JPH087361A - Magneto-optical recording medium, its manufacturing method and apparatus - Google Patents

Abstract

PURPOSE:To form magnetic domains whose sizes are smaller than a light spot diameter and facilitate high density recording by a method wherein regions whose magnetic characteristics, thermal characteristics and/or optical characteristics are different from those of the other regions are provided in the magnetic film of a magneto-optical recording medium. CONSTITUTION:At least a magnetic film 2 is provided on the disc-type substrate 1 of a magneto-optical recording medium. Regions 3 whose coercive forces are low are provided on the magnetic film 2. The regions 3 may be formed on the disc in various patterns. If they are formed in spiral patterns, they can be also used as tracks and accessed easily. At that time, the width of each region 3 is 0.4mum and the distance between the regions 3 is 0.3mum. The region whose coercive force is low has a higher sensitivity than the other region. Therefore, if a light beam having a proper intensity is applied to elevate a medium temperature, recording magnetic domains can be formed in the regions 3 only in the medium. With this constitution, the width of each magnetic domain is limited to the width (0.4mum) of each region 3 regardless of the wavelength of a laser beam, so that high density recording can be realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high density magneto-optical recording medium capable of stably forming a magnetic domain smaller than a light spot, a method of manufacturing the same, and an apparatus using the same.

[0002]

2. Description of the Related Art The cross-sectional structure of a conventional magneto-optical recording medium is, for example, the structure shown in FIG. On a transparent substrate 1 such as glass provided with a guide groove for tracking, a dielectric layer 31 of silicon nitride or the like is about 90 nm, a magnetic layer 32 of TbFeCo or the like is about 100 nm, and a protective layer 33 of silicon nitride or the like.
To form a recording film 4. The dielectric layer 31 has a function of multiply reflecting the laser light incident from the substrate 1 side therein, and increasing the rotation (Kerr rotation) of the polarization plane generated in the magnetic layer 32. The protective layer 33 is the magnetic layer 3
It has a function of protecting 2 from corrosion such as oxidation.

The principle of recording / reproducing on such a recording medium will be described. The coercive force of the magnetic layer 32 is large at room temperature and small near the Curie temperature. Therefore, when a recording magnetic field is applied to the recording medium and the laser light is converged and irradiated to raise the temperature of the recording medium, the coercive force Hc becomes equal to the recording magnetic field when the recording temperature is reached, so that the recording temperature is reached. The magnetization of the magnetic layer 32 in this portion is oriented in the direction of the recording magnetic field to form a recording magnetic domain. At the time of reproduction, the recording magnetic domain is irradiated with convergent light, and the rotation of the plane of polarization of the reflected light is detected to detect the presence, shape, and size of the recording magnetic domain.

This method is described, for example, in JP-A-59-
It is described in Japanese Patent Publication No. 210543.

[0005]

However, when attempting to record a small magnetic domain by controlling the light intensity in the conventional example, it is difficult to control the size of the portion reaching the recording temperature, and it is substantially Had a problem that it was not possible to record magnetic domains smaller than 1/2 of the light spot diameter. Therefore, it is difficult to perform high density recording.

A first object of the present invention is to set the light spot diameter to 1
Another object of the present invention is to provide a magneto-optical recording medium capable of performing high density recording by forming magnetic domains smaller than / 2.

The second object of the present invention is to reduce the light spot diameter to 1 /
Another object of the present invention is to provide a method of manufacturing a magneto-optical recording medium capable of forming magnetic domains smaller than 2 and performing high density recording.

A third object of the present invention is to set the light spot diameter to 1
It is an object of the present invention to provide a magneto-optical recording device capable of performing high density recording by forming magnetic domains smaller than / 2.

[0009]

The present invention uses the following means in order to solve the first object.

(1) In a magneto-optical recording medium composed of at least one magnetic film, when the temperature is gradually raised while applying a constant magnetic field to the magneto-optical recording medium, only a part of the magnetic film is inverted. A magneto-optical recording medium characterized in that there is a temperature such that a magnetic domain is formed and no other region is formed.

(2) In a magneto-optical recording medium including at least one magnetic film, when the magnetic field applied to the magneto-optical recording medium at a constant temperature is gradually increased, the reversed magnetic domain is formed only in a part of the magnetic film. A magneto-optical recording medium characterized by the presence of a magnetic field that can be generated and cannot be generated in other areas.

(3) A magneto-optical recording medium comprising at least one magnetic film, wherein a part of the magnetic film having high recording sensitivity is present.

(4) A magneto-optical recording medium comprising at least one magnetic film, wherein a part of the region having a low coercive force is present in the magnetic film.

(5) A magneto-optical recording medium characterized in that at least one of the width and the length of the partial area is smaller than the width or the length of the information recording unit.

As a result, among the temperature rising parts,
It becomes easy to form a minute recording magnetic domain only in a region where at least one of magnetic property, thermal property and optical property is different from other parts. That is, high density recording becomes possible.

Further, it becomes easy to record by controlling the width or length of the recording magnetic domain accurately. (6) A magneto-optical recording medium, wherein the magneto-optical recording medium has at least a film having a melting point of 200 ° C. or more and 500 ° C. or less in addition to the magnetic film.

(7) A magneto-optical recording medium characterized in that the magneto-optical recording medium has at least a film having a melting point of 300 ° C. or higher and 400 ° C. or lower in addition to the magnetic film.

This makes it easy to manufacture a medium having a region in which at least one of thermal characteristics and optical characteristics is different.

In the present invention, the following means are used in order to solve the second object.

(8) In forming the partial area, the diameter of the light spot at the time of normal recording is 0.8 on the recording medium.
It was performed by irradiating light with a light spot diameter not more than twice.

As a result, it becomes easy to make the part of the area minute. That is, high density recording becomes easy.

(9) A method of manufacturing a magneto-optical recording medium in which a film having a melting point of 200 ° C. or more and 500 ° C. or less is provided, light is irradiated to melt the film, holes are formed, and then a magnetic film is provided.

As a result, it becomes easy to miniaturize the above-mentioned part of the region without thermally deteriorating the magnetic film.

In the present invention, the following means are used to solve the third object.

(10) At least an optical head for irradiating light for raising the temperature of the magnetic film, a magnetic field applying means for applying a magnetic field on the magnetic film, and for forming a desired recording magnetic domain. The magneto-optical recording medium includes a modulator for changing the intensity of the light or the intensity or direction of the magnetic field, and an automatic position controller for irradiating the light to a desired position on the recording medium. The magneto-optical recording device to be used, comprising at least a recording control means for forming a recording magnetic domain so that a domain wall is located at a boundary between the partial area and the other portion.

(11) The recording control means is at least
A light intensity control unit for controlling the intensity of the light and a timing control unit for controlling the time of the intensity change of the light or the magnetic field are arranged.

As a result, it becomes easy to accurately control the width or length of the recording magnetic domain for recording. That is,
It becomes easy to perform recording with high density and good signal quality.

[0028]

The recording medium of the present invention has at least one magnetic film, and the temperature of the magnetic film is raised by using light, and the direction of magnetization in the temperature rising portion is changed to record information. In the medium, the magnetic film has a region in which at least one of magnetic properties, thermal properties, and optical properties is different from other regions.

Therefore, for example, the magnetic characteristics in the magnetic film,
High sensitivity (recording at low temperature) can be achieved only in the area where at least one of thermal characteristics and optical characteristics is different from other areas. For example, the recording magnetic domain can be formed only in the upper high sensitivity region, and the magnetic domain does not spread to other regions. Therefore, it becomes easy to form a minute recording magnetic domain having the same size as a region where at least one of the magnetic characteristic, the thermal characteristic and the optical characteristic is different from the other portion.

Therefore, a minute region in which at least one of the magnetic characteristic, the thermal characteristic and the optical characteristic is different from other portions,
If it is formed in advance by using light with a short wavelength, high density recording can be stably performed.

Further, at this time, the shape and size of the recorded magnetic domain are determined by the shape and size of a minute region in which at least one of the magnetic property, the thermal property and the optical property which is formed in advance is different from other parts. Even if the laser light intensity during recording changes, magnetic domains having a constant shape and size can be formed, and high S / N (low noise) recording is possible.

In order to perform high density recording using the medium formed by such a method, for example, an optical head for irradiating light for raising the temperature of the magnetic film and a magnetic field applied on the magnetic film are applied. Magnetic field applying means, modulating means for changing the light intensity or the magnetic field strength or direction to form a desired recording magnetic domain, and an automatic position for irradiating light to a desired position on a recording medium. Using a device having a light intensity control unit for controlling the intensity of light or a timing control unit for controlling the time of intensity change of light or magnetization, including a control means, the magnetic characteristics, thermal characteristics and At least one of the characteristics is formed so as to coincide with a minute area different from other areas.

[0033]

【Example】

<< Embodiment 1 >> FIG. 1 shows an explanatory view of an embodiment of the magneto-optical recording medium of the present invention. The magneto-optical recording medium comprises at least a magnetic film 2 on a disk-shaped substrate 1. In this example, a magneto-optical recording film such as TbFeCo is used as the magnetic film 2. When using a magneto-optical recording film such as TbFeCo,
A magnetic film having a structure in which a dielectric layer 31 (film thickness 60 nm) and a protective layer 33 (film thickness 60 nm) are provided to sandwich the magnetic layer 32 (film thickness 80 nm) in order to increase the magneto-optical effect and the oxidation resistance. It is preferable to use. Of course, a metal layer such as a heat diffusion layer or a reflection layer may be provided if necessary. A region 3 having a low coercive force is provided on the magnetic film 2 as shown in FIG. The region 3 having a low coercive force can be arranged in various shapes on the disk, but by arranging it in a concentric circle shape or a spiral shape as shown in FIG. Therefore, in this embodiment, they are arranged in a spiral shape. At this time, the width of the region 3 having a low coercive force was set to 0.4 μm. The distance between the regions 3 having low coercive force is 0.3 μm.

Hereinafter, it will be explained that this medium is effective for increasing the density.

When recording is performed with the same bias magnetic field as shown in FIG. 3, an area having a low coercive force can be recorded at a lower temperature than an area having a high coercive force. That is, the region having a low coercive force has a higher recording sensitivity than other regions. Therefore, by irradiating light with an appropriate intensity to raise the temperature of the medium, as shown in FIG. 4, a region with high recording sensitivity in the medium,
That is, the recording magnetic domain can be formed only in the region 3 having a low coercive force. Therefore, the width of the recording magnetic domain is limited to the width (0.4 μm) of the region 3 having a low coercive force, regardless of the wavelength (spot diameter) of the recording laser light. That is, high density (narrow track) recording can be realized. 0.7μ in this example
Since narrow track recording of m pitch can be realized, if the recording bit pitch (linear recording density) is 0.3 μm, a recording density of 3 GB per square inch can be achieved.

In this example, the region 3 having a low coercive force is formed on the medium.
However, it is of course possible to provide a region 91 in which other magnetic characteristics, thermal characteristics, or optical characteristics are changed in place of the low coercive force area.

In this example, the region 3 having a low coercive force, or the region 91 in which the magnetic characteristics, the thermal characteristics, and the optical characteristics are changed has a concentric or spiral shape. The shape is another shape, for example
A shape in which a large number of substantially circular regions shown in FIG. 6 are arranged may be used. In this case, not only a narrow track but also a high linear recording density can be realized.

The magnetic film may be any film known as a magneto-optical recording film such as a PtCo film or a GdFeCo film other than the TbFeCo film. The effect of the present invention does not depend on the type of magnetic film.

Further, in FIG. 1, it is shown that light is applied to the recording film from the side opposite to the substrate.
For the sake of convenience of illustration, the effect of the present invention can be seen without any problem for the light for recording on either the substrate side or the side opposite to the substrate.

<Embodiment 2> FIGS. 7 and 8 are sectional views showing a part of one embodiment of the magneto-optical recording medium of the present invention. The magneto-optical recording medium includes a SnSbSe low melting point film 41 (film thickness 50 nm) having a small hole (groove) on a disk-shaped substrate 1 and a magnetic film 2. The diameter of this hole (width of the groove) is 0.4 μm. In this example, a magneto-optical recording film such as TbFeCo is used as the magnetic film 2 to form the magnetic layer 32 (film thickness 50 nm). In order to increase the magneto-optical effect and the oxidation resistance, the dielectric layer 31 (film thickness 70 nm) is used. ) And the protective layer 33 (film thickness 40n
m) is provided to sandwich the magnetic layer 32.

Since the optical characteristics and the thermal characteristics are different in the hole portion, the recording sensitivity is different. In this example, the film thickness of each layer is designed so that the recording sensitivity is high in the hole portion. That is, since the reflectance is reduced and the heat capacity is reduced in the hole portion, the temperature easily rises and the recording sensitivity is effectively increased.

This example is also effective for increasing the density as in the first embodiment.

Example 3 An example of a method of manufacturing the medium shown in Example 1 will be described.

First, the magnetic film 2 is laminated on the disk-shaped substrate 1. In this example, a TbFeCo magneto-optical recording film is used as the magnetic film 2 and the magnetic layer 32 is used. The dielectric layer 31 (film thickness 60 nm) is used to increase the magneto-optical effect and the oxidation resistance.
And a protective layer 33 (film thickness 60 nm) is provided, and the magnetic layer 32 (film thickness 8
0 nm) is sandwiched between the magnetic films. The dielectric layer 31, the magnetic layer 32, and the protective layer 33 were formed in this order by a high frequency magnetron sputtering method. Of course, a metal layer such as a heat diffusion layer or a reflection layer may be provided if necessary.

Next, the region 3 having a small coercive force is formed on the magnetic film. This is performed by irradiating the magnetic film 2 with light having a short wavelength (457 nm) having a higher intensity (6 mW) than the recording light (4 mW) with a lens having a large aperture ratio (0.8). At this time, the linear velocity was constant so that the characteristics did not change between the inner and outer circumferences. At this time, the width of the region 3 having a low coercive force is 0.4 μm. The distance between the regions 3 having low coercive force is 0.3 μm.
m (0.7 μm pitch).

The principle of forming the region 3 having a low coercive force by the above operation will be described with reference to FIG. Generally TbF
A magneto-optical recording film such as eCo has a lower coercive force when heated to 300 ° C. or higher (FIG. 9A). Further, when the magnetic film 2 is irradiated with light having a short wavelength, which is stronger than the recording light, with a lens having a large aperture ratio, and the temperature of a part of the magnetic film is raised, the temperature distribution at that time is as shown in FIG. 9B. become. Therefore,
By this operation, the temperature of the heated central portion exceeds 300 ° C., so that the coercive force is reduced and the region 3 having a low coercive force is formed. Therefore, the width of the part that exceeds 300 ℃ is 0.4μ.
Irradiation is performed by controlling light with high intensity so that m becomes m. This strong light has a short wavelength and a large numerical aperture, so 0.4
It is easy to control a small area of μm.

Although the temperature of the region where the coercive force starts to decrease is 300 ° C. here, this temperature is about 150 ° C. to 500 ° C. depending on the composition of the magnetic film, the film thickness, the film forming conditions and the like.
Varies between ° C.

Example 4 A method of manufacturing the recording medium of Example 2 will be described.

In the third embodiment, the change in the coercive force due to the irradiation of intense light is used, but in the present embodiment, SnSbSe is used.
A low melting point film 41 (perforation type optical recording film) is laminated and the low melting point film 41 is perforated with strong light similar to that of the third embodiment to form a hole portion of the second embodiment. in this case,
In order to prevent the substrate or the like from being deformed due to temperature rise due to light having high intensity, the melting point of the low melting point film 41 is preferably set to 500 ° C. or less. Further, in order to prevent the low melting point film 41 from being deformed at the time of recording information, the melting point of the low melting point film 41 is preferably at least higher than the recording temperature. That is, the melting point of the low melting point film 41 is preferably 200 ° C. or higher. More preferably, the temperature is preferably 300 ° C. or higher. In this case,
Increased reliability for repeated recording and playback.

In the case of FIG. 7, after laminating the low melting point film 41, strong light is irradiated to form a hole. Then, the recording film 2 is laminated in the same manner as in Example 3.

In the case of FIG. 8, holes are formed by irradiating strong light after stacking all the films. At that time, in order to prevent the magnetic film from being exposed to an extremely high temperature, it is desirable that the melting point of the low melting point film is 400 ° C. or less.

<Embodiment 5> An example of a manufacturing method different from that of Embodiment 3 of the medium shown in Embodiment 1 is shown in FIG.

An ultraviolet curable resin 23 having minute irregularities and flat portions is formed on a substrate, and the magnetic film 2 is formed on the ultraviolet curable resin 23.
Are laminated. In this example, a TbFeCo magneto-optical recording film is used as the magnetic film 2, and the magnetic layer 32 is used. In order to increase the magneto-optical effect and the oxidation resistance, the dielectric layer 31 (having a film thickness of 60 n) is used.
m) and a protective layer 33 (film thickness 60 nm) are provided, and the magnetic layer 32
A magnetic film having a structure sandwiching (thickness of 80 nm) was used. UV curable resin 23 having minute irregularities and flat portions on the substrate
In order to form the pattern, it is easy to transfer the pattern from a stamper having a minute uneven portion and a flat portion. This method
This is the same as the method used to create the guide groove or pit of the conventional optical disk substrate. Therefore, instead of using the ultraviolet curable resin layer 23, a method of forming a plastic substrate such as polycarbonate by an injection molding method may be used. In any case, it suffices to provide a portion having minute irregularities and a flat portion on the surface of the substrate.

In the medium thus produced, the coercive force of the magnetic film 2 is different between the minute uneven portion and the flat portion, and as a result, a medium having a portion with low coercive force and a portion with no coercive force can be obtained. Out. That is, the recording medium of Example 1 can be obtained.

In this case, it is desirable that the size of the fine uneven portion or the flat portion be 0.6 μm or less in order to increase the density. In order to increase the S / N ratio (reduce noise), it is preferable that the height of the minute unevenness itself is 2 nm or more and 20 nm or less, and the size of the unevenness itself is 0.1 μm or less.

<Embodiment 6> FIG. 11 shows a block diagram of a magneto-optical recording apparatus of the present invention.

Using the magneto-optical recording medium 12 of the present invention, an optical head for irradiating the magneto-optical recording medium 12 with light for recording and reproduction is provided, and the optical head is controlled by position control means such as auto-focusing and tracking. , Is positioned at a position where information should be recorded / reproduced. When information is recorded, the intensity of light and the intensity of magnetic field are modulated by a modulation means according to the information to be recorded. At that time, the magnetic domains formed by recording have magnetic or thermal characteristics shown in FIG.
The timing control unit controls the irradiation time (timing) of light or magnetic field in accordance with the clock generated by the clock generation circuit based on the reproduction signal so as to approximately match the region 91 where the optical characteristics have changed. If the region 91 where the magnetic characteristic, the thermal characteristic, or the optical characteristic has changed has a concentric circle or spiral shape as shown in FIG. 5, the timing control circuit is not necessary.

In this embodiment, the recording medium having the structure shown in FIG. 6 is used, and position control such as autofocusing and tracking is performed by the sample servo recording method, and when recording information, according to the information to be recorded. The intensity of light and the intensity of the magnetic field are modulated by the modulation means. At that time, a clock generation circuit is created based on the reproduction signal so that the recorded and formed magnetic domains substantially match the regions 91 in which the magnetic characteristics, the thermal characteristics, and the optical characteristics are changed as shown in FIG. The timing control unit controls the irradiation time (timing) of light or magnetic field according to the clock.

With this method, high density recording of 3 gigabytes or more per square inch was possible.

[0060]

According to the present invention, it is possible to stably form a recording magnetic domain smaller than the light spot, so that high density recording of 3 gigabytes or more per square inch is possible.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of a magneto-optical recording medium of the present invention.

FIG. 2 is an explanatory diagram showing an example of a conventional magneto-optical recording medium.

FIG. 3 is an explanatory diagram of the principle of one embodiment of the present invention.

FIG. 4 is an explanatory diagram of the principle of the present invention.

FIG. 5 is a perspective view showing an embodiment of the magneto-optical recording medium of the present invention.

FIG. 6 is a perspective view showing a second embodiment of the magneto-optical recording medium of the present invention.

FIG. 7 is an explanatory diagram showing an embodiment of a magneto-optical recording medium of the present invention.

FIG. 8 is a sectional view showing an embodiment of the magneto-optical recording medium of the present invention.

FIG. 9 is an explanatory view of the principle of the method for manufacturing a magneto-optical recording medium of the present invention.

FIG. 10 is a cross-sectional view showing one embodiment of a method of manufacturing a magneto-optical recording medium of the present invention.

FIG. 11 is a block diagram showing an embodiment of a magneto-optical recording apparatus of the present invention.

[Explanation of symbols]

1 ... Substrate, 2 ... Magnetic film, 3 ... Low coercive force region, 4 ... Recording film, 5 ... Recording magnetic domain, 6 ... Light spot, 7 ... Lens, 8
... laser light, 17 ... magnetic field, 18 ... magnetic field applying means.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location G11B 11/10 586 B 9296-5D (72) Inventor Hiroyuki Awano 1-280, Higashi Koikeku, Kokubunji, Tokyo Central Research Laboratory, Hitachi, Ltd.

Claims (11)

[Claims] 1. In a magneto-optical recording medium comprising at least one magnetic film, when a temperature is gradually raised while applying a constant magnetic field to the magneto-optical recording medium, only a part of the magnetic film is inverted. A magneto-optical recording medium characterized in that there is a temperature that can form magnetic domains and cannot exist in other regions. 2. In a magneto-optical recording medium comprising at least one magnetic film, when a magnetic field applied to the magneto-optical recording medium at a constant temperature is gradually increased, a reversed magnetic domain is formed only in a part of the magnetic film. A magneto-optical recording medium characterized by the presence of a magnetic field that can be generated and cannot be generated in other areas. 3. A magneto-optical recording medium having a magnetic film of at least one layer, wherein a part of a region having high recording sensitivity is present in the magnetic film. 4. A magneto-optical recording medium comprising at least one magnetic film, wherein the magnetic film has a part of a region having a low coercive force. 5. The magneto-optical recording medium according to claim 1, 2, 3 or 4, wherein the width and / or the length of the partial area is smaller than either the width or the length of the information recording unit. 6. The method according to claim 1, 2, 3, 4 or 5.
The magneto-optical recording medium has a melting point of 200 in addition to the magnetic film.
A magneto-optical recording medium including a film having a temperature of not less than 500 ° C. and not more than 500 ° C. 7. The method according to claim 1, 2, 3, 4 or 5,
The magneto-optical recording medium has a melting point of 300 in addition to the magnetic film.
A magneto-optical recording medium including a film at a temperature of not less than 400 ° C. and not more than 400 ° C. 8. The method according to claim 1, 2, 3, 4 or 5.
A method for manufacturing a magneto-optical recording medium, which comprises forming a part of the region by irradiating the recording medium with light having a light spot diameter not more than 0.8 times the light spot diameter at the time of normal recording. 9. A magneto-optical recording medium comprising a film having a melting point of 200 ° C. or more and 500 ° C. or less, irradiating light to melt the film to form a hole, and then providing a magnetic film. Production method. 10. An optical head for irradiating at least light for raising the temperature of a magnetic film, a magnetic field applying means for applying a magnetic field on the magnetic film, and the light for forming a desired recording magnetic domain. Using a magneto-optical recording medium having a modulation means for changing the intensity of the magnetic field or the intensity or direction of the magnetic field, and an automatic position control means for irradiating the light to a desired position on the recording medium. A magneto-optical recording apparatus comprising: a recording control unit for forming a recording magnetic domain so that a domain wall is located at a boundary between the partial region and the other portion according to claim 1. Magneto-optical recording device. 11. The recording control means according to claim 9, further comprising a light intensity control unit for controlling the intensity of the light, and a timing control unit for controlling the time of the intensity change of the light or the magnetic field. Magneto-optical recording device.