JP2001126331A - Magneto-optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure the stability of magneto-optical recording characteristics, the increase of the C-N ratio and the improvement of reproducing power margin in the case of a combination of magnetic ultra-resolution reproduction and the use of violaceous laser light or a combination of magnetic ultra-resolution reproduction and the use of a field lens having a numerical aperture N.A. >=0.7. SOLUTION: The magneto-optical recording medium has at least a reproducing layer 1, a recording layer 3 and a heat controlling layer 4 and attains magnetic ultra-resolution reproduction with violaceous laser light, that is, laser light of about 350-450 nm wavelength. The heat controlling layer 4 comprises one or more of metallic layers of Al, Ag, Au, Cu and an alloy containing one or more of these metals and has 30-100 nm thickness.

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 for reproducing information by a laser utilizing a magneto-optical effect,
In particular, the present invention relates to a magneto-optical recording medium having a reproducing layer, a recording layer, and a thermal control layer and performing magnetic super-resolution reproduction.

[0002]

2. Description of the Related Art As a rewritable high-density optical recording method, the magnetic layer of a magneto-optical recording medium is partially heated above the Curie temperature or compensation temperature by using thermal energy of a laser beam. Decrease or eliminate the coercive force,
For example, there is a method based on the basic principle that information domains are formed by reversing the direction of magnetization in the direction of a recording magnetic field applied from the outside, that is, information is recorded.

This magneto-optical recording medium is composed of a transparent substrate made of, for example, polycarbonate (PC), a dielectric layer made of, for example, silicon nitride or aluminum nitride, and a film made of, for example, a rare earth-transition metal alloy amorphous film. A recording magnetic layer having an easy axis of magnetization in a direction perpendicular to the surface and having excellent magneto-optical effect characteristics, a dielectric layer made of, for example, silicon nitride or aluminum nitride, a reflection layer made of, for example, aluminum, gold, or silver; A protective layer made of a curable resin is sequentially laminated.

The magneto-optical recording medium is irradiated with the above-described laser beam from, for example, the transparent substrate side, and the above-described information magnetic domain is formed on the magnetic layer, that is, information is recorded. Similarly, reproduction of recorded information is performed by irradiating a reproduction laser beam from the transparent substrate side and detecting a rotation angle of a polarization plane due to a magneto-optical effect due to the information magnetic domain in the magnetic layer, for example, the Kerr effect.

[0005] By the way, not only in the magneto-optical recording medium but also in optical disks such as digital audio and digital video disks, the linear recording density mainly depends on the S / D at the time of reproduction.
N, and the signal amount of the reproduced signal is
The period of the bit sequence of the recorded signal and the reproduction optical system
It depends on the laser wavelength and the numerical aperture of the objective lens. That is, the laser wavelength λ of the reproducing optical system and the numerical aperture N.P. A. The bit period f is determined by the optical detection limit, that is, the diffraction limit of light. That is, the optical detection limit bit period f is f = λ / 2 (N.
A. ).

Therefore, in order to increase the density of the magneto-optical recording medium, the laser wavelength λ of the reproducing optical system is shortened, and the numerical aperture N.sub. A. Need to be larger. Recently, a semiconductor laser capable of obtaining a blue-violet laser beam as a laser wavelength, that is, a laser beam having a wavelength of 350 nm to 450 nm has been developed. For example, recording on a magneto-optical recording medium using a blue-violet laser beam having a wavelength of about 400 nm by a GaN semiconductor laser is performed. Playback is about to take place. In addition, the numerical aperture of the objective lens N.P. A. Also regarding this N. A. Is realized, and a lens system with 0.7 or more is realized.
A. The magneto-optical recording / reproducing with respect to the magneto-optical recording medium is about to be performed using an objective lens having a value of 0.7 or more.

[0007] By making the optical detection limit smaller in this way, it is possible to increase the recording density. However, the recording density is further improved without being limited by the optical detection limit. There has been proposed a so-called magnetic super-resolution reproducing method capable of performing such a method.

In the magnetic super-resolution reproducing method, a magneto-optical recording medium having at least a reproducing layer and a recording layer is used, and a process of transferring information recorded on the recording layer having a high coercive force to the reproducing layer is performed. The recording information is reproduced by obtaining the rotation of the plane of polarization by the magneto-optical effect in the reproduction layer by irradiating the reproduction layer with the laser light and detecting the rotation, and in this case, the spot of the reproduction laser light Using the temperature distribution of the reproducing layer in the spot, part of the recorded information is raised or disappeared in the reproducing layer located in the spot, and for example, 1
The two information domains are read out in a limited manner, and can be reproduced within the optical detection limit bit period described above.

As such a magnetic super-resolution reproducing method,
For example, Japanese Patent Application Laid-Open Nos. 1-143041 and 1-14
No. 3042, the magneto-optical recording medium in these magnetic super-resolution reproducing methods has a reproducing layer, an intermediate layer, and a recording layer magnetically coupled to each other at room temperature. By expanding, contracting, or reversing the recording magnetic domain of the reproducing layer heated in the spot of the reproducing laser light at a high temperature, the interference between information marks at the time of reproduction is reduced, and the light diffraction limit or less. A method of increasing the linear recording density and the track recording density by enabling the reproduction at the period of 1 is proposed.

The magnetic super-resolution reproducing method is based on, for example, the reproducing method disclosed in Japanese Patent No. 2,839,783. That is, a so-called magnetic recording method in which only the recording bit (recording magnetic domain) at the center of the spot of the reproducing laser beam is read out. Center Aperture Detection-Magne
tic Super Resolution: hereinafter abbreviated as CAD-MSR).

A magneto-optical recording medium used in the conventional CAD-MSR reproducing method is, for example, a first dielectric film is formed on a transparent substrate 10 made of, for example, polycarbonate, as shown in FIG. 5, a reproduction layer 1, a reproduction auxiliary layer 2, an intermediate nonmagnetic layer 4, a recording layer 3, a second dielectric film 6, and a heat control layer 7 are formed, and a protective layer 8 is formed to cover the surface.

However, as shown in a schematic cross-sectional view of FIG. 9, the basic structure includes a reproducing layer 1, a reproducing auxiliary layer 2, a nonmagnetic intermediate layer (cutting layer) 4, and a recording layer 3. The reproduction layer 1 and the auxiliary reproduction layer 2 are constituted by magnetic layers having in-plane magnetic anisotropy.
The intermediate nonmagnetic layer 4 is formed of a magnetic layer having perpendicular magnetic anisotropy, and the intermediate nonmagnetic layer 4 is formed of a nonmagnetic material layer.

In the recording layer 3, a recording mark M recorded according to a recording signal, that is, an information magnetic domain is formed (recorded). In FIG. 9, white arrows schematically indicate the directions of magnetization.

CAD-MS for this magneto-optical recording medium
To read out or reproduce the recording by the R reproducing method, the reproducing laser beam L is applied to the optical lens system, that is, the objective lens 11.
In the heating section I generated by the irradiation of the laser beam, the magnetization of the reproduction auxiliary layer 2 is lost, and a reproduction window W, that is, an aperture is formed here. Through W, the reproducing layer 1 is magnetically coupled to the recording layer 3, and the recording mark M is transferred to the reproducing layer 1. The transferred recording mark causes a Kerr rotation of the reproduction laser light, and the Kerr rotation angle of the return light is detected. By doing so, the recording signal is read out.

[0015]

By the way, in the above-mentioned various magnetic super-resolution reproductions, as described above, a blue-violet laser beam having a wavelength of about 350 nm to 450 nm is used to lower the diffraction limit of the light. If you want to play that
It is possible to obtain a recording surface density twice or more that of the conventional magnetic super-resolution reproduction using a red laser beam having a wavelength of about 600 nm to 800 nm. However, according to this method, problems such as a decrease in stability of recorded information and a decrease in reproduction power margin occur.

Similarly, in magnetic super-resolution reproduction, as described above, N.I. A. When reproduction is performed with an objective lens of 0.7 or more, a conventional general N.I. A. Is 0.5 ~
1.5 of magnetic super-resolution reproduction with an objective lens of about 0.6
It is possible to obtain a recording surface density twice or more. However, in this method, problems such as deterioration of the ratio (C / N) between the carrier level and the noise level, deterioration of the stability of recorded information, and reduction of the reproduction power margin occur.

The present inventors have proposed a magnetic super-resolution reproduction using a conventional red laser beam in the case of a combination of the above-described various magnetic super-resolution reproduction and the use of a blue-violet laser beam. About 1/2 of the spot diameter at
When the constant laser power required for reproduction is used, the beam intensity at the center of the spot of the reproduction laser beam becomes extremely high, and the magnetic super-resolution reproduction and the aperture of the objective lens are reduced. Number N. A. To 0.
Even in the case of a combination of 7 or more,
The laser spot diameter is determined by the NA of the objective lens. A. Is 0.
Since the size is reduced to about 1 / 1.5 or less of about 5 to 0.6, the intensity of the central portion of the reproduction laser beam spot on the magneto-optical recording medium is not extremely high even in this case. Temperature rise is significant, as a result,
When performing magneto-optical recording / reproduction, the C / N
Degradation of the recorded information due to temperature rise, for example, erasure of recorded information at the Curie temperature, and instability of information recording due to repetition of reproduction due to high temperature. I found that a problem occurred.

In the present invention, based on this finding, a combination of magnetic super-resolution reproduction and the use of a blue-violet laser beam, or magnetic super-resolution reproduction and a numerical aperture N. A. Is 0.7 or more, the stability of magneto-optical recording characteristics, C / N
And a magneto-optical recording medium capable of improving the reproduction power margin.

[0019]

The magneto-optical recording medium according to the present invention has at least a reproducing layer, a recording layer, and a heat control layer, and has a blue-violet laser beam, that is, a wavelength of 350 nm to 450 nm.
A magneto-optical recording medium in which magnetic super-resolution reproduction is performed by a laser beam of about m, wherein the heat control layer is formed of aluminum Al, silver Ag, gold Au, 30 nm or more and 100 nm or less.
Any one of copper Cu and an alloy containing at least one of them
It is composed of more than one metal layer.

The magneto-optical recording medium according to the present invention has at least a reproducing layer, a recording layer, and a thermal control layer, and has a numerical aperture of an objective lens of 0.7 or more, and performs magnetic super-resolution reproduction. A magnetic recording medium, wherein the heat control layer has a thickness of 30 nm or more and 1
It is composed of at least one metal layer of aluminum Al, silver Ag, gold Au, copper Cu, and an alloy containing at least one of these metals having a thickness of 00 nm or less.

As described above, the magneto-optical recording medium according to the present invention can be manufactured by using a blue-violet laser beam by setting the thickness of the heat control layer to 30 nm or more, or by setting the objective lens to a numerical aperture of 0.7 or more. Improvement of C / N, improvement of jitter, and improvement of reproduction power margin for performing super-resolution reproduction, stable characteristics can be obtained by repeated erasure and reproduction, and the above-described effects can be obtained. Considering the emission upper limit power of the laser light source, the Curie temperature of the magneto-optical recording medium, and the reflectance, the thickness of the heat control layer is 100 nm.
The following is assumed.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A magneto-optical recording medium according to the present invention
This is a magneto-optical recording medium on which magnetic super-resolution reproduction is performed. That is, in the magneto-optical recording medium according to the present invention, the magnetic super-resolution reproducing method, that is, by irradiating the reproducing layer with laser light, the magnetization state signal of this reproducing layer is changed by the magneto-optical effect (Kerr effect or Faraday effect). It is converted into an optical signal and read out. In this reproduction method,
Using a temperature distribution generated in accordance with the laser light intensity distribution within the irradiation spot diameter and a temperature characteristic of the magneto-optical recording medium, a reproducing method capable of reproducing a signal having a period equal to or less than the diffraction limit of light, Further, the reproduction or recording / reproduction is particularly performed using a blue-violet laser (that is, about 350 nm to 450 nm).
Or / and the numerical aperture N.I. A. Is a magneto-optical recording medium applied to a new method in which an object lens of 0.7 or more is used.

The basic principle of the magnetic super-resolution reproduction to which the above-described magneto-optical recording medium of the present invention is applied is based on the CAD described above.
-MSR and others, for example,
No. 71634, etc. (Front Aperture Detection-Magnetic Super Reso
lution: hereinafter abbreviated as FAD-MSR) or, for example, a rear-detection-type magnetic super-resolution reproduction (Rear Aperture Detection-Magnetic Sup) described in, for example, JP-A-3-93058.
er Resolution: hereinafter abbreviated as RAD-MSR) or a magneto-optical recording / reproduction (Domain Wall Displacement D) described in, for example, JP-A-6-290496.
etection: hereinafter referred to as DWDD), and magnetic domain expansion detection magneto-optical recording / reproducing (MAMMOS) described in, for example, JP-A-8-7350. In these magnetic super-resolution reproducing methods, the magneto-optical recording medium has a reproducing layer and a recording layer, and has a process of transferring recording bits of the recording layer to the reproducing layer.

The magneto-optical recording medium according to the present invention is a magneto-optical recording medium having at least such a reproducing layer, a recording layer, and a thermal control layer. It is composed of one or more metal layers of aluminum Al, silver Ag, gold Au, copper Cu and an alloy containing at least one of these aluminum alloys having a thickness of 100 nm or less.

One embodiment according to the present invention is a CAD-MS
In R, the reproducing layer is irradiated with laser light in a magneto-optical recording medium in which reproduction is performed using a blue-violet laser,
The magnetization state signal of the reproducing layer is converted into an optical signal by a magneto-optical effect (Kerr effect or Faraday effect) and read. In magnetic super-resolution reproduction, a signal having a period equal to or less than the diffraction limit of light can be reproduced by showing perpendicular magnetization at a specific portion smaller than the reproduction laser spot diameter in accordance with the magnetization information direction of the recording layer. It is.

The reproducing method using the CAD-MSR is as described with reference to FIG. 9, but the CAD-MSR using the magneto-optical recording medium according to the present invention employs a laser beam L.
Is a blue-violet laser having a wavelength of 350 nm to 450 nm, and / or a numerical aperture N / L of the objective lens 11. A. However, a 0.7 or more objective lens is used as compared with the conventional one.

FIG. 1 is a schematic sectional view of an example of a magneto-optical recording medium according to the present invention. This magneto-optical recording medium is used, for example, in a reproducing method based on CAD-MSR, but it goes without saying that the present invention is not limited to this structure. In the example shown in FIG. 1, a first dielectric film 5, a reproducing layer 1, a reproducing auxiliary layer 2, an intermediate non-magnetic layer 4, a recording layer 3, a second
And a heat control layer 7 are formed, and a protective layer 8 is formed to cover the surface.

In the example shown in FIG. 1, the recording layer 3 is composed of first to third magnetic films 31 to 33. In this case, the first to third magnetic films 31 and Reference numeral 32 denotes a rare earth-transition metal magnetic film having a composition at room temperature having a dominant composition from a compensating composition to a transition metal, and can be selected to have a property of exhibiting high saturation magnetization in a desired temperature range as a whole.

In the present invention, the heat control layer 4 is formed of aluminum A having a thickness of 30 nm or more and 100 nm or less.
1, silver Ag, gold Au, copper Cu, and an alloy containing at least one of these metals.

When a CAD-MSR reproducing method is performed using the above-described magneto-optical recording medium according to the present invention, particularly when a blue-violet laser having a wavelength of 350 nm to 450 nm is used as a reproducing laser, Numerical aperture N. of objective lens 11 A. However, even when an objective lens having a size of 0.7 or more is used, the C / N ratio is improved,
The jitter and reproduction power margin were improved.

Next, embodiments of the magneto-optical recording medium according to the present invention will be described. However, this embodiment is not limited to these embodiments. [Example 1] In this example, the diameter was 120 mm,
A transparent substrate 10 made of polycarbonate having a thickness of 0.6 mm, formed with a track groove (guide groove) and having a track pitch of 0.35 μm was used, and as described with reference to FIG. A dielectric film 5, a reproducing layer 1, a reproducing auxiliary layer 2, an intermediate nonmagnetic layer 4, a recording layer 3, a second dielectric layer 6,
A heat control layer 7 was formed, and a protective layer 8 was formed covering the surface.

Each layer was formed by the following method. That is, Si, Tb, Gd, FeCo, Fe, and A are set in a magnetron sputtering apparatus having two vacuum chambers.
The above-mentioned transparent substrate 10 was mounted on a substrate holder, and the inside of the vacuum chamber was evacuated with a cryopump until a high vacuum of 1 × 10 ⁻⁵ [Pa] or less was obtained.

In a first vacuum chamber, Ar gas and N ₂ gas are evacuated to 50 [sccm] and 30 [sccm], respectively.
[sccm] and the pressure in the chamber is 0.2
After adjusting the main valve until the pressure becomes 4 [Pa], a silicon nitride film is formed to a thickness of 40 nm on the transparent substrate 10 by radio frequency (RF) reactive sputtering of a Si target, and the first dielectric film 5 is formed. Was formed.

Next, the valves for introducing the Ar gas and the N ₂ gas are closed, and the substrate holder is moved from the first vacuum chamber to the second vacuum chamber.
To a vacuum chamber. Thereafter, the inside of the second vacuum chamber was evacuated with a cryopump until a high vacuum of 1 × 10 ⁻⁵ [Pa] or less was obtained. Ar gas was introduced into the second vacuum chamber at 100 [sccm] while evacuation was performed, and the main valve was adjusted until the pressure in the chamber became 0.12 [Pa]. On the film 5, by direct current sputtering, the thickness is 30
reproduction layer 1 of GdFeCo with a thickness of 8 nm, Gd with a thickness of 8 nm
Auxiliary reproduction layer 2 made of Fe, intermediate nonmagnetic layer 4 made of Al with a thickness of 4 nm, first magnetic film 31 of recording layer 3 made of GdFeCo with a thickness of 10 nm, and second magnetic layer 30 made of TbFeCo with a thickness of 30 nm A film 32 and a second magnetic film 33 of the recording layer 3 made of TbFeCo having a thickness of 30 nm were formed.

Next, the Ar gas introduction valve was closed, and the substrate holder was moved from the second vacuum chamber to the first vacuum chamber. Then, in this first vacuum chamber,
Substrate holder in second vacuum chamber 1 × 10 ^-5 [Pa]
Evacuation was performed with a cryopump until the following high vacuum was reached.

Then, Ar gas and N ₂ gas are introduced into the first chamber at 50 [sccm] and 30 [sccm], respectively, while evacuating, and the pressure in the chamber is 0.24 [Pa]. After adjusting the main valve until
A silicon nitride film was formed to a thickness of 10 nm by RF reactive sputtering of a Si target to form a second dielectric film 6.

Next, the introduction valves of Ar gas and N ₂ gas were closed, and the inside of the first vacuum chamber was evacuated with a cryopump until a high vacuum of 1 × 10 ⁻⁵ [Pa] or less was reached.

Then, Ar gas is introduced at 100 [sccm] into the first vacuum chamber while evacuating, and the main valve is adjusted until the pressure in the chamber becomes 0.23 [Pa]. In this example, a 30-nm-thick Al thermal control layer 7 was formed on the second dielectric film 6 by DC sputtering.

The above-described magnetic layers and metal layers are formed by
By selecting the power to be applied to each target, its composition is selected.

Thereafter, the transparent substrate 1 on which these films are formed is formed.
0 is taken out of the vacuum chamber and the heat control layer 7 made of Al
Was formed by applying an ultraviolet curable resin and curing by irradiation with ultraviolet light to a thickness of 20 μm.

Thus, a magneto-optical recording medium was manufactured. In this case, the composition of GdFeCo of the reproducing layer 1 shows in-plane magnetization at room temperature, shows perpendicular magnetization at 150 ° C. or more,
The composition was adjusted so that the Curie temperature became 350 ° C. The composition of GdFe of the reproduction auxiliary layer 2 was adjusted so that the Curie temperature was 150 ° C. in the in-plane magnetic film having a transition metal dominant composition from room temperature to the Curie temperature.

The first magnetic film 31 constituting the recording layer 3 is
The composition of GdFeCo is a perpendicular magnetization film having a transition metal dominant composition from room temperature to the Curie temperature, and has a Curie temperature of 30.
The composition was adjusted to be 0 ° C. The second magnetic film 32 constituting the recording layer 3 is a perpendicular magnetization film having a composition of TbFeCo, which is a transition metal dominant composition from room temperature to the Curie temperature, and its composition is adjusted so that the Curie temperature becomes 280 ° C. The third magnetic film 33 constituting the recording layer 3 is made of TbFe
The composition of Co was adjusted so that the Curie temperature was 300 ° C. in a perpendicular magnetic film having a transition metal dominant composition from room temperature to the Curie temperature.

The magneto-optical recording medium of the first embodiment is referred to as an optical disk number 1.

[Embodiment 2] The same method and structure as in Embodiment 1 were adopted, but the thickness of the Al film of the heat control layer 4 was set to 4
It was set to 0 nm. This magneto-optical recording medium is used for optical disk number 2
And

[Embodiment 3] The same method and configuration as in Embodiment 1 were adopted, but the thickness of the Al film of the heat control layer 4 was set to 5
It was set to 0 nm. This magneto-optical recording medium is designated as optical disk number 3
And

[Comparative Example 1]
However, in this comparative example, the thickness of the Al film of the heat control layer 4 was set to 20 nm.
This magneto-optical recording medium is referred to as an optical disk number 4.

[Embodiments 4, 5, and 6] The same method and configuration as those in Embodiment 1 are used.
The thickness of the silicon nitride film of the second dielectric film 6 is set to 20 nm, and the thickness of the Al film of the heat control layer 4 is set to 30 n.
Films of m, 40 nm, and 50 nm were formed to produce a magneto-optical recording medium. These magneto-optical recording media are referred to as optical disk number 5,
6 and 7.

COMPARATIVE EXAMPLE 2 The same method and configuration as in Example 1 were used, but in this example, the thickness of the silicon nitride film of the second dielectric film 6 was set to 20 nm, The thickness of the Al film was 10 nm. This magneto-optical recording medium is referred to as an optical disk number 8.

[Embodiments 7, 8, 9] Although the same method and configuration as in Embodiment 1 are used, in these Embodiments 7, 8, and 9, the thickness of the silicon nitride film of the second dielectric film 6 is reduced. A magneto-optical recording medium having a thickness of 30 nm and a thickness of the Al film of each heat control layer 4 of 30 nm, 40 nm, and 50 nm was manufactured. These magneto-optical recording media are referred to as optical disk numbers 9, 10, and 11.

Comparative Example 3 The same method and configuration as in Example 1 were used, except that the thickness of the silicon nitride film of the second dielectric film 6 was formed to be 30 nm, and the thickness of the Al film of the heat control layer 4 was formed. The length was 20 nm. This magneto-optical recording medium is referred to as an optical disk number 12.

Table 1 lists the optical disk numbers, the thickness of the silicon nitride film of the second dielectric film 6 and the thickness of the Al film of the thermal control layer 4. Table 2 shows the measurement results of the jitter, the reproduction power margin, and the reproduction power at which the jitter is minimized. In this measurement, recording / reproducing characteristics were evaluated by a reproducing method using CAD-MSR by laser pulse irradiation magnetic field modulation recording. in this case,
Numerical aperture of the objective lens A. Is 0.6, and 406 nm
A blue-violet laser beam having the following wavelength was used. The duty of the laser light waveform for laser pulse irradiation magnetic field modulation recording was 35% of the system clock cycle time. The linear velocity of the optical disk was 3.7 m / s, and the external recording magnetic field was 350 [Oe]. The measurement was performed without applying an external magnetic field during reproduction. Under such conditions, 0.28 μm and 1.12
The ratio (C / N) between each carrier level and the noise level when recording was performed with a mark length of μm, and a bit length of 0.27 μm
The jitter when recording a random pattern modulated by m (1,7) RLL was measured for a reproduction power at which the jitter was 20% or less and a reproduction power at which the jitter was minimized.

[0052]

[Table 1]

[0053]

[Table 2]

FIGS. 2, 3 and 4 show that the thickness of the silicon nitride SiN film of the second dielectric film is 10 nm, 20 nm and 30 nm, respectively, based on the measurement results.
FIG. 4 is a diagram showing the relationship between the thickness of the Al heat control layer, the jitter, and the reproduction power when the above condition is satisfied. 5, 6, and 7
Similarly, based on the respective measurement results, the thickness of the silicon nitride SiN film of the second dielectric film is set to 10 n
FIG. 9 is a diagram showing the relationship between the thickness of the Al heat control layer at m, 20 nm, and 30 nm and the reproduction power margin at which jitter is minimized.

As is clear from Table 2 and FIGS. 2 to 7, excellent characteristics are exhibited when the thickness of the heat control layer 4 is 30 nm or more. This is because the temperature rise in the reproducing laser beam spot of the magneto-optical recording medium is suppressed, and as a result, the C / N and the jitter are greatly improved, and the margin for the reproducing power is also greatly improved.

In each of the above examples, the heat control layer 4 is made of Al. Next, the heat control layer 4 is made of Ag.
An example in the case of the above configuration will be described.

[Examples 10 and 11] These examples are as follows.
According to the same method and configuration as in Example 1, the heat control layer 4 is formed of a 30 nm thick and 40 nm thick A
A magneto-optical recording medium was manufactured by using the g film. The optical disk numbers of these magneto-optical recording media were 13 and 14.

[Comparative Example 4] In this example, too,
The same method and configuration as in the above, but the heat control layer 4
Was composed of an Ag film having a thickness of 20 nm to produce a magneto-optical recording medium. The optical disk number of this magneto-optical recording medium was set to 15.

The characteristics of Examples 10 and 11 and Comparative Example 4 were measured in the same manner as described above. Table 3 shows these measurement results.
Shown in

[0060]

[Table 3]

As described above, even when the heat control layer 4 was made of Ag, good results were obtained when the thickness was 30 nm or more.

[Embodiments 12 and 13] In these embodiments, the same method and configuration as those in Embodiment 1 are used, but the heat control layer 4 is formed to have a thickness of 30 nm and a thickness of 4 nm, respectively.
A magneto-optical recording medium composed of a 0 nm Au film was manufactured. The optical disk numbers of these magneto-optical recording media were 16 and 17.

[Comparative Example 4] In this example, too,
The same method and configuration as in the above, but the heat control layer 4
Was composed of a 20 nm-thick Au film to produce a magneto-optical recording medium. The optical disk number of this magneto-optical recording medium was 18.

With respect to these optical disks 16 to 18, the recording power margin where the jitter of each optical disk was 20% or less was measured under the same measurement conditions as described above. Table 4 shows the measurement results. Note that the recording power margin here is a margin portion where a recording power margin when the adjacent track is cross-written under the same condition and a recording power margin when the adjacent track is overwritten under the same condition are overlapped. .

[0065]

[Table 4]

Also in this case, when the thickness of the thermal control layer 4 is 30 nm or more, the recording power margin is greatly improved. This is because, by forming an Au film having a high thermal conductivity of 30 nm or more, an excessive rise in temperature during recording is suppressed, so that cross writing to an adjacent track is reduced, and as a result, a recording power margin is increased. It is considered something.

Also, as a result of measuring the jitter of the optical discs according to these embodiments, the reproduction power margin at which the jitter is 20% or less, and the reproduction power at which the jitter is minimized, the temperature rise in the reproduction laser beam spot is suppressed, and as a result, , The jitter was greatly improved, and the margin for the reproduction power was also greatly improved.

As is clear from the above-described embodiments, the heat control layer 4 is made of Au and its film thickness is set to 30 nm or more, whereby an excessive rise in temperature during recording and reproduction is suppressed. As a result, it is possible to improve the jitter and increase the reproduction power margin and the recording power margin.

Next, in the magneto-optical recording / reproducing apparatus for which the above-described magneto-optical characteristics were evaluated, the objective lens was set to have a numerical aperture N.P. A. Was changed to 0.7, and the C / N, jitter, and reproduction power margin were measured for the optical disc numbers 5 to 8 under the same measurement conditions as described above.
Table 5 shows the measurement results.

[0070]

[Table 5]

As is apparent from Table 5, the heat control layer 4
It can be understood that the jitter and the reproduction power margin can be improved by setting the thickness of the Al film to 30 nm or more. The reproduction power at which the jitter is minimized is increased by increasing the Al film thickness of the thermal control layer. This is because the increase in the temperature in the spot of the reproducing laser beam of the magneto-optical recording medium was suppressed by providing a thick Al film having a high thermal conductivity, and as a result, the best reproducing power of the magnetic super-resolution reproducing was increased. It is considered something.

As described above, in the present invention, the thermal control layer 42 is formed of a metal layer having a thickness of 30 nm or more and having a high thermal conductivity. From the reflectance, etc.
A thickness of 0 nm or less is a feasible thickness.

From this, in magnetic super-resolution reproduction,
As the objective lens, its numerical aperture N.P. A. Is 0.7 or more, according to the magneto-optical recording medium of the present invention, the C / N and the jitter can be greatly improved and the margin for the reproduction power can be greatly improved by effectively suppressing the temperature rise.

The heat control layer 4 is made of the above-described Al,
Similar effects can be obtained by using other metals having high thermal conductivity, such as Cu, in addition to Ag and Au. Alternatively, depending on the upper limit of the reproducing power or the upper limit of the recording power of the magneto-optical recording device used, the recording medium can be formed not only of these single metals but also of an alloy containing at least one of these metals.

In the above embodiment, the CAD-MSR
Is a case in which magnetic super-resolution reproduction is performed by using a magnetic super-resolution reproduction having a process of transferring a recording mark of a recording layer to a reproduction layer, such as FAD-MSR, RAD-MSR, and DWD.
D, MAMMOS and the like can be applied to a magneto-optical recording medium to achieve the same effect. In this case, each of the layers has at least a reproducing layer and a recording layer having a multilayer structure. Can be variously changed.

[0076]

As described above, according to the present invention, a blue-violet laser or a magnetic laser with a large numerical aperture of an objective lens is used to perform magnetic super-resolution reproduction, and a high laser beam is irradiated by a laser spot below the diffraction limit of light. Excessive temperature rise in the high-intensity irradiation section was effectively avoided by specifying the configuration of the thermal control layer, stabilizing the characteristics and improving the medium performance such as C / N, jitter, reproduction power margin, and recording. The power margin has been greatly improved, and a magneto-optical recording medium capable of recording and reproducing signals below the diffraction limit of light satisfactorily has been realized.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an example of a magneto-optical recording medium according to the present invention.

FIG. 2 is a diagram showing a measurement result of a relationship between a thickness of Al constituting a heat control layer of a magneto-optical recording medium according to the present invention and a comparative example, a jitter, and a reproduction power margin.

FIG. 3 is a diagram showing a measurement result of a relationship between a thickness of Al constituting a thermal control layer of a magneto-optical recording medium according to the present invention and a comparative example, jitter, and a reproduction power margin.

FIG. 4 is a diagram showing a measurement result of a relationship between a thickness of Al constituting a heat control layer of a magneto-optical recording medium according to the present invention and a comparative example, a jitter, and a reproduction power margin.

FIG. 5 is a diagram showing a measurement result of a relationship between a film thickness of Al constituting a heat control layer of a magneto-optical recording medium according to the present invention and a comparative example and a reproduction power at which jitter is minimized.

FIG. 6 is a diagram showing a measurement result of a relationship between a film thickness of Al constituting a heat control layer of a magneto-optical recording medium according to the present invention and a comparative example and a reproducing power at which jitter is minimized.

FIG. 7 is a diagram showing a measurement result of a relationship between a film thickness of Al constituting a heat control layer of a magneto-optical recording medium according to the present invention and a comparative example and a reproduction power at which jitter is minimized.

FIG. 8 is a schematic sectional view of a comparative example of a magneto-optical recording medium.

FIG. 9 is an explanatory diagram of an example of a magnetic super-resolution reproducing method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... reproduction layer, 2 ... reproduction assistance layer, 3 ... recording layer, 4 ... non-magnetic intermediate layer, 5 ... 1st dielectric layer,
6 ... second dielectric layer, 7 ... thermal control layer, 8 ...
Protective layer, 10: transparent substrate, 11: objective lens,
31: first magnetic film, 32: second magnetic film, 3
3 ... third magnetic film

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 7/125 G11B 7/125 A 7/135 7/135 A

Claims (4)

[Claims] 1. A magneto-optical recording medium having at least a reproducing layer, a recording layer, and a thermal control layer and performing magnetic super-resolution reproduction with a blue-violet laser beam, wherein the thermal control layer has a thickness of 30 nm to 100 nm. A magneto-optical recording medium comprising at least one metal layer of any of the following aluminum, silver, gold, copper and alloys containing one or more of the following. 2. The magneto-optical recording medium according to claim 1, wherein the magnetic super-resolution reproduction is a center detection type magnetic super-resolution magneto-optical reproduction. 3. A magneto-optical recording medium having at least a reproducing layer, a recording layer, and a thermal control layer, having a numerical aperture of an objective lens of 0.7 or more, and performing magnetic super-resolution reproduction. A magneto-optical recording medium, wherein the control layer is formed of at least one metal layer of 30 nm or more and 100 nm or less of aluminum, silver, gold, copper, and an alloy containing at least one of these. 4. The magneto-optical recording medium according to claim 3, wherein the magnetic super-resolution reproduction is a center detection type magnetic super-resolution magneto-optical reproduction.