JPH0622171B2 - Magneto-optical recording medium - Google Patents

Description

TECHNICAL FIELD The present invention relates to a magneto-optical recording medium having a magnetic film made of a novel metal oxide magnetic material.

2. Description of the Related Art In recent years, a magneto-optical recording medium for performing magnetic recording with a semiconductor laser beam has been researched and developed for high density recording. Conventionally, most magnetic materials used in magneto-optical recording media are amorphous alloys of rare earth metals and transition metals. In order to manufacture a magneto-optical recording medium using such an amorphous alloy magnetic material, the magnetic material is generally provided on a substrate such as a glass plate,
For example, a magnetic film is formed by adhering a Tb-Fe alloy to a thickness of about 0.1 to 1 μm by a method such as vacuum deposition and sputtering. Recording and reproduction on the thus obtained magneto-optical recording medium are performed as follows. That is, the recording is performed by irradiating and heating the magnetic film with laser light modulated by a binary signal by utilizing the rapid change characteristic of the coercive force corresponding to the temperature change in the vicinity of the Curie temperature or the compensation temperature of the magnetic film to change the direction of magnetization. It is performed by reversing. In addition, reproduction is performed by reading by utilizing the difference in magneto-optical effect of the magnetic film thus recorded in reverse. Since the magneto-optical recording medium using the amorphous alloy magnetic material as described above has a high recording sensitivity, it has an advantage that it can be recorded at a high speed (at a frequency of 1 MHz) by a semiconductor laser light. In particular, since the rare earth metal component is susceptible to oxidative corrosion, there is a major drawback that the magneto-optical characteristics of the magnetic film deteriorate with time. In order to prevent this, SiO, S is formed on the amorphous magnetic film.
It is also known to provide a protective film such as iO ₂ (the forming method is vacuum evaporation, sputtering, etc. as in the case of the magnetic film), but O ₂ which remains in vacuum when the magnetic film or the protective film is formed , on the magnetic film is oxidized and corroded with time by O _2, H 2 _O or the like contained in the target of the adsorbed O _2, H 2 _O and the like and alloys magnetic surface of the substrate, the recording time of the light and heat Furthermore, this oxidative corrosion is accelerated. Further, the amorphous magnetic material has a drawback that it is easily crystallized by heat, which easily deteriorates the magnetic characteristics. As a reproducing method for further improving the reproducing output, the magnetic film is made as thick as possible, and a reflective film of Cu, Al, Pt, Ag, etc. is provided on the magnetic film, and after the laser light is irradiated and transmitted through the magnetic film, The reflection type Faraday method of reflecting and detecting the reflected light is advantageous in that a high S / N signal can be obtained, but since the conventional amorphous magnetic film lacks translucency, it is used for this method. It was impossible.

It is an object of the present invention to provide a magneto-optical recording medium which has a magnetic film made of a novel metallized magnetic material, has high recording sensitivity, and is excellent in oxidative corrosion resistance and translucency.

Structure The metal oxide magnetic material used in the magneto-optical recording medium of the present invention has the general formula CoM _x Fe _{2 -x} O ₄ (where M = Mn, Ni, Ti, Zn, Al, Sn, Cr, Cu, Mg, Rh). , V, Ga, In, Sb, S
at least one member of the group consisting of c, Bi, Y, Sm, Eu, Tb and Gd, 0.
4 ≦ x ≦ 1.4) and the magnetic film is made of the metallized magnetic material of the above general formula.

The magnetic substance or magnetic film used in the magneto-optical recording medium must have magneto-optical characteristics (appropriate Curie temperature, coercive force, etc.) that can be recorded and reproduced by semiconductor laser light, but particularly high recording sensitivity is obtained. Therefore, it is necessary that the Curie temperature Tc is low and that the coercive force Hc is appropriately high in order to stably maintain the recorded memory. Generally, the proper range of Tc and Hc is 100 for Tc.
For ~ 350 ° C, it is considered to be 300-6000 Oersted. This is because when the Tc is 100 ° C. or lower, the recorded memory becomes unstable due to the laser light during reproduction, which causes deterioration of the reproducing characteristics, and when the temperature is 350 ° C. or higher, recording by the semiconductor laser light is difficult. If it is less than 300 oersteds, the memory may become unstable and may disappear, and if it is more than 6000 oersteds, the laser output and the external magnetic field necessary for the magnetization reversal at the time of recording become large, which is not preferable.

On the other hand, as a magnetic valve material, a hexagonal crystal thread and a spinel thread metal oxide magnetic material have been studied. Among them, for spinel yarn, for example, Co spinel type iron oxide is known. The inventors of the present invention noted that this kind of magnetic substance is an oxide itself, so that there is no fear of oxidative deterioration and that it has translucency even when the film thickness is 10 μm. However, since the Curie temperature Tc of them is as high as 450 ° C. or higher, it is difficult to record with a semiconductor laser beam as described above, and they cannot be applied as they are as a material for a magneto-optical recording medium. Therefore, the present inventors have made various studies,
A part of the Fe atoms in the Co spinel type iron oxide is M
It was found that Tc is lowered by substituting with a metal atom represented by (hereinafter referred to as M metal) atom. Therefore, the present inventors have paid attention to such an effect of substituting M metal, and further, Tc and Hc required for a magnetic body or a magnetic film for a magneto-optical recording medium.
In consideration of the appropriate range of F of Co spinel type iron oxide
As a result of substituting a part of e with M metal at various ratios, it was found that the metal oxide magnetic material of the above general formula gave excellent characteristics as a magneto-optical recording medium, and the present invention was accomplished.

As described above, according to the present invention, since the Curie temperature is particularly high, a part of Fe atoms in the Co spinel type iron oxide, which has not been neglected as a material for a magneto-optical recording medium, is replaced with M metal atoms, so that a memory can be obtained. While maintaining a required moderately high coercive force, the Curie temperature is lowered to enable recording / reproducing with a semiconductor laser beam, and thus it can be applied as a material for a magneto-optical recording medium.

As can be seen from the above description, the metal oxide magnetic material of the present invention satisfies the appropriate Curie temperature range Tc and the appropriate coercive force range Hc required as a material for a magneto-optical recording medium. Due to these Tc and Hc characteristics, the metal oxide magnetic material or magnetic film of the present invention can be applied as a material for a magneto-optical recording medium for recording / reproducing with a semiconductor laser beam, and of course, because of its low Curie temperature, high recording sensitivity. Up,
It has features such as oxidation resistance and translucency.

In order to produce the metal oxide magnetic material of the present invention, 1 mol of Fe ₂ O _3, 0.5 mol of Co ₂ O _{3 and} 0.5 mol of M ₂ O ₃ are mixed and pulverized, and this is put into a mold having an appropriate shape and molded. After 1200 ~ 14
Sintering may be performed at a temperature of 00 ° C.

Specific examples of the metal oxide magnetic material of the present invention obtained as described above include CoCr _0.8 Fe _1.2 O ₄ and CoMn _1.0 Fe.
_1.0 O ₄ , CoCr _0.75 Fe _1.25 O ₄ , CoCr _1.2 Fe
_0.8 O ₄ , CoMn _0.75 Fe _1.25 O ₄ , CoAl _0.8 Fe
_1.2 O ₄ , CoAl _1.0 Fe _1.0 O ₄ , CoZn _0.75 Fe
_1.25 O ₄ , CoZn _1.0 Fe _1.0 O ₄ , CoTi _0.8 Fe
_1.2 O ₄ , CoSn _1.2 Fe _0.8 O ₄ , CoCu _1.0 Fe
_1.0 O ₄ , CoRh _0.5 Fe _0.5 O ₄ , CoCr _0.85 Fe
_1.15 O ₄ , CoCr _1.0 Fe _1.0 O ₄ , CoMn _0.4 Fe
_1.0 O ₄ , CoMn _0.9 Fe _1.1 O ₄ , CoCr _0.8 Bi _0.2 Fe
_1.0 O ₄ CoMn _0.6 Bi _0.2 Fe _1.2 O ₄ , CoAl _0.8 Bi
_0.1 Fe _1.1 O ₄ , CoCr _0.8 V _0.1 Fe _1.1 O ₄ , CoMn _0.7 Sn
_{0.1 Fe 1.2 O 4, CoMn 0.8} V 0.1 Bi 0.1 Fe 1.0 O 4 and the like.

In addition, in order to improve the magneto-optical characteristics by further increasing the Faraday rotation angle, the above metal oxide magnetic material has La,
Metals such as Yb and Dy can be added.

To make a magnetic film using the metal oxide magnetic material of the present invention,
Depending on the type of substrate, this magnetic material is generally used as a target on the substrate at a substrate temperature of 500 to 700 ° C and the film thickness is 0.1 to 1 by a method such as vacuum deposition, sputtering, or ion plating.
It may be attached to a thickness of about 0 μm. Thus, as shown in FIG. 5, a magneto-optical recording medium having the magnetic film 2 which is perpendicularly magnetized on the substrate 1 is obtained. In some cases, the magnetic film can be formed at a substrate temperature lower than 500 ° C. However, in this case, after the magnetic film is formed, it is necessary to perform heat treatment at 500 to 800 ° C. on this, while applying a magnetic field in some cases, for perpendicular magnetization. Here, the substrate material is generally a heat-resistant metal such as aluminum; quartz glass; GGG;
Sapphire; Lithium tantalate; Crystallized transparent glass; Pyrex glass; Single crystal silicon with or without surface oxidation treatment; Al ₂ O ₃ , Al ₂ O ₃ .Mg
O, MgO · LiF, Y ₂ O ₃ · LiF, BeO, Zr
Transparent ceramic materials such as O ₂ · Y ₂ O ₃ and ThO ₂ · CaO; inorganic materials such as inorganic silicon materials (for example, Tosgard manufactured by Toshiba Silicon Co., Sumiceram P manufactured by Sumitomo Chemical Co., Ltd.), acrylic resins, polycarbonate resins, polyester resins, etc. Organic materials can be used.

The magnetic film of the present invention can be applied not only to the single-layer type magneto-optical recording medium as shown in FIG. 1 but also to all conventionally known multi-layer type magneto-optical recording media. Examples of this type of multi-layer type include those having the configurations shown in FIGS. In the figure, 1'is a substrate with a guide track, 3 is a reflective film, 4 is a guide track layer, 5 is a protective film, 6 is a transparent adhesive layer, and 7 is a heat resistant layer.
Here, the substrate 1'with a guide track is made by processing the above-mentioned organic material by injection molding, extrusion molding, photoetching or the like. The guide track on the substrate guides the laser beam during recording and reproduction. The reflective film 3 is made of Cu, Al, Ag, Au, Pt, TeOx, Te.
It is formed by depositing C, SeAs, TeAs, TiN, TaN, CrN, cyanine dye, phthalocyanine dye, etc. on the target surface to a film thickness of about 500 to 10000Å by a method such as vacuum deposition, sputtering, and ion plating. The reflective film is provided for the purpose of reflecting the laser beam transmitted through the magnetic film and increasing the Faraday effect by transmitting the laser beam through the magnetic film again. Guide track layer 4
Is formed by applying an ultraviolet curable resin to the target surface and then irradiating ultraviolet rays to cure the resin while pressing a mold having a guide groove. The protective film 5 is an acrylic resin, a polyurethane resin, a polycarbonate resin, a polyether sulfone resin, a polyamide resin, an epoxy resin, TiN, Si ₃ N ₄ , TaN, SiO ₂ , SiO or the like, which is a coating method in the case of a resin, and other cases. Is formed by depositing a film having a thickness of about 0.1 to 10 μm on the target surface by a method such as vacuum deposition, sputtering, and ion plating. The protective film is provided for the purpose of protecting the reflective film 3. The transparent adhesive layer 6 is a heat-resistant layer 7 provided with the magnetic film 2 and the reflection film of the substrate 1 ′ having a guide track provided with the reflection film 3 (since this layer is made of the above-mentioned inorganic material, “heat-resistant layer provided with a magnetic film”). Is a single-layer type magneto-optical recording material) and is adhered with a resin such as epoxy resin, polyurethane or polyamide to a thickness of about 2 to 100 μm. That is, this transparent adhesive layer is simply the substrate 1 '.
It is a layer for joining the upper reflection film 3 and the magnetic film 2 of the single-layer type magneto-optical recording material. Since the heat-resistant layer 7 is made of the above-mentioned inorganic material and corresponds to the substrate 1, it is provided here for the purpose of improving the heat resistance of the magnetic film 2. Thickness is about 10 ~
About 500 μm is suitable.

Recording and reproduction on the above-described magneto-optical recording medium using the magnetic film of the present invention are performed by irradiating a laser beam modulated or deflected from the magnetic film or the substrate side as in the conventional case.

The metal oxide magnetic material or magnetic film of the present invention has suitable Tc and Hc as a material for a magneto-optical recording medium, and has high recording sensitivity, but has an oxidation resistance and corrosion resistance which are not present in conventional products. Since it has transparency, the magneto-optical characteristics do not deteriorate with time, and transmitted light can be used during reproduction, and therefore reproduction can be performed using a Faraday rotation angle with high reproduction output.

Examples of the present invention will be shown below.

Example 1~12 Fe ₂ O ₃ 1 mol of _Co 2 _{O 3} 0.5 moles of the _M 2 _{O 3} 0.5 mol well mixed and dispersed in a ball mill, the inner diameter 120mm this
Placed in a disc-shaped mold with a depth of 2 mm, pressure 300 kg / cm ² , temperature 12
Sintering was carried out at 00 ° C. for 2 hours to obtain the disc-shaped target shown. Next, using these targets, Ar gas 90% ~
RF sputtering was performed on a quartz substrate under the conditions of a substrate temperature of 200 ° C., a gas pressure of 3 Pascal, and a discharge power of 50 W in a mixed gas of O ₂ 10% to form a magnetic film having a thickness of 5000 Å. The results of measuring the Curie temperature Tc and the coercive force Hc of these magnetic films are shown in the table below.

Next, each of the magneto-optical recording media obtained as described above is
Applying a magnetic field of 10K oersted from the outside while heating to ℃, magnetize in the perpendicular direction, and apply a magnetic field of 500 oersted opposite to the direction of this magnetization, and output 2
When recording was performed by irradiating 0 mW of semiconductor laser light with a pulse of intensity 10 mW and frequency 1 MHz on the surface of the recording medium for magnetic reversal and recording, a recording pit having a pit diameter of about 1.5 μm was formed in each case.

[Brief description of drawings]

1 to 4 are block diagrams of examples of the magneto-optical recording medium of the present invention. 1 ... Substrate 1 '... Substrate with guide track 2 ... Magnetic film, 3 ... Reflective film 4 ... Guide track layer, 5 ... Protective film 6 ... Transparent adhesive layer, 7 ... Heat-resistant layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Motoharu Tanaka 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Inventor Atsuyuki Watada 1-3-6 Nakamagome, Ota-ku, Tokyo Stocks Within Ricoh Company (72) Inventor Fumiya Omi 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Company Ltd. (56) Reference JP-A-51-119999 (JP, A) JP-A-55-55503 ( JP, A) JP 58-145625 (JP, A) JP 41-547 (JP, B1)

Claims (1)

[Claims] 1. A substrate of the general formula CoM _x Fe _2-x O ₄ (where M is Mn, Ni, Ti, Zn, Al, Sn, Cr, Cu, Mg, R).
h, V, Ga, In, Sb, Sc, Bi, Y, Sm, Eu, Tb, and at least one of the group consisting of Gd, 0.4 ≦ x ≦ 1.4) A magneto-optical recording medium having a film.