JPH02173902A - Magnetic field generating device - Google Patents

Abstract

PURPOSE:To give a uniform magnetic field to accurately record or erase information without giving noise to an information recording medium by arranging a magnetic flux generating face in a position facing the surface of the information recording medium and constituting the peripheral part of the magnetic flux generating face so that it is distant from the surface of the information recording medium. CONSTITUTION:The distance between a peripheral part 16b of a magnetic flux generating face 16 and a magnetic film 22 is made longer than that between a center part 16a of the magnetic flux generating face 16 and the magnetic film 22 for the purpose of giving a uniform magnetic field intensity distribution to the magnetic film 22 of a magneto-optical disk 20. By this structure, the edge effect of the magnetic field distribution is relaxed to give a uniform magnetic field intensity distribution to the magnetic film 22. Thus, information is accurately recorded or erased without noise because the intensity of magnetization of the magnetic film 22 is approximately uniform.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a magnetic field generating device included in a magneto-optical disk device, etc. that records and erases information using the magneto-optical effect, for example. Regarding.

(Prior Art) As an information recording/reproducing device capable of recording and erasing information, for example, a magneto-optical disk device has been developed and is being put into practical use. A magneto-optical disk is a recording medium applied to this magneto-optical disk device, and this magneto-optical disk is provided with a magnetic film as a recording film. This magnetic film has magnetization oriented in a predetermined direction, and information is recorded and erased by applying a magnetic field to this magnetic film and irradiating it with light. In other words, when the irradiated magnetic film is heated to a temperature that exceeds the Curie point, or the magnetic force of the applied magnetic field exceeds the magnetic coercive force of the magnetic film, The direction of magnetization of the magnetic film is the direction of the applied magnetic field.

Conventionally, as a device that applies a magnetic field to this magneto-optical disk,
For example, one disclosed in Japanese Unexamined Patent Publication No. 164004/1988 is known. This device is constructed as shown in FIG. That is, a rod-shaped magnetic core portion 30 made of a magnetic material. an electromagnetic coil 32 wound around a magnetic core 30;
A magnetic core portion 30 generates magnetic flux when a current is passed through the electromagnetic coil 32. A magnetic core extension part 34 that extends from one end of the magnetic core part 30 and is also made of a magnetic material and generates magnetic flux is magnetically connected to the other end of the magnetic core part 30 and defines a space in which the information recording medium 38 is to be placed. A yoke portion 36 is provided through which the magnetic flux generated from the magnetic core extension portion 34 is returned. The magnetic core extension 34 is arranged to face the magnetic film 40 of the information recording medium 38, and when a current is supplied to the electromagnetic coil 32, magnetic flux is generated from the surface of the magnetic core extension 34. In this device, the magnetic flux generating surface 42 of the magnetic core extension portion 34 is connected to the magnetic film 4 of the information recording medium 38.
It is arranged parallel to 0 and has a flat shape.

(Problem to be solved by the invention) In the conventional magnetic field generating device, the surface 42 that generates magnetic flux
has a flat shape as shown in FIG. Therefore, the peripheral edge of the magnetic flux generating surface 42 has an angular configuration. When magnetic flux is generated from the magnetic core extension portion 34, the magnetic flux is generated intensively from this corner portion 46, and the edge effect of the magnetic field distribution refers to the fact that the portion where the magnetic field is generated is sharp. This is a phenomenon in which magnetic flux is relatively more concentrated at the pointed part than at other parts. Therefore, the magnetic field intensity distribution on the magnetic film 40 of the information recording medium 38 becomes non-uniform as shown in FIG. 13. That is, this phenomenon occurs when the magnetic core extension part 3
Although there are some differences depending on the strength of the magnetic field generated from the magnetic core extension 34, if the distance between the magnetic core extension 34 and the magnetic film 40 is about 101 or less, as shown in (a), the magnetic core extension 34 The magnetic flux intensively generated at the corner portion 46 of the magnetic film 40
As a result of this influence, the strength of the magnetic field on the magnetic film 40 becomes non-uniform. Further, the magnetic flux intensively generated at the corner portion 46 of the magnetic core extension portion 34 is transmitted to the magnetic flux generation surface 4
Since the magnetic field is more diffused than the magnetic field generated on the plane of 2, the distance between the magnetic core extension 34 and the magnetic film 40 is approximately 1
01 m or more, as shown in (b), contrary to the case shown in (a), the corner part 46 of the magnetic core extension part 34
The magnetic field in the magnetic film 40, which is relatively close to , becomes weaker.

If the magnetic field strength distribution in the magnetic film 40 is uneven in this way, noise is likely to occur in the magnetic film 40 when recording or erasing information, making it impossible to accurately record or erase information. There is a problem. In other words, the size of the magnetic domain, which is the unit of information to be recorded, is determined by the interaction between the temperature rise caused by the irradiation of light from the objective lens 48 and the magnetic field strength. The problem was that this resulted in non-uniformity and noise.

Therefore, the present invention aims to provide a magnetic field generating device that can apply a uniform magnetic field to an information recording medium in order to accurately record or erase information without imparting noise to the information recording medium. purpose.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present invention provides, in a first invention, a magnetic flux generating section having a magnetic flux generating surface that generates magnetic flux; In a magnetic field generating device, the magnetic flux receiving section receives the magnetic flux generated by the magnetic flux generating section, and an information storage medium capable of recording and erasing information can be placed in the space between the magnetic flux generating section and the magnetic flux receiving section. The magnetic flux generation surface of
The periphery of the magnetic flux generating surface, which is disposed at a position facing the surface of the information recording medium, is smaller than the central portion of the magnetic flux generating surface.
The present invention provides a configuration in which the distance from the surface of the information storage medium is large, and in the second invention, a magnetic flux generating section having a magnetic flux generating surface that generates magnetic flux, and a magnetic flux generated by the magnetic flux generating section are provided. (7,
In a magnetic field generating device in which an information storage medium capable of recording and erasing information can be placed in a space between a magnetic flux generating section and a magnetic flux receiving section, the magnetic flux generating surface of the magnetic flux generating section is located at a position facing the surface of the information recording medium. In the third aspect of the present invention, the peripheral part of the magnetic flux generating surface is located closer to the surface of the information storage medium than the central part of the magnetic flux generating part. , has a magnetic flux generating part that H a magnetic flux generating surface that generates magnetic flux, and a magnetic flux receiving part that receives the magnetic flux generated by the magnetic flux generating part, and information is recorded and stored in the space between the magnetic flux generating part and the magnetic flux receiving part. In a magnetic field generating device in which an erasable information storage medium can be placed, a structure is provided in which the peripheral edge of a magnetic flux generating surface of a magnetic flux generating section is smooth.

(Function) In the present invention, the distance relationship with the information recording medium is made different between the periphery and the center of the magnetic flux generating surface that generates the magnetic flux of the magnetic core extension, thereby reducing the edge effect of the magnetic field. can be reduced. This makes it possible to provide the magnetic film with a -like magnetic field intensity distribution. In addition, in the present invention, by having a smooth structure instead of an angular structure on the peripheral edge of the magnetic flux generating part that generates the magnetic flux of the magnetic core extension part, the edge effect of the magnetic field can be similarly reduced, and the information It becomes possible to provide a recording medium with a -like magnetic field strength distribution.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
FIG. 1 is a schematic configuration diagram showing a magnetic field generating device of the present invention. This magnetic flux generating device includes a magnetic core formed of a prismatic or plate-shaped magnetic material; An extending portion 14 that is formed and generates a magnetic field generated by the electromagnetic coil core 2. The yoke section 18 is magnetically connected to the other end of the magnetic core section 10 and receives the magnetic flux generated from the magnetic core extension section 14 back through the space in which the information recording medium 20 is to be placed. The information recording medium 20 is a so-called magneto-optical disk 20, and is composed of a substrate 21 and a magnetic film 22. However, this structure
The structure is not limited to that shown in FIG. 1, but may also have a two-layered structure with a protective film made of silicon or the like added thereto.

In the magnetic field generator shown in FIG.
When a current is supplied to the magnetic core portion 10, magnetic flux is supplied to the magnetic core extension portion 14. The magnetic core extension portion 14 has a magnetic flux emitting surface 16 at a position facing the magneto-optical disk 20. From this magnetic flux emitting surface 16 to the magneto-optical disk 20
Magnetic flux is emitted towards. This emitted magnetic flux passes through the magneto-optical disk 20 and heads towards the yoke portion]8.

Furthermore, the magnetic flux directed toward this yoke portion 18 is directed to a magnetic core portion that is magnetically and mechanically connected to this yoke portion 18.]
Returned to -0. In the configuration shown in FIG. 1, the distance between the magnetic core extension]-4 and the magnetic film 22 is approximately 1011I1.
In this case, in order to give a uniform magnetic field strength distribution to the magnetic film 22 of the magneto-optical disk 20, the peripheral part 16b of the magnetic flux generating section 16 is
The distance between the magnetic film 22 and the central portion 16 of the magnetic flux generating surface 16 is
This is configured to be longer than the distance between a and the magnetic film 22. In other words, the stepped portion 1 extends from the central portion 16a of the magnetic flux generating portion 16 toward the peripheral portion 16b.
6e, and the distance between the peripheral portion 1.6b and the magnetic film 22 is longer than the distance between the central portion 16a and the magnetic film 22. By having such a structure, the edge effect of the magnetic field distribution can be alleviated. Therefore, this magnetic core extension portion 14 can provide a uniform magnetic field strength distribution to the magnetic film 22, as shown in FIG. If the magnetic field is applied uniformly, it can be assumed that the magnetic domain whose temperature increases due to the light irradiated from the objective lens 24 is almost constant. Therefore, by exceeding the Curie point temperature, etc., the direction of magnetization of the magnetic film 22 changes. Since the sizes of the magnetic domains facing the direction of the magnetic field are almost the same, accurate information can be recorded and erased without noise. The magnetic field applied to the magnetic film 22 returns to the yoke portion 18,
It is returned to the magnetic core part 10 which is magnetically and mechanically connected to this yoke part 18. Furthermore, by setting the direction of the current supplied to the electromagnetic coil 12 in two directions, the magnetic film 2
The direction of the magnetic field applied to 2 can be set in two directions.

Next, the configuration of another embodiment of the present invention will be described with reference to FIG.

Unlike the configuration shown in FIG. 1, when the distance between the magnetic core extension part 14 and the magnetic film 22 is about 10) or more, a structure having a magnetic flux generating surface 17 as shown in FIG. By providing this, a uniform magnetic field can be applied to the magnetic film 22. In addition, in this Figure 3, the first
Components having the same configuration and functions as the magnetic field generating device shown in the figure are designated by the same symbols, and their explanation will be omitted here. That is, the magnetic flux generating surface 1 of the magnetic core extension portion 14a
A stepped portion 17c is provided from the central portion 17a of the magnetic film 7 toward the peripheral portion 17b thereof, and the distance between the peripheral portion 17b and the magnetic film 22 is configured to be shorter than the distance between the central portion 17a and the magnetic film 22. It is something. By adopting such a structure, the stepped portion 17c can be brought close to the magnetic film 22, and an edge effect of the magnetic field distribution and a −-like magnetic field strength can be imparted to the magnetic film 22. The magnetic flux applied to the magnetic film 22 enters the yoke portion 18 through space, and is returned to the magnetic core portion 18 that is magnetically and mechanically connected to the yoke portion 18 . Furthermore, as shown in FIG.
When the distance between the magnetic film 22 and the magnetic film 22 is approximately 10+ am or less, the peripheral portion 19 of the magnetic flux generating surface 19 with the magnetic core extension portion 14c
By forming a into a smooth shape with a relatively large curvature, the edge effect of the magnetic field distribution can be alleviated, and a uniform magnetic field intensity distribution can be given to the magnetic film 22.

Next, the configuration of another embodiment of the magnetic field generating device of the present invention will be described with further reference to FIGS. 5 and 6.

The configuration of the magnetic field generating device of this embodiment is as follows: electromagnetic coils 25, 25, and 25, each of which generates a magnetic field by being supplied with an electric current. Magnetic flux generating sections 26 and 27 around which this electromagnetic coil 25 is wound generate magnetic flux, the magnetic flux emitted by these magnetic flux generating sections 26 and 27 passes through a magneto-optical disk 28, and a cross section serves as a return section for returning the magnetic flux. It is composed of a U-shaped yoke portion 29. In the magnetic field generating device shown in FIG. 5, a magnetic flux generating section 26 is arranged inside a yoke section 27. FIG. 5(a) is a front view of the magnetic field generator, and FIG. 5(b) is a side view. The magnetic flux generating section 26 includes a magneto-optical disk 28
The opposing surfaces 26a and 26b facing each other are constructed such that the opposing surface 26a is further away from the magneto-optical disk 28 than the opposing surface 26b.

This structure applies when the distance between the magneto-optical disk 28 and the magnetic flux generating section 26 is relatively short, within about 101 m, and when the distance exceeds about 10 mm, the opposing surface 26a is magneto-optically connected to the opposing surface 26b. Just move it closer to the disk 28. Further, the distance between the magneto-optical disk 28 and the magnetic flux generating section 26 is approximately 1
0+m or less, the opposing surface 26a of the magnetic flux generating section 26 is not separated from the magneto-optical disk 28;
The surface from 6b to the opposing surface 26a may be rounded to have a smooth shape. Next, the magnetic field generator shown in FIG.
FIG. 3 is a perspective view of a magnetic flux generating section 27 partially protruding from the contents of a yoke section 29; Similar to the magnetic field generating device shown in FIG. 5, the opposing surface 27a facing the magneto-optical disk (not shown) is separated from the magneto-optical disk (not shown) with respect to the opposing surface 27b. This structure is based on a magneto-optical disk (
(not shown) and the magnetic flux generating part is approximately 10IIIli
If the distance is greater than this distance, the opposing surface 27a may be moved closer to the magneto-optical disk (not shown) than the opposing surface 27b. In addition, when the distance between the magneto-optical disk (not shown) and the magnetic flux generating section 27 is about 10IIIli, the opposing surface 27a of the magnetic flux generating section 27 can be set apart from the two magneto-optical disks. The surface from 27b to the opposing surface 27a may be rounded to have a smooth shape. By configuring the magnetic flux generating sections 26 and 27 as described above, it is possible to provide a uniform magnetic field strength distribution to the magneto-optical disk.

In addition, FIGS. 7 to 1] use permanent magnets (and show the configuration of a magnetic field generating device. That is, as shown in these drawings, the magneto-optical disk 50 is connected to the objective lens 52. irradiated with light by the permanent magnet 54.
．． Recording of information by receiving magnetic fields from 56, 58, 60 and 62.

Erasure is performed. In Figures 7 to 1.1, (a
), the magnetic field generator records information on the magneto-optical disk 50,
It is a block diagram of a state in which erasing is possible, and (b) is a side view of the magnetic field generator. The permanent magnets 54, 56, 58, 60 and 62 have shafts 64, 66, 68, 70 and 72, respectively, which are connected to rotational axes 74, 76, 78, 80 and 72, respectively. By rotating around 82, permanent magnet 54, 56.58°6
The configuration is such that magnetic poles 0 and 62 are exchanged, and magnetic fields can be applied to the magneto-optical disk 50 in two directions. Magneto-optical disk 5 with permanent magnets 54, 56, 58, 60 and 62
The length of 0 in the radial direction is set to approximately 30 to 50 mm. Also, permanent magnets 54, 56, 58, respectively.
60 and 62 are rotating shafts 74, 76, 78, 80 and 82
The permanent magnets 54 and 56 of the magnetic field generator shown in FIGS.
A cylindrical structure having a circular cross section perpendicular to 76 is shown in FIG. At this time, the permanent magnet 54 is configured such that the distance between its end portions and the magneto-optical disk 50 is greater than the distance between its central portion a and the magneto-optical disk 50. The figure shows that the arrangement relationship between the permanent magnet 56 and the magneto-optical disk 50 is approximately 10ffiI11 with respect to the distance I7.
That's it for now. At this time, the permanent magnet 56 is configured such that the distance between its both ends d and the magneto-optical disk 50 is closer than the distance between its central portion C and the magneto-optical disk 50. Further, the permanent magnets 58, 60 of the magnetic field generator shown in FIGS. 9 and 10 have a prismatic structure with a rectangular cross section perpendicular to the rotating shaft 78, 80.

FIG. 9 shows a case where the distance between the permanent magnet 58 and the first magneto-optical disk 50 is about 10 ain+ or less. At this time, the permanent magnet 58 is configured such that the distance between its both ends r and the magneto-optical disk 50 is greater than the distance between its central portion e and the magneto-optical disk 50. FIG. 10 shows a case where the distance between the permanent magnet 60 and the magneto-optical disk 50 is approximately 1.0 m or more. At this time, the permanent magnet 60 is configured such that the distance between its end portions 11 and the magneto-optical disk is closer than the distance between its central portion g and the magneto-optical disk 50.

Moreover, the permanent magnet 62 of the magnetic field generator shown in FIG.
It has a cylindrical structure with a circular cross section perpendicular to the rotating shaft 82. The arrangement relationship between the permanent magnet 62 and the magneto-optical disk 50 is such that the distance therebetween is approximately 10 mm or more. At this time, the permanent magnet 62 has a smooth shape with relatively large curvature at both ends l.

As described above, by creating a structure in which the positional relationship between the surface that generates magnetic flux and the magneto-optical disk differs between the peripheral portion and the central portion, it is possible to provide the magneto-optical disk with a uniform magnetic field strength distribution.

[Effects of the Invention] Hereinafter and Detailed Description] Also, according to the present invention, the structure is such that the positional relationship between the magnetic flux generating surface that generates magnetic flux and the information recording medium is different between the peripheral portion and the central portion thereof. Accordingly, it is possible to provide a magnetic field generating device that can apply a uniform magnetic field to an information recording medium.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a magnetic field generating device showing an embodiment of the present invention,
FIG. 2 is a magnetic field strength distribution diagram in a magnetic field generating device according to an embodiment of the present invention, FIGS. 3 to 6 are block diagrams of a magnetic field generating device showing other embodiments of the present invention, and FIGS. 7 to 11 12 is a block diagram of a magnetic field generator equipped with a permanent magnet, FIG. 12 is a block diagram of a conventional magnetic field generator, and FIG. 13 is a diagram of magnetic field strength distribution in a conventional magnetic field generator.

Claims (3)

[Claims] (1) It has a magnetic flux generating section having a magnetic flux generating surface that generates magnetic flux, and a magnetic flux receiving section that receives the magnetic flux generated by the magnetic flux generating section, and information is stored in the space between the magnetic flux generating section and the magnetic flux receiving section. In a magnetic field generating device in which an information storage medium capable of recording and erasing information can be arranged, a magnetic flux generation surface of the magnetic flux generation section is arranged at a position facing the surface of the information recording medium, and the magnetic flux generation surface of the magnetic flux generation section A magnetic field generating device, characterized in that the peripheral portion is configured to be farther from the surface of the information storage medium than the central portion of the magnetic flux generating surface. (2) It has a magnetic flux generating section having a magnetic flux generating surface that generates magnetic flux, and a magnetic flux receiving section that receives the magnetic flux generated by the magnetic flux generating section, and information is stored in the space between the magnetic flux generating section and the magnetic flux receiving section. In a magnetic field generating device in which an information storage medium capable of recording and erasing information can be arranged, a magnetic flux generation surface of the magnetic flux generation section is arranged at a position facing the surface of the information recording medium, and the magnetic flux generation surface of the magnetic flux generation section A magnetic field generating device characterized in that the peripheral portion is configured to be closer in distance from the surface of the information storage medium than the central portion of the magnetic flux generating surface. (3) A magnetic flux generating section having a magnetic flux generating surface that generates magnetic flux, and a magnetic flux receiving section that receives the magnetic flux generated by the magnetic flux generating section, and information is provided in a space between the magnetic flux generating section and the magnetic flux receiving section. What is claimed is: 1. A magnetic field generating device in which an information storage medium capable of recording and erasing information can be arranged, characterized in that a peripheral edge of a magnetic flux generating surface of the magnetic flux generating section has a smooth structure.