JPH07334959A - Magneto-optical disk cartridge - Google Patents

Abstract

PURPOSE:To decrease the number of magnets to one piece and to reduce the size and cost of a magneto-optical disk cartridge by providing the cartridge with a yoke covering the magnetic pole surface of a permanent magnet placed in parallel with a magneto-optical disk surface. CONSTITUTION:A magnetic field applying means 5 has the permanent magnet 6 and the yoke part 7 having a high magnetic permeability. The permanent magnet 6 is arranged in parallel with the substrate surface of the magneto- optical disk 1. The yoke part 7 covers the magnetic pole surfaces on both sides of the permanent magnet 6. The magnetic fluxes emitted from the one magnetic pole of the permanent magnet concentrate to the yoke part and the greater part thereof penetrate the magneto-optical disk 1 from the yoke part of the magnetic pole and, thereafter, the magnetic fluxes advance along the magneto-optical disk 1, again penetrate the magneto-optical disk 1 near the yoke part of the magnetic pole on the opposite side and return to the magnetic pole by passing the other yoke part.

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 the information that has been recorded once, it is necessary to erase the data once and then record new information. Therefore, the rewriting time becomes 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 initialized medium 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 high coercive force at room temperature and a relatively low magnetization reversal temperature as compared with the recording layer, and the recording layer, conversely, has a relatively small coercive force at room temperature as compared with the memory layer. The magnetization reversal temperature is relatively high. 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. Further, in order to increase the C / N value of the reproduction signal, there has been proposed a structure in which a reading layer having a higher Curie point and a higher Kerr effect is stacked 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. 64-046247.
With this method, it is not necessary to incorporate an initializing magnet in the magneto-optical disk recording device, the recording device can be downsized, and
There is an advantage that recording and reproduction of a disc that does not require an initializing magnetic field can be performed without any problem.

[0008]

However, the method proposed so far as a means for incorporating an initialization magnet in a magneto-optical disk cartridge is, as shown in FIG. 3 (a), provided on one inner surface of the cartridge. , A method of applying a magnetic field by arranging a magnet so that the magnetic pole is perpendicular to the disk surface,
Alternatively, as shown in FIG. 3B, there has been a method of applying a magnetic field by arranging magnets on both inner surfaces of the cartridge so that magnetic poles are perpendicular to the disk surface. These methods require a magnetic circuit (referred to as a yoke) for returning the magnetic flux passing through the disk surface to the magnet, which causes a problem of high cost. Also, since one or a set of magnets can only realize magnetic flux in one direction, a double-sided magneto-optical disk cartridge has two magnets.
There is a problem that the cost is further increased because two or more pieces are required.

[0009]

In order to solve such a problem, the inventors of the present invention have conducted intensive studies and found that by mounting a permanent magnet having a yoke covering a magnetic pole surface parallel to the disk surface, The present invention has been completed by finding that the cost can be kept low because only one magnet or one set is required.

Accordingly, the present invention is, firstly, "at least,
A magneto-optical disk cartridge in which a magneto-optical disk which can be overwritten by optical modulation and a magnetic field applying means for applying an initializing magnetic field to the magneto-optical disk are provided inside, wherein the magnetic field applying means includes the magneto-optical disk. A magneto-optical disk cartridge comprising a permanent magnet placed parallel to the surface and a yoke covering the magnetic pole surface of the permanent magnet. 2. A permanent magnet mounted parallel to a surface, and a U-shaped yoke covering a surface of the permanent magnet opposite to the magneto-optical disk and a magnetic pole surface. Thirdly, the distance between the yoke tip of the magnetic pole portion of the permanent magnet of the magnetic field applying means and the magneto-optical disk is the distance between the permanent magnet and the magneto-optical disk. Claim, characterized in that also small 1
4. The magneto-optical disk cartridge according to claim 4, further comprising: fourthly, a magnetic flux converging means is provided at a portion opposite to the magnetic field applying means with the magneto-optical disk interposed therebetween. It provides a "magneto-optical disk cartridge".

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

[0012]

1 is a conceptual view showing a magneto-optical disk cartridge of the present invention. The magneto-optical disk cartridge of the present invention includes a magneto-optical disk 1, a rectangular housing portion 2 for rotatably holding and accommodating the magneto-optical disk, and an optical head for irradiating the disk with a laser beam in the vicinity of the disk. It comprises an opening 3 provided, a shutter 4 covering the opening when not in use, and a magnetic field applying means 5 for applying an initializing magnetic field to the magneto-optical disk.

A magneto-optical disk has a multi-layer overwritable magnetic layer protected by a protective film formed on a transparent substrate. The magnetic layer is at least a memory layer having perpendicular magnetic anisotropy and a recording layer. Consists of two layers,
The magnetization of the recording layer can be initialized in one direction by the magnetic field applying means 5. A hub is attached to the center of the magneto-optical disk, and at the time of recording and reproducing, the hub is connected to the disk rotating means of the recording device to transmit the rotational force to the disk and rotate the magneto-optical disk 1.

Recording and reproduction are performed by opening the shutter 4 and irradiating the magneto-optical disk 1 with a laser beam focused through the opening 3. 2 (a) and 2 (b) are conceptual views in which a portion of the magnetic field applying means 5 according to the present invention is enlarged, and (a) and (b) are aspects of the present invention, respectively. The magnetic field applying means includes a permanent magnet portion 12 and a yoke portion 13 having high magnetic permeability.
The permanent magnet 12 is arranged parallel to the substrate surface of the magneto-optical disk 11. As a material of the permanent magnet, a material having a large residual magnetic flux density and a large coercive force is desirable, and NdFeCo which is a rare earth transition metal alloy or the like is preferable. As the material of the yoke portion, low carbon steel having high magnetic permeability, silicon steel or the like is used.

In the embodiment shown in FIG. 2 (a), the yoke portion 13 covers the magnetic pole surfaces on both sides of the permanent magnet. The magnetic flux emitted from one magnetic pole of the permanent magnet is concentrated in the yoke portion, and most of the magnetic flux penetrates the magneto-optical disk 11 from the yoke portion of the magnetic pole and then advances along the magneto-optical disk 11 to the yoke of the opposite magnetic pole. In the vicinity of this portion, the magneto-optical disk 11 is penetrated again, and the magnetic flux is returned to the magnetic pole through the other yoke portion. A part of the magnetic flux concentrated in the yoke portion flows back to the other magnetic pole through the opposite side of the magneto-optical disk.

In the embodiment shown in FIG. 2B, the yoke portion 13
Covers the magnetic pole surface of the permanent magnet and the surface of the permanent magnet opposite to the disk. The magnetic flux emitted from one magnetic pole of the permanent magnet is concentrated in the yoke portion, and most of the magnetic flux penetrates the magneto-optical disk 11 from the yoke portion of the magnetic pole and then advances along the magneto-optical disk 11 to the yoke of the opposite magnetic pole. In the vicinity of this portion, the magneto-optical disk 11 is penetrated again, and the magnetic flux is returned to the magnetic pole through the other yoke portion. In this method, the amount of magnetic flux leaking to the outside of the magnetic field applying means is reduced as compared with the mode shown in (a), so that there is an advantage that the influence of the magnet to the outside of the cartridge can be suppressed. Also in this mode, a part of the magnetic flux concentrated in the yoke portion flows back to the other magnetic pole through the opposite side of the magneto-optical disk.

When the magneto-optical disk 11 passes through the magnetic field applying means 15, the magneto-optical disk 11 is affected by two magnetic fields in the opposite directions which penetrate the magneto-optical disk 11. At this time, the magnetization of the recording layer of the magneto-optical disc is initialized to the direction of the magnetic field immediately before recording due to the influence of the magnetic flux passing later in the magnetic flux in two directions depending on the rotational direction of the disc (rotational direction). If it is different, the initialization direction will be opposite). In the case of a double-sided bonded type magneto-optical disk, it is necessary for recording and reproduction on the front surface and the back surface that the relative rotation direction and the initialization direction of the disk as viewed from the head are the same on both surfaces. Since the cartridge insertion surface is opposite between the front surface and the back surface, the disk rotation direction and the initialization direction viewed from the cartridge are opposite. Therefore, in the conventional magneto-optical disk cartridge as shown in FIG. 3, two magnetic field applying means were required to reverse the initialization directions on the front and back sides. However, in the magneto-optical disk cartridge of the present invention, if the rotation direction is different, the initialization direction is reversed, so that it is possible to initialize both sides with one magnetic field applying means.

When the tip of the yoke of the magnetic pole portion of the permanent magnet is closer to the magneto-optical disk than the end surface of the permanent magnet, the magnetic field applying means causes the magnetic flux emitted from the yoke tip to be perpendicular to the magneto-optical disk. It is more preferable because it concentrates. In some cases, in order to efficiently concentrate the magnetic flux emitted from the yoke portion on the magneto-optical disk, a magnetic flux concentrating means having a high magnetic permeability is provided in the cartridge on the side opposite to the magnetic field applying means with the magneto-optical disk interposed therebetween. Good.

Since the magneto-optical disk cartridge of the present invention can be made to look exactly the same as the conventional ISO standard product, it is convenient to maintain compatibility with these.

[0020]

As described above, according to the present invention,
A magneto-optical disk cartridge capable of overwriting can be manufactured at low cost because only one magnet or one set is required, and a magneto-optical recording device using the magnet is equipped with an initialization magnetic field applying means. Since it is unnecessary, it can be miniaturized. Furthermore, compatibility with a conventional disk cartridge for non-overwrite magneto-optical recording which does not require an initializing magnetic field can be obtained.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a magneto-optical disk cartridge of an embodiment of the present invention.

FIG. 2 is an enlarged conceptual diagram of a magnetic field applying unit according to an embodiment of the present invention. (A) and (b) are different embodiments.

FIG. 3 is a conceptual diagram showing a conventional overwritable magneto-optical disk cartridge.

[Explanation of symbols]

 1 ... Magneto-optical disk 2 ... Cartridge part 3 ... ... Cartridge opening part 4 ... Shutter part 5 ... Magnetic field applying means 6 ... Permanent magnet member 7 ... Yoke part and above

Claims (4)

[Claims] 1. A magneto-optical disk cartridge having at least a magneto-optical disk capable of overwriting by optical modulation and magnetic field applying means for applying an initializing magnetic field to the magneto-optical disk, wherein the magnetic field is applied. Means
A permanent magnet mounted parallel to the surface of the magneto-optical disk;
A magneto-optical disk cartridge comprising a yoke covering the magnetic pole surface of the permanent magnet. 2. A U-shaped yoke in which the magnetic field applying means covers a permanent magnet mounted parallel to the surface of the magneto-optical disk, a surface of the permanent magnet opposite to the magneto-optical disk, and a magnetic pole surface. The magneto-optical disk cartridge according to claim 1, comprising: 3. The magnetic field applying means, wherein the distance between the yoke tip of the magnetic pole portion of the permanent magnet and the magneto-optical disk is smaller than the distance between the permanent magnet and the magneto-optical disk. Magneto-optical disk cartridge. 4. A magneto-optical disk cartridge according to claim 1, wherein a magnetic flux converging means is provided at a portion opposite to the magnetic field applying means with the magneto-optical disk interposed therebetween.