtained.

According to the sixth aspect of the present invention, high-density and sharp recording can be performed without blurring (bleeding) of recording in a direction parallel to the substrate surface. According to the invention of claim 7, by recording information by magnetizing a ferromagnetic layer provided as an ultrathin film perpendicular to the substrate surface in a direction perpendicular to the substrate surface, it is possible to miniaturize the magnetized portion, High-density and sharp recording can be performed. Further, non-contact recording by laser light can be performed. According to the invention of claim 8,
By recording information by magnetizing the ferromagnetic layer that is discontinuous in the recording direction and perpendicular to the substrate surface as one bit in the recording direction and perpendicularly to the substrate surface to record information, the magnetized portion of the ferromagnetic layer is discontinuous. Since it can be limited to one by one, the magnetized portion can be miniaturized, and high-density and sharp recording can be performed.

According to the ninth aspect of the present invention, the ferromagnetic layer having a thickness of 5 nm to 200 nm formed on the side wall surface of the groove is magnetized in a direction perpendicular to the substrate surface to record information. Due to the large magneto-optical effect due to the interaction between the body layer and the reproduction laser beam, a reproduction signal with a good S / N can be obtained. Further, non-contact reproduction by laser light can be performed. According to the tenth aspect of the present invention, since the ferromagnetic layers are arranged on the substrate transparent to visible light in a direction perpendicular to the surface of the substrate, high light transmittance and a polarization function can be obtained at the same time. Thus, a high contrast can be formed in the non-magnetized portion, an image or the like can be recorded in a large area, and the image or the like can be observed as a display.

According to the eleventh or twelfth aspect of the present invention, high contrast can be obtained by providing the light reflecting film,
It can be used as a reflective display. According to the thirteenth aspect, by providing the antireflection film, the light transmittance is improved, and an image or the like with higher contrast can be observed. According to the fourteenth aspect, since the ferromagnetic layer having conductivity is used, the ferromagnetic layer can be used as a ferromagnetic layer and / or a polarizer layer. According to the invention of claim 15, since the ferromagnetic layer contains ultrafine particles of Fe, Co, Ni, or an alloy of any combination thereof having a large Faraday effect, the ferromagnetic layer has a polarization function in combination with the large Faraday effect. ,
Further, an image or the like with high contrast can be observed.

According to the sixteenth aspect of the present invention, when the ferromagnetic layer is insulative, the non-magnetic semiconductor layer or the non-magnetic metal layer is provided in an overlapping manner, so that a polarizing function is imparted and an image with a high contrast or the like is provided. Can be observed. According to the seventeenth aspect, since the substrate is a plastic film, a deformable magnetic recording medium can be obtained.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view schematically showing one example of a magnetic recording medium of the present invention.

FIG. 2 is an enlarged sectional view schematically showing a typical example of a magnetic recording medium of the present invention which also has a function as a display.

FIG. 3 is an enlarged sectional view schematically showing an example of a magnetic recording medium of the present invention having a ferromagnetic layer provided with a nonmagnetic semiconductor layer or a nonmagnetic metal layer.

FIG. 4 is an explanatory diagram schematically showing how contrast is exhibited when the magnetic recording medium of the present invention is used as a display.

FIG. 5 is an explanatory view showing an example of a process for manufacturing the magnetic recording medium of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Substrate 1A Substrate transparent to visible light 2 Side wall surface of groove 3 Many linear grooves with parallel side walls 4 Ferromagnetic layer 4A Ferromagnetic layer 4B Oxide ferromagnetic layer 4X Ferromagnetic material Magnetized portion of layer 4Y Non-magnetized portion of ferromagnetic layer 5 Magnetic recording medium surface 6 Light reflection film 7 Antireflection film 8 Nonmagnetic semiconductor layer or nonmagnetic metal layer 9 Resist film 10 Ar ion 11A Circularly polarized light 11B Ferromagnetic layer 11C Light reflected by the light reflecting layer 12A Circular polarized light 12B Light reflected through the non-magnetized portion of the ferromagnetic layer 12C Light reflected by the light reflecting layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01F 1/047 H01F 10/16 10/16 1/06 J

Claims (17)

[Claims] 1. A substrate, a plurality of grooves formed on the surface of the substrate and having a side wall surface perpendicular to the substrate surface, the side wall surfaces being parallel to each other, and a height of 0.1 μm formed on the side wall surface of the groove. And a ferromagnetic layer having a thickness of 5 to 200 μm, and the ferromagnetic layers are formed at equal intervals in a range of 0.2 to 2.0 μm across the groove. Magnetic recording medium. 2. The magnetic recording medium according to claim 1, wherein the inside of the groove is filled with an inorganic or organic material, and the surface of the magnetic recording medium is a smooth surface. 3. The magnetic recording medium according to claim 1, wherein the substrate is transparent to a laser beam. 4. The magnetic recording medium according to claim 2, wherein the inorganic or organic material is transparent to laser light. 5. The ferromagnetic material layer has an average particle diameter of 2 nm of an alloy of Fe, Co, Ni or any combination thereof.
The magnetic recording medium according to any one of claims 1 to 4, wherein the magnetic recording medium contains ultrafine particles of from 50 to 50 nm. 6. The magnetic recording medium according to claim 1, wherein a number of grooves having parallel side wall surfaces are linear grooves. 7. A recording method of a magnetic recording medium for recording information by applying a bias magnetic field to a magnetic recording medium and irradiating the magnetic recording medium with a laser light, wherein the substrate is transparent to the laser light.
A number of grooves formed on the surface of the substrate and having a side wall surface perpendicular to the substrate surface and having parallel side wall surfaces; and a height of 0.1 μm to 5 μm and a thickness of 5 nm to 5 nm formed on the side wall surface of the groove. A ferromagnetic layer of a magnetic recording medium is formed of a 200 nm ferromagnetic layer, and the ferromagnetic layers are formed at regular intervals in a range of 0.2 μm to 2.0 μm in a direction crossing the groove. A method for recording information on a magnetic recording medium, wherein information is recorded by magnetizing in a perpendicular direction to the information. 8. A ferromagnetic recording medium having a ferromagnetic layer in which a large number of grooves whose side walls are parallel to each other are linear grooves and has a ferromagnetic layer discontinuous in the recording direction and perpendicular to the substrate surface. 8. The recording method for a magnetic recording medium according to claim 7, wherein information is recorded by magnetizing the body layer as one bit in a recording direction in a direction perpendicular to the substrate surface. 9. A method for reproducing information recorded on a magnetic recording medium by using a rotation of a plane of polarization of a laser beam applied to the magnetic recording medium, the method comprising: A plurality of grooves having side walls perpendicular to the surface of the substrate and parallel to each other, and a height of 0.1 μm to 5 μm and a thickness of 5 n formed on the side walls of the grooves.
a ferromagnetic layer of a magnetic recording medium formed of ferromagnetic layers having a thickness of 0.2 to 2.0 μm in a direction crossing the groove. A method for reproducing a magnetic recording medium, wherein information is recorded by being magnetized in a direction perpendicular to a substrate surface. 10. A substrate transparent to visible light, a plurality of linear grooves formed on one surface of the substrate and having a side wall surface perpendicular to the substrate surface, the side wall surfaces being parallel to each other; The ferromagnetic layer has a height of 0.1 μm to 5 μm and a thickness of 5 nm to 200 nm formed on the side wall surface of the groove, and the ferromagnetic layer has a thickness of 0.2 μm to 2.0 μm across the groove. A magnetic recording medium formed so as to have an interval. 11. The magnetic recording medium according to claim 10, wherein a light reflecting film is formed on the grooved surface of the substrate. 12. The magnetic recording medium according to claim 10, wherein a light reflection film is formed on a surface of the substrate opposite to the surface having the grooves. 13. The magnetic recording medium according to claim 11, wherein an anti-reflection film is provided on a surface opposite to the surface on which the light reflection film is provided. 14. The magnetic recording medium according to claim 10, wherein the ferromagnetic material has conductivity. 15. The ferromagnetic material layer has an average particle size of 2n of an alloy of Fe, Co, Ni or any combination thereof.
15. The magnetic recording medium according to claim 10, comprising ultrafine particles of m to 50 nm. 16. A ferromagnetic layer having the same height and a thickness of 5
16. The magnetic recording medium according to claim 10, wherein a nonmagnetic semiconductor layer or a nonmagnetic metal layer having a thickness of 10 nm to 10 nm is provided. 17. The magnetic recording medium according to claim 1, wherein the substrate is a plastic film.