JPH0773536A - Magneto-optical memory method - Google Patents

Abstract

PURPOSE:To provide both functions of a high-density characteristic and a large capacity by having width of 100 to 200 times the recording track width in the radial direction of a recording carrier in a magnetic field impressing region where the magnetic field is impressed to a magneto-optical recording film. CONSTITUTION:Recording of information is executed by impressing the modulated magnetic fields inverted in polarities according to the recording information by a magnetic head 12 to the memory device from the magneto-optical recording film 903 side simultaneously with irradiating of the magneto-optical recording film 903 with a laser beam of high output from the substrate 901 side by an optical head. As a result, overwriting of fresh signals is executable while the old signals are erased. The recording density is determined by the size of the light spot. Namely, the magneto-optical memory device having the high density and large capacity of the optical disk and the overwriting function of the magnetic disk in combination is realized without substantially impairing the absence of contact which is the characteristic of optical recording.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical storage method, and more particularly to overwrite by magnetic field modulated light.
The present invention relates to a possible magneto-optical disk device.

[0002]

2. Description of the Related Art Conventionally, as an overwritable magneto-optical disk device, an IEEE Transaction on Magnetics (IEEE Transactio) has been used.
onMagnatics) MAG-20. Volume 5p. 10
No. 13 (1984), a system using two light spots, or JP-A-51-107121.
No. 59, JP-A-59-215008, JP-B-60-488.
As described in No. 06, there is a method of modulating the magnetic field applied to the recording film according to the information to be recorded. The present invention particularly relates to the latter magneto-optical storage device using the magnetic field modulation method.

[0003]

Conventionally, in an example of overwriting by a magnetic field modulation method, a magnetic field generating electromagnetic coil is installed on a disk and a modulating magnetic field is applied. The distance between the two was fixed at about 0.1 mm to 0.5 mm. In this case, the recording frequency is 0.5 MHz or less, and there is a problem that it is not possible to record a signal with a frequency of several MHz.

The object of the present invention is to solve the above problems,
It is an object of the present invention to provide a magneto-optical storage device capable of recording a signal of about several MHz and having both an overwrite function, which is an advantage of a magnetic disk, and a high density and large capacity, which are advantages of an optical disk.

[0005]

In order to achieve the above object, the present invention is characterized in that an optical head and a magnetic head are opposed to each other with a record carrier sandwiched therebetween, and a floating magnetic head is used as the magnetic head. This flying type magnetic head has a wide effective magnetic field application area (about 0.2 mm x 0.5 mm) and a large flying height (1 μm) even at a low linear velocity.
Above) It consists of a slider. Then, light is irradiated by the optical head from the substrate side of the record carrier, and a magnetic field is applied by the magnetic head from the magneto-optical recording film side.

Specifically, a disc-shaped record carrier having a transparent substrate, a magneto-optical recording film on the transparent substrate, and a protective film on the magneto-optical recording film is used, and polarity inversion or intensity modulation is performed according to recorded information. A magneto-optical storage method for recording information by applying a magnetic field to the magneto-optical recording film from the protective film side and irradiating laser light to the magneto-optical recording film from the transparent substrate side. The magnetic field application region applied to the magneto-optical recording film has a width of 100 to 200 times the recording track width in the radial direction of the record carrier.

According to another feature of the present invention, a protective film having good sliding resistance is formed on the side of the magneto-optical recording film facing the magnetic head with a thickness of, for example, 1 to 20 μm.

[0008]

The floating magnetic head used in the present invention has an effective magnetic field application area much wider than that of the conventional magnetic head. For example, if the effective magnetic field is about 0.2 mm × 0.5 mm, the narrowed spot and the magnetic head are aligned with each other. Is easy and stable against temperature changes and vibrations. Since the magnetic field application area is 100 to 200 times as wide as the recording track width in the radial direction of the record carrier, the light spot does not deviate from the magnetic field application area due to eccentricity of the disk.

If the flying height of the magnetic head is 1 μm or more, so-called head crash due to dust or the like hardly occurs, and the device can be used in the atmosphere. Furthermore, when a head core having a wide effective magnetic field application area as described above is used, the magnetic field strength is hardly attenuated even at a position 10 to 20 μm away from the end face of the head core, so that the surface of the magneto-optical recording film is about 5 to 10 μm. It is possible to form a thick protective film. Moreover, unlike conventional coated magnetic disks, etc., the protective film can be coated purely for the purpose of protection without containing magnetic powder, so the durability of the protective coat is extremely high, and the environment resistance and reliability are even higher. Can be improved.

Information is recorded by irradiating the magneto-optical recording film with a high-power laser beam from the substrate side by the optical head, and at the same time, from the magneto-optical recording film side, a modulating magnetic field whose polarity is inverted by the magnetic head according to the recorded information is irradiated. It is done by applying. As a result, the old signal can be erased and the new signal can be overwritten. The recording density is determined by the size of the light spot. That is, it is possible to realize a magneto-optical storage device having both a high density and a large capacity of an optical disc and an overwrite function of a magnetic disc, while hardly losing the non-contact characteristic of the optical recording.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIG.

In FIG. 1, reference numeral 1 is a magneto-optical disk which is a rotating record carrier, and has a magneto-optical recording medium 101 having a magneto-optical effect and a protective film 102 on a disk-shaped transparent substrate 103. For example, the light emitted from the light source composed of the semiconductor laser 2 is converted into a parallel light flux by the collimator lens 3, and enters the focusing lens 5 via the beam splitter 4. The light beam focused by the lens 5 enters the disc from the side of the disc substrate 103 and forms a minute spot having a diameter of about 1 μm on the recording film 101. The stop lens 5 follows the vertical movement of the disc 1 so that the focus is always on the recording film, and the eccentricity of the information recording track on the disc is always followed so that the spot is always on the desired track. It is attached to the actuator 6. The reflected light from the disk 1 passes through the squeezing lens 5 and is reflected by the beam splitter 4. The beam splitter 7 causes the magneto-optical signal detection optical system 8 and the optical spot control signal detection optical system 9 for detecting defocus and track shift. Be guided.

FIG. 1 shows an example of a magneto-optical signal detection system 8. This is a differential signal detection method using a λ / 2 plate 801 and a polarization beam splitter 803. The light incident on the magneto-optical signal detecting optical system 8 passes through the λ / 2 plate 801 and the lens 802, is separated into the respective polarization components of sp by the polarization beam splitter 803, and is respectively detected by the photodetectors 804 and 805. Collected. The signal converted into an electric signal by both photodetectors is differentially obtained by the differential amplifier 10 and obtained as a magneto-optical signal.

The magnetic head 12 is arranged on the recording film side so as to face the optical head 11 with the disk 1 interposed therebetween. In FIG. 1, for the sake of explanation, the magnetic head is rotated 90 ° in the plane of the disk from the actual arrangement and is enlarged as a bird's eye view. The magnetic head 12 is composed of a coil portion for applying a magnetic field to the recording film and a slider portion for levitating the entire head, as will be described later, and is levitated by air pressure due to the disc rotation while the disc is rotating. The flying height is 1 μm or more (preferably 2 μm or more). With this amount of levitation,
A head crash due to dust or the like, which is a problem with a magnetic disk, does not occur, and it is possible to use the apparatus in the atmosphere and replace the medium.

The magnetic head 12 is also pressed against the disk 1 by a support spring 13 with a load of about 5 to 10 g. The so-called CSS (C (C) which keeps the magnetic head in contact with the disk when the disk starts and stops
Either the ontact start (Stop) method or the method in which the magnetic head is removed from the disk until the disk rotation speed reaches a constant value may be used. Just disk 1
When exchanging the magnetic head 12, the moving mechanism 16 for moving the magnetic head 12 up and down is necessary regardless of the above two methods.

The magnetic head 12 is further integrally connected to the optical head 11 by a support arm 15 so that it can be interlocked with the optical head. The magnetic head 12 has a constant distance between them, and at the same time, it is directly above the optical spot on the disk. Install the magnetic head on. It is not always necessary to integrate the two as shown in the figure, but if they are not integrally connected, when moving the recording position in the disk radial direction, a means for keeping the distance between them constant and a magnetic head directly above the optical spot. A magnetic head moving means for installing the magnetic head is required.

The optical head 11 is moved in the disk radial direction by, for example, a linear motor or a step motor.

FIG. 2 shows a method of recording information. In order to record information, the semiconductor laser 2 is made to continuously emit light at a high output as shown in FIG.
Is heated to near the Curie temperature to reduce the coercive force of the part irradiated with light. At this time, the magnetic head 12 is driven by the magnetic head drive circuit 14 to record information (see FIG.
The modulation magnetic field whose polarity is inverted according to FIG.
Information is recorded by applying (c)) to the magneto-optical recording film 101. The recording state is shown in FIG. If it is necessary to change the applied magnetic field strength in order to keep the recording conditions constant, regardless of the inner and outer circumferences of the disc and the laser output fluctuation,
In addition to polarity reversal, a DC bias component is added to the intensity modulation or magnetic field. According to this method, even if new recording is performed on a portion where information is recorded, old recorded information does not remain, and it is possible to erase old information by overwriting, that is, by overwriting information. Becomes

Now, an embodiment of the magnetic head and the disk, which are the main constituent elements of this embodiment, will be described in detail.

As the magnetic head 12, a levitation type magnetic head which has a large levitation amount even if the linear velocity is slow and has a wide effective magnetic field application region is used. The flying height is 1 μm or more (preferably 2 μm or more) from the viewpoint of preventing head crash due to dust and the like,
From the viewpoint of aligning the light spot and the magnetic head, the effective magnetic field application area of the head core is 0.1 mm × 0.1 mm or more and 1 mm or more.
X1 mm or less, preferably 0.1 mm x 0.1 mm or more, 0.2 m
m x 0.5 mm or less.

FIG. 3 shows an example of the magnetic head used in the present invention. FIG. 6C is a diagram showing a slider sliding surface.
The entire surface facing the disk is a sliding surface, and two substantially circular through holes are provided on the central axis AA 'of the slider 301 along the disk traveling direction. As a result, the area of the sliding surface that contributes to levitation can be made larger than that of the conventional magnetic head shown in FIG. Also, since the air pressure distribution for flying is as shown in the side of FIG. 6C, the slider is supported at four points P _{1 to} P _{4 in} the figure, and pitching or rolling is prevented. And stable levitation can be realized. The through hole may be a substantially circular recess. At this time, the depth of the recess is shown in FIG.
Set so that the air pressure distribution shown in is obtained. If this slider is used, for example, the outer dimensions of the sliding surface are 3 mm x 4 m
When m, the hole diameter is 0.6 mm, and the load is 5 g, a flying height of 2 μm can be obtained even if the disk peripheral velocity is about 3 m / sec, as shown in FIG. In the above example, the number of circular recesses or through holes is two, but it may be one as shown in FIG. Further, the shape of the recess or hole does not necessarily have to be circular, such as oval or rectangular.

The magnetic field to the recording film is applied by the coil 302 provided at the tip of the air outflow end. The coil magnetic core is a magnetic material such as Mn-Zn ferrite, and may be integrally machined with the slider or may be machined separately from the magnetic core and the coil portion and then combined with the slider. Particularly in the latter case, the slider does not have to be a magnetic material such as Mn-Zn ferrite, but may be a non-magnetic material such as ceramic.

When a magnetic material is used as the slider material, the leaking magnetic field of the actuator 6 is concentrated on the slider side, the net magnetic field strength applied to the recording film is reduced, and the magnetic field and the leaking magnetic field generated in the magnetic core portion 302 are reduced. Vibration of the magnetic head or the like may occur due to the interaction with the magnetic field. However, the use of a non-magnetic slider also has the effect of preventing the above phenomenon.

Further, the position to which the magnetic field is applied does not necessarily have to be at the outflow end, and may be arranged inside the slider as shown in FIG. Further, in this case, it is also effective to use a non-magnetic ceramic or the like as the slider 301 and use only a magnetic material for the coil magnetic core portion 302, or to use an air-core coil. With an air core coil,
Since the inductance of the magnetic head as a whole can be reduced, the frequency response of the magnetic head can be improved as described later.

The area of the effective magnetic field application area at the tip of the coil is determined by (i) magnetic head alignment accuracy, (ii) disk eccentricity, (ii) magnetic head frequency response, etc. (i), ( ii) It is required to have a larger area, but since the inductance increases, the frequency response of (iii) deteriorates. For example, 0.2mm in the circumferential direction
It is preferably about 0.5 mm to 0.1 mm × 0.1 mm in the radial direction. The former can handle a recording frequency of 3 to 5 MHz and the latter a recording frequency of about 5 to 10 MHz.

In the former example, the area is wider in the radial direction than in the disk circumferential direction. This is to prevent the light spot from deviating from the effective magnetic field application area even if the light spot moves in the radial direction due to the disk eccentricity. As shown in FIG. 1, the magnetic head 12 is fixed to the optical head 11 by the support arm 15 and moves in the disk radial direction in conjunction with the optical head. If the magnetic head 12 is also provided with a mechanism that follows the disk eccentricity, the magnetic field application area can be made small, but in this case, a position control mechanism for the magnetic head is required in addition to the optical head. However, the device becomes complicated and expensive. Therefore, in the present embodiment, in order to make the device configuration simple and inexpensive, this is dealt with by providing an effective magnetic field application region that is wider in the radial direction than in the disk circumferential direction. Further, when the optical head is discontinuously moved by, for example, a step motor or the like, the amount of movement of the narrowed spot in the radial direction becomes larger than the disk eccentricity, so it is necessary to make the radial direction wider than the disk eccentricity. In a magnetic disk or a floppy disk, the magnetic field application area by the magnetic head corresponds to the recording track width, but in the case of the magnetic head used for the magneto-optical disk as in this embodiment, the magnetic field application area is It is 100 to 200 times as wide as the recording track width.

The magnetic field application region as described above is 50 to 100 times wider than the magnetic head for a magnetic disk. Therefore, the rate of decrease of the magnetic field vertical component with respect to the distance from the head is much smaller than that of the magnetic disk head. For example, in the case of a magnetic head having a magnetic field application area of 0.5 mm × 0.2 mm, as shown in FIG.
The decrease in the vertical component of the magnetic field is 2 even at a position separated by 0 μm.
It is about 3%.

When the magnetic field application area is widened, the decrease in the magnetic field strength at a position of several tens of μm from the end face of the magnetic head can be made smaller than that in the example shown in the figure, but the frequency characteristic deteriorates. In order to realize a recording frequency of several MHz, the magnetic field application area is preferably 0.5 mm × 0.2 mm or less, and the distance between the magneto-optical recording film and the magnetic head is 3 mm.
It is preferably 0 μm or less. The above points are important in determining the disc structure in consideration of the sliding resistance. In addition, the fluctuation of the magnetic field strength due to the vertical movement of the magnetic head 12 is 1
Even if it is about μm, it does not pose a problem like a magnetic disk.

FIG. 9 shows an example of the structure of the disk used in the present invention. This disc is for single-sided recording, and has a substrate 901.
Light is irradiated from the side, and a magnetic field is applied from the recording film 903 side. The substrate 901 is made of glass or plastic having a thickness of about 1.2 mm. A magneto-optical recording film layer (for example, a TbFeCo perpendicular magnetization film) 903 having a thickness of about 1000Å is sandwiched,
On the substrate side, an enhancement film (about 1
000Å, for example, Si ₃ N ₄ , SiO, etc.) 902, and a protective film (about 2000 Å, for example, Si ₃ N ₄ , SiO, etc.) 904 is provided on the other surface to improve corrosion resistance and oxidation resistance. . A protective coat 905 for improving the sliding resistance with respect to the magnetic head is formed thereon in the range of about 1 to 20 μm, preferably about 5 to 10 μm. At this time, the recording film 903
The distance between the magnetic head 12 and the magnetic head 12 is about 10 to 20 μm, but unlike the magnetic disk as shown in FIG. 8, the magnetic field strength does not decrease at this distance.

As the protective coat 905, for example, an ultraviolet curable resin is used. It is also possible to mix a so-called filler or lubricant such as Al ₂ O ₃ with the ultraviolet curable resin. For example, when a spherical sliding test was conducted using a mixture of an ultraviolet curable resin and a filler, it was possible to achieve a sliding count of 1 million or more. In the case of magneto-optical disk, recording / reproducing /
Since the erasing characteristics are not affected, the protective coat can be thickened as described above, the life of the disk or the environment resistance can be improved, and the reliability of the device can be improved.

Further, the disk 1 is replaceable and is housed in a cartridge 906 as shown in FIG. A dustproof mechanism 907 such as linen paper is provided inside the cartridge 906 so as to face the protective coat of the disc and to remove dust adhering to the protective coat.

Next, FIG. 11 shows a second embodiment of the present invention. This is an example in which a laser array in which two laser chips are housed in one package is used as the laser light source 2. However, the support spring 13, the support arm 15, and the magnetic head moving device 16 shown in FIG. 1 are omitted for simplicity. Further, in FIG. 6A, the positional relationship of the narrowed spots on the disc is shown rotated by 90 ° in the disc surface for the same explanation as in FIG. As shown in FIG. 2B, a semiconductor laser array in which two laser chips LD1 and LD2 having different wavelengths are mounted in one package with their active layers facing each other is used as a light source. LD1 has a wavelength of 780 nm
Is a low-power, low-noise laser used for reproducing magneto-optical signals and controlling light spots. On the other hand, the LD2 is a high-power laser with a wavelength of 830 nm, and is used for recording / erasing a signal. On the other hand, the LD2 is a high-power laser with a wavelength of 830 nm, and is used for recording / erasing a signal. As for the positional relationship between the light spots SP1 (wavelength 780 nm) and SP2 (wavelength 860 nm) formed by both laser light sources on the disc, the spot SP2 precedes the spot SP2 on the same track as shown in FIG. As a result, it is possible to perform the recording at the spot SP2 and the error check at the spot SP1. The error check is performed by comparing the recording signal with the magneto-optical signal reproduced by the spot SP2 by the comparator 17. The result of the comparison is input to the controller 18, and if a discrepancy, that is, an error occurs between the above two signals, an operation such as re-recording is performed. In this embodiment, the signal before the input of the magnetic head drive circuit 14 is used as the original recording signal to be compared, but the magnetic head drive circuit 14 is used.
The magnetic head drive current that is the output of the above may be used.

Conventionally, in the magneto-optical disk, in order to rewrite recorded information, one rotation of the disk was required in the order of erasing / recording / checking, for a total of three rotations. Since the above three operations can be performed in one rotation, the effective data recording time can be greatly shortened.

[0034]

As described above, according to the present invention, it is possible to achieve high density and large capacity of an optical disk without significantly impairing the non-contact recording / reproducing / erasing which is a feature of optical recording.
It is possible to realize a magneto-optical recording device having both a high speed and overwrite function of a magnetic disk, which is extremely effective for improving the performance of the optical disk.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing an information recording operation in the present invention.

FIG. 3 is a diagram showing a structural example of a magnetic head used in the present invention.

FIG. 4 is a trihedral view showing a magnetic head structure.

FIG. 5 is a graph showing an example of the flying characteristics of the flying magnetic head used in the present invention.

FIG. 6 is a plan view showing an example of a magnetic head used in the present invention.

FIG. 7 is a trihedral view showing an example of a magnetic head used in the present invention.

FIG. 8 is a graph showing an example of magnetic field intensity distribution generated by the magnetic head used in the present invention.

FIG. 9 is a sectional view showing one structural example of a magneto-optical disk used in the present invention.

FIG. 10 is a diagram showing a structural example of a disc cartridge.

FIG. 11 is a block diagram showing a second embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Disk, 2 ... Semiconductor laser, 5 ... Focusing lens, 8 ... Magneto-optical signal detection optical system, 9 ... Optical point control signal detection optical system, 11 ... Optical head, 12 ... Magnetic head, 301 ...
Slider, 302 ... Coil, 901 ... Disk substrate, 9
Reference numeral 03 ... Magneto-optical recording film, 905 ... Protective coat, 14 ... Wavelength separation filter, LD1 ... Signal reproducing laser chip, LD
2 ... Laser chip for signal recording.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Toyoharu Okuwaki, 1-280 Higashi Koikeku, Kokubunji City, Tokyo Metropolitan Research Laboratory, Hitachi Ltd. (72) Yoichi Kawakubo 1-280, Higashi Koikeku, Kokubunji, Tokyo Hitachi Ltd. (72) Inventor Yoshinori Takeuchi, 502 Jinritsucho, Tsuchiura-shi, Ibaraki, Hiritsu Seisakusho Co., Ltd. (72) Inventor, Yuzo Yamaguchi, 502, Jinritsucho, Tsuchiura-shi, Ibaraki, Hiritseki, Co.

Claims (8)

[Claims] 1. A transparent substrate, a magneto-optical recording film on the transparent substrate,
A disc-shaped record carrier having a protective film on the magneto-optical recording film is used, and a magnetic field whose polarity is inverted or intensity-modulated according to recorded information is applied to the magneto-optical recording film from the protective film side, and a laser beam is applied. Is a magneto-optical recording method for recording information by irradiating the magneto-optical recording film from the transparent substrate side, wherein a magnetic field application region applied to the magneto-optical recording film at the time of recording or erasing information is A magneto-optical storage method having a recording track width of 100 to 200 times in a radial direction of a record carrier. 2. The magneto-optical storage method according to claim 1, wherein the magnetic field application region is wider in the radial direction than in the circumferential direction of the disk-shaped record carrier. 3. The magneto-optical storage method according to claim 1, wherein the area of the magnetic field application region is at least 0.1 mm × 0.1 mm. 4. The magnetic field is applied by magnetic field applying means,
4. The magneto-optical storage method according to claim 1, wherein the reduction of the magnetic field vertical component at a position 100 μm away from the end face of the magnetic field applying means is 30% or less. 5. The magnetic field is applied by magnetic field applying means,
4. The reduction of the magnetic field vertical component at a position 50 μm away from the end face of the magnetic field applying means is 10% or less.
A magneto-optical storage method according to any one of the above. 6. The thickness of the protective film is 1 μm or more and 20 μm or more.
The magneto-optical storage method according to any one of claims 1 to 5, which is as follows. 7. The magneto-optical storage method according to claim 1, wherein the record carrier is housed in a cartridge provided with a dustproof mechanism facing the protective film and is replaceable. 8. The magneto-optical storage method according to claim 1, wherein the laser light is emitted from a laser array light source in which two semiconductor laser chips are housed in the same package.