JPS60263357A - Photomagnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a photomagnetic recording medium which is free from deterioration due to the aging or heat and excels in the sensitivity, etc., by holding a metallic oxide magnetic layer of a hexagonal system or spinel system having a specific composition between light transmissive dielectric layers having absolute diffractive indexes higher than a specific level and setting them on the surface of a reflecting layer formed on a heat-resistant substrate. CONSTITUTION:A metallic oxide magnetic layer of a hexagonal system shown by an equation I (Me: >=1 kind among Ba, Pb, and Sr; M I : >=1 kind among Ga, Al, Mn and Cr; MII: >=1 kind among 38 elements including Sc, Ta, etc.; m and n: ion-valent numbers of M I and MII; x and y: substitution element numbers of M I and MII; 5<=A<=6, 0<x<=1.0, 0<y<=0.5) or a metallic oxide magnetic layer 3 of a spinel system shown by an equation II (M: >=1 kind among 22 elements including Mn, Al, Cr, etc.; n: ion-valent number of M; 0<x<=0.8, 0.2<y <1.0) is held between light transmissive dielectric layers 5 and 5' having high diffractive indexes containing CeF3 of >=1.7 absolute diffractive index and then put on a reflecting layer 2 formed on a heat-resistant substrate 1. Then a transparent protection layer 4 is formed on the layer 5. Thus a recording medium is obtained with use of a semiconductor laser.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a magneto-optical recording medium for recording and reproducing information using semiconductor laser light.

BACKGROUND OF THE INVENTION In recent years, magneto-optical recording media for performing magnetic recording and reproduction using semiconductor laser light have been researched and developed for high-density recording. The most basic type of magneto-optical recording medium is one in which a magnetic film that can be magnetized perpendicular to the substrate surface is provided on a heat-resistant transparent substrate such as quartz glass by a method such as sintering or vacuum evaporation. It is. Here, the material for the magnetic film is an amorphous alloy of a rare earth metal and a reduced metal (for example, Tb -
A magnetic material made of (Fe alloy) is mainly used. Recording and reproduction on such a magneto-optical recording medium are performed as follows.

That is, recording is performed at the Curie temperature or compensation temperature of the magnetic film.
[K Oyu, Oyu I6. Ka9ikaeka. This is done by heating the magnetic film by irradiating it with a laser beam modulated by a binary signal, making use of the 1□ change characteristic, and reversing the direction of magnetization. In the reversible reproduction, polarized laser light is irradiated onto the magnetic film that has been recorded in reverse in this way, and the polarized light wI is rotated according to the direction of magnetization using the difference in the magneto-optic effect of the magnetic film, and this is converted into binary data. Yukihiko is detected by detecting it as a symbol.

In the above-mentioned recording and reproducing methods, AI, Cu, Ag
It has also been proposed to use a recording medium provided with a reflective film such as Pt, Au, or the like.

Magneto-optical recording media using amorphous alloy magnetic materials as mentioned above all have high recording sensitivity, so they have the advantage of being able to record at high speeds (at a frequency of IMHz) using semiconductor laser light. Magnetic materials, especially rare earth metal components, are susceptible to oxidative corrosion, and therefore, a major drawback is that the magneto-optical properties of the magnetic film deteriorate over time, especially those with a protective film. To prevent this, a protective layer such as sto, sto, etc. is provided on the amorphous magnetic film (
It is also known that the formation method is generally the same as in the case of magnetic films (vacuum deposition, sputtering, etc.); however, when forming a magnetic film or protective layer, o, which remains in vacuum and is adsorbed to the surface of the substrate.

H, 0, etc. and O contained in the alloy magnetic target,
, H2O, etc. over time, and this oxidative corrosion is further accelerated by light and heat during recording. In addition, amorphous magnetic materials have the disadvantage that they are easily crystallized by heat, which tends to cause deterioration of the magnetic light quantity characteristics.

Since these defects are caused by the material of the magnetic film, the same can be said of recording media provided with a protective film.

Furthermore, in this type of recording medium, the effect of improving the reproduction output by the reflection method was also insufficient.

Object The object of the present invention is to provide a magneto-optical recording medium which exhibits almost no deterioration of magneto-optical properties due to aging or heat, has high recording sensitivity, and has improved reproduction output.

Structure The present invention provides a magneto-optical recording medium having a magnetic layer and a reflective layer on a heat-generating substrate, in which the magnetic layer has the general formula (1) % formula % (1) (where Me=at least 18 of Ba, Pb, and Sr). [Above, M1= Ga, AI, Mn,
At least one kind of Cr, Ml (=Sc, Ta, Ti
, Zn, Sn, Go.

In, Bi, Y, Tb, Yb, S
m, V, Gd, Dy.

Ho, Er, Eu, Yb, Pr,
Co, Mg, B, Mo.

W, Os, Pt, Ag, Au, P
d, Ru, Rh, Re.

At least one of Ir, Sb, Tm, Pm, and Th is represented, m and n are the ion valences of Ml and Mi, respectively, XmY is the number of substituted atoms of Ml and MX, respectively, and A, x, and y are each 5≦A≦6.0 (x≦1
It is within the range of -0+0<y≦0.5. ) or the following general formula (2) [Coy] [MxFel-Ja-, o4 (21 (however, M
=Mn, AI, Cr, Ga, In, S
o, Zn.

Ti, Mg, Ta, Pt, Ag, Pt, 8
n, Bl, V.

Sm, Gd, Rh, Ru, Pr,
At least one type of Y is represented, X+7 is the number of substituted atoms of Co and M, n is the ion valence of M, and x and y are 0.
(x≦0.8, 0.2 (y (within the range of 1.0) It is characterized by being sandwiched between dielectric layers with a high refractive index.

The magnetic material or magnetic film used in magneto-optical recording media has magneto-optical properties (
In particular, in order to obtain high recording sensitivity, the Curie temperature Tc must be low, and in order to maintain the recorded memorization stability, the coercive force Ha must be moderate. It is necessary to have a high

Generally, the appropriate range for Tc and Hc is 1 for Tc.
00-350°C, HC is considered to be 300-6000 oersted.

Hexagonal and spinel metal oxide magnetic materials have been studied as magnetic bubble materials. Hexagonal crystal systems are known, for example, those represented by the general formula (3)% formula (3) (where Me and A are the same as in general formula (1)), and spinel systems such as CoF
e104 is known. The present inventors have focused on the fact that since the above type of magnetic material is itself a chemically resistant material, there is a high risk of oxidative deterioration.

However, since the Curie temperature Tc of these materials is as high as 450° C. or higher, recording with semiconductor laser light is difficult as described above, and they cannot be used as is as a material for magneto-optical recording media. Therefore, the present inventor conducted various studies and found that when some of the Fe atoms of the magnetic material of general formula (3) and CoFe104 are replaced with specific other metal atoms, the Tc decreases, and the magnetic layer for the magneto-optical recording medium is Gold [2
Discovered a compound magnetic material.

Furthermore, the present inventor focused on using a material with a Faraday effect for the purpose of further improving the reproduction output in a conventional magneto-optical recording medium having a reflective layer, and used SlO and TIO□ as the material.

It has been discovered that the above object can be achieved by using a high refractive index inorganic transparent dielectric material such as Th01, Ce01, 810g, TiO, etc. and sandwiching the above magnetic layer as a light-transmitting high refractive index dielectric layer, and the present invention has been made based on this discovery. This is what we have come to.

Next, the basic layer structure of the present invention will be explained, focusing on the advantages of sandwiching a light-transmitting dielectric layer with a high refractive index between the magnetic layers. Figures 1 to 6 show schematic cross-sectional views of magneto-optical recording media, of which Figure 1 shows one without a transparent high refractive index dielectric layer, and Figures 2 and 3 show a magnetic layer. FIGS. 4 to 6 show a structure according to the present invention in which a magnetic layer is sandwiched between light-transmitting dielectric layers with a high refractive index. In the figure, 1 is a heat-resistant substrate, 2 is a reflective layer, 3 is a magnetic layer, 4
5.5' is a transparent high refractive index dielectric layer, 6 is a laser beam, 7 is a void layer, and 8 is a spacer.

FIG. 1 shows a recording medium in which a reflective layer 2, a magnetic layer 3, and a protective layer 4 are sequentially laminated on a heat-resistant substrate 1.

When this recording medium is irradiated with a laser beam 6 in a substantially perpendicular direction and the reflected light from the recording medium is received by a photodiode, for example, as a reproduction signal, the Kerr rotation angle θ of the reflected light from the magnetic layer 3 3, reflected by the reflective layer 2, and transmitted through the magnetic layer 3 again at a Faraday rotation angle θ1. The Kerr rotation angle and Faraday rotation angle are based on the fact that the plane of polarization rotates depending on the direction of magnetization of the magnetic layer 3, but in the Kerr rotation angle and Faraday rotation angle, the direction of magnetization is opposite and the rotation of the plane of polarization is in the opposite direction. Become. Therefore 01. It can be said that extracting only this is good for reproduction characteristics. In FIG. 2, a transparent high refractive index dielectric layer 5 is provided on the magnetic layer 3. Here, the thickness of the transparent high refractive index dielectric layer 5 is dl, the absolute refractive index is n, and the refractive index of the magnetic layer 3 is k.
n,, the refractive index of the protective layer 4 is n, then d,=λ(2
N+1)/4n (λ is the wavelength of the laser beam, 10-N=0.1.2..., n=s/"stripes-i), the translucent high refractive The reflected light θ from the dielectric layer 5 and the reflected light θ from the magnetic layer 3 cancel each other out. FIG. A dielectric layer 5' is provided.Here, if the thickness of the transparent high refractive index dielectric layer 5' is d2, the refractive index of the magnetic layer 3 is n11, and the refractive index of the reflective layer 'fc n, d
,=λ(2N+1)/2n(N=0,1.

2..., ""r), θ12
and θr1 are synergistic.

For this reason, as shown in FIG.
When i is provided, θh and θ■ are canceled out, and θI
All phases I and θl can be placed on top of each other. This makes it possible to increase the Faraday rotation angle and improve reproduction output.

The thickness of the transparent high refractive index dielectric layers 5 and 5' is 1 as described above, d,=λ(4N+1)/4n and d,=λ(2N+1)
It is desirable to satisfy /2n. The present invention can also be applied to a substrate having a pregroove as shown in FIGS. 5 and 6. In FIG. Refractive index dielectric layer 5 and protective layer 40
A void layer 7 is provided in between. In FIG. 6, the protective layer 4 has a pregroove, and a gap layer 7 is provided between the reflective layer 2 and the transparent high refractive index dielectric layer 5', and the laser beam is irradiated from the substrate 1 side. Ru.

The magnetic layer of the present invention is made of a metal oxide magnetic material represented by the general formula (1) or (2), and specific examples thereof include the following.

(Left below) ^ Ro Ro Ro Ro Ro Ro Ro Ro Ro Ql+C'
J F-I C4x vs cQrs cQC4ww
cotowtouuit.

-I to cL> size roto ω ■ Roda 5
! Ta da ta da 5! , 5! Da Da 13-He Ro Ro Ro Ro Ro LotlQ -Ro Ro 00 Ro Sendan -1-@Sen 0 Medium To 14- These metal oxide magnetic materials are Fe@0B or Co20
In addition to B, oxides of predetermined metal atoms are mixed and pulverized with a predetermined sound,
After putting this into a mold of an appropriate shape and molding it,
It is made by sintering at a temperature of 400°C.

In order to form a magnetic layer using the metal oxide magnetic material described above, the magnetic material is generally placed on a transparent substrate at a substrate temperature of 400 to 600°C, although it depends on the type of substrate.
The film may be deposited to a film thickness of about 0.1 to 1 opm by a method such as suffix 9 rolling, vacuum evaporation, or ion silating. In some cases, the magnetic layer can be formed at a substrate temperature of less than 400°C. However, in this case, after forming the magnetic layer, it is necessary to perform a heat treatment at 400 to 700 DEG C., sometimes with repeated application of a magnetic field, to achieve perpendicular magnetization.

Here, the substrate material is general glass, quartz glass;
GGG; S1 Fire; Lithium tantalate; Crystallized transparent glass; Pyrex glass; Single crystal silicon with or without surface oxidation treatment; Al, 0. .

AIIOIm MgO, MgO* LiF, YIOB
”LiF, BeO.

Transparent ceramic materials such as zyo, @YIOB, Th01 @CaO; inorganic materials such as inorganic silicon materials (for example, Toshiba Silicon Co., Ltd. Toss Guard, Sumitomo Chemical Co., Ltd. Sumiceram P) can be used.

The light-transmitting high refractive index dielectric layer is made of an inorganic transparent electrically shielding material having an absolute refractive index of 1.7 or more. As an inorganic transparent dielectric material,
Ce02(2,2), ZrO,(2,1).

CeFl(1,7), Mg0(1,74), T
ie, (2,5).

At, 0. (1,7) , Bi, O, (1,9) ,
WO, (2,0), Zn8(2,1), 810
(2,0), Sl, N, (2,3), etc. are used. Values in parentheses indicate absolute refractive index. The light-transmitting high refractive index dielectric layer can be formed by depositing the above-mentioned material by sputtering, vacuum deposition, ion silating, or the like, as in the case of the magnetic layer.

As before, the reflective layer is made of Cu, AI, Ag,
Au.

Ni, PL, TeOx, TeC, 5eAs
, TeAs, TiN.

It is composed of TaN, CrN, cyanine dye, phthalocyanine dye, etc. The method for forming the reflective layer is exactly the same as the conventional method, using the above materials. It may be deposited to a film thickness of about 0.02 to 0.5 μm by a method such as footing, vacuum deposition, or ion silating. The reflective layer thus obtained has the effect of increasing the Faraday effect by reflecting the laser beam that has passed through the magnetic layer and transmitting it through the magnetic layer again, thereby improving the reproduction output in the same way as the transparent high refractive index dielectric layer. have.

The protective layer is the same as before, 810, 810*, TIN
.

It is composed of 81N, TaN, acrylic resin, polyurethane resin, polycarbonate resin, polyether sulfone resin, polyamide resin, epoxy resin, etc. The method of forming the protective layer is the same as before, and in the case of resin, a coating method is used, and in the case of other methods, a film thickness of approximately 0.1 to 10 μm is applied to the target surface using methods such as vacuum evaporation, sputtering, and ion blasting.
It is formed by adhering to about m.

Effects According to the present invention, there is no fear of oxidative deterioration in the magnetic layer, and a metal oxide magnetic material having a Curie temperature and coercive force suitable for use as a material for magneto-optical recording media is used, and at the same time, the magnetic layer is free from oxidative deterioration. Since the layers are sandwiched between light-transmitting dielectric layers with a high refractive index, the magneto-optical properties tend to deteriorate over time and the recording sensitivity is high. Furthermore, sufficient reproduction output can be obtained due to the improvement of the Faraday effect.

Example 1 A film thickness of 5ooXo*g as a reflective layer on a heat-resistant quartz substrate
was attached by vapor deposition. On top of this, a transparent high refractive index @electrolayer 810 was deposited with a thickness of 1aooX by sputtering method,
Further, while maintaining the substrate temperature at 400 to 700°C, the Nl
A magnetic layer of l to rVk116 was deposited to a film thickness of aooX using the star bulging method to form a magnetic layer, and a polymethyl methacrylate retaining plate was bonded thereon to obtain a magneto-optical recording medium.

Example 2 On a substrate with Ni electroformed guide tracks, an AI layer having a thickness of 100X was deposited as a reflective layer by vapor deposition.

On top of this, CeO was deposited to a thickness of 18-1000X by sputtering, and then the magnetic material of Nnl to N11116 was deposited to a thickness of 5000mm to form a magnetic layer, and then CeO1 was deposited to a thickness of 1000X. was bonded to a polymethyl methacrylate protective substrate via a spacer to obtain a magneto-optical recording medium.

Example 3 SI was deposited on a non-equal glass substrate by sputtering method.
O □ is attached to the film too
[A magnetic material of 116 was deposited to a thickness of 5000X, and a T
10. was deposited to a film thickness of 1000 to obtain a recording medium.

On the other hand, a reflective layer was deposited on a polymethyl methacrylate substrate with a guide rack obtained by the injection method to a thickness of 1000× by the Cu f evaporation method. The reflective layer side of this pregroove plastic substrate with a reflective layer was joined to the translucent high refractive index @electrolayer TIO side of the recording medium via a spacer to obtain a magneto-optical recording medium.

゛ Next, the magneto-optical recording medium obtained as described above was magnetized in one direction, and then an output of 20 m was applied while applying an external magnetic field of 0.5 oersted in the opposite direction to the magnetic direction.
When recording was performed by irradiating with a W semiconductor laser with an IMHz pulse to cause magnetic reversal, minute pits were recorded in each case. Next, the medium was irradiated with a laser output of 2 mWf, and the reflected light from the recorded bits of the medium was passed through the analyzer and received by the Apparasia photodiode, and a signal was reproduced.

[Brief explanation of drawings]

1 to 6 show schematic cross-sectional views of magneto-optical recording media,
Among these, FIG. 4 to FIG. 6 show what is related to the present invention. 1... Heat-resistant substrate 2... Reflective layer 3... Magnetic layer 4... Retention layer 5.5'... Transparent high refractive index dielectric layer

Claims (1)

[Claims] 1. In a magneto-optical recording medium having a magnetic layer and a reflective layer on a heat-resistant substrate, the magnetic layer has the general formula %) (where Me = at least 1 of Ba, Pb, and Sr). More than species, M engineering = Ga, AI, Mn,
At least one kind of Cr, Mz=Be, Ta
, Ti, Zn. 8n, Ge, In, Bi, Y, T
b, Yb, Sm, V. Gd, Dy, Ho, Er, Eu,
Yb, Pr, Co. Mg, B, Mo, W, Os, Pt, Ag, Au, Pd. Ru, Rh, Re, Ir, 8b,
Represents at least one of Tm, Pm, and Th, m and n are the ionic valences of M and MU, H% K +
)' indicate the number of substituted atoms of M and M, respectively, and A
*X + )' is 5≦A≦6゜0 (x≦L
It is within the range of O+0<y≦0.5. 1. A magneto-optical recording medium comprising a metal oxide magnetic material represented by: 2. In a magneto-optical recording medium having a magnetic layer and a reflective layer on a heat-resistant substrate, the magnetic layer exhibits at least one type of the general formula %, and X+y is C. and the number of substituted atoms of M, n indicates the ion valence of M, x,
y is a metal oxide magnetic material represented by 0 (x≦0.8°0,2 (y (within the range of 1, o)), and the magnetic layer has an absolute refractive index of 1.7 or more. A magneto-optical recording medium characterized by being sandwiched between transparent high refractive index dielectric layers.