JP2565092B2 - Magneto-optical recording medium - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium, and more particularly to a magneto-optical recording medium capable of repeated recording and reproduction.

[0002]

2. Description of the Related Art In a magneto-optical recording / reproducing system, a magneto-optical recording medium having a recording layer made of a magnetic film having an easy axis of magnetization in a direction perpendicular to the film surface is used. Recording is performed by reversibly reversing the irradiation of the beam and the application of the magnetic field. Also, when playing back,
This is performed by detecting the direction of magnetization of the recording layer by utilizing one effect, which is a type of magneto-optical effect, as much as possible.

Magneto-optical recording is superior to ordinary magnetic recording in terms of a non-contact access function, medium exchangeability, high recording density, etc., but on the other hand, when rewriting recorded information. It has been considered difficult to perform high-speed rewriting by overwriting because there is a restriction that already recorded information must be erased once. Various proposals have heretofore been made for this high-speed overwrite technique for magneto-optical recording, for example, Japanese Laid-Open Patent Publication No. 1-133242.

In the conventional example described in Japanese Patent Laid-Open No. 1-133242, an interference layer 22, a recording layer 23,
The nonmagnetic metal layer 25, the bias layer 27, and the protective layer 28 are sequentially provided.

In this overwrite method, the leakage magnetic field from the bias layer 27 is positively used in the recording process. Further, since the recording layer 23 and the non-magnetic metal layer 25 are adjacent to each other, the thermal energy applied to the recording layer 23 tends to preferentially flow in the direction perpendicular to the film surface direction. Therefore, there is an advantage in that the formation of marks in the recording process becomes small and it is suitable for high density reproduction.

[0006]

However, in the above-described conventional magneto-optical recording medium, there is a phenomenon that the initial recording / reproducing characteristics are slightly deteriorated as the number of times of repeated recording / reproducing increases when the recording / reproducing is repeated. Is generally known. Therefore, there is a difficulty in durability in terms of high reliability.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a durable magneto-optical recording medium which is suitable for repeated recording and reproduction by improving the disadvantages of the conventional example.

[0008]

According to the present invention, an interference film 12, a recording layer 13, a first diffusion preventing layer 14,
The nonmagnetic metal layer 15, the second diffusion prevention layer 16, the bias layer 17, and the protective layer 18 are sequentially stacked. The recording layer 13 and the bias layer 17 have a configuration in which the easy axis of magnetization is set perpendicular to the film surface. This aims to achieve the above-mentioned object.

[0009]

An embodiment of the present invention will be described below with reference to FIG. In the embodiment shown in FIG. 1, an interference film 12, a recording layer 13, a first diffusion preventing layer 14, a nonmagnetic metal layer 15, a second diffusion preventing layer 16, a bias layer 17 and a protective layer are formed on a substrate 11. 18 are sequentially laminated. The easy magnetization axes of the recording layer 13 and the bias layer 17 are set perpendicular to the film surface.

On the other hand, the deterioration phenomenon from the initial recording / reproducing characteristics when repeatedly performing recording / reproducing, which was a problem in the prior art, was investigated thoroughly, and as a result, the non-magnetic metal layer 15, the recording layer 13, and the bias layer 17 were found. The present invention has been accomplished by finding out the phenomenon of diffusion at the interface between the two.

In this embodiment, a first diffusion barrier layer is provided between the recording layer 13 and the nonmagnetic metal layer 15, and the nonmagnetic metal layer 1 is also used.
The second diffusion prevention layer is provided between the bias layer 5 and the bias layer 17 to prevent the diffusion phenomenon and improve the repeated resistance in recording and reproduction.

Here, the thickness of the first and second diffusion prevention layers is made smaller than the thickness of the non-magnetic metal layer by the flow of heat from the recording layer to the non-magnetic metal layer and further to the bias layer. This is to maintain a thermal design suitable for high-density reproduction without hindering as much as possible. Particularly, the thickness of the first and second diffusion prevention layers is optimally in the range of 10 [angstrom] to 100 [angstrom]. This is because it is within this film thickness range to simultaneously satisfy the diffusion prevention effect and the thermal design suitable for high density reproduction.

To further describe this, as the substrate 11 used in the present embodiment, plastics such as acrylic resin and polycarbonate resin, glass, substrates having grooved resin formed on glass, and the like can be mentioned. On the glass,
An ultraviolet curable resin is used as the resin for forming the groove.

As the interference film 12, for example, SiO, Al
₂ O ₃ , AlN, ZnS, SiN, TaO or the like is used. As the recording layer 13, for example, TbFe, TbC
o, TbFeCo, GdFeCo, GdTbCo, Dy
FeCo, NdFeCo, ptCo, MnBi, MnC
uBi or the like is used. In addition, they include Ti, Cr,
A small amount of Ta, Ni, pt, Nb may be added.

The first and second diffusion prevention layers 14 and 16 are, for example, metal oxides such as TaO, SiO, and Al _2.
O ₃ , MgO, etc., or SiN, Al which is a metal nitride
N or the like is used. As the non-magnetic metal layer 15, for example, Au, Ag, Al, Cu, Ti, Ta or the like is used. For the bias layer 17, TbCo or the like is used. Examples of the protective layer 18 include SiO, Al ₂ O ₃ ,
AlN, ZnS, SiN, TaO or the like is used.

Here, UV overcoating may be performed on the protective film 18 in the medium structure of this embodiment.
Further, the same medium of this embodiment may be bonded to two sheets or a cover substrate.

Next, a specific manufacturing method of the above embodiment will be described. First, after mounting a 2p / glass substrate in a sputtering apparatus and evacuating to 3 × 10 ⁻⁷ Torr or less, argon gas was introduced to sputter-etch the substrate for about 10 Å, followed by argon and nitrogen. 2 × 10 ⁻³ Torr by introducing the mixed gas of
An interference layer having a thickness of 1000 [angstrom] was formed by reactively sputtering a silicon target having a purity of 5N.

Subsequently, an argon gas was introduced to TbFe
By sputtering a CoTi target, 2
A recording layer of 00 [angstrom] was formed.

Next, by introducing argon gas and sputtering a tantalum oxide target, 15
Forming a first diffusion barrier layer having a thickness of [angstrom],
Furthermore, by sputtering a gold target, 1
A nonmagnetic metal layer having a thickness of 00 [angstrom] is formed. Further, a tantalum oxide target was sputtered to form a second diffusion prevention layer having a thickness of 15 [angstrom].

Subsequently, an argon gas was introduced, and TbCo was added.
The target was sputtered to form a 1500 [angstrom] thick bias layer.

Next, by introducing a mixed gas of argon and nitrogen to 3 × 10 ⁻³ Torr and reactively sputtering a 5N-purity silicon target, 800
A thick protective layer was formed. And
A UV overcoat was applied over the protective layer.

When the magneto-optical recording medium thus manufactured was repeatedly recorded and reproduced 10 ⁶ times, the drop from the initial characteristics of C / N was 1 [dB], which was good. For comparison, a similar test was performed on a conventional magneto-optical recording medium without the first and second diffusion prevention layers,
When recording / reproducing was repeated 10 ⁶ times, the C / N drop was about 4 [dB].

[0023]

As described above, according to the present invention, the recording layer having the easy axis of magnetization perpendicular to the film surface and the bias layer are provided, and the interference layer, the recording layer, and the first diffusion layer are formed on the substrate. By sequentially laminating the prevention layer, the non-magnetic metal layer, the second diffusion prevention layer, the bias layer and the protection layer, it is possible to obtain a magneto-optical recording medium having very excellent repeated recording / reproducing characteristics.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a conventional example.

[Explanation of symbols]

 Reference Signs List 11 substrate 12 interference layer 13 recording layer 14 first diffusion prevention layer 15 non-magnetic metal layer 16 second diffusion prevention layer 17 bias layer 18 protective layer

Continuation of front page (56) Reference JP-A-2-227844 (JP, A) JP-A-1-173453 (JP, A) JP-A-62-65250 (JP, A) JP-A-3-8148 (JP , A) JP-A-5-47055 (JP, A) JP-A-4-137239 (JP, A)

Claims (5)

(57) [Claims] 1. An interference film, a recording layer, a first diffusion preventing layer, a nonmagnetic metal layer, a second diffusion preventing layer, a bias layer and a protective layer are sequentially laminated on a substrate, and the recording layer and the recording layer are formed. The magneto-optical recording medium is characterized in that the easy axis of magnetization of the bias layer is set perpendicular to the film surface. 2. The magneto-optical recording medium according to claim 1, wherein the first diffusion prevention layer and the second diffusion prevention layer are made of a metal oxide. 3. The magneto-optical recording medium according to claim 1, wherein the first diffusion prevention layer and the second diffusion prevention layer are made of metal nitride. 4. The first diffusion barrier layer and the second diffusion barrier layer are set to have a film thickness smaller than that of the nonmagnetic metal layer. Or 3
A magneto-optical recording medium according to claim 1. 5. The first diffusion prevention layer and the second diffusion prevention layer have a film thickness set in a range of 10 [angstrom] to 100 [angstrom]. 2. The magneto-optical recording medium according to 2, 3, or 4.