JP2517559B2 - Magneto-optical information recording device - Google Patents

Description

Description: TECHNICAL FIELD The present invention irradiates a magneto-optical recording medium with a light beam and applies a bias magnetic field to an irradiation portion to record information on the medium or erase information recorded on the medium. And a device using an electromagnet as a bias magnetic field applying means.

[Prior art]

The magneto-optical information recording device has been extensively studied in recent years as a rewritable large-capacity memory. As a magneto-optical recording medium used for this purpose, a disk type (magneto-optical disk) is often used. The magneto-optical disk is formed by forming a perpendicular magnetization film on a substrate such as glass or plastic. Further, the magnetization direction of this perpendicularly magnetized film can be aligned in one direction. In recording information, the perpendicularly magnetized film is irradiated with a laser beam that is digitally modulated by an information signal to raise the temperature of the vertically magnetized film to the Curie point or higher. Then, the portion irradiated with the laser beam loses its magnetization direction, and when it is cooled, it is magnetized again by a DC bias magnetic field applied from the outside so that the magnetization direction is opposite to that of the surroundings. In this way, a signal pit sequence corresponding to the information is generated.

In order to read the information recorded on the magneto-optical disk, the reading Kerr effect that changes the direction of the polarization plane of the reflected beam by irradiating the perpendicular magnetization film with a reading laser beam and changing the magnetization direction of the perpendicular magnetization film is used. I am reading it. When erasing the recording pits, a laser beam is applied to the recording pit portion while tracking on the recording pit row, and a DC bias magnetic field in the magnetization direction opposite to the recording pit is applied to align the magnetization direction of the perpendicularly magnetized film again.

As a matter of course, it is necessary to switch the magnetization direction of the DC bias magnetic field during recording and erasing. Generally, as a method for generating a DC bias magnetic field, there are a method using a permanent magnet and a method using an electromagnet. However, the method using a permanent magnet requires a mechanism for reversing the magnetization, and it takes time to reverse the magnetization. Because of this drawback, electromagnets are often used.

FIG. 8 is a perspective view of a magneto-optical information recording apparatus using an electromagnet which has been generally used conventionally.

In the figure, the bias magnetic field applying means 21 comprises a main yoke 22, side yokes 23 and 24 arranged on both sides of the main yoke 22, and the main yoke 2.
2. A yoke plate 26 connecting one ends of the side yokes 23 and 24 and a coil 25 wound around the main yoke 22. The main yoke 22 is T-shaped for easy coil winding.

The bias magnetic field applying means 21 is arranged on the side opposite to the optical head 27 with respect to the magneto-optical disk 28 and so that the longitudinal direction of the main yoke 22 coincides with the radial direction of the magneto-optical disk 28. The optical head 27 includes a light source such as a semiconductor laser and an objective lens for condensing the light beam emitted from the light source on the magneto-optical disk 28, and is moved in the radial direction of the magneto-optical disk by a mechanism (not shown).

However, in the structure described above, the magnetic field lines emitted from the main yoke 22 pass through the air and enter the side yokes 23, 24, so that only a small amount of the magnetic flux generated by the auxiliary magnetic field applying device is recorded in the portion to be recorded on the magneto-optical disk 28. Don't concentrate
In order to obtain the required magnetic field strength, it was necessary to apply a large current or wind the coil for several hundred turns.

In addition, a large and expensive power source is required to pass a large current, and the temperature rise cannot be ignored. When the number of turns is further increased, the size of the auxiliary magnetic field applying device is inevitably increased, and the reactance of the coil is increased in accordance with the number of turns, resulting in a long time for switching from recording to erasing or vice versa. there were.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magneto-optical information recording device capable of efficiently recording or erasing by concentrating the magnetic flux of a bias magnetic field in the recording portion of a magneto-optical recording medium.

It is an object of the present invention to provide means for irradiating a magneto-optical recording medium with a light beam and a coil wound around the medium, which is provided in close proximity to a portion irradiated with the light beam and directly faces the medium through a space. Bias magnetic field applying means including a yoke having one protrusion and two second protrusions provided on both sides of the first protrusion so as to be separated from each other in the direction along the medium surface. In the information recording apparatus, each of the second protrusions of the yoke has a substantially L-shape that is bent toward the first protrusion on the side closer to the medium, and the first protrusion of the yoke is also formed. When the distance between the second magneto-optical recording medium and the magneto-optical recording medium is d, and the distance from the first protrusion on the side closer to the medium of each second protrusion of the yoke is δ, the condition 0.5d ≦ δ ≦ Achieved by being configured to satisfy 5d.

EXAMPLES Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a perspective view showing a schematic configuration of an embodiment of the magneto-optical information recording apparatus of the present invention. Here, the bias magnetic field applying means 1 is wound around the main yoke 2, the side yokes 3 and 4 arranged on both sides thereof, the main yoke 2, and the yoke plate 6 and the main yoke 2 which connect one ends of the side yokes 3 and 4. It consists of coil 5. The bias magnetic field applying means 1 is a magneto-optical disk 8
On the other hand, a space is further provided for the magneto-optical disk 8 on the opposite side of the optical head 7 for irradiating the medium with a light beam and so that the longitudinal direction of the main yoke 2 coincides with the radial direction of the magneto-optical disk 8. It is arranged to face directly through. The main yoke 2, the side yokes 3 and 4, and the yoke plates are made of magnetic material such as pure iron such as electromagnetic soft iron or iron-based alloy such as Si-Fe and Ni-Fe. Copper wire of about 0.6 mm is 300 to 1
It is wound about 000 turns and fixed with adhesive. When a current is passed through the coil 5, a DC bias magnetic field is generated in the main yoke 2 in a direction perpendicular to the medium surface of the magneto-optical disk 8. The main yoke 2 has a T-shape so that the coil 5 can be easily wound. The side yokes 3 and 4 are L-shaped with the magneto-optical recording medium side portion extending toward the main yoke side.

FIG. 2 is a sectional view of the magneto-optical information recording apparatus shown in FIG. In the figure, the shaded area shows the cross section of the magneto-optical disk 8. FIG. 3 is a graph showing the relationship between δ in FIG. 2, that is, the distance between the main yoke 2 and the side yokes 3 and 4 and the magnetic flux density B at the spot position on the magneto-optical medium. The vertical axis is the magnetic flux density B.

In FIG. 3, when δ is close to 0, the magnetic flux emitted from the main yoke 2 hardly reaches the magneto-optical medium and the side yoke
B becomes smaller because it enters 3 and 4. Further, δ = L, that is, in the case of the conventional example, on the contrary, the distance between the main yoke 2 and the side yokes 3 and 4 becomes too large, so that the magnetic flux is not concentrated and B falls.

The value δmax of δ at which the highest magnetic flux can be obtained changes depending on the distance d between the main yoke 2 and the magneto-optical medium 8 shown in FIG. 2, and also changes depending on the drive current I. FIG. 4 shows the relationship between δ and B when the value of d is changed. Also, the sixth
The figure shows the relationship between δmax and d. When d is large, that is, at a location away from the main yoke, the larger the leakage flux in the disk direction, the larger the magnetic flux density in the direction perpendicular to the disk. Therefore, the larger δ is, the larger δmax is.

FIG. 5 shows the relationship between δ and B when the current I flowing through the coil is changed, and FIG. 7 shows the relationship between δmax and I. The larger I is, the larger the generated magnetic flux is and the larger the leakage magnetic flux is. Therefore, a larger magnetic flux density can be obtained on the medium surface by increasing δ to some extent.

As described above, the value of δmax changes depending on the changes in d and I, but the minimum value of d, that is, the distance between the bias magnet and the recording medium, depends on the thickness of the transparent layer and the maximum amount of disc surface deviation to protect the recording medium. Is determined, and in order to improve efficiency, it is used near this minimum value. For example, if the thickness of the transparent layer is 1.2 mm and the maximum surface blurring amount of the disk is about 0.4 mm, d will be about 2 to 3 mm.

On the other hand, with respect to the current I flowing through the coil, δmax is the most efficient when the erasing magnetic field is generated, that is, when the maximum current is supplied.
The value of should be chosen. In this case, since the current I when the recording magnetic field is generated is smaller than that when the erasing magnetic field is generated, the efficiency is somewhat deteriorated. However, considering that a higher magnetic field strength is required at the time of erasing, when the maximum current is applied as described above. It is better to choose the optimum δmax.

The relationship between d and δmax in FIG. 6 is the case when a general erasing magnetic field (300 to 500 Gauss on the medium surface) is generated. The relationship between d and δmax at this time can be approximated to δmax = d. That is, when the erasing magnetic field is generated, the distance δ between the main yoke and the side yoke is set to the distance d between the bias magnet and the recording medium.
The maximum magnetic field is obtained when they are almost equal to. But,
The strength of the erasing magnetic field may change greatly depending on the sensitivity of the recording medium, the laser power, the configuration of the device, etc.When the change is taken into consideration, the value of δ varies from 0.5d to 5d. It is desirable to select the optimum value according to the appropriate conditions. The magnetic field strength when δ = 0.5d or δ = 5d is about 75% of the maximum magnetic field strength obtained when δ = d.

On the contrary, within this range, even if the conditions and the configuration are changed to some extent, the configuration is not extremely inefficient, and the magnetic flux can be concentrated on the surface of the magneto-optical medium quite efficiently.

Further, although the above embodiment describes the case where the disk-shaped recording medium is used, the present invention can be applied to an apparatus using a card-shaped magneto-optical recording medium. Generally, the size and configuration of the bias magnetic field applying means are determined by the shape of the recording medium used and the method of accessing the recording medium with the optical head, and the shape of the main yoke also changes variously according to the device. This is because the strength and spread of the magnetic field required on the recording medium differ subtly from device to device.
However, it is obvious that the structure of the present invention can be applied to such various magneto-optical information recording devices.

〔The invention's effect〕

As described in detail above, according to the present invention, the magnetic flux can be concentrated more simply by changing the shape of the yoke without changing the number of turns of the coil, the current value, etc., and a more efficient magneto-optical information recording apparatus is provided. Can be provided.

[Brief description of drawings]

FIG. 1 is a perspective view showing a schematic configuration of an embodiment of a magneto-optical information recording apparatus according to the present invention, FIG. 2 is a schematic sectional view of the apparatus shown in FIG. 1, and FIGS. FIG. 6 is a diagram showing the relationship between the distance between the two and the magnetic flux density in the recording portion of the medium, and FIG. 6 is a diagram showing the relationship between the distance between the protrusions that yields the highest density magnetic flux and the distance between the yoke and the medium. FIG. 7 is a diagram showing the relationship between the distance between the protrusions where the highest density magnetic flux can be obtained and the current passed through the coil, and FIG. 8 is a perspective view showing the schematic configuration of a conventional magneto-optical information recording apparatus. . 1 ... Bias magnetic field applying means, 2 ... Main yoke, 3, 4 ...
… Side yoke, 5… Coil, 6… Yoke plate, 7…
… Optical head, 8… magneto-optical disk.

Claims (1)

(57) [Claims] 1. A first coil around which a coil is provided, which is provided to face a magneto-optical recording medium with a light beam and to directly face the medium with a space in the vicinity of the irradiated portion of the light beam. Information and a bias magnetic field applying means including a yoke having two second protrusions provided on both sides of the first protrusion and separated from each other in the direction along the medium surface. In the recording apparatus, each of the second protrusions of the yoke has a substantially L-shape that is bent toward the first protrusion on the side close to the medium, and The distance from the magneto-optical recording medium is d, and the distance from each of the second protrusions of the yoke from the first protrusion on the side closer to the medium is δ.
The magneto-optical information recording apparatus is characterized in that the condition 0.5d ≦ Δ ≦ 5d is satisfied.