JPS62175949A - Photomagnetic recording medium protected by compound oxide - Google Patents

Abstract

PURPOSE:To obtain a photomagnetic recording medium having improved durability by coating, directly or via other layer, at least one face of a magnetic recording layer consisting of a vertically magnetized film with a protective film essentially consisting of a compound oxide composed of a specific ratio of a group III metallic oxide and group IV metallic oxide. CONSTITUTION:At least one face of the magnetic recording layer consisting of the vertically magnetized film is coated directly or via the other layer with the protective film essentially consisting of the compound oxide composed of 20-85mol% group III metallic oxide and 80-15mol% group IV metallic oxide. for example, Al2O3, In2O3, Y2O3, La2O3, etc. are used as the group III metallic oxide to constitute the protective film and, for example, SiO2, TiO2, ZrO2, HfO2, SnO2, etc. are used for the group IV metallic oxide. Both oxides constitute the protective film preferably in the mixed state at a molecular level. The protective film is not always limited to the case in which said film is constituted of only the above-mentioned two kinds of the oxides and for example, a small amt. of a group IIa metallic oxide, for example, MgO, CaO and BaO may be incorporated therein. The film thickness of the protective film is generally enough with 100-10000Angstrom .

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a magneto-optical recording medium with excellent durability.

(Prior Art) In recent years, the information society has progressed at a remarkable pace, and the need for large-capacity recording media and recording/playback methods is rapidly increasing. %4 discs etc. have been put into practical use. However, the recording media that have been put into practical use have the disadvantage that they cannot be rewritable, and rewritable recording media and recording/playback methods are desired. As one example, a magneto-optical recording and reproducing method has been proposed, and prototypes have also been announced.

The magneto-optical recording medium used in this magneto-optical recording and reproducing system is basically a plastic substrate or a glass substrate with an amorphous perpendicular magnetization film formed thereon, and the magnetic material is, for example, GdTbFe, TbFeCo, etc. .

Rare earths such as GdCo, TbFe, GdDyFe
Transition metal multi-element alloys are used.

[Problem that the invention seeks to solve]

In order to investigate the durability of such magneto-optical recording media, the present inventor prepared samples and conducted accelerated deterioration tests in a high-temperature atmosphere, and found that the coercive force and magneto-optical properties deteriorated in a relatively short period of time. I found out that there is a problem with this.

Therefore, an object of the present invention is to provide a magneto-optical recording medium with improved durability.

[Means for solving problems]

As a result of intensive research, the present inventor has determined that at least one of the front and back surfaces of the magnetic recording layer (perpendicularly magnetized film) contains 20 to 85 mol % of Group (I) metal oxide and 80 to 1 mol % of Group (II) metal oxide.
A protective film mainly composed of a composite oxide consisting of 5 mol%.
It has been discovered that durability can be improved by coating directly or through another layer, and the present invention has been completed.

Accordingly, in the present invention, at least one surface of the magnetic recording layer consisting of a perpendicularly magnetized film is coated with 2° to 85 mol% of Group M metal oxide.
A magneto-optical recording medium is provided, which is coated directly or via another layer with a protective film mainly composed of a composite oxide consisting of 80 to 15 mol % of a Group (1) metal oxide.

According to the experiments conducted by the present inventor, it was strangely possible to reduce the content of the group (III) metal oxide to 20 mol in a protective film made of a composite oxide of a group (III) metal oxide and a group (III) metal oxide. Even if it is lower than 85 mol %, or conversely higher than 85 mol %, the durability of the medium is poor.

As the Group Ⅰ metal oxide constituting the protective film, for example, A
l z 02 , I nzos + Y! 03
, Lag's, etc. are used, and examples of group Ⅰ metal oxides include SiOx + TtOt + Zr
Ot+HfOx.

It is preferable that the protective film is formed by mixing SnO, etc. at the molecular level. Therefore, as a method for forming the protective film, for example, sputtering using the composite oxide as a target, sputtering using the composite oxide as a target, Reactive sputtering targeting metal alloys that make up oxides,
Binary (responsive or non-responsive) using two types of targets
Vacuum thin film formation techniques such as sputtering, binary ion blating, and binary vacuum deposition are used.

The protective film of the present invention is not limited to being composed only of the above two types of oxides, and may also contain, for example, a small amount of Group M metal oxide 2 or the like.

The thickness of such a protective film is 100 to 10.
000 people is enough.

The protective film of the present invention may be in direct contact with the magnetic recording layer, or there may be another layer □ - for example, another protective film or another functional film such as a Kerr effect increasing film □ between the magnetic recording layer and the magnetic recording layer. As such a Kerr effect increasing film which may intervene, for example, a film having a high refractive index having a thickness corresponding to a quarter wavelength or around it is used.

The magnetic recording layer is generally formed on a substrate, and the substrate may be, for example, glass, plastic, ceramic,
Aluminum or the like is used, but a thin molding layer on which uneven tracks are formed, a dielectric layer, a reflective layer, an interference film, or other protective film may be formed in advance on the substrate. Note that the present invention exhibits remarkable effects when a plastic substrate is used.

Next, before forming the magnetic recording layer, a "protective film mainly composed of a composite oxide", which is a feature of the present invention, is formed for the purpose of protecting the lower surface.

Then, directly or after forming another layer (for example, a Kerr effect increasing film) on the protective film, a magnetic recording layer (perpendicular magnetization film) is formed according to a conventional method. As the perpendicular magnetization film, for example, TbF
e, GdFe, DyFe, GdCo, 1Ioc
o.

GdTbPe, GdDyFe, TbDyFe,
GdPeCo, TbFeCo, GdDyF
Rare earth-transition metal amorphous alloys such as eCo5 GdTbFeCo are primarily used.

A protective film of the present invention is optionally provided on the perpendicular magnetization film. In the present invention, the protective film may be provided on at least one of the front surface or the back surface of the magnetic recording layer, but it is preferable to provide it on both. .

And generally, another protective film array is applied directly on top of the protective film of the present invention, such as S i O+ A Its O3+ Z r
Ox + ZnS, AIN, 5isNa, etc. may also be provided.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

[Example 1] After evacuating the vacuum chamber to 5 x 10-7 Torr,
to 5×10-'Torr. φ5 inch At! Using a Gos Sing mixed sintered target, the film formation rate was performed using the magnetron sputtering method on a glass substrate with a radiation-curable resin layer formed by the photopolymer method using an RF power of 700 W:
Approximately 50 people/win, film thickness: 1000 people Al, O,・
5iOz composite oxide CAI! zOs: Sich
-60: 40 mol%) was formed.

This film exhibits a refractive index of approximately 1.5 at a wavelength of 830 nu.

Next, a φ5 inch TbFe alloy target (Tb =
19 atomic%) at RF power of 400 W and film formation rate: 14
At 0 person/+sin, film thickness: 1000 people TbFc
A film (magnetic recording layer) was formed.

Furthermore, the same film thickness: 1000 people A1203-
S i O, complex oxide (A j! z Os
: S1Ox=60:40 mol%) was formed.

These three-layer films were all formed in the same vacuum.

Finally, glass plates were bonded together using a radiation-curable adhesive to produce a magneto-optical recording medium of the present invention.

The magneto-optical properties of the obtained magneto-optical recording medium have a reflectance R=44% at a wavelength of 830 n+w when measured from the substrate side.
, Kerr rotation angle θ = 0.29°, coercive force H1 = 5KO,
Met.

[Example 2] In the same manner as in Example 1, both the front and back surfaces of the magnetic recording layer were coated with A 1
Composite oxide of z Ox ・S i Oz (Aj+gO
A magneto-optical recording medium was manufactured with a protective film formed of (i:5iOx-40:60 mol%).

[Example 3] Both the front and back surfaces of the magnetic recording layer were coated with A 11 in the same manner as in Example 1.
03 ・S i Ox composite oxide (AI120°:
A magneto-optical recording medium on which a protective film was formed was manufactured.

[Comparative Example 1] A magneto-optical recording medium was produced in the same manner as in Example 1, except that instead of the protective film made of the composite oxide of ANzO*.Sin, a film of simple Sin was used.

However, the 5-inch film was created under the conditions of RF PA'7-IKW, film-forming rate: 120 people/win, and the film thickness was approximately 1000 people/win.

The magneto-optical properties of the obtained magneto-optical recording medium were R = 46% when irradiated with light with a wavelength of 830 ns+ from the substrate side.
, θx-0.275, Hc=5KO.

[Comparative Example 2] A j! A magneto-optical recording medium was manufactured in the same manner as in Example 1, except that an A 1 t Oy film was simply used instead of the protective film made of a complex oxide of zO3.Sin.

<Accelerated Deterioration Test 1> The magneto-optical recording media manufactured in Examples 1 to 3 and Comparative Examples 1 to 2 were placed in an atmosphere with a temperature of 60°C and a humidity of 90%, and the coercive force He(t) of the perpendicularly magnetized film was measured over time. quotient α = Hc (
Changes in coercive force were investigated using t)/Hc(0). Furthermore, the quotient α
A change in indicates that oxidation of the perpendicularly magnetized film has progressed, indicating that the magneto-optical properties have deteriorated.

The results are shown in Table 1. Also, Comparative Example 1.

No longer showed vertical anisotropy after 50 days.

Table 1 (Oral changes in Hc(t)/He(0)) [Example 4] One circumferential protrusion with a height of 1400 people and a width of 0.4 μ was prepared in advance.
．． A large number of nickel stampers were prepared concentrically with a pitch of 6μ.

In addition, a disk-shaped glass support (1b) with a thickness t=1.2 mm and a radius r=loo was prepared.

On top of the stamper, a U-curing resin was applied, and a glass support (lb) was placed thereon. The resin is cured by irradiating ultraviolet rays through the support (1b) to form a molded body N(la
) was molded. The molded body ji (la) has a depth of 1400 mm.
A large number of circumferential grooves each having a width of 0.4μ are provided concentrically at a pitch of 1.6μ.

A plastic substrate (11) was obtained by peeling the molded body layer (1a) together with the support (lb) from the stamper.

Next, a φ5 inch Alt! 0
3.Sin mixed sintering target and substrate (1)
cent. After evacuating the inside of the device to 3×10-'Torr, Ar gas was introduced to 5×10-''Torr.
Make it rr. Perform sputtering with RF power IKW. In this way, the film formation rate on the molded body N(Ia): about 5
At 0 people/min, film thickness: 1000 people Alz Oz
・S ion composite oxide (AN, 03: S i O
protection 11 (2
1 was formed. This film exhibits a refractive index of approximately 1°54 at a wavelength of 830 nm. Next, using a φ5 inch Gdz+FealcOxz alloy target at the same gas pressure,
A C, dFaco film (3a) with a film thickness of 500 layers was formed at an RF power of IKW and a film formation rate of 170 layers/win. Continued, Tb. Fe,. A TbFe film (3b) with a thickness of 500 yen was similarly formed using an alloy target. GdFeC
.

Both the film (3a) and the TbFe film (3b) have perpendicular magnetization and constitute the perpendicular magnetization film (3) in the present invention.

Furthermore, the same film thickness: 1ooo person's A2□0゜・
S t Ox (7) Composite oxide (ANz 03:
Protective film (2 oz = 6 mol %)
) was formed.

All of these four-layer films were formed in a continuous vacuum without breaking the vacuum halfway.

Finally, use UV curing adhesive (4) to protect the glass.
fFiT5)Fi was bonded together to produce a magneto-optical recording medium sample 6 having the structure shown in FIG.

The magneto-optical properties of the obtained magneto-optical recording medium sample 6, when measured from the substrate 11) side, are as follows: reflectance R=44% at wavelength 830 na+, Kerr rotation angle θz-0,48, coercive force H
,=4 KO.

[Example 5] In the same manner as in Example 4, the front and back surfaces of the perpendicular magnetization 11i (31) were coated with various composite oxides CAR@03: S loz (7
) ratio is below - see table 2).
1G formed various magneto-optical recording medium samples circles 2 to 8
(excluding 6) were manufactured.

[Comparative Example 3] A j! z Oa: Magneto-optical recording medium sample N was prepared in the same manner as in Example 4 using a simple Sin target instead of the mixed sintered target of SiOx.
11 liters were produced. However, the 5iO1 film is
- IKW, growth rate: 100 people/m1n (7) The film thickness was approximately 1000 people.

The magneto-optical properties of the obtained magneto-optical recording medium sample 11kL1, when irradiated with light with a wavelength of 830 rv from the substrate side, are as follows: R = 44%, θ = 0.48, Hc = 5.3 K
O.

Met.

[Comparative Example 4] Magneto-optical recording medium sample 9 was produced in the same manner as in Example 4, except that the AN103 target was simply used instead of the mixed sintered target of ANg03:Siot. However, AJzOs DI was created under the conditions of RF power IKW, film formation rate: 40 people/request ir1, and the film thickness was about 1000 people.

Table 2 (composition of composite oxide; unit: mol %) <Deterioration acceleration test 2> Recording medium sample fish 1 to 9 were placed in an atmosphere at a temperature of 75° C. and a humidity of 90% for 588 hours. This generally accelerates oxidation deterioration of the perpendicularly magnetized film.

After this test, "=90 dragons (1011 inside from the outer circumference)
The coercive force Hc was measured at the position and compared with the value before the test. The results are shown in FIG.

Also, after the above test, r = 92 fl (8 am from the outer circumference)
B E R (Bit Error Ra)
te) was measured and compared with the pre-test value. The results are shown in FIG. BER represents the number of defective locations in the perpendicularly magnetized film.

It can be said that a material with little change in coercive force 11c and BER before and after the test has excellent durability.

〔Effect of the invention〕

As described above, according to the present invention, a magneto-optical recording medium with excellent durability can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic vertical cross-sectional view of the medium of sample No. 6 of the example. FIG. 2 is a graph showing changes in coercive force. FIG. 3 is a graph showing changes in BER. [Explanation of symbols of main parts] 2.--..--.-.Protective film 3.--.---.--Recording layer

Claims (1)

[Scope of Claims] 1 At least one surface of a magnetic recording layer consisting of a perpendicularly magnetized film is coated with a composite oxide consisting of 20 to 85 mol% of a group III metal oxide and 80 to 15 mol% of a group IV metal oxide. 1. A magneto-optical recording medium characterized by being coated with a protective film, either directly or through another layer. 2. The magneto-optical recording medium according to claim 1, wherein the composite oxide comprises 40 to 80 mol% of a Group III metal oxide and 60 to 20 mol% of a Group IV metal oxide. . 3. The magneto-optical recording medium according to claim 1 or 2, wherein the Group III metal oxide is aluminum oxide, and the Group IV metal oxide is silicon oxide.