JPH071559B2 - Magneto-optical disk - Google Patents

Description

TECHNICAL FIELD The present invention relates to a magneto-optical disk, and more particularly to a magneto-optical disk having a protective film for protecting a magneto-optical recording medium layer.

[Conventional technology]

A magneto-optical disk that records, reproduces, and erases information using laser light is capable of recording high-density information.
Moreover, it is widely used in each direction because it can erase information and record additional information.

As a magneto-optical recording medium for this type of magneto-optical disk, Tb
-Fe-based, Tb-Fe-Co-based, Gd-Tb-Fe-based, etc. are used, but none of them are sufficient in terms of corrosion resistance such as oxidation.

Therefore, various means for protecting the magneto-optical recording medium layer in the magneto-optical disk have been proposed.

For example, a magneto-optical recording medium is sandwiched between films that do not contain oxygen, oxygen is prevented from being mixed when the magneto-optical recording medium is created, and a metal film that is easily oxidized is formed on the uppermost layer,
A method has been proposed in which oxygen from the outside is used to oxidize the metal film to prevent the oxygen from being mixed in (Japanese Patent Laid-Open No. 59-59).
-110052). Furthermore, between the magneto-optical recording medium and the substrate,
A method has also been proposed in which a reducing dielectric film that takes in and stabilizes oxygen is formed, and the presence of this derivative film prevents oxidation of the magneto-optical recording medium (JP-A-59-1100).
No. 56). Further, there has been proposed a system in which a magneto-optical recording medium is protected by a protective film of Al, Bi, Pb or the like which is impermeable and has a high moisture-proof effect (JP-A-58-80142).

However, none of the proposed methods is sufficient to prevent the magneto-optical recording medium from being oxidized or corroded in an atmosphere containing humidity, oil and water in the air.

Therefore, from a practical point of view, when the magneto-optical recording medium is used for a long time in such an atmosphere, the magneto-optical recording medium is deteriorated, the recording condition is changed, and the problem of dropout of recorded information and C Problems such as a decrease in the / N ratio were not completely solved.

[Problems to be Solved by the Invention]

The present invention solves the drawbacks in the protection of a magneto-optical recording medium in a conventionally proposed magneto-optical disk, protects the magneto-optical recording medium with a non-breathable and moisture-impermeable protective film, and the entire film structure is An object of the present invention is to provide a magneto-optical disk having excellent magneto-optical recording / reproducing characteristics, which is simple, has a small number of film forming steps in preparation, does not complicate the manufacturing technique.

[Structure of Invention]

In this invention, as shown in FIG. 1, on a transparent substrate 1 formed of a transparent polymer material such as glass, polycarbonate, acrylic, epoxy, polymethylpenlane,
As the first layer, the composition is represented by TaO _x, NbO _x or _{Ta 1-y Nb y O x} ( where, 1.6 ≦ x ≦ 2.3,0 <y <1), thickness 20
0 to 1000Å, the dielectric film 3-1 for protecting the magneto-optical recording medium and increasing the apparent Kerr rotation angle, the magneto-optical recording medium layer 2 as the second layer, and the composition TaO as the third layer. _z , NbO _z or Ta _1-w Nb _w O _z (where 1.6 ≦ x ≦ 2.3,
A protective film 3-2, which is represented by 0 <w <1) or which is a metal and has a film thickness of 200 Å or more, is formed to protect the magneto-optical recording medium.

This first-layer dielectric film protects the magneto-optical recording medium layer and multiple-reflects the light reflected by the magneto-optical recording medium layer out of the reading light of the information, and reflects the reflected light for reading. It is formed to increase the apparent Kerr rotation angle and improve the regeneration C / N ratio (car enhancement effect). The components of the film needs to be represented by TaO _x, NbO _x or _{Ta 1-y Nb y O x} . Since this component is stable in a wide range of x, it is necessary to introduce high-purity oxygen for the purpose of (1) preventing the formation of an oxygen-deficient film, which is observed when sputtering or vapor-depositing general oxides. This is because (2) the disadvantage that the film formation rate is significantly reduced by introducing oxygen is eliminated. The conditions of 1.6 ≦ x ≦ 2.3 and 0 <y <1 are set for x and y indicating the composition of the film. When x is less than 1.6, metallic Ta, Nb in the dielectric film
Is formed, a homogeneous and transparent film is not formed, while x is 2.
If it exceeds 3, unreacted oxygen becomes excessive and the magneto-optical recording medium deteriorates after long-term use. Furthermore, x is 2.
If it exceeds 7, oxygen deteriorates the magneto-optical recording / reproducing characteristics of the magneto-optical disk obtained by mixing oxygen into the layer during formation of the magneto-optical recording medium layer. This dielectric film is formed to a thickness of 200 to 1000Å by high frequency sputtering. Film thickness 2
If it is less than 00Å, nonuniformity of the film increases due to pinholes, etc., and information dropout occurs due to oxidation of the magneto-optical recording medium layer, and the effect of protecting this medium layer is insufficient, and car enhancement The effect is not fully exerted. On the other hand, when the film thickness exceeds 1000Å, the variation in the film thickness increases and the car enhancement effect cannot be effectively used.

As the magneto-optical recording medium layer, TbFe, GdCo, TbCo, DyCo, GdTb
Rare earth transition metal alloy thin films such as Fe, GdFeCo, TbDyFe, GdTbDyFe, TbDyFeCo and Sn, Zn, Ge, Pb, Si, Bi, B, Cr, Al, P
Rare earth transition metal alloy thin films containing t, Ni, etc. added are used, and these thin films are formed to a film thickness of, for example, 1000 L by vacuum deposition or sputtering.

The third protective film is formed to protect the magneto-optical recording medium layer and has a composition of TaO _z , NbO _z or Ta _1-w Nb _w O _z (however, 1.
It is represented by 6 ≦ z ≦ 2.3 and 0 <w <1) or is a known metal such as Al, Bi, Pb as a protective film. The components of this membrane are
It does not necessarily have to be the same as the composition of the dielectric of the layer. The reason that z is set to a range of 1.6 to 2.3 is that the effect as the above-mentioned protective film is not sufficiently exhibited if it is out of this range. x and z do not necessarily have to be the same. y and w do not necessarily have to be the same. This protective film is formed to a thickness of 200 Å or more by high frequency sputtering in the case of TaO _z , NbO _z or Ta _1-w Nb _w O _z and by high frequency sputtering, DC sputtering or vacuum evaporation in the case of metal. . The lower limit of the film thickness is set as described above. If the lower limit is less than this lower limit, the film nonuniformity due to pinholes or the like increases and the effect of protecting the magneto-optical recording medium layer cannot be sufficiently obtained.

〔Example〕

The magneto-optical disk of the present invention will be described in detail below based on its embodiments along with the manufacturing method.

Tables 1 to 3 show each Example of the present invention (Examples 1 to 1).
The composition and film thickness of the magneto-optical disk of Example 9) and the magneto-optical disk of each Comparative Example (Comparative Examples 1 to 27) corresponding to each Example and not satisfying the composition condition or film thickness condition of the present invention. And the initial C / N ratio and the time-dependent C / N ratio measured by the inventors are shown.

In each of the examples and comparative examples shown in Tables 1 to 3, as shown in FIG. 1, by means of high frequency sputtering on a transparent substrate 1 of polycarbonate having a thickness of 1.2 mm,
Forming a first layer dielectric film 3-1.
−1, a second layer of a magneto-optical recording medium layer 2 having a composition of Tb _0.21 Fe _0.55 Co _0.24 is formed to a film thickness of 1000Å, and a third protective film 3-2 is formed on the magneto-optical recording medium layer 2. It has a formed film structure.

The magneto-optical disk having the protective film thus formed was recorded at a recording frequency of 2 MHz (RBW30 kHz) and a laser power of 4 mW and reproduced at a reproducing laser power of 1 mW. The first C / N ratio when reproduced immediately after recording
The initial C / N ratios (dB) in Tables to 3 are the C / N ratios obtained by reproducing after leaving the magneto-optical disk in an atmosphere of 60 ° C and 90% RH for 1000 hours. Table 3 to Table 3 C / N over time
Is.

In addition, Table 4 shows comparative examples (Comparative Examples 28 to 36) having the same film structure as those in Tables 1 to 3 and the similarly measured initial and aged C / N ratios were obtained. is there.

In each of the examples, it was confirmed that the presence of the dielectric film 3-1 and the protective film 3-2 provided a magneto-optical disk having excellent long-term durability and stable magneto-optical recording / reproducing characteristics. To be done. However, in the comparative example, x in the first layer is
When less than 1.6 (Comparative Examples 1, 10, 19) and over 2.3 (Comparative Examples 2, 11, 20, 28, 29, 30, 34, 35, 36), the thickness of the first layer is less than 200Å In both cases (Comparative Examples 3, 12, 21), exceeding 1000Å (Comparative Examples 4, 13, 22) and oxygen introduced during sputtering (Comparative Examples 9, 18, 27)
There is a drawback that the ratio is greatly reduced. Also, the z of the third layer is
When less than 1.6 (Comparative Examples 6,15,24) and over 2.3 (Comparative Examples 7,16,25,31,32,33,34,35,36), the thickness of the third layer is less than 200Å In both cases (Comparative Examples 5, 14, 23) and when oxygen was introduced during sputtering (Comparative Examples 8, 17, 26), there was a drawback that the decrease in C / N ratio over time was large.

Therefore, in each of the comparative examples, a magneto-optical disk having excellent long-term durability and stable magneto-optical recording / reproducing characteristics cannot be obtained.

The present invention is not limited to the configurations of the respective embodiments described above, and for example, a configuration in which an ultraviolet curable resin is further coated on the protective film 3-2 can also be realized.

Alternatively, it is also possible to realize a structure in which the magneto-optical disk constructed according to the present invention is opposed to each other, a facing space is formed by a spacer, and the facing space is filled with an inert gas.

〔The invention's effect〕

As described in detail above, according to the present invention, the film forming process is simple, the magneto-optical recording medium layer is protected in a state where the air permeability and the moisture impermeability are maintained, and it has long-term durability and a car enhancement effect. It is possible to provide a magneto-optical disk having excellent magneto-optical recording / reproducing characteristics that effectively utilizes the above.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of an embodiment of the magneto-optical disk of the present invention. 1: transparent substrate, 2: magneto-optical recording medium layer, 3-1: dielectric film, 3
-2: protective film.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mikihiko Ito 3-18-5 Chugoku, Ichikawa-shi, Chiba Central Research Institute, Sumitomo Metal Mining Co., Ltd. (56) Reference JP-A-61-32242 (JP, A) Kai 60-197966 (JP, A)

Claims (1)

[Claims] 1. A magneto-optical disk in which a magneto-optical recording medium layer is formed on a transparent substrate, and the magneto-optical recording medium layer is irradiated with a light beam to write and read information.
On the transparent substrate, as the first layer, the composition is TaO _x , NbO _x ,
Or _{Ta 1-y Nb y O x} ( where, 1.6 ≦ x ≦ 2.3,0 <y <1)
And a film thickness of 200 to 1000Å, which protects the magneto-optical recording medium layer and increases the apparent Kerr rotation angle, the second layer is the magneto-optical recording medium layer, and the third layer
The layer has a composition represented by TaO _z , NbO _z , or Ta _1-w Nb _w O _z (where 1.6 ≦ z ≦ 2.3, 0 <w <1) or is made of a metal and has a film thickness of 200 Å or more. And a protective film for protecting the magneto-optical recording medium.