JPH05290420A - Magneto-optical disk and its recording and reproducing method and device - Google Patents

Abstract

PURPOSE:To improve the recording density of the magneto-optical disk which records, reproduces and erases of information by using a laser beam and an externally impressed magnetic field and to improve handleability. CONSTITUTION:An information recording film 3 consists of a magnetic material having perpendicular magnetic anisotropy and exhibiting a magneto-optical effect and consists of a ROM region where the information is previously recorded non-volatizably and a RAM region where a user rewritably records the information. The information is recorded by changing the direction of the axis of easy magnetization in parallel with the recording film plane and the information is reproduced by detecting the difference in the magneto-optical effect by the difference in the direction in the ROM region. The information is recorded by inverting the directions of magnetization and the information is reproduced by detecting the difference in the magneto-optical effect by the difference in the forward and backward directions of the magnetization; for example, the difference in the rotating directions of the plane of polarization in the RAM region.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical disk for recording / reproducing / erasing by using a laser beam and an externally applied magnetic field, and a recording / reproducing method and apparatus therefor. To improve the.

[0002]

2. Description of the Related Art With the progress of advanced information society in recent years, there is an increasing need for a high-density and large-capacity file memory. Among them, optical recording has been attracting attention as a memory to meet this demand. Optical recording includes various types such as a read-only type represented by a laser disc and a compact disc, a write-once type capable of recording information only once, and a rewritable type capable of rewriting many times. These various types of optical recording are used for applications that make the most of their characteristics. Among them, magneto-optical recording has recently been put into practical use as rewritable optical recording. At present, development is being advanced by many research institutions in order to improve the performance of magneto-optical recording. One of these development goals is to further improve the recording density and make the system more user-friendly. Among them, in order to realize high-density recording, it is most promising to use laser light having a short wavelength for recording and reproduction. As a publicly known example in this respect, there is JP-A-1-251356.

[0003]

In the above-mentioned prior art, as a method for realizing high-density optical recording, 1) a recording material is selected, 2) the recording density is improved by reducing the track pitch, and 3) a pit. Use edge recording method,
It has been shown that high density recording can be realized by such means.
However, there is a limit in improving the recording density by a physical method such as reducing the track pitch. Moreover, the usability of the optical disk cannot be improved.

It is an object of the present invention to provide a magneto-optical disk which enables ultra-high density optical recording and is easy to use, and a recording / reproducing method and apparatus thereof.

[0005]

According to the present invention, in order to achieve the above object, in a magneto-optical disk for recording / reproducing digital information using a laser beam and a magnetic field, the information recording film has a perpendicular magnetic anisotropic layer. Of the information recording film, which is composed of a magnetic material having a magnetic property and having a magneto-optical effect, and has a ROM area in which information is recorded in advance and a RAM area in which information can be rewritten by a user. A magneto-optical disk that records and reproduces information by changing magnetic characteristics and magneto-optical characteristics.

In particular, in the recording / reproducing of information due to the change of the magnetic characteristic and the difference of the magneto-optical characteristic, in the ROM area, the direction of the easy axis of magnetization at the recording bit position is changed from the direction perpendicular to the recording film surface to the parallel direction. The information is recorded by changing it, and the information is reproduced by detecting the presence or absence of rotation of the polarization plane caused by the magneto-optical effect due to the difference in the direction of the easy axis of magnetization. The information is recorded by changing the direction of the magnetic field in the opposite direction, and the information is reproduced by detecting the difference in the rotation direction of the polarization plane caused by the magneto-optical effect due to the difference in the direction of this magnetization. To do.

The magneto-optical disk and the information recording / reproducing method thereof according to the present invention will be described more specifically.
First, an object of the present invention to provide a user-friendly magneto-optical disk is that the optical recording medium is a rewritable R recorded by a user.
This is achieved by comprising two parts, an AM area and a non-rewritable ROM area in which predetermined information is recorded in advance. When information is recorded by using a magnetic material having a perpendicular magnetic anisotropy and a magneto-optical effect as a recording material, recording is performed by reversing the direction of the easy axis of magnetization in the RAM area (the direction of the easy axis of magnetization is the substrate. On the other hand, vertically upward or downward, the N pole of the magnet records upward or downward), and reproduction is performed by magneto-optical properties such as Kerr effect and Faradey effect. That is, it is performed by detecting the difference in the direction of rotation of the polarization plane. In addition, in the ROM area, recording is performed by using the alteration of magnetic characteristics due to thermal action, and reproduction is performed by detecting a difference in magneto-optical properties such as Kerr effect and Faradey effect. That is, recording is performed by changing the direction of the easy axis of magnetization from the direction perpendicular to the recording film surface to the parallel direction as a change in magnetic characteristics, and providing a portion having perpendicular magnetic anisotropy and an in-plane magnetized film portion. , The difference in the magneto-optical effects of the two parts, namely Ke
Plays depending on whether the rr effect or Faradey effect is present. As a method of changing the easy axis of magnetization, energy may be irradiated to a desired recording bit position of a magnetic material having perpendicular magnetic anisotropy, and atoms of the irradiated portion may be rearranged. The resulting change in magnetic properties is a change in perpendicular magnetic anisotropy energy. The information recorded in this way cannot be rewritten. Also, as the information to be recorded in advance, disk control information, system information,
There is software information. What is disk control information?
It refers to clock information used for reproduction, address information indicating a position where the information is recorded, information indicating a defective position of the disc, information about a type of the disc and conditions necessary for recording and reproduction. The system information is information about a system such as a computer or a personal computer. The software information is information about music, games, various information processings, and the like.

[0008]

The information recording film of the magneto-optical disk is composed of a RAM area in which the user can rewrite and a ROM area in which disk control information, system information and the like are previously recorded in a non-volatile manner. Therefore, the usability of the disc is improved. In particular, the effect is further enhanced by recording repeatedly used software information in the ROM area. Next, regarding the recording density of information, since the conventional optical disc is a method using physically formed pits and depressions, it is necessary to physically adjust the size so that it can be packed in both the interval between pit tracks and the interval between recording bits. However, the present invention employs a magnetic material having perpendicular magnetic anisotropy and a magneto-optical effect as an information recording film, and changes the magnetic characteristics of the recording film to record information. Therefore, it becomes possible to form a recording bit with a fine dimension beyond the limit of the conventional method, and the purpose of high density recording can be achieved. Particularly, in the information recording in the ROM area, the recording bit position is irradiated with energy, the atoms in the irradiated portion are rearranged, and the direction of the easy axis of magnetization is parallel to the recording surface. It is possible to use a short laser beam, an electron beam or an X-ray, and it is possible to realize information recording at an ultrahigh density.

[0009]

【Example】

Example 1 FIG. 1 is a schematic view showing the cross-sectional structure of the optical disc manufactured in this example. The disks were manufactured by continuously stacking them by a sputtering method without breaking the vacuum. A silicon nitride layer 2 having a film thickness of 650Å was formed on a flat disk substrate 1 which is transparent to a laser beam used for recording and reproduction. This film thickness is changed according to the laser beam used for reproduction. This film causes a large amount of interference by the reproduction light, and the magneto-optical effect is enhanced. Pure Si was used as the target, and Ar / N ₂ (= 90/10) was used as the discharge gas. The gas pressure at the time of discharge was 10 mTorr, and the sputtering was performed at an input power density of 6.6 W / cm ² . Next, as the information recording layer 3, the target was adjusted so that the film composition was Tb ₂₄ Fe ₅₇ Co ₁₆ Nb _3, and the film was formed to a film thickness of 250 Å. Sputtering was performed using a TbFeCoNb alloy as a target and pure Ar as a discharge gas. Sputtering was performed at a discharge gas pressure of 5 mTorr and an input RF power density of 4.2 W / cm ² . Again, the silicon nitride layer 4 was formed to a film thickness of 650Å. The manufacturing conditions are the same as those of the silicon nitride layer 2 described above. Then, finally, the target is adjusted so that the film composition of the metal reflection film 5 is Al ₇₀ Ti _30, and 30
It was formed to a film thickness of 0Å. Sputtering was performed using an AlTi alloy as the target and pure Ar as the discharge gas. The gas pressure during discharge was 15 mTorr, and the input RF power density was 3.2 W / cm ² .

ROM of disk manufactured in this way
Guide tracks for positioning header signals such as clock signals and reference signals and information are formed in the regions.
That is, the recording film is irradiated with He—Ne laser light with a power of 15 mW, and the direction of the easy axis of magnetization of this irradiation portion is changed from the direction perpendicular to the recording film surface to the parallel direction. At that time, the magneto-optical effect (the Kerr effect and the Fa
Controls the recording position of information on the disc while detecting the difference (using both radey effects). In addition to this, as the information to be recorded in the ROM area, system information of the personal computer and the like are recorded in advance. These pieces of information may be recorded for each sector, or may be recorded in a fixed area such as the inner circumference or the inner circumference of the disc. The user can improve the usability by recording the program and various data created by the user in the RAM area of the disk.
When the information recorded in these ROM area and RAM area was reproduced, it could be reproduced without error. Further, the system can be controlled by the system information recorded in the ROM area, data can be exchanged, and the data created by the user in the RAM area can be saved, thus improving the usability. Of course this R
The information in the AM area can be rewritten. The information in the ROM area can be reproduced by detecting the difference between the Kerr effect and the Faradey effect. In order to detect the magneto-optical effect, information was reproduced by irradiating the recording film with linearly polarized laser light and detecting whether or not the plane of polarization of the reflected light was rotated. In this case, it is possible to perform higher density recording by shortening the interval between the guide tracks, using a laser beam having a short wavelength, further shortening the recording bit interval, or performing bit edge recording. It goes without saying that the recording density is further increased by combining these methods.

The effect of the present invention does not depend on the structure of the magneto-optical disk, the material of each layer used, the starting device, the wavelength of laser light, and the like. The materials and structures used are examples, and the effects of the present invention are not affected by these.

Example 2 FIG. 2 is a schematic view showing the cross-sectional structure of the optical disk manufactured in this example. Here, it is a case of a disc in which guide tracks and disc control information are recorded on the recording film in the ROM area. The disk was manufactured by the method described below. That is, a plastic or glass substrate was used, and three layers of the silicon nitride layer 2, the information recording layer 3, and again the silicon nitride layer 4 were continuously laminated on the substrate 1. The sputtering conditions at that time were 750 for each film thickness.
The procedure is the same as that of the first embodiment except that Å, 1000 Å and 1000 Å are used.

A guide track is formed by irradiating the thus-produced disk with a high-power laser beam to reduce the magnetic characteristics of a part of the magnetic film of the recording film, particularly the perpendicular magnetic anisotropy energy. did. With that,
System information was recorded in advance by a similar method. This optical disk drive was connected to a personal computer. Then, when the computer was started up, the system information could be loaded from the optical disc and started up. this is,
This indicates that the information recorded in the ROM area can be reproduced without error. Here, the information may be recorded at a predetermined position on the disc or may be recorded for each sector.
In addition, the ruled lines of the tabulation table are recorded in advance, and the user additionally records the data on the ruled lines, whereby the usability can be further improved.

Third Embodiment FIG. 3 is a block diagram of a magneto-optical disk recording / reproducing apparatus as a third embodiment of the present invention. In FIG. 3, 11 is a magneto-optical disk, 12 is a disk holder, and 13 is a drive motor which is a rotational drive source of the disk. Since the present embodiment shows a recording / reproducing apparatus used by a user, the ROM area of the magneto-optical disk 11 has already recorded disk control information, system information, software information and the like.
A recording / reproducing system 14 is composed of a focusing lens 14a, a mirror 14b, and a half mirror 14c. 1
Reference numeral 5 is a laser source, and 16 is a polarizing plate. 17 is a detection system,
It is composed of a cylindrical lens 17a, an analyzer 17b, a photodiode 17c for detecting a control signal, and a photodiode 17d for detecting a magneto-optical effect. Reference numeral 18 is an electromagnet for forming an externally applied magnetic field when the user records information in the RAM area. Reference numeral 17 is a control signal generating circuit for sending control signals to the recording / reproducing system 14, the laser source 15, and the electromagnet 18. ..

With the recording / reproducing apparatus having such a structure, information can be recorded in the RAM area by reversing the direction of magnetization of the recording bit position by the electromagnet 18, and the ROM area and The reproduction of information recorded in the RAM area can be performed by detecting the difference in magneto-optical effect at the recording bit position with the photodiode 17d.

[0016]

According to the present invention, the usability of the optical disk can be improved and high density recording can be realized, whereby the use of the optical disk can be further expanded.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a sectional structure of a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a cross-sectional structure of a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a magneto-optical disk device showing a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Disk substrate 2, 4 ... Silicon nitride layer 3 ... Information recording film 5 ... Metal reflective film 11 ... Magneto-optical disk 12 ... Disk holder 13 ... Drive motor 14 ... Recording / reproducing system 15 ... Laser source 16 ... Polarizing plate 17 ... Detection system 18 ... Electromagnet 19 ... Control signal generation circuit

Claims (12)

[Claims] 1. A magneto-optical disk for recording / reproducing digital information using a laser beam and a magnetic field, wherein an information recording film is formed of a magnetic material having perpendicular magnetic anisotropy and exhibiting a magneto-optical effect, and It is composed of two areas, a ROM area in which information is recorded in advance and a RAM area in which information can be rewritten by a user. Information is recorded and reproduced by a change in magnetic characteristics and a difference in magneto-optical characteristics of the information recording film. A magneto-optical disk characterized by being performed. 2. A ROM in the information recording film according to claim 1.
A magneto-optical disk characterized in that information is recorded in an area by changing perpendicular magnetic anisotropy energy at a recording bit position. 3. The information recording in the ROM area of the information recording film according to claim 1 or 2, wherein a recording bit position is irradiated with a laser beam, and a direction of an easy axis of magnetization in this irradiation portion is set with respect to a recording film surface. A magneto-optical disk characterized by being changed from a vertical direction to a parallel direction. 4. The information recording in the ROM area of the information recording film according to claim 1 or 2, wherein the direction of the easy axis of magnetization is changed by irradiating the recording bit position with energy and rearranging the atoms of the irradiated portion. A magneto-optical disk characterized by being changed from a direction perpendicular to a recording film surface to a direction parallel thereto. 5. The ROM in the information recording film according to claim 1.
The magneto-optical disk is characterized in that the area and the RAM area are set for each sector of the disk or at a fixed position in the inner peripheral part, the middle peripheral part or the outer peripheral part of the disk. 6. The ROM in the information recording film according to claim 1.
The magneto-optical disk characterized in that the information recorded in the area is any one of disk control information, system information, software information, or a combination thereof. 7. The information to the ROM area obtained by changing the direction of the easy axis of magnetization according to claim 3 or 4 from a direction perpendicular to the recording film surface to a positioning formed in the ROM area. A magneto-optical disk characterized by being recorded along a guide track for use. 8. A magneto-optical disk according to claim 7, wherein the guide track is formed concentrically or spirally with respect to the center of the disk. 9. The positioning of the information recorded in the ROM area according to claim 7 or 8, the difference in the magneto-optical effect caused by the difference in the direction of the easy axis of magnetization is perpendicular or parallel to the recording film surface. A magneto-optical disk characterized by being detected. 10. The method for recording / reproducing information on / from a magneto-optical disk according to claim 1, wherein the direction of the easy axis of magnetization of the recording bit position is parallel to the recording film surface in the ROM area. A recording / reproducing method for a magneto-optical disk, which is characterized in that recording is performed and information is reproduced by detecting the presence or absence of rotation of the polarization plane caused by the magneto-optical effect due to the difference in the direction of the easy axis of magnetization. 11. A method for recording / reproducing information on / from a magneto-optical disk according to claim 1, wherein information is recorded by changing the magnetization direction of a recording bit position in the RAM area in the opposite direction. A recording / reproducing method for a magneto-optical disk, characterized in that information is reproduced by detecting a difference in a rotation direction of a polarization plane caused by a magneto-optical effect due to a difference in direction. 12. A magneto-optical disk (11) according to claim 1, and a rotary drive system (12, 13) thereof.
A laser source (15), a recording / reproducing system (14) for narrowing and irradiating a laser beam after passing through a polarizing plate (16) as a spot to a predetermined position on the disc, and the recording / reproducing system reflecting the disc again. A detection system (17) that detects the difference in the magneto-optical effect at the spot irradiation position by detecting the light that has passed through the system (14), and a magnetic field applying means (18) for the user to record information in the RAM area. ) And a control signal generating means (19) for producing and outputting a control signal to the recording / reproducing system (14) and the magnetic field applying means (18).