JPH06111405A - Production of magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To provide the process for production of the magneto-optical recording medium with which stable high-speed recording and erasing operations are possible even with a device having a small and lightweight electromagnet by increasing CNR under a low magnetic field and improving recording characteristics. CONSTITUTION:A gaseous mixture composed of ozone, oxygen and argon is introduced right to bring the ozone into contact with the surface of a recording layer 4 consisting of an amorphous alloy of a rare earth-transition metal for the prescribed period of time right after this recording layer 4 is formed, by which an oxidized layer 5 is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a magneto-optical recording medium having a recording layer made of a rare earth-transition metal amorphous alloy, and more particularly to a technique for improving recording characteristics under the action of a low external magnetic field. .

[0002]

2. Description of the Related Art Among various optical recording elements, a magneto-optical recording medium capable of recording and erasing information is currently in the stage of practical application. As the recording film of this magneto-optical recording medium,
Those having a thin film of a rare earth-transition metal amorphous alloy are most often used because of their excellent overall characteristics. This recording film is generally constituted by laminating a first dielectric layer, a recording layer, a second dielectric layer, a reflective layer, etc., and the rare earth-transition metal amorphous alloy film is formed on the recording layer. It is used. This recording layer is a vertically magnetized thin film, and when recording or erasing information, writing is performed by distinguishing between 0 and 1 of the binarized signal depending on the change of the magnetization direction (vertical direction) in the vertically magnetized thin film. .

As one of the recording methods for changing the magnetization direction of the recording layer, an optical modulation method has been put into practical use. This is 200 to 300 Oersted (Oe)
Under the action of a relatively strong external magnetic field of, the recording layer is irradiated with a pulsed laser beam having a diameter of about 1 micron, and the irradiated part is heated to the Curie temperature, thereby magnetizing the part. The direction is magnetized in the same direction as the external magnetic field to record signalized information. On the other hand, as another recording method, contrary to the above-mentioned optical modulation method, a magnetic field that applies an external magnetic field and continuously switches (modulates) the direction of the magnetic field while continuously irradiating a laser beam with a constant intensity. A modulation method is known. This system has recently attracted particular attention because it is easy to overwrite a recording medium.

[0004]

By the way, in the above magnetic field modulation method, it is necessary to reverse the direction of the magnetic field at a high speed. For this high-speed magnetic field modulation, a large coil that generates a large external magnetic field is used. Instead, it is better to use a small coil that produces the smallest possible external magnetic field,
The smaller the coil, the smaller the entire device.
Moreover, it can be configured simply. However, since a small intensity of the external magnetic field that can be used deteriorates the signal quality, it is possible to invert the magnetic field of the recording layer with a small external magnetic field intensity in the recording medium. In other words, the magnetic field sensitivity is high. It is necessary to realize the recording layer. Specifically, it is necessary to realize a sufficient signal recording characteristic, for example, a ratio of signal carrier to noise (CNR) of at least 36 dB or more at an external magnetic field strength of −50 to +50 (Oe).

The present invention has been made to solve the above-mentioned problems, and even under the action of a low external magnetic field,
It is an object of the present invention to provide a method for manufacturing a magneto-optical recording medium that can obtain sufficient signal quality.

[0006]

In order to achieve the above object, the invention according to claim 1 provides a first dielectric layer on a substrate,
In a method of manufacturing a magneto-optical recording medium in which a recording layer made of a rare earth-transition metal amorphous alloy and a second dielectric layer are sequentially laminated, the above-mentioned recording layer and the first or second dielectric layer are arranged between the recording layer and the second dielectric layer. The oxidation layer is formed by oxidizing at least the recording layer with a gas containing ozone. According to a second aspect of the present invention, in the method of manufacturing a magneto-optical recording medium according to the first aspect, a substance that is difficult to be oxidized is attached to the surface of the recording layer, and then a gas containing ozone is brought into contact with the surface to oxidize the substance. It forms a layer.

[0007]

By the presence of an oxide layer in the surface layer portion of the recording layer by the above manufacturing method, a recording medium having high recording characteristics sufficient for recording or erasing information even under the action of a small external magnetic field. Can be produced.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below by taking a magneto-optical disk (hereinafter simply referred to as a disk) which is a typical magneto-optical recording medium as an example. FIG. 1 is a sectional view showing the basic structure of a disc. The disk 1 is on the substrate 2,
The first dielectric layer 3, the recording layer 4, which is a perpendicular magnetization film, the oxide layer 5, the second dielectric layer 6, and the reflective layer 7 are sequentially laminated. Of these layers, the layers other than the oxide layer 5 are formed by a known method such as a sputtering film forming method.
The oxide layer 5 is formed after the recording layer 4 is formed and before the second dielectric layer 6 is formed, and details thereof will be described later. The above stacking order is based on the substrate 2 side (upper side in FIG. 1).
Is the case where the laser beam is radiated from the substrate, and contrary to the above, on the substrate 2, the reflective layer, the second dielectric layer, the recording layer, the oxide layer, and the first dielectric layer are arranged in this order. There is also a method of stacking. In the latter case, the laser beam is emitted from the side opposite to the substrate (downward in FIG. 1). When the magneto-optical recording medium is a magneto-optical disk, the former configuration is usually adopted.

In each of the first to fourth embodiments in which the method of forming the oxide layer 5 in the disk 1 is different from each other and the comparative example in which the disk is formed without forming the oxide layer in order to contrast them. The recording characteristics of the disc were measured. In each of the examples and comparative examples, an optical grade polycarbonate is used for the substrate 2, SiN is used for the first dielectric layer 3 and the second dielectric layer 6, and TbFeCoCr is used for the recording layer 4.
The reflective layer 7 uses AlTi as a material, and
A disk 1 was formed by forming a film by sputtering using r and N ₂ gas and stacking the layers as shown in FIG.

The first embodiment will be described. In this embodiment, immediately after the recording layer 4 is formed by sputtering, a mixed gas of ozone, oxygen and argon (O ₂ obtained by corona discharge of oxygen) is obtained.
+ O ₃ is 20%) is introduced into the sputtering chamber,
The oxide layer 5 was formed by bringing ozone into contact with the surface of the recording layer for only a second. After the formation was completed, ozone was discharged to stop the oxidizing action.

FIG. 2 shows the result of measurement of the recording characteristics of the disk according to the first embodiment and the comparative example having the same structure except the oxide layer 5. In the figure, the horizontal axis represents the external magnetic field intensity (unit Oe), and the vertical axis represents CNR (unit dB). As is clear from the figure, the external magnetic field is -50 to +
At 50 (Oe), the disc 1 of the first embodiment exhibits a clearly larger signal recording characteristic, that is, the carrier-noise ratio (CNR) than the comparative example.

A second embodiment will be described. In the present embodiment, in forming the oxide layer 5, immediately after the recording layer 4 is formed by sputtering, the surface of the recording layer 4 is adjusted to have an average thickness of 3 Å by adjusting Cr as a metal which is relatively hard to be oxidized. After the film formation, the same ozone / oxygen / argon mixed gas as in the first embodiment is introduced into the sputtering chamber, the ozone is brought into contact with the surface of the recording layer for 10 seconds to oxidize, and then ozone is discharged to oxidize. Stopped.

FIG. 3 shows the result of measurement of the recording characteristics of the disk according to the comparative example having the same structure except that the second embodiment and the oxide layer 5 were formed. As is clear from the figure, when the external magnetic field is −50 to +50 (Oe), CN of the disk 1 of this example is obviously larger than that of the comparative example.
R is shown.

A third embodiment will be described. In this embodiment, instead of Cr used as the metal that is hard to be oxidized in the second embodiment, Al that is also a metal that is hard to be oxidized is used.
Was sputter-deposited on the surface of the recording layer 4. Other configurations and procedures are the same as those in the second embodiment. FIG. 4 shows the measurement results of the recording characteristics of the disk according to the third example and the comparative example having the same structure except for the oxide layer 5. As is clear from the figure, the external magnetic field is -50 to +
At 50 (Oe), the disc 1 of this example exhibits a significantly higher CNR than the comparative example.

A fourth embodiment will be described. In this example, Au was used as the metal that is difficult to oxidize. The Au film was formed by sputtering so as to have an average thickness of 2 Å. The introduction time of the ozone / oxygen / argon mixed gas was 5 seconds. Other configurations and procedures are the same as those in the second embodiment. This fourth embodiment and oxide layer 5
FIG. 5 shows the result of measurement of the recording characteristics of the disk according to the comparative example having the same structure except the above. As is apparent from the figure, the external magnetic field is −50 to + also in this embodiment.
At 50 (Oe), the disc 1 according to this example exhibits a significantly higher CNR than the comparative example.

As can be seen from the above-mentioned first to fourth embodiments, by forming an oxide layer on the surface of the recording layer,
Under the action of an external magnetic field as low as −50 to +50 (Oe), the signal recording characteristics can be improved. The present invention is
The present invention is not limited to the configuration of the above embodiment, and various modifications are possible. For example, when forming a disk, the substrate 2 may be a transparent plastic such as an epoxy resin or a polyolefin resin, or an optically transparent material such as transparent glass, in addition to the polycarbonate. In addition, the first dielectric layer 3 and the second dielectric layer 6
In addition to the above SiN, AlSiON, SiO or the like can be used as a material. The recording layer 4 is composed of Tb, Fe,
The rare earth-transition metal amorphous alloy may be composed of those containing elements such as Co, Cr and Ti. Reflective layer 7
Can be formed of not only AlTi but also an alloy of Al as a main component with addition of Cr or the like, aluminum, platinum, or the like, and the reflective layer 7 may not be formed. In the above embodiments, the magneto-optical disk is taken as an example, but the present invention is not limited to this, and can be widely applied to other magneto-optical recording media.

[0017]

As described above, according to the present invention, the signal recording characteristic (CNR) under the action of a low external magnetic field (for example, -50 to +50 Oersted) becomes larger than that of the conventional magneto-optical recording medium, A magneto-optical recording medium suitable for the magnetic field modulation method can be provided. Furthermore, in an apparatus using the recording medium manufactured by the manufacturing method of the present invention,
Since it is not necessary to provide a large-sized magnetic field generator, the device can be downsized and the cost can be reduced. Also, high-speed magnetic field modulation is possible, and the recording operation time can be shortened.

[Brief description of drawings]

FIG. 1 is a sectional view showing a basic structure of a magneto-optical recording medium according to an embodiment of the present invention.

FIG. 2 is a diagram showing measurement results of signal recording characteristics of magneto-optical recording media according to the first example and its comparative example.

FIG. 3 is a diagram showing measurement results of signal recording characteristics of magneto-optical recording media according to a second example and its comparative example.

FIG. 4 is a diagram showing measurement results of signal recording characteristics of magneto-optical recording media according to a third example and its comparative example.

FIG. 5 is a diagram showing measurement results of signal recording characteristics of magneto-optical recording media according to a fourth example and its comparative example.

[Description of Reference Signs] 1 magneto-optical disk 2 substrate 3 first dielectric layer 4 recording layer 5 oxide layer 6 second dielectric layer 7 reflective layer

Claims (2)

[Claims] 1. A method for manufacturing a magneto-optical recording medium, which comprises sequentially laminating a first dielectric layer, a recording layer made of a rare earth-transition metal amorphous alloy, and a second dielectric layer on a substrate. A method for manufacturing a magneto-optical recording medium, characterized in that an oxide layer formed by oxidizing the recording layer with a gas containing at least ozone is formed between the first and second dielectric layers. 2. The magneto-optical recording according to claim 1, wherein a substance that is not easily oxidized is attached to the surface of the recording layer, and then a gas containing ozone is brought into contact with the surface to form the oxide layer. Medium manufacturing method.