JPH0991779A - Magneto-optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magneto-optical disk of a low cost having high performance by laminating a reading out layer consisting of a transition metal of a prescribed atomic compsn. formula and a recording layer formed by adding a rare earth metal to the transition metal of the same compsn. ratios. SOLUTION: A dielectric layer 5, the reading out layer 6a, a recording layer 6b, a dielectric layer 7 and a reflection layer 8 are successively laminated on a substrate 1. The atomic compsn. formula of the reading out layer 6a is Fe1-x Cox (0.10<=X<=0.50) and the thickness thereof is 50 to 150Å. The recording layer 6b is formed by adding Tb to the FeCo ally of the same compsn. ratios as the compsn. ratios of the reading out layer 6a. Then, there is no need for disposing two film forming chambers for the recording layer and the reading out layer and the thickness of the reading out layer 6a is reduced at the time of successively forming both layers of the reading out layer 6a and the recording layer 6b by sputtering, by which the manufacturing cost is reduced. Since the atomic compsn. ratios of the reading out layer 6a are easily and strictly settable, the reading out characteristics, such as C/N are additionally improved.

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 A magneto-optical disk having a read layer and a recording layer exchange-coupled to each other has been proposed (for example, Japanese Patent Laid-Open No. Sho 6).
3-18545). According to the publication, the recording layer has R
-FeCo-M (R: 1 or 2 elements selected from Tb and Dy, 1 selected from M: Cr and Al)
Seed) is proposed, in which GdFeCo is used for the readout layer and exchange coupling is performed in these two layers, and it is stated in the examples that the thickness of each layer is 500Å.

[0003]

However, both the recording layer and the reading layer are composed of an alloy of a rare earth metal and a transition metal, and the transition metal commonly uses a FeCo alloy. Since they are different, it is necessary to provide two film forming chambers for the recording layer and the reading layer when sequentially forming both layers by sputtering, and as a result, the manufacturing cost is significantly increased.

Further, if an attempt is made to form a read-out layer having a thickness of 500 Å, the manufacturing time is lengthened due to the large thickness, the amount of material used is increased, and the manufacturing cost is also increased for this reason.

Moreover, regarding the read layer, GdFe is used.
Since it consists of ternary atoms like Co, the composition ratio between these individual atoms must be set strictly, but in general, the composition control becomes difficult as it becomes a multi-element system, and moreover, reading of GdFeCo Since the coercive force is small when the layer is used, there is a problem in that the composition range is further narrowed down in order to obtain the optimum coercive force, which requires a fine adjustment in the sputtering conditions. In addition, there is a problem that the reading characteristics are not yet satisfactory.

Therefore, it is an object of the present invention to provide a high performance and low cost magneto-optical disk with improved read characteristics such as C / N and reduced manufacturing cost.

[0007]

The magneto-optical disk of the present invention comprises a transparent disk substrate, a first dielectric layer, and an atomic composition formula of Fe _1-x Co _x (0.10≤x≤0.50). And
In addition, a reading layer having a thickness of 50 to 150 Å, a recording layer in which Tb is added to a FeCo alloy having the same composition ratio as the reading layer, a second dielectric layer, and a reflecting layer are sequentially laminated. And

[0008]

1 is a block diagram of the magneto-optical disk M of the present invention (diameter 3.5 inches).
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.

This thin film 4 has a film thickness of 8 as a first dielectric layer.
A dielectric layer 5 made of 00Å sialon, a read layer 6a made of FeCo, a recording layer 6b made of TbFeCo, a dielectric layer 7 made of sialon having a film thickness of 400Å as a second dielectric layer, and a film thickness of 600Å 2 is a laminated structure of the reflection layer 8 made of aluminum and the protective resin layer 9 made of an ultraviolet curable resin. Read layer 6a and recording layer 6
Exchange-coupled by two layers with b, and in the present embodiment, a combination of these two layers is referred to as an exchange-coupled layer 6.

For the readout layer 6a, the X value represented by the atomic composition Fe _1-x Co _x is 0.10 ≦ x ≦ 0.5.
The range is preferably 0, and the recording layer 6b is made by adding Tb to a FeCo alloy having the same composition ratio as that of the read layer 6a, and when the X value is less than 0.10. Since the C / N value is small, sufficient read characteristics cannot be obtained. When the X value exceeds 0.50, the C / N value is sufficient, but on the other hand, the laser power required for recording becomes high. There is a problem in practical use.

The thickness of the readout layer 6a is 50-15.
The range of 0 Å is recommended, and if it is less than 50 Å, the effect of the car rotation angle becomes small and the C / N value decreases,
When it exceeds 50 Å, the perpendicular magnetization is stopped and the C / N value is lowered.

Then, in the magneto-optical disk M having the above structure, while the substrate 1 is rotated, a laser beam having a wavelength of 780 nm is irradiated through the substrate 1 and tracking is performed along the tracking groove 2, the laser beam is the dielectric layer. 5 to reach the exchange coupling layer 6, and a part of the light passes through the exchange coupling layer 6 and is reflected by the reflection layer 8 through the dielectric layer 7, and the reflected light reaches the exchange coupling layer 6.

Configuration of Magnetron Sputtering Apparatus Next, a magnetron sputtering apparatus 10 for forming the exchange coupling layer 6 will be described with reference to FIG. Reference numeral 13 denotes a vacuum chamber. Inside the vacuum chamber 13, a revolution mechanism 14 is provided above, a revolution mechanism 15 is formed in the revolution mechanism 14, and the film formation substrate 11 is fixed to the revolution mechanism 15. There is. A rare earth metal targate (Tb metal) 12 and a transition metal targate (FeCo alloy) 16 are arranged so as to face the public / self-rotating mechanisms 14 and 15 and the substrate 11, and a magnet 17 and a cathode 18a are arranged on these targates 12 and 16. , 18b are provided. Then, in a part of the vacuum chamber 13, A which is a sputtering gas is used.
An r gas inlet 19 and an exhaust port 20 for exhausting the residual gas after film formation are provided.

In order to form the exchange coupling layer 6 by the magnetron sputtering apparatus 10 having the above-mentioned structure, the film formation substrate 11 (substrate 1) is rotated by the rotation mechanism 15, and the rotation mechanism 15 is rotated by the revolution mechanism 14. The substrate 11 for film formation is revolved and revolved, and
Ar gas is introduced through the inlet 19 and electric power is applied to the cathode 18 to perform sputtering.

Then, in order to sequentially form the read layer 6a and the recording layer 6b, power is not applied to the cathode 18a for the rare earth metal targate 12, but power is applied to the cathode 18b for the transition metal targate 16. Then, the readout layer 6a is formed on the film formation target substrate 11 under such film formation conditions, and then the cathode 18a for the rare earth metal targate 12 while maintaining the film formation conditions for the readout layer 6a.
Is also applied to form a recording layer 6b formed by adding Tb to a FeCo alloy having the same composition ratio as that of the readout layer 6a.

Thus, according to the magneto-optical disk M of the present invention, the above atomic composition formula is Fe _1-x Co _x (0.10≤x≤
0.50) and a reading layer 6a having a thickness of 50 to 150Å and F having the same composition ratio as that of the reading layer 6a.
By forming the exchange coupling layer 6 by sequentially laminating the recording layer 6b formed by adding Tb to the eCo alloy, during sputtering for forming both layers 6a and 6b,
Since only the common transition metal targate 16 and rare earth metal targate 12 are used, it is not necessary to provide two film forming chambers for the recording layer and the reading layer, and the number of film forming chambers can be reduced. Manufacturing costs have been reduced.

Moreover, the thickness of the readout layer 6a is 50 to 1
Since it can be reduced to 50 Å, the film formation time and the amount of materials used are significantly reduced as compared with the conventional read layer having a thickness of 500 Å, which also reduces the manufacturing cost.

Further, since the read layer 6a is made of FeCo binary atoms, the atomic composition ratio can be set easily in manufacturing, as compared with the conventional ternary atoms. Manufacturing costs were also reduced by easy manufacturing operations. In addition, an excellent coercive force was obtained as compared with the magneto-optical disk using the read layer of GdFeCo.

[0020]

EXAMPLES Examples based on the above manufacturing method will be described in detail below. As shown in Table 1, the thickness of the readout layer 6a and Fe
11 kinds of prototypes were made by changing the X value of _1-x Co _x in various ways. However, the composition of the recording layer 6b is Tb.
_The thickness was _0.15 (Fe _1-x Co _x ) _0.85 and the thickness was 150 Å. In this example, the protective resin layer 9 was not formed before the measurement.

[0021]

[Table 1]

When the C / N of each sample was measured, the results shown in FIGS. 5 and 6 were obtained. In FIG. 1-4 and sample No. 10 and 11
Based on the above, the thickness of the readout layer 6a is set to 70Å,
The C / N and the laser power required for recording when the X value of Fe _1-x Co _x is changed are shown. Moreover, in FIG. Based on 4 to 9, the C / N is shown when the X value of Fe _1-x Co _x of the reading layer 6a is set to 0.15 and the thickness is changed.

In these measurements, the rotation speed was 3
000 rpm, recording power 4 to 15 mW, reproduction power 1
The recording was performed at a recording portion with a radius of 24.1 mm under the conditions of mW, recording frequency 5.84 MHz and recording pulse width 20 nanoseconds.

As is clear from the result shown in FIG. 5, the X value is 0.
In the case of 1 to 0.5, excellent characteristics of C / N of 50 dB or more and recording power of 10 mw or less were obtained. From the result of FIG. 6, the readout layer 6a has a thickness of 50 to
It can be seen that when 150Å, excellent characteristics of C / N of 50 dB or more were obtained.

Moreover, the read layer 6a of Fe _1-x Co _x
By using, it was easier to adjust the atomic ratio compared with the read layer of GdFeCo, and as a result, a high C / N was obtained as desired.

[0026]

As described above, according to the magneto-optical disk of the present invention, the atomic composition formula is Fe _1-x Co _x (0.10 ≦ x ≦
0.50) and a reading layer having a thickness of 50 to 150Å and a recording layer obtained by adding Tb to a FeCo alloy having the same composition ratio as that of the reading layer. When the films are sequentially formed, it is not necessary to provide two film forming chambers for the recording layer and the reading layer, and the thickness of the reading layer is further reduced, which reduces the manufacturing cost.

According to the magneto-optical disk of the present invention,
The atomic composition ratio of the readout layer can be set easily and strictly,
Further, the read characteristics such as C / N are improved, and thereby a high performance and low cost magneto-optical disk can be provided.

[Brief description of 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 magneto-optical recording layer.

FIG. 4 is a schematic diagram of a magnetron sputtering apparatus.

FIG. 5 is a diagram showing C / N and recording power.

FIG. 6 is a diagram showing C / N.

[Explanation of symbols]

 M Magneto-optical disk 1 Substrate 4 Thin film 5, 7 Dielectric layer 6 Exchange coupling layer 6a Read-out layer 6b Recording layer 8 Reflective layer 9 Protective resin layer

Claims (1)

[Claims] 1. A first dielectric layer on a transparent disk substrate,
The atomic composition formula is Fe _1-x Co _x (0.10 ≦ x ≦ 0.5
0) and having a thickness of 50 to 150Å, a recording layer in which Tb is added to a FeCo alloy having the same composition ratio as the reading layer, a second dielectric layer, and a reflective layer are sequentially laminated. A magneto-optical disk characterized by the above.