JPH04162231A - Magnetooptical recording system and magnetic head used for the system - Google Patents

Abstract

PURPOSE:To enable recording in a low magnetic field by sliding a magnetic head against a magnetooptical recording medium through an abrasion-resistant protective film having specific film thickness. CONSTITUTION:A magnetic head 3 is slid against magnetooptical recording medium 1 with an abrasion-resistance protective film 7 having film thickness of 0.01-50mum through the abrasion-resistant protective film 7. Since the magnetic head 3 is slid against the magnetooptical recording medium 1, a distance to a recording magnetic layer 8 is reduced sufficiently, and a magnetic field generated by the magnetic head 3 can be small. Since the magnetic head 3 is slid through the abrasion-resistant protective film 7 formed onto the magnetooptical recording medium 1, a special servo, etc., are unnecessitated, and trouble such as crush is also eliminated. Accordingly, low magnetic-field recording is enabled without requiring a flying head and a complicate servo.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a novel magneto-optical recording method in which a magnetic head slides against a magneto-optical recording medium, and further relates to a new magneto-optical recording method. This relates to the magnetic head used.

[Summary of the invention]

The present invention provides a new magneto-optical recording method that allows recording in a low magnetic field by sliding a magnetic head against a magneto-optical recording medium through a wear-resistant protective film with a thickness of 0.01 to 50 μm. It is something to do.

Furthermore, the present invention provides a curved surface for the entrance end of the magneto-optical recording medium, and provides a magnetic field generating means at a position that is set back from the maximum protrusion on the magneto-optical recording medium side. The present invention provides a magnetic head that slides smoothly.

[Conventional technology]

In the magneto-optical recording method, the temperature of a part of a magnetic thin film is raised above the Curie point or temperature compensation point, and the coercive force in this part is extinguished to reverse the direction of magnetization in the direction of the externally applied recording magnetic field. The basic principle is that optical file systems, computer external storage devices, audio,
It is being put into practical use in video information recording devices and the like.

The magneto-optical recording medium used in this magneto-optical recording method consists of a recording magnetic layer (having an axis of easy magnetization perpendicular to the film surface and having a large magneto-optic effect) on the entire surface of a transparent substrate made of polycarbonate or the like. For example, a recording section is formed by laminating a rare earth-transition metal alloy amorphous thin M), a reflective layer, and a dielectric layer, and the signal is read by irradiating laser light from the transparent substrate side. Are known.

[Problem to be solved by the invention]

By the way, magneto-optical recording methods can be broadly divided into optical modulation methods and magnetic field modulation methods, and because they can be overridden, expectations for the magnetic field modulation methods are increasing.

The above-mentioned magnetic field modulation method writes information signals in a magnetic thin film by reversing the applied magnetic field at high speed, and the application of the magnetic field is usually performed by a magnetic head having a magnetic field generating means.

In this case, a magnetic head that applies a high-speed switching magnetic field can only generate a very small magnetic field due to various restrictions, and it is necessary to move the magnetic head as close to the recording magnetic layer as possible. For example, in the case of a magneto-optical disk for data recording, the distance between the magneto-optical disk surface and the magnetic head is set to 0. Must be IEII 11 or lower.

When the distance between the magneto-optical disk and the magnetic head decreases in this way, it is necessary to improve the dimensional accuracy of the magneto-optical disk to suppress surface runout in order to prevent crashes of the magnetic head.

However, with a magneto-optical disk made of a substrate or polycarbonate, there is a limit to the suppression of surface runout, so a servo is applied to keep the distance between the magnetic head and the magneto-optical disk constant, such as the focus servo of an optical pickup. Or, like hard disks, a so-called flying head will have to be adopted.

However, especially in a low-speed rotation system of about 300 to 600 rpm, a flying head cannot be used, and a complicated servo is required to control the distance.

Further, in the case of a high-speed rotation system with a rotational speed of about 360 rpm, it is possible to employ a flying head in which the magnetic head floats via an air bearing, but it is necessary to avoid the problem of crashes during start and stop.

Furthermore, even when using servo to maintain a constant distance from the disk, or when using a flying head, the distance between the magnetic head and the magneto-optical disk must be maintained. Also on the magneto-optical disk side, the recording magnetic layer must be a magnetic thin film that allows writing in a low magnetic field.

Therefore, the present invention was proposed in view of the above-mentioned conventional situation, and provides a magneto-optical recording system capable of performing low magnetic field recording without requiring a flying head or complicated servo. A further object of the present invention is to provide a magnetic head suitable for use in such a magneto-optical recording system.

[Means to solve the problem]

In order to achieve the above-mentioned object, the magneto-optical recording method of the present invention provides a magneto-optical recording medium having a wear-resistant protective film with a thickness of 0.01 to 50 μm, in which a magnetic head is coated with the wear-resistant protective film. It is characterized by being slid through.

Furthermore, the magnetic head of the present invention is characterized in that at least the end on the entrance side to the magneto-optical recording medium has a curved shape, and the magnetic field generating means is provided at a position set back from the largest protrusion on the magneto-optical recording medium side. That is.

[Effect]

In the present invention, since the magnetic head is made to slide with respect to the magneto-optical recording medium, the distance to the recording magnetic layer is sufficiently small, and the magnetic field generated from the magnetic head can be small. Furthermore, since the magnetic head slides through a wear-resistant protective film formed on the magneto-optical recording medium, there is no need for a special servo or the like, and problems such as crashes are eliminated.

On the other hand, since the magnetic head of the present invention has a curved end on the entrance side to the magneto-optical recording medium, it slides smoothly and does not damage the magneto-optical recording medium. In addition, since the magnetic field generating means is installed at a position slightly set back from the sliding surface, the magnetic field generating means will not be damaged by sliding, and the sliding surface can be flattened, allowing load fluctuations. This eliminates the increase in errors due to

〔Example〕

Embodiments to which the present invention is applied will be described in detail below with reference to the drawings.

FIG. 1 shows a schematic configuration of a magneto-optical recording device. In this magneto-optical recording device, an optical pickup (2) and a magnetic head (3) are placed facing each other with a magneto-optical disk (1) in between. ing.

As shown in FIG. 2, the magneto-optical disk (1) has a substrate (
A recording section (5) is laminated on the -main surface of 4), and the surface of this recording section (5) is further covered with an ultraviolet curing resin layer (6) and an abrasion-resistant protective film (7).

The substrate (4) is a disc-shaped transparent substrate with a thickness of about a few nm (for example, 2 nm), and its material includes plastic materials such as acrylic resin, polycarbonate resin, polyolefin resin, and epoxy resin. , glass, etc. are also used.

In addition, on the surface of this substrate (4) on the side where the recording section (5) is provided, there are usually guide grooves and addresses having a depth of approximately one-fourth of the wavelength of the laser light used during reproduction. A code bit and the like (all illustrations are omitted) are provided.

The recording section (5) includes a recording magnetic layer (8), a dielectric layer (9),
(10) and a reflective layer (11), with a first dielectric layer (9) on a substrate (4), a recording magnetic layer (
8), the second dielectric layer (10), and the reflective layer (11).

Among these, oxides, nitrides, etc. can be used as the first dielectric layer (9) and the second dielectric layer (lO), but in the dielectric layers (9) and (10), Nitride is more preferable because the oxygen in it may have an adverse effect on the recording magnetic layer (8), and silicon nitride, aluminum nitride, etc. are preferable as substances that do not allow oxygen and moisture to pass through and can sufficiently transmit the laser beam used. is suitable.

Further, the recording magnetic layer (8) is an amorphous magnetic thin film having an easy magnetization direction perpendicular to the film surface, and has not only excellent magneto-optical properties but also a large coercive force at room temperature. , and preferably have a Curie point near 200°C. Recording materials that meet these conditions include rare earth-transition metal alloy amorphous thin films, among which Tb
FeC.

Amorphous thin films are preferred. This recording magnetic layer (8) may contain an additive element such as Cr for the purpose of improving corrosion resistance.

The reflective layer (11) is preferably composed of a film with a high reflectance that reflects 70% or more of the laser beam at the boundary with the second dielectric layer (10), and is preferably a vapor-deposited film of a non-magnetic metal. be. Further, it is desirable that this reflective layer (11) is a good thermal conductor, and aluminum is suitable in consideration of ease of availability and ease of film formation.

Each of these layers is formed by a so-called vapor plating technique such as vapor deposition or sputtering. At this time, the thickness of each layer can be set arbitrarily, but it is usually set to about several hundred to several thousand. It is preferable that these film thicknesses be determined not only by the optical properties of each layer alone but also by taking into account the effects of the combination.

This is because, for example, when the thickness of the recording magnetic layer (8) is thinner than the wavelength of the laser beam, the laser beam transmits through the recording magnetic layer (8) and causes multiple interference with the light reflected at the boundaries of each layer. This is because the effective optical and magneto-optical properties of the recording magnetic layer (8) vary greatly depending on the combination of thicknesses.

The ultraviolet curing resin layer (6) is provided for the purpose of flattening and protecting the surface of the recording section (5), but may not be provided depending on the material, film thickness, etc. of the wear-resistant protective film (7), which will be described later. You can. The film thickness of this ultraviolet curable resin layer (6) is 3~
The thickness is approximately 5 μm, and acrylic ultraviolet curing resin or the like is usually used.

The above is the basic configuration of the magneto-optical disk (1),
In the present invention, since magnetic field modulation recording is performed while the magnetic head (3) is sliding on the disk surface, a wear-resistant protective film ( 7) is provided to suppress wear caused by sliding and ensure running performance of the magnetic head (3). This wear-resistant protective film (7) will be explained below.

The wear-resistant protective film (7) formed on the sliding surface of the magnetic head of the magneto-optical disk (1) is basically made of a cured film of thermosetting resin, electron beam curing resin, ultraviolet curing resin, etc. Or else, AI! , Nj, or the like by plating, vapor deposition, sputtering, or the like, or a film made of a lubricating polymer material such as polytetrafluoroethylene, or a nonwoven fiber.

Furthermore, lubricating powder, abrasive material, or the like may be added to the wear-resistant protective film (7) to further improve running performance and durability. In this case, examples of the lubricating powder used include carbon (carbon black, graphite powder, etc.), polytetrafluoroethylene powder (so-called Teflon powder), and the like. As the abrasive material, alumina, chromium oxide (so-called green), etc. are suitable. Other products include γ-Fetus acicular magnetic powder, CO impregnated (doped) γ-Fetus acicular magnetic powder, Co-coated γ-FetOz acicular magnetic powder, metal magnetic powder, Cr
It is also possible to use magnetic powders such as 0w magnetic powder and barium ferrite as the abrasive. Magnetic coatings containing these magnetic powders have been proven to have high durability when used with magnetic tapes, etc., and because of their high magnetic permeability, it is possible that even a small magnetic field can sufficiently apply a magnetic field to the recording section (5). There is.

Further, the wear-resistant protective film (7) may contain lubricants or extreme pressure agents that are widely used in the field of magnetic recording media.

A coupling agent or the like may be internally added or applied to prevent damage when the magnetic head comes into contact with the magnetic head.

As the lubricant, all kinds of lubricants such as higher fatty acids such as oleic acid and fatty acid esters can be used, and any conventionally known extreme pressure agents can be used. As the coupling agent, various coupling agents such as a silane coupling agent, a titanium coupling agent, a zircoaluminate coupling agent, etc. can be used. By using these coupling agents, the aforementioned resin and substrate.

Furthermore, it is possible to chemically bond powder components such as abrasives to improve film strength and adhesion to a substrate.

The above-mentioned wear-resistant protective film (7) does not necessarily have to be a single layer, but can also be multilayered.

In this case, by selecting the type of resin and the type of additives for each layer, it becomes possible to meet various demands. Alternatively, when the wear-resistant protective film (7) is made of a metal material, the lower layer is made of a hard metal film (or a non-metallic film such as ceramics may be used), and the upper layer is made of Au,
It is also possible to use a soft metal film such as Ag or Pb to reduce impact and friction.

In the wear-resistant protective film (7) having the above configuration,
In order to perform good magnetic field modulation recording, it is necessary to set the film thickness to an appropriate value.

That is, the thickness of the wear-resistant protection lli (7) determines the distance between the magnetic head (3) and the recording section (5),
At this time, it does not matter how far the magnetic head (3) is from the recording section (5), but it should be within the range where the minimum magnetic field necessary for recording can reach the recording magnetic layer (8) of the recording section (5). There must be. From the magnetic head (3) side,
The distance must be such that the recording current for applying the same magnetic field to the recording magnetic layer (8) can be made sufficiently small. For example, in order to generate a magnetic field of ±200 Oe in the recording magnetic layer (8), the distance between the magnetic head (3) and the recording magnetic layer (8) is 0.4 m (400 um).
While a recording current of approximately ±IA is required, if the distance is 0.04 mm (40 μm), approximately ±IA is required.
A recording current of 0.5 A is sufficient.

Regarding the lower limit, it is sufficient that the film thickness is sufficient to ensure durability, and the range is such that even if this wear-resistant protective film (7) is slightly scratched, it will not damage the recording section (5). do it.

In view of these points, the thickness of the wear-resistant protective film (7) is set here to 0.01 to 50 μm. This film thickness is 5
If it exceeds 0 μm, the strength of the magnetic field reaching the recording magnetic layer (8) will be small, and a large recording current will be required during recording. On the other hand, if the film thickness is less than 0.01, it will be difficult to ensure sufficient durability, and there is a risk that the recording section (5) will be damaged by scratches or the like.

On the other hand, the magnetic head (3) is designed to have a shape that does not damage the magnetic disk (1) as much as possible, but also prevents damage to the magnetic field generating means provided on the magnetic head (3) itself. It is necessary to create a shape that will not cause any damage. Therefore, in the present invention, the entrance end of the magneto-optical disk (1) is curved, and the magnetic field generating means such as a coil is arranged at a position retracted from the sliding surface of the magneto-optical disk.

3 and 4 show an example of a magnetic head used, and this magnetic head has a ferrite core (21)
A coil (22) serving as a magnetic field generating means is embedded inside.

The ferrite core (21) is made of polycrystal or single crystal of Mn-Zn ferrite or N1-Zn ferrite, and the magnetic head basically contacts it during rotation of the magneto-optical disk (1). Therefore, the circumference of the sliding surface is rounded to form a curved surface (21a), and the shape is such that, for example, the edge of the ferrite core (21) will not damage the magneto-optical disk (1). It is said that

A rectangular recess (21b) is provided approximately at the center of the sliding surface of the ferrite core (21).
A coil (22) is formed on the bottom surface of 21b).

Therefore, the coil (22) is connected to the magneto-optical disk (1).
It is formed at a position slightly set back from the sliding surface.

The coil (22) is formed by plating or vapor depositing a conductive metal such as copper and then etching it. It may be a so-called flat coil, or it may be a coiled coil made of copper wire, copper foil, or the like.

The terminal portion of this coil (22) is connected to the ferrite core (
It is pulled out to the back surface (the surface opposite to the sliding surface) through a through hole (23) provided in 21) and connected to the drive circuit.

Furthermore, if the coil (22) is directly exposed to the sliding surface of the magnetic head, there is a risk that the coil (22) will be damaged due to abrasion or peeling.
The recess (21b) of 1) is filled with a wear-resistant material (24) such as glass, plastic, silicone, etc., and the coil (22
) is not exposed on the sliding surface. In this way, the coil (22) is connected to the ferrite core (21).
), it is possible to not only prevent damage to the coil (22) but also to flatten the sliding surface of the magnetic head, thereby preventing damage to the magneto-optical disk (1). can also be made smaller. Additionally, by flattening the sliding surface of the magnetic head, fluctuations in the coefficient of friction can be suppressed, which not only keeps the load on the disk drive motor constant, but also eliminates increases in errors due to load fluctuations. becomes.

In the magnetic head configured as described above, a ferrite core (
21) may be changed to achieve a lower coefficient of friction, higher efficiency, etc.

The magnetic head shown in FIG. 5 has a convex part (21b) with curved corners around a concave part (21b) of a ferrite core (21).
21c), thereby making it possible to reduce the substantial contact area with the magneto-optical disk (1) and reduce the amount of wear. In this case, the recess (21b) of the ferrite core (21) may be filled with a filler (24) as in the previous example, but since flattening is not necessary, the filler may be used in some cases. (24) may not be filled.

The magnetic head shown in FIG. 6 also has a ferrite core (2
A center core (21d) that fits into the center hole of the coil (22) is integrally provided in the center of the recess (21b) of 1), and is suitable for a magnetic head for low frequency signals.

The above-mentioned magnetic heads all have a ferrite core (21)
The coil (22) is embedded in the recess (21b) of the magnetic head, but as shown in FIGS. Available for use.

This magnetic head has a single magnetic pole head (3) in which a coil bobbin (34) is fitted into a rod-shaped center core (33).
1) is placed in the center of the guard material (32).

The guard material (32) is made of ceramics such as potassium titanate, and includes a pair of side guard materials (32a) and (32b) that sandwich the center core (33) from both sides; (32b) A pair of center guard members (32C) that determine the position of the center core (33).

(32d).

Therefore, the center core (3) of the single magnetic pole head (31)
3) These center guard materials (32c), (32
d) and side guard materials (32a) and (32b), and a tip end surface (3
It is shaped to expose 3a).

Furthermore, in the magnetic head having the above structure, the guard material (3
The peripheral edge on the sliding surface side of 2) is curved to prevent scratches on the magneto-optical disk (1). Further, in the single magnetic pole head (31), the coil bobbin (34), which is a magnetic field generating means, is connected to the magneto-optical disk (1).
) is not exposed to the sliding surface and is placed at a position retreated from the sliding surface.

In a magnetic head configured in this way, it is possible to generate a strong magnetic field, so the track radius can be expanded, and alignment with the beam spot of the laser beam irradiated from the optical pickup (2) is also possible. It's easy. Furthermore, the basic configuration of this magnetic head is the same as that of a so-called floppy disk magnetic head, and since it is simpler than a floppy disk magnetic head by omitting an erasing head and the like, it is easier to manufacture.

By the way, in the magnetic head having the above configuration,
In either case, the higher the frequency, the greater the heat generation.
Furthermore, frictional heat is also generated due to sliding with the magneto-optical disk (1). This heat generation causes adverse effects such as causing thermal destruction of the magnetic head and increasing resistance within the coil to reduce the generated magnetic field.

Therefore, a cooling mechanism is provided for the magnetic head (3) used.
It is preferable to perform recording while suppressing the heat generation. In this case, examples of the cooling mechanism include one using a Vertier element and one with fins for air cooling.

In the magneto-optical recording system of the present invention, recording is performed with the above-mentioned magnetic head (3) sliding against the magneto-optical disk (1). At this time, the contact state of the magnetic head (3) with the magneto-optical disk (1) is (a) contact when the disk is stationary, floating when the disk is rotating (so-called C8S method), and (b) disk rotation even when the disk is stationary. Although two forms of contact are sometimes considered, the latter is advantageous in terms of lower magnetic fields, etc. Further, in a magneto-optical disk system with a low linear velocity (1.2 to 1.4 m/sec), the former cannot be adopted, but the latter makes it possible to construct a good sliding type magneto-optical recording system.

During sliding, since the magneto-optical disk (1) is provided with a wear-resistant protective film (7), the magneto-optical disk (1)
The distance between the magnetic head and the magnetic head (3) is small, making low magnetic field recording possible and ensuring sufficient durability.

In addition, when the magnetic head (3) is slid, it is preferable to use it by attaching it to a gimbal spring or the like to avoid so-called uneven contact.

Next, a magneto-optical disk having the configuration shown in FIG. 2 was actually prepared, the magnetic head was moved to perform recording, and its characteristics were evaluated.

Example 1 The recording portion of the produced magneto-optical disk had a four-layer structure, and the film thickness was as follows.

First dielectric layer: SI3N4 1000 people Recording magnetic layer: Tb-FeCo-Cr 230 people Second dielectric layer: 5isN, 500 people Reflective layer: l 700 people Ultraviolet curing resin layer = 3 μm And the above ultraviolet curing resin layer A wear-resistant protective film was formed thereon by the method described below.

Composition of paint Carbon (average particle size 200μ)...100 parts by weight Vinyl chloride-vinyl acetate copolymer...100 parts by weight Vinyl chloride-vinyl acetate-vinyl alcohol copolymer
...100 parts by weight of the above composition was kneaded with a mixed solvent of methyl ethyl ketone, toluene and cyclohexanone (1:1) in a ball mill for 40 hours.

Next, 20 parts by weight of a thermosetting agent (trade name: Coronet L) and 1.5 parts by weight of an aliphatic hydrocarbon lubricant (olive oil) were added, and the mixture was stirred for 20 minutes.

This was applied onto the ultraviolet curable resin layer using a doctor blade with a gap of 25.4 μm and dried.

The thickness of the coating film after drying was 20 μm.

On the other hand, a magnetic head having the structure shown in FIGS. 3 and 4 was used. The coil, which is the magnetic field generating means of this magnetic head, was made by bundling 24 copper wires with a diameter of 30 μm and winding them 27 times (5 times×5 stages).

The above-mentioned magnetic head was slid onto the magneto-optical disk through the above-mentioned wear-resistant protective film, and the linear velocity was 1.2 to t, +m/sec, the recording power of the optical pickup was 4.5 mW, and the reproducing power was 0.5.
Recording and reproduction were repeated at mW.

As a result, it became possible to record in a low magnetic field, and it was also excellent in terms of durability.

Example 2 After applying a wear-resistant protective film using the same method as in Example 1, a mixed solution of 2 parts by weight of stearic acid and 100 parts by weight of ethanol was added so that the thickness of the stearic acid layer was 2 g/rrI. It was applied to.

When this magneto-optical disk was repeatedly recorded and reproduced by sliding the magnetic head in the same manner as in Example I, it was again possible to record in a low magnetic field, and the durability was further improved.

〔Effect of the invention〕

As is clear from the above description, in the present invention,
Since the magnetic head slides against the magneto-optical recording medium through a wear-resistant protective film with a thickness of 0.01 to 50 μm,
The distance between the magnetic head and the recording magnetic layer can be stably maintained at a small value without requiring complicated servo or the like. Therefore, a magnetic field modulation magnetic head can be used even if the generated magnetic field is small, and if it has the ability to generate a large magnetic field, it is possible to reduce the applied current and save power. . Furthermore, it becomes possible to ensure the frequency characteristics of the magnetic head up to a high frequency range, and it becomes possible to achieve a high transfer rate and high density. On the other hand, when viewed from the magneto-optical recording medium side, it is no longer necessary to have a recording magnetic layer with high magnetic field sensitivity, and if the recording magnetic layer is a film that can record in a low magnetic field, a wide margin against the magnetic field can be provided. becomes possible.

Furthermore, in the magneto-optical recording method of the present invention, since the magnetic head is slid through the wear-resistant protective film, it is possible to significantly suppress wear of the magneto-optical recording medium due to sliding. It is possible to ensure durability.

On the other hand, since the magnetic head used in the present invention has a curved end at the entrance side of the magneto-optical recording medium,
Smooth running is possible, and the magneto-optical recording medium is not inadvertently damaged. Furthermore, since the magnetic field generating means is arranged at a position recessed from the largest convex portion on the magneto-optical recording medium side, there is no risk of damaging the magnetic field generating means itself.
The sliding condition against the magneto-optical recording medium can also be made good.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram for explaining a magneto-optical recording system to which the present invention is applied. FIG. 2 is an enlarged sectional view of a main part showing an example of the configuration of a magneto-optical recording medium used in the magneto-optical recording method of the present invention. FIG. 3 is a schematic perspective view showing an example of a magnetic head used in the magneto-optical recording system of the present invention, and FIG. 4 is a sectional view thereof. FIG. 5 is a sectional view showing another example of the magnetic head, and FIG.
The figure is a sectional view showing still another example of the magnetic head. FIG. 7 is a schematic perspective view showing an example of a floppy disk head type magnetic head, and FIG. 8 is a sectional view thereof. 1... Magneto-optical disk 2... Optical pickup 3... Magnetic head 7... Wear-resistant protective film

Claims (2)

[Claims] (1) A magneto-optical recording method characterized in that a magnetic head is slid on a magneto-optical recording medium having a wear-resistant protective film with a thickness of 0.01 to 50 μm through the wear-resistant protective film. (2) At least the end on the entrance side to the magneto-optical recording medium has a curved shape, and the magnetic field generating means is provided at a position recessed from the largest protrusion on the magneto-optical recording medium side (
1) A magnetic head for the magneto-optical recording method described above.