JPH06150418A - Magneto-optical recording medium and recording and reproducing method - Google Patents

Abstract

PURPOSE:To execute high-density recording by providing a reading-out layer which exhibits intra-surface magnetization dominant with intra-surface magnetic anisotropy within a chamber and migrates to perpendicular magnetization dominant with perpendicular magnetic anisotropy with an increase in temp. and a recording layer thereon. CONSTITUTION:A transparent dielectric substance layer 2, the reading-out layer 3, a recording layer 4, a protective layer 5 and an over coat layer 6 are formed on a substrate 1. The layer 3 exhibits the intra-surface magnetization dominant with the intra-surface magnetic anisotropy within the chamber and migrates to the perpendicular magnetization dominant with the perpendicular magnetic anisotropy with the increase in temp. Only the part where the temp. rises exhibits an extreme Kerr effect when the part where the temp. rises shifts from the intra-surface magnetization to the perpendicular magnetization. Information is thus reproduced in accordance with the reflected light from this part. The temp. of the previous reproducing part falls at the time of reproducing the next recording pit by movement of a light beam. The perpendicular magnetization shifts to the intra-surface magnetization and the extreme Kerr effect is not longer exhibited. The layer 3 shifts sharply in the magnetization from the intra-surface magnetization to the perpendicular magnetization by using GdFeCo. The noises at the time of reproducing decrease and the recording at the higher density is possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium such as a magneto-optical disk, a magneto-optical tape, a magneto-optical card, etc., applied to a magneto-optical recording apparatus, and a recording / reproducing method for the magneto-optical recording medium. .

[0002]

2. Description of the Related Art Magneto-optical discs are being researched and developed as rewritable optical discs, and some of them have already been put to practical use as external memories for computers.

Since a magneto-optical disk uses a perpendicular magnetization film as a recording medium and performs recording and reproduction by using light, a large recording capacity can be realized as compared with a floppy disk or a hard disk using an in-plane magnetization film.

[0004]

However, in the above conventional structure, the recording density of the magneto-optical disk depends on the size of the light beam used for recording / reproducing on the recording medium. In addition, there is a problem that the storage capacity cannot be increased.

That is, when the recording bit size and the recording bit interval become smaller than the light beam spot diameter, a plurality of recording bits including adjacent recording bits enter the light beam spot. Therefore, there is a problem in that noise increases and it becomes impossible to reproduce each recorded bit separately.

As means for reducing the light beam spot diameter in order to increase the recording density, the wavelength of the laser as the light source is shortened, the numerical aperture (NA) of the objective lens is increased, and the angle of narrowing the light is adjusted. It can be increased.

Regarding the shortening of the wavelength of lasers, the development of semiconductor lasers for short wavelengths has been vigorously carried out. However, the emission intensity is still weak and it cannot be used as a light source for recording / reproducing of a magneto-optical disk.

When the NA is increased, it is necessary to make the inclination between the objective lens for converging the light beam into the light beam spot and the surface of the magneto-optical disk as small as possible.
Otherwise, the diameter of the light beam spot on the recording medium will be large on the contrary. In other words, if the NA is increased, the assembly accuracy of the optical system of the magneto-optical disk device or the warp amount of the magneto-optical disk must be controlled more strictly than before.
A new problem occurs that the light beam spot diameter becomes large.

For this reason, the wavelength of the semiconductor laser used in the current magneto-optical disk is 780 to 830 nm, and the NA of the objective lens is 0.45 to 0.55. Therefore, the diameter of the light beam spot on the recording medium is 1.7 to 2.0 μm.

In consideration of this light beam spot diameter,
The track pitch of the magneto-optical disk, that is, the recording bit interval in the radial direction of the magneto-optical disk is set to 1.4 to 1.6 μm.

If the track pitch is made smaller than this,
At the time of reproduction, it is necessary to suppress crosstalk in which information recorded in adjacent tracks leaks. Therefore, a compensating circuit for performing special waveform processing must be provided, which causes a problem that the magneto-optical disk device becomes complicated.

Next, in order to obtain a sufficiently large magnetic field when performing magnetic field modulation overwriting on the magneto-optical disk,
There is a problem that the magnetic field generation mechanism must be close to the magneto-optical disk, and there is a problem that the magnetic field cannot be modulated at high speed.

In order to solve these problems, Japanese Patent Laid-Open No. 175948/1987 uses a magneto-optical recording medium having a two-layer structure composed of a recording layer using a perpendicular magnetization film and a recording auxiliary layer, and uses only a laser power. A light modulation overwrite method has been proposed in which the light is modulated to overwrite.

However, in this optical modulation overwrite method, the magnetization direction of the recording auxiliary layer also changes when overwriting is performed. Therefore, it is necessary to align the magnetization direction of the recording auxiliary layer each time before overwriting. Therefore, in addition to the recording magnetic field generating mechanism, an initializing magnetic field generating mechanism is required, which leads to an increase in size of the magneto-optical disk device and
There is a problem that it also leads to cost increase.

[0015]

In order to solve the above-mentioned problems, a magneto-optical recording medium according to the invention of claim 1 is provided with a translucent substrate and an in-plane magnetism formed at room temperature at room temperature. A reading layer that exhibits in-plane magnetization in which anisotropy is dominant, and shifts to perpendicular magnetization in which perpendicular magnetic anisotropy is dominant with a rise in temperature, and a recording layer that is formed on the reading layer and magneto-optically records information. And the read layer is GdFeCo.

The magneto-optical recording medium according to the invention of claim 2 is
In order to solve the above problems, the recording layer according to claim 1 is Dy.
FeCo is a feature.

A magneto-optical recording medium according to the invention of claim 3 is
In order to solve the above-mentioned problems, the magneto-optical recording medium according to claim 1 or 2, wherein a transparent dielectric layer is formed between the substrate and the read layer, and the protective layer is provided on the recording layer. A layer is formed, and at least one of the transparent dielectric layer and the protective layer is AlN.

The magneto-optical recording medium according to the invention of claim 4 is
In order to solve the above problems, a transparent substrate, a transparent dielectric layer formed on the substrate, and a surface formed on the transparent dielectric layer and having an in-plane magnetic anisotropy at room temperature are superior. A reading layer that exhibits internal magnetization and that changes to perpendicular magnetization in which perpendicular magnetic anisotropy predominates as the temperature rises, a recording layer that is formed on the reading layer, and magneto-optically records information, and a reading layer that is formed on the recording layer. And a protective layer, and at least one of the transparent dielectric layer and the protective layer is made of a transparent dielectric material containing no oxygen.

A magneto-optical recording medium according to the invention of claim 5 is
In order to solve the above problems, the transparent dielectric material containing no oxygen according to claim 4 is SiN, AlSiN, AlTa.
It is characterized by being any one of N, TiN, BN, and ZnS.

The magneto-optical recording medium according to the invention of claim 6 is
In order to solve the above problems, a transparent substrate, a transparent dielectric layer formed on the substrate, and a surface formed on the transparent dielectric layer and having an in-plane magnetic anisotropy at room temperature are superior. A reading layer that exhibits internal magnetization and that changes to perpendicular magnetization in which perpendicular magnetic anisotropy predominates as the temperature rises, a recording layer that is formed on the reading layer, and magneto-optically records information, and a reading layer that is formed on the recording layer. And a protective layer, and at least one of the transparent dielectric layer and the protective layer is made of a transparent dielectric material containing nitrogen.

The magneto-optical recording medium according to the invention of claim 7 is
In order to solve the above problems, the transparent dielectric material containing nitrogen according to claim 6 is SiN, AlSiN, AlTaN, T.
It is characterized by being any one of iN, BN, SiAlON, and TiON.

The magneto-optical recording medium according to the invention of claim 8 is
In order to solve the above problems, a transparent substrate, a transparent dielectric layer formed on the substrate, and a surface formed on the transparent dielectric layer and having an in-plane magnetic anisotropy at room temperature are superior. A reading layer that exhibits internal magnetization and that changes to perpendicular magnetization in which perpendicular magnetic anisotropy predominates as the temperature rises, a recording layer that is formed on the reading layer, and magneto-optically records information, and a reading layer that is formed on the recording layer. And a protective layer, and at least one of the transparent dielectric layer and the protective layer is made of a transparent dielectric material having a refractive index of 2.2 or more.

The magneto-optical recording medium according to the invention of claim 9 is
In order to solve the above problems, the refractive index of claim 8 is 2.
Two or more transparent dielectric materials are TiN, ZnS, Ti
It is characterized by being any one of ON, TiO ₂ , BaTiO ₃ , and SrTiO ₃ .

In order to solve the above-mentioned problems, a magneto-optical recording medium according to the invention of claim 10 is a GdFe according to claim 1.
The read layer made of Co is characterized in that at least one element selected from Nd, Pr, Pt, and Pd is added.

In order to solve the above problems, a magneto-optical recording medium according to the invention of claim 11 is the GdFe of claim 1.
At least one of Cr, Ni, Mn, Be, V, and Nb is added to at least one of the read layer made of Co and the recording layer.

In order to solve the above-mentioned problems, a magneto-optical recording medium according to a twelfth aspect of the present invention is formed of a light-transmissive substrate and a substrate, and has in-plane magnetic anisotropy at room temperature. While having in-plane magnetization, it has a read layer in which the perpendicular magnetic anisotropy shifts to the dominant perpendicular magnetization as the temperature rises, and a recording layer formed on the read layer for magneto-optically recording information, The recording layer is made of TbFeCo.

In order to solve the above-mentioned problems, a magneto-optical recording medium according to a thirteenth aspect of the present invention is formed of a light-transmissive substrate, and is formed on the substrate and has in-plane magnetic anisotropy at room temperature. While having in-plane magnetization, it has a read layer in which the perpendicular magnetic anisotropy shifts to the dominant perpendicular magnetization as the temperature rises, and a recording layer formed on the read layer for magneto-optically recording information, The readout layer is made of a rare-earth transition metal amorphous alloy having ferrimagnetism and has a compensation temperature of 125.
The composition is set to be ℃ or more, and the film thickness is 10
It is characterized by being set to nm or more.

In order to solve the above-mentioned problems, a magneto-optical recording medium according to a fourteenth aspect of the present invention is formed of a light-transmissive substrate and a substrate, and has in-plane magnetic anisotropy at room temperature. While having in-plane magnetization, it has a read layer in which the perpendicular magnetic anisotropy shifts to the dominant perpendicular magnetization as the temperature rises, and a recording layer formed on the read layer for magneto-optically recording information, The read-out layer is made of a rare-earth transition metal amorphous alloy having ferrimagnetism, has a composition so that the Curie temperature is 130 ° C. or higher without a compensation temperature, and the film thickness is 10 nm or higher. It is characterized by being set.

In order to solve the above-mentioned problems, a magneto-optical recording medium according to a fifteenth aspect of the present invention is formed of a light-transmissive base and a base, and has in-plane magnetic anisotropy at room temperature. While having in-plane magnetization, it has a read layer in which the perpendicular magnetic anisotropy shifts to the dominant perpendicular magnetization as the temperature rises, and a recording layer formed on the read layer for magneto-optically recording information, A groove for guiding a light beam is provided on the surface of the substrate on the side of the readout layer, and the width of the groove is set to be substantially equal to the width of the land between the grooves. There is.

In order to solve the above problems, the magneto-optical recording medium according to the sixteenth aspect of the present invention is characterized in that information is magneto-optically recorded in the recording layer on the groove and the recording layer on the land. It has a feature.

In order to solve the above-mentioned problems, a magneto-optical recording medium according to a seventeenth aspect of the present invention is formed of a light-transmissive substrate, and is formed on the substrate, and has in-plane magnetic anisotropy at room temperature. While having an in-plane magnetization state, it has a read layer that shifts to a perpendicular magnetization state in which the perpendicular magnetic anisotropy is dominant as the temperature rises, and a recording layer formed on the read layer for magneto-optically recording information. The readout layer is made of a rare earth transition metal alloy, the compensation temperature is set so as not to be between room temperature and the Curie temperature, and the rare earth metal content is higher than the maximum content corresponding to the compensation composition. It is characterized in that it is set so as to increase.

In order to solve the above problems, the magneto-optical recording medium according to the eighteenth aspect of the present invention is provided with an intermediate layer made of an in-plane magnetized film between the read layer and the recording layer. It is characterized by

A recording / reproducing method according to a nineteenth aspect of the invention is
In order to solve the above-mentioned problems, a translucent substrate and an in-plane magnetized state formed on the substrate, in which the in-plane magnetic anisotropy is dominant, at room temperature, the perpendicular magnetic anisotropy increases as the temperature rises. A read layer that shifts to a perpendicular magnetization state in which the property is superior, and a recording layer that is formed on the read layer and magneto-optically records information, and the read layer is made of a rare earth transition metal alloy, Use a magneto-optical recording medium whose compensation temperature is set so as not to be between room temperature and Curie temperature, and whose rare earth metal content is set to be higher than the maximum content corresponding to the compensation composition. A recording / reproducing method for recording / reproducing information, wherein a relatively low first laser power and a relatively high second laser power are applied according to a recording signal while applying a constant magnetic field for magnetizing a read layer. Switched laser light Recording is performed by reversing the magnetization direction of the recording layer by irradiating, and by irradiating a laser beam with a laser power lower than the first laser power, a region smaller than the laser spot diameter of the reading layer is perpendicularly magnetized. State, and align the sub-lattice magnetization of the region in the perpendicular magnetization state of the read layer in a stable direction with respect to the sub-lattice magnetization of the recording layer. It is characterized by playing back.

In order to solve the above-mentioned problems, a magneto-optical recording medium according to a twentieth aspect of the present invention is formed of a light-transmissive substrate and a substrate, and has in-plane magnetic anisotropy at room temperature. While having an in-plane magnetization state, it has a read layer that shifts to a perpendicular magnetization state in which the perpendicular magnetic anisotropy is dominant as the temperature rises, and a recording layer formed on the read layer for magneto-optically recording information. It is characterized in that an intermediate layer made of a non-magnetic film is provided between the read layer and the recording layer.

The recording / reproducing method according to the invention of claim 21 is
In order to solve the above-mentioned problems, a translucent substrate and an in-plane magnetization formed on the substrate, in which the in-plane magnetic anisotropy is dominant, at room temperature, the perpendicular magnetic anisotropy increases as the temperature rises. Has a read layer that shifts to the predominant perpendicular magnetization and a recording layer formed on the read layer for magneto-optically recording information, and guides a light beam to the surface of the above-mentioned substrate on the read layer side. A recording / reproducing method using a magneto-optical recording medium in which a groove for setting is provided, and the width of the groove is set to be substantially equal to the width of the land between the grooves.
The recording layer on the groove and the recording layer on the land are used for recording and reproducing information.

[0036]

According to the structure of claim 1, when the reading layer is irradiated with the light beam during the reproducing operation, the temperature distribution of the irradiated portion becomes almost Gaussian distribution. The temperature rises only in the vicinity area.

As the temperature rises, the magnetization of the temperature rise portion shifts from in-plane magnetization to perpendicular magnetization. At this time, the magnetization direction of the reading layer follows the magnetization direction of the recording layer due to the exchange coupling force between the two layers of the reading layer and the recording layer.

When the temperature rising portion shifts from the in-plane magnetization to the perpendicular magnetization, only the temperature rising portion exhibits the polar Kerr effect, and the information is reproduced based on the reflected light from the portion.

Then, when the light beam moves to reproduce the next recorded bit, the temperature of the previous reproducing portion lowers and the perpendicular magnetization changes to the in-plane magnetization, so that the polar Kerr effect is not exhibited. This means that the magnetization recorded in the recording layer is masked by the in-plane magnetization of the read layer and cannot be read. This eliminates signal mixing from adjacent recorded bits that causes noise and reduces reproduction resolution.

As described above, since only the area heated to a predetermined temperature or higher is involved in the reproduction, it becomes possible to reproduce the recording bit smaller than the conventional one, and the recording density is remarkably improved.

By adopting GdFeCo, which is a rare earth transition metal alloy, as the material of the read layer, it is possible to realize a read layer in which the magnetization direction changes from the in-plane magnetization to the perpendicular magnetization very sharply. As a result, noise during reproduction is reduced, so that it is possible to provide a magneto-optical recording medium capable of recording at higher density.

According to the structure of claim 2, in addition to the effect of claim 1, the perpendicular magnetic anisotropy is reduced by using DyFeCo as the material of the recording layer. As a result, the external magnetic field during recording can be reduced.

According to the structure of claim 3, in addition to the effect of claim 1 or 2, a transparent dielectric layer is formed between the substrate and the reading layer, and a protective layer is formed on the recording layer, At least one of the transparent dielectric layer and the protective layer is Al
Since it is N, a magneto-optical recording medium having excellent moisture resistance can be provided.

According to the structure of claim 4, since at least one of the transparent dielectric layer and the protective layer is made of a transparent dielectric material containing no oxygen, an excellent magneto-optical recording medium can be provided.

According to the structure of claim 5, in addition to the function of claim 4, the transparent dielectric material containing no oxygen is replaced with Si.
Since any of N, AlSiN, AlTaN, TiN, BN, and ZnS is used, a magneto-optical recording medium excellent in long-term reliability can be provided.

According to the structure of claim 6, since at least one of the transparent dielectric layer and the protective layer is made of a transparent dielectric material containing nitrogen, an excellent magneto-optical recording medium can be provided.

According to the structure of claim 7, in addition to the function of claim 6, the transparent dielectric material containing nitrogen is replaced by SiN, A
lSiN, AlTaN, TiN, BN, SiAlON,
Since either of TiON is used, a magneto-optical recording medium having excellent long-term reliability can be provided.

According to the structure of claim 8, at least one of the transparent dielectric layer and the protective layer has a refractive index of 2.
Since the transparent dielectric material is 2 or more, an excellent magneto-optical recording medium can be provided.

According to the structure of claim 9, in addition to the effect of claim 8, the transparent dielectric material having the refractive index of 2.2 or more is made of TiN, ZnS, TiO, TiO ₂ , and BaTiO 3.
₃ or SrTiO ₃ , it is possible to provide an excellent magneto-optical recording medium.

According to the structure of claim 10, in addition to the function of claim 1, the read layer made of GdFeCo contains N.
Since at least one element selected from d, Pr, Pt, and Pd is added, the reproduction signal becomes large when a short wavelength laser is used as the light source.

According to the structure of claim 11, in addition to the function of claim 1, at least one of the read layer made of GdFeCo and the recording layer has Cr, Ni, and
Since at least one element selected from Mn, Be, V, and Nb is added, long-term reliability is improved.

According to the structure of claim 12, in addition to the effect of claim 1, since the recording layer is made of TbFeCo, the perpendicular magnetic anisotropy becomes large. This makes it possible to provide a magneto-optical recording medium with high reproduction signal quality.

According to the thirteenth aspect, the readout layer is made of a rare-earth transition metal amorphous alloy having ferrimagnetism, the composition is set so that the compensation temperature is 125 ° C. or higher, and Since the film thickness is set to 10 nm or more, the reproduction signal quality at the time of reading the information recorded at high density is improved.

According to the structure of the fourteenth aspect, the read layer is made of a rare earth transition metal amorphous alloy having ferrimagnetism, and has a Curie temperature of 13 without a compensation temperature.
The composition is set to be 0 ° C or higher and the film thickness is 1
Since it is set to 0 nm or more, the reproduction signal quality at the time of reading information recorded at high density is improved.

According to the structure of the fifteenth aspect, a groove for guiding the light beam is provided on the surface of the substrate on the side of the readout layer, and the width of the groove becomes substantially equal to the width of the land between the grooves. Since the settings are made as described above, the reproduction signal quality when reading the information recorded in the recording layer on the groove and the information recorded in the recording layer on the land become the same.

According to the structure of the sixteenth aspect, in addition to the function of the fifteenth aspect, since information is magneto-optically recorded on the recording layer on the groove and the recording layer on the land, the recording density is doubled.

According to the seventeenth aspect, the readout layer is made of a rare earth-transition metal alloy, the compensation temperature is set so as not to be between room temperature and the Curie temperature, and the content of the rare earth metal is set. Since the content is set to be larger than the maximum content corresponding to the compensating composition, it is possible to provide a magneto-optical recording medium capable of high-density recording and reproduction.

According to the structure of claim 18, in addition to the function of claim 17, since the intermediate layer made of the in-plane magnetized film is provided between the read layer and the recording layer, the read layer and the recording layer. It becomes possible to control the exchange coupling force of. This increases the selection range of materials for the read layer and the recording layer.

According to the structure of claim 19, high density recording and reproduction can be performed by using the magneto-optical recording medium of claim 17.

According to the twentieth aspect, since the intermediate layer made of a nonmagnetic film is provided between the read layer and the recording layer, the exchange coupling between the read layer and the recording layer is weakened. . As a result, it is possible to provide a magneto-optical recording medium that can stably perform high density recording.

According to the twenty-first aspect, since the recording layer on the groove and the recording layer on the land are used for recording and reproducing information, the recording density is doubled.

[0062]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The first embodiment of the present invention will be described below with reference to FIGS.

As shown in FIG. 1, the magneto-optical disk (magneto-optical recording medium) of this embodiment has a substrate 1 (base), a transparent dielectric layer 2, a read layer 3, a recording layer 4, a protective layer 5, and an overcoat. The coat layer 6 has a structure laminated in this order.

As shown in the magnetic phase diagram of FIG. 2, the rare earth transition metal alloy used as the readout layer 3 has a very narrow composition range (indicated by A in the figure) showing perpendicular magnetization. This is because the perpendicular magnetization appears only near the compensating composition (indicated by P in the figure) in which the moments of the rare earth metal and the transition metal are balanced.

The magnetic moments of the rare earth metal and the transition metal have different temperature characteristics, and the magnetic moment of the transition metal becomes larger than that of the rare earth metal at high temperatures. Therefore, the content of the rare earth metal is set to be larger than that of the compensating composition at room temperature so that the in-plane magnetization does not appear at room temperature but the perpendicular magnetization does. In this case, when the temperature of the irradiation site rises due to the irradiation of the light beam, the magnetic moment of the transition metal becomes relatively large and becomes balanced with the magnetic moment of the rare earth metal, so that the perpendicular magnetization is exhibited. Become.

3 to 6 show an example of the hysteresis characteristic of the readout layer 3, where the horizontal axis represents the readout layer 3.
Is the external magnetic field (Hex) applied in the direction perpendicular to the film surface, and the vertical axis is the polar Kerr rotation angle (θk) when light is incident from the same direction perpendicular to the film surface.

FIG. 3 shows the composition P in the magnetic phase diagram of FIG.
4 shows the hysteresis characteristics of the readout layer 3 from room temperature to the temperature T _1. FIGS. 4 to 6 show the hysteresis characteristics from the temperature T ₁ to the temperature T ₂ and the temperatures T ₂ to the temperature T _{3, respectively.} hysteresis characteristic up, and shows the hysteresis characteristic from the temperature T ₃ to the Curie temperature Tc.

In the temperature range from the temperature T ₁ to the temperature T ₃ , the polar Kerr rotation angle exhibits a steep rise with respect to the external magnetic field, but in other temperature ranges, the polar Kerr rotation angle is almost zero. .

By using the rare earth transition metal having the above characteristics in the read layer 3, the recording density of the magneto-optical disk can be increased. That is, it is possible to reproduce recorded bits smaller than the size of the light beam. This will be described below.

During the reproducing operation, the reproducing light beam 7 is applied to the readout layer 3 from the substrate 1 (FIG. 1) side through the condenser lens 8. The temperature of the part of the readout layer 3 irradiated with the reproduction light beam 7 is highest in the vicinity of the central part thereof and is higher than the temperature of the peripheral part. This is because the reproduction light beam 7
Since the light is condensed to the diffraction limit by the condenser lens 8, its light intensity distribution has a Gaussian distribution, and the temperature distribution of the reproducing portion on the magneto-optical disk also has a Gaussian distribution.

When the intensity of the reproduction light beam 7 is set so that the temperature in the vicinity of the center reaches T ₁ or higher and the temperature in the peripheral portion becomes T ₁ or lower, only the region having the temperature of T ₁ or higher is reproduced. Therefore, the recording bit smaller than the diameter of the reproduction light beam 7 can be reproduced, and the recording density can be remarkably improved.

That is, the magnetization in the region having a temperature of T ₁ or higher shifts from in-plane magnetization to vertical magnetization (the hysteresis characteristic of polar Kerr rotation angle shifts from FIG. 3 to FIG. 4 or FIG. 5). At this time, the magnetization direction of the recording layer 4 is transferred to the reading layer 3 by the exchange coupling force between the two layers of the reading layer 3 and the recording layer 4. On the other hand, since the temperature is T ₁ or less in the peripheral region other than the region corresponding to the vicinity of the center of the reproduction light beam 7, the in-plane magnetization state (FIG. 3) is maintained. As a result, the polar Kerr effect is not exhibited with respect to the reproduction light beam 7 irradiated from the direction perpendicular to the film surface.

In this way, when the temperature rising portion shifts from the in-plane magnetization to the perpendicular magnetization, only the vicinity of the center of the reproducing light beam 7 exhibits the polar Kerr effect, and based on the reflected light from the portion, The information recorded on the recording layer 4 is reproduced.

When the reproducing light beam 7 moves (actually, the magneto-optical disk rotates) to reproduce the next recording bit, the temperature of the previous reproducing portion drops to T ₁ or less, and the perpendicular magnetization is lost. Transition to in-plane magnetization. Along with this, the region where the temperature is lowered does not exhibit the polar Kerr effect. Therefore, the information is not reproduced from the portion where the temperature is lowered, and the signal mixture from the adjacent recording bit, which is a cause of noise, is eliminated.

As described above, when the magneto-optical disk of the present invention is used, the recording bit smaller than the diameter of the reproducing light beam 7 can be surely reproduced, and the adjacent recording bits are not affected, so that the recording density can be improved. It can be significantly increased.

Next, a specific example of the magneto-optical disk of this embodiment will be shown.

The substrate 1 is made of a disk-shaped glass having a diameter of 86 mm, an inner diameter of 15 mm and a thickness of 1.2 mm. Although not shown in the drawings, a concave-convex guide track for guiding the light beam has a pitch of 1.6 μm, a groove (concave) width of 0.8 μm, and a land (convex) on one surface of the substrate 1. The width is 0.8 μm. That is, the width of the groove and the width of the land are formed to be 1: 1.

On the surface of the substrate 1 on which the guide track is formed, A1N having a thickness of 80 n is formed as the transparent dielectric layer 2.
It is formed by m.

On the transparent dielectric layer 2, GdFeCo, which is a rare-earth transition metal alloy thin film, is used as the read-out layer 3.
It is formed with a thickness of 50 nm. The composition of GdFeCo is Gd _0.26 (Fe _0.82 Co _0.18 ) _0.74 , and its Curie temperature is about 300 ° C.

On the read-out layer 3, as a recording layer 4, a rare earth-transition metal alloy thin film, DyFeCo, having a thickness of 50 n was used.
It is formed by m. The composition of DyFeCo is Dy _0.23
(Fe _0.78 Co _0.22 ) _0.77 , and its Curie temperature is about 200 ° C.

Due to the combination of the read layer 3 and the recording layer 4 described above, the magnetization direction of the read layer 3 is substantially in-plane (that is, the layer direction of the read layer 3) at room temperature, and 100
The temperature shifts from the in-plane direction to the vertical direction at a temperature of about 125 ° C.

On the recording layer 4, as a protective layer 5, A1N
Are formed with a thickness of 20 nm.

On the protective layer 5, a polyurethane acrylate-based UV curable resin is formed as the overcoat layer 6 with a thickness of 5 μm.

The above magneto-optical disk was manufactured by the following procedure.

The guide track on the surface of the glass substrate 1 was formed by the reactive ion etching method.

Transparent dielectric layer 2, readout layer 3, recording layer 4
The protective layer 5 and the protective layer 5 were both formed by the sputtering method in the same sputtering apparatus without breaking the vacuum. A1N of the transparent dielectric layer 2 and the protective layer 5 is the same as the A1 target.
It was formed by the reactive sputtering method of sputtering in a _two- gas atmosphere. The read layer 3 and the recording layer 4 are made of FeC.
It was formed by sputtering with Ar gas using a so-called composite target in which Gd or Dy chips were arranged on an o alloy target, or a ternary alloy target of GdFeCo and DyFeCo.

The overcoat layer 6 was formed by applying a polyurethane acrylate type ultraviolet curable resin with a spin coater and then applying ultraviolet rays with an ultraviolet ray irradiation device to cure the resin.

Next, the result of the operation confirmation performed using the above magneto-optical disk will be described.

Due to the combination of the read layer 3 and the recording layer 4 described above, the magnetization direction of the read layer 3 is substantially in-plane at room temperature and shifts from the in-plane direction to the vertical direction at a temperature of about 100 to 125 ° C. .

FIG. 7 and FIG. 8 are diagrams showing the results of actual measurement of the hysteresis characteristics of the polar Kerr rotation angle while changing the temperature. FIG. 7 shows the hysteresis characteristic at room temperature (25 ° C.), and the polar Kerr rotation angle is almost zero when the external magnetic field (Hex) is zero. This indicates that the direction of magnetization is almost in the direction perpendicular to the film surface and is in the in-plane direction. FIG. 8 shows the hysteresis characteristic at 120 ° C. It can be seen that even when the external magnetization is zero, there is a polar Kerr rotation angle of about 0.5 deg, and the magnetization has shifted to perpendicular magnetization.

The above is the confirmation of the static characteristics. Next,
The result of the dynamic measurement using the optical pickup will be described. The wavelength of the semiconductor laser of the optical pickup used for the measurement was 780 nm, and the numerical aperture of the objective lens (N.
A. ) Is 0.55.

First, the radius 26.
Rotation speed 1800 rpm (Line speed 5
m / sec), 0.765 μm long single frequency recording bits were pre-recorded. For recording, first, the magnetization direction of the recording layer 4 is aligned in one direction (erased state), and then the direction of the external magnetic field for recording is fixed in the opposite direction to the erasing direction. Was performed by modulating the laser at a recording frequency corresponding to (in this case, about 3.3 MHz). The recording laser power was about 8 mW.

FIG. 9 shows the result of examining the amplitude of the reproduced signal waveform by reproducing this recorded bit string by changing the reproducing laser power. The horizontal axis is the reproduction laser power, 0.5m
It was measured in the range of W to 3 mW. The vertical axis represents the reproduction signal amplitude, which is normalized by the amplitude when the reproduction laser power is 0.5 mW.

In the figure, the curve marked A is the result of the magneto-optical disk of the present invention, and the curve of B is the result of the conventional magneto-optical disk prepared and measured for comparison. is there. A conventional magneto-optical disk has A1N of 80 nm and DyFeCo of 20 nm on the same glass substrate 1 as described above.
A1N having a thickness of 25 nm and A1Ni having a thickness of 30 nm are laminated in this order, and the same overcoat layer as described above is provided on A1Ni.

The structure of this conventional magneto-optical disk has only one DyFeCo magnetic layer which is a rare earth transition metal alloy, and sandwiches both sides thereof with A1N which is a transparent dielectric layer, and finally, A1Ni which is a reflective film. It is the structure provided. This structure is called a reflection film structure, and is a typical structure of a 3.5-inch size single-plate type magneto-optical disk that has already been commercially available. Also, as is well known, the recording layer made of DyFeCo in the conventional magneto-optical disk has perpendicular magnetization from room temperature to high temperature.

In FIG. 9, the straight line shown by the broken line in the drawing is a straight line connecting the 0 point (origin) and the amplitude standard value at 0.5 mW. It is a straight line showing the relationship with power.

Reproduction signal amplitude ∝ Medium reflected light quantity × polar Kerr rotation angle In this formula, the medium reflected light quantity increases in proportion to the reproduction laser power, and therefore can be replaced with the reproduction laser power.

The measurement result curve (B) of the conventional magneto-optical disk is below this straight line for the following reason.
That is, when the reproducing laser power is increased, the amount of light reflected from the medium increases accordingly, while the temperature of the recording medium rises. The magnetization of a magnetic substance generally has the property of decreasing as the temperature rises and becoming zero at the Curie temperature.
Therefore, in the conventional magneto-optical disk, the polar Kerr rotation angle becomes smaller as the temperature rises, so that the polar Kerr rotation angle does not follow the straight line in the figure and is on the lower side.

On the other hand, in the measurement result curve (A) of the magneto-optical disk of the present invention, the signal amplitude sharply increases as the reproducing laser power increases, and the amplitude becomes maximum at about 2 to 2.25 mW. In addition, except for the value at 3 mW, the values are all above the straight line, and it can be seen that the increase in amplitude over the increase in reproduction laser power is obtained. This result is
This reflects the characteristic of the readout layer 3 of the present invention that there is almost no polar Kerr rotation angle when the temperature is low, and the in-plane magnetization rapidly changes to the perpendicular magnetization as the temperature rises. Is.

Although the above measurement results were obtained for the land portion, when the same measurement was performed for the groove portion, the same result was obtained.

Next, the result of examining the reproduced signal quality when the recording bit is made smaller will be described. The fact that smaller recorded bits can be played means that
This means an increase in recording density.

FIG. 10 is a graph showing the results of measuring the reproduced signal quality (C / N) with respect to the recording bit length.
The linear velocity of the magneto-optical disk was set to 5 m / sec as in the previous experiment, recording was performed by changing the recording frequency, and the C / N
Was measured. The optical pickup and recording method are the same as in the previous experiment.

In the figure, the curve marked A is the measurement result of the magneto-optical disk of the present invention, and the reproducing laser power is 2.25 m.
W. In the figure, the curve marked B is the measurement result of the conventional magneto-optical disk as in the previous experiment, and the reproducing laser power was 1 mW.

At long recording bits with a recording bit length of 0.6 μm or more, there is almost no difference in C / N between the two, but when the recording bit length becomes 0.6 μm or less, the C / N sharply decreases in the conventional magneto-optical disk. Come on. This is because as the recording bit length decreases, the number (area) of recording bits existing in the irradiation diameter of the light beam increases, and it becomes impossible to identify each recording bit.

The cutoff spatial frequency is one of the indices representing the optical resolution of the optical pickup.
It is determined by the wavelength of the laser that is the light source and the numerical aperture of the objective lens. The laser wavelength and the numerical aperture of the objective lens in the optical pickup used in this experiment (780 nm,
0.55) is used to calculate the cutoff frequency, which is converted to the recording bit length, which is 780 nm / (2 * 0.55) /2=0.355 μm. In other words, the optical resolution limit of the optical pickup used in this experiment was 0.355 μm for the recording pit length.
Is. The result of the above conventional magneto-optical disk reflects this, and the C / N at 0.35 μm is almost zero.

On the other hand, in the magneto-optical disk of the present invention, although the C / N decreases as the recording bit length decreases, a C / N close to 30 dB can be obtained even with a recording bit shorter than the optical resolution of 0.355 μm. Has been.

The measurement was performed on both the land and the groove, and the C / N value and tendency were almost the same.

From the above results, it was confirmed that by using the magneto-optical disk of the present invention, recording bits smaller than the optical analysis limit can be reproduced. As a result, it is possible to greatly improve the recording bit density as compared with the conventional magneto-optical disk.

Next, in addition to the present invention confirmed by the above experiment, the result of examining the crosstalk amount which is another important effect will be described.

In a magneto-optical disk, in general, for example, in the case of land specifications, a land is formed as wide as possible and a guide track with a narrow groove is formed, and only the land portion is used for recording and reproduction. Therefore,
The crosstalk in a land-type magneto-optical disk is a leakage from a recording bit written in adjacent lands when reproducing an arbitrary land. The crosstalk in a groove-type magneto-optical disk is a leakage from recording bits written in adjacent grooves when reproducing an arbitrary groove.

For example, according to the IS10089 standard (standard defined for ISO 5.25 rewritable optical disc), 1.6 μ
Shortest recorded bit in m-pitch guide track
The amount of crosstalk with respect to (0.765 μm) is specified to be −26 dB or less.

In this example, the crosstalk amount for a recording bit of 0.765 μm was measured based on the crosstalk measuring method defined in this IS10089 standard. However, in order to confirm the effect of the magneto-optical disk of the present invention, in the above-mentioned glass substrate 1 having a track pitch of 1.6 μm and a land width and a groove width of the same 0.8 μm, when the land portion is reproduced, it is measured from both adjacent grooves. The amount of crosstalk and the amount of crosstalk from both adjacent lands when the groove portion was reproduced were measured.

FIG. 11 shows the measurement result when the land portion is reproduced. The horizontal axis represents the reproduction laser power, and the vertical axis represents the crosstalk amount. In the figure, the curve marked A is the measurement result of the magneto-optical disk of the present invention, and the curve marked B is the measurement result of the above-mentioned conventional magneto-optical disk.

In the conventional magneto-optical disk (B), the crosstalk amount is as large as -15 dB, whereas in the magneto-optical disk (A) of the present invention, it is about -30 dB, which is defined by the above ISO standard. A value of clearing 26 dB was obtained.

Similar results were obtained for crosstalk when reproducing the groove portion.

The reason why such a result is obtained is shown in FIG.
Will be described.

FIG. 12 is a schematic plan view of the magneto-optical disk when viewed from directly above, in which recording bits indicated by circles (dotted lines) in the middle land portion and on both adjacent group portions are recorded. The large circle (solid line) in the figure is the condensed light spot of the reproduction light beam 7, and the servo is applied so that the light spot follows the land. In the figure, the land width and group width are 0.8 μm, and the light spot diameter (light beam diameter) is 1.73 μm (= Airy disk diameter = 1.22 * 7).
80nm / 0.55), the recording bit diameter is 0.335 for convenience of explanation.
The size is shown in μm.

In the figure, the reproduction light beam 7 includes 7
Recording bits are coming in. In the case of conventional magneto-optical disks, each exhibits perpendicular magnetization (for example, the magnetization direction of the recording bit portion is perpendicularly upward to the paper surface, and the magnetization of the (erasure portion) is the same in the area other than the recording bit direction), and As a result, it becomes impossible to separate the respective signals in the light beam. This is the reason why the C / N at 0.35 μm of the conventional magneto-optical disk was small and the crosstalk from the adjacent track was large in the above experimental results.

On the other hand, with the magneto-optical disk of the present invention,
In the region near the center of the reproduction light beam 7 where the temperature is higher than the surroundings, the magnetization of the read layer 3 becomes perpendicular, and in the other regions, the in-plane magnetization remains unchanged. Therefore, even if there are 7 recording bits in the reproduction light beam 7 as shown in the figure, only one located at the center of the reproduction light beam 7 contributes to the reproduction, and is extremely small at 0.335 μm. Even with a very small recorded bit, a C / N of about 30 dB can be obtained. Further, the crosstalk from both adjacent tracks is also very small.

As described above, the readout layer 3 described above is used.
Also, in the magneto-optical disk in which the recording layer 4 is formed on the substrate 1 having a track shape in which the pitch is 1.6 μm and the width ratio of the land and the groove is 1: 1, even if the C / N value is on the land. It was confirmed by an experiment that both of them can be used for recording and reproduction without changing on the groove and that crosstalk is sufficiently small even when information is recorded on the recording layer 4 on the land and the groove.

As a result, the recording density in the longitudinal direction of the track and the track density can be increased, and both the land and the groove are used for recording / reproducing, so that the recording density is greatly increased as compared with the conventional magneto-optical disk. It will be possible.

The composition of GdFeCo of the readout layer 3 is Gd
It is not limited to _0.26 (Fe _0.82 Co _0.18 ) _0.74 . The readout layer 3 has almost in-plane magnetization at room temperature, and the in-plane magnetization may be changed to the perpendicular magnetization at room temperature or higher. In rare earth-transition metal alloys, changing the ratio of rare earth to transition metal changes the compensation temperature at which the magnetizations of the rare earth and transition metal are balanced. Since GdFeCo is a material system that exhibits perpendicular magnetization near this compensation temperature, if the compensation temperature is changed by changing the ratio of Gd and FeCo, the temperature at which in-plane magnetization changes to perpendicular magnetization also changes accordingly.

FIG. 13 shows the results of examining the compensation temperature and Curie temperature when the composition of X, that is, Gd was changed in the system of Gd _X (Fe _0.82 Co _0.18 ) _1-X .

In the composition range in which the compensation temperature is room temperature (25 ° C.) or higher, X is 0.18 or higher, as is apparent from FIG. Of these, the range of 0.19 <X <0.29 is preferable. Within this range, the temperature at which the direction of magnetization shifts from the in-plane direction to the perpendicular direction is in the range of room temperature to 200 ° C. in the actually used configuration in which the recording layer 4 is laminated on the read layer 3. If this temperature is too high, the laser power for reproduction will be as high as the laser power for recording, so that recording may be performed on the recording layer 4 and the recorded information may be disturbed.

Next, in the above GdFeCo system, the characteristics (compensation temperature) when the ratio of Fe and Co was changed, that is, when Y was changed in Gd _X (Fe _{1 -Y} Co _Y ) _{1 -X} . And the change in Curie temperature).

In FIG. 14, when Y is 0, that is, Gd _X
It is a figure which shows the characteristic of Fe1 _-X . In the figure, for example,
When the Gd composition is X = 0.3, the compensation temperature is about 120 ° C and the Curie temperature is about 200 ° C.

In FIG. 15, when Y is 1, that is, Gd _X
It is a figure which shows the characteristic of Co1 _-X . In the figure, for example,
When the Gd composition is X = 0.3, the compensation temperature is about 220 ° C and the Curie temperature is about 400 ° C.

From the above, it can be seen that even if the Gd composition is the same, the compensation temperature and the Curie temperature rise as the Co content increases.

A higher Curie temperature of the read layer 3 is advantageous because a higher C / N can be obtained if the polar Kerr rotation angle during reproduction is as large as possible. However, it should be noted that if the Co content is increased too much, the temperature at which the magnetization direction shifts perpendicularly from the surface also increases.

Considering these points, Gd _x (Fe _{1 -Y} Co _Y )
The value of Y in _1-X is preferably in the range of 0.1 <Y <0.5.

In the read layer 3, the characteristics such as the temperature at which the in-plane magnetization is changed to the perpendicular magnetization are naturally affected by the composition and film thickness of the recording layer 4. this is,
This is because a magnetic exchange coupling force acts between both layers. Therefore, the optimum composition and film thickness of the readout layer 3 vary depending on the material, composition and film thickness of the recording layer 4.

As described above, GdFeCo, which is steep from in-plane magnetization to perpendicular magnetization, is the most suitable material for the read layer 3 of the magneto-optical disk of the present invention. The same effect can be obtained.

Gd _x Fe _1-X has the characteristics shown in FIG. 14, and has a compensation temperature above room temperature in the range of 0.24 <X <0.35.

Gd _x Co _1-X has the characteristics shown in FIG. 15, and has a compensation temperature above room temperature in the range of 0.20 <X <0.35.

When a FeCo alloy is used as the transition metal, Tb _X (Fe _Y Co _1-Y ) _1-X has a compensation temperature at room temperature or higher in the range of 0.20 <X <0.30 (where Y is arbitrary). Have.
Dy _X (Fe _Y Co _1-Y ) _1-X is 0.24 <X <0.33 (At this time,
Y has a compensation temperature at room temperature or higher in any range. Ho _X
(Fe _Y Co _1-Y ) _1-X has a compensation temperature at room temperature or higher in the range of 0.25 <X <0.45 (where Y is arbitrary).

In addition to the above-mentioned materials, when the wavelength of the semiconductor laser which is the light source of the optical pickup becomes shorter than the above-mentioned 780 nm, a material having a large polar Kerr rotation angle at that wavelength can be used as the readout layer of the present invention. It is suitable as the material of No. 3.

As described above, in an optical disk such as a magneto-optical disk, it is the size of the light beam that limits the recording density, which is determined by the laser wavelength and the numerical aperture of the objective lens. Therefore, if a semiconductor laser having a wavelength shorter than that of the present time appears, the recording density of the magneto-optical disk is improved by itself. Now, already 670
Semiconductor lasers with a wavelength of ~ 680 nm are almost at the practical level, and SHG lasers with a wavelength of 400 nm or less are being actively researched.

The polar Kerr rotation angle of a rare earth-transition metal alloy has wavelength dependence, and generally, when the wavelength becomes shorter,
The polar car rotation angle will decrease. If a film with a short wavelength and a large polar Kerr rotation angle is used, the signal strength is increased and a high quality reproduction signal is obtained.

Nd, Pt, Pr, and Pd are used as the material of the read layer 3 described above.
By adding a trace amount of at least one of these elements,
Provided is a magneto-optical disk capable of increasing a polar Kerr rotation angle at a short wavelength with almost no loss of characteristics required for the readout layer 3 and obtaining a high quality reproduction signal even when a short wavelength laser is used. it can.

The read layer 3 to which the above element is added is specifically, for example, Nd _0.05 [Gd _0.26 (Fe
_0.82 Co _0.18 ) _0.74 ] _0.95 , Pt _0.05 [Gd _0.26 (Fe
_0.82 Co _0.18 ) _0.74 ] _0.95 , Pr _0.05 [Gd _0.26 (Fe
_0.82 Co _0.18 ) _0.74 ] _0.95 , Pd _0.05 [Gd _0.26 (Fe
_0.82 Co _0.18 ) _0.74 ] _0.95 .

The material of the readout layer 3 of the above-mentioned magneto-optical disk was changed from Gd _0.26 (Fe _0.82 Co _0.18 ) _0.74 to Nd.
_{When 0.05} [Gd _0.26 (Fe _0.82 Co _0.18 ) _0.74 ] _0.95 was used and the same operation was confirmed as above, almost the same result was obtained.

Further, the environment resistance of the readout layer 3 itself is improved by adding a trace amount of at least one element of Cr, V, Nb, Mn, Be and Ni to the material of the readout layer 3 described above. To do. That is, it is possible to provide a magneto-optical disk excellent in long-term reliability by suppressing deterioration of characteristics due to oxidation of the material of the read layer 3 due to invasion of water and oxygen.

The read layer 3 to which the above element is added is specifically, for example, Cr _0.05 [Gd _0.26 (Fe
_0.82 Co _0.18 ) _0.74 ] _0.95 , V _0.05 [Gd _0.26 (Fe
_0.82 Co _{0. 18) 0.74] 0.95,} Nb _0.05 [Gd _0.26 (Fe
_0.82 Co _{0.18) 0.74] 0.95,} Mn _{0. 05} [Gd _0.26 (Fe
_0.82 Co _0.18 ) _0.74 ] _0.95 , Be _0.05 [Gd _0.26 (Fe
_0.82 Co _0.18 ) _0.74 ] _0.95 , Ni _0.05 [Gd _0.26 (Fe
_0.82 Co _0.18 ) _0.74 ] _0.95 .

Here, an experiment conducted for investigating the effect of increasing the Kerr rotation angle when the above element is added to the material of the readout layer 3 will be described.

The structure of the sample used in the experiment is shown in FIG.

As a sample, a transparent dielectric layer 2 of AlN having a thickness of 80 nm was formed on a glass substrate 1, and a film having a composition of X _0.1 Gd _0.28 (Fe _0.8 Co _0.2 ) _{0.72 0.9} was deposited thereon to a thickness of 50 nm as a readout layer 3. Then, as the recording layer 4, Dy _0.23 Fe _0.82 Co
_0.18 ) _0.77 deposited to 50 nm
It was produced by coating with the protective layer 5 of. Here, X is an additive element and is any of Nd, Pr, Pt, and Pd.

FIG. 31 shows the wavelength dependence of θ _K (Kerr rotation angle) measured from the glass substrate 1 side. As a comparative example,
The results for the sample in which the readout layer 3 does not contain the above additive are also shown in FIG.

In the sample containing no additive, θ _K is large in the long wavelength region but small in the short wavelength region. On the other hand, Nd, P
When r, Pt, and Pd are added, θ _K becomes large in the short wavelength region.

Generally, when the magneto-optical disk is reproduced by using the short wavelength laser, the laser light can be narrowed down as compared with the case where the magneto-optical disk is reproduced by using the long wavelength laser. The recorded bits can be played back. At this time, if the read layer 3 made of a material having a short wavelength and a large θ _K is used, the reproduction signal intensity is increased and a high quality reproduction signal can be obtained.

Therefore, according to the above experimental results, it is effective means to add the above-mentioned additional element to the recording and reproducing using the short wavelength laser. It should be noted that the effect of increasing θ _{K in the} short wavelength region becomes more remarkable as the added amount of the additional element is increased.

With the composition of X _0.1 Gd _0.28 (Fe _0.8 Co _0.2 ) _{0.72 0.9} , the magnitude of θ _{K in} the wavelength range of 600 nm or less is θ _K (P
Add t) ≒ θ _K (Add Nd) ＞ θ _K (Add Pd) ≒
There is a relationship of θ _K (Pr added) (see FIG. 31). Therefore, θ _K can be increased by adding a small amount of Pt and Nd. Furthermore, the addition of Pt has the effect of improving the moisture resistance of the readout layer 3. That is, addition of Pt not only increases θ _K in the short wavelength region, but also has the effect of improving moisture resistance.

Table 1 shows the amount of addition of a material having _a composition of X _a Gd _0.28 (Fe _0.8 Co _0.2 ) _{0.72 1-a} from amorphous to crystalline.

[0153]

[Table 1]

From Table 1, it can be seen that Nd can be added in a larger amount than Pt. That is, when a large amount of Pt is added, the material changes from amorphous to crystalline, which increases noise due to crystal grain boundaries, but even if a large amount of Nd is added, the material remains amorphous. It has a uniform structure. Therefore, it is possible to add a large amount of Nd.

Addition of Pd has the effect of improving the moisture resistance of the readout layer 3, and moreover, the amount of reserves is larger than that of Pt.
It is cheap. Even if Pr is added in a large amount like Nd, the material remains amorphous and a large amount can be added. Moreover, it has the effect of improving the moisture resistance of the readout layer 3 more than Nd.

Next, an experiment carried out for investigating the effect of improving the moisture resistance when the above element is added to the material of the readout layer 3 will be described.

The structure of the sample used in the experiment is shown in FIG.

The sample is a transparent dielectric layer 2 AlN on a glass substrate 1 with a 3.5 inch diameter group.
Of 80 nm is formed, and X _0.1 Gd is formed as the readout layer 3 thereon.
A film having a composition of _0.28 (Fe _0.8 Co _0.2 ) _{0.72 0.9} was deposited to 50 nm,
Next, 50 nm of _{Dy 0.23 Fe 0. 82 Co 0.18)} 0.77 as a recording layer 4
It was prepared by depositing and further coating with a protective layer 5 of AlN of 20 nm and coating with an overcoat layer 6 of 5 μm.

Here, X is an additive element, and Pt, Pd, Nd, P
It is one of r, Ni, Mn, Be, V, Nb, and Cr.

120 samples of the above-mentioned magneto-optical disk were prepared.
The sample was left to stand in a thermostat at 2 ° C. (100% humidity), and the time change of the C / N ratio of the reproduced signal was examined. C when recording / reproducing a recording bit of 0.76 μm length using 780 nm light
FIG. 33 shows the change over time in the / N ratio. The C / N ratio is plotted with an initial value of 0 dB. As a comparative example,
The results for the sample in which the readout layer 3 does not contain the above additive are also shown in FIG.

As is clear from the figure, Cr, V, Nb, Mn, Be, N
When i, Pt and Pd are added, the moisture resistance is improved. The addition of Cr is most effective in improving the moisture resistance.

Table 2 shows the Kerr rotation angle (unit: degree) of the above-mentioned magneto-optical disk sample, which was measured with light having a wavelength of 780 nm. As a comparative example, the Kerr rotation angle of a sample of a magneto-optical disk in which the read layer 3 does not contain an additive is also shown.

[0163]

[Table 2]

As is clear from the table, the addition of Ni has little effect on improving the moisture resistance, but has the effect of increasing the Kerr rotation angle.

Table 3 shows X _a Gd _0.28 (Fe _0.8 Co _0.2 ) _0.72
The addition amount a at which the material having the composition of _1-a changes from amorphous to crystalline is shown.

[0166]

[Table 3]

As is apparent from the table, even if a large amount of V is added, it remains amorphous, noise due to crystal grain boundaries can be suppressed, and moisture resistance can be improved.

Table 4 shows that X _0.05 Gd _0.28 (Fe _0.8 Co _0.2 ) _0.72
The crystallization temperature T _{cr yst} (temperature at which amorphous changes to crystalline, unit: ° C) of a material having a composition of _0.95 is shown.

[0169]

[Table 4]

As is clear from the table, the addition of Nb has the effect of raising the crystallization temperature. Therefore, the deterioration of the readout layer 3 can be suppressed even when the recording and reproduction are repeatedly performed, and moreover, the moisture resistance can be improved. Mn has a large reserve in the soil and is inexpensive.

Table 5 shows the noise level (unit: dB) of the above sample of the magneto-optical disk. As a comparative example,
The noise level of the sample of the magneto-optical disk in which the readout layer 3 does not contain the additive is also shown. The noise level of the sample of the comparative example was set to 0 dB.

[0172]

[Table 5]

Addition of Be and Ni lowers the noise level.
Be added can improve the moisture resistance more than Ni added.

Next, the deterioration of the signal quality when the recording / reproducing was repeatedly performed using the above-mentioned magneto-optical disk sample was examined.

Table 6 shows the C / N ratio (unit: dB) after repeatedly recording and reproducing 1,000,000 times at room temperature. As a comparative example,
The C / N ratio of the sample of the magneto-optical disk in which the readout layer 3 does not contain the additive is also shown. The C / N ratio of the comparative sample was set to 0 dB.

[0176]

[Table 6]

Next, in this embodiment, the read layer 3
Although the film thickness of is set to 50 nm, the film thickness is not limited to this. As shown in FIG. 1, recording and reproducing of information is performed from the side of the read layer 3, but if the film thickness of the read layer 3 is too thin, the information of the recording layer 4 becomes transparent. That is, the masking effect due to the in-plane magnetization of the readout layer 3 is reduced.

As described above, since the magnetic characteristics of the read layer 3 are affected by the recording layer 4, the thickness of the read layer 3 varies depending on each material and composition, but the thickness of the read layer 3 is 20 nm. The above is necessary. Further, the thickness is preferably 50 nm or more, and if it is too thick, information in the recording layer will not be transferred, so a film thickness of about 100 nm or less is preferable.

The thickness of the readout layer 3 is 20 nm and 30 n
Magneto-optical disks (FIG. 1) of m, 40 nm, and 50 nm were prepared, and polar Kerr hysteresis loops at room temperature measured from the substrate 1 side are shown in FIGS. 34 (a) to 34 (d), respectively.

Since the composition of the recording layer 4 is adjusted to a value close to the compensation composition at room temperature, the coercive force of the recording layer 4 at room temperature is very large, but when a sufficiently large magnetic field is applied, the magnetization direction of the recording layer 4 changes. Invert. Therefore, the read layer 3 is the recording layer 4
The magnetization direction of is affected by the exchange coupling force and shows a polar Kerr hysteresis loop as shown in the figure. In all cases, the exchange coupling force works, but when the thickness of the readout layer 3 is thin (FIGS. 34A and 34B), the magnetization of the readout layer 3 is completely recorded when the applied magnetic field is zero. It can be seen that the information in the recording layer 4 is not masked by the read layer 3 in the same direction as the magnetization of the. On the other hand, when the film thickness of the readout layer 3 becomes thicker (FIG. 7C), the mask effect gradually appears, and the thickness of the readout layer 3 becomes 50 nm.
Shows that the information of the recording layer 4 is almost completely masked by the read layer 3.

Next, in order to examine the degree of masking effect when the composition temperature of GdFeCo in the readout layer 3 is changed to change the compensation temperature and the film thickness is also changed, a magneto-optical disk having the structure shown in FIG. 1 is manufactured. Then, the squareness ratio was determined from the polar Kerr hysteresis loop at room temperature measured from the substrate 1 side. Results are shown in FIG. The temperature in the figure indicates the compensation temperature.

The squareness ratio was calculated from the squareness ratio = θ _k ^r (Kerr rotation angle at zero magnetic field) / θ _k ^s (Kerr rotation angle at 15 kOe magnetic field), as shown in FIG. Squareness ratio =
A value of 1 indicates that there is no masking effect, and a squareness ratio of 0 indicates that information is completely masked.

From the figure, it can be seen that the higher the compensation temperature and the thicker the readout layer 3, the greater the masking effect. When the film thickness of the readout layer 3 is 100 nm or less, there is no masking effect when the compensation temperature is 100 ° C. or less. In order to obtain the mask effect, the compensation temperature needs to be 125 ° C. or higher, preferably 150 ° C. or higher. Similarly, it is found that the film thickness of the readout layer 3 must be 10 nm or more in order to obtain the mask effect, and preferably 20 nm or more.

Next, the composition of GdFeCo of the readout layer 3 is changed so that the magnetization of the rare earth sublattice becomes excessive in the temperature range from the room temperature to the Curie temperature, that is, the compensation temperature is changed. In order to investigate the degree of mask effect when changing the film thickness with a composition that does not have
The squareness ratio was calculated. The results are shown in Fig. 37. The temperature in the figure is
The Curie temperature is shown.

From the figure, the higher the Curie temperature is,
It can be seen that the larger the thickness of the readout layer 3, the greater the masking effect. When the film thickness of the readout layer 3 is 100 nm or less, when the Curie temperature is 100 ° C. or less, there is no mask effect. To obtain the mask effect, the Curie temperature is 13
The Curie temperature must be 0 ° C or higher, preferably 200 ° C or higher. Similarly, it is found that the film thickness of the readout layer 3 must be 10 nm or more in order to obtain the mask effect, and preferably 20 nm or more.

In the above, the thickness of the readout layer 3 is 1
The case where the thickness is less than 00 nm has been described.
Even when the film thickness is 200 nm, a good masking effect can be obtained. However, a very large laser power is required to raise the temperature of the read layer 3 and the recording layer 4. Considering the performance of the semiconductor laser, the readout layer 3
The film thickness of is preferably 200 nm or less, more preferably 150 nm or less. Further, the compensation temperature and the Curie temperature of the readout layer 3 are preferably 500 ° C. or lower, more preferably 450 ° C. or lower in view of the performance of the semiconductor laser.

The material of the recording layer 4 is a material exhibiting perpendicular magnetization from room temperature to the Curie temperature, and the Curie temperature may be in a temperature range suitable for recording, that is, about 150 to 250 ° C. Although DyFeCo is used as the recording layer 4 in the above-described embodiment, DyFeCo is a material having a small perpendicular magnetic anisotropy, and therefore recording can be performed even when the external magnetic field required for recording is low. This is a very advantageous point particularly in the magnetic field modulation overwrite recording method described later, and it is possible to reduce the size and power consumption of the recording external magnetic field generator.

Other than DyFeCo, TbFeCo, GdTbFe, NdDyFe
Co, GdDyFeCo and GdTbFeCo are suitable for the recording layer 4. As an example, in Tb _X (Fe _Y Co _1-Y ) _1-X ,
It suffices that 0.10 ≦ X ≦ 0.30 is satisfied for any Y. More specifically, for example, Tb _0.18 (Fe
_0.88 Co _0.12 ) _0.82 .

The material of the recording layer 4 of the above-mentioned magneto-optical disk was changed from Dy _0.23 (Fe _0.78 Co _0.22 ) _0.77 to Tb _0.18 (Fe
_0.88 Co _0.12 ) When _0.82 Co was replaced with _0.82 and the same operation confirmation as above was performed, almost the same result was obtained.

The perpendicular magnetic anisotropy Ku of TbFeCo is
Is as large as about 3 to 4 × 10 ⁶ erg / cc,
It is possible to supply a magneto-optical recording medium in which the reproduced signal quality is very high without breaking the square shape of the Kerr loop at high temperature.

For reference, the above TbFeCo was used as the recording layer 4.
The Kerr loop obtained by the magneto-optical disk used as is shown in FIG. 38 (a), and the perpendicular magnetic anisotropy Ku is about 1 × 10 ^6.
The Kerr loop obtained by the magneto-optical disk using DyFeCo of erg / cc as the recording layer 4 is shown in FIG.
Shown in. The Kerr loop was measured at 180 ° C. from the recording layer 4 side with respect to the substrate 1 of the magneto-optical disk.

While the prismatic shape of DyFeCo is poor, that of TbFeCo has a large perpendicular magnetic anisotropy Ku. Therefore, the recorded bit has a clean edge shape, and the quality of the reproduced signal is high.

Further, as the material of the recording layer 4 described above, Cr, V, N
By adding at least one element of b, Mn, Be, and Ni, the long-term reliability can be improved. The film thickness of the recording layer 4 is determined depending on the material, composition, and film thickness of the readout layer 3, and is preferably 20 nm or more and 100 nm or less.

The film thickness of AlN of the transparent dielectric 2 is not limited to 80 nm.

The film thickness of the transparent dielectric layer 2 takes into consideration the so-called Kerr effect enhancement in which the polar Kerr rotation angle from the read layer 3 is increased by utilizing the light interference effect when reproducing the magneto-optical disk. It is determined. Signal quality during playback
In order to increase (C / N) as much as possible, it is necessary to increase the polar Kerr rotation angle. Therefore, the film thickness of the transparent dielectric layer 2 is set so that the polar Kerr rotation angle becomes the largest. It

This film thickness changes depending on the wavelength of reproducing light and the refractive index of the transparent dielectric layer 2. In the case of this embodiment, 780n
Since AlN having a refractive index of 2.0 is used for the reproduction light wavelength of m, the film thickness of AlN of the transparent dielectric layer 2 is 30 to 120n.
When it is set to about m, the effect of the Kerr effect enhancement becomes large. The thickness of AlN of the transparent dielectric layer 2 is preferably 70 to 100 nm, and the polar Kerr rotation angle is almost maximum in this range.

Although the above description is for the reproduction light of wavelength 780 nm, for example, for the reproduction light of wavelength 400 nm, which is half the wavelength, the film thickness of the transparent dielectric layer 2 may be almost halved. .

Further, when the refractive index of the transparent dielectric layer 2 changes due to the difference in the material of the transparent dielectric layer 2 or the manufacturing method, the value obtained by multiplying the refractive index and the film thickness (optical path length) becomes the same. The thickness of the transparent dielectric layer 2 may be set.

That is, in the present embodiment, the refractive index 2 of AlN of the transparent dielectric layer 2 and the film thickness of 80 nm are multiplied by 160.
nm is the optical path length of the transparent dielectric layer 2, but when the refractive index of this AlN changes from 2 to 2.5, 160 nm / 2.5 = 6
The film thickness should be set to about 4 nm.

As can be seen from the above description, the larger the refractive index of the transparent dielectric layer 2, the smaller the film thickness.
Also, the greater the refractive index, the greater the enhancement effect of the polar Kerr rotation angle.

AlN is changed by changing the ratio of Ar and N ₂ which are sputter gases at the time of sputtering and the gas pressure.
Although the refractive index changes, it is a material having a relatively large refractive index of about 1.8 to 2.1 and is suitable as a material for the transparent dielectric layer 2.

In addition to the Kerr effect enhancement described above, the transparent dielectric layer 2 has a role of preventing oxidation of the rare earth-transition metal alloy magnetic layers of the read layer 3 and the recording layer 4 together with the protective layer 5.

A magnetic film made of a rare earth transition metal is very likely to be oxidized, and particularly rare earth is easily oxidized. For this reason, if the invasion of oxygen and moisture from the outside is not prevented as much as possible, the characteristics will be significantly deteriorated by oxidation.

Therefore, in this embodiment, the read layer 3 and the recording layer 4 are sandwiched on both sides by AlN. AlN is a nitride film that does not contain oxygen as its component, and is a material having extremely excellent moisture resistance.

Further, AlN has a relatively large refractive index of about 2 and is transparent, and does not contain oxygen in its component, so that a magneto-optical disk excellent in long-term stability can be provided. In addition, using A1 target, N ₂ gas or
It is possible to perform reactive DC (direct current) sputtering by introducing a mixed gas of Ar and N ₂ , and RF (high frequency)
It is also advantageous in that the film formation speed is higher than that of the sputter.

As the transparent dielectric layer 2 other than AlN, SiN, AlSiN, AlTaN, which has a relatively large refractive index,
SiAlON, TiN, TiON, BN, ZnS, Ti
O ₂ , BaTiO ₃ , SrTiO _{3 and the} like are suitable. Of these, especially SiN, AlSiN, AlTiN, TiN,
BN and ZnS do not contain oxygen as a component, and can provide a magneto-optical disk having excellent moisture resistance.

SiN, AlSiN, AlTaN, SiA
lON, TiN, TiON, BN, ZnS, TiO ₂ ,
BaTiO ₃ and SrTiO ₃ are formed by sputtering. AlSiN, AlTaN, TiN, TiO
₂ is also advantageous in that reactive DC sputtering can be performed and the film formation rate is higher than in RF (high frequency) sputtering. In addition, SiN, AlSiN,
The refractive index of AlTaN, BN, and SiAlON is 1.8 to
2.1, the refractive index of TiN is 2-2.4, ZnS, Ti
The refractive index of ON is 2 to 2.5, TiO ₂ , and BaTi.
The refractive indexes of O ₃ and SrTiO ₃ are 2.2 to 2.8, and these refractive indexes change depending on the sputtering conditions.

Since SiN and AlSiN have relatively small thermal conductivity, they are suitable for a high recording sensitivity magneto-optical disk.
Since AlTaN and TiN contain Ta and Ti, respectively, a magneto-optical disk excellent in corrosion resistance (pitting corrosion resistance) can be obtained. Since BN is extremely hard and resistant to abrasion, it is possible to obtain a magneto-optical disk which prevents scratches and has excellent long-term stability. The targets of ZnS, SiAlON, and TiON are inexpensive. TiO ₂ , BaTiO ₃ , SrTiO
No. ₃ has a very high refractive index, so that a magneto-optical disk having excellent reproduction signal quality can be obtained.

When the material of the transparent dielectric layer 2 of the above magneto-optical disk was changed from AlN to SiN and the same operation was confirmed as above, almost the same result was obtained.

The film thickness of AlN of the protective layer 5 in this embodiment is
Although it is set to 20 nm, it is not limited to this. The thickness of the protective layer 5 is preferably 1 to 200 nm.

In this embodiment, the total thickness of the magnetic layers of the read layer 3 and the recording layer 4 is 100 nm, and at this thickness, the light incident from the optical pickup hardly passes through the magnetic layer. Therefore, the film thickness of the protective layer 5 is not particularly limited as long as it is necessary to prevent oxidation of the magnetic layer for a long period of time. If the material has a low antioxidation ability, the film thickness may be increased, and if it is high, the film thickness may be decreased.

The thermal conductivity of the protective layer 5 together with the transparent dielectric layer 2 affects the recording sensitivity characteristics of the magneto-optical disk. The recording sensitivity characteristic means how much laser power is required for recording or erasing. Most of the light incident on the magneto-optical disk is a transparent dielectric layer.
It passes through 2 and is absorbed by the reading layer 3 and the recording layer 4 which are absorption films, and is converted into heat. At this time, the heat of the read layer 3 and the recording layer 4 is transferred to the transparent dielectric layer 2 and the protective layer 5 by heat conduction. Therefore, the thermal conductivity and heat capacity (specific heat) of the transparent dielectric layer 2 and the protective layer 5 affect the recording sensitivity.

This means that the recording sensitivity of the magneto-optical disk can be controlled to some extent by the film thickness of the protective layer 5. For example, for the purpose of increasing the recording sensitivity (record erasing can be performed with low laser power). The protective layer 5 may be thinned. Usually, in order to extend the life of the laser, it is advantageous that the recording sensitivity is high to some extent, and the thickness of the protective layer 5 is preferably thin.

AlN is also suitable in this sense and has excellent moisture resistance. Therefore, when it is used as the protective layer 5, the film thickness can be reduced and a magneto-optical disk having high recording sensitivity can be provided.

In this embodiment, the protective layer 5 is replaced by the transparent derivative layer 2
By using the same AlN as described above, a magneto-optical disk having excellent moisture resistance can be provided, and by forming the protective layer 5 and the transparent derivative layer 2 from the same material, productivity can be improved. As described above, AlN is a material having extremely excellent moisture resistance, so that it can be set to a relatively thin film thickness of 20 nm. Even if productivity is taken into consideration, the thinner one is more advantageous. Further, as the material of the protective layer 5, other than AlN,
Considering the above-mentioned objects and effects, the above-mentioned transparent dielectric layer 2
Used as material for SiN, AlSiN, AlT
aN, SiAlON, TiN, TiON, BN, Zn
S, TiO ₂ , BaTiO ₃ , and SrTiO ₃ are suitable.

Further, if the same material as the transparent dielectric layer 2 is used, it is also advantageous in terms of productivity.

Of these, particularly SiN, AlSiN, Al
TaN, TiN, BN, and ZnS do not contain oxygen as a component, and can provide a magneto-optical disk having excellent moisture resistance.

As the material of the substrate 1, in addition to the above-mentioned glass, chemically strengthened glass, a so-called 2P-layered glass substrate having a UV-curable resin layer formed on these glass substrates, polycarbonate (PC), poly It is possible to use the substrate 1 made of methyl methacrylate (PMMA), amorphous polyolefin (APO), polystyrene (PS), polychlorinated biphenyl (PVC), epoxy, or the like.

When the chemically strengthened glass is used for the substrate 1, it has excellent mechanical properties (in the case of a magneto-optical disk, surface wobbling, eccentricity, warpage, inclination, etc.), a large hardness,
Hard to be scratched by sand and dust, chemically stable so it does not dissolve in various solvents, less likely to be charged as compared to plastic, so dust and dirt do not adhere, and chemically strengthened so it is hard to break In addition, since it has excellent moisture resistance, oxidation resistance, and heat resistance, long-term reliability of the magneto-optical recording medium is improved, optical characteristics are excellent, and high signal quality can be obtained. .

When the above-mentioned glass or chemically strengthened glass is used as the substrate 1, a guide track for guiding a light beam and unevenness called pre-pits formed in advance on the substrate to obtain information such as an address signal. As a method of forming a signal on a substrate, the surface of these glass substrates is formed by reactive dry etching. Also, 2
There is a method of irradiating an ultraviolet curable resin called a P layer to cure the resin, and then peeling off the stamper to form the guide track, prepits, and the like on the resin layer.

When a PC is adopted as the substrate 1, injection molding is possible, so that the same substrate 1 can be supplied in a large amount at a low cost, and the water absorption rate is lower than other plastics.
Improved long-term reliability of magneto-optical recording media, heat resistance,
The advantage is that it has excellent impact resistance. For materials that can be injection-molded as described below, including this material, guide tracks, pre-pits, etc. can be formed on the surface of the substrate 1 simultaneously with molding if a stamper is attached to the surface of the molding die during injection molding. To be done.

When PMMA is used for the substrate 1, injection molding can be performed, so that the same substrate 1 can be supplied in a large amount at a low cost, and since the birefringence is smaller than other plastics, it has excellent optical characteristics. The advantages include high signal quality and excellent durability.

When APO is used for the substrate 1, injection molding is possible, so that a large amount of the same substrate 1 can be supplied at low cost, and the water absorption rate is lower than other plastics.
The advantages are that the long-term reliability of the magneto-optical recording medium is improved, the birefringence is small, the optical characteristics are excellent, the high signal quality is obtained, and the heat resistance and the impact resistance are excellent. To be

When PS is used for the substrate 1, injection molding is possible, so that the same substrate 1 can be supplied in large quantities at low cost, and since the water absorption rate is lower than other plastics, long-term reliability of the magneto-optical recording medium is obtained. The advantage is that the property is improved.

When PVC is used for the substrate 1, injection molding can be performed, so that the same substrate 1 can be supplied in a large amount at low cost, and the water absorption rate is lower than that of other plastics.
The advantages are that the long-term reliability of the magneto-optical recording medium is improved and that it is flame-retardant.

When epoxy is used for the substrate 1, the water absorption is lower than that of other plastics, so that the long-term reliability of the magneto-optical recording medium is improved, and the thermosetting resin is excellent in heat resistance. The advantage is that it is excellent.

As described above, it is possible to use various materials as the substrate 1, but when these materials are used as the substrate 1 of the magneto-optical disk, the following optical characteristics and mechanical characteristics are satisfied. Is desirable.

Refractive index: 1.44 to 1.62 Birefringence: 100 nm or less (reciprocal birefringence measured by parallel light) Transmittance: 90% or more Thickness variation: ± 0.1 mm Tilt: 10 mrad or less Surface runout acceleration : 10 m / s ² or less Radial acceleration: 3 m / s ² or less The optical pickup for focusing the laser light on the recording layer 4 is designed according to the refractive index of the substrate 1, and thus the substrate 1
If the variation in the refractive index of the laser becomes large, the laser light cannot be collected sufficiently. When the focused state of the laser light changes, the temperature distribution of the recording medium (that is, the read layer 3 and the recording layer 4) changes, which affects recording and reproduction. In the present invention, the temperature distribution of the recording medium during reproduction becomes particularly important, so it is desirable to suppress the refractive index of the substrate 1 used within the range of 1.44 to 1.62.

Further, since the laser light is made incident through the substrate 1, if the substrate 1 has birefringence, the polarization state of the laser light changes when passing through the substrate 1.
Since the present invention reproduces the change in the magnetization state of the readout layer 3 as the change in the polarization state by using the Kerr effect, if the polarization state changes when passing through the substrate 1, the reproduction cannot be performed. Therefore, it is desirable that the reciprocal birefringence of the substrate 1 when measured with parallel light is 100 nm or less.

Further, when the transmittance of the substrate 1 becomes low, the amount of light when the light beam from the optical pickup passes through the substrate 1 at the time of recording, for example, decreases. Therefore, in order to obtain the amount of light required for recording on the recording medium, a laser light source with higher output is required. Particularly in the present invention, the recording medium is a recording layer 4 and a reading layer 3
In order to raise the temperature of the recording medium as compared with the conventional single-layer (without the reading layer 3) recording medium,
Since a larger amount of light is required, the transmittance of the substrate 1 is 9
It is preferably 0% or more.

Further, since the optical pickup for focusing the laser light on the recording medium is designed according to the thickness of the substrate 1, the laser light is sufficiently focused when the thickness of the substrate 1 varies greatly. Can not do. When the focused state of the laser light changes, the temperature distribution of the recording medium changes, which adversely affects recording and reproduction. In the present invention, the temperature distribution of the recording medium during reproduction is particularly important, so it is desirable to suppress the thickness variation of the substrate 1 used within ± 0.1 mm.

If the substrate 1 is tilted, the laser light from the optical pickup will be focused on the tilted recording medium surface, and the focused state will change depending on the tilted state. As in the case where the thickness of the substrate 1 changes, recording and reproduction are adversely affected. Therefore, in the present invention, the tilt of the substrate 1 is preferably 10 mrad or less, more preferably 5 mrad or less.

When the substrate 1 moves vertically with respect to the optical pickup, the optical pickup operates to compensate the vertical movement of the substrate and focus the laser light on the surface of the recording medium, but if the vertical movement becomes too large. The compensation operation of the optical pickup becomes incomplete, and the condensed state of the laser light on the surface of the recording medium becomes incomplete. If the focused state of the laser light is incomplete, the temperature distribution of the recording medium changes, which adversely affects recording and reproduction. In the present invention, since the temperature distribution of the recording medium during reproduction becomes particularly important, it is desirable to suppress the surface wobbling acceleration to 10 m / s ² or less when the substrate used is moved up and down during rotation.

In addition, the substrate 1 is preliminarily 1.0-1.
Although guide tracks for guiding the light beam are provided at a pitch of 6 μm, if the guide tracks have an eccentricity, the guide tracks move in the radial direction with respect to the optical pickup during rotation. At this time, the optical pickup collects the laser light in order to compensate the movement in the radial direction and maintain a constant relationship with the guide track, but if the movement of the guide track in the radial direction becomes too large, the compensating operation of the optical pickup will occur. It becomes incomplete, and it becomes impossible to focus the laser beam in a state where the guide track is kept in a constant relationship. In the present invention, the temperature distribution of the recording medium during reproduction is particularly important. Therefore, with respect to the radial movement of the substrate used during rotation, the radial acceleration should be suppressed to 3 m / s ² or less. Is desirable.

As a method of guiding the condensed laser light to a predetermined position of the magneto-optical disk, spiral or
A continuous servo method using a concentric guide track and a sample servo method using a spiral or concentric pit row can be considered.

In the case of the continuous servo system, as shown in FIG. 16, the pitch is 1.2 to 1.6 μm and the pitch is 0.2 to 0.6 μm.
Width groups are formed with a depth of about λ / (8n),
Information is generally recorded and reproduced at the land portion. This is called a land specification magneto-optical disk. Where λ is the wavelength of the laser beam and n is the refractive index of the substrate used.

It is sufficiently possible to apply the present invention to such a general system. In the present invention, the crosstalk due to the recording bits of the adjacent tracks is significantly reduced.
Even when a group having a width of 0.4 μm is formed, recording / reproduction can be performed without being affected by crosstalk from adjacent recording bits, and the recording density is significantly improved.

Further, as shown in FIG. 17, 0.8-1.
Forming groups and lands of the same width at a pitch of 6 μm,
Even when recording / reproducing is performed on both the group portion and the land portion, recording / reproducing can be performed on both the group portion and the land portion without being affected by crosstalk from the recording bits of adjacent tracks. The density is greatly improved.

On the other hand, in the case of the sample servo system, FIG.
As shown in FIG. 8, wobble pits are formed with a pitch of 1.2 to 1.6 μm with a depth of about (λ / (4n)), and information is recorded so that the laser beam always scans the center of the wobble pits. Regeneration is generally performed.
It is quite possible to apply the present invention to such a general system. In the present invention, by significantly reducing the crosstalk from the adjacent recording bits,
Even when the wobble pits are formed with a pitch of 0.5 to 1.2 μm, recording and reproduction can be performed without being affected by crosstalk from adjacent recording bits.
Recording density is greatly improved.

Further, as shown in FIG.
When wobble pits are formed at a pitch of 1.6 μm and information is recorded / reproduced at positions where the wobble pits have opposite polarities, recording / reproduction can be performed without being affected by crosstalk from adjacent recording bits. It becomes possible and the recording density is greatly improved.

Further, as shown in FIG. 20, in the continuous servo system, when the position information of the magneto-optical disk is obtained by wobbling the groove, the wobbling state exists in the adjacent groove in the opposite phase portion. Although there has been a problem that crosstalk from recording bits becomes large, by applying the present invention, crosstalk from recording bits existing in an adjacent groove may occur even in a portion where the wobbling state has an opposite phase. Therefore, it is possible to perform good recording and reproduction.

The magneto-optical disk of this embodiment is also suitable for various recording / reproducing optical pickups as described below.

For example, when a multi-beam type optical pickup using a plurality of light beams is adopted, as shown in FIG. 21, the light beams at both ends of the plurality of light beams are positioned so as to scan the guide track. A general method is to perform recording / reproduction with a plurality of light beams positioned between them. By using the magneto-optical head disk of the present invention, crosstalk from adjacent recording bits can be achieved even if the light beam interval is narrowed. It is possible to reproduce without being affected by the above, and it is possible to shorten the pitch of the guide tracks, or it is possible to record and reproduce with more laser beams between a pair of guide tracks. The density is greatly improved.

In the above description, the numerical aperture (NA) of the objective lens of the optical pickup used has a general value of 0.4 to 0.6, and the wavelength of the laser light is The guide track pitch and the like are discussed as being 670 nm to 840 nm. A. Is further increased to 0.6 to 0.95, the laser beam is further narrowed down, and by applying the magneto-optical disk of the present invention, the pitch and width of the guide track can be further narrowed. High-density recording / reproducing is possible.

Further, by using an argon laser beam having a wavelength of 480 nm or a laser beam having a wavelength of 335 nm to 600 nm using an SHG element, the laser beam is further narrowed down, and by applying the present invention, the pitch of the guide track can be reduced. Also, the width can be further narrowed, and recording and reproduction with higher density can be performed.

Regarding a / w, 0.3 to 1.0 can be used. Where a is the optically effective diameter of the lens,
w is the diameter of the light beam entering the lens, and is the radius of 1 / e ² of the central intensity when the Gaussian distribution is used.

Next, the disk format applied to the magneto-optical disk of this embodiment will be described.

Generally, in a magneto-optical disk, recording is performed at each radial position in order to maintain compatibility between different manufacturers or different magneto-optical disks.
What value or duty the erasing power is set to is recorded in advance in a part of the inner and outer peripheries with a prepit row having a depth of about (λ / (4n)). Also,
Based on those read values, a test area that can be used for actual recording and playback is provided inside and outside (for example, IS1008
9 See standard).

On the other hand, regarding the reproduction power, information for setting a specific reproduction power is recorded in advance in a part of the inner and outer circumferences in a prepit row.

In the magneto-optical disk of the present invention, the temperature distribution of the recording medium at the time of reproduction has a great influence on the reproduction characteristics, so that the method of setting the reproduction power is very important.

As a reproducing power setting method, for example, with respect to the reproducing power as well as the recording power, a test area for setting the reproducing power is provided on the inner and outer circumferences, and each radial position is determined from the reproducing power obtained in the test area. It is desirable to previously record information for optimizing the reproduction power in the pit row in a part of the inner and outer circumferences.

In particular, in a magneto-optical disk drive using the CAV system in which the number of revolutions of the magneto-optical disk is always constant, the linear velocity of the magneto-optical disk changes depending on the radial position. Therefore, the reproducing laser power depends on the radial position. It is more preferable to change Therefore, it is better to record information divided into as many radial areas as possible as a prepit row.

Similarly, as a method of setting a more optimum reproducing laser power at each radial position, the recording area is divided into a plurality of zones according to the radial position, and the recording power is set for each zone at the boundary between the zones. Also, by optimizing the reproduction power in the test area, the temperature distribution of the recording medium during reproduction can be controlled more accurately, and good recording / reproduction can be performed.

Next, the point that the magneto-optical disk of this embodiment is applicable to various recording methods described below will be described.

First, the recording method of the first generation magneto-optical disk which cannot be overwritten will be described.

The first-generation magneto-optical disk is IS10089.
In accordance with the standard (standard of ISO 5.25 "rewritable optical disc), many are already on the market,
Since overwriting cannot be performed, when newly recording information at a place where information has already been recorded, it is necessary to perform an operation of once erasing that portion and then recording. Therefore, it is necessary to rotate the magneto-optical disk at least twice, and there is a defect that the data transfer rate is slow.

However, there is an advantage that the performance required for the magnetic film is not so high as compared with the overwritable magneto-optical disk described below.

In order to eliminate the drawback that overwriting cannot be performed, a method of arranging a plurality of optical heads to eliminate the loss of waiting for rotation and to improve the data transfer rate is adopted in some devices.

For example, it is a method of using two optical heads to erase the information already recorded by the preceding optical head and record new information by the optical head chasing after. When reproducing, either one of the optical heads is used for reproduction.

When recording is performed using three optical heads, the preceding optical head erases the already recorded information, the next optical head records new information, and the remaining optical heads perform verification. (Check that the new information is recorded correctly).

Instead of using a plurality of optical heads, one optical head may be used to form a plurality of beams by using a beam splitter, and this may be used in the same manner as the plurality of optical heads.

As a result, new information can be recorded without passing through the process of erasing the already recorded information.
Pseudo overwrite can be realized using the next generation magneto-optical disk.

The magneto-optical disk of this example has been confirmed to be capable of recording, reproducing and erasing, as already described in the explanation of the experimental results, and is a magneto-optical disk applicable to this recording system. .

Next, the magnetic field modulation overwrite recording method will be described.

The magnetic field modulation overwrite recording method is a method in which the magneto-optical recording medium is irradiated with a laser having a constant power and the magnetic field intensity is modulated in accordance with the information for recording, which will be described with reference to FIG. For example,

FIG. 22 is a schematic diagram showing an example of a magneto-optical disk device for performing magnetic field modulation overwriting on a magneto-optical disk. A laser light source (not shown) for irradiating a laser beam at the time of recording and reproducing, and recording. And an optical head 11 incorporating a light receiving element (not shown) for receiving the reflected light from the magneto-optical disk during reproduction, and a floating magnetic head 12 mechanically or electrically connected to the optical head 11. I have it.

The flying magnetic head 12 is the flying slider 1
2a and a magnetic head 12b in which a coil is wound around a core made of MnZn ferrite or the like.
It is pressed by 4 and is levitated with a constant gap of about several μm to several tens of μm.

In this state, the floating magnetic head 12 and the optical head 11 are moved to a desired radial position in the recording area of the magneto-optical disk 14, and the recording layer of the magneto-optical disk 14 is moved from the optical head 11 to about 2 to 10 mW. Laser light is focused and irradiated to raise the temperature of the recording layer 4 to near the Curie temperature (or the temperature at which the coercive force becomes almost “0”), and then, upward or downward depending on the information to be recorded. A magnetic field to be reversed is applied by the magnetic head 12b. As a result, information can be recorded by the overwrite recording method without passing through the process of erasing the already recorded information.

In this embodiment, the laser power was kept constant at the time of magnetic field modulation overwriting. However, when the polarity of the magnetic field was switched, the laser power was lowered to the unrecorded power so that recording would not be performed. The recorded bit shape becomes clearer and the reproduction signal quality is improved.

In the magnetic field modulation overwrite, in order to perform high-speed recording, it is necessary to modulate the magnetic field at high speed, but there is a restriction in terms of power consumption and size of the magnetic head 12b, and a very large magnetic field is required. Is difficult to generate. Therefore, the magneto-optical disk 14 is required to be able to record with a relatively small magnetic field.

In the magneto-optical disk of this embodiment, the Curie temperature of the recording layer 4 is kept relatively low at 150 to 250 ° C. to facilitate recording, and DyFeCo, which is a material having small perpendicular magnetic anisotropy, is adopted. By doing so, the magnetic field at the time of recording can be suppressed to a lower level, and the configuration is very suitable for the magnetic field modulation overwrite method.

Next, the optical modulation overwrite recording method will be described.

The optical modulation overwrite recording method is completely opposite to the magnetic field modulation overwrite recording method, in which a constant magnetic field strength is applied to the magneto-optical recording medium and the laser power is modulated according to the information for recording. Is the way. This will be described below with reference to FIGS. 23 to 27.

FIG. 24 shows the temperature dependence of the coercive force in the direction perpendicular to the film surfaces of the read layer 3 and the recording layer 4 and the recording magnetic field H, which are suitable for the light modulation overwrite recording method described below.
_{Shows W.}

Recording is performed by applying a recording magnetic field H _W and irradiating laser light whose intensity is modulated into two levels, high and low. That is, as shown in FIG. 25, when the high-level I laser beam is irradiated, both the reading layer 3 and the recording layer 4 are heated to a temperature T _H near or above the Curie points T _C1 , T _C2. When the laser light of low level II is irradiated, only the recording layer 4 is set to be heated up to the temperature T _L which becomes the Curie point T _C2 or more.

Therefore, when the low-level II laser beam is irradiated, the coercive force H ₁ of the read layer 3 is sufficiently small, and the magnetization is transferred to the recording layer 4 in the cooling process according to the direction of the recording magnetic field H _W. To be done. That is, as shown in FIG. 23, the magnetization is upward. Next, when the laser light of high level I is irradiated, since the compensation temperature is exceeded, the magnetization direction of the read layer 3 is changed to a low level by the recording magnetic field H _W.
The direction is opposite to the case of the laser light of II, that is, the direction is downward. In the cooling process, the temperature drops to the same temperature as that of the low-level II laser beam, but since the cooling process of the read layer 3 and the recording layer 4 is different (the recording layer 4 is cooled faster), only the recording layer 4 is at the low level The temperature _TL at which the laser light of II was irradiated
Then, the magnetization direction of the read layer 3 is transferred to the recording layer 4 and becomes downward. After that, the readout layer 3 is at the low level II.
The temperature drops to the same temperature as that of the laser light of, and becomes upward according to the direction of the recording magnetic field H _W. At this time, since the magnetization direction of the recording layer 4 has its coercive force H ₂ sufficiently larger than the recording magnetic field H _W, it does not follow the direction of the recording magnetic field H _W has.

During reproduction, when the laser light of level III in FIG. 25 is irradiated, the temperature of the read layer 3 becomes T _R (FIG. 24), and the magnetization of the read layer 3 is perpendicular to the in-plane magnetization. The recording layer 4 and the read layer 3 are switched to the magnetization.
Both layers exhibit perpendicular magnetic anisotropy. At this time, the recording magnetic field H
_{Since W} is not applied or is sufficiently smaller than the coercive force H ₂ of the recording layer 4 even if applied, the direction of magnetization of the read layer 3 during reproduction is changed by the exchange force acting on the interface with the recording layer 4. Match the orientation of.

As a result, information can be recorded by the overwrite recording method without passing through the process of erasing the already recorded information.

The recording may be performed by applying the modulated two types of laser light as shown in FIG. 26 or 27 while applying the recording magnetic field H _W.

That is, when the type I high-level laser beam is irradiated, the temperature T at which the reading layer 3 and the recording layer 4 both reach the Curie points T _C1 , T _C2 or higher.
_{When the} temperature is raised to _H and the low-level type II laser beam is irradiated, only the recording layer 4 is set to the temperature T _L at which the Curie point T _C2 or higher is reached. By doing so, the cooling process of the read layer 3 and the recording layer 4 can be greatly different particularly when irradiated with a high level type I laser beam. That is, the recording layer 4 is cooled faster. Therefore, overwriting can be performed more easily.

However, the intensity of the laser light that is irradiated for a while after being irradiated with the high level laser light of type I may be equal to or lower than the high level.

According to the above recording method, there is an advantage that it is not necessary to apply an initialization magnetic field, which is generally required at the time of optical modulation overwrite.

The magneto-optical disk (FIG. 1) is generally called a single-sided type. In this magneto-optical disk, when the thin film portions of the transparent dielectric layer 2, the read layer 3, the recording layer 4, and the protective layer 5 are collectively referred to as a recording medium layer, as shown in FIG. 28, the substrate 1 and the recording medium layer are shown. 9. The structure of the overcoat layer 6 is obtained.

On the other hand, as shown in FIG. 29, two pieces of the recording medium layer 9 formed on the substrate 1 are bonded by the adhesive layer 10 so that the recording medium layers 9 and 9 face each other. The magnetic disk is called a double-sided type.

The material of the adhesive layer 10 is particularly preferably a polyurethane acrylate adhesive. This adhesive is a combination of three types of curing functions of ultraviolet rays, heat and anaerobic, and the curing of the shadowed portion of the recording medium layer 9 where ultraviolet rays do not pass is cured by the heat and anaerobic curing functions. Thus, it is possible to provide a double-sided magneto-optical disk having extremely high humidity resistance and extremely excellent long-term stability.

Since the single-sided type requires only half the thickness of the magneto-optical disk as compared with the double-sided type, it is advantageous for a recording / reproducing apparatus which requires miniaturization.

Since the double-sided type is capable of double-sided reproduction, it is advantageous for a recording / reproducing apparatus which requires a large capacity, for example.

Whether to adopt the single-sided type or the double-sided type depends largely on the recording system as described below, in addition to considering the thickness and capacity of the magneto-optical disk as described above.

As is well known, a light beam and a magnetic field are used for recording information on the magneto-optical disk. As shown in FIG. 22, in the magneto-optical disk device, a light beam from a light source such as a semiconductor laser is focused by the condenser lens 8 through the substrate 1 onto the recording medium layer 9 and irradiated, and the position facing the position is confronted. A magnetic field is applied to the recording medium layer 9 by a magnetic field generating device (for example, a floating magnetic head 12) such as a magnet or an electromagnet provided in the recording medium layer 9. By making the light beam intensity higher during recording than during reproduction, the temperature of the recording medium layer 9 at the focused portion rises, and the coercive force of the magnetic film at that portion decreases. At this time, if a magnetic field having a magnitude larger than the coercive force is applied from the outside, the magnetization of the magnetic film follows the direction of the applied magnetic field and the recording is completed.

For example, in the magnetic field modulation overwrite method for modulating the recording magnetic field according to information, it is necessary to bring the magnetic field generator (mostly an electromagnet) as close to the recording medium layer 9 as possible. This is modulated by the frequency required for recording (generally several hundred kHz to several tens MHz) due to heat generation of the coil of the electromagnet, device power consumption, size, etc., and the magnetic field required for recording (generally 500e to several hundreds of Oe), the recording medium is about 0.2 mm or less, and in most cases 50 μ.
It is necessary to bring them closer to about m. Therefore, in the double-sided type magneto-optical disk, the thickness of the substrate 1 is generally 1.2.
Since it is about mm and needs to be about 0.5 mm even if it is thin, when the electromagnet is arranged so as to face the light beam, the recording magnetic field strength becomes insufficient and recording cannot be performed. Therefore, when the recording medium layer 9 suitable for the recording modulation overwrite system is adopted, a single-sided type magneto-optical disk is often used.

On the other hand, in the optical modulation overwrite method in which the light beam is modulated according to information, the recording magnetic field remains in one direction, or the recording magnetic field is unnecessary. Therefore, it is possible to use, for example, a permanent magnet having a strong generated magnetic field, and to dispose the recording medium layer 9 at a distance of about several mm without arranging the permanent magnet as close as possible to the recording medium layer 9 as in the magnetic field modulation overwrite method. it can. Therefore, not only the single-sided type but also the double-sided type can be adopted.

When the magneto-optical disk of this embodiment is used as a single-sided disk, there are structural variations that can be explained below.

The first variation is a magneto-optical disk in which a hard coat layer (not shown) is formed on the overcoat layer 6, which is substrate 1 / recording medium layer 9 / overcoat layer 6 / hard coat layer. It has a structure.
The hard coat layer is, for example, an acrylate-based UV-curable hard coat resin film, and is made of, for example, a polyurethane acrylate-based UV-curable resin and has a film thickness of about 6 μm.
Is formed on the overcoat layer 6. The film thickness of the hard coat layer is, for example, 3 μm.

By forming the overcoat layer 6, it is possible to prevent characteristic deterioration due to oxidation of the recording medium layer 9 and ensure long-term reliability. In addition to this, by providing a hard coat film, even if a recording magnet comes into contact with the disc, for example, the hard coat film with high hardness and excellent abrasion resistance makes it difficult to scratch. Further, even if a scratch is generated, it can be prevented from reaching the recording medium layer 9.

Further, as a matter of course, the function of the hard coat layer may be added to the overcoat layer 6, and only the overcoat layer 6 may be used.

In the second variation, a hard coat layer is formed on the overcoat layer 6, and a hard coat layer (not shown) is formed on the surface of the substrate 1 opposite to the recording medium layer 9. A magnetic disk, hard coat layer / substrate 1 / recording medium layer 9 / overcoat layer 6 /
It has a hard coat layer structure.

As the material of the substrate 1 for the magneto-optical disk,
Many plastics such as PC are used,
These materials are much softer than glass and can be scratched just by rubbing them with your nails. In the worst case, when the recording / reproducing is performed with a light beam, this flaw may cause servo skipping, which makes it impossible to record / reproduce information.

In the magneto-optical disk of the present embodiment, since reproduction is performed only in the vicinity of the center of the light beam, the influence of defects such as scratches on the surface of the substrate 1 on the reproduction is greater than that in the conventional magneto-optical disk. It gets bigger. For this reason, by providing the hard coat layer on the surface of the substrate 1 opposite to the recording medium layer 9, the present structure capable of preventing the occurrence of scratches is very effective.

Also in the double-sided type, it is clear that the same effect can be obtained by providing a hard coat layer on the surface of each substrate 1.1 of the magneto-optical disk.

The third variation is the above first and second variations.
On the overcoat layer 6 of the variation of
It is a magneto-optical disk in which an antistatic coating layer (not shown) or a layer having an antistatic function is further formed on the hard coat layer.

If the surface of the substrate 1 is dusty or dusty, it may be impossible to record / reproduce information like scratches. Further, if dust is attached to the overcoat film 6, in the case of the magnetic field modulation overwriting method, the magnet is used as the floating magnetic head 12 (FIG. 22), and the overcoat film 6 is covered by several μm.
In the case of arranging with the gap, the dust and the dust cause damage to the floating magnetic head 12 and the recording medium layer 9.

With this structure, if a layer having an antistatic function is provided on the surface of the substrate 1 side or the surface of the recording medium layer 9 side, dust, dust, etc. in the air or the surface of the substrate 1 Adhesion on the overcoat layer 6 can be prevented.

In the magneto-optical disk of the present embodiment, since reproduction is performed using only the vicinity of the center of the light beam, the influence of defects such as dust and dust on the surface of the substrate 1 on reproduction is affected by the conventional magneto-optical disk. Since this is larger than the above, this configuration is extremely effective.

As the antistatic layer, for example, an acrylic hard coat resin mixed with a conductive filler can be used, and its film thickness is preferably about 2 to 3 μm.

The antistatic layer is provided for the purpose of lowering the surface resistivity and making dust and dirt less likely to occur, regardless of whether it is the plastic substrate 1 or the glass substrate 1.

Naturally, an antistatic effect may be added to the overcoat layer 6 or the hard coat layer.

Also, in the double-sided type, it is obvious that this structure can be applied to the surface of each substrate 1.1 of the magneto-optical disk.

The fourth variation is a magneto-optical disk in which a lubricating layer (not shown) is formed on the overcoat layer 6, and has a structure of substrate 1 / recording medium layer 9 / overcoat layer 6 / lubrication layer. Have As a lubricating layer,
For example, a fluorine-based resin can be used, and a film thickness of about 2 is suitable.

By providing the lubricating layer, when the floating magnetic head 12 is used in the magnetic field modulation overwrite method, the lubricity between the floating magnetic head 12 and the magneto-optical disk can be improved.

That is, the floating magnetic head 12 is arranged for recording information on the recording medium layer 9 while maintaining a gap of several μm to several tens μm. The floating magnetic head 12 is generated by the pressing force of the suspension 13 that works to press the layer 9 and the air flow generated by the high-speed rotation of the magneto-optical disk.
Is balanced from the recording medium layer 9 so that the gap is maintained.

By using the floating magnetic head 12 as described above, the floating of the magneto-optical disk is started at the start of rotation, until the rotation speed reaches the predetermined rotation speed, and at the end of the rotation until the rotation stops from the predetermined rotation speed. When the CSS (Contact-Start-Stop) method in which the magnetic head 12 and the magneto-optical disk are in contact is adopted, if the floating magnetic head 12 and the magneto-optical disk are attracted to each other, the magneto-optical disk is floated at the start of rotation. The magnetic head 12 may be damaged. However,
According to the magneto-optical disk of the present embodiment, since the lubricating film is provided on the overcoat layer 6, the lubricity between the floating magnetic head 12 and the magneto-optical disk is improved, and the floating magnetic head 12 due to the attraction. Can be prevented from being damaged.

Naturally, it is not necessary to separately provide the overcoat layer 6 and the lubrication layer as long as they are materials which prevent the deterioration of the recording medium layer 9 and also have a moisture resistance protection performance.

In the fifth variation, a moisture permeation preventive layer (not shown) and a second overcoat layer (not shown) are laminated on the surface of the substrate 1 opposite to the recording medium layer 9. It is a magneto-optical disk and has a structure of overcoat layer / moisture permeation preventive layer / substrate / recording medium layer 9 / overcoat layer 6.

For the moisture permeation preventive layer, for example, A1N, A1SiN, Si
A transparent dielectric material such as N, A1TaN, SiO, ZnS, and TiO ₂ can be used, and its film thickness is preferably about 5 nm. The second overcoat layer is particularly effective when a highly hygroscopic plastic such as PC is used as the substrate 1 for the substrate 1.

The moisture permeation preventive layer has an effect of suppressing a change in warp of the magneto-optical disk with respect to a change in environmental humidity. This will be described below.

If this moisture permeation preventive film is not provided on the light incident side of the substrate 1, for example, when the environmental humidity changes greatly, only the side where the recording medium layer 9 is absent, that is, the incident light side of the substrate 1 is a plastic substrate. Water is absorbed or released in 1). Due to this moisture absorption and moisture release, a local volume change occurs in the plastic substrate 1 and the plastic substrate 1 is warped.

The warp of the magneto-optical disk is caused by the substrate 1 with respect to the optical axis of the light beam used for reproducing and recording information.
Is tilted, the servo is deviated, the signal quality is deteriorated, and in severe cases, servo skipping occurs.

When the substrate 1 has a tilt, the laser light from the optical head 11 (FIG. 22) is focused on the inclined surface of the recording medium layer 9, and the laser light is focused according to the tilt state. The state will change, which adversely affects recording and reproduction.

Further, when the substrate 1 moves up and down with respect to the optical head 11, the optical head 11 operates so as to compensate for the up and down movement and focus the laser beam on the surface of the recording medium layer 9, but the up and down movement. Is too large, the compensation operation of the optical head 11 becomes incomplete, and the condensing state of the laser light on the surface of the recording medium layer 9 becomes incomplete. If the focused state of the laser light is incomplete, the temperature distribution of the recording medium layer 9 changes, which affects recording / reproduction. In this embodiment, the temperature distribution of the recording medium layer 9 at the time of reproduction is particularly important, so that it is necessary to suppress the warp of the substrate 1 and the warp change due to the environment as much as possible.

In the magneto-optical disk of this structure, the moisture permeation preventive layer prevents moisture absorption and release of moisture on the surface side of the substrate 1, so that the warp of the substrate 1 when the environment changes can be suppressed significantly. Therefore, as described above, the structure is particularly suitable for the magneto-optical disk of the present invention.

The second overcoat layer on the moisture permeation preventive layer is provided for the purpose of preventing damage to the moisture permeation preventive layer, protecting the surface of the substrate 1, and the like. Medium layer 9
It may be the same as the overcoat layer 6 above.

Further, in addition to this structure, the above-mentioned hard coat layer or antistatic layer may be provided instead of or on the second overcoat layer.

In the above embodiments, the substrate 1 has a pitch of 1.
Although a groove having a thickness of 6 μm was formed, it was confirmed that a recording / reproducing characteristic with no practical problems can be obtained even if the groove has a thickness of 1.2 μm.

Therefore, for example, the laser wavelength is 78
Using a short wavelength laser shorter than 0 nm, N. A. If the spot diameter of the reproduction light beam 7 is reduced by using the condensing lens 8 having a value of 0.55 or more, a groove with a pitch of 1.2 μm or less (for example, a pitch of 0.8 μm) is not a practical problem It is possible to record and replay without.

In terms of manufacturing, it is necessary to consider an error of at least ± 0.05 μm in the width of the land and the width of the groove.

The ratio of the land width to the groove width is
It is preferable to set the C / N on the land and the C / N on the groove to be substantially the same. Therefore, the ratio may be slightly deviated from 1: 1 in consideration of the depth of the groove.

In the magneto-optical disk device for recording / reproducing with one light beam, it is necessary to switch the polarity of the tracking servo in order to switch the tracking servo from the track on the land to the track on the groove.

As a recording method, first, recording is performed on tracks on lands, and after recording is performed on tracks on all lands, the polarities of the tracking servo are switched and recording is performed on tracks on the grooves. Also, the track is divided into logical areas in the radial direction of the magneto-optical disk,
First, recording is performed on tracks on a land of a logical division area, and after recording on tracks on all lands of the logical division area, recording is performed on tracks on grooves of the logical division area. If so, the access speed is improved.

In a magneto-optical disk device that uses two or more light beams and applies tracking servo to each track on the land and the track on the groove, it is not necessary to switch the polarities of the tracking servo. Moreover, high-speed data transfer becomes possible. It is necessary to separate a plurality of light beams to some extent so that the shape of the recording bit is not disturbed by thermal interference during recording.

The second embodiment of the present invention will be described below with reference to FIG. For convenience of explanation, members having the same functions as those of the members shown in the drawings of the above-described embodiments are designated by the same reference numerals, and the description thereof will be omitted.

In the magneto-optical disk of this example, as shown in FIG. 39, a substrate 1, a transparent dielectric layer 2, a reading layer 3, a recording layer 4, a heat dissipation layer 20, and an overcoat layer 6 were laminated in this order. Have a configuration.

For the heat dissipation layer 20, for example, Al can be used, and its film thickness is appropriately about 100 nm. Board 1,
For the transparent dielectric layer 2, the readout layer 3, the recording layer 4, and the overcoat layer 6, the same materials as those in the above-mentioned embodiment can be used.

Since the heat dissipation layer 20 is provided on the recording layer 4, it has an effect of making the recording bit shape sharper at the time of recording. This is for the following reason.

Most of the light beam incident from the incident surface side is absorbed by the reading layer 3 and the recording layer 4 and converted into heat. At this time, heat is conducted not only in the thickness direction of the read layer 3 and the recording layer 4 but also in the layer, that is, in the lateral direction. When the amount of heat conduction in the lateral direction is large and the speed of heat conduction is slow, for example, when recording is performed at higher speed and higher recording density, heat is applied to the recording bit to be recorded next. Have a negative impact. For this reason, the recording bit becomes longer than the predetermined length, or the recording bit spreading in the lateral direction with respect to the guide track is formed. If the recording bits spread in the horizontal direction, the amount of crosstalk increases, and good recording and reproduction cannot be performed.

In this embodiment, since the heat dissipation layer 20 made of Al having high heat conductivity is formed on the recording layer 4, it is necessary to allow the heat spread in the lateral direction to escape to the heat dissipation layer 20 side, that is, the thickness direction. It is possible to reduce the spread of heat in the lateral direction as described above. Therefore, it becomes possible to perform recording without thermal interference under a recording condition of higher density and higher speed.

Further, the provision of the heat dissipation layer 20 is advantageous also in the light modulation overwrite recording as described below.

Due to the presence of the heat dissipation layer 20, when a region whose temperature has been once raised by irradiation with a light beam is cooled in the course of recording, there is a clearer difference in temperature change between the read layer 3 and the recording layer 4. Can have This effect can greatly differ the cooling process of the read layer 3 and the recording layer 4 when irradiated with a high level laser light (the recording layer 4 is cooled faster).
Overwriting can be performed more easily.

Al, which is the material of the heat dissipation layer 20, has a higher thermal conductivity than the rare earth transition metal alloy films used for the read layer 3 and the recording layer 4, and is a material suitable for the heat dissipation layer 20. In addition, when AlN is used for the transparent dielectric layer 2, this AlN is formed by reactively sputtering an Al target with Ar and N ₂ gas. Therefore, the same Al target is sputtered with Ar gas to release heat. The layer 20 can be easily formed. Al is also a very inexpensive material.

The material of the heat dissipation layer 20 is not limited to Al, but Au, A
Any material such as g, Cu, SUS, Ta, Cr or the like having a higher thermal conductivity than the read layer 3 and the recording layer 4 may be used.

When Au, Ag, and Cu are used for the heat dissipation layer, they are excellent in oxidation resistance, moisture resistance, and pitting corrosion resistance, so that long-term reliability is improved.

When SUS, Ta, or Cr is used for the heat dissipation layer, oxidation resistance, moisture resistance, and pitting corrosion resistance are extremely excellent, so that long-term reliability is improved.

In this embodiment, the thickness of the heat dissipation layer 20 is 10
Although the thickness is set to 0 nm, the larger the thickness, the higher the heat dissipation effect, and the long-term reliability also improves. However, as described above, it also affects the recording sensitivity of the magneto-optical disk, so it is necessary to set the film thickness according to the thermal conductivity and specific heat of the material, and the range of 5 to 200 nm is preferable. Above all, 10-100 nm
Is preferred. If the material has relatively high thermal conductivity and excellent corrosion resistance, the film thickness can be as thin as about 10 to 100 nm, and the time required for film formation during manufacturing can be shortened.

Also, a dielectric layer (not shown) may be inserted between the recording layer 4 and the heat dissipation layer 20. The same material as the transparent dielectric layer 2 may be used for the dielectric layer,
The materials described in the first embodiment such as A1N, SiN and A1SiN can be used. In particular, A1N, SiN, A1SiN, TiN, A1TaN, ZnS, BN
If a nitride film containing no oxygen is used for the above components, it is possible to provide a magneto-optical disk having excellent long-term reliability. The thickness of the dielectric layer is preferably 10-100 nm.

The third embodiment of the present invention will be described below with reference to FIG. For convenience of explanation, members having the same functions as those of the members shown in the drawings of the above-described embodiments are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 40, the magneto-optical disk of this example has a substrate 1, a transparent dielectric layer 2, a read layer 3, a recording layer 4, a transparent dielectric layer 21, a reflective layer 22, and an overcoat layer 6. Are laminated in this order.

For the transparent dielectric layer 21, for example, AlN can be used, and its film thickness is appropriately about 30 nm. For the reflective layer 22, for example, Al can be used, and its film thickness is appropriately about 30 nm. For the substrate 1, the transparent dielectric layer 2, the readout layer 3, the recording layer 4, and the overcoat layer 6, the same materials as those in the above-mentioned embodiment can be used. However, the thickness of the readout layer 3 is 15 nm, which is half the thickness of the first embodiment, and the thickness of the recording layer 4 is 15 nm, which is half the thickness of the first embodiment. I have to.

That is, in the magneto-optical disk of this embodiment, part of the incident light beam is transmitted through the read layer 3 and the recording layer 4, through the transparent dielectric layer 21, and reflected by the reflective layer 22. It is supposed to be done.

As a result, the light reflected on the surface of the read layer 3 interferes with the light reflected by the reflective layer 22 and transmitted through the recording layer 4 and the read layer 3 again, and the magneto-optical effect is enhanced to enhance the polar curve. The rotation angle increases. Therefore, the information can be reproduced with higher accuracy, and the quality of the reproduced signal is improved.

In this structure, in order to enhance the enhancing effect, the thickness of the transparent dielectric layer 2 is optimally 70 to 100 nm, and at this time, the thickness of the transparent dielectric layer 21 is preferably 15 to 50 nm. Is.

The reason why the film thickness of the transparent dielectric layer 2 may be set to 70 to 100 nm is that the enhancement effect of the polar Kerr rotation angle becomes the largest as already described in the first embodiment.

Regarding the film thickness of the transparent dielectric layer 21, the thicker the film thickness, the larger the polar Kerr rotation angle but the smaller the reflectance. If the reflectance is too small, the signal for applying servo to the guide track becomes small, and stable servo cannot be applied. For this reason,
The thickness of the transparent dielectric layer 21 is preferably about 15 to 50 nm.

Further, if the refractive index of the transparent dielectric layer 21 is made larger than that of the transparent dielectric layer 2, the enhancement effect can be further enhanced.

Further, since the readout layer 3 and the recording layer 4 are both layers made of a rare earth transition metal alloy and having a high light absorptivity, almost no light is transmitted when the total thickness thereof is 50 nm or more. , The enhancement effect cannot be obtained. Therefore, the total thickness of these two layers is preferably 10 to 50 nm.

If the thickness of the reflection layer 22 is too thin, light is transmitted through the reflection layer 22 and the enhancement effect is deteriorated. Therefore, at least about 20 nm is necessary. On the other hand, if the thickness is too large, the laser power required for recording, reproduction, etc. will be high, and the recording sensitivity of the magneto-optical disk will be lowered, so about 100 nm or less is preferable. Therefore, the preferable film thickness of the reflective layer 22 is in the range of 20 to 100 nm.

The reason why Al is used as the material of the reflective layer 22 is that the reflectance is as large as about 80% in the wavelength range of the semiconductor laser and that it is common with AlN of the transparent dielectric layer 2 when formed by sputtering. It is possible to use an Al target. As mentioned above, Al
When N is deposited, reactive sputtering is performed using a mixed gas of Ar and N ₂ or N ₂ gas to form A of the reflective layer 22.
When depositing No. 1, Ar gas is introduced and sputtering is performed.

Reflective layers other than A1 include Au, Pt,
Any material such as Co, Ni, Ag, Cu, SUS, Ta, Cr having a reflectance of 50% or more at the wavelength of the light beam may be used.

When Au, Pt, Cu or Co is used for the reflective layer 22, it is excellent in oxidation resistance, moisture resistance and pitting corrosion resistance, so that long-term reliability is improved.

When Ni is used for the reflective layer 22, since the thermal conductivity is small, the magneto-optical disk has high recording sensitivity,
It has excellent oxidation resistance, moisture resistance, and pitting corrosion resistance, improving long-term reliability.

When Ag is used for the reflective layer 22, it is excellent in oxidation resistance, moisture resistance and pitting corrosion resistance, so that long-term reliability is improved. Moreover, the Ag target is inexpensive.

When SUS, Ta, or Cr is used for the reflective layer 22, since it is extremely excellent in oxidation resistance, moisture resistance and pitting corrosion resistance, it is possible to provide a magneto-optical disk having excellent long-term reliability. .

The fourth embodiment of the present invention will be described below with reference to FIGS. 41 and 42. For convenience of explanation, members having the same functions as those of the members shown in the drawings of the above-described embodiments are designated by the same reference numerals, and the description thereof will be omitted.

In the magneto-optical disk of this example, as shown in FIG. 41, a substrate 1, a transparent dielectric layer 2, a reading layer 3, a recording layer 4, a protective layer 5, and an overcoat layer 6 were laminated in this order. Have a configuration. Although the structure is similar to that of the magneto-optical disk of the first embodiment, the magnetic characteristics of the read layer 3 are different as described in detail below.

The readout layer 3 is made of a rare earth-transition metal alloy and is a ferrimagnetic material in which the sublattice magnetic moment of the rare earth metal and the sublattice magnetic moment of the transition metal are directed in opposite directions. The temperature characteristics of these sublattice magnetic moments are different from each other, and the magnetic moment of the transition metal becomes relatively larger than that of the rare earth metal at high temperature.

At room temperature, the readout layer 3 has a rare earth metal content higher than that of the compensating composition so as to be in-plane magnetized at room temperature. When the light beam is irradiated, the temperature of that portion rises and the sublattice magnetic moment of the transition metal relatively increases. Therefore, the magnetization as a whole becomes small and the magnetization becomes perpendicular.

That is, as shown in the temperature characteristic of the coercive force in FIG. 42, the readout layer 3 is in the in-plane magnetization state in which the magnetization is oriented in the in-plane direction at room temperature (T _ROOM ), and the temperature is not less than T _P1. The magnetization becomes a perpendicular magnetization state in which the magnetization is oriented in the direction perpendicular to the film surface, and the film becomes a perpendicular magnetization film at the read temperature (T _READ ).

Therefore, the readout layer 3 of this embodiment has an RE-rich composition in which the content of rare earth metal is larger than that of the compensation composition at room temperature. Furthermore, the readout layer 3 must always have a RE-rich composition from room temperature to the Curie temperature. Here, RE-rich means a composition having a higher content of rare earth metal than the compensating composition, and TM-rich, which will be described later, means a composition having a higher content of transition metal than the compensating composition.

The recording layer 4 is made of a rare earth-transition metal alloy composed of a perpendicularly magnetized film, and has a coercive force H in order to stably store information recorded as a magnetization direction at room temperature.
_C2 (see Figure 42) must be high enough. Considering disturbance such as an external magnetic field, a coercive force of about 100 kA / m is sufficient, but a coercive force of 400 kA / m or more is desirable if possible.

Next, the light modulation overwrite in the above magneto-optical disk will be described.

When the temperature of the recording layer 4 rises to near the Curie temperature T _C2 at which recording is performed by irradiation with the light beam, the magnetization direction of the recording layer 4 is aligned with the direction of the recording magnetic field. It is determined by the balance between the magnetostatic coupling force and the exchange coupling force that tries to align the directions of the sublattice magnetic moments of the read layer 3 and the recording layer 4. for that reason,
In the vicinity of the Curie temperature T _{C2 at which} recording is performed, the directions of the magnetostatic coupling force and the exchange coupling force exerted on the recording layer 4 need to be opposite. That is, in the vicinity of the Curie temperature T _C2 of the recording layer 4, the read layer 3 is RE-rich, so the recording layer 4 needs to be TM-rich.

When the temperature of the recording layer 4 rises to near its Curie temperature T _C2 (T _{L in} FIG. 42) by irradiating the magneto-optical disk with a light beam of a relatively low first power, the recording layer 4 The magnetization of the read layer 3 is oriented in the direction of the recording magnetic field, because the magnetization of is very small or disappears. In addition, the temperature of the readout layer 3 on the light incident side is set to the recording layer 4
Of the reading layer 3 and the recording layer 4 such that T ₁₁ (the average temperature of the reading layer 3)> T ₂₂ (the average temperature of the recording layer 4) is satisfied. If the exchange coupling force exerted on the recording layer 4 from the read layer 3 is compared with the magnetostatic coupling force exerted on the recording layer 4 by the recording magnetic field, the static magnetic force exerted on the recording layer 4 by the recording magnetic field is set. The magnetic coupling force becomes relatively strong. As a result, the magnetization direction of the recording layer 4 can be oriented in the direction determined by the magnetostatic coupling force exerted on the recording layer 4 by the recording magnetic field.

Next, when the temperature of the recording layer 4 rises above its Curie temperature T _C2 (T _{H in} FIG. 42) by irradiating the magneto-optical disk with a light beam of a relatively high second power, Although the temperature rises through the same process, the temperature difference in the film thickness direction is eliminated during the temperature decrease process, and at the time when the temperature drops to near the Curie temperature of the recording layer 4, T
It is possible to realize the state of ₁₁ = T ₂₂ . At this time,
Since the magnetization of the recording layer 4 becomes very small or disappears, the magnetization direction of the read layer 3 is oriented in the direction of the recording magnetic field.

In this case, the exchange coupling force exerted on the recording layer 4 from the read layer 3 becomes relatively stronger than in the case where the light beam of the relatively low first power is irradiated. As a result, the magnetization direction of the recording layer 4 can be oriented in the direction determined by the exchange coupling force from the read layer 3.

In this way, the magnetization direction of the recording layer 4 is changed depending on whether the light beam having a relatively low first power is applied or the light beam having a relatively high second power is applied. It becomes possible. That is, light modulation overwriting becomes possible.

When reading the recorded magnetization direction of the recording layer 4, a light beam having a power lower than the first power is irradiated. Since the intensity of the irradiated light beam generally has a Gaussian distribution, the temperature distribution of the readout layer 3 also has a Gaussian distribution. Therefore, it is possible to set the readout layer 3 only in the central portion smaller than the light beam diameter to the perpendicular magnetization state.

The magnetization direction of the read layer 3 is determined by exchange coupling with the recording layer 4 so that the directions of the sublattice magnetic moments of the read layer 3 and the recording layer 4 are aligned. Therefore, it is possible to read out the magnetization direction of the recording layer 4 only in a range smaller than the diameter of the light beam in the central portion of the light beam.

When the recording layer 4 is RE-rich near the Curie temperature T _C2 , optical modulation overwrite cannot be performed, but information recorded by a recording method such as magnetic field modulation overwrite cannot be read. It is possible.

In the above, the readout layer 3 is at room temperature (T
_ROOM ) is an in-plane magnetization state in which the magnetization is oriented in the in-plane direction, and it is necessary to become a perpendicular magnetization state in which the magnetization is oriented in the direction perpendicular to the film surface at a temperature of T _P1 or higher as the temperature rises. It is necessary to form a perpendicular magnetization film at the reading temperature (T _READ ). However, since the reproduction output at the time of reading depends on the inclination of the magnetization of the reading layer 3, the reading layer 3 does not need to have a perfect in-plane magnetization state at room temperature and a perfect perpendicular magnetization state at a reading temperature.

That is, at room temperature and readout temperature,
If the state of the magnetization gradient of the read layer 3 is different, the effect of reading the magnetization direction of the recording layer 4 only in the range smaller than the light beam diameter of the central portion of the light beam can be obtained at the time of reading.

Next, a concrete example of the above-mentioned magneto-optical disk, a manufacturing method thereof, an optical modulation overwrite using the magneto-optical disk and a reproduction test thereof will be described.

5 consisting of A1, Gd, Dy, Fe and Co
A polycarbonate substrate 1 having pregrooves and prepits is placed facing the target in a sputtering apparatus equipped with an original target, and the inside of the sputtering apparatus is evacuated to 1 × 10 ^-6 Torr, and then argon and nitrogen are used. Is introduced, and power is supplied to the target of A1 to form a transparent dielectric layer 2 of A1N having a thickness of 80 nm at a gas pressure of 4 × 10 ⁻³ Torr and a sputtering rate of 12 nm / min. Formed.

Next, after evacuating to 1 × 10 ^-6 Torr again, argon gas was introduced and power was supplied to the targets of Gd, Fe and Co to supply gas pressure of 4 × 10 ^-3 Torr.
GdFeCo at a sputter rate of 15 nm / min
A readout layer 3 having a thickness of 50 nm was formed. The readout layer 3 is RE rich, has no compensation temperature,
The Curie temperature T _C1 was 300 ° C. GdFeC
The composition of o was Gd _0.26 (Fe _0.82 Co _0.18 ) _0.74 .

Next, the power supplied to Gd is stopped,
DyFe is similarly supplied by supplying power to the Dy target.
A recording layer 4 made of Co and having a thickness of 50 nm was formed. The recording layer 4 is TM rich at room temperature and has a coercive force H _C2 of 80
The Curie temperature T _C2 was set to 150 ° C., assuming that 0 kA / m and no compensation temperature existed. The composition of DyFeCo was Dy _0.23 (Fe _0.82 Co _0.18 ) _0.77 .

Next, a mixed gas of argon and nitrogen was introduced, and electric power was supplied to the target of A1 so that the gas pressure was 4 × 1.
The protective layer 5 made of A1N and having a film thickness of 20 nm was formed at a gas pressure of 0 ⁻³ Torr and a sputtering rate of 12 nm / min. The thickness of the protective layer 5 may be determined so that the read layer 3 and the recording layer 4 can be protected from corrosion such as oxidation.

Next, an ultraviolet curable resin was applied by spin coating and irradiated with ultraviolet rays to form the overcoat layer 6.

Although the thicknesses of the read layer 3 and the recording layer 4 are set to 50 nm, respectively, the read layer 3 and the recording layer 4 are formed.
It was possible to more effectively use the temperature difference in the film thickness direction by setting the thickness to 100 nm.

The above-mentioned magneto-optical disk was attached to the magneto-optical disk device and rotated so that the linear velocity of the magneto-optical disk became 10 m / s at the laser beam irradiation position.
With a recording magnetic field of 25 kA / m applied, the first laser power was set to 6 mW and the second laser power was set to 10 m.
When mW was used and recording was performed by modulating the laser power at a frequency of 5 MHz, it was recorded on the recording layer 4 at a period of 2 μm.
It was possible to form inverted magnetic domains with a length of μm.

When information was reproduced with a laser power of 2 mW, a magneto-optical signal of 5 MHz could be obtained from the read layer 3 in accordance with the inverted magnetic domain formed in the read layer 3.

Next, when the laser power was modulated at a frequency of 10 MHz and overwriting was performed on the inverted magnetic domain formed at 5 MHz, the inverted magnetic domain formed at 5 MHz disappeared, and the recording layer 4 remained. , 1 μm newly
It was possible to form an inverted magnetic domain having a length of 0.5 μm in a cycle.

When information was reproduced again with the laser power set to 2 mW, only the magneto-optical signal of 10 MHz having the same magnitude as the magneto-optical signal of 5 MHz was reproduced according to the reversed magnetic domain formed in the recording layer 4. It could be obtained from the readout layer 3. This means that in the readout layer 3,
This means that the magnetization state of the read layer 3 is reproduced only in the portion where the temperature rises to the perpendicular magnetization state.

The fifth embodiment of the present invention will be described below with reference to FIG. For convenience of explanation, members having the same functions as those of the members shown in the drawings of the above-described embodiments are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 43, the magneto-optical disk of this example has a substrate 1, a transparent dielectric layer 2, a readout layer 3, an intermediate layer 29 composed of an in-plane magnetized film, a recording layer 4, a protective film 5, and The overcoat layer 6 has a structure laminated in this order. That is, the magneto-optical disk of the fourth embodiment has a structure in which the intermediate layer 29 made of an in-plane magnetized film is provided between the read layer 3 and the recording layer 4.

The light modulation overwrite and reproduction are performed in the same manner as in the fourth embodiment, but the exchange coupling force between the read layer 3 and the recording layer 4 is provided by providing the intermediate layer 29 made of an in-plane magnetized film. It becomes possible to control, and the degree of freedom of the film design is improved.

The intermediate layer 29 may always be in-plane magnetized up to the Curie temperature of the intermediate layer 29. However, when the intermediate layer 29 reaches the Curie temperature or higher, the exchange coupling between the read layer 3 and the recording layer 4 is released. Therefore, in order to realize more reliable optical modulation overwrite, the intermediate layer 29
It is desirable that the Curie temperature is approximately the same as the Curie temperature T _C2 of the recording layer 4, that is, 150 to 250 ° C.

For the intermediate layer 29, specifically, for example, Dy
An in-plane magnetized film made of FeCo is used. DyFeC
Other than o, TbFeCo, GdTbFe, NdDyF
eCo is preferred. In addition, Cr, V,
The long-term reliability can be improved by adding at least one kind of element among Nb, Mn, Be and Ni. The film thickness of the intermediate layer 29 is determined in consideration of the material, composition, and film thickness of the readout layer 3, but 1 to 50 nm is suitable. Middle layer 2
9 is continuously formed in the same sputtering apparatus together with the read layer 3 and the recording layer 4.

With the same sputtering apparatus as in the above embodiment, D
A magneto-optical disk provided with an intermediate layer 29 made of yFeCo was prototyped. Other than that, the configuration is the same as that of the above-mentioned embodiment. The Curie temperature of the intermediate layer 29 is the same as that of the recording layer 4 15
It was set to 0 ° C.

When this magneto-optical disk was attached to a magneto-optical disk apparatus and the same recording / reproducing test as that in the above-mentioned example was conducted, good overwrite characteristics and reproducing characteristics were obtained. However, in this embodiment, the intermediate layer 9 controls the exchange coupling between the read layer 3 and the recording layer 4, and the exchange coupling force is weakened. Therefore, the optimum magnitude of the recording magnetic field is
Unlike the above example, it was 22 kA / m.

Sixth Embodiment of the Present Invention FIGS. 44 to 46
The explanation is based on the following. For convenience of explanation, members having the same functions as those of the members shown in the drawings of the above-described embodiments are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 44, the magneto-optical disk of this example has a substrate 1, a transparent dielectric layer 2, a readout layer 3, an intermediate layer 30 made of a nonmagnetic film, a recording layer 4, a protective film 5, and an overcoat. The coat layer 6 has a structure laminated in this order.

During recording, if the intermediate layer 30 made of a non-magnetic film does not exist, a strong exchange coupling force is exerted from the reading layer 3 to the recording layer 4 and the recording characteristics are deteriorated. Therefore, by providing the intermediate layer 30 made of the non-magnetic film of the present embodiment and releasing the exchange coupling, stable recording becomes possible.

As the intermediate layer 30, specifically, for example,
AlN with a thickness of 5 nm is used. Since the intermediate layer 30 is formed so that the exchange coupling between the recording layer 4 and the reading layer 3 does not work, AlN may be formed as a monolayer or more between the recording layer 4 and the reading layer 3. If the intermediate layer 30 becomes too thick, the magnetic field generated from the recording layer 4 for aligning the magnetization of the read layer 3 becomes weak. Therefore, the thickness of the intermediate layer 30 is preferably 50 nm or less.

In the magneto-optical disk of this embodiment, specifically, the substrate 1 has a diameter of 86 mm, an inner diameter of 15 mm and a thickness of 1.2 mm.
It is made of disc-shaped glass. Although not shown in the drawings, a concave-convex guide track for guiding the light beam has a pitch of 1.6 μm, a groove (concave) width of 0.8 μm, and a land (convex) on one surface of the substrate 1. Width 0.8μ
It is formed by m. That is, the width of the groove and the width of the land are formed to be 1: 1.

On the surface of the substrate 1 on which the guide track is formed, A1N having a thickness of 80 n is formed as the transparent dielectric layer 2.
It is formed by m.

On the transparent dielectric layer 2, a rare earth-transition metal alloy thin film GdFeCo having a thickness of 50 nm is formed as the readout layer 3. The composition of GdFeCo is
_{Gd 0. 26 (Fe 0.82 Co 0.18} ) _0.74, the Curie temperature is about 300 ° C..

Due to the combination of the read layer 3 and the recording layer 4, the magnetization direction of the read layer 3 is substantially in-plane (that is, the layer direction of the read layer 3) at room temperature, and 100
The temperature shifts from the in-plane direction to the vertical direction at a temperature of about 125 ° C.

On the read layer 3, as the intermediate layer 30, A
1N is formed with a thickness of 5 nm.

On the intermediate layer 30, as a recording layer 4, a rare earth-transition metal alloy thin film, DyFeCo, having a thickness of 50 nm was used.
Is formed by. The composition of DyFeCo is Dy
_0.23 (Fe _0.78 Co _0.22 ) _0.77 , and its Curie temperature is about 200 ° C.

On the recording layer 4, as a protective layer 5, A1N
Are formed with a thickness of 20 nm.

On the protective layer 5, as the overcoat layer 6, a polyurethane acrylate-based ultraviolet curable resin is formed with a thickness of 5 μm.

In this magneto-optical disk, an intermediate layer 30 is provided between the read layer 3 and the recording layer 4 of the magneto-optical disk shown as a specific example in the first embodiment.
When the same operation as that of the example was confirmed, almost the same result was obtained.

As the material of the intermediate layer 30 other than AlN,
SiN, AlSiN, AlTaN, SiAlON, Ti
N, TiON, BN, ZnS, TiO ₂ , BaTi
Dielectric materials such as O ₃ and SrTiO ₃ can be used.

Al, Si, Ta, Ti, Cu, A
A non-magnetic metal material such as u, Ag or Pt, or an alloy material thereof can be used.

As a variation of the above magneto-optical disk, as shown in FIG. 45, the substrate 1, the transparent dielectric layer 2,
There is a magneto-optical disk in which a reading layer 3, an intermediate layer 30 made of a nonmagnetic film, a recording layer 4, a heat dissipation layer 20, and an overcoat layer 6 are laminated in this order. The heat dissipation layer 20 is as described in detail in the first embodiment.

As another variation of the above magneto-optical disk, as shown in FIG. 46, the substrate 1, the transparent dielectric layer 2, the readout layer 3, the intermediate layer 30 made of a non-magnetic film, the recording layer 4, and the second transparent layer. There is a magneto-optical disk in which a dielectric layer 21, a reflective layer 22, and an overcoat layer 6 are laminated in this order.
This magneto-optical disk has a recording layer 4 of the magneto-optical disk.
The second transparent dielectric layer 21 and the reflective layer 22 are provided between the overcoat layer 6 and the overcoat layer 6, and the second transparent dielectric layer 2
1 and the reflective layer 22 are as described in detail in the first embodiment.

In the above-mentioned first to sixth embodiments, the magneto-optical disk is taken as an example of the magneto-optical recording medium, but the present invention can be applied to a magneto-optical card and a magneto-optical tape. In addition,
In the case of a magneto-optical tape, a flexible tape base (base), for example, a tape base made of polyethylene terephthalate may be used instead of the rigid substrate 1.

A magneto-optical disk according to the invention of claim 1 is a substrate 1 having a light-transmitting property, and is formed on the substrate 1 and exhibits in-plane magnetization at room temperature in which in-plane magnetic anisotropy is dominant, The read layer 3 has a read layer 3 that shifts to a perpendicular magnetization in which the perpendicular magnetic anisotropy is dominant as the temperature rises, and a recording layer 4 formed on the read layer 3 for magneto-optically recording information.
Is GdFeCo.

Therefore, it becomes possible to reproduce the recording bit smaller than the conventional one, and the recording density is remarkably improved. Moreover, by adopting GdFeCo, it is possible to realize the read layer 3 in which the magnetization direction changes from the in-plane magnetization to the perpendicular magnetization very sharply. As a result, noise during reproduction is reduced, so that it is possible to provide a magneto-optical disk capable of performing higher density recording.

In the magneto-optical disk according to the second aspect of the present invention, since the recording layer 4 is DyFeCo, in addition to the above-mentioned function and effect, the material of the recording layer 4 is DyFeCo.
By adopting, the perpendicular magnetic anisotropy becomes smaller.
As a result, the external magnetic field during recording can be reduced.

In the magneto-optical disk according to the invention of claim 3, the transparent dielectric layer 2 is formed between the substrate 1 and the reading layer 3, and the protective layer 5 is formed on the recording layer 4. At least one of the transparent dielectric layer 2 and the protective layer 5 is made of AlN. Therefore, it is possible to provide a magneto-optical disk having excellent moisture resistance.

A magneto-optical disk according to a fourth aspect of the present invention comprises a transparent substrate 1, a transparent dielectric layer 2 formed on the substrate 1, and a transparent dielectric layer 2 formed at room temperature. In the in-plane magnetic anisotropy, the in-plane magnetization is dominant and the perpendicular magnetic anisotropy shifts to the perpendicular magnetization as the temperature rises. It has a recording layer 4 for magnetic recording and a protective layer 5 formed on the recording layer 4, and at least one of the transparent dielectric layer 2 and the protective layer 5 is a transparent dielectric containing no oxygen. Since it is made of a material, an excellent magneto-optical disk can be provided.

In the magneto-optical disk according to the invention of claim 5, the oxygen-free transparent dielectric material is SiN,
Since it is any one of AlSiN, AlTaN, TiN, BN, and ZnS, it is possible to provide a magneto-optical disk excellent in long-term reliability in addition to the effect of claim 4.

A magneto-optical disk according to a sixth aspect of the present invention comprises a transparent substrate 1, a transparent dielectric layer 2 formed on the substrate 1, a transparent dielectric layer 2 formed on the transparent dielectric layer 2, and room temperature. In the in-plane magnetic anisotropy, the in-plane magnetization is dominant and the perpendicular magnetic anisotropy shifts to the perpendicular magnetization as the temperature rises. It has a recording layer 4 for magnetic recording and a protective layer 5 formed on the recording layer 4, and at least one of the transparent dielectric layer 2 and the protective layer 5 is a transparent dielectric material containing nitrogen. Therefore, an excellent magneto-optical disk can be provided.

In the magneto-optical disk according to the invention of claim 7, the nitrogen-containing transparent dielectric material is SiN or Al.
SiN, AlTaN, TiN, BN, SiAlON, T
Since it is one of iON, in addition to the effect of claim 6,
A magneto-optical disk having excellent long-term reliability can be provided.

A magneto-optical disk according to an eighth aspect of the present invention comprises a transparent substrate 1, a transparent dielectric layer 2 formed on the substrate 1, a transparent dielectric layer 2 formed at the room temperature, and a room temperature. In the in-plane magnetic anisotropy, the in-plane magnetization is dominant and the perpendicular magnetic anisotropy shifts to the perpendicular magnetization as the temperature rises. It has a recording layer 4 for magnetic recording and a protective layer 5 formed on the recording layer 4, and at least one of the transparent dielectric layer 2 and the protective layer 5 has a refractive index of 2.2 or more. Since it is made of a transparent dielectric material, it is possible to provide an excellent magneto-optical disk.

In the magneto-optical disk according to the invention of claim 9, the transparent dielectric material having a refractive index of 2.2 or more is TiN, ZnS, TiO, TiO ₂ , or BaTiO 3.
_3, because it is one of SrTiO _3, in addition to the above functions and effects can be provided an excellent magneto-optical disk.

According to the magneto-optical disk of the tenth aspect of the present invention, the read layer 3 made of GdFeCo has an N content.
Since at least one element selected from d, Pr, Pt, and Pd is added, in addition to the above-mentioned effects,
A reproduction signal becomes large when a short wavelength laser is used as a light source.

In a magneto-optical disk according to the invention of claim 11, at least one of the read layer 3 and the recording layer 4 made of GdFeCo is Cr, N.
Since at least one element selected from i, Mn, Be, V, and Nb is added, long-term reliability is improved in addition to the above function and effect.

A magneto-optical disk according to a twelfth aspect of the present invention is a substrate 1 having a light-transmitting property, and is formed on the substrate 1 and exhibits in-plane magnetization with in-plane magnetic anisotropy predominant at room temperature. The recording layer 4 has a read layer 3 that shifts to perpendicular magnetization in which the perpendicular magnetic anisotropy is dominant as the temperature rises, and a recording layer 4 that is formed on the read layer 3 and magneto-optically records information. Is TbFeCo, the perpendicular magnetic anisotropy becomes large in addition to the effect of claim 1. This makes it possible to provide a magneto-optical disk having a high reproduction signal quality.

A magneto-optical disk according to a thirteenth aspect of the present invention is a substrate 1 having a light-transmitting property, formed on the substrate 1, and exhibiting in-plane magnetization at room temperature in which in-plane magnetic anisotropy is dominant, The read layer 3 has a read layer 3 that shifts to a perpendicular magnetization in which the perpendicular magnetic anisotropy is dominant as the temperature rises, and a recording layer 4 formed on the read layer 3 for magneto-optically recording information. Is composed of a rare earth-transition metal amorphous alloy having ferrimagnetism, its composition is set so that its compensation temperature is 125 ° C. or higher, and its film thickness is set to 10 nm or higher. The quality of the reproduced signal when reading the recorded information is improved.

According to a fourteenth aspect of the present invention, a magneto-optical disk has a light-transmissive substrate 1, and is formed on the substrate 1 and exhibits in-plane magnetization at room temperature in which in-plane magnetic anisotropy is dominant. The read layer 3 has a read layer 3 that shifts to a perpendicular magnetization in which the perpendicular magnetic anisotropy is dominant as the temperature rises, and a recording layer 4 formed on the read layer 3 for magneto-optically recording information. Is composed of a rare-earth transition metal amorphous alloy having ferrimagnetism and has a Curie temperature of 1 without compensation temperature.
Since the composition is set to 30 ° C. or higher and the film thickness is set to 10 nm or higher, the reproduction signal quality at the time of reading information recorded at high density is improved.

A magneto-optical disk according to a fifteenth aspect of the present invention is a substrate 1 having a light-transmitting property, and formed on the substrate 1 and exhibiting in-plane magnetization in which in-plane magnetic anisotropy is dominant at room temperature, The substrate 1 has a read layer 3 that shifts to perpendicular magnetization in which the perpendicular magnetic anisotropy is dominant as the temperature rises, and a recording layer 4 that is formed on the read layer 3 and magneto-optically records information. Since a groove for guiding a light beam is provided on the surface of the read layer 3 side of the disk, and the width of the groove is set to be substantially equal to the width of the land between the grooves, recording on the groove is performed. The reproduction signal quality when reading the information recorded on the layer 4 and the recording layer 4 on the land becomes the same.

In the magneto-optical disk according to the sixteenth aspect of the invention, information is magneto-optically recorded in the recording layer 4 on the groove and the recording layer 4 on the land. Since information is magneto-optically recorded on the recording layer 4 and the recording layer 4 on the land, the recording density is doubled.

A magneto-optical disk according to a seventeenth aspect of the present invention is a substrate 1 having a light-transmitting property, and is formed on the substrate 1 and exhibits an in-plane magnetization state in which in-plane magnetic anisotropy is dominant at room temperature. ,
A read layer 3 that shifts to a perpendicular magnetization state in which perpendicular magnetic anisotropy is dominant as the temperature rises, and is formed on the read layer 3.
The readout layer 3 is made of a rare earth-transition metal alloy, and its compensation temperature is set so as not to be between room temperature and the Curie temperature. Since the content of rare earth metal is set to be higher than the maximum content corresponding to the compensation composition,
A magneto-optical disk capable of high-density recording and reproduction can be provided.

In the magneto-optical disk according to the eighteenth aspect of the present invention, since the intermediate layer made of the in-plane magnetized film is provided between the read layer 3 and the recording layer 4, the above-mentioned function and effect can be obtained. In addition, the exchange coupling force between the read layer 3 and the recording layer 4 can be controlled. As a result, the selection range of materials for the read layer 3 and the recording layer 4 is increased.

[0434] The recording / reproducing method according to the nineteenth aspect of the invention is
A transparent substrate 1 and an in-plane magnetization state formed on the substrate 1 at room temperature in which the in-plane magnetic anisotropy is dominant while the perpendicular magnetic anisotropy state in which the perpendicular magnetic anisotropy is dominant as the temperature rises. And a recording layer 4 formed on the reading layer 3 for magneto-optically recording information, the reading layer 3 being made of a rare earth transition metal alloy and having a compensation temperature thereof. Is set between room temperature and Curie temperature,
In addition, there is provided a recording / reproducing method for recording / reproducing information by using a magneto-optical disk in which the content of the rare earth metal is set to be higher than the maximum content corresponding to the compensating composition. While applying a constant magnetic field that magnetizes,
By irradiating a laser beam switched to a relatively low first laser power and a relatively high second laser power according to a recording signal, the magnetization direction of the recording layer 4 is reversed to perform recording, and By irradiating laser light with a laser power lower than the laser power of
A region smaller than the laser spot diameter of the reading layer 3 is shifted to the perpendicular magnetization state, and the sub-lattice magnetization of the region of the reading layer 3 in the perpendicular magnetization state is stable to the sub-lattice magnetization of the recording layer 4. The configuration is such that information is reproduced from the aligned and read-out layer 3 in the perpendicularly magnetized region.

Therefore, high density recording / reproducing can be performed by using the magneto-optical disk according to the invention of claim 17.

A magneto-optical disk according to the twentieth aspect of the present invention is a substrate 1 having a light-transmitting property, and is formed on the substrate 1 and exhibits an in-plane magnetization state in which in-plane magnetic anisotropy is dominant at room temperature. ,
A read layer 3 that shifts to a perpendicular magnetization state in which perpendicular magnetic anisotropy is dominant as the temperature rises, and is formed on the read layer 3.
It has a recording layer 4 for magneto-optically recording information, and an intermediate layer made of a non-magnetic film is provided between the reading layer 3 and the recording layer 4, so that the reading layer 3 and the recording layer 4 are provided. The exchange coupling between and is weakened. As a result, it is possible to provide a magneto-optical disk that can stably perform high-density recording.

A recording / reproducing method according to the invention of claim 21
As described above, the light-transmitting substrate 1 and the in-plane magnetization formed on the substrate 1 with the in-plane magnetic anisotropy predominant at room temperature are shown, while the perpendicular magnetic anisotropy is superior with increasing temperature. Formed on the read layer 3 and a read layer 3 that shifts to a perpendicular magnetization
A recording layer 4 for magneto-optically recording information is provided, and a groove for guiding a light beam is provided on the surface of the substrate 1 on the side of the readout layer 3, and the width of the groove is between the grooves. A recording / reproducing method using a magneto-optical disk set to be almost equal to the width of the land of
Recording layer 4 on the groove and recording layer 4 on the land
Is used for recording / reproducing information, the recording density is doubled.

[0438]

As described above, the magneto-optical recording medium according to the first aspect of the present invention has a substrate having a light-transmitting property and an in-plane in which the in-plane magnetic anisotropy is superior at room temperature. The magnetic recording medium has a read layer that exhibits magnetization and shifts to a perpendicular magnetization in which the perpendicular magnetic anisotropy is dominant as the temperature rises, and a recording layer formed on the read layer for magneto-optically recording information. Since the layer is GdFeCo, it is possible to reproduce a recording bit smaller than the conventional one, and the recording density is remarkably improved. Moreover, by adopting GdFeCo,
It is possible to realize a read layer in which the magnetization direction changes very sharply from in-plane magnetization to perpendicular magnetization. As a result, noise at the time of reproduction is reduced, so that it is possible to provide a magneto-optical recording medium capable of high-density recording.

A magneto-optical recording medium according to the invention of claim 2 is
As described above, since the recording layer of claim 1 is DyFeCo, in addition to the effect of claim 1, as a material of the recording layer, D
By adopting yFeCo, the perpendicular magnetic anisotropy becomes small. This has the effect of reducing the external magnetic field during recording.

The magneto-optical recording medium according to the invention of claim 3 is
As described above, in the magneto-optical recording medium according to claim 1 or 2, the transparent dielectric layer is formed between the substrate and the reading layer, and the protective layer is formed on the recording layer. Since at least one of the transparent dielectric layer and the protective layer is AlN, in addition to the effect of claim 1 or 2, a transparent dielectric layer is formed between the substrate and the read layer, and the recording is performed. Since the protective layer is formed on the layer and at least one of the transparent dielectric layer and the protective layer is made of AlN, it is possible to provide a magneto-optical recording medium excellent in moisture resistance.

The magneto-optical recording medium according to the invention of claim 4 is
As described above, a translucent substrate, a transparent dielectric layer formed on the substrate, and an in-plane magnetization that is formed on the transparent dielectric layer and in which the in-plane magnetic anisotropy is dominant is exhibited at room temperature. On the other hand, a reading layer in which perpendicular magnetic anisotropy shifts to a perpendicular magnetization with an increase in temperature, a recording layer formed on the reading layer for magneto-optical recording of information, and a protective layer formed on the recording layer. Since at least one of the transparent dielectric layer and the protective layer is made of a transparent dielectric material containing no oxygen, it is possible to provide an excellent magneto-optical recording medium.

The magneto-optical recording medium according to the invention of claim 5 is
As described above, the oxygen-free transparent dielectric material according to claim 4 is SiN, AlSiN, AlTaN, TiN, B.
Since it is N or ZnS, in addition to the effect of the fourth aspect, there is an effect that a magneto-optical recording medium excellent in long-term reliability can be provided.

The magneto-optical recording medium according to the invention of claim 6 is
As described above, a translucent substrate, a transparent dielectric layer formed on the substrate, and an in-plane magnetization that is formed on the transparent dielectric layer and in which the in-plane magnetic anisotropy is dominant is exhibited at room temperature. On the other hand, a reading layer in which perpendicular magnetic anisotropy shifts to a perpendicular magnetization with an increase in temperature, a recording layer formed on the reading layer for magneto-optical recording of information, and a protective layer formed on the recording layer. And at least one of the transparent dielectric layer and the protective layer is made of a transparent dielectric material containing nitrogen,
It is possible to provide an excellent magneto-optical recording medium.

The magneto-optical recording medium according to the invention of claim 7 is
As described above, the transparent dielectric material containing nitrogen according to claim 6 is SiN, AlSiN, AlTaN, TiN, BN,
Since it is either SiAlON or TiON, in addition to the effect of the sixth aspect, there is an effect that a magneto-optical recording medium excellent in long-term reliability can be provided.

The magneto-optical recording medium according to the invention of claim 8 is
As described above, a translucent substrate, a transparent dielectric layer formed on the substrate, and an in-plane magnetization that is formed on the transparent dielectric layer and in which the in-plane magnetic anisotropy is dominant is exhibited at room temperature. On the other hand, a reading layer in which perpendicular magnetic anisotropy shifts to a perpendicular magnetization with an increase in temperature, a recording layer formed on the reading layer for magneto-optical recording of information, and a protective layer formed on the recording layer. Since at least one of the transparent dielectric layer and the protective layer is made of a transparent dielectric material having a refractive index of 2.2 or more, it is possible to provide an excellent magneto-optical recording medium. Play.

The magneto-optical recording medium according to the invention of claim 9 is
As described above, the transparent dielectric material having a refractive index of 2.2 or more according to claim 8 is TiN, ZnS, TiON, Ti.
Since it is any one of O ₂ , BaTiO ₃ , and SrTiO ₃ , it has the effect of providing an excellent magneto-optical recording medium in addition to the effect of claim 8.

According to the magneto-optical recording medium of the tenth aspect of the present invention, as described above, at least one element selected from Nd, Pr, Pt, and Pd is contained in the read layer made of GdFeCo of the first aspect. Claim 1 since it is added
In addition to the above effect, there is an effect that a reproduction signal becomes large when a short wavelength laser is used as a light source.

As described above, in the magneto-optical recording medium according to the invention of claim 11, Cr, Ni, Mn, Be and V are contained in at least one of the read layer made of GdFeCo of claim 1 and the recording layer. , And Nb, at least one of these elements is added, so that in addition to the effect of claim 1, the effect of improving long-term reliability is achieved.

As described above, the magneto-optical recording medium according to the invention of claim 12 has a substrate having a light-transmitting property and an in-plane magnetization which is formed on the substrate and has in-plane magnetic anisotropy predominant. On the other hand, it has a read layer that shifts to perpendicular magnetization where the perpendicular magnetic anisotropy is dominant as the temperature rises, and a recording layer that is formed on the read layer and magneto-optically records information. Since it is TbFeCo, the perpendicular magnetic anisotropy becomes large in addition to the effect of the first aspect. As a result, it is possible to provide a magneto-optical recording medium with high reproduction signal quality.

As described above, the magneto-optical recording medium according to the thirteenth aspect of the present invention has a translucent substrate and an in-plane magnetization that is formed on the substrate and has in-plane magnetic anisotropy predominant at room temperature. On the other hand, it has a read layer that shifts to perpendicular magnetization in which the perpendicular magnetic anisotropy is dominant as the temperature rises, and a recording layer formed on the read layer for magneto-optically recording information. , A rare-earth transition metal amorphous alloy having ferrimagnetism, the composition is set so that the compensation temperature is 125 ° C. or more, and the film thickness is set to 10 nm or more. This has the effect of improving the quality of the reproduced signal when reading the read information.

As described above, the magneto-optical recording medium according to the fourteenth aspect of the present invention has a translucent substrate and an in-plane magnetization which is formed on the substrate and has in-plane magnetic anisotropy predominant at room temperature. On the other hand, it has a read layer that shifts to perpendicular magnetization in which the perpendicular magnetic anisotropy is dominant as the temperature rises, and a recording layer formed on the read layer for magneto-optically recording information. , Made of a rare-earth transition metal amorphous alloy with ferrimagnetism and has a Curie temperature of 1 without compensation temperature.
Since the composition is set to 30 ° C. or more and the film thickness is set to 10 nm or more, there is an effect that the quality of a reproduced signal when reading high density recorded information is improved.

As described above, the magneto-optical recording medium according to the fifteenth aspect of the present invention has a translucent substrate and an in-plane magnetization which is formed on the substrate and has in-plane magnetic anisotropy predominant at room temperature. On the other hand, it has a read layer that shifts to perpendicular magnetization in which the perpendicular magnetic anisotropy is dominant as the temperature rises, and a recording layer formed on the read layer for magneto-optically recording information. Since the groove for guiding the light beam is provided on the surface on the read layer side and the width of the groove is set to be substantially equal to the width of the land between the grooves,
An advantage is that the reproduction signal quality when reading the information recorded on the recording layer on the groove and the information recorded on the recording layer on the land are the same.

In the magneto-optical recording medium according to the sixteenth aspect of the invention, as described above, since information is magneto-optically recorded in the recording layer on the groove and the recording layer on the land of the fifteenth aspect,
In addition to the effect of claim 15, since information is magneto-optically recorded on the recording layer on the groove and the recording layer on the land, the recording density is doubled.

As described above, the magneto-optical recording medium according to the seventeenth aspect of the present invention is a translucent substrate, and an in-plane magnetized state which is formed on the substrate and in which the in-plane magnetic anisotropy is dominant at room temperature. On the other hand, the reading layer has a reading layer that shifts to a perpendicular magnetization state in which the perpendicular magnetic anisotropy is dominant as the temperature rises, and a recording layer that is formed on the reading layer and magneto-optically records information. The layer consists of a rare earth transition metal alloy, the compensation temperature of which is set between room temperature and the Curie temperature, and the content of rare earth metal is higher than the maximum content corresponding to the compensation composition. Is set to
It is possible to provide a magneto-optical recording medium capable of high-density recording and reproduction.

In the magneto-optical recording medium according to the eighteenth aspect of the invention, as described above, since the intermediate layer made of the in-plane magnetized film is provided between the read layer and the recording layer of the seventeenth aspect, In addition to the effect of claim 17, it becomes possible to control the exchange coupling force between the read layer and the recording layer. This has the effect of increasing the selection range of materials for the read layer and the recording layer.

A recording / reproducing method according to the invention of claim 19
As described above, a light-transmissive substrate and an in-plane magnetization state formed on the substrate and having in-plane magnetic anisotropy predominant at room temperature, while perpendicular magnetic anisotropy predominates as temperature rises. It has a read layer that shifts to a perpendicular magnetization state, and a recording layer that is formed on the read layer and magneto-optically records information.The read layer is made of a rare earth transition metal alloy, and its compensation temperature is Recording of information using a magneto-optical recording medium that is set so as not to be between room temperature and the Curie temperature, and the content of the rare earth metal is set to be higher than the maximum content corresponding to the compensation composition. A recording / reproducing method for reproducing, wherein laser light is switched to a relatively low first laser power and a relatively high second laser power according to a recording signal while applying a constant magnetic field for magnetizing a read layer. Irradiating Recording is performed by reversing the magnetization direction of the recording layer, and by irradiating a laser beam with a laser power lower than the first laser power, a region smaller than the laser spot diameter of the reading layer is shifted to the perpendicular magnetization state. In addition, the sub-lattice magnetization of the read layer in the perpendicular magnetization state is aligned in a stable direction with respect to the sub-lattice magnetization of the recording layer, and information is reproduced from the read layer in the perpendicular magnetization state. Therefore, high density recording / reproducing can be performed by using the magneto-optical recording medium according to claim 17.

As described above, the magneto-optical recording medium according to the twentieth aspect of the present invention is a translucent substrate, and an in-plane magnetized state formed on the substrate and having a superior in-plane magnetic anisotropy at room temperature. On the other hand, the reading layer has a reading layer that shifts to a perpendicular magnetization state in which the perpendicular magnetic anisotropy is dominant as the temperature rises, and a recording layer that is formed on the reading layer and magneto-optically records information. Since the intermediate layer made of a non-magnetic film is provided between the layer and the recording layer, the exchange coupling between the read layer and the recording layer is weakened. As a result, it is possible to provide a magneto-optical recording medium that can stably perform high-density recording.

A recording / reproducing method according to the invention of claim 21
As described above, a translucent substrate and an in-plane magnetization formed on the substrate, which has a superior in-plane magnetic anisotropy at room temperature, and a perpendicular magnetic anisotropy, in which the perpendicular magnetic anisotropy is superior as the temperature increases It has a read layer that shifts to magnetization, and a recording layer that is formed on the read layer and magneto-optically records information, and a groove for guiding a light beam is provided on the read layer side surface of the substrate. A recording / reproducing method using a magneto-optical recording medium in which the width of the groove is set to be substantially equal to the width of the land between the grooves. Since this recording layer is used for recording / reproducing information, the recording layer on the groove and the recording layer on land are used for recording / reproducing information, so that the recording density is doubled.

[Brief description of drawings]

FIG. 1 shows a first embodiment of the present invention and is an explanatory diagram showing a schematic configuration of a magneto-optical disk and a reproducing operation.

FIG. 2 is an explanatory diagram of a magnetic state showing magnetic characteristics of a read layer of the magneto-optical disk of FIG.

FIG. 3 is an explanatory diagram showing a relationship between an externally applied magnetic field applied to the read layer and a polar Kerr rotation angle from room temperature to temperature T ₁ in FIG.

FIG. 4 is an explanatory diagram showing a relationship between an externally applied magnetic field applied to the read layer and a polar Kerr rotation angle from temperature T ₁ to temperature T ₂ in FIG.

5 is an explanatory diagram showing a relationship between an externally applied magnetic field applied to the read layer and a polar Kerr rotation angle at temperatures T ₂ to T ₃ in FIG. 2;

6 is an explanatory diagram showing a relationship between an externally applied magnetic field applied to the read layer and a polar Kerr rotation angle at a temperature T ₃ Curie temperature Tc in FIG. 2.

7 is a graph showing the results of actually measuring the externally applied magnetic field dependence of the polar Kerr rotation angle at room temperature of the read layer of the magneto-optical disk of FIG.

8 is a reading layer of the magneto-optical disk of FIG. 1 at 120 ° C.
4 is a graph showing the results of actually measuring the externally applied magnetic field dependence of the polar Kerr rotation angle in FIG.

9 is a graph in which the reproduction signal amplitude of the magneto-optical disk of FIG. 1 is plotted against the reproduction laser power.

10 is a reproduction signal quality (C / N) of the magneto-optical disk of FIG.
6 is a graph in which is plotted against the recording bit length.

11 is a graph showing a result of measuring crosstalk of the magneto-optical disk of FIG.

FIG. 12 is an explanatory diagram showing an effect of the magneto-optical disk of FIG.

FIG. 13 Curie temperature (Tc) of Gd _X (Fe _0.82 Co _0.18 ) _1-X
5 is a graph showing the composition dependence of the compensation temperature (Tcomp) and

FIG. 14: Curie temperature (Tc) and compensation temperature (T of Gd _X Fe _1-X
It is the graph which showed the composition dependence of comp).

FIG. 15: Curie temperature (Tc) and compensation temperature (T of Gd _X Co _1-X
It is the graph which showed the composition dependence of comp).

16 is an explanatory diagram showing an example of land and group shapes formed on the substrate of the magneto-optical disc of FIG.

17 is an explanatory view showing another example of the shapes of lands and groups formed on the substrate of the magneto-optical disc of FIG.

18 is an explanatory diagram showing an example of the arrangement of wobble pits formed on the substrate of the magneto-optical disc of FIG.

19 is an explanatory diagram showing another example of the arrangement of wobble pits formed on the substrate of the magneto-optical disk of FIG.

20 is an explanatory diagram showing an example of a wobble ring groove formed on a substrate of the magneto-optical disc of FIG.

21 is an explanatory diagram showing a recording / reproducing method when a plurality of light beams are used in the magneto-optical disc of FIG.

22 is an explanatory diagram showing a magnetic field modulation overwrite recording method using the magneto-optical disc of FIG. 1. FIG.

FIG. 23 is an explanatory diagram showing a light modulation overwrite recording method using the magneto-optical disk of FIG. 1 and a magnetization method of a read layer and a recording layer.

24 is an explanatory diagram showing an optical modulation overwrite recording method using the magneto-optical disk of FIG. 1 and showing temperature dependence of coercive force of a read layer and a recording layer.

FIG. 25 is an explanatory diagram showing an example of the intensity of a light beam with which the magneto-optical disk of FIG. 1 is irradiated at the time of optical modulation overwrite and at the time of reproduction.

FIG. 26 is an explanatory diagram showing another example of the intensity of the light beam with which the magneto-optical disk of FIG. 1 is irradiated at the time of optical modulation overwrite and at the time of reproduction.

FIG. 27 is an explanatory diagram showing another example of the intensity of the light beam with which the magneto-optical disk of FIG. 1 is irradiated at the time of light modulation overwriting and at the time of reproduction.

28 is an explanatory diagram showing a single-sided type of the magneto-optical disc of FIG. 1. FIG.

FIG. 29 is an explanatory diagram showing a double-sided type of the magneto-optical disk of FIG. 1.

30 is an explanatory diagram showing a schematic configuration of a sample for investigating the effect of increasing the Kerr rotation angle when an element is added to the read layer of the magneto-optical disc of FIG. 1. FIG.

31 is a graph showing wavelength dependence of Kerr rotation angle of the sample of FIG. 30. FIG.

32 is an explanatory diagram showing a schematic configuration of a sample for investigating the effect of improving the moisture resistance when an element is added to the read layer of the magneto-optical disc of FIG. 1. FIG.

FIG. 33 is a graph showing the change over time in the C / N ratio of the sample of FIG. 32.

34 is a graph showing a Kerr hysteresis loop measured by changing the film thickness of the readout layer of the magneto-optical disk of FIG. 1, wherein (a) to (d) show a film thickness of 20, and FIG.
Kerr hysteresis obtained at 30, 40 and 50 nm
It is a graph which shows a loop.

35 is a graph plotting the squareness ratio of the readout layer of the magneto-optical disk of FIG. 1 against the film thickness for each compensation temperature.

FIG. 36 is an explanatory diagram showing a calculation method for obtaining the squareness ratio from FIG. 29.

37 is a graph plotting the squareness ratio of the read layer of the magneto-optical disk of FIG. 1 against the film thickness for each Curie temperature.

38 is a graph showing a Kerr loop obtained by the magneto-optical disc of FIG. 1, and (a) and (b) are Kerr loops obtained by the magneto-optical disc using TbFeCo and DyFeCo in the recording layers, respectively. is there.

FIG. 39 shows a second embodiment of the present invention and is a schematic configuration diagram of a magneto-optical disk.

FIG. 40 shows a third embodiment of the present invention and is a schematic configuration diagram of a magneto-optical disk.

FIG. 41 shows a fourth embodiment of the present invention and is a schematic configuration diagram of a magneto-optical disk.

42 is an explanatory diagram showing temperature characteristics of coercive force of the read layer and the recording layer of FIG. 41.

FIG. 43 shows a fifth embodiment of the present invention and is a schematic configuration diagram of a magneto-optical disk.

FIG. 44 shows a sixth embodiment of the present invention and is a schematic configuration diagram of a magneto-optical disk.

FIG. 45 shows a variation of the magneto-optical disc shown in FIG. 44, and is a schematic configuration diagram of the magneto-optical disc having a heat dissipation layer.

FIG. 46 shows a variation of the magneto-optical disc shown in FIG. 44, and is a schematic configuration diagram of the magneto-optical disc having a reflective layer.

[Explanation of symbols]

 1 Substrate 1 (Substrate) 2 Transparent Dielectric Layer 3 Readout Layer 4 Recording Layer 5 Protective Layer 6 Overcoat Layer 9 Recording Medium Layer 10 Adhesive Layer 20 Heat Dissipation Layer 21 Transparent Dielectric Layer (Second Transparent Dielectric Layer) 22 Reflective Layer 29 middle layer 30 middle layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junsaku Nakajima 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (72) Inventor Akira Takahashi 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka (72) Inventor Kenji Ota 22-22, Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) In-house, Naoyasu Ikeya 22-22, Nagaike-cho, Abeno-ku, Osaka, Osaka Within

Claims (21)

[Claims] 1. A transparent substrate and a substrate formed on the substrate,
At room temperature, the in-plane magnetic anisotropy exhibits a dominant in-plane magnetization, while as the temperature increases, the perpendicular magnetic anisotropy shifts to the dominant perpendicular magnetization. A magneto-optical recording medium having a recording layer for recording, wherein the reading layer is GdFeCo. 2. The magneto-optical recording medium according to claim 1, wherein the recording layer is DyFeCo. 3. A transparent dielectric layer is formed between the substrate and the readout layer, and a protective layer is formed on the recording layer, and at least one of the transparent dielectric layer and the protective layer is formed. The magneto-optical recording medium according to claim 1, which is AlN. 4. A translucent substrate, a transparent dielectric layer formed on the substrate, and an in-plane magnetization which is formed on the transparent dielectric layer and has an in-plane magnetic anisotropy predominant at room temperature. On the other hand, a reading layer in which perpendicular magnetic anisotropy shifts to a perpendicular magnetization with an increase in temperature, a recording layer formed on the reading layer for magneto-optical recording of information, and a protective layer formed on the recording layer. At least one of the transparent dielectric layer and the protective layer is made of a transparent dielectric material containing no oxygen. 5. The transparent dielectric material containing no oxygen is S
iN, AlSiN, AlTaN, TiN, BN, ZnS
The magneto-optical recording medium according to claim 4, wherein the magneto-optical recording medium is any one of the following: 6. A translucent substrate, a transparent dielectric layer formed on the substrate, and an in-plane magnetization which is formed on the transparent dielectric layer and has in-plane magnetic anisotropy predominant at room temperature. On the other hand, a reading layer in which perpendicular magnetic anisotropy shifts to a perpendicular magnetization with an increase in temperature, a recording layer formed on the reading layer for magneto-optical recording of information, and a protective layer formed on the recording layer. At least one of the transparent dielectric layer and the protective layer is made of a transparent dielectric material containing nitrogen. 7. The transparent dielectric material containing nitrogen is Si.
N, AlSiN, AlTaN, TiN, BN, SiAl
7. The magneto-optical recording medium according to claim 6, which is either ON or TiON. 8. A translucent substrate, a transparent dielectric layer formed on the substrate, and an in-plane magnetization having an in-plane magnetic anisotropy which is formed on the transparent dielectric layer and has a dominant in-plane magnetic anisotropy at room temperature. On the other hand, a reading layer in which perpendicular magnetic anisotropy shifts to a perpendicular magnetization with an increase in temperature, a recording layer formed on the reading layer for magneto-optical recording of information, and a protective layer formed on the recording layer. And a at least one of the transparent dielectric layer and the protective layer is made of a transparent dielectric material having a refractive index of 2.2 or more. 9. The transparent dielectric material having a refractive index of 2.2 or more includes TiN, ZnS, TiO, TiO ₂ , and BaT.
The magneto-optical recording medium according to claim 8, which is one of iO ₃ and SrTiO ₃ . 10. The magneto-optical recording medium according to claim 1, wherein at least one element selected from Nd, Pr, Pt and Pd is added to the read layer made of GdFeCo. 11. A read layer made of GdFeCo and / or a recording layer containing at least one of Cr and N.
2. At least one element selected from i, Mn, Be, V, and Nb is added.
The magneto-optical recording medium described. 12. A light-transmissive substrate, and a perpendicular magnetic film formed on the substrate, which exhibits in-plane magnetization with in-plane magnetic anisotropy predominant at room temperature, and perpendicular magnetic anisotropy with temperature rise. A magneto-optical recording medium comprising a read layer that shifts to magnetization and a recording layer formed on the read layer for magneto-optically recording information, wherein the recording layer is TbFeCo. 13. A translucent substrate, and a perpendicular magnetic film formed on the substrate, which exhibits in-plane magnetization with in-plane magnetic anisotropy predominant at room temperature, and has perpendicular magnetic anisotropy with temperature increase. It has a read layer that shifts to magnetization and a recording layer that is formed on the read layer and magneto-optically records information. The read layer is made of a rare earth transition metal amorphous alloy having ferrimagnetism. , The composition is set so that the compensation temperature is 125 ° C. or higher, and the film thickness is 10 nm.
A magneto-optical recording medium having the above settings. 14. A translucent substrate, and a perpendicular magnetic film formed on the substrate, which exhibits in-plane magnetization with in-plane magnetic anisotropy predominant at room temperature, and perpendicular magnetic anisotropy with temperature rise. It has a read layer that shifts to magnetization and a recording layer that is formed on the read layer and magneto-optically records information. The read layer is made of a rare earth transition metal amorphous alloy having ferrimagnetism. , The composition is set so that the Curie temperature is 130 ° C or higher without the compensation temperature,
A magneto-optical recording medium having a thickness of 10 nm or more. 15. A translucent substrate, and a perpendicular magnetic film formed on the substrate, which exhibits in-plane magnetization with in-plane magnetic anisotropy predominant at room temperature, while having perpendicular magnetic anisotropy with temperature rise. It has a read layer that shifts to magnetization and a recording layer that is formed on the read layer and magneto-optically records information. The surface of the base body on the read layer side has a groove for guiding a light beam. Is provided, and the width of the groove is set to be substantially equal to the width of the land between the grooves. 16. A magneto-optical recording medium according to claim 15, wherein information is magneto-optically recorded on the recording layer on the groove and the recording layer on the land. 17. A translucent substrate and an in-plane magnetized state formed on the substrate and having an in-plane magnetic anisotropy predominant at room temperature, while a perpendicular magnetic anisotropy becomes dominant as the temperature rises. It has a read layer that shifts to a perpendicular magnetization state, and a recording layer that is formed on the read layer and magneto-optically records information.The read layer is made of a rare earth transition metal alloy, and its compensation temperature is A magneto-optical recording medium, characterized in that it is set so as not to be between room temperature and the Curie temperature, and the content of the rare earth metal is set to be higher than the maximum content corresponding to the compensation composition. 18. The magneto-optical recording medium according to claim 17, wherein an intermediate layer made of an in-plane magnetized film is provided between the read layer and the recording layer. 19. A light-transmissive substrate and an in-plane magnetization state formed on the substrate and having in-plane magnetic anisotropy predominant at room temperature, while perpendicular magnetic anisotropy predominates as temperature rises. It has a read layer that shifts to a perpendicular magnetization state, and a recording layer that is formed on the read layer and magneto-optically records information.The read layer is made of a rare earth transition metal alloy, and its compensation temperature is Recording of information using a magneto-optical recording medium that is set so as not to be between room temperature and the Curie temperature, and the content of the rare earth metal is set to be higher than the maximum content corresponding to the compensation composition. A recording / reproducing method for reproducing, wherein laser light is switched to a relatively low first laser power and a relatively high second laser power according to a recording signal while applying a constant magnetic field for magnetizing a read layer. Irradiating Recording is performed by reversing the magnetization direction of the recording layer by irradiating with a laser beam having a laser power lower than the first laser power, and a region smaller than the laser spot diameter of the reading layer is shifted to the perpendicular magnetization state. In addition, the sub-lattice magnetization of the region of the read layer in the perpendicular magnetization state is aligned in a stable direction with respect to the sub-lattice magnetization of the recording layer, and information is reproduced from the region of the read layer in the perpendicular magnetization state. A recording / reproducing method characterized by the above. 20. A light-transmissive substrate and an in-plane magnetization state formed on the substrate, in which the in-plane magnetic anisotropy is dominant at room temperature, while the perpendicular magnetic anisotropy is dominant as the temperature rises. It has a read layer that shifts to a perpendicular magnetization state, and a recording layer formed on the read layer for magneto-optically recording information, and an intermediate layer made of a non-magnetic film between the read layer and the recording layer. A magneto-optical recording medium comprising: 21. A translucent substrate, and a perpendicular magnetic layer formed on the substrate, which exhibits in-plane magnetization with in-plane magnetic anisotropy predominant at room temperature, and perpendicular magnetic anisotropy with temperature rise. It has a read layer that shifts to magnetization, and a recording layer that is formed on the read layer and magneto-optically records information, and a groove for guiding a light beam is provided on the read layer side surface of the substrate. A recording / reproducing method using a magneto-optical recording medium in which the width of the groove is set to be substantially equal to the width of the land between the grooves. A recording / reproducing method characterized in that the recording layer is used for recording / reproducing information.