JPH05342679A - Full-surface erasing device and method for magneto-optical disk medium - Google Patents

Abstract

PURPOSE:To enable the generation of a large magnetic field of about 25KOe or more with the full-surface erasing device for which permanent magnets are used relating to the full-surface erasing device and method to be used at the time of producing a magneto-optical disk medium and a magnetic recording medium of a perpendicular magnetic recording type. CONSTITUTION:A pair of yokes 18, 19 consisting of magnetic materials are disposed to face each other so that the magneto-optical disk medium can pass between these yokes 18 and 19. The one yoke 18 is held by a pair of the permanent magnets 20, 21, the same poles of which face each other. The other yoke 19 is held by a pair of the permanent magnets 22, 23, the same poles of which different from the yoke 18 side polarity of the permanent magnets 20, 21 face each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a full erase device and a full erase method used when manufacturing a magneto-optical disk medium or a perpendicular magnetic recording type magnetic recording medium.

[0002]

[Prior Art]

[Outline of Magneto-Optical Disk Device] FIG. 5 is a perspective view showing the basic configuration of the magneto-optical disk device. The laser light emitted from the semiconductor laser LD is collimated by the collimator lens 1 into a parallel beam, guided to the beam splitter 2, narrowed down by the objective lens 3, irradiated onto the magnetic recording film 4, and irradiated with the laser light. Only the temperature rises locally.

When the temperature of the magnetic recording film 4 is raised to near the Curie temperature, its coercive force decreases, and the magnetization of that portion is reversed by the external magnetic field 6 of about several hundred Oe. As a result, recording pits 5 of about 1 μm are formed.

When reproducing, as shown in FIG. 6, the magnetic recording film 4 is irradiated with a laser beam 7 having a power lower than that at the time of recording. Since the laser light 7 in this case is linearly polarized light, the polarization plane of the reflected light 7a rotates counterclockwise or clockwise depending on whether the magnetization direction of the magnetic recording film 4 is upward or downward due to the Kerr effect. .. The difference in rotation of the polarization plane is converted into light intensity by the analyzer 8 and detected by the photodetector 9 to be used as a reproduction signal.

[Magnetic State of Magneto-Optical Disk Medium] In the magneto-optical disk medium, as shown in FIG. 7, a protective film 11 made of SiNx or the like is formed on a substrate 10 made of polycarbonate or the like, and magnetic recording is performed thereon by TbFeCo or the like. The film 4 is formed by sputtering and the upper surface is covered with a protective film 12 such as SiNx.
In the state where the magnetic recording film 4 is formed by sputtering, the magnetization directions are not aligned in a fixed direction, but are random directions, as shown in FIG.

Therefore, it is necessary to reduce the medium noise by preliminarily aligning the direction of perpendicular magnetization in a fixed direction as shown in FIG. The process of aligning the direction of perpendicular magnetization with the erasing direction is called full-face erase (bulk erase).

[Types of Full Erase Method] There are three types of methods for completely erasing a magneto-optical disk medium having a large coercive force (Hc) of 10 to 20 KOe.

In the magnetic field generated by the permanent magnet,
This is a method of erasing the entire surface by passing through the magneto-optical disk medium, the device is simple, and maintenance is sufficient only with the operating system. However, since the maximum magnetic field is only about 14 KOe, it can be applied only to a medium having a small coercive force.

This is a method in which a magneto-optical disk medium is passed through a magnetic field generated by an electromagnet, and a large magnetic field of about 25 KOe can be obtained. However, in order to generate a large magnetic field of about 25 KOe, a large electromagnet having a weight of 1 ton or more is required, and a water cooling mechanism for the electromagnet is also required.

The magneto-optical disk medium is heated to a high temperature, the coercive force is lowered, and the entire surface is erased by a magnet. This method has no limitation on the coercive force of the magneto-optical disk medium, but since it heats the medium, it may adversely affect the resin substrate and is not suitable for the magneto-optical disk medium using the resin substrate.

[Conventional permanent magnet type full-face erase device]
FIG. 8 is a side view and a bb cross-sectional view showing a conventional full-face erase device using a permanent magnet. Two permanent magnets 13, 1
4 are opposed to each other, and the other ends are connected to each other by a magnetic yoke 15, and by inserting the magneto-optical disk medium 17 into the gap 16 between the permanent magnets 13 and 14,
Erase the entire surface.

[0012]

However, in the full erase device having such a structure, the magnetic field generated between the permanent magnets 13 and 14 is limited to about 14 KOe, and as a result,
The coercive force of the magneto-optical disk medium 17 after erasing the entire surface is 10
It is as small as KOe. Considering variations in the characteristics of the optical head, the coercive force of the magneto-optical disk medium is 10
The thing of about 20 KOe is desired. In order to realize this level of coercive force, it is necessary for a full-face erase device to be able to generate a magnetic field of about 25 KOe or more.

The technical problem of the present invention is to pay attention to such a problem, and in a full-face erase device using a permanent magnet,
It is to be able to generate a large magnetic field of about 25 KOe or more.

[0014]

FIG. 1 is a plan view and a side view for explaining the basic structure of a full-face erase device according to the present invention. The invention according to claim 1 is a pair of yokes 1 made of a magnetic material.
The magneto-optical disk medium 17 can pass between both yokes 18 and 19 with 8 and 19 facing each other. The one yoke 18 is sandwiched by a pair of permanent magnets 20 and 21 having the same poles (for example, N poles) facing each other.

The other yoke 19 has the permanent magnets 20,
A pair of permanent magnets 2 having the same poles (for example, S poles) different from the polarities (for example, N poles) on the yoke 18 side of 21 are opposed to each other.
It is sandwiched between 2 and 23.

According to a second aspect of the present invention, the yokes 18, 19 are parallel to the yokes 18, 19 and at least on one side.
This is a full-face erase device provided with an auxiliary magnetic circuit for generating an auxiliary magnetic field F8 in the same direction as the magnetic field between them.

According to a third aspect of the present invention, the pair of yokes 18 and 1 are provided.
Reference numeral 9 denotes a full-face erase device having an elongated shape in a direction (Y direction) orthogonal to the passing direction X of the magneto-optical disk medium 17 to be erased entirely.

A fourth aspect of the present invention is a method of inserting the magneto-optical disk medium between the yokes 18 and 19 and then letting the magneto-optical disk medium pass through an auxiliary magnetic field when the entire surface of the magneto-optical disk medium is erased by the apparatus of the second aspect. Is.

[0019]

According to the structure of claim 1, between the upper and lower yokes 18 and 19 of FIG. 1, a magnetic flux F1 attracted between the N pole of the upper right permanent magnet 21 and the S pole of the lower right permanent magnet 23 is attracted. Occurs. Moreover, an attractive magnetic flux F2 is also generated between the N pole of the upper left permanent magnet 20 and the S pole of the lower left permanent magnet 22.

A magnetic flux F3 repulsive between the N poles is generated between the pair of upper permanent magnets 20 and 21, but the repulsive magnetic flux F3 is eventually guided by the yoke 18 to the lower yoke 19. It becomes F4. A magnetic flux F5 repulsive between the S poles is also generated between the pair of lower permanent magnets 22 and 23, and this repulsive magnetic flux F5 is eventually drawn by the yoke 19 so that the repulsive magnetic flux F3 in the upper yoke 18 is drawn. To work.

Therefore, the magnetic flux of two pairs of permanent magnets is concentrated between the yokes 18 and 19, and when the permanent magnets having the magnetic force of the same degree as in FIG.
It is possible to obtain a magnetic field that is nearly double. When the magneto-optical disk medium 17 is inserted into this magnetic field and the entire surface is erased, the coercive force of the magneto-optical disk medium 17 can be remarkably improved. Note that F6 and F7 are the yoke 1 between the upper and lower permanent magnets.
The reverse magnetic flux does not pass through 8 and 19.

In the case of a magneto-optical disk medium having a small coercive force even if the entire surface is erased in one direction by the magnetic field between the yokes 18 and 19, in order to take out the magneto-optical disk medium, the reverse direction is not passed through the yokes 18 and 19. When passing through the magnetic field F6 or F7, the entire area is erased in the opposite direction.

However, as in claim 2, the magnet 24,
An auxiliary magnetic field such as 25 is provided to allow the yoke 1
When an auxiliary magnetic field F8 in the same direction as the magnetic fluxes F1, F2, F4 between 8 and 19 is generated, even if the entire magnetic field is erased in the opposite direction by the opposite magnetic fields F6 and F7, the auxiliary magnetic field F8 again causes normal magnetization. Erase all over in the direction. Therefore,
Even if the magneto-optical disk medium has a small coercive force due to manufacturing variations, it is possible to securely erase the entire surface.

According to a third aspect, the pair of yokes 1 is provided.
Magneto-optical disk medium 1 in which 8 and 19 are entirely erased
When the shape is elongated in the direction (Y direction) orthogonal to the passing direction X of 7, the magneto-optical disk medium 17 is moved to the yoke 18,
The entire surface of the magneto-optical disk medium 17 can be erased all at once by simply inserting it between 19 and allowing it to pass.

According to a fourth aspect of the present invention, in the apparatus of the second aspect, when the magneto-optical disk medium is inserted between the yokes 18 and 19 and then passes through the auxiliary magnetic field, the magneto-optical disk medium is re-normalized. Since it is erased entirely in the direction, the yoke 1
The influence of the reverse magnetic field due to 8 and 19 is eliminated.

[0026]

EXAMPLES Next, examples of practical implementation of the full-area erase apparatus for a magneto-optical disk medium according to the present invention will be described. FIG. 2 is a plan view and a side view showing an embodiment of the invention of claim 1. The width W of the yokes 18 and 19 is 6 mm,
The length L of the yokes 18 and 19 and the permanent magnets 20 to 23
By setting the value to 170 mm, it is possible to erase the entire surface of a magneto-optical disk medium having a diameter of 130 mm or 86 mm.

In this way, the length of the pair of yokes 18 and 19 is elongated in the Y direction orthogonal to the passing direction X of the magneto-optical disk medium 17 whose entire surface is erased, and the magneto-optical disk medium 17 is By making it longer than the diameter, the entire surface can be erased reliably.

The tips of the yokes 18 and 19 are fixed to the permanent magnet 20.
23 to 23, and is formed in a tapered shape so that the magnetic flux concentrates. The distance between the yokes 18 and 19 was 4 mm. With this configuration, both yokes 18, 1
A magnetic field of 24 KOe could be obtained during 9 minutes.

FIG. 3 is a plan view and a side view showing an embodiment of the invention of claim 2. In this embodiment, the yokes 18, 19 are
In between, insert the magneto-optical disk medium 17 from the left side of the figure,
If taken out from the right side, an auxiliary magnetic circuit for generating a magnetic field in the same direction as the magnetic field between the yokes 18 and 19 is provided on the taken out side.

In this embodiment, in the auxiliary magnetic circuit, the auxiliary yokes 26 and 27 are arranged so as to face each other in parallel with the yokes 18 and 19, and the yokes 18 and 19 are provided between the auxiliary yokes 26 and 27.
Permanent magnets 28 and 29 for generating a magnetic field F8 in the same direction as the magnetic field between them are arranged adjacent to each other.

The numerical values in FIG. 3 are the actual sizes (unit: mm) from the center positions of the yokes 18 and 19 to each part. The magnetic fields at these positions are actually measured as shown in FIG. In FIG. 4, the horizontal axis represents the yokes 18, 1
The position from the center of 9 and the vertical axis are the direction and magnitude of the magnetic field. The positive direction is the magnetic field in the entire erase direction, and the negative direction is the magnetic field in the opposite direction to the total erase.

The peak P1 of the curve showing the value of the magnetic field is the value of the magnetic field in the entire erase direction generated between the yokes 18 and 19, and the peak P2 is the value of the reverse magnetic field F7 in FIG.
The peak P3 is the value of the magnetic field F6 in the reverse direction in FIG. 1, the peak P4 is the value of the reverse magnetic field F9 generated by the auxiliary magnetic circuit, and the peak P5 is the value of the magnetic field F8 in the entire erase direction generated by the auxiliary magnetic circuit. is there.

As is clear from this figure, the yoke 1
Since a large magnetic field of maximum 24 KOe is generated between 8 and 19,
It is possible to erase the entire surface of a magneto-optical disk medium having a large coercive force of about 10 to 20 KOe. However,
Before and after the yoke 18 and 19, the peak P2,
Like P3, the reverse magnetic fields F7, F of about 7-8 KOe
6 occurs.

In the case of a magneto-optical disk medium having a large coercive force of about 10 to 20 KOe, it is about 7 to 8 KOe when it passes through the magnetic field F7 or F6 in the opposite direction after being erased entirely between the yokes 18 and 19. Even if a magnetic field in the opposite direction of is applied,
The magnetic field of the magnetic recording film does not reverse.

However, due to manufacturing variations and the like, 6
In the case of a magneto-optical disk medium having a small coercive force of about 10 KOe, when it passes through the reverse magnetic field F7 or F6, the reverse magnetic field of about 7-8 KOe may completely erase the reverse direction. is there. However, since the auxiliary magnetic field generates a magnetic field in the positive direction of 10 KOe or more, even if it is magnetized in the reverse direction by the magnetic fields F7, F6, and F9 in the reverse direction, it is finally returned to the normal direction by the magnetic field F8 in the positive direction. It will be erased entirely.

In the apparatus of this embodiment, the entire surface of the erased magneto-optical disk medium 17 moves from the left side to the right side of the drawing and passes between the yokes 18 and 19 and between the yokes 26 and 27. .. Alternatively, it may be passed from right to left as indicated by arrow a ₁ and then returned from left to right as indicated by arrow a ₂ to be taken out.

The overall erase of the magneto-optical disk medium has been described above, but the present invention can also be applied to the overall erase of a perpendicular magnetic recording type magnetic recording medium.

[0038]

As described above, according to the first aspect, in addition to the magnetic field attracted between the upper permanent magnets 20 and 21 and the lower permanent magnets 22 and 23, the upper permanent magnets 20 and 21 are added.
Since the repulsive magnetic field F3 between them and the repulsive magnetic field F5 between the lower permanent magnets 22 and 23 are effectively guided between the yokes 18 and 19, the magnetic fields of four permanent magnets are concentrated between the yokes 18 and 19. It is possible to obtain an extremely large magnetic field. Further, since the permanent magnet and the yoke can be used alone, the device is simple and maintenance is easy.

According to the second aspect of the invention, the auxiliary magnetic field F8 in the same direction as the magnetic field between the yokes 18 and 19 is generated.
Since the coercive force is small, even if the entire magnetic field is erased in the opposite direction by the opposite magnetic fields F6 and F7, the entire magnetic field is erased again in the normal magnetization direction by the auxiliary magnetic field F8.
Even with a magneto-optical disk medium having a small coercive force, the entire surface is finally erased in the normal direction.

Therefore, a medium having a small coercive force to a medium having a large coercive force can be applied, and there is no problem even if the coercive force varies among the magneto-optical disk media, and the target medium is not limited.

According to a third aspect, the pair of yokes 1 is provided.
Magneto-optical disk medium 1 in which 8 and 19 are entirely erased
By making the shape elongated in the direction orthogonal to the passage direction of 7, it is possible to erase the entire surface of the magneto-optical disk medium 17 all at once.

According to a fourth aspect of the present invention, in the apparatus of the second aspect, after inserting the magneto-optical disk medium between the yokes 18 and 19, the medium is taken out from the auxiliary magnetic field side.
The magneto-optical disk medium completely erased in the opposite direction by the magnetic field in the opposite direction by 19 is erased again in the normal direction by the auxiliary magnetic field, so that even if the magneto-optical disk medium has a small coercive force, it is surely normal. You can erase the entire area in the direction of.

[Brief description of drawings]

FIG. 1 is a plan view and a side view showing a basic configuration of a full-face erase apparatus for a magneto-optical disk medium according to the present invention.

FIG. 2 is a plan view and a side view showing an embodiment of the invention of claim 1;

FIG. 3 is a plan view and a side view showing an embodiment of the invention of claim 2;

FIG. 4 is a diagram showing measured values of a magnetic field in each part of the embodiment apparatus of FIG.

FIG. 5 is a perspective view showing a basic configuration of a magneto-optical disk device.

FIG. 6 is a sectional view showing the reproducing principle of the magneto-optical disk medium.

FIG. 7 is a sectional view of a magneto-optical disk medium.

FIG. 8 is a side view and a bb sectional view of a conventional full-face erase device using a permanent magnet.

[Explanation of symbols]

 LD semiconductor laser 1 Collimator lens 2 Beam splitter 3 Objective lens 4 Magnetic recording film 5 Recording pit 6 External magnetic field 7 Laser light (for reproduction) 7a Reflected light 8 Analyzer 9 Photodetector 10 Substrate 11,12 Protective film 13,14 Permanent magnet 15 yoke 16 gap 17 magneto-optical disk medium 18,19 yoke 20-23 permanent magnet F1-F9 magnetic flux (magnetic field) 24,25 auxiliary magnet 26,27 auxiliary yoke 28,29 permanent magnet

Claims (4)

[Claims] 1. A pair of yokes (18), (19) made of a magnetic material.
So that the magneto-optical disk medium can pass between the two yokes (18) and (19), and one yoke (18) has a pair of permanent magnets (20) and (21) with the same poles facing each other. The other yoke (19) is the yoke of the permanent magnets (20), (21).
An all-erasing device for a magneto-optical disk medium, characterized in that it has a pair of permanent magnets (22), (23) having the same poles different from the polarity on the (18) side and facing each other. 2. A magnetic circuit for generating an auxiliary magnetic field in the same direction as the magnetic field between the yokes (18) and (19) is provided in parallel to at least one side of the yokes (18) and (19). 2. An all-erasing device for a magneto-optical disk medium according to claim 1, wherein 3. The pair of yokes (18), (19) has an elongated shape in a direction orthogonal to the passing direction of the magneto-optical disk medium erased over the entire surface. An erasing device for the entire surface of the magneto-optical disk medium according to claim 2. 4. The entire surface of a magneto-optical disk medium according to claim 2, wherein the magneto-optical disk medium is inserted between the yokes (18) and (19) and then passed through an auxiliary magnetic field to be taken out. Erase method.