JP3366261B2 - Magneto-optical recording medium - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium, and more particularly to a magneto-optical recording medium using a garnet ferrite having a large Faraday rotation angle, that is, a ferrite having a garnet type crystal structure as a magneto-optical recording material.

[0002]

2. Description of the Related Art Conventionally, commercially available magneto-optical recording media mainly use a rare earth metal material such as TbFeCo as a magneto-optical recording material, and the magneto-optical recording portion is easily deteriorated by oxidation or the like. . Therefore, it is necessary to hermetically protect the recording portion with a plastic layer or the like.

On the other hand, a recording medium using garnet ferrite or the like as a magneto-optical recording material is characterized in that the material itself is an oxide, so that the influence of deterioration is small and there is no need to take the above-mentioned special protective measures. have.

However, when garnet ferrite is used as the magneto-optical recording material, when the garnet ferrite layer is formed on the substrate surface by sputtering, stress is generated inside the layer due to thermal expansion, and as a result, the garnet ferrite layer is formed. Cracks may occur, the morphology of the layer surface may be roughened, and the crystal grains may become huge.
These are not preferable because they cause noise during recording and reproduction.

Therefore, in order to overcome the above problems,
Japanese Unexamined Patent Publication No. 8-249740 discloses that the thermal expansion coefficient of the substrate is adjusted, and reverse sputtering or the like is performed after annealing to improve the characteristics of morphology on the magneto-optical recording material layer. There is.

Further, in Japanese Patent Laid-Open No. 6-290497, by adopting a double-layer garnet ferrite structure using an underlayer of non-magnetic garnet ferrite, the grain size of the garnet ferrite layer is suppressed to 1 μm or less, It is disclosed to improve shape distortion and noise.

[0007]

However, the above-mentioned method is not practical because the process becomes complicated. Further, when a multi-layer structure is formed by garnet ferrites having different compositions, the elements of each garnet ferrite layer diffuse near the layer boundary after the heat treatment. Therefore, in the above-mentioned multilayer structure, composition deviation occurs in the direction perpendicular to the layers, which causes problems in characteristic deterioration and reproducibility. The above-mentioned garnet ferrite layer forming method cannot obtain nano-order fine crystals, which is an obstacle to high-density recording.

Further, it is generally known that garnet ferrite has a large Faraday effect, but since it expands by heat, compressive stress is generated inside the layer after heat treatment when forming a polycrystalline garnet ferrite layer on a substrate. In addition, the squareness ratio (residual magnetization /
Only a layer with a low saturation magnetization could be obtained.

An object of the present invention is to solve the above problems. That is, the object of the present invention is to improve the morphology and magnetic properties of the garnet ferrite layer by a practical method, further, by obtaining fine garnet ferrite crystal particles, high resolution, high recording density, low noise, An object is to provide a magneto-optical recording medium having an excellent S / N ratio.

[0010]

The above object is a magneto-optical recording medium having a recording layer and a reflective layer on a glass substrate, the recording layer being either a spinel ferrite layer or a rutile oxide layer. And a garnet ferrite layer. The reflective layer is preferably located between the glass substrate and the recording layer. The thickness of the garnet ferrite layer is 100 to 400 nm, and the thickness of the spinel ferrite layer or rutile type oxide layer is 10 to 10 nm.
It is preferably within the range of 0 nm.

The recording layer may include a plurality of garnet ferrite layers and a plurality of spinel ferrite layers or rutile type oxide layers. In that case, the thickness of the recording layer is preferably 100 to 1000 nm.

A groove may be formed on at least one surface of the glass substrate, the reflective layer, and the recording layer, or a loading may be provided. Here, the loading is a member for changing the effective refractive index of each layer surface, and usually has a rectangular cross section and forms a protrusion on the layer surface.

A transparent layer may be further laminated on the surface of the recording layer or the reflective layer, in which case a groove may be formed on the surface of the transparent layer.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Spinel ferrite known as one of magneto-optical recording materials, that is, ferrite having a spinel type crystal structure, has a high Faraday effect, does not cause cracks, and Fine crystals of nanometer order can be produced (Brevet Francais No.
933315258 (1993)), it is suitable for high-density recording, but the spinel ferrite layer cannot obtain a sufficient reproduction output signal because the layer itself has a large absorption coefficient. However, since spinel ferrite has a different crystal structure from garnet ferrite, it is possible to easily obtain a layer to which tensile stress is applied.

Further, with respect to rutile type oxide, which is the same inorganic oxide as ferrite, nano-order fine crystals can be produced and a layer to which tensile stress is applied can be easily obtained.

Therefore, in the present invention, by laminating the garnet ferrite layer and the spinel ferrite layer or the rutile type oxide layer, the tensile stress that the spinel ferrite layer or the rutile type oxide layer exerts on the compressive stress acting on the garnet ferrite layer. It was decided to offset by stress.

As a result, it is possible to obtain a recording layer having a large squareness ratio, a high perpendicular anisotropy, an excellent coercive force, excellent magnetic characteristics, and an improved morphology. Therefore, a recording medium suitable for magneto-optical recording can be manufactured.

When a plurality of garnet ferrite layers and a plurality of spinel ferrite layers or rutile type oxide layers are alternately or randomly laminated, the internal stress of the recording layer can be controlled in a wide range from compressive stress to tensile stress. Therefore, a recording layer having excellent magnetic properties can be easily obtained. Also, the number of heat treatments can be reduced.

The glass substrate is usually quartz glass,
Heat-resistant glass such as Pyrex glass is used. In the present invention, as the spinel ferrite, for example, Fe
_The general formula R _xy Co _y Fe _3-x O ₄ containing ₃ O ₄ and γ-Fe ₂ O ₃
(Here, 0 ≦ x ≦ 1, 0 ≦ y ≦ x, and R is one or more kinds of rare earth elements including Dy).
As the garnet ferrite, for example, comprises iron garnet, the general formula _{Bi x R 3-x + u} M y Fe 5-y + v O 12 ( wherein, 0 ≦ x ≦ 3,0 ≦ y ≦ 5, - 3 ≦ u ≦ 3, -3 ≦ v ≦ 3, R is D
One or more rare earth elements including y, M can be replaced with iron 3
Ferrite represented by (valent metal) is used. on the other hand,
The rutile type oxide is represented by RO ₂ (R is a transition metal such as Ti or Cr), and TiO ₂ is usually used. The reflective layer may be made of a metal material such as aluminum, gold, chrome or platinum.

If a reflective layer made of a metal material having a thermal expansion coefficient larger than that of glass is previously formed on a glass substrate by a sputtering method, tensile stress acts on the reflective layer after the sputtering. Therefore, when a recording layer is further laminated thereon, the compressive stress in the garnet ferrite layer is effectively reduced by the synergistic effect of the tensile stress of the reflective layer and the tensile stress acting on the spinel ferrite layer or the rutile type oxide layer. Can be offset.

When a garnet ferrite layer is formed adjacent to the spinel ferrite layer or the rutile type oxide layer, the garnet ferrite layer has a morphology due to the fine crystal grains characteristic of the spinel ferrite or the rutile type oxide at the time of crystal formation. Inherit to generate fine garnet ferrite crystals. Therefore, a garnet ferrite layer having a fine morphology suitable for high density recording can be obtained.

As a result, it is possible to obtain a magneto-optical recording medium having high resolution, high recording density and low noise. Further, it is possible to manufacture a magneto-optical recording medium having an excellent S / N ratio due to the synergistic effect of the high output due to the huge Faraday effect inherent in garnet ferrite and the reduction of noise.

When the reflective layer is located between the glass substrate and the recording layer, the reflective layer is covered with the oxide-based recording layer, which is extremely stable for a long period of time. Even if it is made of metal, it is not necessary to consider passivation, and its protective film is unnecessary. As a result, the manufacturing process of the magneto-optical recording medium can be simplified and the manufacturing cost can be reduced. Further, since the protective film does not exist during reproduction, it is possible to bring the optical pickup mechanism such as the read head closer to the recording layer substantially, and a higher S / N ratio can be secured.

Further, when a groove is formed on at least one surface of the glass substrate, the reflective layer and the recording layer and a loading is provided, the effective refractive index of the surface can be changed depending on the place. The servo control of the recording position on the recording medium can be performed by detecting the change in the reflected light from the surface due to the change in the refractive index.

When a transparent layer is further laminated on the surface of the recording layer or the reflective layer, the irradiation light is less likely to be affected by dust or scratches on the surface of the recording medium. Further, by forming a groove in the transparent layer, this groove can be used as a guide for the servo control.

The thickness of the garnet ferrite layer in the present invention is preferably 100 to 400 nm. 10
If it is less than 0 nm, it is difficult to obtain sufficient magnetic characteristics, and if it exceeds 400 nm, cracks are likely to occur. On the other hand, the thickness of the spinel ferrite layer or the rutile oxide layer is preferably 10 to 100 nm.
If it is less than 10 nm, it is difficult to obtain sufficient magnetic properties, and if it exceeds 100 nm, the layer is colored and the S / N ratio is lowered.

When the recording layer includes a plurality of garnet ferrite layers and a plurality of spinel ferrite layers or rutile type oxide layers, the thickness of the recording layer is preferably 100 to 1000 nm. If it is less than 100 nm, it is difficult to obtain sufficient magnetic properties, and if it exceeds 1000 nm, the transparency of the recording layer deteriorates.

In the present invention, the garnet ferrite layer is adjacent to the spinel ferrite layer or the rutile type oxide layer.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings. However, these examples do not limit the scope of the invention. Comparative Example First, for comparison with the present invention, a recording medium having a recording layer composed of only a spinel ferrite layer, a rutile type oxide layer and a garnet ferrite layer was prepared.

FIG. 1 shows spinel ferrite or rutile (T
FIG. 3 is a diagram showing cross sections of two types of a magneto-optical recording medium (hereinafter referred to as Comparative Example 1) having a recording layer composed of a single layer of iO ₂ ). In the example shown in FIG. 1 (a), the spinel ferrite (or rutile) layer 2 on the quartz glass substrate 1 is provided with a metal reflection layer 4
Are covered. On the other hand, in the example shown in FIG. 1B, the stacking order of the metal reflective layer 4 and the spinel ferrite (or rutile) layer 2 on the quartz glass substrate 1 is different from that in the case of FIG. 1A.

Comparative Example 1 using spinel ferrite was prepared as follows. That is, in the case of FIG. 1A, first, the spinel ferrite layer 2 made of Mn _0.13 Co _0.73 Fe _2.14 O ₄ was formed on the quartz glass substrate 1 by the high frequency sputtering method to have a thickness of 100 nm. Then 400 ° C for 10 minutes, oxygen 20%, nitrogen 80
% Heat treatment in an atmosphere of 1 atm, and then the metal reflective layer 4 was coated on the spinel ferrite layer 2.
In surface observation with an atomic force microscope (AFM), the surface roughness of the spinel ferrite layer 2 after heat treatment was 2 nm, and the crystal grain size was 30 nm or less, which was very flat.

In the case of FIG. 1B, Comparative Example 1 was prepared under the same conditions as those of FIG. 1A except that the metal reflection layer 4 was previously formed on the quartz glass substrate 1. . In the surface observation by AFM, in this case as well, the surface roughness of the spinel ferrite layer 2 was 2 nm and the crystal grain size was 30 nm or less, which was very flat.

On the other hand, Comparative Example 1 using rutile (TiO ₂ ) instead of spinel ferrite was also prepared under the same conditions as above. The surface observation by AFM is shown in Fig. 1 (a).
In both types (b) and (b), the surface roughness of the rutile layer 2 was 2 nm and the crystal grain size was 30 nm or less, which was very flat.

FIG. 2 is a diagram showing cross sections of two types of magneto-optical recording media (hereinafter referred to as Comparative Example 2) having a recording layer composed of a single garnet ferrite layer. In the example shown in FIG. 2A, the metal reflective layer 4 is laminated on the garnet ferrite layer 3 on the quartz glass substrate 1. On the other hand, FIG.
In the example shown in (b), the metal reflection layer 4 is formed on the quartz glass substrate 1.
The stacking order of the garnet ferrite layer 3 is different from that in the case of FIG.

Comparative Example 2 was prepared as follows.
That is, in the case of FIG. 2A, first, on the quartz glass substrate 1.
By high frequency sputtering method₂DyFe_FourG
aO ₁₂A garnet ferrite layer 3 made of
The thickness was 50 nm. Then, at 650 ° C for 10 minutes,
Heat treatment is performed in an atmosphere of 100% oxygen at 1 atm,
After that, the metal reflection layer 4 is placed on the garnet ferrite layer 3.
Coated Surface observation by AFM shows that after heat treatment,
-The crystal grain size of the net layer 3 is 70 nm, and the surface roughness is 4 nm.
There is a crack of 1-3 μm on the surface
It was

In the case of FIG. 2B, Comparative Example 2 was manufactured under the same conditions as those of FIG. 2A except that the metal reflection layer 4 was previously formed on the quartz glass substrate 1. In the surface observation by AFM, the surface roughness of the garnet ferrite layer 3 was 4 nm, the crystal grain size was 70 nm, and cracks of 1 to 3 μm were generated on the surface in this case as well.

Example 1 FIG. 3 shows garnet ferrite
/ Magneto-optical recording medium having a recording layer consisting of two layers of spinel ferrite (or rutile) (hereinafter referred to as Example 1)
2 is a diagram showing two types of cross sections of FIG. In the example shown in FIG. 3A, a garnet ferrite layer 3 is laminated on a spinel ferrite (or rutile) layer 2 formed on a quartz glass substrate 1, and a metal reflective layer 4 is further laminated.
On the other hand, in the example shown in FIG. 3 (b), the spinel ferrite (or rutile) layer 2 is laminated on the metal reflective layer 4 formed on the quartz glass substrate 1 in FIG. 3 (a). Not the case. In the example of FIG. 3 (a), recording / reproduction is performed by irradiating a laser through the quartz glass substrate 1 from the lower side of the figure, while in the example of FIG. 3 (b), laser light is emitted from the upper side of the figure. Recording and reproducing are performed by directly irradiating the recording layer.

Example 1 was prepared as follows.
That is, in the case of FIG. 3A, first, a spinel ferrite (or rutile) layer 2 was formed as a base layer on the quartz glass substrate 1 by a high frequency sputtering method, and Comparative Example 1
Heat treatment was performed under the same conditions as described above. Then, a garnet ferrite layer 3 having a large Faraday effect was formed on the spinel ferrite (or rutile) layer 2 by a high frequency sputtering method, and heat treatment was performed under the same conditions as in Comparative Example 2. Finally, the metal reflective layer 4 was coated on the garnet ferrite layer 3. In the case of FIG. 3B as well, the treatment was performed under the same conditions as above except that the metal reflection layer 4 was previously formed on the quartz glass substrate 1.

As the spinel ferrite, Mn _0.13 C
o _0.73 Fe _2.14 O ₄ , rutile is TiO ₂ , and garnet ferrite is Bi ₂ DyFe ₄ G
aO _{1 2} were used, respectively. The thickness of the spinel ferrite (or rutile) layer 2 and the thickness of the garnet ferrite layer 3 were 100 nm and 350 nm, respectively.

In the surface observation by AFM, no matter whether spinel ferrite or rutile is used as the underlayer and whichever structure is shown in FIGS. 3 (a) and 3 (b), after heat treatment, There are no cracks on the surface of the garnet ferrite layer 3, the surface roughness is 3 nm, and the crystal grain size is 40 n.
It was very flat below m. Thus, by using the spinel ferrite (or rutile) layer 2 as the underlayer of the garnet ferrite layer 3, the morphology of the garnet ferrite layer 3 was significantly improved.

As shown in FIG. 3 (b), the metal reflection layer 4 is made of quartz glass substrate 1 and spinel ferrite (or rutile).
When it is located between the layers 2, there is no concern about passivation of the metal reflective layer 4, and a protective means for the metal reflective layer 4 such as a coating film is not necessary. As a result, the manufacturing process of the magneto-optical recording medium can be simplified and the manufacturing cost can be reduced. Further, since the protection means does not exist at the time of reproduction, the optical pickup mechanism such as a read head can be brought closer to the recording layer, and the S / N ratio can be increased.

FIG. 4 shows the magnetization curves of the magneto-optical recording media of Comparative Examples 1 and 2 and Example 1, and FIGS. 4 (a), (b) and (c) show
Comparative Example 1 having a spinel ferrite single layer,
This corresponds to the magnetic characteristics of Comparative Example 2 and Example 1 having the garnet ferrite single layer.

Comparative Example 1 having a single layer structure of spinel ferrite has the hysteresis shown in FIG.
Specifically, the coercive force (a) is 50,000 e, the saturation magnetization (a) is 250 emu / cc, and the remanent magnetization (a) is 150 emu / c.
It was c. Therefore, Comparative Example 1 has practically sufficient characteristics (20,000 or more) with respect to coercive force.
However, the squareness value is 0.6 (residual magnetization (a) / saturation magnetization
(a) = 150/250 = 0.6), so it is practically S
A problem such as a decrease in / N ratio occurs (practically, a squareness ratio of about 0.8 or more is ideal).

On the other hand, Comparative Example 2 having a garnet ferrite single layer structure has the magnetic hysteresis characteristics shown in FIG. 4 (b), the coercive force (b) is 12000e and the saturation magnetization (b) is 13e.
mu / cc and residual magnetization (b) were 10 emu / cc. Therefore, in Comparative Example 2, the squareness value was about 0.8.
(10/13), the squareness ratio is sufficient for practical use, but since the coercive force (b) is as small as 12000e, problems such as increase in noise occur during high-density recording (2 for practical use).
An ideal coercive force of 0000e or more).

On the other hand, Example 1 having the garnet ferrite / spinel ferrite (or rutile) bilayer structure according to the present invention has the hysteresis shown in FIG. 4 (c) and the coercive force (c) is 20000e, saturation magnetization (c) is 13
The emu / cc and the residual magnetization (c) were 10 emu / cc. Therefore, the value of the squareness ratio of Example 1 is about 0.8, and practically sufficient magnetic properties are obtained in terms of both the squareness ratio and the coercive force. It should be noted that the values of the above magnetic properties were exactly the same regardless of which of the spinel ferrite layer and the rutile layer was used as the underlayer of the three garnet ferrite layers.

As described above, the recording medium having the two-layer structure of garnet ferrite / spinel ferrite (or rutile) has a problem in the recording medium having only the garnet ferrite layer or only the spinel ferrite (or rutile) layer. The magnetic properties were significantly improved. Then, in Example 1, the S / N ratio was improved by about 20 dB as compared with Comparative Example 2 regardless of whether spinel ferrite or rutile was used as the underlayer.

Example 2 FIG. 5 shows garnet ferrite
FIG. 3 is a diagram showing cross sections of two types of a magneto-optical recording medium (hereinafter, referred to as Example 2) having a recording layer formed of a multilayer laminate of / spinel ferrite (or rutile). Figure 5 (a)
In the example shown in (1), a multilayer recording layer 5 including a plurality of spinel ferrite (or rutile) layers and a garnet ferrite layer is formed on a quartz glass substrate 1, and a metal reflective layer 4 is further laminated thereon. On the other hand, in the example shown in FIG. 5 (b), the stacking order of the multilayer recording layer 5 and the metal reflective layer 4 is different from that in the case of FIG. 5 (a).

Example 2 was carried out except that a plurality of spinel ferrite (or rutile) layers and garnet ferrite layers were laminated to form the multilayer recording layer 5 and then the multilayer recording layer 5 was heat-treated collectively. It was prepared in the same manner as in Example 1. The layer structure type of FIG. 5 (a) is the case of FIG. 3 (a) of the first embodiment, and the layer structure type of FIG. 5 (b) is the case of FIG. 3 (b) of the first embodiment. , Respectively.

When the characteristics of Example 2 were examined, no matter which spinel ferrite or rutile was used as the material for forming the multilayer recording layer 5 other than garnet ferrite, the coercive force was 20000 e and the saturation magnetization was 13 emu /
cc, remanent magnetization 10 emu / cc, squareness ratio of about 0.8,
It had the same magnetic characteristic values as in Example 1. The surface roughness of the multilayer recording layer 5 after the heat treatment is 3 nm and the crystal grain size is 40.
It was less than or equal to nm. As described above, also in Example 2 having multiple recording layers, the same magnetic characteristics and morphology as Example 1 could be obtained.

In Example 2, the multilayer recording layer 5 is composed of a plurality of spinel ferrite (or rutile) layers and garnet ferrite layers, and it is not necessary to heat-treat each layer included in the recording layer. It can be reduced.

The following embodiments can also be manufactured by substantially the same method as in the first and second embodiments.

[Embodiment 3] FIG. 6 shows garnet ferrite.
/ A magneto-optical recording medium having a recording layer composed of two layers of spinel ferrite (or rutile), wherein a groove for servo control is formed on the surface (hereinafter referred to as Example 3).
2 is a diagram showing two types of cross sections of FIG. In the example shown in FIG. 6A, a garnet ferrite layer 3 is laminated on a spinel ferrite (or rutile) layer 2 formed on a quartz glass substrate 1, and a metal reflective layer 4 is further laminated. On the other hand, in the example shown in FIG. 6B, in the case of FIG. 6A, the spinel ferrite (or rutile) layer 2 is laminated on the metal reflection layer 4 formed on the quartz glass substrate 1. Is different from.

As shown in the drawing, in the third embodiment, the groove 6 is formed on the surface of the recording medium by using the silica glass substrate 1 having the groove having the width and the depth of the predetermined size on the surface. The effective refractive index there is changed depending on the place. The change in the refractive index changes the intensity of the reflected light from the medium that enters the reproducing optical pickup. By detecting this change, the servo control of the recording position on the recording medium becomes possible. That is, the groove 6 on the surface of the recording medium has a function as a guide for servo control of the recording position.

When the magneto-optical recording medium has a disk shape and is mounted on a rotating means such as an electric motor or an ultrasonic motor and rotated, the groove 6 is formed along the circumferential direction of the surface of the recording medium. On the other hand, when the recording medium is not rotated but mounted on a linear movement mechanism or a periodic vibration mechanism using a linear ultrasonic motor or a laminated piezoelectric element, the groove 6 is used.
Are formed along the straight traveling direction or the vibration direction. The groove 6 does not have to be continuous along the direction,
It may have a discontinuous pit shape.

[Embodiment 4] FIG. 7 shows garnet ferrite.
A magneto-optical recording medium having a recording layer formed of a multilayer laminated body of / spinel ferrite (or rutile), which has two types of recording medium (hereinafter referred to as Example 4) having grooves for servo control formed on the surface thereof. It is a figure which shows a cross section. Figure 7 (a)
In the example shown in (1), a multilayer recording layer 5 including a plurality of spinel ferrite (or rutile) layers and a garnet ferrite layer is formed on a quartz glass substrate 1, and a metal reflective layer 4 is further laminated thereon. On the other hand, in the example shown in FIG. 7B, the stacking order of the multilayer recording layer 5 and the metal reflective layer 4 is different from that in the case of FIG. 7A.

In the example shown in FIG. 7 (a), the quartz glass substrate 1 having grooves on the surface is used in advance. However, as in the example shown in FIG. 7 (b), it is not the quartz glass substrate 1 but metal reflection. Layer 4
It is also possible to form the groove 6 on the surface of the recording medium by forming a groove of a predetermined size on the surface of the recording medium. The groove 6
Is formed along the direction of rotation, rectilinear movement or vibration of the recording medium, and is not necessarily continuous, as in the third embodiment.

[Embodiment 5] FIG. 8 shows garnet ferrite.
A magneto-optical recording medium having a recording layer composed of two layers of spinel ferrite (or rutile), the recording medium having a servo control load on its surface (hereinafter referred to as Example 5).
2 is a diagram showing two types of cross sections of FIG. In the example shown in FIG. 8A, a garnet ferrite layer 3 is laminated on a spinel ferrite (or rutile) layer 2 formed on a quartz glass substrate 1, and a metal reflective layer 4 is coated thereon. . A load 7 made of aluminum is attached on the surface of the metal reflection layer 4. On the other hand, in the example shown in FIG. 8 (b), the metal reflective layer 4 is formed on the quartz glass substrate 1, and on the surface of the recording layer composed of the spinel ferrite (or rutile) layer 2 and the garnet ferrite layer 3. This is different from the case of FIG. 8A in that the loading 7 made of silicon oxide is directly attached to. The material of the load 7 is not particularly limited, and various metals, oxides, and dielectric materials can be used.

As described above, in the fifth embodiment, by mounting the load 7 having a predetermined size in advance, it is possible to form irregularities on the surface of the recording medium and change the effective refractive index there. Since the light reflectance changes due to this change in the refractive index, servo control of the recording position on the recording medium becomes possible by detecting this change. That is, the loading 7 on the surface of the recording medium has a function as a guide for servo control of the recording position.

When the magneto-optical recording medium is disc-shaped and is mounted on a rotating means such as an electric motor or an ultrasonic motor and rotated, the load 7 is attached along the circumferential direction of the recording medium. On the other hand, when the recording medium is not rotated but mounted on a linear movement mechanism or a periodic vibration mechanism using a linear ultrasonic motor or a laminated piezoelectric element, the loading 7 is attached along the linear movement direction or the vibration direction. To be The loading 7 does not have to be continuous along the direction.

Example 6 FIG. 9 shows garnet ferrite
A cross section of two types of magneto-optical recording medium having a recording layer formed of a multilayer laminate of spinel ferrite (or rutile), the recording medium having servo loading on its surface (hereinafter referred to as Example 6). FIG. Figure 9 (a)
In the example shown in FIG. 3, the metal reflective layer 4 is formed on the multilayer recording layer 5 formed on the quartz glass substrate 1 and including a plurality of spinel ferrite (or rutile) layers and garnet ferrite layers.
Are laminated, and a load 7 made of aluminum is attached on the surface of the metal reflective layer 4. On the other hand, FIG.
In the example shown in (b), the multilayer recording layer 5 is laminated on the metal reflective layer 4 formed on the quartz glass substrate 1, and the loading 7 made of silicon oxide is directly attached on the surface thereof. Different from the case of 9 (a)

In the case of the sixth embodiment as well, as in the fifth embodiment, the material of the loading 7 is not particularly limited, and various metals,
An oxide or a dielectric material can be used, and the unevenness formed by the load 7 can be used as a guide for servo control of the recording position. Note that the loading 7 is formed along the rotation, traveling or vibration direction of the recording medium, and is not necessarily continuous, as in the fifth embodiment.

[Embodiment 7] FIGS. 10A and 10B show a type in which a transparent layer is further formed on the surface of the magneto-optical recording medium shown in FIGS. 3B and 5B, respectively. FIG. 9 is a cross-sectional view of a magneto-optical recording medium (hereinafter referred to as Example 7). Although polycarbonate is used as the material of the transparent layer 8 in Example 7, the transparent layer 8 may be made of another transparent material, if necessary. The thickness of the transparent layer 8 is appropriately set within the range of 100 nm to 2 mm.

Thus, by providing the transparent layer 8 on the surface of the recording layer, compatibility with the conventional medium surface can be obtained, and the distance between the recording layer on which recording is actually performed and the surface of the recording medium is performed. Can be extended. Therefore, even if dust or scratches occur on the surface of the recording medium, the laser emitted from the reproducing head and focused on the recording layer is not easily affected by dust or scratches on the surface of the recording medium. Become.

Here, if the optical thickness of the transparent layer 8 on the recording medium is sufficiently shorter than the wavelength of light used in magneto-optical recording (for example, 700 nm or less), Example 7 will be described.
Can be used as a near-field light magneto-optical recording medium that uses near-field light that exudes from the surface of the recording medium by a distance of about the wavelength. On the other hand, if the optical thickness of the transparent layer 8 is about the wavelength of the light or more, the embodiment 7
It can be used as a far-field magneto-optical recording medium used in an optical system including a general condenser lens.

[Embodiment 8] FIGS. 11A and 11B are of a type in which a transparent layer is further formed on the surface of the magneto-optical recording medium shown in FIGS. 6B and 7B, respectively. FIG. 9 is a cross-sectional view of a magneto-optical recording medium (hereinafter referred to as Example 8). Thus, by covering the recording layer having the groove for servo control with the transparent layer 8, the effective refractive index and the reflectance can be changed inside the recording medium. Therefore, in the eighth embodiment, when the servo control of the recording position is performed, the change in the reflectance of the light inside the recording medium can be detected and controlled, the influence from the external environment can be eliminated, and more accurate control can be performed. It becomes possible to do.

In the eighth embodiment, since the laser beam emitted from the reproducing head is focused on the recording layer inside the recording medium, it is less susceptible to dust and scratches on the surface of the recording medium. The grooves on the surface of the recording layer are formed along the direction of rotation, rectilinear movement or vibration of the recording medium. The groove need not be continuous.

[Embodiment 9] FIG. 12 shows the transparent layer 8 of Embodiment 8.
The magneto-optical recording medium subjected to the flattening treatment (hereinafter, referred to as Example 9).
Is a sectional view of FIG. In FIG. 12B, the quartz glass substrate 1 having a groove on the surface is used. By the flattening process, in addition to the effect of the eighth embodiment, it becomes possible to record and reproduce information by moving the optical pickup mechanism close to the surface of the recording medium rotating at high speed. The approach to the surface of the recording medium is performed, for example, by mounting an optical pickup mechanism on a flying slider head that is commonly used in magnetic recording disk drives.

[Embodiment 10] FIGS. 13A and 13B are of a type in which a transparent layer is further formed on the surface of the magneto-optical recording medium shown in FIGS. 8B and 9B, respectively. It is a schematic sectional drawing of the magneto-optical recording medium (henceforth Example 10). Example 1
Also for 0, the same effect as that of the ninth embodiment can be obtained. The loading 7 on the surface of the recording layer is formed along the direction of rotation, rectilinear movement or vibration of the recording medium. The loading 7 does not have to be continuous as in the fifth embodiment.

[Embodiment 11] FIGS. 14A and 14B show servo control grooves 6 on the surface of the transparent layer 8 of the magneto-optical recording medium shown in FIGS. 10A and 10B, respectively. It is a schematic sectional drawing of the formed type magneto-optical recording medium (henceforth Example 11). This makes it possible to detect the change in reflectance on the surface of the transparent layer 8 and servo-control the recording position. In addition, compatibility with the conventional medium surface can be achieved, and the distance between the recording layer on which recording is actually performed and the recording medium surface can be widened. Therefore, even if dust or scratches occur on the surface of the recording medium, the laser emitted from the reproducing head and focused on the recording layer is not easily affected by dust or scratches on the surface of the recording medium. Become. The groove 6 on the surface of the transparent layer 8 is formed along the rotation, rectilinear or vibration direction of the magneto-optical recording medium. The groove 6 need not be continuous.

[0070]

According to the present invention, it is possible to manufacture a garnet ferrite recording medium having good magnetic characteristics and suitable for a magneto-optical recording medium without going through a complicated process. Moreover, since no metal-based material is used as the magneto-optical recording material, there is no problem of passivation.

Since a garnet ferrite layer having a fine morphology suitable for high density recording can be obtained, a magneto-optical recording medium with high resolution, high recording density and low noise can be manufactured. Further, the S / N ratio is greatly improved compared to the conventional one by the synergistic effect of the high output obtained by the huge Faraday effect originally possessed by garnet ferrite and the low noise.

When the reflective layer is located between the glass substrate and the recording layer, the protective film for the reflective layer is not necessary even if the reflective layer is made of a metal material, so that the magneto-optical recording medium is manufactured. It is possible to simplify the process and reduce the manufacturing cost. Further, since the protective film does not exist during reproduction, it is possible to bring the optical pickup mechanism such as the read head closer to the recording layer substantially, and a higher S / N ratio can be secured.

When the recording layer includes a plurality of garnet ferrite layers and a plurality of spinel ferrite layers or rutile type oxide layers, the number of heat treatments for producing the recording layer can be reduced. Further, since the internal stress of the recording layer can be finely controlled, a recording layer having excellent magnetic characteristics can be easily obtained.

Further, when a groove is formed on at least one surface of the glass substrate, the reflection layer and the recording layer and a loading is provided, servo control of the recording position on the recording medium becomes possible.

When a transparent layer is further laminated on the surface of the recording layer or the reflective layer, the irradiation light can avoid the influence of dust or scratches on the surface of the recording medium. Further, when a groove is formed in the transparent layer, this groove can be used as a guide for the servo control.

[Brief description of drawings]

FIG. 1 is a diagram showing cross sections of two types of magneto-optical recording media having a recording layer composed of a single layer of spinel ferrite or rutile.

FIG. 2 is a diagram showing cross sections of two types of magneto-optical recording media having a recording layer composed of a single garnet ferrite layer.

FIG. 3 is a diagram showing cross sections of two types of magneto-optical recording media having a recording layer composed of two layers of garnet ferrite / spinel ferrite (or rutile).

FIG. 4 is a diagram showing magnetic history curves of magneto-optical recording media of Comparative Example and Example 1.

FIG. 5 is a diagram showing two types of cross sections of a magneto-optical recording medium having a recording layer composed of a multi-layer laminate of garnet ferrite / spinel ferrite (or rutile).

FIG. 6 shows two types of cross sections of a magneto-optical recording medium having a recording layer composed of two layers of garnet ferrite / spinel ferrite (or rutile), in which grooves for servo control are formed on the surface. Fig.

FIG. 7 is a magneto-optical recording medium having a recording layer composed of a multi-layer laminate of garnet ferrite / spinel ferrite (or rutile), in which two types of cross sections of the recording medium having servo control grooves formed on the surface are shown. FIG.

FIG. 8 shows cross sections of two types of magneto-optical recording media having a recording layer composed of two layers of garnet ferrite / spinel ferrite (or rutile), which has a servo control load attached to the surface thereof. Fig.

FIG. 9 is a magneto-optical recording medium having a recording layer composed of a multi-layer laminate of garnet ferrite / spinel ferrite (or rutile), and showing a cross section of two types of the recording medium having a servo control load attached to the surface thereof. FIG.

FIG. 10 is a cross-sectional view of a magneto-optical recording medium of a type in which a transparent layer is further formed on the surface of the magneto-optical recording medium shown in FIGS. 3B and 5B.

FIG. 11 is a sectional view of a magneto-optical recording medium of the type shown in FIGS. 6B and 7B, in which a transparent layer is further formed on the surface of the magneto-optical recording medium.

FIG. 12 is a cross-sectional view of a magneto-optical recording medium in which a transparent layer of Example 8 is flattened.

FIG. 13 is a sectional view of a magneto-optical recording medium of the type shown in FIGS. 8B and 9B, in which a transparent layer is further formed on the surface of the magneto-optical recording medium.

FIG. 14 is a sectional view of a magneto-optical recording medium of the type shown in FIGS. 10A and 10B, in which grooves for servo control are formed on the surface of the transparent layer of the magneto-optical recording medium.

[Explanation of symbols]

1: Quartz glass substrate 2: Spinel ferrite (or rutile) layer 3: Garnet ferrite layer 4: Reflective metal layer 5: Multi-layer recording layer 6: groove 7: Loading 8: transparent layer

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Yoshikawa 3-21-3 Nishishinjuku, Shinjuku-ku, Tokyo Inside Nippon Telegraph and Telephone Corporation (72) Toshifumi Okubo 3-19-3 Nishishinjuku, Shinjuku-ku, Tokyo No. 2 Nihon Telegraph and Telephone Corporation (72) Inventor Manabu Yamamoto 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Nihon Telegraph and Telephone Corporation (72) Inventor Colin Despax France Paris Michelangele Street 3 Center -National de la Recherche Scientific (72) Inventor Philippe Tayad France Paris Michel Ange Street 3 Center National de la Recherche Scientific (72) Inventor Laurence Buet France Toulouse Cux Narbonne street 118 Universite Paul Sabattiere (72) Inventor Abel Ruse France Toulouse Cedex Narbonne street 118 Universite Paul Sabattiere (56) Reference JP-A-60-150614 (JP, A) Flat 9-81978 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G11B 11/105

Claims (3)

(57) [Claims] 1. A magneto-optical recording medium having a recording layer and a reflective layer on a glass substrate, wherein the recording layer includes either a spinel ferrite layer or a rutile type oxide layer and a garnet ferrite layer. The garnet ferrite layer is formed adjacent to the spinel ferrite layer or the rutile type oxide layer after the spinel ferrite layer or the rutile type oxide layer is formed. . 2. The magneto-optical recording medium according to claim 1, wherein the reflective layer is located between the glass substrate and the recording layer. 3. The magneto-optical recording medium according to claim 1, wherein the recording layer includes a plurality of garnet ferrite layers and a plurality of spinel ferrite layers or rutile type oxide layers.