JPH09180277A - Magneto-optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magneto-optical disk having improved jitter characteristic and magnetizing characteristic. SOLUTION: This disk is constituted by successively laminating a dielectrics layer 5, a magnetic layer 6 consisting of GdDyFeCo having a easily-magnetized axis perpendicular to the film surface, a dielectrics layer 7 and a reflecting layer 8 on a substrate 1. In this case, the magnetic layer 6 is made by atomic composition rate within a range shown by formula I, atomic composition rate of whole magnetic layer 6 at an average value is set within a range shown by formula II and, further, the (b) value in a layer region on a dielectrics layer 7 side is made larger than the (b) value in a layer region at a dielectrics layer 5 side. (I): GdhDyiFejCok (where, h+i+j+k=1), h+i<=0.30, k>=0.01, (II): GdaDybFecCod (where, a+b+c+d=1), 0.05<=a<=0.20, 0.03<=b<=0.10, 0.50<=c<=0.90, 0.02<=d<=0.20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvements in magneto-optical disks.

[0002]

2. Description of the Related Art Japanese Patent Laid-Open No. 61-117747 discloses a magneto-optical disk having a layer structure in which a low coercive force layer of GdFeCo having a high Curie point and a high coercive force layer of TbFe having a low Curie point are exchange-coupled. Proposed, and fair and fair 3-
No. 9545 has recording layers such as TbFe and DyFe having a low Curie point and GdFe and GdFe having a large Kerr rotation angle.
A magneto-optical recording medium having a laminated structure with a reproducing layer such as Bi has been proposed, and both have achieved high C / N.

[0003]

However, according to the magneto-optical disk described in Japanese Patent Laid-Open No. 61-117747, although it is suitable for pit position recording, in pit edge recording, especially for jitter characteristics. Thus, there is a problem that the Curie temperatures of both layers cannot be optimized, resulting in increased jitter. There is a remarkably large difference in coercive force (Hc) between the low coercive force layer and the high coercive force layer, which also causes a problem of increasing jitter. Further, the magneto-optical recording medium proposed in Japanese Examined Patent Publication No. 3-9545 has the same problem.

Therefore, an object of the present invention is to provide a high performance magneto-optical disk with improved jitter characteristics.

[0005]

The magneto-optical disk of the present invention comprises a first dielectric layer on a transparent disk substrate, a magnetic layer made of GdDyFeCo having an easy axis of magnetization perpendicular to the film surface, and a second dielectric layer. The magnetic layer is formed by sequentially laminating a magnetic layer and a reflective layer, and the atomic composition ratio of the entire magnetic layer is set within the range shown in (b) below as an average value. In addition, the b value of the layer region on the second dielectric layer side is larger than the b value of the layer region on the first dielectric layer side.

(A): Gdh Dyi Fej Cok (however, h + i + j + k = 1) h + i ≤0.30, k ≥0.01 (b): Gda Dyb Fec Cod (however, a + b
+ C + d = 1) 0.05 ≦ a ≦ 0.20 0.03 ≦ b ≦ 0.10 0.50 ≦ c ≦ 0.90 0.02 ≦ d ≦ 0.20 According to the magneto-optical disk having the above configuration, In the magnetic layer, the b value of the layer region on the side of the second dielectric layer is made larger than the b value of the layer region on the side of the first dielectric layer, so that the latter layer region serves as a reproducing layer, The layer regions form a recording layer, and the Curie temperatures of both layer regions can be optimized by changing the Co composition. In addition, the coercive force (H
c) The difference is reduced, and as a result, the jitter characteristic is improved.

Furthermore, since the magneto-optical disk of the present invention is rich in transition metal in any layer region of the magnetic layer, exchange coupling does not occur and magnetization becomes easy.

[0008]

FIG. 1 shows a magneto-optical disk M according to the present invention.
FIG. 2 is a cross-sectional view taken along the line XX of FIG. 1. Further, FIG. 3 shows a layer structure of a thin film forming the magneto-optical disk M.

A substrate 1 made of a polycarbonate resin is used as the transparent disk substrate. A plurality of tracking grooves 2 are concentrically formed on one side of the substrate 1, and a hub mounting hole 3 is formed in the center thereof. Is provided. A thin film 4 is coated on the surface on which the tracking grooves 2 are formed.

The thin film 4 is a dielectric layer 5 made of sialon having a thickness of 500 to 900Å as a first dielectric layer,
The thickness of the magnetic layer 6 and the second dielectric layer is 50 to 250.
Dielectric layer 7 made of Å sialon, thickness 600 ~
Reflective layer 8 consisting of 1200Å titanium-containing aluminum
And a protective resin layer 9 made of an ultraviolet curable resin. The dielectric layer 5, the magnetic layer 6, the dielectric layer 7, and the reflective layer 8 are formed by sputtering, and then the protective resin layer 9 is formed by coating.

The dielectric layers 5 and 7 may be formed of silicon oxide, aluminum nitride, titanium oxide, tantalum oxide, etc. in addition to sialon, and the reflection layer 8 may be made of Al other than titanium-containing aluminum. Ti, A
It may be formed of at least one metal or alloy of u, Ag, Cu, Pt, Cr and Ni.

Regarding the magnetic layer 6, GdDyFeC
and the composition ratio of each atom is in the following range in average value, and further, the layer region 6a on the dielectric layer 5 side and the dielectric layer 7
When it is bisected with the layer region 6b on the side, it is exchange-coupled, and the b value is larger in the layer region 6b than in the layer region 6a. Further, between the two layer regions 6a and 6b,
The composition ratio of b may be changed gradually or stepwise.

Gda Dyb Fec Cod (where a
+ B + c + d = 1) 0.05 ≦ a ≦ 0.20, preferably 0.10 ≦ a ≦
0.15 0.03 ≦ b ≦ 0.10 Suitably, 0.04 ≦ b ≦
0.08 0.50 ≦ c ≦ 0.90 Suitably, 0.60 ≦ c ≦
0.80 0.02 ≦ d ≦ 0.20 Preferably 0.05 ≦ d ≦
0.15 The reason for limiting the range of each atomic composition is as follows.

If a exceeds 0.20, a rare earth metal-rich portion occurs, and if it is less than 0.05, jitter increases.

If b exceeds 0.10, a rare earth metal rich portion is generated, and if it is less than 0.03, the coercive force Hc is significantly reduced.

If c exceeds 0.90, the coercive force Hc becomes remarkably small, and if it is less than 0.50, a rare earth metal rich portion is generated.

When d exceeds 0.20, the Curie temperature Tc
Becomes significantly higher, the recording power increases, and if it is less than 0.02, the jitter increases.

The magnetic layer 6 has an atomic composition ratio in the range shown below. Gdh Dyi Fej Cok (however, h + i + j + k
= 1) h + i ≦ 0.30, k ≧ 0.01 By setting h + i ≦ 0.30 in this way, the rare earth metal becomes rich.

Then, in the magneto-optical disk M having the above structure, while the substrate 1 is rotated, a laser beam having a wavelength of 680 nm is irradiated through the substrate 1 and tracking is performed along the tracking groove 2, the laser beam is the dielectric layer. 5, reaches a magnetic layer 6 and a part thereof passes through the magnetic layer 6 and is reflected by a reflecting layer 8 through a dielectric layer 7. The reflected light goes to the magnetic layer 6 or undergoes multiple reflection.

Thus, according to the magneto-optical disk M of the present invention, by providing the thin film 4 having the above-mentioned layer structure, the jitter characteristic is improved and the magnetization characteristic is further improved.

[0021]

Next, an embodiment will be described. (Example 1) A substrate 1 made of a polycarbonate resin was prepared, baked at 100 ° C for 10 hours, and then 1 x.
The substrate was evacuated in a vacuum chamber of 10 ⁻⁵ Pa for 3 hours, and then a thin film 4 was formed on the substrate 1 as a dielectric layer 5 made of sialon having a thickness of 600 Å, and the atomic composition of each layer region was changed as shown in Table 1. The magnetic layer 6 (thickness of the layer region 6a: 100
Å, the thickness of the layer area 6b: 200 Å) and the thickness is 200 Å
Dielectric layer 7 made of sialon with a thickness of 1000Å
Various magneto-optical disks were prepared by sputtering the reflective layer 8 made of titanium-containing aluminum.

[0022]

[Table 1]

For each magneto-optical disk, the jitter and magnetizing characteristics, the coercive force and the Curie temperature in each layer region were evaluated, and the results shown in Table 2 were obtained. The magnetization characteristics are indicated by a circle when uniformly magnetized when an external magnetic field of 15 KOe is applied at room temperature.
The case where the magnets were not uniformly magnetized was indicated by a cross.

[0024]

[Table 2]

As is clear from the results shown in Table 2, the magneto-optical disk No. 1 of the present invention was Nos. 1 to 3 had a jitter of 7.0 or less, and all had good magnetization characteristics.

However, the sample No. In 9 and 10, k was 0.01 or less, and the jitter was large. Sample No. 11, the layer region 6a is rich in rare earth, and the sample No. In No. 12, since the layer region 6b was rich in rare earths, h + i was 0.30 or more and the magnetization characteristics were deteriorated.

The sample No. In Nos. 4, 8 and 9, the jitter is large in that the difference in coercive force between the two layer regions a and b is large.

[0028]

As described above, according to the present invention, GdDy
D of exchange coupled two-layer magnetic layer made of FeCo
By changing the y composition ratio, the jitter characteristics are improved,
Further, it is possible to provide a high-performance magneto-optical disk with improved magnetization characteristics.

[Brief description of the drawings]

FIG. 1 is a plan view of a magneto-optical disk M according to the present invention.

FIG. 2 is a sectional view of a magneto-optical disk M of the present invention.

FIG. 3 is a cross-sectional view showing a layer structure of a thin film according to the present invention.

[Explanation of symbols]

 M Magneto-optical disk 1 Substrate 4 Thin film 5, 7 Dielectric layer 6 Magnetic layers 6a, 6b Layer region 8 Reflective layer 9 Protective resin layer

Claims (1)

[Claims] 1. A first dielectric layer on a transparent disk substrate,
A magnetic layer made of GdDyFeCo having an easy axis of magnetization perpendicular to the film surface, a second dielectric layer, and a reflective layer are sequentially laminated, and the magnetic layer is formed according to the atomic composition ratio in the range shown in (a) below. , The atomic composition ratio of the entire magnetic layer is set to an average value in the range shown in (b) below, and the b value of the layer region on the second dielectric layer side is set to the b value of the layer region on the first dielectric layer side. A magneto-optical disk characterized by being made larger than that. (A): Gdh Dyi Fej Cok (however, h + i
+ J + k = 1) h + i ≦ 0.30, k ≧ 0.01 (b): Gda Dyb Fec Cod (where a + b
+ C + d = 1) 0.05 ≦ a ≦ 0.20 0.03 ≦ b ≦ 0.10 0.50 ≦ c ≦ 0.90 0.02 ≦ d ≦ 0.20