JPH09204702A - Magneto-optical recording medium and its recording or reproducing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the magneto-optical recording medium in which a high density recording/reproducing is conducted, the recording is accomplished using a small applied magnetic field, a magnetic modulation system is optimally used and the CNR during a reproducing is satisfactory. SOLUTION: The composition ratio of Co in a reproducing layer is made to 12 to 50at%. After forming a substrate, an etching process is performed for the surface layer and a reproducing layer is formed, or, the magneto-optical recording medium is manufactured by lowering the sputtering gas pressure of the reproducing layer to the level of 3mTorr or providing a heat radiation layer made of a metal or a metallic alloy on the recording layer. During a recording, the laser beam is made pulsive, the phase difference between the pulsed magnetic field and the pulsed laser beam is set to zero to 60nsec and the recording of information is performed. Furthermore, during a reproducing, the power of the laser beam is set to 2.0 to 3.0mW, With the use of these methods, the temperature coefficient of the Kerr rotational angle is set larger than 8.0 and translucent polycarbonate resin is used for the substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises an exchange coupling magnetic layer composed of a recording layer which is a perpendicular magnetization film and a reproducing layer which is an in-plane magnetization film at room temperature, and the magnetization direction of the recording layer is transferred to the magnetic layer. The present invention relates to a magneto-optical recording medium that achieves high-density recording by reading and writing the same and a recording or reproducing method thereof.

[0002]

2. Description of the Related Art Magneto-optical recording media have attracted attention as rewritable, large-capacity, and highly reliable recording media, and have begun to be put to practical use as computer memories and the like. However, with the increase in the amount of information and the downsizing of the apparatus, a higher density recording / reproducing technique is required.

[0003] The high-density recording / reproducing technology includes a device-side technology and a medium-side technology. The former techniques include an optical super-resolution method for obtaining a focused spot that exceeds the diffraction limit of laser light, and shortening of the wavelength of laser light. As the latter technique, there are techniques such as narrowing the pitch of the medium and improving the reproduction resolution by the magnetic multilayer film. Here, the technology for improving the reproduction resolution by the magnetic multilayer film utilizes the fact that the temperature distribution of the laser spot has the highest Gaussian distribution near the center to selectively transfer the state of the recording layer to the reproduction layer. do it,
This is a technique for reading the state of the reproduction layer.

Further, in the conventional magneto-optical recording medium used in the optical super-resolution method, a recording layer made of a perpendicular magnetization film is usually used. A glass substrate is usually used as the substrate for the magneto-optical recording medium.

[0005]

In order to raise the temperature of the reproducing layer to the Curie temperature or higher, it is necessary to increase the laser power, and if the temperature rise is insufficient, the CNR of the recording signal deteriorates. Further, a large applied magnetic field is required to align the magnetization direction of the reproducing layer with insufficient temperature rise with the direction of the external magnetic field, and even in that case, the deterioration of the CNR of the recording signal cannot be avoided.
Further, in the magnetic field modulation recording, there is also a situation that it is desired that the applied magnetic field is small.

When the Curie temperature of the recording layer is low and the temperature difference from the Curie temperature of the reproducing layer is large, the Curie temperature of the recording layer becomes lower than the Curie temperature of the recording layer during recording, and the magnetization direction of the reproducing layer becomes When the transfer is started, a part of the magnetization of the reproducing layer has already started to face the in-plane direction, which becomes noise of the signal transferred from the reproducing layer to the recording layer, and the CNR of the recording signal decreases. is there.

Further, in the technique of transferring the state of the recording layer to the reproducing layer and reading the same, it is required that the temperature distribution of the reproducing layer heated by the laser spot has a desired distribution.
This is because when the temperature distribution deviates from the desired distribution, noise due to the disordered magnetization direction and even the non-central portion of the laser spot (the peripheral low-temperature portion) are read out. This is because the crosstalk noise that occurs increases.

Further, in a transmission type magneto-optical recording medium in which light is transmitted through the magnetic layer, heat accumulation due to irradiation of a laser spot can be ignored. However, in a magneto-optical recording medium of the type that detects reflected laser light from the magnetic layer, the film thickness is, for example, 40
Since it is 0 Å or more and the accumulated heat affects the temperature distribution of the reproducing layer, the above noise increases.

Further, in the conventional recording on the magneto-optical recording medium, since the recording was carried out under the condition that the laser light of a constant intensity was irradiated, the temperature rising region in the recording layer was larger than the laser spot. As a result, there is a problem that the recording spot becomes large and it is difficult to increase the density. In the technique of transferring the state of the recording layer to the reading layer and reading it, it is required that the temperature distribution of the reading layer heated by the laser spot has a desired distribution. This is because when the temperature distribution deviates from the desired distribution, noise due to the disordered magnetization direction and even the state of the non-central portion of the laser spot (the peripheral low temperature portion) are read. This is because the crosstalk noise that occurs increases.

Further, in a transmission type magneto-optical recording medium in which light is transmitted through the magnetic layer, heat accumulation due to irradiation of a laser spot can be ignored. However, in a magneto-optical recording medium of the type that detects reflected laser light from the magnetic layer, the film thickness is, for example, 40
Since it is 0 Å or more and the accumulated heat affects the temperature distribution of the reproducing layer, the above noise increases.

Further, when glass is used as the substrate, there are the following problems. 1) The weight of the magneto-optical recording medium becomes heavy. 2) It may be damaged if dropped by mistake. 3) It cannot withstand high speed rotation. 4) It becomes expensive because it is necessary to polish the surface.

5) It is difficult to directly form the guide groove used for tracking the laser beam. Further, in the conventional CAD method, the conversion from the in-plane magnetized film to the perpendicular magnetized film in the reproducing layer is performed in a wide range from several tens to 100 degrees, and due to the magnetic influence from the recording layer to the reproducing layer. Since the in-plane magnetization is not completely retained in the reproducing layer and the masking effect is lowered, the transfer region is not clear, the reproducing noise is large, and the large MSR effect cannot be obtained.
In addition, since there is no clear threshold value for transfer, the transfer temperature is likely to depend on the preparation conditions of the material, and uniform characteristics could not be obtained.

It is an object of the present invention to reduce the above noise in a magneto-optical recording medium of the type that detects reflected laser light from a magnetic layer, by making heat accumulation negligible. . It is another object of the present invention to provide a magneto-optical recording medium that can record even when the applied magnetic field is small and can be optimally used in a magnetic field modulation system. Another object of the present invention is to provide a magneto-optical recording medium capable of recording with good CNR.

The present invention also provides a magneto-optical recording medium which realizes high-density recording / reproducing in a magneto-optical recording medium by reducing the soaking area during recording / reproducing and is easy to handle. To aim. Also,
The present invention solves the above-mentioned problems. By providing a magnetic transfer function to the recording layer itself, not to the reproducing layer, the transfer temperature is made clear, the reproduction noise is low, the MSR effect is large, and the uniformity is excellent. It is intended to obtain a magneto-optical recording medium.

[0015]

According to the present invention, there is provided a translucent substrate, an underlayer formed on the translucent substrate, and a reproducing layer which is an in-plane magnetized film at room temperature formed on the underlayer. , A recording layer formed on the reproducing layer and transferring the magnetization direction to the reproducing layer when heated to a predetermined temperature, a magneto-optical recording medium having a Kerr rotation angle temperature coefficient of 8.0. The above is characterized.

Further, the present invention is characterized in that the recording layer is a perpendicular magnetization film at room temperature. Further, the present invention is characterized in that the reproducing layer is composed of a transition metal containing cobalt (Co) and a rare earth, and the composition ratio of Co in the reproducing layer is in the range of 12 at% to 50 at%. In the present invention, the reproducing layer is G
It is characterized by containing d and Fe.

Further, the present invention is characterized in that the underlayer is formed by depositing SiN which functions as an interference layer in a range of 600Å to 800Å. Further, the present invention is characterized in that the thickness of the reproducing layer is in the range of 800Å to 1200Å.
In the present invention, the recording layer has a Co content of 1
It is characterized by forming a film of TbFeCo in the range of 0 at% to 16 at%.

Further, according to the present invention, the reproducing layer has a Gd in the reproducing layer.
Content of GdF in the range of 30 at% to 36 at%
It is characterized in that it is formed by forming a film of eCo. Further, in the present invention, the surface of the interference layer is 0.02 W / cm ^{2 to} 0.08 W /
The present invention is characterized in that a reproducing layer and a recording layer are formed after an etching treatment with an etching power in a range of cm ² .

Further, according to the present invention, the reproducing layer has a thickness of 2 to 7 mTorr.
It is characterized in that the film is formed at a sputtering gas pressure in the range of r. Further, the present invention is characterized in that the translucent substrate is a polycarbonate resin. In the present invention, the recording layer is TdFeCo, and the reproducing layer is GdFeCoCr, GdFeCoNi, GdFeCoTi, or GdFeC.
oAl or GdFeCoMn or GdFeCoNiCr
Alternatively, it is characterized by being GdFeCoAlTi.

Further, the present invention is characterized in that a heat dissipation layer is formed on the recording layer. In the present invention, the heat dissipation layer is made of Al.
Or Au or Pt or Ti or V or Cr or Mn or Fe or Co or Ni or Cu or Zn or Mo or A
g or Sn or Sb or W. Further, the present invention is characterized in that the film thickness of the heat dissipation layer is 200 to 1000Å.

Further, according to the present invention, the surface of the underlayer is set to 0.0.
After etching with 2W / cm ² ~0.08W / cm ² in the range etching power, characterized in that formed by forming the recording layer and the reproducing layer. In the present invention, the heat dissipation layer is R
It is characterized by being formed by an F magnetron sputtering method with an RF power of 100 to 1000 W and an argon pressure of 1 to 10 mTorr.

According to the present invention, the translucent polycarbonate substrate has a birefringence of 20 to 25 nm, a birefringence variation of 6 to 10 nm in the circumferential direction, and a radius of curvature of 35 to 35 at the corner of the groove and the land. It is characterized by being 50 nm. Further, the present invention is characterized in that the surface roughness of the translucent polycarbonate substrate is 100 to 500 Å.

Further, the present invention is characterized in that the recording layer is a magnetic layer whose primary transition point from antiferromagnetism to ferromagnetism is set to 50 ° C. or higher. Further, in the present invention, the recording layer has (Mn
_(100-x) M _x ) ₂ Sb (M = Cr, V, Co, Cu, Z
n, Ge, As). The present invention also provides (Mn _(100-x) Cr _x ) ₂ Sb, x = 10 to 30 at%
It is characterized by being.

The present invention is also characterized in that the externally applied magnetic field during recording is 50 to 200 Oe. Further, according to the present invention, the duty of the laser pulse during recording is set to 20 to 60.
%, The phase difference between the pulse magnetic field and the laser pulse is 0 to 60n.
It is characterized in that it is set to sec.

Further, according to the present invention, in reproducing the magneto-optical recording medium, the reproducing power is 1.5 to 2.2 mW and the reproducing power is 1.5 to 1.7 m at the reproducing linear velocity of 1.1 to 1.3 m / sec. / S
The reproduction power is 1.8 to 2.7 m at the reproduction linear velocity of ec.
The reproducing power is 2.0 to 3.0 mW and the reproducing power is 2.9 to 3.1 m / se at the reproducing linear velocity of 1.9 to 2.1 m / sec.
The reproducing power is 2.4 to 3.7 mW at the reproducing linear velocity of c.
At a reproducing linear velocity of 4.9 to 5.1 m / sec, a reproducing power of 3.2 to 4.5 mW, and a reproducing power of 8.9 to 9.1 m / sec.
The reproducing power is 4.0-6.0mW at the reproducing linear velocity of
It is characterized in that they are set respectively.

Further, according to the present invention, after forming the underlayer, the surface of the underlayer is subjected to sputter etching treatment, and then Co
Is characterized in that a reproducing layer containing 12 at% to 50 at% is formed. Further, the present invention after formation of the base layer is subjected to sputter etching treatment in etching power in a range of 0.02W / cm ² ~0.08W / cm ² on the base layer surface, then, 12at% ~ the Co It is characterized in that a reproducing layer containing 50 at% is formed.

The present invention is also characterized in that the recording layer is formed of TbFeCo having a Co content in the range of 10 at% to 16 at%. Further, the present invention is characterized in that the reproducing layer is formed of GdFeCo having a Gd content ratio of 30 at% to 36 at%. Further, the present invention is characterized in that the reproduction layer is formed at a sputtering gas pressure in the range of 2 to 7 mTorr.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a magneto-optical recording medium comprising a recording layer and a reproducing layer which is an in-plane magnetized film at room temperature to which magnetization is transferred from the recording layer. The sectional structure is as shown in FIG. That is, on the transparent substrate 1, the interference layer 2, the reproducing layer 3, the recording layer 4, the protective layer 5,
This is a structure in which the heat dissipation layer 6 and the ultraviolet curable resin 7 are sequentially laminated.

The present invention discloses a technique relating to the recording or reproducing method of the transparent substrate 1, the interference layer 2, the reproducing layer 3, the recording layer 4, the heat dissipation layer 6 and the magneto-optical recording medium in the above structure. . Example 1 FIG. 1 is a schematic diagram showing a cross-sectional structure of a magneto-optical recording medium of Example 1. In the illustrated magneto-optical recording medium, a thickness of 80 is formed on a polycarbonate (PC) substrate in order from the substrate side.
Interference layer consisting of 0Å SiN, GdFe with a thickness of 500Å
A reproducing layer made of Co, a recording layer made of TbFeCo having a thickness of 500 Å, an oxidation preventing layer made of SiN having a thickness of 800 Å are formed, and an ultraviolet curable resin layer (not shown) has a thickness of about 20 μm as a protective layer It is formed by coating.
The illustrated layers can be formed by a conventionally known sputtering method or the like.

The composition of the reproducing layer is "Gd: Fe: Co = 3.
1:47:22 at% ”, and the composition of the recording layer is“ T
b: Fe: Co = 26: 66: 8 at% ”. The results of measuring the residual Kerr rotation angle of the recording layer and the reproducing layer having this composition are shown in FIG. As shown, the temperature at which the reproducing layer becomes a perpendicularly magnetized film is 140 ° C.
The Curie temperature is 300 ° C. The Curie temperature of the recording layer is 230 ° C. and the compensation temperature is room temperature. The reproduction is performed by raising the temperature of the transfer to 140 ° C. and transferring the magnetization direction of the recording layer to the reproducing layer to read it.

At the time of recording, as shown in FIG. 3, the CNR is saturated when the laser power is 3.5 [mW] or more, and at this time, the reproducing layer is heated to the Curie temperature or higher. Therefore, as shown in FIG. 4, the externally applied magnetic field can be recorded even from a low magnetic field of 50 [Oe], and the CNR is saturated at 200 [Oe] or more. Conventionally, it was necessary to apply an external magnetic field of 500 [Oe] or more (Optical D
ata storage 1994, Technica
l Digest Series Volume 1
0, p128-129), it can be seen that the present magneto-optical recording medium can be recorded with an extremely small externally applied magnetic field. Example 2 The sectional structure of Example 2 is the same as that of Example 1 described above. Example 2 is different from Example 1 in that the composition of the reproducing layer is “G”.
d: Fe: Co = 31: 44: 25 at% "and the composition of the recording layer is" Tb: Fe: Co = 26: 59: 125 at. "
% ”.

FIG. 5 shows the temperature characteristics of the residual Kerr rotation angle of the recording layer and the reproducing layer having the above composition. As shown in the figure, the temperature at which the reproducing layer becomes a perpendicular magnetization film is 140 ° C., and the Curie temperature is 320 ° C. The Curie temperature of the recording layer is 290
° C and the compensation temperature is room temperature. That is, the Curie temperature difference between the recording layer and the reproducing layer is as small as 30 ° C. Therefore, when the temperature falls below the Curie temperature during the temperature lowering process during recording, in the reproducing layer, part of the magnetization at the transfer temperature does not face the in-plane direction. Therefore, the direction of the magnetization transferred from the reproducing layer to the recording layer is also the vertical direction, and the CNR is good.

In the case of the second embodiment, as shown as [B] in FIG. 6, recording can be performed from a low magnetic field of 100 [Oe] of externally applied magnetic field, and CNR is saturated at 250 [Oe] or more. There is. In the figure [A], the composition of the reproducing layer is “Gd: Fe: Co = 31: 34: 35 at%”, the Curie temperature is 360 ° C., and the composition of the recording layer is “Tb: Fe: C”.
o = 26: 66: 8 at% ”and the Curie temperature is 230 ° C.
FIG. 11 is a characteristic diagram of the conventional magneto-optical recording medium of FIG. As shown in the figure, conventionally, an externally applied magnetic field of 500 [Oe] or more is required. By comparison with this, it is understood that the present magneto-optical recording medium can be recorded with an extremely small externally applied magnetic field. Example 3 FIG. 7 is a schematic diagram showing a cross-sectional structure of a magneto-optical recording medium of Example 3. In the illustrated magneto-optical recording medium, a thickness of 80 is formed on a polycarbonate (PC) substrate in order from the substrate side.
High refractive index layer consisting of 0Å SiN, Gd with a thickness of 500Å
Reproducing layer made of FeCo, TbFeCo of 500 Å thickness
A recording layer made of Si, an oxidation layer made of SiN having a thickness of 800Å, a heat dissipation layer made of Al having a thickness of 200Å, and a protective layer made of an ultraviolet curable resin having a thickness of about 20 μm is formed by coating. There is. Each layer other than the protective layer can be formed by a conventionally known sputtering method or the like.

Further, magneto-optical recording media in which the film thickness 200 Å of the heat dissipation layer made of Al is replaced with 300 Å, 400 Å, 800 Å in the above, respectively were also manufactured. In each of these magneto-optical recording media, the total film thickness of the exchange-coupling magnetic layer (meaning the recording layer and the reproducing layer, meaning that the magnetization is transferred from the recording layer to the reproducing layer by the exchange-coupling force) is 1000Å. Therefore, it is a type that does not sufficiently transmit light, that is, a type that detects reflected light from the magnetic layer.

In each of the magneto-optical recording media described above, when a laser spot is incident from the substrate side to raise the reproducing layer to a predetermined transfer temperature (140 ° C. in the first embodiment), the recording layer is exposed at a portion exceeding the transfer temperature. The magnetization direction is transferred to the reproducing layer, and this phenomenon is used to read the information in the recording layer.
Since the temperature at which the spontaneous magnetization of the recording layer disappears is 250 ° C., the information of the recording layer is retained at the above transfer temperature.

In this example, the transfer temperature of the reproducing layer is 14
The temperature of 0 ° C and the temperature of 400 ° C at which the spontaneous magnetization disappears are “Gd: Fe
Co = 32: 68 at% ”, and the temperature of 250 ° C. at which the spontaneous magnetization of the recording layer disappears is“ Td: Fe ”.
It is realized by setting “Co = 25: 75 at%”. Each magneto-optical recording medium of Example 3 (the thickness of the heat dissipation layer is 2
The recorded information of each of the 00 Å, 300 Å, 400 Å, and 800 Å magneto-optical recording mediums) was read out, and the CNR was measured for each. It was better than before. Also,
The comparison between the magneto-optical recording media of Example 1 is 200
300Å was better than Å, but 300Å, 40
At 0Å and 800Å, they were about the same. From this, Al
The thickness of the heat dissipation layer may be 200 Å, but 300 Å or more is particularly suitable.

FIG. 8 is a graph showing the measurement results of the CNR of the reproduction signal of the magneto-optical recording medium of Example 3 (film thickness of the heat dissipation layer 400Å) and the conventional magneto-optical recording medium with the recording domain length as the horizontal axis. Is. As shown in the figure, it can be seen that the recording domain length is particularly improved when the recording domain length is 0.8 μm or more and 0.4 μm or less. This is because the heat of the reproducing layer flows to the heat dissipation layer and the temperature distribution becomes good. As a result, noise due to disordered magnetization direction and non-central portion of the laser spot (the peripheral low temperature portion) It is considered that this is because the noise was reduced by reading out to the state.

In the structure of Example 3 in FIG. 7, the composition ratio of the reproducing layer is changed from Gd = 30 at% (transfer temperature in this case is about 70 ° C.) to Gd = 33 at% (transfer temperature in this case is about 160 ° C.). The same results were obtained when a recording medium having different temperature ranges was prepared and CNR was measured in the same manner as above. Further, instead of Al, Ag, C having good thermal conductivity
Similar results were obtained when u, Au, W, and Mg were used as the heat dissipation layer. Example 4 FIG. 9 is a schematic view showing the cross-sectional structure of the magneto-optical recording medium of Example 4.

The magneto-optical recording medium of Example 2 is different from the magneto-optical recording medium in that the in-plane magnetic film magnetic layer made of NiO having a thickness of 500Å was provided between the high refractive index layer made of SiN and the reproducing layer made of GdFeCo. Different from Example 1, the other structures are the same as those in Example 1. The heat dissipation layer was made of Al with a film thickness of 400Å. The in-plane magnetic film magnetic layer is a layer in which the magnetization direction is in-plane in the range from room temperature to Neel temperature (100 ° C. in this example). Moreover, since it is 500 Å NiO, it has sufficient translucency so that the laser light that enters from the substrate side and is reflected by the reproducing layer returns to the substrate. This in-plane magnetic film magnetic layer is provided for the purpose of improving the CNR by aligning the magnetization direction in the initial state of the reproducing layer. That is, the direction of magnetization in the initial state of the reproducing layer is due to the influence of magnetic coupling due to the recording layer being a perpendicularly magnetized film.
It is not a perfect in-plane direction. However, there is a circumstance that the initial state of the reproducing layer affects the process in which the magnetization of the reproducing layer changes from the in-plane direction to the vertical direction during signal reproduction.
Therefore, by providing the in-plane magnetic film magnetic layer, noise due to the disordered magnetization direction and crosstalk noise due to reading a signal from a low temperature portion are reduced. Moreover, the above effect can be further enhanced by appropriately selecting the Curie temperature or the Neel temperature. As the in-plane magnetic film magnetic layer, other than NiO, CoNiO, CoO, Mn
Fe, FeCr, FeNi, PtCo, PdCo can be used.

With respect to the magneto-optical recording medium of the present Example 4, the CNR of the reproduced signal was measured in the same manner as in Example 3, and as a result, a good CNR was obtained. Further, when a recording medium having a structure without a heat dissipation layer was prepared and compared in FIG. 9, a better CNR was obtained with the recording medium of Example 4 than with the recording medium having a structure without the heat dissipation layer. Fifth Embodiment FIG. 10 is a schematic diagram showing the cross-sectional structure of the magneto-optical recording medium of the fifth embodiment.

The magneto-optical recording medium of Example 5 does not have the NiO in-plane magnetic film magnetic layer of Example 2, and G
It differs from the second embodiment in that a blocking magnetic layer made of TbFeCoAl having a thickness of 300 Å is provided between the reproducing layer made of dFeCo and the recording layer made of TbFeCo. The other structure is the same as that of the fourth embodiment, and Al having a film thickness of 400 Å is used as the heat dissipation layer as in the fourth embodiment.

The blocking magnetic layer has a spontaneous magnetization extinction temperature of 190 ° C., which is set to a temperature lower than the spontaneous magnetization extinction temperature of recording. In this embodiment, the temperature of 190 ° C. is realized by setting the Al content to 17 at%. The blocking magnetic layer is provided for the purpose of recording information on the recording layer so as not to be affected by the thermomagnetic characteristics of the reproducing layer. That is, at the time of recording information, when the temperature of the portion heated by the irradiation of the laser spot of the recording power becomes 250 ° C. or less (the temperature at which the spontaneous magnetization of the recording layer disappears) during the cooling process, the temperature is cut off at 250 ° C. Since the magnetization of the magnetic layer is 0, the magnetization of the recording layer is oriented in the direction of the externally applied magnetic field independently of the reproducing layer. When the temperature is further lowered to 190 ° C. (temperature at which spontaneous magnetization of the blocking magnetic layer disappears) or less, the magnetization direction of the blocking magnetic layer follows the magnetization direction of the recording layer. Therefore, at a transfer temperature of 140 ° C. or more at the time of reproduction, which is 190 ° C. or less, the blocking magnetic layer behaves similarly to the recording layer. As the blocking magnetic layer, other than TbFeCoAl, TbF
eCoNb, TbFeCoCr, TbFeCoNi can be used.

With respect to the magneto-optical recording medium of the fifth embodiment, the CNR of the reproduced signal was measured in the same manner as in the third embodiment.
A good CNR was obtained. Further, when a recording medium having a structure without a heat dissipation layer was prepared and compared in FIG. 10, a better CNR was obtained with the recording medium of Example 5 than with the recording medium having a structure without the heat dissipation layer. . The composition of the reproduction layer and the like will be described.

First, the compositions of the comparative example (conventional example) and Examples 6 to 14 will be shown. In the comparative example, the interference layer 2 is 800 Å and the reproducing layer 3 is 500.
Å, the recording layer 4 is formed in a thickness of 500 Å, and the protective layer 5 is formed in a thickness of 800 Å. The composition of the reproducing layer 3 is Gd: Fe: Co = 23: 65.5: 11.5 at%, and the composition of the recording layer 4 is Tb: Fe: Co = 26: 66: 8 at%. Example 6 In Example 6, the interference layer 2 is 800 Å and the reproduction layer 3 is 500.
Å, the recording layer 4 is formed in a thickness of 500 Å, and the protective layer 5 is formed in a thickness of 800 Å.

The composition of the reproducing layer 3 is Gd: Fe: Co = 31: 46: 23 at%, and the composition of the recording layer 4 is Tb: Fe: Co = 26: 66: 8 at%.

That is, in Example 6, the composition of the reproducing layer 3 is different from that of the comparative example. Example 7 In Example 7, the interference layer 2, the reproducing layer 3, the recording layer 4, and the protective layer 5 were used.
The respective film thicknesses, the composition of the reproducing layer 3 and the composition of the recording layer 4 are the same as in Example 6. Example 7 is different from Example 6 in that after the interference layer 2 is formed, the surface of the interference layer 2 is etched, and then the reproducing layer 3 is formed.

The etching conditions are reverse sputtering pressure of 1.2 mTorr, input power of 100 W and etching time of 20 min. In Example 8, the reproducing layer 3, the recording layer 4,
The respective film thicknesses of the protective layer 5, the composition of the reproducing layer 3, and the composition of the recording layer 4 are the same as in Example 6. Example 8 is different from Example 6 in that the film thickness of the interference layer 2 is 700Å. Example 9 In Example 9, the film thicknesses of the interference layer 2, the recording layer 4, and the protective layer 5 were
The composition of the reproducing layer 3 and the composition of the recording layer 4 are the same as in Example 8.

In Example 9, the thickness of the reproducing layer 3 was 1000Å.
Is different from Example 8. Example 10 In Example 10, the film thicknesses of the interference layer 2, the reproducing layer 3, the recording layer 4, the protective layer 5, and the composition of the reproducing layer 3 are the same as in Example 9. Example 10 differs from Example 9 in that the composition of the recording layer is Tb: Fe: Co = 25: 62: 13 at%. Example 11 In Example 11, the film thicknesses of the interference layer 2, the reproducing layer 3, the recording layer 4 and the protective layer 5, and the composition of the recording layer 4 are the same as in Example 10.

Example 11 differs from Example 10 in that the composition of the reproducing layer is Gd: Fe: Co = 34: 44: 22 at%. Example 12 In Example 12, the thicknesses of the interference layer 2, the reproducing layer 3, the recording layer 4, and the protective layer 5, the composition of the reproducing layer 3, and the composition of the recording layer 4 were as follows.
Same as Example 11.

The difference of Example 12 from Example 11 is that after the interference layer 2 is formed, the surface of the interference layer 2 is etched, and then the reproducing layer 3 is formed. The etching power is 0.05 W / cm ² . Example 13 In Example 13, the film thicknesses of the interference layer 2, the reproducing layer 3, the recording layer 4, and the protective layer 5, the composition of the reproducing layer 3, the composition of the recording layer 4, and
As in Example 12, the reproducing layer 3 was formed after the surface of the interference layer 2 was etched with an etching power of 0.05 W / cm ² .

The thirteenth embodiment differs from the twelfth embodiment in that an Al heat dissipation layer having a thickness of 200 Å is provided on the protective layer 5. Example 14 In Example 14, the film thicknesses of the interference layer 2, the reproducing layer 3, the recording layer 4, and the protective layer 5, the composition of the reproducing layer 3, and the composition of the recording layer 4 were as follows.
Same as Example 11.

Example 14 is different from Example 11 in that the sputtering gas pressure at the time of forming the reproduction layer 3 of Example 14 is 3.
The reproduction layer 3 of Example 11 is 5 mTorr.
The point is that the sputtering gas pressure during film formation is 7 mTorr. Next, various characteristics of the magneto-optical recording media of Examples 6 to 14 will be compared and shown. Example 6 and Comparative Example FIG. 12 is a temperature characteristic diagram of the Kerr rotation angle of Comparative Example and Example 6.

The temperature (transfer temperature) at which the reproducing layer of the magneto-optical recording medium of Example 6 became a perpendicular magnetic film was 140 ° C., and the Curie temperature was 350 ° C. On the other hand, the Curie temperature of the comparative example was 300 ° C. When a laser spot is made incident from the substrate 1 side to raise the temperature of the reproducing layer 3 to the transfer temperature,
The direction of the magnetization of the recording layer 4 is transferred to the reproducing layer 3 at a portion exceeding the transfer temperature (140 ° C. in the embodiment).

FIG. 13 shows the Kerr loops around Curie temperatures of Example 6 and Comparative Example. As illustrated, the saturation magnetic field at a temperature of 280 ° C. of the comparative example is about 500 Oe, and the saturation magnetic field at a temperature of 330 ° C. of Example 6 is about 10
It is 0 Oe. The magnitude of the saturation magnetic field at a temperature slightly lower than the Curie temperature (330 ° C. in Example 6 and 280 ° C. in Comparative Example) is related to the magnitude of the externally applied magnetic field required for recording. That is, as the saturation magnetic field increases, the externally applied magnetic field required for recording also increases.

FIG. 14 is a magnetic field modulation recording characteristic diagram of Example 6 and a comparative example. As shown, in the comparative example, 500O
Recording could not be performed unless an external magnetic field of e or more was applied. On the other hand, in Example 6, the CNR could be saturated when the externally applied magnetic field was about ± 200 Oe. Recording was possible even when the externally applied magnetic field was as low as about ± 80 Oe.

In Example 6, if the Co composition ratio in the reproducing layer was set to be greater than 50 at%, a perpendicularly magnetized film was not formed even if the temperature was raised, and the object of the present invention could not be achieved. Although the reproducing layer is made of GdFeCo in Example 6, the reproducing layer is made of another element such as GdFe.
CoCr, GdFeCoNi, GdFeCoTi, Gd
When composed of a quaternary material such as FeCoAl, GdFeCoMn, or GdFeCoNiCr, GdFeCoAl
The same effect as in Example 6 could be obtained even when the material was made of a quinary material such as Ti. Example 6 and Example 7 FIG. 15 is an image of each surface of the interference layer (underlayer) 2 of Example 6 and Example 7 observed by an atomic force microscope. In the case of Example 7, it can be seen that the surface of the interference layer 2 is smoother than that of Example 6. For this reason, the pinning force of the reproducing layer 3 and the recording layer 4 formed on the surface smoothed by the etching process of the reverse sputtering is reduced, and the domain wall is easily moved.

FIG. 16 is a characteristic diagram of magnetic field modulation recording of Example 6 and Example 7 (CNR of honor signal with respect to externally applied magnetic field).
It is. As shown in the figure, in Example 6, recording can be performed from an externally applied magnetic field of about ± 80 Oe, whereas in Example 7, recording can be performed with an externally applied magnetic field of ± 50 Oe, which is lower. You can see that it is possible.
This is considered to be due to the effect of forming the reproduction layer after smoothing the surface of the underlayer 2 by etching. Example 6 and Example 8 FIG. 40 is a magnetic field modulation recording characteristic diagram (CNR of a reproduced signal with respect to an externally applied magnetic field) of Example 6 and Example 8. As shown in the figure, in Example 8, as in Example 6, it is possible to perform recording from an externally applied magnetic field of about ± 80 Oe and further improve the recording characteristics. This is considered to be due to the fact that the interference layer 2 was formed to be slightly thinner than that of Example 6. It was confirmed that the interference layer 2 showed good characteristics when the film thickness was in the range of 600Å to 800Å. Example 8 and Example 9 FIG. 41 is a reproduction characteristic diagram (CNR of a reproduced signal with respect to reproduction laser power) of Example 8 and Example 9. As shown in the figure, the CNR sharply changes in Example 9 when the laser power at the time of reproduction is around 1.5 mW, which is considered to be due to the effect of setting 1000 Å, which is thicker than that in Example 8. To be In this way, the CNR of the reproduced signal
However, a certain value of laser power during reproduction (1.
It was confirmed that the effect of abruptly changing at a boundary of about 5 mW) was sufficiently obtained when the thickness of the reproducing layer 3 was set in the range of 800 Å to 1200 Å. Example 9 and Example 10 FIG. 42 is a recording characteristic diagram (CNR of reproduced signal with respect to recording laser power) of Example 9 and Example 10, and the laser power of the reproduced signal was 1.5 mW. As shown,
In Example 10 in which the Co composition of the recording layer 4 was changed, when the laser power of the recording signal was lower than 3 mW (>> 1.5 mW = reproducing laser power), the CNR of the reproducing signal was sufficiently lowered. On the other hand, in Example 9, the laser power of the recording signal was 2 mW (> 1.5 mW = reproducing laser power).
Only then does the CNR of the reproduced signal drop sufficiently. That is, there is a possibility that irradiation of the reproducing laser power may adversely affect the recorded signal.
0 is smaller than that in Example 9. This is considered to be the effect of setting the Co composition of the recording layer 4 to be larger in Example 10 than in Example 9. In addition, such an effect is obtained by changing the composition of Co of the recording layer 4 from 10 at% to
It was confirmed that sufficient results were obtained when the range was set to 16 at%. Example 10 and Example 11 FIG. 43 is a reproduction characteristic diagram (CNR of a reproduction signal with respect to reproduction laser power) of Example 10 and Example 11. As shown in the drawing, the CNR sharply changes in Example 11 with the laser power at the time of reproduction being close to 1.5 mW as a boundary,
The characteristics are better than those of Example 10. This is considered to be due to the effect of setting the Gd composition of the reproducing layer 3 to 34 at%, which is larger than that in the tenth embodiment. As described above, the effect that the CNR of the reproduction signal sharply changes at a certain value of the laser power at the time of reproduction (around 1.5 mW in Example 9) is due to the composition of Gd of the reproduction layer 3 being 3
It was confirmed that when it was set in the range of 0 at% to 36 at%, it was sufficiently obtained. Etching Power FIG. 44 is a characteristic diagram comparing the smoothness of the surface by changing the etching power in the case where the surface of the interference layer 2 is etched. As shown in the figure, it was confirmed that when the etching power was set to 0.05 W / cm ² , the desired smoothness was obtained by performing the etching treatment for 10 minutes or longer. Example 11 and Example 12 FIG. 45 is a characteristic diagram showing the CNR of a reproduced signal with respect to the recording domain length for Example 11 and Example 12.
As shown, in Example 12, good CNR was obtained even when the recording domain length was shorter. This is because the surface of the interference layer 2 is smoothed by the etching process.
It is considered that the domain walls were easily moved, and more stable domains were formed than in the case of Example 11. Example 13 FIG. 46 is a characteristic diagram of the magneto-optical recording medium of Example 12 in which a heat dissipation layer of Al was provided on the protective layer 5 and the CNR of the reproduction signal with respect to the thickness of the heat dissipation layer was measured. The recording domain length was 0.5 μm and 1.5 μm. As shown in the figure, it can be seen that good characteristics can be obtained by setting the thickness of the Al heat dissipation layer in the range of 200Å to 500Å. The 200 Å heat dissipation layer corresponds to Example 13. Example 11 and Example 14 FIG. 47 is a reproduction characteristic diagram (CNR of a reproduction signal with respect to reproduction laser power) of Example 11 and Example 14. As shown in the figure, the CNR of the reproduced signal changes sharply in all cases, with the laser power at the time of reproduction being around 1.5 mW, and it can be seen that good characteristics are obtained. Such good characteristics are obtained when the sputtering gas pressure at the time of forming the reproduction layer 3 is set in the range of 2 mTorr to 7 mTorr.
It was confirmed that it was sufficiently obtained.

As described above, the effect of Example 6 is that the surface state of the interference layer 2 is 0.02 W / cm ^{2 to} 0.08 W / c.
Smoothing by etching treatment with an etching power in the range of m ² , changing the film thickness of the interference layer 2 in the range of 600Å to 800Å, and changing the film thickness of the reproducing layer from 800Å to 1200Å
The content of Co in the composition of the recording layer in the range of 10 at% to 16 at%, the content of Gd in the composition of the reproducing layer in the range of 30 at% to 36 at%, and the protective layer. Al heat dissipation layer on top of 5
The same or even better can be obtained when the film is formed in the range of Å to 500 Å, or when the sputtering gas pressure during film formation of the reproducing layer is changed in the range of 2 mTorr to 7 mTorr. Example 15 In this example, a substrate for a magneto-optical recording medium, recording conditions and the like will be described with reference to the drawings and tables. The magneto-optical disk according to the present invention comprises a recording layer whose magnetic layer is a perpendicularly magnetized film and a reproducing layer which is an in-plane magnetized film at room temperature, and the magnetization of the recording layer is transferred to the reproducing layer at the time of laser light irradiation for recording. The present invention relates to a magneto-optical recording medium capable of reproducing information (hereinafter referred to as a super-resolution magneto-optical recording medium), and is a magneto-optical recording medium capable of high-density recording / reproducing. FIG. 17 is a view showing a cross-sectional structure of the magneto-optical recording medium 11 in this example, in which the interference layer 2 is formed on the translucent polycarbonate substrate 1.
And a reproducing layer 3, a recording layer 4, a protective layer 5, a heat dissipation layer 6, and an ultraviolet curable resin 7 are sequentially deposited on the interference layer 2.

First, the production of the magneto-optical disk 11 will be described. FIG. 18 shows the manufacturing process of the magneto-optical disk of the present invention. The transparent polycarbonate substrate 1 is injection-molded, SiN is deposited on the transparent polycarbonate substrate 1, and then the SiN is etched by plasma. After that, the reproduction layer 3 and the like are sequentially deposited as described above. In this embodiment, a polycarbonate substrate is used in place of the glass substrate that is conventionally used as a substrate for super-resolution magneto-optical recording medium. Therefore, the injection molding of the translucent polycarbonate substrate will be described. For injection molding of the translucent polycarbonate substrate, as shown in FIG.
The mold clamping pressure 2p, resin injection speed 3v, heating cylinder temperature 4t, and cooling time have great influences, but in this embodiment, the track pitch is 1.4, 1.2, 1.0, 0.8 μm, and groove. The width of the land was set to 1: 1 and molding was performed under the conditions of Examples 1, 2, 3 and 4 in FIG. That is, mold temperature:
118 to 125 ° C, mold clamping pressure: 180 to 220 kg / c
Injection molding was performed under the conditions of m ² , resin injection speed of 150 to 200 (mm / s), heating cylinder temperature: 310 to 340 ° C., cooling time: 9 to 13 seconds. When the transfer rate of the molded substrate was expressed by the ratio of the groove depth of the translucent polycarbonate substrate to the groove depth of the stamper, a high transfer rate of 90% or more was obtained under any condition. The surface state of the substrate molded under each condition was measured by an atomic force electron microscope (AFM), and the radius of curvature at the corner of the groove and the land was calculated from the AFM data. The results are shown in FIG. as a result,
At each track pitch, the radius of curvature was 35 to 50 nm, the maximum absolute value of birefringence was 20 to 25 nm, and the fluctuation of birefringence was 8 to 10 nm, which was good. The surface roughness of the molded polycarbonate substrate is 10 to 10.
It was as good as 50 nm. Particularly, at the track pitch of 1.4 μm used in this embodiment, the radius of curvature is 3
5 nm, the maximum absolute value of birefringence was 22 nm, and the fluctuation in the circumferential direction was 8 nm, which was good. The birefringence was measured by a double pass using a He-Ne laser with a wavelength of 633 nm.

Next, the injection-molded polycarbonate
A SiN film is formed as an interference layer 2 on the substrate by the RF sputtering method.
700 Å was deposited under the conditions shown in FIG. The SiN deposition
After that, the surface of the SiN film is planarized by plasma etching.
After that, Gd is used as the reproduction layer 3._xFe _{100- (x + y)}Co_yTo 1000
Å, Tb as recording layer 4_xFe_{100- (x + y)}Co_yTo 500
Å, SiN film is 800 Å as the protective film 5, and heat dissipation layer 6 is
And Al of 500Å and UV curable resin 7 of 10 μm are deposited.
Was.

SiN as the interference layer 2 is RF power: 500 W, Ar pressure: 5 mTor under the conditions shown in FIG.
The condition of r is more desirable. Gd _x F as the reproduction layer 3
_{e100- (x + y)} Co _y was deposited under the conditions shown in FIG. 31 by the RF binary magnetron sputtering method. RF in FIG. 31
The conditions of power: Gd; 70 W, FeCo; 200 W, Ar pressure: 7 mTorr are more desirable. Also, Gd _x F
The composition of e _{100- (x + y)} Co _y is x: 25 to 35, y: 0 to 4
The range of 0 is suitable for the magneto-optical recording medium according to the present invention,
Desirably, it is x: 30 and y: 40.

Tb _x Fe _{100- (x + y)} C as the recording layer 4
O _y was deposited by the RF magnetron sputtering method under the conditions shown in FIG. Among the conditions shown in FIG. 30, the condition of RF power: 500 W and Ar pressure: 5 mTorr is more desirable. The composition of Tb _x Fe _{100- (x + y)} Co _y is x: 1.
The range of 5 to 35 and y: 5 to 30 is suitable for the magneto-optical recording medium according to the present invention, preferably x: 22.5, y: 1.
It is 4.5. SiN as the protective film 5 was deposited by the RF magnetron sputtering method under the conditions shown in FIG. Of the conditions shown in FIG. 34, RF power: 500 W,
Ar pressure: more preferably 5 mTorr.

As the heat dissipation layer 6, Al is a target of an Al alloy such as Al-Ti, Al-Mn, or Al-Nb by the RF magnetron sputtering method.
It was deposited under the conditions shown in FIG. RF among the conditions shown in FIG.
The conditions of power: 800 W and Ar pressure: 5 mTorr are more desirable. At this time, the deposition rate of Al is 100Å /
Minutes. Further, the heat dissipation layer 6 in the present embodiment is not limited to Al, but Au, Pt, T
i, V, Cr, Mn, Fe, Co, Ni, Cu, Zn,
It may be Mo, Ag, Sn, Sb, or W. Further, not only the simple substance of the above elements, but also an alloy of any combination may be used.

An ultraviolet curable resin 7 is formed on the protective layer 6 by a usual method. Next, recording / reproducing of the magneto-optical recording medium prepared as described above will be described. Instead of the conventional recording method of irradiating a constant intensity laser beam, a pulse modulation method of pulsing the laser beam as shown in FIG. 20 was adopted. FIG. 21 shows a block diagram of the recording apparatus. The recording signal enters the synchronization pulse generation / phase delay circuit 20, and is first converted into a signal having a duty of 50% in synchronization with the recording signal.
Next, it is converted into a pulse signal whose phase is delayed by 0 to 60 ns. The pulse signal enters the pulse width changing circuit 19 and is changed into a pulse signal with a duty ratio of 20 to 60%.
It is introduced into the semiconductor laser drive circuit 18. The semiconductor laser drive circuit 18 turns on / off the semiconductor laser 15 by a pulse signal changed to a predetermined duty, and the pulsed laser light is applied to the magneto-optical recording medium 11 via the mirror 14 and the objective lens 21. It The recording signal is sent to the magnetic head drive circuit 17 as it is, the magnetic head drive circuit 17 drives the magnetic head according to the input recording signal, and each recording signal is recorded on the magneto-optical recording medium.

In the present embodiment, the relationship between the pulsed laser light and the applied magnetic field corresponding to the recording signal by pulsing the laser light is shown in FIG.
The signal is recorded during turning ON. Therefore, as qualitatively shown in FIG. 22, the conventional method of recording while constantly irradiating the laser light of constant intensity (see FIG.
The soaking area in the recording layer is narrower than that in (a)) (FIG. 22 (b)). This effect can be obtained not only by pulsing the laser light but also by depositing Al as a heat dissipation layer on the recording layer (FIG. 22B). Further, by forming the heat dissipation layer and pulsing the laser light, the above effect becomes more remarkable and the soaking area becomes narrower (FIG. 22).
(C)).

In this example, recording on the magneto-optical recording medium was performed under the conditions shown in FIG. Laser wavelength: 680n
m, numerical aperture of objective lens: 0.55, recording linear velocity: 2.0
m / s, recording frequency: 2.0 MHz is constant. The recording magnetic field, recording power, and duty of the optical pulse are shown in FIG.
Of the two conditions, ± 200 Oe, 6 mW, 40 respectively
% Is desirable.

Reproduction of a magneto-optical recording medium on which high density recording was performed with a domain length of 0.5 μm by forming a heat dissipation layer and pulsing laser light was performed under the conditions shown in FIG. The laser wavelength is 680 nm, the numerical aperture of the objective lens is 0.55, and the reproducing linear velocity is 2.0 (± 0.1) m / sec.
Of the conditions shown in FIG. 33, the reproducing power is preferably 2.0 mW or more. This reproducing power of 2.0 mW or higher has a high C in the relation between the reproducing power and the CNR at the time of reproducing shown in FIG.
The NR was determined as the reproduction power to be obtained. That is, according to FIG. 25, as the reproduction power increases, the CN
Since the R is improved and a CNR of 42 to 44 dB which is almost constant is obtained at 2.0 mW or more, a laser power of 2.0 mW or more was determined as the reproducing power for obtaining a high CNR. Also, as a result of similarly determining good reproduction power at different reproduction linear velocities, 1.1 to 1.3 m / se
At a reproducing linear velocity of c, a reproducing power of 1.5 to 2.2 mW, and at a reproducing linear velocity of 1.5 to 1.7 m / sec, a reproducing power of 1.8 to 2.7 mW, 2.9
At a reproducing linear velocity of up to 3.1 m / sec, 2.4 to 3.
Reproduction power of 7mW, 4.9-5.1m / sec
The reproducing power of 3.2 to 4.5 mW is suitable for the reproducing linear velocity of, and the reproducing power of 4.0 to 6.0 mW is suitable for the reproducing linear velocity of 8.9 to 9.1 m / sec. I found out. Further, this recording condition is also suitable for the magneto-optical recording media described in Examples 1 to 14 above.

23 and 24 show the reproducing characteristics of the above-mentioned magneto-optical recording medium for high density recording. FIG. 23 shows a laser wavelength: 68
0 nm, numerical aperture of objective lens: 0.55, pulse width of pulsed magnetic field: 500 nsec, pulse number of pulsed laser light: 4 phase difference at the time of recording (the difference between the pulsed magnetic field and the pulsed laser light) Phase difference) and C during playback
The relationship of NR (ratio of carrier and noise) is shown. Laser power at the time of recording as a parameter is 5.0, 5.5, 6.
It was changed to 0 and 6.5 mW. No phase difference during recording
In the range of up to 33 nsec, when the recording laser power increases from 5.0 mW to 5.5 mW, the CNR sharply improves from 0 to 37 to 40 dB, and the recording laser power increases from 5.5 to 6.5 mW. As a result, the CNR gradually improves. At the recording laser power: 6.5 mW, a CNR of about 43 dB was obtained.

Further, FIG. 24 shows a laser wavelength: 680 nm,
Numerical aperture of objective lens: 0.55, pulse width of pulsed magnetic field: 500 nsec, pulse number of pulsed laser light: phase difference at the time of recording (phase difference between pulsed magnetic field and pulsed laser light) ) And CNR at the time of reproduction are shown. As a parameter, the laser power during recording was changed to 4.5, 5.0, 5.5, and 6.0 mW. When the laser power during recording increases from 4.5 mW to 5.0 mW in the phase difference range of 0 to 60 nsec during recording, the CNR sharply improves from 0 to 35 dB, and the laser power during recording increases from 5.0 to 5.0 dB. The CNR gradually improves with an increase to 6.0 mW. Laser power during recording:
A CNR of up to 45 dB was obtained at 6.0 mW.

By comparing FIG. 23 and FIG. 24, in FIG. 24, the number of laser light pulses at the time of recording is reduced from four to two, so that the laser power at the time of recording showing a good CNR is 5. It shows that it can be reduced from 5 mW to 5.0 mW. The effect of the heat dissipation layer in reproduction is clear from the comparison between the conventional and the present invention in the relationship between CNR and domain length shown in FIG. That is, domain length: 0.4 to 1.5
In the present invention, the CNR during reproduction in the μm range is 1 in the present invention.
About 3 dB. The improvement of CNR is more remarkable when the domain length is shorter, so the domain length is 0.4μ.
Similar results are obtained when m or less. Further, it has been found that providing the heat dissipation layer on the recording layer is effective for reproducing a short domain length, that is, a high density magneto-optical recording medium.

Further, the film thickness of Al as the heat dissipation layer 6
Is not limited to 500Å, but 200Å ~ 1
It may be in the range of 000Å. This film thickness range is shown in FIG.
It was determined from the relationship between the Al film thickness and the reproduction resolution shown in.
That is, as the Al film thickness increases, the reproduction resolution improves,
It was decided because it becomes almost constant above 200Å. Example 16 In this example, the recording layer 4 of the magneto-optical recording medium was formed.
See FIGS. 36, 37, 38, 39, and 49.
I will explain while illuminating FIG. 36 shows the magneto-optical disk of this embodiment.
The cross-sectional structure of The production is performed by the following steps
Was. First, a normal magneto-optical image is formed on the polycarbonate substrate 31.
Like the disc, the SiN layer 32 is used as a protective film and optical enhancer.
After forming a 800 Å sputter film as a double layer, Gd₃₀Fe₅₅C
o_Fifteen33 Å 500 Å, Cr and Sb on the Mn target
(Mn₈₀Cr₂₀)_TwoSb3
4 was formed by sputtering 1000 Å. Then on it
SiN35 was deposited as a protective layer by 800Å sputtering.
After that, the UV curable resin 36 is further spin-coated to 10 μm
Formed. Table 1 shows the sputtering conditions for each of these layers.
You. The SiN layer 32 is formed under the conditions shown in FIG.
Argon gas pressure: 0.4 Pa, input power: 30
0W condition, Gd₃₀Fe₅₅Co_FifteenArgo to form 33
Gas pressure: 0.67 Pa, input power: 400 W
, (Mn₈₀Cr₂₀) _TwoArgon gas to form Sb34
Pressure: 0.67 Pa, input power: 350 W, S
Argon gas pressure for forming iN35: 0.4P
a, input power: 300 W is optimal.
Further, the ultraviolet curable resin 36 is a dripping amount: 5 cc, spin
Conditions (medium speed: 100 rpm, 2 seconds, high speed: 900 rp
m, 3 seconds), exposure time: 1 kW of halogen, 5 seconds
I spin-coated it. Produced (Mn₈₀Cr₂₀)_TwoSb3
4 is a magnetic film having a transition from antiferromagnetism to ferromagnetism
Gd₃₀Fe₅₅Co_Fifteen33 is an in-plane magnetized film at room temperature.

The prepared recording layer (Mn_100-xCr_x)_TwoS
The temperature dependence of the magnetization of b34 with Cr concentration as a parameter
The result of the investigation is shown in FIG. By increasing the Cr concentration
(Mn _100-xCr_x)_TwoSb34 conversion from antiferromagnetism to ferromagnetism
The transition point shifts to the high temperature side, and the magnetization after the transition suddenly increases.
You can see that it will increase. Also, the rise of this magnetization
Since it is steeper than the conventional example, (Mn_100-xCr_x)_TwoS
b is brighter than conventional DyFeCo in the range of 40 to 200 ° C.
Magneto-optical recording medium with accurate transfer temperature and using MSR technology
Suitable as a body material.

[0073] (Mn ₈₀ Cr _{20) 2} Sb34 results of examining the Curie temperature of, so was around constant at 230 ° C. irrespective of the Cr concentration, recorded information by heating the medium above 230 ° C.,
Track pitch 1.6 using beam of wavelength 780nm
The recording linear velocity was 5 m / sec. Playback is (M
desirably set to about 100 ° C. Since the Curie temperature of the n ₈₀ Cr _{20) 2} Sb34 is 230 ° C., in the present invention it was 20at% of Cr concentration. As shown in FIG. When the reproducing beam 66 is applied to the magneto-optical recording medium, the recording layer 62 is heated, and in the heating region 65, a transition from antiferromagnetism to ferromagnetism occurs and magnetization is expressed. When the magnetization is developed in the recording layer 62, the magnetization is not transferred to the reproducing layer 61, which is the in-plane magnetized film, and the state of the in-plane magnetized film is retained in this region, which functions as a mask. Therefore, only the information of the heating area 65 is reproduced, and reproduction in an area smaller than the irradiated beam diameter, that is, MSR reproduction is possible.
A reproduction signal suddenly appears at a reproduction power of 1.5 mW or more, and M
It turned out that SR playback is being performed. Also, with a reproducing power of 2.5 mW, the CNR of the domain 0.3 μm is 40 dB.
Met. As a result, the information in the recording layer is clearly transferred to the reproducing layer at 100 ° C. or higher, and (Mn ₈₀ C
Since there is no magnetic influence from r ₂₀ ) ₂ Sb 34 to Gd ₃₀ Fe ₅₅ Co ₁₅ 33, the mask effect is further improved, the reproduction noise is low, the MSR effect is large, and the MSR reproduction with excellent uniformity is possible. is there.

[0074] In the present invention, since the Cr concentration as _{(Mn 100-x Cr x)} 2 Sb shown in FIG. 37 results in a transition to a ferromagnetic from clear antiferromagnetic in the range of 10～30At% , Having a Cr concentration in this range (Mn _100-x Cr _x ) ₂ Sb
By applying to the recording layer, MSR reproduction similar to the above can be performed. Further, in the present invention, Gd ₃₀ Fe ₅₅ Co ₁₅ which is an in-plane magnetized film at room temperature is used as the reproducing layer, but the present invention is not limited to this, and any material that transfers the magnetization of the recording layer may be used. If an initializing magnetic field that aligns the magnetization directions of the reproducing layers is used, the perpendicularly magnetized films of TbFe, GdCo, and Tb are formed.
Co, TbFeCo, etc. are also possible. In this case, an initialization magnetic field 70 is applied as shown in FIG.
The reproduction is performed by irradiating the laser beam 66 'with the magnetization direction of the reproduction layer aligned in advance so that the magnetization 1'is directed to the recording layer 62'. In the high temperature region 65 ′, the magnetization appears in the recording layer 62 ′, so that the exchange coupling force reverses the magnetization toward the recording layer 62 ′ in the same direction as the magnetization in the recording layer 62 ′. Is transferred to the reproduction layer 61 ', information can be reproduced only in the high temperature region 65'. Further, if a perpendicularly magnetized film having a coercive force of 1 kOe or less is used, the transferred magnetic domains are self-erased, so that a mask is formed behind the beam and MSR reproduction is possible.

On the other hand, if the recording layer also has a first-order transition point, it is not limited to (Mn ₈₀ Cr ₂₀ ) ₂ Sb, but M
A magnetic material obtained by adding V, Co, Cu, Zn, Ge, and As to n2Sb may be used, and the composition of each material showing the best result is (M
n ₉₃ V ₇ ) ₂ Sb, (Mn ₇₅ Co ₂₅ ) ₂ Sb, (Mn ₉₀ Cu ₁₀ ) ₂ S
b, (Mn ₉₀ Zn ₁₀ ) ₂ Sb, (Mn ₉₀ Ge ₁₀ ) ₂ Sb, (M
n ₈₀ As ₂₀ ) ₂ Sb.

FIG. 48 shows the temperature dependence of the Kerr rotation angle in the magneto-optical recording medium disclosed in the above embodiment. Each curve in FIG. 48 is proportional to T ^c (T: temperature). From FIG. 48, 1) the thickness of the reproducing layer should be 1000 Å 2) the underlayer should be etched 3) the Co composition of the reproducing layer should be 20 at% 4) the sputtering gas pressure should be 3.5 mTorr Thus, the rise of each curve is steep, and the temperature coefficient C of the Kerr rotation angle in each curve is 8.99, 9.69, 10.9, 11.0, respectively. Therefore, in recording / reproducing using these magneto-optical recording media, higher density recording / reproducing than in the past can be performed.

[0077]

According to the present invention, the Curie temperature is 230.
In the invention in which the temperature is relatively low in the range of up to 350 ° C., it is possible to raise the temperature above the Curie temperature with a small laser power, so that a good CNR can be obtained even with a small externally applied magnetic field. Therefore, it can be optimally used also as a magnetic field modulation type recording medium.

According to the present invention, in the invention in which the Curie temperature difference between the reproducing layer and the recording layer is small, when the magnetization direction is transferred from the reproducing layer to the recording layer during recording, the magnetization direction of the reproducing layer is Is oriented in the vertical direction, and a part of the magnetization does not start in the in-plane direction, so that the in-plane magnetization is prevented from becoming noise, and as a result, a good CNR is obtained. You can

Further, according to the present invention, since the heat dissipation layer having good thermal conductivity is provided to release the heat of the exchange coupling magnetic layer,
The temperature distribution of the reproducing layer can be set to a desired distribution, so that noise due to the disordered magnetization direction and the state of the non-central part of the laser spot (the part where the temperature should be low in the periphery) can be read. There is an effect that the crosstalk noise due to the loss can be reduced.

Further, according to the present invention, by setting the composition ratio of Co in the reproducing layer within the range of 12 at% to 50 at%,
Good recording was possible even when the externally applied magnetic field was small. The CNR during reproduction was also good. Further, since the recording can be performed even when the externally applied magnetic field is small, the burden on the recording apparatus is also reduced. Further, this effect was further improved by etching the underlayer before forming the reproducing layer.

Further, according to the present invention, the heat radiation layer is provided on the recording layer of the magneto-optical recording medium or the laser beam at the time of recording is pulsed, so that the soaking area at the time of irradiation of the recording laser is narrowed. Therefore, high-density recording becomes possible. Further, according to the present invention, by providing the heat dissipation layer on the recording layer, it is possible to narrow the soaking area at the time of irradiating the reproducing laser,
High-density reproduction becomes possible.

Further, according to the present invention, a magneto-optical recording medium using a polycarbonate resin as a substrate can be manufactured. Further, according to the present invention, it is possible to manufacture a magneto-optical recording medium which is hard to break and easy to handle. Further, according to the present invention, reproduction with a high CN ratio is possible.

Further, according to the present invention, the manifestation of magnetization and the temperature of transfer during reproduction can be clarified, and a magneto-optical recording medium having low reproduction noise and excellent uniformity can be obtained. In addition, since the recording layer has no magnetization at room temperature, there is no magnetic influence on the reproducing layer, and the in-plane magnetization is further retained in the reproducing layer compared to the conventional case, so that the mask effect is improved.
The MSR effect can be increased. Therefore, a high-density recording magneto-optical recording medium can be used. Furthermore, since the transfer temperature of the magnetization is clear, it is possible to provide a medium that is easy to manufacture and low in cost.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a cross-sectional structure of a magneto-optical recording medium of an example.

FIG. 2 is a graph showing the residual Kerr rotation angle of the recording layer and the reproducing layer of the magneto-optical recording medium of the first embodiment with temperature as the horizontal axis.

FIG. 3 is a characteristic diagram showing the relationship between laser power and noise during recording on the magneto-optical recording medium of the first embodiment.

FIG. 4 is a characteristic diagram showing a relationship between an externally applied magnetic field and noise during recording in the magneto-optical recording medium of the first embodiment.

FIG. 5 is a graph showing the residual Kerr rotation angle of the recording layer and the reproducing layer of the magneto-optical recording medium of the second embodiment with temperature as the horizontal axis.

FIG. 6 is a characteristic diagram showing a relationship between an externally applied magnetic field and CNR at the time of recording in the magneto-optical recording medium [B] of the second example and the conventional magneto-optical recording medium [A].

FIG. 7 is a schematic diagram showing a cross-sectional structure of a magneto-optical recording medium of a third embodiment.

FIG. 8 is a CN of a reproduction signal of the magneto-optical recording medium of the third embodiment.
The graph which shows R.

FIG. 9 is a schematic diagram showing a cross-sectional structure of a magneto-optical recording medium of a fourth example.

FIG. 10 is a schematic diagram showing a cross-sectional structure of a magneto-optical recording medium of a fifth example.

FIG. 11 is a schematic sectional view of a magneto-optical recording medium according to sixth and seventh embodiments.

FIG. 12 shows the temperature dependence of the Kerr rotation angle in the sixth example and the conventional example.

FIG. 13 is a Kerr loop near the Curie temperature of the sixth example and the conventional example.

FIG. 14 is a recording magnetic field characteristic of the magnetic field modulation recording of the sixth example and the conventional example.

FIG. 15 is a diagram in which the surfaces of the interference layers of the seventh example and the sixth example are observed with an atomic force microscope.

FIG. 16 is a recording magnetic field characteristic of the magnetic field modulation recording of the seventh embodiment and the sixth embodiment.

FIG. 17 is a sectional structural view of a magneto-optical recording medium of the present invention.

FIG. 18 is a diagram showing a manufacturing process of the magneto-optical recording medium of the present invention.

FIG. 19 is a view showing an injection molding apparatus for a translucent polycarbonate substrate for a magneto-optical recording medium of the present invention.

FIG. 20 is a diagram showing a relationship between an applied magnetic field and a pulse laser in recording on the magneto-optical recording medium of the present invention.

FIG. 21 is a recording block of the magneto-optical recording medium of the present invention.

FIG. 22 is a diagram qualitatively showing the effect of pulsing the heat radiation layer and the laser beam in the present invention.

FIG. 23 is a diagram showing the relationship between the phase difference at the time of recording (the phase difference between the pulsed magnetic field and the pulsed laser light) and the CN ratio at the time of reproduction of the magneto-optical recording medium of the present invention.

FIG. 24 is a diagram showing the relationship between the phase difference during recording (phase difference between the pulsed magnetic field and the pulsed laser light) and the CN ratio during reproduction of the magneto-optical recording medium of the present invention.

FIG. 25 is a diagram showing the relationship between the CN ratio and the reproducing power when reproducing from the magneto-optical recording medium of the present invention.

FIG. 26 is a diagram showing the effect of the heat dissipation layer of the magneto-optical recording medium of the present invention.

FIG. 27 shows the injection molding conditions for the translucent polycarbonate substrate of the present invention.

FIG. 28 shows the characteristics of the translucent polycarbonate substrate of the present invention.

FIG. 29 shows Al film forming conditions of the present invention.

FIG. 30 shows conditions for forming the recording layer of the present invention.

FIG. 31 shows conditions for forming the reproducing layer of the present invention.

FIG. 32 shows recording conditions of the magneto-optical recording medium of the present invention.

FIG. 33 shows reproduction conditions of the magneto-optical recording medium of the present invention.

FIG. 34 is a film forming condition of the SiN film of the present invention.

FIG. 35 is a relationship between the Al film thickness and the reproduction resolution according to the present invention.

FIG. 36 is a sectional view of a magneto-optical recording medium of Example 16.

FIG. 37 is a characteristic of the recording layer of Example 16.

FIG. 38 is a schematic diagram at the time of reproduction in Example 16.

FIG. 39 is a schematic diagram at the time of reproduction in Example 16.

FIG. 40 is a characteristic diagram showing the CNR of a reproduced signal with respect to an externally applied magnetic field in Examples 6 and 8.

FIG. 41 is a characteristic diagram showing the CNR of the reproduction signal with respect to the reproduction laser power in the eighth and ninth embodiments.

FIG. 42 is a characteristic diagram showing the CNR of the reproduced signal with respect to the recording laser power in the ninth and tenth embodiments.

FIG. 43 is a characteristic diagram showing the CNR of the reproduction signal with respect to the reproduction laser power in the tenth and eleventh embodiments.

FIG. 44 is a characteristic diagram comparing the surface smoothness by changing the etching power when the surface of the interference layer 2 is etched.

FIG. 45 is a characteristic diagram showing the CNR of the reproduced signal with respect to the recording domain length for Examples 11 and 12;

46 is a characteristic diagram of the magneto-optical recording medium of Example 12, in which a heat dissipation layer of Al is provided on the protective layer 5, and the CNR of the reproduction signal with respect to the thickness of the heat dissipation layer is measured.

FIG. 47 is a characteristic diagram showing CNR of a reproduction signal with respect to reproduction laser power in Examples 11 and 14;

FIG. 48 is a temperature characteristic diagram of Kerr rotation angle.

FIG. 49 Conditions for forming recording layer, reproducing layer and protective layer in Example 16

[Explanation of symbols]

 1 ... Polycarbonate substrate 2 ... Interference layer 3 ... Reproducing layer 4 ... Recording layer 5 ... Protective layer 6 ... Heat dissipation layer 7 ... UV curable resin 1t ... Mold temperature 2p ... Mold clamping pressure 3v ... Resin injection pressure 4t ... Heating cylinder temperature 11 ... Magneto-optical recording medium 13 ... Optical head 14 ... Mirror 15 ... Semiconductor laser 16 ... Magnetic head 17 ... Magnetic head drive circuit 18 ... Semiconductor laser drive circuit 19 ... Pulse width changing circuit 20 ... Synchronous pulse generation / phase delay circuit 21 ... Objective lens

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G11B 11/10 511 9075-5D G11B 11/10 511A 521 9075-5D 521C 9075-5D 521F 586 9296- 5D 586B 9296-5D 586C (31) Priority claim number Japanese Patent Application No. 7-224387 (32) Priority date Hei 7 (1995) August 31 (33) Priority claim country Japan (JP) (31) Priority claim Number Japanese Patent Application No. 7-304345 (32) Priority Date No. 7 (1995) November 22 (33) Country of priority claim Japan (JP) (31) Priority claim number Japanese Patent Application No. 7-329915 (32) Priority Date Hei 7 (1995) November 24 (33) Priority claiming country Japan (JP) (72) Inventor Satoshi Washimi 2-5-5 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd.

Claims (30)

[Claims] 1. A transparent substrate, an underlayer formed on the transparent substrate, a reproducing layer which is an in-plane magnetized film at room temperature formed on the underlying layer, and a reproducing layer on the reproducing layer. A magneto-optical recording medium having a recording layer which is formed and is heated to a predetermined temperature to transfer the magnetization direction to the reproducing layer, and has a Kerr rotation angle temperature coefficient of 8.0 or more. A magneto-optical recording medium characterized by: 2. The magneto-optical recording medium according to claim 1, wherein the recording layer is a perpendicular magnetization film at room temperature. 3. The reproduction layer according to claim 1, wherein the reproduction layer is composed of a transition metal containing cobalt (Co) and a rare earth, and the composition ratio of Co in the reproduction layer is 12 at% to 5 at.
A magneto-optical recording medium characterized by being in the range of 0 at%. 4. The magneto-optical recording medium according to claim 3, wherein the reproducing layer contains Gd and Fe. 5. The underlayer according to claim 3, wherein the underlayer is made of SiN which functions as an interference layer.
A magneto-optical recording medium characterized by being formed into a film in the range of up to 800 Å. 6. The magneto-optical recording medium according to claim 5, wherein the thickness of the reproducing layer is in the range of 800Å to 1200Å. 7. The recording layer according to claim 3, wherein the content of Co in the recording layer is 10 at%.
A magneto-optical recording medium comprising a film of TbFeCo in the range of ˜16 at%. 8. The reproducing layer according to claim 3, wherein the content of Gd in the reproducing layer is 30 at%.
A magneto-optical recording medium comprising a film of GdFeCo in the range of ˜36 at%. 9. The surface of the interference layer according to claim 5, wherein the surface of the interference layer is 0.02 W / cm ^{2 to} 0.08 W / 0.08 W / cm ² .
A magneto-optical recording medium, characterized in that the reproducing layer and the recording layer are formed after an etching treatment with an etching power in the range of cm ² . 10. The magneto-optical recording medium according to claim 8, wherein the reproducing layer is formed at a sputtering gas pressure in the range of 2 to 7 mTorr. 11. The magneto-optical recording medium according to claim 1, wherein the translucent substrate is a polycarbonate resin. 12. The recording layer according to claim 1, 2 or 11, wherein the recording layer is TdFeCo, and the reproducing layer is GdFeCoCr or GdFeCoNi.
Or GdFeCoTi or GdFeCoAl or GdF
eCoMn or GdFeCoNiCr or GdFeCo
A magneto-optical recording medium characterized by being AlTi. 13. The magneto-optical recording medium according to claim 1, wherein a heat dissipation layer is formed on the recording layer. 14. The heat dissipation layer according to claim 13, wherein the heat dissipation layer is Al, Au, Pt, Ti, V, Cr, Mn, Fe, Co, Ni, Cu or Z.
A magneto-optical recording medium characterized by being n, Mo, Ag, Sn, Sb, or W. 15. The magneto-optical recording medium according to claim 13, wherein the heat dissipation layer has a film thickness of 200 to 1000 Å. 16. The surface of the underlayer according to claim 15, wherein the surface of the underlayer is 0.02 W / cm ^{2 to} 0.08 W / 0.08 W / cm ² .
A magneto-optical recording medium, characterized in that the reproducing layer and the recording layer are formed after an etching treatment with an etching power in the range of cm ² . 17. The heat-dissipating layer according to claim 13, wherein the heat-dissipating layer is formed by RF magnetron sputtering.
A magneto-optical recording medium formed with an RF power of up to 1000 W and an argon pressure of 1 to 10 mTorr. 18. The translucent polycarbonate substrate according to claim 11, wherein the birefringence is 20 to 25 nm, the fluctuation of the birefringence in the circumferential direction is 6 to 10 nm, and the curvature at the corner of the groove and the land. Radius is 35-50
A magneto-optical recording medium having a thickness of nm. 19. The surface roughness of the translucent polycarbonate substrate according to claim 11 or 18,
A magneto-optical recording medium characterized by having a thickness of up to 500 Å. 20. The recording layer according to claim 1, wherein the primary conversion point from antiferromagnetism to ferromagnetism is 5
A magneto-optical recording medium having a magnetic layer set at 0 ° C. or higher. 21. The method of claim 20, wherein the recording _{layer, (Mn (100-x)} M x) 2 Sb (M = Cr,
V, Co, Cu, Zn, Ge, As). 22. The magneto-optical recording medium according to claim 21, wherein M = Cr and x = 10 to 30 at%. 23. The recording method of a magneto-optical recording medium according to claim 1, wherein an externally applied magnetic field at the time of recording is 50 to 200 Oe. 24. In recording on the magneto-optical recording medium according to claim 1, the duty of the laser pulse at the time of recording is set to 20 to 60%, and the phase difference between the pulse magnetic field and the laser pulse is set to 0 to 60 nsec.
A recording method for a magneto-optical recording medium, characterized in that 25. When reproducing the magneto-optical recording medium recorded by the recording method according to claim 24, at a reproducing linear velocity of 1.1 to 1.3 m / sec, the reproducing power is 1.5 to 2.2 mW, and The reproducing power is 1.8 to 2.7 mW at the reproducing linear velocity of 0.5 to 1.7 m / sec, and the reproducing power is 2.0 to 3.0 mW at the reproducing linear velocity of 1.9 to 2.1 m / sec. , A reproducing power of 2.4 to 3.7 mW at a reproducing linear velocity of 2.9 to 3.1 m / sec, and a reproducing power of 3.2 to 4.2 at a reproducing linear velocity of 4.9 to 5.1 m / sec. A reproducing method of a magneto-optical recording medium, wherein the reproducing power is set to 5 mW and the reproducing power is set to 4.0 to 6.0 mW at a reproducing linear velocity of 8.9 to 9.1 m / sec. 26. The method of manufacturing a magneto-optical recording medium according to claim 3, wherein after forming the underlayer, the surface of the underlayer is subjected to a sputter etching treatment, and thereafter, the Co content is 12 at% to 50 at%. A method of manufacturing a magneto-optical recording medium, comprising forming a reproducing layer containing the same. 27. In claim 26, after forming the underlayer, 0.02 W / cm ^{2 is} formed on the surface of the underlayer.
A method for manufacturing a magneto-optical recording medium, which comprises performing a sputter etching process with an etching power in the range of up to 0.08 W / cm ² , and then forming a reproducing layer containing 12 at% to 50 at% of Co. 28. The Co content of the recording layer according to claim 27, wherein the content of Co is 10 at% to 16 at%.
A method of manufacturing a magneto-optical recording medium, characterized in that the film is formed of TbFeCo within the range of. 29. The reproduction layer according to claim 27, wherein the content of Gd is 30 at% to 36 at%.
A method of manufacturing a magneto-optical recording medium, characterized in that the film is formed of GdFeCo within the range of. 30. The method of manufacturing a magneto-optical recording medium according to claim 29, wherein the reproducing layer is formed at a sputtering gas pressure in the range of 2 to 7 mTorr.