JPH0855376A - Magneto-optical disk cartridge - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a compact and low-cost magneto-optical disk cartridge capable of overwriting optical modulation. A cartridge is equipped with two magnets each having a yoke on its magnetic pole so that magnetic lines of force inside the magnet are parallel to the disk surface and opposite magnetic poles face each other across the disk.

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 cartridge.

[0002]

2. Description of the Related Art Magneto-optical disks have been developed and put into practical use as information recording media capable of repetitive recording and reproduction. Recording is performed on this magneto-optical disk by irradiating the disk surface with a focused laser beam, thereby applying a recording magnetic field while heating the medium, and reversing the magnetization of the heated portion. To reproduce the recorded information, the focused laser beam is linearly polarized and irradiated on the disk surface, and the polarization direction of the reflected light changes by the Kerr effect according to the magnetization direction of the medium. To do. Furthermore, in order to erase the recorded information, irradiate a focused laser beam on the disk surface, thereby heating the medium and applying a magnetic field in the direction opposite to that at the time of recording to return the direction of the magnetic field to the original direction. Is going by.

Therefore, when rewriting information that has been recorded once, it is necessary to erase the data once and then record new information, which makes the rewriting time longer than that of a hard disk by the time required for the erasing. There was a drawback. In order to overcome such drawbacks, various techniques of a recording method that does not require an erasing operation, so-called overwriting, have been proposed. Among them, JP-A-62-175948 proposes a method of using an exchange-coupled multilayer magnetic film as a recording medium and using an initialization magnetic field in addition to the conventional bias magnetic field. This method has a memory layer and a recording layer both of which are perpendicularly magnetizable and exchange-coupled to each other, and at room temperature, the magnetization direction of the memory layer is not changed but only the magnetization direction of the recording layer is changed to a predetermined direction. It uses a recording medium that can be stored in.

To explain this method in more detail, the magnetization direction of the recording layer of the recording medium is aligned in one direction perpendicular to the disk surface by the initialization means before recording. This action is referred to as "initialization" in this specification. This "initialization" is a process peculiar to overwrite. The medium which has been “initialized” is irradiated with a laser beam pulse-modulated according to the binary information to be recorded. At this time, new information is overwritten while modulating the laser beam intensity into three levels of a recording level, a reproduction level and an erasing level. The memory layer has a relatively higher coercive force at room temperature than the recording layer,
The magnetization reversal temperature is relatively low, and conversely, the recording layer has a relatively small coercive force at room temperature and a relatively high magnetization reversal temperature as compared with the memory layer. The memory layer and the recording layer may themselves be composed of a multilayer film. In some cases, an intermediate layer for adjusting the exchange coupling force of both layers may be present between the memory layer and the recording layer. Also, the C /
In order to increase the N value, there is also proposed a structure in which a reading layer having a higher Curie point and a higher Kerr effect is laminated on the laser beam incident side of the memory layer.

The initialization means is required to be able to generate a fairly strong magnetic field of 1 to 6 kOe. However, if an initialization magnet that generates such a strong magnetic field is placed inside the magneto-optical recording device, there is a problem that the device cannot be downsized. Further, there is a problem that it hinders recording / reproduction of a disc that does not require an initialization magnetic field such as non-overwrite.

Therefore, in consideration of compatibility with conventional discs, a method of incorporating this initialization magnet into a magneto-optical disc cartridge has been proposed in Japanese Patent Laid-Open No. 64-46247. This method has the advantages that it is not necessary to incorporate an initializing magnet in the magneto-optical disk recording apparatus, the recording apparatus can be miniaturized, and recording and reproducing of a disk that does not require an initializing magnetic field can be performed without any problem.

[0007]

However, the method proposed so far as the means for incorporating the initialization magnet in the magneto-optical disk cartridge is as shown in FIG.
The magnetic field was applied by arranging one (one set) of magnets so that the magnetic lines of force inside the magnet were perpendicular to the disk surface, with the disk sandwiched. Therefore, a large magnetic circuit (yoke) is required to recirculate the magnetic flux to the magnet on the opposite side, resulting in a problem that the cartridge becomes large and the cost becomes high. Further, since the direction of the magnetic flux is only in one direction with respect to the disc, two sets of magnets are required for a magneto-optical disc cartridge of the type that records and reproduces from both sides, which further increases the size and cost. there were.

[0008]

In order to solve such a problem, the inventors of the present invention have conducted intensive studies and found that a magnet having a yoke on a magnetic pole has a magnetic field line parallel to the disk surface. The present invention has been completed by finding that the cartridge can be small in size and low in cost by providing two cartridges so that opposite magnetic poles face each other with the disc sandwiched therebetween.

Therefore, according to the present invention, firstly, in a magneto-optical disk cartridge for storing a magneto-optical disk capable of overwriting by at least optical modulation, a permanent magnet and a yoke covering a magnetic pole surface of the permanent magnet are used. A magnet-optical disk cartridge, in which two magnets are provided so that the opposite magnetic poles face each other with the magneto-optical disk sandwiched therebetween, and a magnetic field applying means is configured by the two magnets. 2. The magneto-optical disk cartridge according to claim 1, wherein "the yoke is a U-shape that covers the surface of the permanent magnet on the opposite side when viewed from the magneto-optical disk". "The distance between the tip of the yoke and the magneto-optical disk is smaller than the distance between the permanent magnet surface facing the magneto-optical disk and the magneto-optical disk. Fourthly, "the magneto-optical disk cartridge described above is provided, and fourthly, the cross-sectional area of the yoke at one magnetic pole portion is smaller than the cross-sectional area of the yoke at the other magnetic pole, and two magnet parts sandwich the magneto-optical disk. The magneto-optical disk cartridge according to claim 1, wherein a magnetic pole having a large cross-sectional area of the yoke and a magnetic pole having a small cross-sectional area of the yoke face each other. 5. The magnetic centers of the yokes of the magnetic poles of the two magnets facing each other are aligned.
And a magneto-optical disk cartridge according to claim 6,
According to claim 4, "The distance between the magneto-optical disk and one magnet portion is smaller than the distance between the other magnet portion.
The magneto-optical disk cartridge described in "7.
To "a magneto-optical disk cartridge according to claim 1, wherein the cross-sectional area of the yoke of one magnet portion is smaller than the cross-sectional area of the yoke of the other magnet portion".
Eighth, "The distance between the magneto-optical disk and the permanent magnet surface of the magnet portion having the smaller yoke cross-sectional area faces the magneto-optical disk of the magnet portion having the larger yoke cross-sectional area. The magneto-optical disk cartridge according to claim 7, characterized in that it is smaller than the distance between the permanent magnet surface and the magneto-optical disk.

[0010]

FIG. 6 is a conceptual diagram showing the magneto-optical disk cartridge of the embodiment of the present invention. The magneto-optical disk cartridge of the present invention includes a magneto-optical disk 11, a rectangular cartridge portion 12 that rotatably holds and stores the magneto-optical disk,
An opening 13 provided to bring an optical head for recording / reproducing information closer to the disk, a shutter section 14 for blocking the opening when unnecessary, and a magnetic field applying means 15 for applying an initializing magnetic field to the magneto-optical disk. Consists of.

The magneto-optical disk has an overwritable multilayer magnetic layer protected by a protective film on a transparent substrate. The magnetic layer is composed of at least two layers: a memory layer having perpendicular magnetic anisotropy and holding recorded information, and a recording layer also having perpendicular magnetic anisotropy and peculiar to the overwrite function. Initialization is performed in one direction by the magnetic field applying means including the two magnet portions 15.

The magneto-optical disk has a hub at its center. At the time of recording / reproducing, by connecting the hub to the disk rotating means of the recording / reproducing apparatus, the rotating force of the rotating means is transmitted to the disk to rotate the magneto-optical disk 11. At the same time, the shutter unit 14 is opened and the magneto-optical disk 11 is irradiated with the laser beam condensed from the opening 13 for recording and reproduction.

FIG. 1 is an enlarged conceptual view of a portion of a magnetic field applying means of a magneto-optical disk cartridge according to claim 1 of the present invention, and corresponds to a cross section taken along the line AA of FIG. The magnetic field applying means is composed of two magnet parts, and the magnet parts face each other with the magneto-optical disk interposed therebetween. The magnet portion includes a permanent magnet 22 and a yoke 23 having high magnetic permeability. The permanent magnet 22 is arranged parallel to the substrate surface of the magneto-optical disk 21. Permanent magnet 22
As the material of (1), it is desirable that both the residual magnetic flux density and the coercive force are large, and examples of such a material include NdFeCo which is a rare earth-transition metal alloy. The yoke 23 covers both sides of the magnetic poles of the permanent magnet 22. As a material of the yoke, low carbon steel having high magnetic permeability, silicon steel or the like is used. The magnetic poles of the magnet portion are arranged to face different magnetic poles to form a magnetic circuit.

With this configuration, the permanent magnet of one magnet portion is
The magnetic flux emitted from one of the magnetic poles of 22 is concentrated on the yoke 23 and is further focused on the yoke of the magnet portion which passes through the magneto-optical disk 21 and faces each other. Also, the magnetic flux emitted from the other magnetic pole is
The magneto-optical disk 21 is penetrated from the yoke in the opposite direction, and is focused and returned to the yoke of the magnetic pole of the magnet portion on the opposite side. Therefore, since the magnetic circuit is formed only by the magnetic field applying means, it is not necessary to provide a large magnetic circuit (yoke) for returning the magnetic flux to the magnet on the opposite side as in the conventional case.

FIG. 2 is an enlarged conceptual view of the magnetic field applying means of the magneto-optical disk cartridge according to claim 2 of the present invention. The yoke portion 23 covers the disk of the permanent magnet 22, the surface on the opposite side, and the magnetic pole surfaces on both sides. The magnetic flux from one magnetic pole of one permanent magnet 22 is concentrated on the yoke 23,
A part of it returns to the other magnetic pole through the inside of the yoke. The rest of the magnetic flux is from the yoke to the magneto-optical disk.
It is focused on the yoke of the magnet part that passes through 21 and faces each other. Similarly, the magnetic flux emitted from the other magnetic pole passes through the magneto-optical disk 21 from the yoke portion in the opposite direction and is converged and recirculated to the yoke portion of the magnetic pole of the magnet portion on the opposite side.

1 and 2, when passing through the magnetic field applying means, the magneto-optical disk 11 is affected by magnetic fields penetrating the magneto-optical disk 11 in opposite directions, one by one. As a result, the magnetization of the recording layer of the disc is initialized in the direction of the magnetic field, with the influence of the magnetic field that passes later remaining after the two magnetic fields pass. That is, if the rotation directions are different, the initialization directions are opposite.

By the way, in the case of a double-sided type magneto-optical disk capable of recording / reproducing on both sides, the disk rotation direction and the initialization direction viewed from the optical head must be the same on both surfaces. Therefore, since the cartridge insertion surface is opposite between the front surface and the back surface, it is necessary that the relative rotation direction and the initialization direction of the disk viewed from the cartridge are opposite. For this reason, as shown in FIG. 7, the conventional magneto-optical disk cartridge requires two magnetic field applying means.

However, according to the present invention, even if one magnetic field applying means has different rotation directions, the initialization directions are automatically reversed so that both surfaces can be initialized. In the magnet portion 15, it is preferable that the tip of the yoke of the magnetic pole portion is closer to the magneto-optical disk than the end surface of the permanent magnet, because the magnetic flux is more focused on the magneto-optical disk between the facing yokes.

Further, as shown in FIG. 3, the cross-sectional area of one yoke is made smaller than the cross-sectional area of the other yoke, so that the two magnet portions sandwich the magneto-optical disk and the magnetic pole having a large cross-sectional area of the yoke. When the magnetic poles with a small cross-sectional area of the yoke are opposed to each other, the magnetic flux emitted from the yoke with a large cross-sectional area is concentrated on the yoke with a small cross-sectional area, which increases the magnetic field strength in the magneto-optical disk, which is preferable. Changing the width of the yoke is the easiest way to change the cross-sectional area of the yoke. Further, in this case, it is more preferable to align the magnetic centers of the yoke having a small cross-sectional area and the large yoke so that the magnetic flux efficiently flows from the yoke to the yoke.

Further, as shown in FIG. 4, in the magnetic field applying means, the cross-sectional area of the yoke covering the magnetic pole surface of the permanent magnet of one of the magnet portions and the yoke covering the magnetic pole surface of the permanent magnet of the other magnet portion. If the cross-sectional area is smaller than the cross-sectional area, the magnetic flux concentrates on the yoke having a small cross-sectional area, and the magnetic field strength on the magneto-optical disk increases, which is preferable. Further, as shown in FIG. 5, when the distance between one of the pair of magnets of the magnetic field applying means facing each other across the magneto-optical disk is smaller than the distance between the other and the disk, the cross-sectional area is reduced. Since the magneto-optical disk is close to the small yoke, a larger magnetic field intensity can be obtained on the magneto-optical disk, which is preferable.

Since the magnetic field applying means of the present invention only needs to apply a magnetic field capable of initializing the recording layer of the magneto-optical disk, there is no restriction on the installation location in the cartridge. Therefore, it may be near the opening of the cartridge or on the opposite side of the opening. Further, the appearance of the cartridge of the present invention can be exactly the same as that of the conventional ISO standard product.

Examples of the present invention will be described below, but the present invention is not limited thereto.

[0023]

EXAMPLE A magneto-optical disk having a diameter of 130 mm and capable of optical modulation overwriting, and a magneto-optical disk cartridge having the magnetic field applying means shown in FIGS. 1 and 2 were prepared. These two
A kind of cartridge was set in a recording / reproducing apparatus, first a first recording signal was recorded, and first, a second recording signal having a frequency different from that of the recording signal was overwritten. After that, when reproduction was performed and the C / N value of the reproduction signal was measured, it was confirmed that the C / N value was not less than a predetermined value, and that the overwriting was normally performed.

[0024]

As described above, according to the present invention, it is possible to provide a small size and low cost cartridge for an overwrite magneto-optical disk. Further, this eliminates the need for the initialization magnetic field applying means in the disc recording device, so that the disc recording device can be downsized and the cost of the recording device can be reduced. Furthermore, compatibility with a conventional disk cartridge that does not require an initializing magnetic field can be obtained.

[Brief description of drawings]

FIG. 1 is an enlarged conceptual view of a magnetic field applying unit of a magneto-optical disk cartridge according to claim 1 of the present invention.

FIG. 2 is an enlarged conceptual view of a magnetic field applying unit of a magneto-optical disk cartridge according to claim 2 of the present invention.

FIG. 3 is an enlarged conceptual view of a magnetic field applying unit of a magneto-optical disk cartridge according to claim 4 of the present invention.

FIG. 4 is an enlarged conceptual view of a magnetic field applying means of a magneto-optical disk cartridge according to claim 7 of the present invention.

FIG. 5 is an enlarged conceptual view of a magnetic field applying unit of a magneto-optical disk cartridge according to claim 8 of the present invention.

FIG. 6 is a conceptual diagram showing a magneto-optical disk cartridge of an embodiment of the present invention.

FIG. 7 is an enlarged conceptual view of a magnetic field applying unit of a conventional magneto-optical disk cartridge.

[Explanation of symbols]

 11 ... Magneto-optical disk 12 ... Cartridge part 13 ... Cartridge opening part 14 ... Shutter part 15 ... Magnet part 21 ... Magneto-optical disk 22 ... Permanent magnet 23 ... Yoke that's all

Claims (8)

[Claims] 1. A magneto-optical disk cartridge for storing a magneto-optical disk capable of overwriting by light modulation, wherein a magnet portion composed of a permanent magnet and a yoke covering a magnetic pole surface of the permanent magnet is opposed to each other. Two magnets are placed so that the magnetic poles face each other with the magneto-optical disk sandwiched therebetween.
A magneto-optical disk cartridge comprising a plurality of magnetic field applying means. 2. The magneto-optical disk cartridge according to claim 1, wherein the yoke is a U-shape that covers the surface of the permanent magnet on the opposite side when viewed from the magneto-optical disk. 3. The magneto-optical disk according to claim 1, wherein the distance between the tip of the yoke and the magneto-optical disk is smaller than the distance between the magneto-optical disk and the permanent magnet surface facing the magneto-optical disk. Disk cartridge. 4. The cross-sectional area of the yoke in one magnetic pole portion is smaller than the cross-sectional area of the yoke in the other magnetic pole.
2. The magneto-optical disk cartridge according to claim 1, wherein each of the magnet portions faces a magnetic pole having a large cross-sectional area of the yoke and a magnetic pole having a small cross-sectional area of the yoke so as to sandwich the magneto-optical disk. 5. The magneto-optical disk cartridge according to claim 4, wherein the magnetic centers of the yokes of the magnetic poles of the two magnet portions facing each other with the magneto-optical disk interposed therebetween are aligned. 6. The magneto-optical disk cartridge according to claim 4, wherein a distance between the magneto-optical disk and one magnet portion is smaller than a distance between the other magnet portion. 7. The magneto-optical disk cartridge according to claim 1, wherein the yoke of one magnet portion has a smaller cross-sectional area than the yoke of the other magnet portion. 8. The magneto-optical disk of the magnet part having the larger yoke cross-sectional area is located at a distance between the magneto-optical disk and the permanent magnet surface of the magnet part of the smaller yoke cross-sectional area facing the magneto-optical disk. 8. The magneto-optical disk cartridge according to claim 7, wherein the magneto-optical disk cartridge is smaller than the distance between the opposing permanent magnet surfaces and the magneto-optical disk.