JP2003067994A - Magneto-optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magneto-optical disk that can make the recording power margin 30% or larger. SOLUTION: This disk has a base plate laminated, in order, with a first dielectric layer, a reproducing layer, a reproduction support layer, a non- magnetic layer, a recording layer, a second dielectric layer, and a heat diffusion layer. The information on this disk can be read from the recorded marks smaller than the diameter of the light beam spot for reproduction by using MSR of a CAD system. It is desirable that the thickness x of the second dielectric layer and the thickness y of the heat diffusion layer are within the limits shown in Fig. or the thickness x of the second dielectric layer is 30 nm or larger, the thickness y of the heat diffusion layer is within the limits of 5 nm or less, or the thickness x of the second dielectric layer is 50 nm or larger, and the thickness y of the heat diffusion layer is within the limits of y<=0.3x+9.5. The temperature distribution at the time of reproduction can be improved, and a recording power margin can be made large.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical disk in which information is written and read by magneto-optical recording, and more particularly, to a magnetically induced resolution.
The present invention relates to a magneto-optical disk whose recording density is increased by the upper resolusion (MSR) technology.

[0002]

2. Description of the Related Art As a rewritable recording medium, a magneto-optical disk in which information is written and read by magneto-optical recording has been put into practical use. In this magneto-optical disk, a method of reading information from a recording mark smaller than a spot diameter of a light beam used for reproducing information has been proposed in recent years by a technique called MSR, which is a method for realizing a high recording density. Is being watched as.

This MSR takes advantage of the fact that a temperature distribution occurs in the spot of the light beam used for reproducing information, and by masking the low temperature region or high temperature region in this spot, the spot diameter of the light beam can be made smaller than the spot diameter. It is possible to read information from a small recording mark. As an example of such MSR, the center aperture detection (Center Apert
The ure detection (CAD) method is disclosed in Japanese Patent Laid-Open No. 5-81717.

In the CAD system, the in-plane magnetization state in which the in-plane magnetic anisotropy is predominant at room temperature and the reproducing layer in which the perpendicular magnetization anisotropy is predominant in the perpendicular magnetization state as the temperature rises and information is recorded. Using a magneto-optical disk provided with a recording layer for recording and a non-magnetic layer for preventing exchange coupling between the reproducing layer and the recording layer, information is recorded and reproduced as follows. First, information is recorded on the recording layer of this magneto-optical disk with a recording mark smaller than the spot diameter of the light beam used for reproduction.

Next, at the time of reproduction, the reproduction layer is irradiated with a light beam. The reproducing layer is heated by this light beam and its temperature rises. However, since the irradiating light beam is narrowed down to the diffraction limit by the condenser lens, the light intensity distribution becomes Gaussian distribution, and the temperature distribution in the reproducing layer also becomes Gaussian distribution. . Therefore, only the central portion of the portion of the reproducing layer irradiated with the light beam is heated to near the magnetic compensation temperature, and this portion is in the perpendicular magnetization state. A leak magnetic field from the recording layer is applied to the portion in the perpendicular magnetization state, and the recording mark recorded on the recording layer is transferred. Since the other portions of the reproducing layer remain in the in-plane magnetization state, the magnetization of the recording layer is masked. As a result, it becomes possible to read information from a recording mark smaller than the spot diameter of the light beam.

[0006]

Such a CAD method is an extremely excellent technique because it has the advantage that it is not necessary to apply an external magnetic field for initialization during reproduction. However, in the CAD method, since the recording mark is transferred to the reproducing layer by utilizing the leakage magnetic field from the recording layer, the error in the size of the magnetic domain recorded in the recording layer or the error in the laser power irradiated at the time of reading out. Due to this, the leakage magnetic field is greatly shaken, and there is a problem that stable reading is relatively difficult.

A general method for evaluating the read stability is to measure the error rate by changing the recording power and the reproducing power, and obtain the range of the recording power and the reproducing power at which the error rate is sufficiently reduced. . This readable recording power range is called a recording power margin, and if it is less than 20%, the reading stability is poor, and if it is 30% or more, it can be said to be sufficient. But CAD
In the method, the stability is low as described above, and the recording power margin often falls below 20%.

The present invention has been made in view of such problems, and an object thereof is to provide a magneto-optical disk capable of having a recording power margin of 30% or more.

[0009]

A first magneto-optical disk according to the present invention comprises a first dielectric layer, a reproducing layer, and
A second dielectric, which has a recording layer, a second dielectric layer, and a thermal diffusion layer, records information on the recording layer, and transfers the recorded information from the recording layer to the reproducing layer for reproduction. The thickness of the layer and the thickness of the thermal diffusion layer are within the range indicated by the diagonal lines in FIG. 1, or the thickness of the second dielectric layer is 30 nm or more, and the thickness of the thermal diffusion layer is within the range of 5 nm or less. Alternatively, the thickness of the second dielectric layer is 50 nm or more, the thickness of the second dielectric layer is x [nm], and the thickness of the thermal diffusion layer is y [nm].
Then, the thickness y of the heat diffusion layer is characterized in that y ≦ 0.3x + 9.5.

A second magneto-optical disk according to the present invention has a first dielectric layer, a reproducing layer, a recording layer, a second dielectric layer and a thermal diffusion layer which are sequentially stacked, and records information on the recording layer. At the same time, the recorded information is transferred from the recording layer to the reproducing layer and reproduced, and the thickness of the second dielectric layer is x [n
m] and the thickness y [nm] of the thermal diffusion layer, the thickness x of the second dielectric layer is 26.5 nm or more, and when the thickness x of the second dielectric layer is 35 nm or more, the thermal diffusion layer is Is within a range of y ≦ 0.3x + 9.5, and when the thickness x of the second dielectric layer is 30.5 nm or more and less than 35 nm, the thickness y of the thermal diffusion layer is y ≦ 0.78x−. It is within the range of 7.22, and the thickness x of the second dielectric layer is 26.5 nm or more and 30.
When the thickness is less than 5 nm, the thickness y of the thermal diffusion layer is -1.25.
It is characterized in that x + 43.1 ≦ y ≦ 1.63x−33.1.

According to the magneto-optical disk of the present invention, since the thickness of the second dielectric layer and the thickness of the thermal diffusion layer are within the above ranges, the temperature distribution during reproduction is improved and the recording power margin is improved. improves. In the present invention,
The shaded area in FIG. 1 includes the solid line surrounding the area.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 2 shows the structure of a magneto-optical disk according to an embodiment of the present invention. In this magneto-optical disk, information can be read from a recording mark smaller than the spot diameter of a reproduction light beam by a so-called CAD MSR, and a first dielectric layer is formed on a substrate 1. 2, reproduction layer 3, reproduction auxiliary layer 4, non-magnetic layer 5,
The recording layer 6, the second dielectric layer 7, and the thermal diffusion layer 8 are sequentially stacked.

The substrate 1 has, for example, a thickness in the stacking direction (hereinafter, simply referred to as thickness) of 0.1 mm to 1.2 mm, and is made of a material such as polycarbonate having a sufficient transmittance for light used for reproduction. It is configured. On this substrate 1, guide grooves called grooves for facilitating tracking control or embossed pits indicating address information or the like are formed as needed.

The first dielectric layer 2 has a thickness of, for example, 50 n.
m-90 nm, used for regeneration of silicon nitride, etc.
Transparent dielectric material with sufficient transmittance for
It is composed of In the present specification, silicon nitride is used.
Compounds have the composition Si ₃N_FourLimited to
However, it widely includes compounds of silicon and nitrogen.

The reproduction layer 3 transfers the information recorded in the recording layer 6 during reproduction. The reproduction layer 3 has, for example, a thickness of 15 nm to 40 nm and is made of gadolinium.
It is composed of an alloy of a rare earth element such as an iron-cobalt alloy (GdFeCo alloy) and a transition element. The content of the rare earth element in the reproduction layer 3 is higher than the compensation composition at room temperature. As a result, the reproducing layer 3 is in the in-plane magnetization state in which the in-plane magnetic anisotropy is dominant at room temperature, and becomes in the perpendicular magnetization state in which the perpendicular magnetic anisotropy is dominant when the temperature rises.
That is, at room temperature, the shape anisotropy is large due to the high saturation magnetization, and the magnetization direction is tilted in-plane, but the saturation magnetization becomes smaller as the temperature rises. The shape anisotropy becomes small in the vicinity, and the state becomes the perpendicular magnetization state in which the perpendicular magnetic anisotropy is dominant.

The auxiliary reproduction layer 4 is formed at a temperature at which the reproduction layer 3 changes from the in-plane magnetization state to the perpendicular magnetization state.
The purpose of this is to make the state change abrupt and to further increase the density of the magneto-optical disk. The reproduction assisting layer 4 is, for example,
It has a thickness of 5 nm to 20 nm and is composed of an alloy of a rare earth element such as a gadolinium-iron alloy (GdFe alloy) and a transition element.

The non-magnetic layer 5 is for blocking the magnetic coupling between the reproducing layer 3 and the auxiliary reproducing layer 4 and the recording layer 6 so as not to exchange-couple them. The nonmagnetic layer 5 has a thickness of 1 nm to 5 nm, for example, and is made of a transparent nonmagnetic material such as silicon nitride having a sufficient transmittance for light used for recording.

The recording layer 6 is for recording information.
The recording layer 6 has, for example, a thickness of 20 nm to 50 nm and is made of an alloy of a rare earth element such as a terbium-iron-cobalt alloy (TbFeCo alloy) and a transition element.

The second dielectric layer 7 is made of a dielectric material such as silicon nitride. Thermal diffusion layer 8
Is for increasing the difference in temperature change between the reproducing layer 3 and the recording layer 6 during cooling. For example, aluminum such as aluminum-titanium alloy (AlTi alloy) or aluminum-tungsten alloy (AlW alloy) is used. It is composed of an alloy containing.

The thickness of the second dielectric layer 7 and the thickness of the thermal diffusion layer 8 are usually 35 nm or less for the second dielectric layer 7 in order to improve the production efficiency, and the thickness of the thermal diffusion layer 8 is not formed. It is often set to 20 nm or more for ease of use.
However, these thicknesses are closely related to the recording power margin, and it is preferable to set them within the following ranges. By adjusting these thicknesses, it is possible to improve the temperature distribution in the magneto-optical disk when a light beam is irradiated during reproduction. This is because the recording power margin can be increased to 30% or more.

FIG. 3 shows the thickness of the second dielectric layer 7 and the thermal diffusion layer 8.
Shows the relationship with the thickness of the. Assuming that the thickness of the second dielectric layer 7 is x [nm] and the thickness of the thermal diffusion layer 8 is y [nm], the thickness x of the second dielectric layer 7 and the thickness y of the thermal diffusion layer 8 are lower left in FIG. Within the shaded area or the second
The thickness x of the dielectric layer 7 is 30 nm or more, the thickness y of the thermal diffusion layer 8 is 5 nm or less, or the thickness x of the second dielectric layer 7 is 50 nm or more, and the thickness y of the thermal diffusion layer 8 is y ≦ 0. .3x
It is preferably within the range of +9.5. It should be noted that the range shown by the lower left diagonal line in FIG. 3 also includes the solid line surrounding the range.

In a concrete approximation, the thickness x of the second dielectric layer 7 is 26.5 nm or more, and when the thickness x of the second dielectric layer 7 is 35 nm or more, the thermal diffusion layer is formed. 8 has a thickness y within the range of y ≦ 0.3x + 9.5. When the thickness x of the second dielectric layer 7 is 30.5 nm or more and less than 35 nm, the thickness y of the thermal diffusion layer 8 is y ≦ 0.78x. Within the range of -7.22, the thickness x of the second dielectric layer 7 is 26.5 nm or more 3
When it is less than 0.5 nm, the thickness y of the thermal diffusion layer 8 is −.
It is preferable that it is within the range of 1.25x + 43.1 ≦ y ≦ 1.63x−33.1.

It is more preferable to set the thickness x of the second dielectric layer 7 and the thickness y of the thermal diffusion layer 8 within the following ranges, because the recording power margin can be further increased. For example, in the range shown by the two-dot dashed line in the lower right of FIG. 3, or the thickness x of the second dielectric layer 7 is 40 nm.
As described above, the thickness y of the thermal diffusion layer 8 is in the range of 5 nm or less, or the thickness x of the second dielectric layer 7 is 50 nm or more, and the thermal diffusion layer 8 is
It is more preferable that the thickness y is within the range of y ≦ 0.33x + 3.33. In addition, in FIG. 3, the range shown by the lower right diagonal two-dotted line includes the two-dotted line surrounding the range.

In a concrete approximation, the thickness x of the second dielectric layer 7 is 32 nm or more, and the second dielectric layer 7 is
When the thickness x of the second diffusion layer 8 is 40 nm or more, the thickness y of the thermal diffusion layer 8 is within the range of y ≦ 0.33x + 3.33, and when the thickness x of the second dielectric layer 7 is 35 nm or more and less than 40 nm, The thickness y of the diffusion layer 8 is −0.625x + 30.0 ≦ y ≦.
Within the range of 0.33x + 3.33, when the thickness x of the second dielectric layer 7 is 32 nm or more and less than 35 nm, the thermal diffusion layer 8
Thickness y is -0.625x + 30.0≤y≤1.67x
More preferably, it is within the range of −43.33.

The thickness x of the second dielectric layer 7 is 200
It is preferably not more than 100 nm, more preferably not more than 100 nm. This is because if it is too thick, the film will crack.

The magneto-optical disk having such a structure can be manufactured, for example, as follows.

First, the substrate 1 is manufactured by, for example, injection molding. At that time, if necessary, use a stamper,
Guide grooves or embossed pits are formed on the surface of the substrate 1. Then, the first dielectric layer 2, the reproduction layer 3, the reproduction auxiliary layer 4, the non-magnetic layer 5, the recording layer 6, the second dielectric layer 7, and the thermal diffusion layer 8 are sequentially formed on the substrate 1 by, for example, sputtering. Stack. Of these, the first dielectric layer 2, which is formed of a dielectric material such as silicon nitride or a non-magnetic material,
For example, high frequency sputtering is used for the non-magnetic layer 5 and the second dielectric layer 7, and direct current sputtering is used for the reproducing layer 3, the reproduction assisting layer 4, the recording layer 6 and the thermal diffusion layer 8 formed of an alloy. At that time, the thickness x of the second dielectric layer 7 and the thickness y of the thermal diffusion layer 8 are adjusted to fall within the above-mentioned ranges. As a result, the magneto-optical disk shown in FIG. 2 is formed.

On this magneto-optical disk, information is written and read as follows.

Information is written by irradiating the recording layer 6 with a light beam having a smaller spot diameter than the light beam used for reproduction from the substrate 1 side. The recording layer 6 records information with a recording mark smaller than the spot diameter of the reproduction light beam.

The information is read by irradiating the reproducing layer 3 with a reproducing light beam from the substrate 1 side. In the reproducing layer 3, only the central portion of the portion irradiated with the light beam is heated to near the magnetic compensation temperature, and only the central portion is in the perpendicular magnetization state. As a result, a leakage magnetic field from the recording layer 6 is applied to this central portion, and the recording mark recorded on the recording layer 6 is transferred. The other portion of the reproducing layer 3 is in the in-plane magnetization state and masks the magnetization of the recording layer 6.

In this embodiment, the thickness x of the second dielectric layer 7 and the thickness y of the thermal diffusion layer 8 are within the above-mentioned predetermined ranges, so that the temperature distribution in the magneto-optical disk is improved. . Therefore, even if the leakage magnetic field from the recording layer 6 changes due to an error in the size of the magnetic domain recorded in the recording layer 6 or an error in the power of the light beam irradiated at the time of reading, the recording power margin is large and the information is It can be read stably.

As described above, according to the magneto-optical disk of this embodiment, the thickness x of the second dielectric layer 7 and the thickness y of the thermal diffusion layer 8 are set within the above-mentioned predetermined ranges. The recording power margin can be set to 30% or more, and the information reading stability can be improved.
Further, even if the manufacturing conditions vary, it is possible to secure 20%, which is the absolute required amount of the recording power margin, with a margin, so that the manufacturing operation rate and the yield can be improved, and the manufacturing cost can be reduced. .

In particular, the thickness x of the second dielectric layer 7 is 200n.
When it is set to m or less, cracking of the film can be prevented and high characteristics can be obtained.

[0035]

EXAMPLES Further, specific examples of the present invention will be described in detail.

The thickness x of the second dielectric layer 7 and the thermal diffusion layer 8
A plurality of magneto-optical disks shown in FIG. 1 were manufactured by changing the thickness y of the magneto-optical disk. Here, with reference to FIG. 1, description will be given using the same reference numerals as those in FIG.

First, polycarbonate was injection molded to prepare a disk-shaped substrate 1 having a thickness of 1.2 mm. At that time, a spiral groove was formed on the surface of the substrate 1 by the stamper. Then, a silicon nitride film having a thickness of 90 nm was formed on the surface of the substrate 1 by high frequency sputtering to form a first dielectric layer 2. Subsequently, an amorphous film of Gd ₃₁ Fe ₅₄ Co _{15 having} a thickness of 20 nm is formed on the first dielectric layer 2 by DC sputtering to form a reproducing layer 3, and further an amorphous film of Gd ₁₁ Fe _{89 having} a thickness of 10 nm is formed. To form a reproduction assisting layer 4. After that, the thickness of 2.
A non-magnetic layer 5 was formed by forming a 5 nm silicon nitride film. Next, an amorphous film of Tb ₁₉ Fe ₆₆ Co _{15 having} a thickness of 40 nm was formed on the non-magnetic layer 5 by direct current sputtering to form a recording layer 6. Then, on the recording layer 6,
The second dielectric layer 7 was formed by forming a silicon nitride film having a thickness of 15 nm to 50 nm by high frequency sputtering. Finally, an AlTi alloy film (titanium content: 1.5% by mass) having a thickness of 5 nm to 40 nm was formed on the second dielectric layer 7 by direct current sputtering to form a thermal diffusion layer 8.

As a result, the thickness x of the second dielectric layer 7 is set to 1
Within the range of 5 nm to 50 nm, the thickness y of the thermal diffusion layer 8 is set to 5
A plurality of magneto-optical discs each having a variation in the range of 40 nm to 40 nm were obtained. This magneto-optical disk has a track pitch of 0.65 μm, and corresponds to a land / groove substrate in which information is written in both the groove-formed portion and the land portion between adjacent grooves.

The recording / reproducing characteristics of each of the obtained magneto-optical disks were evaluated. First, the magneto-optical disk was rotated to a linear velocity of 9.5 m / s, and -24 kA / m.
With the recording magnetic field applied, the recording power was changed and a (2-7) RLL-modulated random pattern having a shortest pit length of 0.4 μm was recorded on the land portion. Then, the magneto-optical disk was rotated at the same linear velocity, and while the reproducing magnetic field of +8 kA / m was applied, the recorded signal was reproduced while changing the reproducing power, and the byte error rate was measured. FIG. 4 shows representatively the measurement results of error bytes obtained for one magneto-optical disk.

In FIG. 4, the horizontal axis represents the recording power and the vertical axis represents the reproducing power. The byte error rate is expressed by a contour formula that connects equal values with a line. The area shown by the lower right diagonal thin line is less than 1 × 10 ⁻⁴ , and the area shown by the lower left diagonal thin line is 1 × 10 ^{−. 4} or more and less than 1 × 10 ^-3 , the area indicated by the lower right diagonal thick line is 1 × 10 ^-3 or more and less than 1 × 10 ^-2 , and the area indicated by the lower left diagonal thick line is 1 × 10 ^-2 or more 1 × 10 ^-1 The region indicated by the lower right diagonal broken line is 1 × 10 ⁻¹ or more.

Next, a recording power margin was obtained for each magneto-optical disk based on the measurement result of the bite error rate. Regarding the recording power margin, the reproduction power that maximizes the recording power in the area where the byte error rate is less than 1 × 10 ⁻⁴ is set as the optimum reproduction power, and the lower limit recording when the byte error rate is less than 1 × 10 ⁻⁴ at the optimum reproduction power It was calculated from Equation 1 from the power L [mW] and the upper limit recording power H [mW].

[0042]

[Equation 1]

A specific description will be given with reference to FIG.
In this case, since the lower limit recording power L is 7.5 mW and the upper limit recording power H is 10.0 mW, the recording power margin is 28.6% according to the equation (1).

FIG. 5 shows the result of the recording power margin obtained for each magneto-optical disk. In FIG. 5, the horizontal axis represents the thickness x of the second dielectric layer 7, and the vertical axis represents the thickness y of the thermal diffusion layer 8. The recording power margin is expressed by a contour equation connecting equal values with a line. The area shown by the lower left diagonal one-dot thin line is 34% or more and less than 36%, and the area shown by the lower right diagonal two-dot thin line is 32% or more and less than 34%, the area indicated by the lower left diagonal thin line is 30% or more and less than 32%, the area indicated by the lower right diagonal thin line is 28% or more and less than 30%, and the area indicated by the thicker left lower diagonal line is 26 % Or more and less than 28%, lower right diagonal 2
The area shown by the dotted line is 24% or more and less than 36%, the area shown by the lower left diagonal thick line is 22% or more and less than 24%, and the area shown by the lower right diagonal broken line is 20% or more and less than 32%.

From these results, the thickness x of the second dielectric layer 7 and the thickness y of the thermal diffusion layer 8 have a close relationship with the recording power margin. These thicknesses x and y are the lower left diagonal thin line and the lower right diagonal. It was found that the recording power margin can be set to 30% or more within the range shown by the two-point broken line and the one-point broken line on the lower left.

When this range is approximated by a mathematical expression, the thickness x of the second dielectric layer 7 is 26.5 nm or more, and when the thickness x of the second dielectric layer 7 is 35 nm or more, thermal diffusion is performed. Layer 8
Is within a range of y ≦ 0.3x + 9.5, and when the thickness x of the second dielectric layer 7 is 30.5 nm or more and less than 35 nm, the thickness y of the thermal diffusion layer 8 is y ≦ 0.78x−. Within the range of 7.22, the thickness x of the second dielectric layer 7 is 26.5 nm or more 3
When it is less than 0.5 nm, the thickness y of the thermal diffusion layer 8 is −.
It is within the range of 1.25x + 43.1 ≦ y ≦ 1.63x−33.1.

Further, the thickness x of the second dielectric layer 7 and the thickness y of the thermal diffusion layer 8 are within the range indicated by the broken line at the lower right diagonal two points, and further within the range indicated by the broken line at the lower left diagonal one point. It was found that the recording power margin can be further increased by doing so.

If these are also approximated by mathematical expressions,
More preferably, the thickness x of the second dielectric layer 7 is 32 nm.
When the thickness x of the second dielectric layer 7 is 40 nm or more, the thickness y of the thermal diffusion layer 8 is y ≦ 0.33x + 3.
In the range of 33, when the thickness x of the second dielectric layer 7 is 35 nm or more and less than 40 nm, the thickness y of the thermal diffusion layer 8 is −0.
Within the range of 625x + 30.0 ≦ y ≦ 0.33x + 3.33, when the thickness x of the second dielectric layer 7 is 32 nm or more and less than 35 nm, the thickness y of the thermal diffusion layer 8 is −0.625x +.
It is within the range of 30.0 ≦ y ≦ 1.67x−43.33.

In the above embodiment, the case where the thickness x of the second dielectric layer 7 is changed within the range of 15 to 50 nm and the thickness y of the thermal diffusion layer 8 is changed within the range of 5 to 40 nm is specifically described. As described above, FIG. 5 also shows the case where the thickness x of the second dielectric layer 7 is thicker than 50 nm or the thickness y of the thermal diffusion layer 8 is thinner than 5 nm or thicker than 40 nm. According to the results shown, similar results can be obtained in the extended range of the region shown in FIG.

Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the above-described embodiments and examples, and various modifications can be made. For example, although the configuration of the magneto-optical disk has been specifically described in the above embodiments and examples, the present invention is not limited to the first embodiment.
It can be widely applied to a magneto-optical disk having a dielectric layer, a reproducing layer, a recording layer, a second dielectric layer and a thermal diffusion layer, and may not have the other layers described in the above embodiment. , Or may have other layers other than those described.

Further, in the above-mentioned embodiment and example,
Although the magneto-optical disk for reading out information by the CAD MSR has been described, the present invention improves the internal temperature distribution in the magneto-optical disk during reproduction.
Other methods of reading using temperature distribution, for example, MSR of rear aperture detection (RAD) method, or domain wall displacement detection (Domain Wall Displacement)
ment detection (DWDD) method, the present invention can be applied to a magneto-optical disk that reads information. However, the present invention is preferable because a high effect can be obtained in the CAD method.

[0052]

As described above, according to the magneto-optical disk of any one of claims 1 or 2 to 5, the thickness of the second dielectric layer and the thickness of the heat diffusion layer can be reduced. Since it is set within the predetermined range, the recording power margin can be set to 30% or more, and the information reading stability can be improved. Even if the manufacturing conditions vary, the recording power margin is the absolute required amount.
Since 0% can be secured with a margin, the manufacturing operation rate and the yield can be improved, and the manufacturing cost can be reduced.

Particularly, according to the magneto-optical disk of the fourth aspect, since the thickness of the second dielectric layer is set to 200 nm or less, it is possible to prevent the film from cracking and obtain high characteristics. You can

[Brief description of drawings]

FIG. 1 is a relationship diagram showing a range of thicknesses of a second dielectric layer and a heat diffusion layer in a magneto-optical disk of the present invention.

FIG. 2 is a partial cross-sectional view showing the structure of a magneto-optical disk according to an embodiment of the present invention.

3 is a relationship diagram showing a preferable range of the thickness of the second dielectric layer and the thickness of the heat diffusion layer in the magneto-optical disk shown in FIG.

FIG. 4 is a characteristic diagram showing a relationship among a reproduction power, a recording power and a byte error rate according to the example of the present invention.

FIG. 5 is a characteristic diagram showing the relationship between the thickness of the second dielectric layer, the thickness of the thermal diffusion layer, and the recording power margin according to the example of the present invention.

[Explanation of Codes] 1 ... Substrate, 2 ... First Dielectric Layer, 3 ... Reproduction Layer, 4 ... Reproduction Auxiliary Layer, 5 ... Nonmagnetic Layer, 6 ... Recording Layer, 7 ... Second Dielectric Layer,
8 ... Thermal diffusion layer

Claims (5)

[Claims] 1. A first dielectric layer, a reproducing layer, which are sequentially stacked.
A magneto-optical disk having a recording layer, a second dielectric layer and a thermal diffusion layer, for recording information on the recording layer and transferring the recorded information from the recording layer to the reproducing layer for reproduction. The thickness of the second dielectric layer and the thickness of the thermal diffusion layer are within the range indicated by the diagonal lines in FIG. 1, or the thickness of the second dielectric layer is 30 nm or more,
The thickness of the thermal diffusion layer is in the range of 5 nm or less, or the thickness of the second dielectric layer is 50 nm or more,
When the thickness of the second dielectric layer is x [nm] and the thickness of the thermal diffusion layer is y [nm], the thickness y of the thermal diffusion layer is y ≦.
A magneto-optical disk having a range of 0.3x + 9.5. 2. A first dielectric layer, a reproducing layer, which are sequentially stacked.
A magneto-optical disk having a recording layer, a second dielectric layer and a thermal diffusion layer, for recording information on the recording layer and transferring the recorded information from the recording layer to the reproducing layer for reproduction. When the thickness of the second dielectric layer is x [nm] and the thickness of the thermal diffusion layer is y [nm], the thickness x of the second dielectric layer is 26.5 nm or more. When the layer thickness x is 35 nm or more,
The thickness y of the thermal diffusion layer is in the range of y ≦ 0.3x + 9.5, and the thickness x of the second dielectric layer is 30.5 nm or more and 35 nm.
When less than, the thickness y of the thermal diffusion layer is y ≦ 0.78
x-7.22, and the thickness x of the second dielectric layer is 26.5 nm or more and 30.5.
When the thickness is less than nm, the thickness y of the thermal diffusion layer is -1.2.
A magneto-optical disk having a range of 5x + 43.1 ≦ y ≦ 1.63x−33.1. 3. The thickness x of the second dielectric layer is 32 nm or more, and when the thickness x of the second dielectric layer is 40 nm or more,
The thickness y of the thermal diffusion layer is in the range of y ≦ 0.33x + 3.33, and when the thickness x of the second dielectric layer is 35 nm or more and less than 40 nm, the thickness y of the thermal diffusion layer is −0. .625x +
Within the range of 30.0 ≦ y ≦ 0.33x + 3.33, and when the thickness x of the second dielectric layer is 32 nm or more and less than 35 nm, the thickness y of the thermal diffusion layer is −0.625x +.
3. The magneto-optical disk according to claim 2, wherein the range is 30.0 ≦ y ≦ 1.67x−43.33. 4. The thickness x of the second dielectric layer is 200 nm.
The magneto-optical disk according to claim 2, wherein: 5. The magneto-optical disk according to claim 2, wherein the second dielectric layer is made of a nitride of silicon (Si), and the thermal diffusion layer is made of an alloy containing aluminum (Al).