JP3454955B2 - Magneto-optical recording medium and magneto-optical recording medium reproducing apparatus - Google Patents

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 and a magneto-optical recording medium reproducing apparatus, and more particularly to recording information recorded by a recording mark smaller than the optical diffraction limit of a light beam for reproducing information. The present invention relates to a magneto-optical recording medium and a magneto-optical recording medium reproducing apparatus capable of performing so-called super-resolution reproduction.

[0002]

2. Description of the Related Art Magneto-optical recording media such as so-called magneto-optical discs are widely used today as recording media for recording images and computer data because information can be recorded at high density on the information recording surface. It's being used.

In recent years, attempts have been made to record high-definition television signals on this magneto-optical recording medium. However, the above-mentioned high-definition television signals are recorded on magneto-optical recording media having conventional recording densities. When I try to record
The amount of information that can be recorded on a single magneto-optical recording medium is only about 10 minutes as a reproduction time. Therefore, it is required to improve the recording density of information in the magneto-optical recording medium.

As a method of improving the information recording density, a method of improving the recording density in the time axis direction (the traveling direction of the magneto-optical recording medium) and a track pitch of an information track composed of recording marks corresponding to the information A method of improving the recording density in the direction (the direction orthogonal to the time axis direction, and in the case of a magneto-optical disk, the radial direction) can be considered.

Here, as the former method (in the case of improving the recording density in the time axis direction), the MSR (Magn
So-called super-resolution reproduction such as etically induced Super Resolution) has been proposed.

Here, an outline of the MSR will be described. It has been conventionally known in the world of microscopes that resolution is improved by providing an optical mask such as a pinhole at the position of an object to be observed. So M
SR does not provide a physical mask on the recording surface of the magneto-optical recording medium, but utilizes the temperature distribution on the medium including the recording surface to create an effective mask in the medium, and to effectively reproduce the reproduction limit. The spatial frequency is increased, and the recording density can be improved by about 1.5 to 3 times (For more details, see "Super-Resolution Magneto-Optical Disk", The Japan Society for Applied Magnetics, Vol1.15, No.5. , 1991 etc.).

Various magneto-optical recording media to which such MSR is applied have been proposed, an example of which is shown in FIG.
A magneto-optical disk 1P as a magneto-optical recording medium is shown in FIG.
As shown in (a), a substrate B ′ transparent to a light beam such as a laser beam and a reproducing layer P ′ having a small coercive force.
A recording layer R ′ having a large coercive force and information recorded in a perpendicular magnetization state, a switch layer S ′ for controlling the exchange coupling force between the reproducing layer P ′ and the recording layer R ′, and a reproducing layer. Layer P ',
A magneto-optical disk 1P and a dielectric protective layer C'such as a Si N layer formed so as to sandwich the magneto-optical layer for protecting the magneto-optical layer composed of the recording layer R'and the switch layer S '.
In order to protect the whole, it is composed of a resin protective layer CP 'formed of a 2P (Photo Polymer) overcoat or the like.

Here, between the Curie temperature T _CR ′ of the recording layer R ′, the Curie temperature T _CP ′ of the reproducing layer P ′ and the Curie temperature T _CS ′ of the switch layer S ′, T _CR ′> T _CS ′, In addition, the composition of the reproducing layer P ', the recording layer R'and the switch layer S'is determined so that the relationship of T _CP '> T _CS 'is established.

Regarding the specific composition of each layer of the magneto-optical disk 1P, for example, the composition of the reproducing layer P'is GdFeC.
and the composition of the switch layer S ′ is TbFe,
TbFeCo is used as the composition of the recording layer R ′.

Next, the operation of recording information on the magneto-optical disk 1P will be described. At the time of recording information, the output power of the light beam, which is the recording light, has a maximum temperature in the irradiation range of the light beam on the magneto-optical disk (hereinafter referred to as a light spot), which is the Curie temperature T of the recording layer R ′.
It is set to be _CR 'or higher. Then, the coercive force of the recording layer R ′, the switch layer S ′, and the reproducing layer P ′ disappears. At this time, if an external magnetic field corresponding to the information to be recorded is applied from the outside, the magneto-optical disk moves. As the temperatures of the recording layer R ′, the switch layer S ′, and the reproducing layer P ′ decrease, the recording layer R ′, the switch layer S ′, and the reproducing layer P ′ are magnetized in the direction of the external magnetic field to record information. .

Next, the information reproducing operation on the magneto-optical disk 1P will be described with reference to FIG.
At the time of reproducing information, the maximum temperature T _H in the light spot is set as the first condition of the output power of the light beam which is the reproduction light.
_Are set so that T _H <T _CR '. Then, when the light beam whose output power is set in this way is applied to the magneto-optical disk 1P from the reproducing layer P ′ side, as the magneto-optical disk 1P moves, as shown in FIG. A region having a higher temperature than the surroundings (hereinafter referred to as a high temperature region) is formed in the rear part of the spot.

The temperature of this high temperature region is equal to or higher than the Curie point of the switch layer S ', and the temperature of other regions within the light spot (hereinafter referred to as low temperature region) is the switch layer S'.
The output power of the laser beam is set under the second condition that it is equal to or lower than the Curie point. At this time, the output power of the light beam is set so that the shape of the low temperature region becomes substantially crescent as shown in FIG. 13B and the shape of the high temperature region becomes substantially elliptical.

Then, the temperature of the high temperature region is the switch layer S '.
Above the Curie point, the magnetic domain of the switch layer S ′ disappears, that is, the coercive force becomes zero and the exchange coupling force between the reproducing layer P ′ and the recording layer R ′ becomes weak. At the same time, when a reproducing magnetic field H _r is applied from the outside as shown in FIG.
The magnetization direction of the reproducing layer P ′ having a small coercive force is aligned with the direction of the reproducing magnetic field H _r .

Therefore, the high-temperature area serves as a mask area in which the recording information of the recording layer R'cannot be read, and the recording information of the recording layer R'can only be read from the crescent-shaped low-temperature area in the light spot. Even at this time, since the temperature in the light spot does not exceed the Curie temperature T _CR ′ of the recording layer R ′, the information recorded on the recording layer R ′ is not erased.

Due to the functions of the low temperature region and the high temperature region (mask region) described above, the reproduction of information on the recording layer R'can only be performed from the low temperature region within the light spot. In other words, the low temperature region functions as a window region for information reproduction,
The size of the light spot can be reduced substantially,
Information having a spatial frequency higher than the physical spatial frequency of the light spot can be reproduced. That is, super-resolution reproduction in the time axis direction of the magneto-optical disk can be performed.

[0016]

However, in the super-resolution reproduction using the magneto-optical disk 1P of the prior art, a magnet for applying the reproduction magnetic field H _r is required, which complicates the apparatus configuration and reduces the size. There was a problem that could not be achieved.

Further, in the mask region, the reproducing layer P '
A reproducing magnetic field H _r is applied to the magnetic field, and its magnetization direction is aligned with the reproducing magnetic field. Therefore, in the boundary portion between the low temperature region and the mask region, the magnetization direction may change abruptly, and in this case, the Kerr rotation angle in the reflected light of the reproduction light changes abruptly in the boundary portion. It will be. As a result, the reproduction RF corresponding to the recording mark
The waveform changes abruptly, which causes a problem that the symmetry of the waveform is lost and the waveform is greatly distorted.

Therefore, the present invention has been made in view of the above problems, and an object thereof is to simplify the apparatus configuration by eliminating the need for a reproducing magnetic field, and further to prevent the reproduced RF waveform from being distorted. An object of the present invention is to provide a magneto-optical recording medium and a magneto-optical recording medium reproducing apparatus capable of resolution reproduction.

[0019]

[0020]

[Means for Solving the Problems ]
Therefore, the magneto-optical recording medium of the invention according to claim 1 is an information recording medium.
As a magneto-optical layer for recording, from room temperature to its Curie temperature.
When information is recorded while maintaining the perpendicular magnetization state between at
In both cases, the Curie temperature is continuous in the thickness direction.
Side that changes with time and is irradiated with a predetermined reproduction light
The Curie temperature of the surface of the
It is configured to include only one magneto-optical layer having a temperature lower than the Curie temperature .

[0021]

[0022]

The invention described in claim 3 is the invention according to claim 1 or 2.
A magneto-optical recording medium reproducing apparatus for reproducing the recorded information on the magneto-optical recording medium according to claim 1, wherein reproduction light irradiating means for irradiating the magneto-optical recording medium with reproduction light such as a laser and the like on the magneto-optical recording medium. The temperature of the magneto-optical layer on the side of the irradiation surface corresponding to the mask region is equal to or lower than the highest Curie temperature in the magneto-optical layer, and more than the Curie temperature of the surface on the irradiation surface side of the magneto-optical layer, Alternatively, reproduction for controlling the output power of the reproduction light such that the temperature is equal to or lower than the Curie temperature of the surface on the irradiation surface side, and is a temperature at which the magnetization on the irradiation surface side in the magneto-optical layer is substantially disappeared. An output control unit and a reproduction unit that receives reflected light of the reproduction light from the irradiation range of the reproduction light on the magneto-optical recording medium and reproduces the recorded information are configured.

[0024]

[0025]

[0026]

[0027]

According to the magneto-optical recording medium of the present invention as set forth in action] claim 1, at the time of reproduction, the information recording layer of the magneto-optical layer of
Magneto-optical recording medium comprising viewed, the temperature of the magneto-optical layer of irradiated surface side corresponding to the mask region is the highest temperature of not higher than the Curie temperature of the magneto-optic layer, a predetermined reproduction light in the magneto-optical layer The temperature is equal to or higher than the Curie temperature of the surface on the irradiation surface side or equal to or lower than the Curie temperature of the surface on the irradiation surface side of the predetermined reproduction light, which is a temperature at which the magnetization on the irradiation surface side of the magneto- optical layer is substantially disappeared. Is irradiated with the reproduction light.

Then, the magnetization near the irradiation surface side of the magneto-optical layer corresponding to the mask region disappears or disappears substantially. As a result, the mask area becomes an area in which the print information cannot be read.

Therefore, since the information can be read only from a portion other than the mask area within the reproduction light irradiation range,
So-called super-resolution reproduction is possible without applying a reproduction magnetic field. In addition, there is only one magneto-optical layer for information recording.
Therefore, the manufacturing process of the magneto-optical recording medium can be simplified.
it can.

[0030]

[0031]

[0032]

[0033]

[0034]

[0035]

According to the third aspect of the present invention, the reproducing light irradiation means irradiates the magneto-optical recording medium according to the second or third aspect with the reproducing light. At this time, the reproduction output control means is configured such that the temperature of the magneto-optical layer on the irradiation surface side corresponding to the mask region becomes equal to or lower than the highest Curie temperature in the magneto-optical layer, and the irradiation surface of the predetermined reproduction light on the magneto-optical layer is irradiated. To a temperature not lower than the Curie temperature of the side surface or not higher than the Curie temperature of the surface on the irradiation surface side of the predetermined reproduction light and substantially eliminating the magnetization on the irradiation surface side in the magneto-optical layer. The output power of the reproduction light is controlled.

Then, the reproducing means reproduces the recorded information by receiving the reflected light of the reproducing light from the irradiation range of the reproducing light on the magneto-optical recording medium. Therefore, the magnetization in the vicinity of the irradiation surface side of the magneto-optical layer corresponding to the mask area disappears or substantially disappears, so that the mask area becomes an area in which the recording information cannot be read.

Therefore, the information can be read only from a portion other than the mask area in the reproduction light irradiation range.
So-called super-resolution reproduction is possible without applying a reproduction magnetic field.

[0039]

[0040]

[0041]

[0042]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the present invention will be described with reference to the drawings. In the following actual施例, magneto-optical recording medium, a case of using a disk-shaped magneto-optical disk. (I) Device Configuration First, a magneto-optical disk reproducing device for reproducing recorded information from a magneto-optical disk according to each of the following embodiments will be described with reference to FIGS. 1 and 2.

First, the structure of the magneto-optical disk reproducing apparatus will be described with reference to FIG. In the magneto-optical disk reproducing apparatus shown in FIG. 1, not only reproduction of the recording signal of the magneto-optical disk 1 but also recording data from the outside can be processed and recorded on the magneto-optical disk 1.

The magneto-optical disk reproducing apparatus S shown in FIG.
Under the control of a control microcomputer MC, which will be described later, it has a disk drive unit DS for rotating and driving the magneto-optical disk 1, a laser diode (not shown), an actuator, a deflection beam splitter, etc., and reproduces on the rotating magneto-optical disk 1. A light beam B such as a laser beam is emitted as light, and this light beam B is reflected and returned in the magneto-optical layer of the magneto-optical disk 1 by slightly rotating the deflecting surface due to the magnetic Kerr effect. Signal component of RF (Radio Frequency)
In order to demodulate the optical pickup 2 that outputs as a signal, the RF amplifier that amplifies the RF signal output from the optical pickup 2, and the modulated signal corresponding to the record information from the amplified RF signal, partial response and Viterbi decoding are performed. It has a decoder or the like for processing, processes the RF signal, converts it into a reproduction signal, and outputs it to the control microcomputer MC, which will be described later, and the ambient temperature at the position of the optical pickup 2, and measures the ambient temperature signal. The output of the light beam B is controlled via the laser diode included in the optical pickup 2 under the control of the temperature sensor 4 that outputs to the control microcomputer MC and the control microcomputer MC that is based on the temperature signal from the temperature sensor 4. Laser drive circuit 3 and control microcomputer MC
N for encoding the recording data input from the outside via the
RZ1 (Non Return-to-Zero change-on-ones recordin
g) A recording processing unit RS that includes a magnetic head drive circuit that drives a magnetic head 5 described later based on the outputs of the encoder and the NRZ1 encoder, and that controls the magnetic head 5 described later for information recording based on the recording data. Under the control of the recording processing unit RS, in recording information on the magneto-optical disc 1, a magnetic head 5 for applying a predetermined magnetic field to the information recording portion of the magneto-optical disc 1 and a magneto-optical disc reproducing apparatus S.
And a control microcomputer MC for controlling the whole.

Further, the disk drive section DS includes a spindle drive circuit 6 for controlling the rotation of the spindle motor 7 under the control of the control microcomputer MC, and a spindle for rotationally driving the magneto-optical disk 1 under the control of the spindle drive circuit 6. And a motor 7.

In the actual magneto-optical disk reproducing apparatus S, in addition to the above-mentioned configuration, servo control such as focus servo and tracking servo is performed on the optical pickup 2, and the spindle motor 7 is rotated by a spindle. Although it has a servo control unit for performing servo control such as servo, it is not shown in FIG. 1 for simplification of description.

When reproducing the recorded information in the magneto-optical disk reproducing apparatus S, first, based on the ambient temperature of the optical pickup 2 detected by the temperature sensor 4, the relationship between the ambient temperature and the output of the light beam B is determined. The output of the light beam B is controlled so as to have the relationship shown in FIG. The output of the light beam B is finely controlled by referring to the BER (Bit Error Rate) at that time while executing the reproducing operation by the reproducing operation described in each of the embodiments described later.

More specifically, first, the output of the light beam B is controlled so as to have the relationship between the ambient temperature and the output of the light beam B shown in FIG. 2, and then the reproducing operation of each of the following embodiments is executed. To be done. Then, when the BER during reproduction becomes larger than 10 ⁻⁶ units, the output of the light beam B is changed so that the BER becomes 10 ⁻⁶ units or less. In the method of changing the output of the light beam B, the output of the light beam B having the relationship shown in FIG. 2 is used as a reference value, and the output is changed every 0.05 mW up to 0.4 mW above and below the reference value. However, at this time, the maximum output is 2.4 mW. Then, the output of the light beam B when the BER finally becomes the minimum is set to the optimum value of the output of the light beam B.

Here, the magneto-optical disk reproducing apparatus S of FIG.
The recording operation by is the same as that of the conventional technique, and thus detailed description thereof is omitted. Next , the structure of the magneto-optical disk of the present invention and the reproducing operation thereof will be described. (II) First Reference Example First, a first reference example related to the present invention will be described with reference to FIGS. 3 to 5.

First, the structure of the magneto-optical disk according to the first reference example will be described with reference to FIG. First shown in FIG.
The magneto-optical disk 1 according to the reference example has a substrate 10, which is the main body of the magneto-optical disk 1, a dielectric protective layer 11 for protecting the magneto-optical layer, and a room temperature, which will be described later. By exchange coupling with the recording layer 13, the recording layer 13
Holds the same magnetization direction (recording mark) as
At the time of reproduction, the reproducing layer 12 serving as a mask layer in which the magnetization of the recording layer 12 is not transferred by being heated to the Curie temperature or higher, the recording layer 13 in which information is recorded in the direction of magnetization in the perpendicular magnetization state, A dielectric protective layer 14 for protecting the magnetic layer and a resin protective layer 15 formed by a 2P overcoat or the like for coating and protecting the magneto-optical disk 1 are laminated. In the above structure, it is the reproducing layer 12 and the recording layer 13 that are substantially involved in the reproducing operation, and these are collectively referred to as a magneto-optical layer.

Next, the function, composition and film thickness of each layer will be described. The substrate 10 functions to support the entire magneto-optical disk 1, and as its material, transmits the light beam B,
Moreover, a material that is difficult to be refracted is used, and specifically, glass or the like is used. Further, the thickness thereof has sufficient strength to support the magneto-optical disk 1, and the light beam B
Any film thickness that does not affect the transmission of Specifically, it is about 0.6 to 1.2 mm.

The dielectric protective layers 11 and 14 are formed by the light beam B
And also protects the magneto-optical layer described later. The property of this film is that it should be transparent so as not to affect the transmission of the light beam B and have a dense composition that does not allow moisture and the like to pass through. As a composition having this property, SiN _x , AlN, Ta ₂ O ₅ or the like can be used. The film thickness is required to be thick enough to resist aging and oxidation (for example, about 20 nm), and is a thickness that does not affect the heat conduction property or the light transmission property. It is preferable that the thickness is (for example, about 100 nm) or less.

The recording information of the recording layer 13 is transferred at room temperature to the reproducing layer 12, and the temperature of the reproducing layer 12 is raised when the temperature is raised above the Curie temperature (hereinafter referred to as T _C1 ) of the reproducing layer 12 during reproduction. The magnetic domain of the part disappears, and the heated part operates as a mask region from which information cannot be read. At this time,
The reached temperature of the mask region (hereinafter referred to as the reproduction temperature) at the time of temperature rise must be lower than the Curie temperature of the recording layer 13 (hereinafter referred to as T _C2 ) in order to hold the recorded information of the recording layer 13. I won't. Further, in the temperature decreasing process accompanying the movement of the magneto-optical disk 1, the recording information of the recording layer 13 (recording layer 1
The magnetization of 3) has to be transferred again. From the above conditions, the Curie temperature T _C2 and the coercive force (hereinafter, referred to as H _C1 ) of the reproducing layer 12 must satisfy the following conditions.

T _C1 <T _C2 (1) and H _C1 <H _C2 (2) near the reproduction temperature, where H _C2 is the coercive force of the recording layer 13.

As the composition and film thickness of the reproducing layer 12 suitable for the above conditions, Tb ₂₀ Fe ₈₀ [at%] (40 nm (film thickness,
The same shall apply hereinafter)), Tb ₂₀ (Fe ₉₅ Co ₅ ) ₈₀ [at%] (4
0 nm) or the like is used. Regarding the film thickness, Tb ₂₀
In the case of Fe ₈₀ , a range of 10 nm to 60 nm is suitable.

Here, the numerical values in the composition formula represent the atomic ratio of the two alloys and are referred to as atomic percentages. For example, in the notation A _n B _m [at%], n + m = 100, and this formula shows that this material is composed of n% A atoms and m% B atoms in the total number of atoms. means.

As the composition of the reproducing layer 12, DyFeCo, GdTbFe or the like can be used in addition to the above composition. The recording layer 13 functions to hold recorded information. The nature of this film is that it is a magnetic material having perpendicular magnetization, and its Curie temperature T _C2 is lower than the maximum temperature that can be reached by irradiation with the light beam B during recording, and it is necessary to once eliminate the magnetic domain at the maximum temperature. . Further, during reproduction, it is necessary that the recorded information (direction of magnetization) does not disappear even when part of the irradiation range of the optical beam B of the magneto-optical disk 1 (mask area) reaches the reproduction temperature. From the above conditions, it is necessary for the Curie temperature T _C2 and coercive force H _C2 of the recording layer 13 to satisfy the conditions of the above formulas (1) and (2).

The composition of the recording layer 13 suitable for the above conditions and
The thickness of the reproducing layer 12 is Tb.₂₀Fe₈₀(At%
 ] (40 nm), Tb₂₀(Fe₉₀Co
_Ten)₈₀[At%] (40 nm) or the like is used for the reproducing layer 12
And then Tb₂₀(Fe₉₅Co_Five) ₈₀[At%] (40 nm)
When used, (Gd₂₀Tb₈₀)_{twenty three}(Fe₉₀Co_Ten)
₇₇[At%] (40 nm) or the like is used. Also, regarding the film thickness
Then, Tb₂₀(Fe₉₀Co_Ten)₈₀In case of, 20nm
A range of -60 nm is suitable.

As the composition of the recording layer 13, in addition to the above composition, GdDyFeCo or the like can be used.
Next, a reproducing operation of recorded information using the magneto-optical disk 1 shown in FIG. 3 will be described with reference to FIGS.

In FIG. 4B, the recording information (hereinafter referred to as recording mark M) recorded on the recording layer 13 corresponds to the upward magnetization in the recording layer 13. Then, in the room temperature portion (the portion where the light beam B is not irradiated), the recording mark M of the recording layer 13 is transferred to the reproducing layer 13, and the recording mark corresponding to the recording mark M of the recording layer 13 is also formed in the reproducing layer 13. Has been formed.

At the time of reproducing information, light which is reproduction light
The output power of the beam B is output by the laser drive circuit 3.
Beam irradiation area on the magneto-optical disk (hereinafter referred to as optical spot
To B _PSay. ) Maximum temperature (corresponding to the regeneration temperature
R) T_HBut, T_C1<T_H<T_C2 Is set. And output power like this
The light beam B set with the
When the disk 1 is irradiated, the magneto-optical disk 1 moves along with it.
As shown in Fig. 4, the front part of the light spot is
Temperature T_FIs T_F<T_C1Area (hereinafter referred to as low temperature area)
U ) Is formed, and the temperature T
_BIs T_C1<T_BArea (hereinafter, high temperature area (mask area
Area A_M). ) Can be done. At this time, the shape of the low temperature region
Shows a crescent shape as shown in FIG._Mof
The output power of the light beam is set so that the shape is approximately elliptical
To be done.

In the low temperature region, the recording mark M of the recording layer 13 is transferred to the reproducing layer 12 until the temperature reaches the Curie temperature T _C2 of the reproducing layer 12 (see FIG. 4B). Then, the Kerr effect based on the direction of the magnetization of the reproducing layer 12 by the transfer causes the polarization plane of the light beam irradiated on the recording mark portion to rotate, and the light beam having the rotated polarization plane and the portion other than the recording mark M ( The light beam (which has a different magnetization direction from that of the information recording portion) (having a different polarization plane than the light beam applied to the recording mark M due to the Kerr effect) is polarized and separated by the optical pickup 2. By doing so, the information is reproduced.

Next, as the magneto-optical disk 1 moves,
The temperature of the low temperature region is increased while moving to become the mask region (see FIG. 4A). At this time, in the mask region, the reproduction temperature T _H becomes T _C1 <T _H in comparison with the Curie temperature T _C1 of the reproduction layer 12, so that as shown in FIG. The magnetization disappears. Therefore, in the mask area, the magnetization of the recording layer 13 is not transferred to the reproducing layer 12,
The information recorded in the storage layer 13 corresponding to the mask area cannot be read. In other words, the mask area is an area from which information cannot be read. Even at this time, the temperature in the light beam irradiation region does not exceed the Curie temperature T _{C2 of} the recording layer 13, so that the information recorded in the recording layer 13 is not erased.

When the magneto-optical disk 1 is further moved and the light beam B is no longer irradiated, the temperature of the mask area A _M is lowered, and when the temperature becomes the Curie temperature T _C1 or less, the above expression is obtained near the reproducing temperature. Because of the relationship (2), the recording mark M of the recording layer 13 is retransferred to the reproducing layer 12, and the recording mark M similar to that of the recording layer 13 is also formed on the reproducing layer 12.

The low temperature region and the mask region A _M described above
With the above function, the information stored in the recording layer 13 can be reproduced only from the low temperature region in the light spot. That is, since the low temperature region functions as a window region for information reproduction, the size of the light spot can be substantially reduced, and the magneto-optical disc 1 can be applied without applying the reproduction magnetic field H _r.
That is, so-called super-resolution reproduction in the time axis direction of can be performed.

Here, in FIG. 5, regarding the waveform of the reproduction RF signal corresponding to the recording mark M, the case of information reproduction using the magneto-optical disk 1 of the first embodiment which does not require a reproduction magnetic field and the reproduction magnetic field are shown. The result of comparison with the case of information reproduction using a conventional magneto-optical disk that requires H _r is shown.

As shown in FIG. 5A, the conventional technique
The mask area A_MWith respect to the reproducing magnetic field H_rIs applied
(See FIGS. 5 (a) and (i))
Area A _MAt the boundary part of the
May occur in the reflected light of the reproduction light.
The car rotation angle changes rapidly at the boundary,
The reproduced RF waveform corresponding to the peak M changes rapidly (Fig. 5).
(See (a) and (ii)), the symmetry of the waveform is lost and it is greatly distorted.
It will be.

On the other hand, as shown in FIG. 5B, the first
In the case of information reproduction using the magneto-optical disk 1 of the embodiment, since the reproduction magnetic field H _r is not applied to the mask area A _M (see FIGS. 5B and 5I), the low temperature area and the mask area A _At the boundary with _M , the direction of magnetization does not change rapidly, but changes smoothly and continuously with increasing temperature. Therefore, the Kerr rotation angle in the reflected light of the reproduction light does not change abruptly, and the reproduction RF waveform corresponding to the recording mark M also changes continuously (FIG. 5 (b) (i
i)), the symmetry of the waveform is not lost. Therefore, a reproduced signal with little noise can be obtained without distortion of the reproduced signal.

According to the first reference example described above, the structure of the magneto-optical disk can be simplified, and so-called super-resolution reproduction can be performed without applying the reproduction magnetic field Hr. Therefore, the structure of the magneto-optical disk reproducing device can be simplified.

Further, since the magnetization direction of the reproducing layer 12 is not abruptly changed by the reproducing magnetic field H _r , the reproducing RF waveform corresponding to the recording mark M is not distorted and a good reproducing signal with less noise can be obtained. Obtainable.

In the above-mentioned first reference example, the temperature of the reproducing layer 12 corresponding to the mask area AM is set to a reproducing temperature equal to or higher than the Curie temperature TC1, so that the magnetization of the reproducing layer 12 corresponding to the mask area AM is magnetized. However, the present invention is not limited to this, and the temperature of the reproducing layer 12 corresponding to the mask area AM is equal to or lower than the Curie temperature TC1 and corresponds to the mask area AM.
Of the light beam B so that the temperature at which the magnetization of the
May be controlled.

More specifically, at the reproduction temperature TH, a change in the reproduction RF signal based on a change in the Kerr rotation angle in the reflected light of the light beam B caused by a change in the magnetization direction of the reproduction layer 12 is predetermined in the reproduction processing section PS. The temperature is set so that the magnetization of the reproducing layer 12 is reduced so that the value becomes equal to or lower than the threshold of. By doing so, the magnetization of the reproducing layer 12 is substantially lost, and the same effect as that of the first reference example can be obtained. (III) Embodiment Next, actual施例that corresponds to the present invention will be described with reference to FIGS.

[0073] In the first reference example, although the structure of a magneto-optical layer has a two-layer structure of the reproduction layer 12 and recording layer 13, in the real施例, the magneto-optical layer is a single layer structure, the thickness direction Is configured so that the Curie temperature continuously changes.

[0074] First, the structure of the magneto-optical disk according to the actual施例be described with reference to FIG. Magneto-optical disc 20 according to the shown to actual施例in Figure 6, in order from the irradiation side of the light beam B, a main body serving as the substrate 21 of the magneto-optical disk 20, a dielectric protection for protecting the magneto-optical layer 23 described later Due to the difference in the direction of perpendicular magnetization between the layer 22 and room temperature, the recording mark M
And the amount of the contained element (for example, Co) for changing the Curie temperature continuously changes in the thickness direction so that the Curie temperature continuously changes in the thickness direction ( 6B), a dielectric protective layer 24 for protecting the magneto-optical layer 23, and a 2P overcoat for protecting the magneto-optical disk 20 by coating. And the like, and a resin protective layer 25 formed by the above. In the above structure, it is the magneto-optical layer 23 that substantially participates in the reproducing operation.

Further, in the magneto-optical layer 23, as shown in FIG.
As shown in (b), the Curie temperature on the irradiation surface side (substrate 21 side) irradiated with the light beam B is lower than the Curie temperature on the surface side other than the irradiation surface (resin protective layer 25 side). The contained element for changing the temperature is the substrate 2
It is configured to decrease on the first side and increase on the resin protective layer 25 side.

Next, the function, composition and film thickness of each layer will be described. Since the substrate 21 and the dielectric protection layers 22 and 24 are the same as those in the first reference example, detailed description will be omitted.

The recording mark M is held at room temperature in the magneto-optical layer 23, and at the time of reproduction, the vicinity of the surface of the magneto-optical layer 23 on the side of the substrate 21 is the Curie temperature (hereinafter T) of the surface on the side of the substrate 21.
_{Called C3} . ) When the temperature is raised above, the heated portion operates as a mask area from which information cannot be read. At this time,
The reproduction temperature T _H is set to the magneto-optical layer 2 in order to hold the recorded information.
3 near the surface of the resin protective layer 25 side Curie temperature (hereinafter,
It is called T _C4 . ) Must be lower. Further, in the temperature lowering process accompanying the movement of the magneto-optical disk 20, the recording mark M held on the resin protective layer 25 side of the magneto-optical layer 23 must be transferred again to the surface of the magneto-optical layer 23 on the substrate 21 side. From the above conditions, the Curie temperatures T _C3 and T _{C4 of} the magneto-optical layer 23, the coercive force (hereinafter referred to as H _C3 ) near the surface of the magneto-optical layer 23 on the substrate 21 side, and the magneto-optical layer 2 are obtained.
Regarding the coercive force (hereinafter, referred to as H _C4 ) near the surface of No. 3 on the resin protective layer 25 side, it is necessary to satisfy the following conditions.

T _C3 <T _C4 (3) and near the reproduction temperature, H _C3 <H _C4 (4) The composition and film thickness of the magneto-optical layer 23 suitable for the above conditions are Tb ₂₀ (Fe _{100- x} Co _x ) ₈₀ [at%] (90n
m), Gd ₂₆ (Fe _100-x Co _x ) ₇₄ [at%] (90n
m) etc. are used. Here, x is variable in the thickness direction of the magneto-optical layer 23. Further, regarding the film thickness, even when the temperature in the vicinity of the surface of the magneto-optical layer 23 on the substrate 21 side is raised to the Curie temperature T _C3 or higher during reproduction, the vicinity of the surface of the magneto-optical layer 23 on the resin protective layer 25 side is reached. Is the Curie temperature T
_The recording mark M is set to _C4 or less so that the recording mark M does not disappear (the magnetization does not disappear).

More specifically, Tb ₂₀ (Fe _100-x Co
_{In the case of x} ) ₈₀ [at%], the range is 30 to 150 nm, and in the case of Gd ₂₆ (Fe _100-x Co _x ) ₇₄ [at%], the range is 30 to 150 nm.

Here, as the magneto-optical layer 23, Gd ₂₆ (Fe
Cobalt (C when _100-x Co _x ) ₇₄ [at%] is used
FIG. 7 shows the relationship between the content of o) (size of x) and the Curie temperature. As is clear from FIG. 7, cobalt (C
If the content of o) is large, the Curie temperature rises. Therefore, the position in the thickness direction of the magneto-optical layer 23 and cobalt (Co)
6B, the Curie temperature of the magneto-optical layer 23 is changed monotonously and continuously in the thickness direction, and the substrate 2 of the magneto-optical layer 23 is changed.
The Curie temperature T _C3 near the surface on the first side can be made lower than the Curie temperature T _C4 near the surface on the resin protective layer 25 side. Next, regarding the reproducing operation of the recorded information using the magneto-optical disk 20 shown in FIG. This will be described with reference to FIG.

In FIG. 8B, the recording mark M recorded on the magneto-optical layer 23 corresponds to the upward magnetization in the magneto-optical layer 23. Then, in the room temperature portion (the portion where the light beam B is not irradiated), the recording mark M of the magneto-optical layer 23 is transferred to the surface of the magneto-optical layer 23 on the substrate 21 side, and the surface of the magneto-optical layer 23 on the substrate 21 side. A recording mark M is formed on the.

[0082] During reproduction of the information, the output power of the light beam B is the reproduction light, the laser drive circuit 3, so that the regeneration temperature T _H in the light spot B _P becomes the T _C3 <T _H <T _C4 Is set to. Then, when the light beam B having the output power thus set is irradiated from the substrate 21 side, as the magneto-optical disk 20 moves, as shown in FIG. That temperature T _F is T
A low temperature region similar to that of the first embodiment where _F <T _C3 is formed, and a high temperature region (mask region A _M ) where the temperature T _B is T _C3 <T _B is formed in the rear part of the light spot. At this time,
Similar to the first embodiment, the output power of the light beam is set so that the low temperature region has a substantially crescent shape and the mask region A _M has a substantially elliptical shape.

In the low temperature region, the recording mark M remains in the magneto-optical layer 2 until the temperature reaches the Curie temperature TC3.
3 is formed on the substrate 21 side surface (see FIG. 8B). Then, the Kerr effect based on the magnetization direction of the recording mark M causes the plane of polarization of the light beam irradiated to the recording mark M portion to rotate, and information is reproduced by the same operation as in the first reference example.

Next, as the magneto-optical disk 20 moves, the temperature of the low temperature area is increased while moving to become the mask area A _M (see FIG. 8A). At this time, in the mask region A _M , the reproduction temperature T _H becomes T _C3 <T _H , as compared with the Curie temperature T _C3 of the surface of the magneto-optical layer 23 on the substrate 21 side, and thus FIG. As shown in, the magnetization near the surface of the magneto-optical layer 23 on the substrate 21 side disappears. Therefore, in the mask area A _M , the recording mark M is not formed on the surface of the magneto-optical layer 23 on the side of the substrate 21.
The information corresponding to can no longer be read. Even at this time, the temperature in the irradiation region of the light beam does not exceed the Curie temperature T _C4 of the surface of the magneto-optical layer 23 on the resin protective layer 25 side. In the vicinity of the surface, the recording mark M continues to be held as it is.

When the magneto-optical disk 20 is further moved and the light beam B is no longer irradiated, the mask area A _M is cooled, and when the temperature becomes the Curie temperature T _C3 or less, the above formula is obtained near the reproducing temperature. Due to the relationship (4), the recording mark M remaining in the vicinity of the surface of the magneto-optical layer 23 on the resin protective layer 25 side is retransferred to the surface of the magneto-optical layer 23 on the substrate 21 side, and The same recording mark M as the surface of the magneto-optical layer 23 on the resin protective layer 25 side is also formed on the surface of the substrate 21 side.

The low temperature region and the mask region AM described above
With the above function, reproduction of information on the magneto-optical layer 23 is performed only from a low temperature region within the light spot, and so-called super-resolution reproduction in the time axis direction of the magneto-optical disk 20 can be performed as in the first reference example. Of.

[0087] According to the actual施例described above, it is possible to simplify the structure of a magneto-optical disc, without applying the reproducing magnetic field Hr, it is possible to so-called super-resolution reproduction. Therefore, the structure of the magneto-optical disk reproducing device can be simplified.

Further, since the magnetization direction of the surface of the magneto-optical layer 23 on the side of the substrate 21 is not abruptly changed by the reproducing magnetic field Hr, the reproducing RF waveform corresponding to the recording mark M is not distorted and noise is generated. A small number of good reproduction signals can be obtained. Furthermore, the number of magneto-optical layers 23 for recording information is only one.
Therefore, the manufacturing process of the magneto-optical disk can be simplified.
it can.

[0089] In the above actual施例, by the temperature of the surface of the substrate 21 of the magneto-optical layer 23 corresponding to the mask area AM and its Curie temperature TC3 above the regeneration temperature, corresponding to the mask region AM Substrate 2 of magneto-optical layer 23
Although the magnetization in the vicinity of the surface on the 1st side is completely disappeared, the present invention is not limited to this. As in the first reference example, the mask region A
The temperature of the surface of the magneto-optical layer 23 corresponding to M on the substrate 21 side is equal to or lower than the Curie temperature TC3, and the magnetization in the vicinity of the surface of the magneto-optical layer 23 corresponding to the mask region AM on the substrate 21 side is substantially. The output of the light beam B may be controlled so that the temperature of the light beam B disappears. Also in this case, the same effect as above you施例is obtained. (IV) Second Reference Example Next, a second reference example related to the present invention will be described with reference to FIGS. 9 to 12.

[0090] In previous first reference example及BiMinoru施例either abolish the magnetization in the mask area AM, or by substantially equivalent to the disappearance reproduction of information from the mask area AM I decided not to do it, but the second visit
In considered example, rather than to eliminate the magnetization in the mask area AM, the heating reduces the squareness ratio of the mask area AM (squareness ratio (squareness)), the mask area AM by reducing the Kerr rotation angle Reproduction of information from is virtually prohibited.

First, the structure of the magneto-optical disk according to the second reference example will be described with reference to FIG. The magneto-optical disk 30 shown in FIG. 9 has a substrate 31, which is the main body of the magneto-optical disk 1, a dielectric protective layer 32 for protecting the magneto-optical layer, and a room temperature, which will be described later, in order from the irradiation side of the light beam B. The same recording mark M as that of the recording layer 34 is held by exchange coupling with the recording layer 34, and at the time of reproduction, the mask layer having a small Kerr rotation angle due to a decrease in the squareness ratio by being heated to a predetermined reproduction temperature or higher. And a recording layer 34 in which information is recorded according to the direction of magnetization in the perpendicular magnetization state.
A dielectric protective layer 35 for protecting the magneto-optical layer, and 2 for protecting the magneto-optical disk 30 by coating.
A resin protective layer 36 formed of P overcoat or the like is laminated. In the above structure, it is the reproducing layer 33 and the recording layer 34 that are magneto-optical layers that are substantially involved in the reproducing operation.

Next, the function, composition and film thickness of each layer will be described. The substrate 31, dielectric protective layer 32 and 35 is similar to that of the first reference example及BiMinoru施例, the explanation of the details is omitted.

When the recording mark M of the recording layer 34 is transferred at room temperature and the temperature is raised above a predetermined reproducing temperature T _H during reproduction, the reproducing layer 33 has a rectangular shape corresponding to the heated region. The ratio decreases, and the Kerr rotation angle of the light beam B with which the recording mark M in the area is irradiated becomes small. As a result, the temperature-increased area operates as a mask area A _{M in} which information cannot be substantially read. To do. At this time, the reproduction temperature T _H must be lower than the Curie temperature of the recording layer 35 (hereinafter referred to as T _C6 ) in order to hold the recording mark M of the recording layer 35. From the above conditions, it is necessary for the predetermined reproduction temperature T _H in the reproduction layer 33 to satisfy the following conditions.

T _H <T _C6 (5) In the magneto-optical disk 30 of the third embodiment, there is no correlation between the Curie temperature of the reproducing layer 33 and the Curie temperature of the recording layer 34. . In the heated region of the reproducing layer 33, the recording mark M does not disappear, and the Kerr rotation angle of the light beam B irradiated on the portion corresponding to the recording mark M becomes small.

Further, in order to reduce the squareness ratio and the Kerr rotation angle of the light beam B in the mask area A _M , the magnetic anisotropy of the reproducing layer 33 must be sufficiently small.

The composition of the reproducing layer 33 suitable for the above conditions and
The film thickness is Gd_{twenty four}(Fe₈₀Co ₂₀)₇₆[At%] (6
0 nm) or the like is used. Here, as the range of the film thickness,
20 to 100 nm is suitable. In addition, the content of Co
Therefore, in order to make the squareness ratio smaller than 1, it is 20 or
It is set to 60 [at%].

Here, as the reproducing layer 33, Gd ₂₄ (Fe
The relationship between the squareness ratio R and the Kerr rotation angle when ₈₀ Co ₂₀ ) ₇₆ [at%] (60 nm) is used will be described with reference to FIG. In FIG. 10, the horizontal axis represents the strength of magnetization and the vertical axis represents the Kerr rotation angle. Further, the squareness ratio R is represented by R = B / A or R = D / C by using "A" and "B" or "C" and "D" in FIG.

As is apparent from FIG. 10, when the squareness ratio R becomes smaller, the Kerr rotation angle also becomes smaller. In addition, in FIG.
As shown in the cases of 220 ° C. and 25 ° C., the higher the temperature, the smaller the squareness ratio, and therefore the smaller the Kerr rotation angle.

Next, as the reproducing layer 33, Gd ₂₄ (Fe ₈₀
Co ₂₀ ) ₇₆ [at%] (60 nm) squareness ratio R
The relationship between temperature and temperature will be described with reference to FIG. Figure 11
In, the horizontal axis represents the temperature and the vertical axis represents the squareness ratio. As is clear from FIG. 11, the squareness ratio R becomes approximately 1 at approximately 200 degrees or less. Therefore, in this temperature range, a Kerr rotation angle sufficient for reproducing information can be obtained. Further, when the angle is about 200 degrees or more, the squareness ratio R becomes small, so that the Kerr rotation angle also becomes small.

The relationship between the temperature and the squareness ratio in the magneto-optical disk 30 as shown in FIG.
It can be obtained by changing the sputtering gas pressure when forming the SiN layer as the dielectric protection layer 32 that protects the No. 3 layer. More specifically, the relationship shown in FIG. 11 is that the film forming pressure when forming the dielectric protective layer (SiN layer) 32 is 7 mTorr.
Obtained at.

The recording layer 34 has a function of holding recording information. As the property of this film, it is necessary to satisfy the same conditions as in the first reference example. Here, in the second reference example, since the recording mark M due to the magnetization of the reproducing layer corresponding to the mask area AM does not disappear even when the temperature is raised as described above, the coercive force of the recording layer 34 in the first reference example will be described. It is not necessary to satisfy the relationship as in Expression (2).

The composition of the recording layer 34 suitable for the above conditions and
The thickness of the reproducing layer 33 is Gd._{twenty four}(Fe₈₀Co
₂₀)₇₆When [at%] (60 nm) is used, Tb
₂₀(Fe ₉₀Co_Ten)₈₀[At%] (40 nm) etc. are used
It 20 nm to 60 nm is suitable for the film thickness range.
Is.

Next, the reproducing operation of recorded information using the magneto-optical disk 30 shown in FIG. 9 will be described with reference to FIG. The rotation arrow of the reproducing layer 33 in FIG. 12B indicates the light beam B irradiated to the portion of the recording mark M of the reproducing layer 33 corresponding to the recording mark M of the recording layer 34. The magnitude of the car rotation angle is shown.

In FIG. 12B, the recording mark M recorded on the recording layer 34 corresponds to the upward magnetization in the recording layer 34. Then, in the room temperature portion (the portion not irradiated with the light beam B), the recording mark M of the recording layer 34 is transferred to the reproducing layer 33, and the recording mark M corresponding to the recording mark M of the recording layer 13 is also recorded in the reproducing layer 33. Are formed.
Furthermore, since the squareness ratio R is approximately 1 at room temperature, the Kerr rotation angle also increases corresponding to each recording mark M of the reproducing layer 33.

[0105] During reproduction of the information, the output power of the light beam B is the reproduction light, the laser drive circuit 3, the regeneration temperature T _H in the light spot B _P is a range shown in FIG. 11, the above equation The temperature is set to satisfy the condition (5).
Then, the light beam B having the output power set in this way
When There is irradiated from the reproducing layer 33 side to the magneto-optical disk 30, along with the movement of the magneto-optical disc 30, as shown in FIG. 12 (a), the front portion of the light spot B _P its temperature T
_A low temperature region where _F becomes T _F <T _H is created, and the light spot B _P
A high temperature region (mask region A _M ) where the temperature T _B is T _H <T _B is formed in the rear portion of the. In this case, the shape of the low-temperature region 12 becomes crescent (a), the shape of the mask region A _M output power of the light beam B so as to be substantially oval is set.

In the low temperature region, the temperature is the reproduction temperature T _H.
Until the recording mark M is reached, a recording mark similar to the recording mark M on the recording layer 35 is formed on the reproducing layer 33 as well.
Also, the Kerr rotation angle corresponding to is increased (see FIG. 12B). Then, due to the change of the Kerr rotation angle of the light beam B with which the reproducing layer 33 is irradiated, information is reproduced by the same operation as in the first or second embodiment.

Next, as the magneto-optical disk 30 moves,
As a result, the low temperature region is moved and heated, and the mask region A_MWhen
(See FIG. 12A). At this time, the mask area A_MTo
The regeneration temperature T_HIs shown in FIG. 11 as described above.
Temperature range that satisfies the above condition (5)
It Therefore, as shown in FIG.
Mask area A_MThe squareness ratio R is small in the part corresponding to
And accordingly, the Kerr rotation angle in the light beam B
Also becomes smaller. Therefore, due to this decrease in car rotation angle,
A change in the reproduction RF signal causes a change in the reproduction processing section PS to a predetermined level.
The value is below the threshold, and the mask area A is substantially_M
The recording mark M of No. cannot be read. At this time
In addition, the temperature in the light beam irradiation area is set to the temperature of the recording layer 34.
Lee temperature T _C6Since it does not exceed the above, recording on the recording layer 34
The information provided is not erased.

[0108] By further magneto-optical disk 30 moves, the light beam B is no longer illuminated, the mask area A _M is lowered, if the temperature is less than the regeneration temperature T _H, squareness ratio of the readout layer 33 Becomes 1 again. Therefore,
When the reproduction layer 33 is irradiated with the light beam B in the next information reproduction, the Kerr rotation angle corresponding to the recording mark M of the reproduction layer 33 in the light beam B also becomes large, and the information reproduction becomes possible.

The low temperature region and the mask region A _M described above
With the function of, the reproduction of information on the recording layer 34 is performed by the light spot B.
Only from the low temperature region in _P , so-called super-resolution reproduction in the time axis direction of the magneto-optical disk 30 can be performed as in the first and second embodiments.

According to the second reference example described above, the structure of the magneto-optical disk can be simplified, and so-called super-resolution reproduction can be performed without applying the reproduction magnetic field Hr. Therefore, the structure of the magneto-optical disk reproducing device can be simplified.

Further, since the Kerr rotation angle of the reproducing layer 33 is not abruptly changed by the reproducing magnetic field H _r , the reproducing RF waveform corresponding to the recording mark M is not distorted, and a good reproducing signal with less noise is generated. Can be obtained.

The first and second reference examples so far
In the embodiments, the description has been made for the magneto-optical disk, but the present invention is not limited to this, and a so-called optical tape or the like in which the above-mentioned magneto-optical layer or the like is formed on a tape-shaped support is used. It can also be applied to a tape-shaped magneto-optical recording medium.

[0113]

[0114]

[0115]

[0116]

As described in the foregoing, according to the invention described in claim 1 or 3, or the magnetization of the irradiated surface side near the optical magnetic layer corresponding to the mask region is lost, or substantially disappear Therefore, the mask area is an area in which print information cannot be read.

Therefore, the information can be read only from a portion other than the mask area within the reproduction light irradiation range.
By providing only one magneto-optical layer for information recording, the structure of the magneto-optical recording medium can be simplified, and so-called super-resolution reproduction can be performed without applying a reproducing magnetic field. The configuration of the device can be simplified.

Further, since the magnetization direction of the reproducing layer is not abruptly changed by the reproducing magnetic field, the reproducing RF waveform corresponding to the recorded information is not distorted, and a good reproducing RF waveform with less noise can be obtained. it can. In addition, light for recording information
Since there is only one magnetic layer, the manufacturing process for magneto-optical recording media
Can be simplified.

[0119]

[0120]

[0121]

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a magneto-optical recording medium reproducing apparatus of an embodiment.

FIG. 2 is a diagram showing a relationship between ambient temperature and reproduction light power.

FIG. 3 is a diagram showing a structure of a magneto-optical recording medium of a first reference example.

FIG. 4 is a diagram showing a reproducing operation in the magneto-optical recording medium of the first reference example, (a) is a plan view in the vicinity of a light spot,
(B) is a sectional view.

FIG. 5 is a diagram showing a comparison of reproduced RF waveforms, (a)
(I) is a plan view of the vicinity of a light spot in the conventional technique,
(A) (ii) is a diagram showing a reproduction RF waveform corresponding to one recording mark in the prior art, (b) (i) is a plan view in the vicinity of a light spot in the present invention, (b) (ii) is the present invention 6 is a diagram showing a reproduction RF waveform corresponding to one recording mark in FIG.

[Figure 6] is a diagram showing the structure of a real施例magneto-optical recording medium, (a) shows the diagram showing the structure of a magneto-optical recording medium, (b)
FIG. 4 is a diagram showing the relationship between the film thickness (position in the thickness direction) and the cobalt content in the magneto-optical layer.

FIG. 7 is a diagram showing the relationship between the cobalt content and the Curie temperature.

8 is a diagram showing a reproducing operation of the magneto-optical recording medium of the real施例, (a) is a plan view of the vicinity of the optical spot, (b)
Is a sectional view.

FIG. 9 is a diagram showing a structure of a magneto-optical recording medium of a second reference example.

FIG. 10 is a diagram showing a relationship between a squareness ratio and a Kerr rotation angle.

FIG. 11 is a diagram showing a relationship between squareness ratio and temperature.

FIG. 12 is a diagram showing a reproducing operation in the magneto-optical recording medium of the second reference example, (a) is a plan view in the vicinity of a light spot,
(B) is a sectional view.

FIG. 13 is a diagram showing a conventional magneto-optical recording medium,
(A) is a figure which shows the structure of a magneto-optical recording medium, (b) is a top view near a light spot.

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshiro Saito 6-1, 1-1 Fujimi, Tsurugashima City, Saitama Pioneer Co., Ltd. (72) Inventor ▲ Takayoshi Kawachi 6-1, Fujimi, Tsurugashima City, Saitama Prefecture Number 1 Pioneer Co., Ltd. Research Institute (56) Reference JP-A-5-342670 (JP, A) JP-A-3-49058 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB) Name) G11B 11/105

Claims (3)

(57) [Claims] As claimed in claim 1] Information magneto-optical layer for recording, Wei perpendicular magnetization state between from room temperature to the Curie temperature
With lifting and while information is recorded, continuously changing the Curie temperature in the thickness direction
And the key on the surface on the irradiation surface side where the predetermined reproduction light is irradiated.
The Curie temperature is the Curie temperature of the surface other than the irradiation surface.
A magneto- optical recording medium comprising only one magneto-optical layer having a lower optical density . 2. The magneto-optical recording medium according to claim 1.
The content of the element that changes the Curie temperature is
A magneto-optical recording medium comprising a magneto-optical layer that continuously changes in the thickness direction of the recording medium. 3. The magneto-optical recording medium according to claim 1 or 2.
It is a magneto-optical recording medium reproducing device that reproduces the recorded information of
And a reproducing light irradiating means for irradiating the magneto-optical recording medium with reproducing light.
And the irradiation corresponding to the mask area on the magneto-optical recording medium
The temperature of the magneto-optical layer on the surface side is the maximum in the magneto-optical layer.
When the temperature is below the high Curie temperature,
The Curie temperature of the surface of the magnetic layer on the irradiation surface side or higher,
Alternatively, at a temperature equal to or lower than the Curie temperature of the surface on the irradiation surface side.
Therefore, the magnetization on the irradiation surface side of the magneto-optical layer is substantially
Output power of the reproduction light so as to reach a temperature at which
Playback output control means for controlling the read / write output, and a read output control means for controlling the read light on the magneto-optical recording medium.
Receiving the reflected light of the reproduction light to reproduce the recorded information
A reproducing device for reproducing a magneto-optical recording medium .