JPH04181533A - Magnetooptical recording medium - Google Patents

Abstract

PURPOSE:To achieve higher endurance by forming a wear resisting protective film on the surface. CONSTITUTION:A magnetooptical disc 1 is laminated with a recording part 5 on one main surface of a substrate 4 and moreover, the surface of the recording part 5 is covered with an ultraviolet hardening resin layer 6 and a wear resisting protective film 7. With this magnetooptical modulation recording medium, a magnetic field modulation recording is performed making a magnetic head 3 slide over a disc surface. At this point, the wear resisting protective film 7 serves to ensure the inhibition of wearing as caused by sliding and a running property of the magnetic head 3. The protective film 7 comprises a resin hardening film made of a thermosetting resin, electron beam hardening resin, ultraviolet hardening resin or the like or that blended partially with the electron beam hardening resin film, the ultraviolet hardening resin or the like.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magneto-optical recording medium used in a magneto-optical recording method in which recording is performed by sliding a magnetic head on the magneto-optical recording medium. A [Summary of the Invention] The present invention provides a magneto-optical recording medium in which a recording magnetic layer is formed on a transparent substrate, by forming a wear-resistant protective film on the surface opposite to the transparent substrate. This is intended to ensure sufficient durability even when the head is slid.

[Conventional technology]

The magneto-optical recording method heats a part of the magnetic thin film above the Curie point or temperature compensation point, eliminates the coercive force in this part, and reverses 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 with an axis of easy magnetization perpendicular to the film surface and a large magneto-optic effect on the whole 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 film), a reflective layer, and a dielectric layer, and the signal is read by irradiating laser light from the transparent substrate side. It is being

[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 must be 0.1 m or less.

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 magneto-optical disks whose substrates are made of polycarbonate or the like, there is a limit to the suppression of surface runout, and servos that maintain a constant distance between the magnetic head and the surface of the magneto-optical disk, such as a force servo in an optical pickup, are required. Or, like hard disks, you have no choice but to use a so-called flying head.

However, especially in low-speed rotation systems of about 300 to 600 rpm, flying heads cannot be used, and complex servos are 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 that floats via a magnetic head or 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, a magneto-optical recording method may be considered in which recording is performed while the magnetic head is slid against the magneto-optical recording medium, but in this case, problems such as scratches and wear caused by the sliding of the magnetic head arise.

The present invention has been proposed to solve this problem, and an object of the present invention is to provide a magneto-optical recording medium that can ensure sufficient durability even when a magnetic head is slid.

[Means to solve the problem]

In order to achieve the above object, the magneto-optical recording medium of the present invention includes a recording magnetic layer formed on a transparent substrate, and a wear-resistant protective film formed on the surface opposite to the transparent substrate. Further, the wear-resistant protective film contains a solid filler, a lubricant, or a coupling agent.

[Effect]

If recording is performed without the magnetic head sliding against the magneto-optical recording medium, the distance to the recording magnetic layer will be sufficiently small, and the magnetic field generated by the magnetic head will be small. Furthermore, no special servo mechanism is required for the magnetic head, and problems such as crashes are eliminated.

However, in this case, an increase in error rate due to wear and damage to the magneto-optical recording medium becomes a problem, but in the magneto-optical recording medium of the present invention, a wear-resistant protective film is formed on the sliding surface of the magnetic head. This ensures sufficient durability against wear and damage.

[Example] Hereinafter, an example to which the present invention is applied will be described in detail 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 arranged facing each other with a magneto-optical disk (+) sandwiched between them. 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 disk-shaped transparent substrate with a thickness of about a few inches (for example, 1.2 mm), and its material is a plastic material such as acrylic resin, polycarbonate resin, polyolefin resin, or epoxy resin. In addition, 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. Code pits and the like (all illustrations are omitted) are provided.

The recording section (5) includes a recording magnetic layer (8 mm), a dielectric layer (9),
It has a four-layer structure consisting of a substrate (4), a first dielectric layer (9), a recording magnetic layer (
8), the second dielectric INF (10), and the reflective layer (11).

Among these, can oxides, nitrides, etc. be used for the first dielectric layer (9) and the second dielectric layer (10)? Nitride is more preferable since oxygen may have an adverse effect on the recording magnetic layer (8), and silicon nitride or aluminum nitride is a material that does 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 it is desirable to have a Curie point near 200°C. Recording materials that meet these conditions include rare earth-transition metal alloy amorphous thin films, among which T
bFeC.

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 view of ease of availability and ease of film formation.

Each of these layers is formed by a so-called vapor phase 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 curable resin layer (6) may be provided for the purpose of flattening or protecting the surface of the recording section (5), or may not be provided depending on the material and 2M thickness of the wear-resistant protection M (a) described later. Good too. The film thickness of this ultraviolet curable resin layer (6) is 3~
The thickness is about 5 μm, and acrylic ultraviolet curing resin or the like is usually used.

Is the above the basic configuration of the magneto-optical disk (1)?
In the magneto-optical recording medium of the present invention, since magnetic field modulation recording is performed without the magnetic head (3) sliding against the disk surface, the magnetic head (3) is placed on the ultraviolet curing resin layer (6).

Alternatively, a wear-resistant protective film (7) is provided directly on the recording section (5) 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 CI) is basically made of a cured resin film of thermosetting resin, electron beam curing resin, ultraviolet curing resin, etc. Alternatively, it is made of a resin cured film partially blended with an electron beam curing resin or an ultraviolet curing resin.

For example, by irradiating an electron beam-curable oligomer with an electron beam and curing it to form a wear-resistant protective film (7), a magneto-optical disk that is less likely to be damaged when a magnetic head comes into contact with it can be obtained. In this case, the molecular weight of the oligomer used is 2
000 or less is preferable.

Similarly, a strong film can be formed by blending an ultraviolet curable resin into the wear-resistant protective film (7) and curing it by irradiating it with ultraviolet rays immediately after forming the protective film (7).

Alternatively, when forming the wear-resistant protective film (7), a curing agent may be added internally to improve the film strength and increase durability. In this case, the molecular structure and type of the curing agent used are arbitrary, and it is also possible to use multiple types of curing agents. The amount of curing agent added depends on the type of curing agent used, but is usually 0.00 parts by weight per 100 parts by weight of the resin.
The amount is preferably 1 to 50 parts by weight. In addition, the curing temperature is arbitrary, and curing at room temperature is possible, or the curing speed is slow, so create a predetermined temperature environment (e.g. above the glass transition point) in a thermostatic oven and harden by placing it in that temperature for a certain period of time. It is preferable to increase the speed.

The heat curing treatment is advantageous not only in shortening the reaction time but also in terms of removing residual solvent and moisture and improving film hardness. As the curing progresses and the curing agent becomes glassy, it is possible to harden the film quality and improve durability.

When the cured resin film is used as the abrasion-resistant protective film (7) as described above, suitable methods for forming it include a method using a doctor blade, a method using a spin cord, and the like.

For example, by placing paint uniformly on a flat adapter between the doctor blade and the magneto-optical disk (1) and moving the doctor blade toward you, a coating film with a uniform thickness is formed. Alternatively, by attaching the magneto-optical disk (1) to the motor rotation shaft and supplying paint onto the magneto-optical disk (1) while rotating, a coating film with even thickness can be formed. . These methods are not only easy to form a film, but also allow for uniform film thickness.
Furthermore, it is possible to control surface roughness and film thickness by manipulating the solid content and viscosity of the paint.

In addition, when mass production is considered, a gravure method, a sandblast transfer method, an offset method, etc. are also suitable.

In the gravure method, for example, a magneto-optical disk (1) is mounted on the outer peripheral surface of a disk holder with the magnetic head side surface facing outward, paint is supplied from a paint nozzle between an inkneri roll and a gravure roll, and the disc holder is By running the gravure roll while pressing it with a back roll, the paint on the surface of the gravure roll is transferred to the magnetic head side surface of the magneto-optical disk (1). When transferring paint, the thickness can be controlled by the position of the back roll and the pattern depth of the gravure roll. After the paint is transferred, it is flattened and dried with a dryer to form a paint film. Note that the back roll does not necessarily have to be cylindrical, and it is also possible to configure it so that the conveyor belt of the disc holder plays this role. Further, the position and rotation of the ink roll and the paint nozzle for supplying the paint are arbitrary.

The sandblast transfer method transfers paint using a sandblast roll whose surface has been roughened by sandblasting, and the basic device configuration is the same as the gravure method described above. However, inkneri roll is not necessary,
Film thickness is controlled by the position of the back roll, peripheral speed of the sandblasting roll, and surface roughness.

The offset method has the same equipment configuration as the gravure method except that it uses an offset roll with a flat surface, and the film thickness is controlled by the position of the back roll, the circumferential speed of the offset roll, and the distance between the offset roll and the ink screw roll.

These methods are excellent in terms of uniformity of film thickness, ease of thickness control, reproducibility, and surface roughness, and the coating speed can be set to over 100 m per minute, making it easy to mass-produce. It is very advantageous in this respect.

Of course, the wear-resistant protective film (7) is not limited to the above-mentioned cured film, for example, AI! , those made of wear-resistant materials such as Ni by plating, vapor deposition, sputtering, etc.
It may also be a coating of a lubricating polymeric material such as polytetrafluoroethylene or a non-woven fiber such as silk. Polytetrafluoroethylene is widely used as a solid lubricant, and methods for forming a film include directly rubbing it on the disk surface, vapor deposition, and spin-coding after dissolving it in a solvent. The non-woven fiber has a fiber diameter of 500
It is preferable to use fibers with a diameter of .mu.m or less, and the type of fibers may be natural or synthetic. Furthermore, it is also possible to use an abrasive-based nonmagnetic film or a lubricant film, and it is also possible to form the film by depositing lubricant powder. In this case, any known lubricants such as fatty acids and fatty acid esters can be used, and the type and composition do not matter. As the lubricating powder, powder of a substance with a small coefficient of friction such as carbon or polytetrafluoroethylene may be used, or it is preferable that the hardness of the powder is lower than that of the substrate (4). The particle size of the lubricating powder used is approximately #8 to #200,000.

Moreover, 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 also be used), and the upper layer is made of Au, Ag, etc.
It is also possible to use a soft metal film such as Pb or the like to reduce impact and friction.

On the other hand, a solid filler such as a lubricating powder or an abrasive material may be added to the above-mentioned wear-resistant protective film (7) to further improve running performance and durability.

The type of lubricating powder and abrasive material does not matter, or the lubricating powder is carbon (carbon black, graphite powder, etc.)
or polytetrafluoroethylene powder (so-called Teflon powder), and as the abrasive material, alumina, chromium oxide (so-called green), etc. are suitable. It is also possible to add multiple types at the same time.

The above-mentioned solid filler is generally added internally to the wear-resistant protective film (7), and in this case, the particle size is preferably within twice the film thickness at most. It is also possible to mix the solid filler with a small amount of binder or apply the solid filler alone to the surface of the wear-resistant protective film (7), in which case the maximum particle size is Protective film (7)
The film thickness shall be equal to or less than that of

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 a lubricant, all kinds of lubricants can be used, such as higher fatty acids such as oleic acid and fatty acid esters, and extreme pressure agents include phosphorus-based extreme pressure agents, inert-based extreme pressure agents, and halogen-based extreme pressure agents. Any conventionally known agent can be used, such as an agent, an organometallic extreme pressure agent, or a composite extreme pressure agent. 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 resin constituting the wear-resistant protective film (7) and the substrate, as well as the powder components such as abrasives, are chemically bonded, increasing the strength of the film and its adhesion to the substrate. Is possible.

In addition, γ-Fe2Oz acicular magnetic powder, Co-impregnated (doped) γ-FetOx acicular magnetic powder, Co-coated γ-FetOx acicular magnetic powder, metal magnetic powder, C
It is also possible to use magnetic powders such as r0t magnetic powder and barium ferrite as the abrasive material. 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.

When these magnetic powders are dispersed in the wear-resistant protective film (7), the orientation direction of the magnetic powders is non-oriented, circumferential direction (including cases where the magnetic powder is oriented obliquely to the film surface), and radial direction. (one direction within the plane), vertical direction, etc., or
Various advantages can be obtained by selecting the orientation direction.

For example, in the case of non-oriented magnetic powder, the magnetic powder is oriented in random directions even at the same position within the plane of the magneto-optical disk (1).
The magnetic influence exerted on the recording magnetic layer (8) is considered to be the same regardless of the part, and the influence of pit length, noise, etc. is eliminated. Even when oriented in the circumferential direction, magneto-optical disks (
The same orientation occurs in the portion of 1), and the recording magnetic layer (8
), there are few factors that give local magnetic anisotropy (,
There is no change in pit length, noise, etc. depending on the location.

On the other hand, in the case of perpendicular orientation, the magnetization direction of the recording magnetic layer (8) and the easy magnetization axis direction of the magnetic powder coincide, and since the magnetic permeability in this direction is high, a larger magnetic field is applied to the recording magnetic layer (8).
8), making it possible to record with a small magnetic field.

Any method used for magnetic recording media can be used as the orientation method. For example, to achieve non-orientation, a pair of orientation magnets is arranged so that the opposing directions of the magnetic poles are perpendicular to each other within the film surface of the coating film. However, an alternating current voltage may be applied to each of these orientation magnets before the coating film dries.

To orient in the circumferential direction, either the widthwise edges or N
Using a long magnet with poles and south poles, one longitudinal end of this magnet is placed at the center of the magneto-optical disk (1), and the magnet is rotated in the circumferential direction of the disk around this one end. It's good to let it happen. When oriented in the lateral direction, both edges in the width direction are the N pole and S pole, respectively.
It is sufficient to use a long magnet with poles and to move it in parallel in the width direction of the magnet on the magneto-optical disk (1).

In the case of vertical alignment, a DC magnet may be arranged so that the magnetic flux passes perpendicularly to the disk surface of the magneto-optical disk (1), and the magneto-optical disk (1) may be rotated.

In addition, by adding color to the above-mentioned wear-resistant protective film (7) by selecting a pigment or the like, it is possible to ensure durability and at the same time give designability and increase the commercial value.

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 protective film (7) determines the distance between the magnetic head (3) and the recording section (5), or the thickness of the wear-resistant protective film (7) determines the distance between the magnetic head (3) and the recording section (5). It does not necessarily have to be far away, but it must be within a range where the minimum magnetic field necessary for recording can reach the recording magnetic layer (8) of the recording section (5). From the side of the magnetic head (3), the distance must be such that the recording current can be made sufficiently small to apply the same magnetic field to the recording magnetic layer (8). For example, in order to generate a magnetic field of ±200 oersted in the recording magnetic layer (8), the magnetic head (3) and the recording magnetic layer (8) are required to generate a magnetic field of ±200 Oe.
) when the distance is 0.4 m (400 μm), a recording current of approximately ±IA is required, whereas when the distance is 0.04 mm (40 μm), a recording current of approximately ±0.5 is required.
A recording current of 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 there is a slight scratch on this wear-resistant protective film (7), 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 preferably 0.01 to 50 μm. If the film thickness exceeds 50 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 μm, 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) that slides on the above-mentioned magneto-optical disk (1) needs to have a shape that does not cause damage to the magneto-optical disk (1) as much as possible. ) It is necessary that the shape is such that it will not damage the magnetic field generating means provided on itself. Therefore, it is preferable that the end on the entrance side of the magneto-optical disk (1) be curved and that the magnetic field generating means such as a coil be arranged at a position retracted from the sliding surface of the magneto-optical disk.

Figures 3 and 4 show examples of magnetic heads 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 Ni-Zn ferrite, and the magnetic head basically contacts it during rotation of the magneto-optical disk (1). Since it is assumed that
The circumference of the sliding surface is rounded to form a curved surface (21a),
For example, the shape is such that the edge portion of the ferrite core (21) will not damage the magneto-optical disk (1).

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, turn the coil (22).

By embedding it in the recess (21b) of the light core (21), it is not only possible to prevent damage to the coil (22), but also to flatten the sliding surface of the magnetic head. ) can also be made to have less damage. 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, or may be filled with a filler (24) as the case may be since flattening is not necessary. (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).

Note that 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 width can be widened, 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 that develops 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 device shown in FIG. 1, 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 as follows: contact when the fal disk is stationary, floating when the disk is rotating (so-called C8
S method) (b) Two forms of contact can be considered, both when the disk is stationary and when the disk is rotating, but 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: 5isN = 1000 people Recording magnetic layer: Tb-Fe-Co-Cr 230 people Second dielectric layer: 5IzNs 500 people Reflective layer, A77 700 people Ultraviolet curing resin layer: 3 μm and
A wear-resistant protective film was formed on the ultraviolet curable resin layer by the following method.

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/cyclohexanone (1:1:1.) in a ball mill for 40 hours.

Next, 20 parts by weight of a thermosetting agent (trade name Coronate L) and 1.5 parts by weight of an aliphatic hydrocarbon lubricant (olive oil) were added and 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 magnetic head was slid onto the magneto-optical disk through the wear-resistant protective film at a linear velocity of 1.2 to 4 m/sec, a recording power of 4.5 mW, and a reproducing power of the optical pickup of 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, 1112 parts by weight of stearin and 10 parts by weight of ethanol were added.
0 parts by weight of the mixed solution was applied so that the coating thickness of stearic acid was 2 g/d.

When this magneto-optical disk was repeatedly recorded and reproduced by sliding the magnetic head in the same manner as in Example 1, recording was still possible in a low magnetic field, and the durability was further improved.

Example 3 When 1 part by weight of alumina with an average particle size of 2μ was added as an abrasive to the paint for forming the wear-resistant protective film in Example 1, the amount of wear after the 10' bath was reduced by 20%. did.

Example 4 When 2 parts by weight of a silane coupling agent (trade name Al100) was added to the paint for forming the wear-resistant protective film in Example 1, the amount of wear after a 10-s pass was still 20%.
%Diminished.

Example 5 Polytetrafluoroethylene powder with an average particle size of 5 μm was added to the paint for forming the wear-resistant protective film in Example 1 above.
When added in parts by weight, the wear amount after 10" pass was 7% per month.
Diminished.

〔Effect of the invention〕

As is clear from the above explanation, in the magneto-optical recording medium of the present invention, since a wear-resistant protective film is formed on the surface, it is possible to significantly suppress wear caused by sliding of the magnetic head. Therefore, it is possible to ensure durability.

Furthermore, if the magneto-optical recording medium of the present invention is used, the distance between the magnetic head and the recording magnetic layer can be stably maintained at a small value without the need for complicated servos, etc. by sliding the magnetic head against the magneto-optical recording medium. I can do something. 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, it is necessary to have a wide margin against the magnetic field. It becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram for explaining a sliding type magneto-optical recording system to which the magneto-optical recording medium of 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 to which the present invention is applied. FIG. 3 is a schematic perspective view showing an example of a magnetic head used in the sliding type magneto-optical recording system, 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. l...Magneto-optical disk 2...Optical pickup 3...Magnetic head 7...Wear-resistant protective film

Claims (4)

[Claims] (1) A recording magnetic layer is formed on a transparent substrate, and
A magneto-optical recording medium comprising a wear-resistant protective film formed on a surface opposite to the transparent substrate. (2) The magneto-optical recording medium according to claim (1), wherein the wear-resistant protective film contains a solid filler. (3) The magneto-optical recording medium according to claim (1), wherein the wear-resistant protective film contains a lubricant. (4) The magneto-optical recording medium according to claim (1), wherein the wear-resistant protective film contains a coupling agent.