JPH0317846A - Magneto-optical recorder - Google Patents

Abstract

PURPOSE:To make it possible to perform overwriting by one directional pulse magnetic field by making the direction of the component of a leakage magnetic field from an objective lens driving means which is orthogonally crossed with a magneto-optical recording medium opposite to the initial magnetizing direction of the magneto-optical recording medium. CONSTITUTION:It is possible to erase only by the leakage magnetic field 5 from a lens actuator 3 and a diamagnetic field from the peripheral part of the heating part of a perpendicularly magnetized film 4 without using the magnetic field generated by an external magnetic field generating device 1. But, in this case, very large magnetic field is necessary for the magnetic field 5. Then, the leakage magnetic field 5 of the actuator 3 which is made to be in the direction of performing recording (the direction opposite to the initial magnetization direction at the time of overwriting) can be more effectively used. And by making the magnetic field 5 and the diamagnetic field 6 from the peripheral part of the recording part act in the same direction, the magnetic field necessary for the inversion of magnetization can be given to the recording part, so that the magnetic recording can be performed without using the magnetic field from the device 1. And then, at the time of erasing the recorded information (the initial magnetization direction at the time of overwriting), the magnetic field is impressed on the erasing direction by the device 1.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for irradiating a magneto-optical recording medium with a laser beam,
The present invention relates to a magneto-optical recording device that records information by modulating either the intensity of a light beam or an applied magnetic field, or both, according to a recording signal.

[Conventional technology]

A magneto-optical recording medium in which a perpendicularly magnetized film is laminated on a substrate is irradiated with a laser beam using an objective lens, and a magnetic field is applied to the irradiated portion of the light beam by a magnetic field generating means such as an electromagnet. Magneto-optical recording devices are known that record information by modulating either the optical intensity or the applied magnetic field, or both, according to the recording signal. In such a magneto-optical recording device, the magneto-optical recording medium (for example, a magneto-optical disk) is formed by laminating a perpendicular magnetization film on a light-transmitting substrate, and the magnetization direction of the perpendicular magnetization film 4 is as follows. In an unrecorded state or an erased state, as schematically shown in FIG. 1, the entire region of the perpendicularly magnetized film has one direction {1! (for example, in the direction of the arrow in the figure). In addition, when recording information, a laser beam is irradiated onto the recording part of the perpendicularly magnetized film 4, and the irradiated part heats the magnetized film to a temperature near its Curie point (ferromagnetic Curie point), and also generates a magnetic field. The device applies an external magnetic field to the recording section, and by the interaction of the external magnetic field and the demagnetizing field created by the magnetization around the heated section, the direction of magnetization of the heated section is reversed according to the recorded information, and information is recorded. FIG. 5 schematically shows the magnetization state after this recording, and shows a state in which the magnetization has been reversed in the recording area 4A. Note that the reproduction of the binary information (representing llPjj''011 depending on the direction of magnetization) recorded on the magneto-optical recording medium as described above is performed using magneto-optic effects such as the Rikichi effect and the Faraday effect. This is done by detecting the direction of magnetization.

[Problem to be solved by the invention]

By the way, in the above-mentioned magneto-optical recording device, when performing so-called overwriting, in which the magnetization direction is rewritten to the recorded state by overwriting, the rewriting can be performed efficiently since no special time is required for erasing. It has the advantage of being able to The magnetic field modulation method is well known as a method for performing such overwriting. However, it has not been put into practical use due to various problems. One problem is that with the generally considered overwriting method using the magnetic field modulation method, for example, it is difficult to obtain the second recording state shown in FIG. 6 from the first recording state shown in FIG. Next, the magnetization state of the recording area 4A in FIG. 5 is reversed and erased. On the other hand, in regions 4B and 4C, recording and erasing magnetic fields are generated in opposite directions in the thickness direction of the magnetized film 4, that is, with both positive and negative polarities, in response to the recorded information signal, causing new magnetization reversal. This means that it is necessary to do so. However, in order to make such reversal possible at a high frequency, it is necessary to reduce the number of turns of the electromagnet coil of this magnetic field generating means to reduce the inductance. It becomes necessary to use a large current. However, when the current is made to be a large current in this way, not only does the problem of heat generation due to Joule heat occur, but also it is necessary to make such a large current swing at a high frequency and with both positive and negative polarities reversed. Such an inductive power supply consumes a large amount of power and must be large in size, and furthermore, in this case, it is extremely difficult to obtain one with excellent frequency characteristics. In addition, it is desirable that the level of the magnetic field of both positive and negative polarities for overwriting for recording and erasing described above be relatively large, and a magnetic field generating means for obtaining this external magnetic field is required to have a large output. , the problem of power consumption increases. By the way, a pickup system of a magneto-optical recording device includes an objective lens that focuses a light beam on a magneto-optical recording medium, a permanent magnet, and an electromagnetic coil, and an objective lens driving means that drives the objective lens at least in the optical axis direction. (hereinafter referred to as a lens actuator), and at least focusing adjustment is performed by the lens actuator. Here, the lens actuator has a magnet, such as a permanent magnet, that actually generates a DC magnetic field in a direction perpendicular to the surface of the magneto-optical recording medium, and a forcing servo is installed in the magnetic circuit including this magnet. A moving coil that conducts current is arranged, and the moving coil moves in the optical axis direction in response to the servo current. Such lens actuators are usually magnetically shielded, and consideration is given to reducing the leakage magnetic field from the actuator as much as possible. The problem is that it is not possible. By the way, when the leakage magnetic field of the lens actuator is not applied to the recording medium, the strength of the external magnetic field required for recording and erasing (initial magnetization direction in overwriting) varies depending on the material of the medium and the power of the laser beam, but in general, Erasing requires a stronger magnetic field than recording. The reason for this is that the demagnetizing field (leakage field) from the surrounding magnetized film acts on the magnetized film that is heated during recording, and that demagnetizing field helps reverse the magnetization. Conventionally, the direction of the leakage magnetic field applied from the lens actuator to the magneto-optical recording medium and the initial magnetization (erasing) of the magneto-optical recording medium have been investigated.
Although the relationship with the direction was not specified, for example, in Japanese Patent Application Laid-Open No. 63-66747, the direction of the external magnetic field and the direction of the leakage magnetic field of the lens actuator are made to be the same during erasing, and the leakage magnetic field is used as the erase magnetic field. As shown in FIGS. 7 and 8, a magneto-optical recording device has been proposed in which the initial magnetization (erasing) direction of the perpendicular magnetization film 4 of the magneto-optical recording medium is It can be considered that the direction of the leakage magnetic field 5 from the lens actuator 3 is the same. However, since the magnetization direction is reversed with both positive and negative polarity by the applied magnetic field from the magnetic field generating means 1, the magnetic field generating means 1 has a high output power, similar to the above-mentioned one that does not utilize the leakage magnetic field. However, problems such as power consumption remain unsolved. The present invention has been made in view of the above circumstances, and aims to provide a magneto-optical recording device which solves the above-mentioned problems and enables overwriting by generating a pulsed magnetic field in only one direction. ．． [Means for Solving the Problems] In order to achieve the above object, the present invention includes an objective lens for condensing a light beam on a magneto-optical recording medium, a permanent magnet, and an electromagnetic coil, and the objective lens is arranged at least along the optical axis. an objective lens driving means for moving the objective lens in a direction; and a magnetic field generating means for applying a magnetic field to the magneto-optical recording medium, and modulating either the optical intensity of the light beam or the applied magnetic field, or both, according to the recording signal. In a magneto-optical recording device that records information by It is characterized by being structured so that [Function] According to the present invention, the direction of the orthogonal component of the leakage magnetic field from the objective lens driving means with respect to the magneto-optical recording medium is configured to be opposite to the initial magnetization direction of the magneto-optical recording medium. , the leakage magnetic field can be made to act as an external magnetic field during recording on a magneto-optical recording medium.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to the drawings. FIG. 1 and FIG. 2 are schematic diagrams of the main parts of a magneto-optical recording device showing an embodiment of the present invention, with FIG. 1 showing the state during recording and FIG. 2 showing the state during erasing, respectively. In the figure, reference numeral 1 denotes an external magnetic field generator including an electromagnet, 2 an objective lens for condensing a laser beam onto a magneto-optical recording medium, and 3 a permanent magnet and a coil. A lens actuator is used to perform focusing control by moving the lens 2 in the direction of its front axis. Reference numeral 4 indicates a perpendicular magnetization film of a magneto-optical recording medium, and reference numeral 5 indicates a leakage magnetic field from the lens actuator 3. In FIGS. 1 and 2, the magneto-optical recording medium is initially magnetized downward in the figure in its initial state, that is, in the state at the time of erasing. Further, the direction in which the leakage magnetic field 5 from the lens actuator 3 is applied to the perpendicular magnetization film 4 of the magneto-optical recording medium is opposite to the initial magnetization direction of the perpendicular magnetization film 4. Here, the leakage magnetic field 5 of the lens actuator 3 is a magnetic field perpendicular to the perpendicular magnetization film 4 of the magneto-optical recording medium. Furthermore, the first
In the example shown in the figure and FIG. 2, the initial magnetization direction of the magneto-optical recording medium is directed downward with respect to the figure, and the leakage magnetic field 5 of the lens actuator 3 is directed upward with respect to the figure, but the directions may be reversed. Now, the present invention provides a magneto-optical recording device having the configuration shown in FIGS.
The leakage magnetic field 5 from the lens actuator 3 is effectively used as a recording magnetic field. Here, the demagnetizing field 6 from the periphery of the magnetized film heated by the laser beam focused by the objective lens 2 is:
In order to use the leakage magnetic field 5 from the lens actuator 3 as a recording magnetic field, it is necessary to set the magnetic field direction of the leakage magnetic field 5 in the recording direction. By setting the magnetic field 5 and the demagnetizing field 6 in the same direction, it becomes possible to perform recording (reversal of magnetization) without using the magnetic field from the external magnetic field generator 1. By the way, when the leakage magnetic field 5 from the lens actuator 3 and the direction of the demagnetizing field 6 from around the heating part of the perpendicularly magnetized film 4 are opposite as in the conventional device, the leakage magnetic field S from the lens actuator 3 and Demagnetizing field from around the heating part 6
However, in this case, a very large magnetic field is required as the leakage magnetic field 5. However, when the leakage magnetic field is increased, the structure of the lens actuator 3 becomes complicated and the weight increases, resulting in drawbacks such as slow access time. Therefore, the leakage magnetic field of the lens actuator can be used more effectively if it is directed in the recording direction (in the direction opposite to the initial magnetization direction during overwriting) as in the present invention. By causing this leakage magnetic field 5 and the demagnetizing field from around the recording section to act in the same direction, the magnetic field necessary for magnetization reversal can be applied to the recording section.
This means that magnetic recording can be performed without using the magnetic field from the external magnetic field generator 1. Next, when erasing the recorded information (in the initial magnetization direction in the case of overwriting), the external magnetic field generator 1 applies a magnetic field in the erasing direction. Here, FIG. 3 shows the application state of the magnetic field during recording/erasing or overwriting. Here, Figure 3 (A) shows that when the magneto-optical recording medium is heated, the leakage magnetic field a of the lens actuator and the demagnetizing field b around the heated magnetized film (recording section) are applied to the heated magnetized film. This is a diagram showing In Fig. 3, l#+rl of the magnetic field indicates the recording direction (in overwriting, the direction opposite to the initial magnetization direction), and 71 of the magnetic field
-It indicates the erasing direction (in overwriting, the same direction as the initial magnetization direction). Here, when the leakage magnetic field a of the lens actuator and the demagnetizing field b around the heated magnetized film are applied to the heated magnetized film as shown in FIG. 3(A), the magnetic field shown in FIG. 3(B) An external magnetic field generator i! generates a unidirectional pulsed magnetic field in the erase direction only! ! 1, information can be recorded/erased (or overwritten) as shown in FIG. 3(C). Note that the leakage magnetic field from the lens actuator 3 applied to the magneto-optical recording medium can be adjusted by changing the size and arrangement of the permanent magnet in the actuator. Now, as explained above, in the present invention, a portion of the magnetic field leaking from the lens actuator 3 in a direction perpendicular to the recording medium is used as a recording magnetic field, and the magnetic field direction of this leaking magnetic field and the initial state of the recording medium are By making the magnetization direction (magnetization direction during erasing) opposite, information can be recorded without using a magnetic field from an external magnetic field generator. In other words, by directing the leakage magnetic field from the lens actuator in the recording direction rather than in the erasing direction, it is possible to suppress the complexity of the structure and increase in weight of the lens actuator, and prevent the impact on access time. In addition, the external magnetic field generator 1 does not need to reverse the magnetic field between recording and erasing, and only generates a pulsed magnetic field in one channel (one direction) during erasing, so that the direction of magnetization of the recording medium is reversed. It is possible to form a magnetization pattern between the recording part and the recording part, and it is possible to easily perform so-called overwriting. ! The configuration of the source section can be simplified. [Effects of the Invention] As described above with reference to the drawings, according to the present invention, the direction of the orthogonal force of the leakage magnetic field from the objective lens driving means with respect to the magneto-optical recording medium and the initial magnetization of the magneto-optical recording medium can be adjusted. By configuring the magnetization direction (or magnetization direction during erasing) to be opposite, the leakage magnetic field can be made to act as an external magnetic field during recording on the magneto-optical recording medium. Therefore, in the magneto-optical recording device according to the present invention,
The external magnetic field generator only needs to generate a magnetic field during erasing, and overwriting can be performed by generating a pulsed magnetic field in only one direction. problems and problems with frequency characteristics are resolved.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are schematic diagrams of the main parts of a magneto-optical recording device showing an embodiment of the present invention, with FIG. 1 showing the state during recording and FIG. 2 showing the state during erasing, respectively. This is a diagram. Figure 3 is
Figures 4 to 6 are diagrams for explaining the state of application of a magnetic field during recording/erasing or overwriting by the magneto-optical recording device shown in Figures 2 and 2, and Figures 4 to 6 are diagrams for explaining the recording state of the magneto-optical recording medium. , FIG. 7, and FIG. 8 are schematic main part configuration diagrams of a magneto-optical recording device showing an example of the prior art,
Fig. 7 shows the state during recording, and Fig. 8 shows the state during erasing. 1...External magnetic field generator, 2...Objective lens,
3... Objective lens driving means, 4... Perpendicular magnetization film of magneto-optical recording medium, 5... Leakage magnetic field from the objective lens driving means, 6... Reversal magnetic field, 7...・Magnetic field applied by an external magnetic field generator.

Claims (1)

[Claims] an objective lens that focuses a light beam on a magneto-optical recording medium; an objective lens driving means that includes a permanent magnet and an electromagnetic coil and drives the objective lens at least in the optical axis direction; and a magnetic field that applies a magnetic field to the magneto-optical recording medium. In the magneto-optical recording device, which records information by modulating either the light intensity of the light beam or the applied magnetic field, or both, according to a recording signal, the magnetic field generating means is provided with a magnetic field generating means. A magneto-optical recording device characterized in that the direction of the component of the leakage magnetic field orthogonal to the recording medium and the initial magnetization direction of the magneto-optical recording medium are opposite directions.