JPH06282887A - Magneto-optical recording medium and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a magneto-optical recording medium and a method for manufacturing the same in which an intensity of a laser light need not be necessarily varied from an inner periphery toward an outer periphery of a disk in the case of recording. CONSTITUTION:A dielectric layer 2, a recording layer 3, a dielectric layer 4 and a reflecting layer 5 are laminated on a transparent board 1, and the layers are so formed that thicknesses are reduced in a quadratic function manner to a distance from an inner periphery. Thus, a recording sensitivity is raised from the inner periphery toward an outer periphery, and the sensitivity required at not only the inner periphery but also the outer periphery can be satisfied. Formations of such layers can be conducted by sputtering at an outer most periphery of the board with a shielding member.

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 for recording, reproducing and erasing information by using a laser beam and a method for manufacturing the same.

[0002]

2. Description of the Related Art Magneto-optical recording media have become popular rapidly in recent years because they have a large storage capacity and can record, reproduce and erase data, and their access speed is much faster than that of magnetic tapes. The magneto-optical recording medium rotates while recording, reproducing,
Since the erasing is performed, the linear velocity in the outer peripheral portion is higher than that in the inner peripheral portion, and the irradiation time of the laser beam per unit area is shortened. Therefore, at the time of recording, it is necessary to heat the outer peripheral portion to a certain temperature or higher with a laser beam stronger than the inner peripheral portion.
However, in this case, since the intensity of the recording laser light must be increased from the inner circumference toward the outer circumference, it is necessary to increase the power margin of the semiconductor laser. Further, the power control circuit and the like are complicated, which is a burden on the drive device.

Further, when attempting to solve this problem on the magneto-optical recording medium side, the composition of the magnetic layer is a factor closely related to the recording sensitivity. Therefore, the composition of the magnetic layer extends from the inner circumference to the outer circumference. It can be changed. However, it is technically very difficult to change the composition of the magnetic layer from the inner circumference to the outer circumference, and the composition of the magnetic layer also affects recording characteristics other than the recording sensitivity. The solution attempted by changing the composition of the layers is not suitable.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magneto-optical recording medium which does not need to change the intensity of laser light from the inner circumference to the outer circumference of a disk during recording, and a method of manufacturing the same. is there.

[0005]

In order to achieve the above-mentioned object, according to the present invention, a magneto-optical recording medium comprising a transparent substrate and a plurality of layers including at least recording layers,
A magneto-optical recording medium is provided, wherein the plurality of layers are formed so that the film thickness of each layer decreases quadratically with respect to the distance from the inner circumference. Further, according to the present invention, there is provided a method for manufacturing the above-mentioned magneto-optical recording medium, characterized in that a shielding member is placed on the outermost peripheral portion of the transparent substrate and each layer is formed by a sputtering method. A method of manufacturing the same is provided.

[0006]

According to the invention of claim 1, since the film thickness of each layer decreases from the inner circumference to the outer circumference in a quadratic function with respect to the distance from the inner circumference, the recording sensitivity increases from the inner circumference to the outer circumference. It is possible to satisfy the required recording sensitivity not only in the inner peripheral portion but also in the outer peripheral portion. In the invention of claim 2, in forming each layer by the sputtering, the shielding member is placed on the outermost peripheral portion of the transparent substrate to form the film.
The film is formed so that the film thickness decreases quadratically from the inner circumference to the outer circumference with respect to the distance from the inner circumference.

[0007]

EXAMPLES The present invention will be described in detail below based on examples. FIG. 1 is a schematic cross-sectional view of a magneto-optical recording medium of one configuration example according to the present invention, and FIG. 2 is a schematic cross-sectional view of a conventional magneto-optical recording medium. In both figures, 1 is a transparent substrate, 2 and 4 are dielectric layers, 3 is a recording layer, and 5 is a reflective layer. In the case of the conventional magneto-optical recording medium of FIG. 2, the film thickness of each layer is uniform on the transparent substrate 1, but the magneto-optical recording medium of the present invention of FIG.
The film thickness of each layer decreases as a quadratic function with respect to the distance from the inner circumference.

In the magneto-optical recording medium having the structure shown in FIG. 1, since the film thickness of each layer decreases as a quadratic function with respect to the distance from the inner circumference, the recording sensitivity increases from the inner circumference to the outer circumference. It is possible to satisfy the required recording sensitivity not only in the peripheral portion but also in the outer peripheral portion. Further, since the composition of the magnetic layer forming the recording layer 3 is the same over the entire surface, it does not affect other recording characteristics. The layer structure in FIG. 1 is merely an example, and the layer structure is not limited to this, and an appropriate layer structure can be adopted. In addition, a structure in which recording layers and the like are provided on both sides of the substrate, or It is also possible to adopt a structure in which a pair of provided substrates are bonded together.

Next, a method of manufacturing the magneto-optical recording medium having the above structure will be described. FIG. 3A is a diagram showing a shielding member placed on the outermost peripheral portion of the transparent substrate when depositing each film by the method of the present invention, and FIG. 3B is a sectional view thereof. In the figure, reference numeral 11 is a transparent substrate, and its material is glass or plastic such as polycarbonate. Reference numeral 12 is a substrate fixing jig, 13 is a shielding member, and 14 is a disk carrier. Substrate fixing jig 1
2. The shielding member 13 can be fixed to the disk carrier 14 during film formation. The shield member 13 is preferably a ring-shaped member that covers the transparent substrate 11 from the outermost peripheral portion to a position 1 mm away, and the height of the shield member 13 is preferably 2 mm or more from the substrate surface, and the material is preferably metal.

In the present invention, when forming each layer on the transparent substrate 11, the transparent substrate 11 is attached to the disk carrier 14.
The transparent substrate 11 is fixed on the outermost peripheral portion of the transparent substrate 11 while being set on the transparent substrate 11 by the substrate fixing jig 12.
Fixedly arranged. By performing the sputtering in this state, each film formed on the transparent substrate 11 has a film thickness that decreases quadratically with respect to the distance from the inner circumference.

Next, an actual manufacturing example will be described. First, Fig. 1
The transparent substrate (diameter 90m
m), a dielectric layer (SiN, thickness 100 nm) is formed on the dielectric layer by a sputtering method, and a recording layer (TbDyFeCo, thickness 6 made of a rare earth-transition metal alloy is formed on the dielectric layer.
30 nm) is sputtered, a dielectric layer (SiN, thickness 40 nm) is sputtered thereon, and a reflection layer (AlTi, thickness 50 nm) is sputtered thereon, and the magneto-optical recording medium according to the present invention is formed. Got

FIG. 4 shows changes in the film thickness of each layer in the radial direction when the film thickness of the inner peripheral portion of each layer of the magneto-optical recording medium thus manufactured is 100. As is clear from this figure, each layer decreases quadratically with the distance from the inner circumference. FIG. 3 shows the change in the recording threshold power of this magneto-optical recording medium in the radial direction. As is clear from this figure, the recording threshold power decreases from the inner circumference to the outer circumference (the recording sensitivity increases from the inner circumference to the outer circumference).

From these facts, when the shielding member is placed on the outermost peripheral portion of the substrate and the film is formed by the sputtering method, the film thickness of each layer, which has not been obtained conventionally, becomes a quadratic function with respect to the distance from the inner circumference. It can be seen that a decreasing magneto-optical recording medium is obtained, and the recording sensitivity increases from the inner circumference to the outer circumference because the film thickness decreases toward the outer circumference.

[0014]

According to the present invention, it is possible to provide a magneto-optical recording medium in which it is not necessary to change the intensity of laser light from the inner circumference to the outer circumference of a disk during recording. Further, according to the present invention, the magneto-optical recording medium having the above characteristics can be easily manufactured by placing the shielding member on the outermost peripheral portion of the disk at the time of sputtering.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a magneto-optical recording medium of one configuration example according to the present invention.

FIG. 2 is a schematic sectional view of a conventional magneto-optical recording medium.

3A is a perspective view showing a shielding member used in the method of the present invention, and FIG. 3B is a sectional view thereof.

FIG. 4 is a diagram showing an average radial change in film thickness of each layer in a manufacturing example according to the present invention.

FIG. 5 is a diagram showing a change in recording threshold power in a radial direction in a manufacturing example according to the present invention.

[Explanation of symbols]

 1 Transparent Substrate 2, 4 Dielectric Layer 3 Recording Layer 5 Reflective Layer 11 Transparent Substrate 12 Substrate Fixing Jig 13 Shielding Member 14 Disk Carrier

Claims (2)

[Claims] 1. A magneto-optical recording medium comprising a transparent substrate and a plurality of layers including at least a recording layer, wherein each of the plurality of layers has a quadratic function with respect to the distance from the inner circumference. A magneto-optical recording medium characterized in that the magneto-optical recording medium is formed so as to be gradually reduced. 2. The method for manufacturing the magneto-optical recording medium according to claim 1, wherein a shielding member is placed on the outermost peripheral portion of the transparent substrate, and each layer is formed by a sputtering method. Recording medium manufacturing method.