JPH01179240A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To obtain a recording medium having large coercive force and excellent optical characteristics by using an amorphous alloy consisting of specific components to form the recording film of the medium constituted by laminating a 1st protective film, magneto-optical recording film and 2nd protective film on a transparent substrate. CONSTITUTION:The 1st protective film 2, the magneto-optical recording film 3 and the 2nd protective film 4 are laminated on the transparent substrate 1 to form the magneto-optical recording medium. The film 3 is the thin amorphous alloy film which is expressed by the formula (RE is at least one kind of the elements selected from the group consisting of Nd, Sm, Pr, Ce, Eu, Gd, Tb, Dy, and Ho; TM is Fe and/or Co, and 0.2<x<0.7, 0.10<y<0.30) and has the axis of easy magnetization in the direction perpendicular to the film plane. The recording medium formed in such a manner has the large coercive force, large angle of Kerr rotation and angle of Faraday rotation, excellent oxidation resistance and the excellent characteristics that the coercive force and the angle of Kerr rotation are not deteriorated with age.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magneto-optical recording medium having excellent oxidation resistance, and more particularly, to a magneto-optical recording medium having an axis of easy magnetization perpendicular to the film surface, The present invention relates to a magneto-optical recording medium having excellent oxidation resistance.

11 -'4: I long'' shell, frab Cζ÷0 transition metals such as iron, cobalt, and terbium (''r
'b), an amorphous thin film made of an alloy with a rare earth element such as gadolinium (Gd) has an axis of easy magnetization in the direction perpendicular to the film surface, and the film surface is fully magnetized in one direction. It is known that it is possible to form small reversed magnetic domains that are oriented in the opposite direction.

By making the presence or absence of this inverted magnetic domain correspond to "11" and "0", it becomes possible to record a digital signal on the amorphous thin film as described above.

For example, Japanese Patent Publication No. 57-20691 discloses that an amorphous thin film composed of a transition metal and a rare earth element used as such a magneto-optical recording medium has a concentration of 15 to 30 at.
An amorphous thin film of a Tb-Fe based alloy containing b is disclosed. Also, an alloy amorphous thin film made by adding a third metal to Tb-Fe is also used as a magneto-optical recording medium. Further, magneto-optical recording media such as 'rb-co type and 'r''b-Fe-Co type are also known.

Magneto-optical recording media made of these alloy amorphous thin films have excellent recording and reproducing properties, but during use, these amorphous thin films undergo oxidation and their properties change over time. There were major practical problems.

The mechanism of oxidative deterioration of magneto-optical recording media made of alloyed amorphous thin films containing transition metals and rare earth elements is as follows.
For example, Journal of the Japanese Society of Applied Magnetics, Vol. 9, No. 2, No. 93.
It has been discussed on pages 96 to 96, and it has been reported that there are three types as shown below.

b) Pitting Pitting corrosion refers to the formation of pinholes in an amorphous thin film of an alloy. This corrosion mainly progresses in a high-temperature atmosphere, for example in Tb-Fe system, Tl)-Co system, etc. progresses significantly.

) A surface oxidation layer is formed on the amorphous thin film of the surface oxidation alloy, and the Kerr rotation angle θ
k changes over time, and the Kerr rotation angle θk eventually decreases.

c) Selective oxidation of rare earth metal The rare earth metal in the amorphous thin film is selectively oxidized, and the coercive force I(C) changes greatly over time.

In order to prevent the oxidative deterioration of alloy amorphous thin films as described above, various methods have been tried in the past.

For example, alloy amorphous thin films are made of Si3N4, Si○, S
A method of creating a three-layer structure sandwiched between oxidation-preventing protective films such as iO2 and AIN is being considered. However, even if this protective film is formed, there is a problem in that it is not always possible to sufficiently prevent oxidative deterioration of the alloy amorphous thin film.

That is, if a pinhole or the like exists in the above-mentioned oxidation-preventing protective film, it is impossible to prevent the oxidative deterioration of the alloy amorphous thin film from progressing through the pinhole.

In addition, in order to improve the oxidation resistance of the thin film, a third layer is added to the amorphous thin film of alloys such as Tb-Fe and Tb-co.
Various methods of adding metals have been attempted.

For example, in the journal of the Japanese Society of Applied Magnetics mentioned above, Tb-Fe
Or Tb-Co, Co, Ni, Pt, AI, Cr
'rb-Fc system or 'rb-c
Attempts have been made to improve the oxidation resistance of o-based alloy amorphous thin films. And C to Tb-Fe or Tb-Co
When small amounts of O, Ni, and Pt are added, it is effective in preventing surface oxidation and pitting corrosion, but it is not effective in preventing selective oxidation of Tb, a rare earth metal, in the amorphous thin film of this alloy. It is reported that there is no. This means that when a small amount of Co, Ni, or Pt is added to Tb-Fc or r'b-Co, Tb is selectively oxidized in the resulting amorphous alloy thin film, and the coercive force Hc decreases over time. This means that there will be a major change. Therefore Tb-F
e or a small amount of Co up to 3.5 at% in Tb-Co
, Ni, and Pt do not sufficiently improve the oxidation resistance of the resulting alloy amorphous thin film.

Also, the 9th Academic Lecture Summary of the Japanese Society of Applied Magnetics (1985)
On page 209 of 2011 JI), Tb-Fe or T
b-Fe-Co, Pt, AI, Cr, Ti 10
Alloy amorphous thin films are taught with additions of up to atomic percent. However, 'T'b-Fc or T b-F
c-Co in an amount of up to 10 atom % of Pt, AI, Cr,
Even if Ti is added, surface oxidation and pitting corrosion can be prevented quite effectively, but the oxidation prevention property against selective oxidation of Tb in the resulting amorphous alloy thin film is not sufficient, and the coercive force also decreases over time. There still remained the problem that IC changed significantly and eventually coercive force HC decreased significantly.

Furthermore, in Japanese Patent Application Laid-open No. 58-7806, pt.
A magnetic thin film material comprising a polycrystalline thin film having a composition of Co and containing 10 to 30 at. % of pt is disclosed.

However, since this polycrystalline thin film with a composition of ptco is polycrystalline, heat treatment such as annealing is required after film formation, and the grain boundaries between crystals may generate noise signals. This polycrystalline thin film had a problem in that it had a high Curie point.

However, the present invention aims to solve the above problems, and has excellent magneto-optical properties such as a large coercive force and a large Kerr rotation angle and a large Faraday rotation angle. Moreover, it is an object of the present invention to provide a magneto-optical recording medium which has excellent oxidation resistance and whose coercive force or Kerr rotation angle does not change over time.

Overview of the present invention The magneto-optical recording medium according to the present invention includes a first protective film, a magneto-optical recording film, and a second protective film, which are sequentially laminated in this order on a transparent substrate. The magneto-optical recording film is (Pt and/or Pd).

[RE x '1' M 1-x] 1-.

(In the formula, RE is Nd, Sm, Pr, Ce, EIJ, Gd
At least one element selected from the group consisting of -Tb, DV and )-10, TM is Fe and/or Co, and 0.2<x<0.7.0.10<y<
It is characterized by being an amorphous alloy thin film having an axis of easy magnetization perpendicular to the film surface expressed by 0.30).

The above-mentioned magneto-optical recording medium according to the present invention has excellent magneto-optical properties such as a large coercive force and a large Kerr rotation angle and a large Faraday rotation angle, and has excellent oxidation resistance.
It has an excellent property that the coercive force or Kerr rotation angle does not change over time.

EMBODIMENT OF THE INVENTION Below, the magneto-optical recording medium according to the present invention will be specifically explained.

As shown in FIG. 1, the magneto-optical recording medium according to the present invention has a first protective film 2, a magneto-optical recording film 3, and a second protective film 4 laminated in this order on a transparent substrate 1. The magneto-optical recording film is composed of (Pt and/or Pd''), [REx'1'M1-x] 1-y (wherein, RE is Nd, Sm, PI', Ce, Ell, G
at least one element selected from the group consisting of d, Tb, DV, and )-IO, TM is Fe and/or Co, and 0.2<x<0.7.0.10<
It is an amorphous alloy thin film having an axis of easy magnetization perpendicular to the film surface, which is expressed by y<0.30.

As the transparent substrate 1, a wide range of materials that have been conventionally used as transparent substrates can be used, but specifically, glass, polymethyl methacrylate-1, polycarbonate,
Polymer alloy of polycarbonate and polystyrene,
Amorphous polyolefins such as those shown in U.S. Pat. A lacyclododecene copolymer or the like can be used.

The thickness of this transparent substrate 1 is about 0.5 to 2.5 mm, preferably about 1.0 to 1.5 mm.

The first protective film 2 provided on the transparent substrate 1 as described above is made of Si 3 N,1, AI N, At Si
Nitrides such as N, BH, S! 02°Tb-3i O2,
Mt+-8i02, AI2o3,5i02-
AI 203 , M(]-8l 02- AI 203
, Tb-3i O-At O, Ba-3i O2, B
a-AI 203, Ba-silica alumina, T e-A
I 203, M(1-Al2O2, TiO2, SiO
, Ti01ZnO, ZrO2, , Ta205, Nb2O
5. Oxides such as CeO2, SnO2, TeO2, indium-tin oxide, sulfides such as ZnS, CdS, ZnSe, SiC, Si, etc. are used.

Further, as the first protective film 2, a plasma polymerized film of CH4, C82, Teflon, etc., or an organic coat film such as a UV-curable organic coat film can also be used.

This first protection film 1pA2 functions as a protective film that protects the magneto-optical recording film from oxidation and the like, and also functions as an enhancement film.

The thickness of the first protective film 2 is approximately 50 to 5,000, preferably 100 to 2,000.

Such a magneto-optical arrangement 5 provided on the first protection rise! The film has a composition expressed by the above formula, and this magneto-optical recording film will be specifically explained below.

b) In the above formula, TM is Fe or Co or both. In such a TM, when the magneto-optical recording film is expressed by the above formula [I], 1-X (however, 0.2<x
<0.7, preferably 0.25<x<0.5, more preferably 0.3<xo,5).

] As M, it is preferable that both Fe and Co exist, and especially for this TM, Fe is 100~
Preferably Co is present in an amount of 35 atom % and Co in an amount of 0 to 65 atom %.

Note that the TM may contain 5 at % or less, preferably 3 at % or less of Ni.

(ii) Pt and/or Pd is added to the magneto-optical recording film at 1
It is present in an amount of 0 to 15 atomic %.

If the content of Pt and/or Pd is below the above range, the oxidation resistance of the resulting magneto-optical recording film will not be sufficiently improved, and even if a protective film is provided, pinholes may occur in the protective film. If the magneto-optical recording film is oxidized and the coercive force Hc changes over time, or the Kerr rotation angle θk
This is not desirable because it may cause a decrease in

pt or Pd may each be used alone,
They may also be used in combination.

(iii>The magneto-optical recording film according to the present invention has the above-mentioned (i>
In addition to (ii) and (ii), it contains at least one rare earth element (RE).

This RE is Nd, Sm, Pr, Ce, Etl
, Gd 2 , Tb 2 , DV and Ho. Preferably RE 6
0 atomic % or more is Tb, the remainder is DV, Nd, Gd
, Ce, Eu, Pr, Ho or sm.

More preferably, 80 atomic % or more of RE is Tb, particularly preferably 90 atomic % or more, and the remainder is Dy, Nd.
, Gd, Ce, Eu, Pr, Ho or sm.

”-, when the amorphous alloy thin film is represented by the above formula [i], the rare earth element RE is 0.2<x0.7, preferably 0.25<x<0.5, and more preferably is 0.3<
It is present in an amount such that x<0.5.

In the present invention, the thickness of the magneto-optical recording film made of the amorphous alloy thin film having the axis of easy magnetization perpendicular to the film surface is 2.
00 to 2,000 people, preferably 200 to 1,000 people.

A second protection J provided on the magneto-optical recording film 3 as described above.
l! 4, Si 3 H4, AI N, AI
Nitride such as Si N, BN, s r o2, "rb-
8i O2, M(]-5i O2, Te-Al 203
, Mg-Al203, Tb-8i02-At
203, Ma-8i O2-Al 203, Ba-8
i02, Ba-Al203, Ba-3to2-
AI203, TlO2, SiO, TiO, Z
nO1Zr○2, 'l'a 2 0s, Nb 2
05, Ce 02 , Sri O2, TeO2,
Oxides such as indium-tin oxide, Zn s, Cd
Sulfides such as S, zn sc , s*c, Si, etc. are used.

In addition, as the second protective film 11, a film of I), a PdJ model, a T
i 771;%, Cr I model, zr) model\Nr
A metal film such as fIA, Ni-Cr) or the like can also be used.

Further, as the second protective film, an organic coat film such as a plasma polymerized film of CH4, CS2, Teflon, etc. or a UV curable organic coat film can also be used.

This second protection IJI! 4 functions as a protective film that protects the magneto-optical recording film from oxidation and the like, and may also function as a reflective film.

The film thickness of such second protection M4 is 5 in the case of an inorganic material.
It is about 0 to 5,000 people, preferably about 100 to 2,000 people, and in the case of organic materials, it is about 100 to 100 μm, preferably about 300 to 500 μm.

The magneto-optical recording medium according to the present invention having the above-described structure has an axis of easy magnetization perpendicular to the film surface, and often exhibits a rectangular loop with good Kerr hysteresis.

In this specification, a square loop with good Kerr hysteresis means the saturated Kerr rotation angle (in θ), which is the Kerr rotation angle at the maximum external magnetic field, and the residual Kerr rotation, which is the Kerr rotation angle at zero external magnetic field. The ratio of the angle (to θ, >
This means that 1 in 2/θ is 0.8 or more.

Furthermore, the magneto-optical recording medium according to the present invention as described above has excellent oxidation resistance, and as shown in FIG.
'b3(>Fe49cOa), a first protective film Si 3 N4, a second protective film
For example, a magneto-optical recording medium made of AS13N4 is 8
Even if it is kept in an environment of 5° C. and 85% relative humidity for more than 240 hours, its coercive force hardly changes. On the other hand, Tbz5Co75 or T b 2 which does not contain Pt
When an amorphous alloy thin film having a composition of 5 F Q 66Co9 is maintained in an environment of 85° C. and 85% relative humidity,
The coercive force changes greatly over time. Furthermore, when this environmental test was continued for 1000 hours, the coercive force of the system containing pt and/or Pd remained almost unchanged, whereas the coercive force of the system containing no Pt and/or Pd could hardly be measured. It will decrease to a certain extent.

In addition, from the experimental examples described later, pt and /mana are Pd
In the magneto-optical recording medium according to the present invention, which includes an amorphous alloy thin film containing It can be seen from observation of the film surface using a microscope that pitting corrosion is also suppressed.

In the present invention, various elements other than those mentioned above may be added to the magneto-optical recording film to improve the Curie temperature, compensation temperature, HC and θ, or to reduce costs. These elements can be substituted, for example, at a rate of less than 50 atomic % with respect to the rare earth element.

Examples of other elements that can be used in combination include the following compounds.

(I) 3d transition elements other than Fe and Co, specifically Sc, Ti, V, Cr, Mti, Ni, C
u, Zn are used.

Among these, T;, Ni, cu, zn, etc. are preferably used.

(n) 4d transition elements other than Pd, specifically Y, Zr, Nb, Mo, Tc, Ru
, Rh, Ag, and Cd are used.

Among these, Zr and Nb are preferably used.

([1) 5d transition elements other than Pt Specifically, Hf, Ta, W, Re, Os, Ir,
Au,)-1g is used.

Among these, Ta is preferably used. .

(IV) Group IIIB element Specifically, B, AI, Ga, In, and TI are used.

Among these, B, AI, and Ga are preferably used.

(V) IVB group element Specifically, C, Si, Ge, Sn, and Pb are used.

Among these, si, ae, sn, and pb are preferably used.

(Vl) VB group element Specifically, N, I), AS, Sb, and Bi are used.

Among these, sb is preferably used.

(VII) VII group 3 elements Specifically, S, Sc, Te, and Po are used.

Among these, Te is preferably used.

Next, a method for manufacturing a magneto-optical recording medium according to the present invention will be explained.

First, a first protective film is formed on a transparent substrate.

To form the first protective film on the transparent substrate, a conventionally known method such as a vacuum evaporation method, a sputtering method, an electron beam evaporation method, a spin code method, etc. can be employed.

Next, in order to form a magneto-optical recording film on the first protective ridge provided on the transparent substrate, the temperature of the substrate is kept at around room temperature, and chips made of each element constituting the magneto-optical recording film according to the present invention are deposited. Using a composite target or an alloy target having a composition of a predetermined ratio arranged at a predetermined ratio, conventionally known film forming conditions such as a sputtering method or an electron beam evaporation method are employed to deposit this substrate (the substrate may be fixed). , or may be rotating on its own axis), a magneto-optical recording film of a predetermined composition may be deposited thereon.

As described above, the magneto-optical recording film according to the present invention can be formed at room temperature, and there is no need to perform heat treatment such as annealing treatment after film formation in order to have an axis of easy magnetization perpendicular to the film surface.

If necessary, the magneto-optical distribution may be applied to the substrate while heating the substrate temperature to 50 to 600°C or cooling it to -50°C. A film can also be formed.

Further, during sputtering, the substrate can be biased to a negative potential. In this way, ions of an inert gas such as argon accelerated by an electric field can be
~ Not only materials but also perpendicularly magnetized films, which are currently being formed, can be attacked, and a perpendicularly magnetized film with excellent properties may be obtained.

Next, a second protective film is formed on the magneto-optical recording layer formed as described above, and at this time, conventionally known methods such as vacuum evaporation, sputtering, or electron beam evaporation are used. can do.

The magneto-optical recording medium according to the present invention is a perpendicularly magnetized film having an axis of easy magnetization perpendicular to the film surface, and in many cases, the Kerr hysteresis loop has a square shape, so that it can be easily magnetized in the absence of an external magnetic field. Since θk is almost the same as the saturation θ at the maximum external magnetic field and the coercive force HC is large, it is suitable as a magneto-optical recording film. Also, a good θk means that θ”
Therefore, it can be used in either the Kerr effect type or Faraday effect type.

The magneto-optical recording medium according to the present invention is not limited to the above-mentioned horizontal path, but may be laminated with an underlayer, an anti-oxidation film, or a high-permeability soft magnetic film, etc., as necessary. It is also possible to use it by laminating veneers together.

The magneto-optical recording medium according to the present invention comprises a first protective film, a magneto-optical recording film and a second protective film, which are sequentially laminated in this order on a transparent substrate, The magnetic recording film is (Pt and/or Pd)V [RExTMl-x] 1-y (where I' (E is Nd, Sm, Pr, Ce,
TM is at least one element selected from the group consisting of Eu, Gd, Tb, D)f, and Ho, and TM is Fc
and/or Co, and 0.2<x<0.7.0.
Since it is an amorphous alloy '4Jli with an axis of easy magnetization perpendicular to the film surface expressed as 10<y<0.30,
It has excellent magneto-optical properties such as a large coercive force and a large Kerr rotation angle and Faraday rotation angle, and has excellent oxidation resistance. It has an excellent characteristic of not changing or changing the Kerr rotation angle.

Furthermore, when forming the magneto-optical recording film according to the present invention on a substrate, it is possible to form the film at room temperature, and there is no need for heat treatment after film formation.

EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples.

Part 21 1-8.　　　　　1～5 A first protective film, a magneto-optical recording film, on a glass substrate.

A second protective film was sequentially formed to a predetermined thickness by sputtering.

When a dielectric film of nitride or oxide was selected as the protective film, each sintered target was subjected to RF magnetron sputtering. On the other hand, when a metal film was selected as the protective film, it was formed by DC magnetron sputtering.

As for the magneto-optical recording film, the target is
p on Fe target or on Fe, Co target
Using a composite target in which chips of T and/or Pd, light rare earth metals, and heavy rare earth metals are arranged at a predetermined ratio, the substrate is placed on a glass substrate at 20 to 30°C by water cooling.
An amorphous alloy thin film having a composition shown in Table 1 was formed by DC magnetron sputtering while controlling the temperature to be around room temperature. The film forming conditions were Ar pressure 5 rn
TOrr, Ar flow t3sec, vacuum attainment 5x
10-” Torr or less.

The crystalline state of the obtained Alloy 3 film was measured by wide-angle X-ray diffraction, and the composition was determined by ICP spectroscopic analysis.

In addition, the Kerr rotation angle is the residual Kerr rotation angle measured from the glass substrate side with zero external magnetic field using the oblique incidence method (λ = 633 nm).
It was measured with Specific measurement methods and equipment for the oblique incidence method are available in "Measurement Techniques for Magnetic Materials" (December 1985) supervised by Aibe Yamakawa.
Published by Triceps Co., Ltd. on March 25th, pp. 261-26
It is described on page 3.

The X value and coercive force (f-1) of the obtained amorphous alloy thin film
co) are shown in Table 1.

Furthermore, in order to confirm the oxidation resistance of the amorphous alloy thin film of the present invention, the conditions under which the film was formed on the glass substrate were maintained at 85°C.
An environmental test was conducted in which the oven was left in an oven under high temperature and high humidity conditions of 85% R and H, and the Kerr rotation angle (
θk) and coercive force (Hc) were measured and compared with the respective initial values θko and Hco before the test. These results are shown in Table 1.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a magneto-optical recording medium according to the present invention,
Figure 2 shows changes in the coercive force of the magneto-optical recording medium according to the present invention and 'rb 25C075 and T b2 according to comparative examples.
FIG. 5 is a diagram showing changes in coercive force of 5 Fe 66C09. 1... Transparent substrate 2... First protective film 3...
Magneto-optical recording film 4...Second protective film Agent Patent attorney Shun Suzuki Changes to engravings of some drawings Figure 2 Time () 1r, ) Procedure amendment date April 26, 1988 Japan Patent Office Commissioner Kunio Ogawa1, Indication of the case 1988 Patent Application No. 335.5532, Name of the invention Magneto-optical recording medium3, Relationship with the person making the amendment Patent applicant name Mitsui Petrochemical Industry Co., Ltd. 4, Agent (Postal code 141) N.M. Building 4, Higashigotanda-chome-25-4, Tokyo Parts Ward
Floor [Telephone Tokyo (444) 3151] March 2, 1988 (shipped: March 29, 1988)
6. Subject of amendment 7. Contents of amendment (1) Submit a power of attorney as shown in the attached sheet. (2) Submit an engraving of Figure 2 of the drawing as attached (no changes to the content).

Claims (1)

[Claims] 1) A first protective film, a magneto-optical recording film, and a second protective film are sequentially laminated in this order on a transparent substrate, and the magneto-optical recording film is made of (Pt and/or Pd)_y [RE_xTM_1_-_x]_1_-_y (where R
E is Nd, Sm, Pr, Ce, Eu, Gd, Tb, Dy
and Ho, TM is Fe and/or Co, and 0.
2<x<0.7, 0.10<y<0.30. 2) The magneto-optical recording medium according to claim 1, wherein 0.25<x<0.5. 3) At least 60 atomic % or more of RE is Tb, and the remainder is Dy, Sm, Pr, Ce, Eu, Gd, or Ho
A magneto-optical recording medium according to claim 1.