JP2955959B2 - Magneto-optical disk and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical disk of a magnetic field modulation type capable of overwriting and a method of manufacturing the same.
The present invention relates to an overcoat layer necessary for improving the sliding resistance and crack resistance of a magneto-optical disk.

[0002]

2. Description of the Related Art In recent years, a magneto-optical disk has attracted attention as a high-density recording medium and has been partially commercialized, but is a recording mode requiring an erasing mode and a writing mode. Therefore, there is a problem that the information transfer speed is low.

In order to solve this problem, a magnetic field modulation overwrite method (for example, JP-A-63-229643) and a light modulation overwrite method using magnetic exchange coupling (for example,
JP-A-62-175948) has been proposed.

The magnetic field modulation system is a system in which the intensity of a laser beam is fixed and the direction of an externally applied magnetic field is modulated. As means for generating the modulated externally applied magnetic field, there is a floating type magnetic head which is used for example in a magnetic disk device (e.g., JP 63- 2 29643 JP). This modulates the current flowing through the coil of the magnetic head to modulate the externally applied magnetic field.

Hereinafter, an example of the above-described conventional art will be described with reference to the drawings.

FIG. 7 is a sectional view showing a schematic configuration of a conventional magneto-optical disk. In FIG. 7, 11 is a transparent glass substrate, 12 is an ultraviolet curable resin film having a pre-group pattern (normal thickness 10 to 100 μm), and 13 is a first protective film made of ZnS or SiN (normal thickness 60 nm). ~ 150nm), 14 is TbFeCo
Magneto-optical recording film (normal thickness 20 to 150 nm), 15 is ZnS or S
A second protective film made of iN (normally 60 to 150 nm in thickness), and 16 is a crash prevention film (thickness) coated with a mixed resin composition composed of alumina powder, polyvinyl methyl ether resin and thermosetting epoxy resin. 17 is a carbon fluoride oil, 18 is a slider, 19 is a magnetic head installed at one end of the slider 18, 20 is an objective lens, 21 is a laser beam, 22
Is a disk rotation drive. The slider 18 and the objective lens 20 are movable in a state where they are arranged at positions facing each other across the magneto-optical disk.

The operation of the conventional magneto-optical disk configured as described above will be described below with reference to FIG.

When the disk rotation drive 22 is stationary, the slider 18 is in contact with the crash prevention film 16 of the magneto-optical disk via the carbon fluoride oil 17.

When the disk rotation driving device 22 is driven, the slider 18 slides on the surface of the carbon fluoride oil 17. The rotation speed of the disk rotation drive device 22 increases,
When the relative speed of the slider 18 and the class Tsu Shiyu preventing film 16 reaches the above schematic 1 m / s, the magnetic head 19 that is secured to the sliders 18 and the slider 18 floats from 17 surface carbon fluoride-based oil.

After the slider 18 and the magnetic head 19 levitate,
The objective lens 20 and the laser beam 21 arranged at a position facing the magnetic head 19 simultaneously access the drive system (not shown)
Moves to an arbitrary position on the magneto-optical disk, and locally heats the magneto-optical recording film 14 with the laser light 21 so that the magnetic head
By passing the modulated current to 19 of the coil (not shown), intends row write recording information on the magneto-optical recording film 14.

When recording and reproduction of information on and from the magneto-optical disk are completed and the disk rotation drive 22 is stopped, the slider 18 and the magnetic head 19 shift from floating to sliding, and the carbon fluoride oil 17 is lubricated. As a result, the vehicle travels in contact and stops on the crash prevention film 16.

However, the externally applied magnetic field necessary for reversing the magnetic field of the magneto-optical recording layer 14 locally heated by the laser light is generated only in the vicinity of the magnetic head 19. The distance between the magneto-optical recording films 14 must be as short as possible. In addition, the floating magnetic head 19 has a low flying height on the crash prevention film 16 by utilizing gas lubrication.
(E.g., several μm or less), and a contact start / stop (hereinafter, CS
S is abbreviated).

In order to perform the CSS method on a magneto-optical disk, (1) that the surface of the disk crash prevention film 16 and the surface of the magnetic head slider 18 do not stick when the magneto-optical disk is stationary, and (2) rotation start of the magneto-optical disk and when the magnetic head contacts run line at stop, the magnetic head 19 does not destroy the magneto-optical recording film 14 of the magneto-optical disk,
(3) It is necessary that dust that hinders the floating of the magnetic head 19 does not adhere to the slider surface of the magnetic head.

In order to satisfy the above-described conditions, a magneto-optical disk in which the crash prevention film 16 is made of a thermosetting resin mixed with alumina fine particles and a thermoplastic resin and provided with a mixed resin composition in which a resin is impregnated with a lubricant. Has been proposed (for example, JP-A-63-229643).

[0015]

However, in the above configuration, since a glass substrate is used and an ultraviolet curable resin film having a groove formed thereon is formed, the material cost and the manufacturing cost increase, and the optical cost increases. There is a problem that the magnetic disk becomes expensive.

When a transparent polycarbonate substrate is used to solve this problem, the polycarbonate resin has a lower mechanical strength than glass, and the crash prevention film 16 made of epoxy resin has a low crash prevention effect. Had.

Further, in the above configuration, when dust having a size on the order of submicrons enters between the magnetic head slider and the crash prevention film during CSS, the dust rolls along the traveling direction of the magnetic head slider, and There is a high possibility that a long scratch is generated in the track direction of the magnetic disk, and there is also a problem that an error may occur and error correction may not be possible.

In view of the above problems, the present invention has a high crash prevention effect even when a resin substrate such as polycarbonate is used, and can prevent the occurrence of a fatal scratch defect on a magneto-optical disk even when dust enters. An object of the present invention is to provide a magneto-optical disk having an overcoat layer for preventing crash and a method for manufacturing the same.

[0019]

The magneto-optical disk of the present invention has an overcoat layer mainly composed of a phosphazene-based photocurable resin, an inorganic compound powder, and a fatty acid ester-based lubricant.

Further, a magneto-optical recording medium formed on a polycarbonate substrate, a photo-curable resin, and a liquid lubricant which is hardly soluble in the photo-curable resin, has a small specific gravity and does not have photo-curability. A means for forming a coating film by applying a suspension of the mixed solution to the surface of the magneto-optical recording medium to a predetermined thickness, and a means for curing the photocurable resin by irradiating the coating film with ultraviolet light, the Jun of the overcoat layer was cured
It is produced by the means for removing the slip agent.

[0021]

According to the present invention, even when a resin substrate such as polycarbonate is used, a crash prevention effect can be obtained by the combination effect of a phosphazene-based photocurable resin having high hardness, an inorganic compound powder and a fatty acid ester-based lubricant. A high magneto-optical disk can be provided. Further, it is possible to form a retracting space of dust that penetrated by the means described above to the surface of the overcoat layer, Ru can be prevented occurrence of a fatal flaw defect for the disk in accordance with the movement of dust.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magneto-optical disk according to one embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic view of an overcoat layer of a magneto-optical disk according to one embodiment of the present invention. In FIG. 1, 1 is a phosphazene-based photocurable resin.
(Manufactured by Idemitsu Chemical Industry Co., Ltd., trade name: PPZ), 2 has a center particle size of about 0.
6μm alumina fine particles (AKP, trade name, manufactured by Sumitomo Chemical Co., Ltd.)
-20), 3 is a lubricant composed of n-butyl stearate and oleyl oleate, 4 is an overcoat layer mainly composed of the phosphazene-based photocurable resin 1, alumina fine particles 2, and lubricant 3, and 5 is TbFeCo. A magneto-optical recording medium in which a magneto-optical recording film is covered with a dielectric film such as ZnS or SiN or ZnSe / SiO ₂ , 6 is a polycarbonate substrate, 18 is a slider, 19 is a magnetic head, 20 is an objective lens, 21 is a laser beam, 22 is a disk rotation drive.

The operation of the magneto-optical disk configured as described above will be described below with reference to FIG.

When the disk drive 22 is stationary, the slider 18 is in contact with the overcoat layer 4. Since a part of the lubricant 3 oozes out on the surface of the overcoat layer 4, the dynamic friction coefficient between the overcoat layer 4 and the slider 18 is
0.3 to 0.5. When the disk rotation driving device 22 is driven, the slider 18 slides smoothly on the overcoat layer 4. The rotation speed of the disk rotation driving device 22 increases, and the relative speed between the slider 18 and the overcoat layer 4 becomes approximately 1 m /
When the distance reaches s or more, the slider 18 and the magnetic head 19 float from the overcoat layer 4.

After the slider 18 and the magnetic head 19 levitate, the objective lens 20 and the laser beam 21 provided at a position facing the magnetic head 19 move to an arbitrary position on the disk by an access drive system (not shown). , Laser light 21
To locally heat the magneto-optical recording film of the magneto-optical recording medium 5,
Information is written on the magneto-optical recording film by passing a modulation current through a coil (not shown) of the magnetic head 19.

When the recording / reproduction of information on the magneto-optical disk is completed and the disk rotation driving device 22 is stopped, the slider 18 and the magnetic head 19 shift from the floating traveling to the sliding traveling, and stop on the overcoat layer 4. This series of operations is called CSS.

FIG. 2 shows how errors occur when the above-mentioned CSS is applied to the magneto-optical disk of FIG. 1 with the overcoat layer 4 and then left in an environment of 80 ° C. and 80% RH for 2000 hours. In FIG. 2, a characteristic A represents a change in occurrence of an error in the magneto-optical disk according to the embodiment of the present invention shown in FIG.
Is a change in occurrence of an error in the magneto-optical disk in which the substrate material of the magneto-optical disk in the conventional configuration is changed from glass to polycarbonate.

The CSS the characteristic A as apparent from FIG. 2
Although the error occurrence rate does not change even if the number of tests increases, in the characteristic B, the error occurrence rate increases from 5 × 10 ⁻⁶ to 7 × 10 ⁻⁵ after 100,000 CSS tests . .

As described above, according to this embodiment, by providing the overcoat layer 4 mainly composed of the phosphazene-based photocurable resin 1, the alumina fine particles 2, and the lubricant 3, the C
A magneto-optical disk having excellent SS durability can be provided.

In this embodiment, the overcoat layer 4 and the magneto-optical recording medium 5 are in direct contact with each other, but when an inorganic compound or an organic compound film is provided between the overcoat layer 4 and the magneto-optical recording medium 5. The same effect can be obtained in

An embodiment of the method of manufacturing a magneto-optical disk according to the present invention will be described below with reference to the drawings.

FIG. 3 is a block diagram showing a step of forming an overcoat layer in a method for manufacturing a magneto-optical disk according to one embodiment of the present invention. 4 is an optical microscope photograph of the surface of the overcoat layer of the magneto-optical disk manufactured by the manufacturing method of the present invention. FIG. 5 is a schematic cross-sectional view of the overcoat layer of the magneto-optical disk completed by the manufacturing method of the present invention up to the curing step. FIG.

In FIG. 4, a portion that looks circular is a depression 8 on the overcoat layer 4 shown in FIG. In FIG. 5, 1 is a photocurable resin, 2 is alumina fine particles, 7 is a lubricant , 4 is a photocurable resin 1, alumina fine particles 2 and a lubricant 7.
5 is a magneto-optical recording medium, and 6 is a polycarbonate substrate.

Next, the step of forming the overcoat layer 4 of the magneto-optical disk shown in FIG. 3 will be described with reference to FIGS. 3, 4 and 5.

First, a photocurable resin 1, a liquid lubricant 7 which is hardly soluble in the photocurable resin 1, has a low specific gravity and does not have photocurability, and alumina fine particles 2 are prepared.
(S1). Phosphazene photocurable resin as a photocurable resin 1 in the present embodiment (Idemitsu Chemical Co., Ltd., trade name PPZ), Jun
Using a mixture of stearic acid n-butyl and oleyl oleate as Lubricant 7. The alumina fine particles 2 may have a center particle diameter of a submicron order.

Next, the photo-curable resin 1, the lubricant 7, and the alumina fine particles 2 are made into a suspended mixed liquid by using a stirring means such as a shaker, a sand mill, a ball mill or the like (S2). A droplet is applied on the magneto-optical recording medium 5 formed thereon. And the polycarbonate substrate 6
Is rotated at a rotation speed of about 1,000 to 3,000 rpm, and the applied mixed liquid is applied and formed to a predetermined thickness on the surface of the magneto-optical recording medium 5 (S3). Thereafter, the liquid mixture formed to a predetermined thickness on the magneto-optical recording medium 5 is irradiated with ultraviolet rays to cure the photocurable resin 1 in the liquid mixture (S4, S5). Lubricant 7
Is a liquid because it does not have photocurability, and is hardly soluble in the photocurable resin 1. Since its specific gravity is smaller than that of the photocurable resin 1, it is determined from the surface tension of the surface of the overcoat layer 4. It precipitates in a roughly spherical shape of a certain size.

Subsequently, isopropyl alcohol (IPA)
The lubricant 7 on the overcoat layer 4 is removed by (S6).
The isopropyl alcohol is dried and removed (S7), and the process ends.

The depression 8 shown in FIGS. 4 and 5 is formed on the surface of the overcoat layer 4 by the above-described method of manufacturing a magneto-optical disk according to the present invention. The depth and area of the depression are determined by the selection of the photo-curable resin 1 and the lubricant 7, and as shown in this embodiment, the photo-curable resin 1 includes a phosphazene-based photo-curable resin and a lubricant . When a mixed solution of n-butyl stearate and oleyl oleate is used as 7, the ratio of the photocurable resin 1 to the lubricant 7 is 10: 1 and the diameter is 3
A substantially circular depression having a thickness of about 5 μm and a depth of 0.2 to 0.4 μm can be formed on the surface of the overcoat layer 4.

FIG. 6 shows the magneto-optical disk shown in FIG.
The error rate is shown when the SS test is performed 10,000 times in a dust environment having a particle size of 2 μm or less and then left in an environment of 80 ° C. and 80% RH for 1000 hours. In FIG. 6, a characteristic C indicates a change in the occurrence of an error in the magneto-optical disk manufactured by the manufacturing method according to the present invention, and a characteristic D indicates an error in the magneto-optical disk in which the substrate material of the conventional magneto-optical disk is changed from glass to polycarbonate. It is a change in occurrence. As is clear from FIG. 6 , the error occurrence rate sharply increases with the increase in the number of dust particles in the characteristic D, but the error occurrence rate does not sharply increase with the increase in the number of dust particles in the characteristic C. .

The reason is considered as follows. That is, the dust particles used in the experiment have a particle size of 2 μm or less, and are smaller than the flying height of the magnetic head slider. For this reason, after recording / reproducing information on the magneto-optical disk, the disk rotation drive device 22 is stopped, and when the slider 18 and the magnetic head 19 shift from the floating traveling to the sliding traveling, the slider 18 and the magnetic head 19 and the overcoat layer 4 are moved. Rolls while dust particles are sandwiched between. At this time, in the case of the characteristic D of the conventional example, the dust particles damage the crash prevention film 16 (see FIG. 7) while the dust particles are sandwiched between the slider 18 and the magnetic head 19 and the overcoat layer 4.

On the other hand, in the case of the characteristic C of the present invention, the dust particles are interposed between the slider 18 and the magnetic head 19 and the overcoat layer 4. Since the depression 8 shown in FIG. 5 is formed, dust particles enter and are trapped in the depression 8, and the rolling of the dust particles is limited to a short distance, so that damage to the overcoat layer 4 is reduced, and The occurrence is prevented.

As described above, the photocurable resin 1 and the liquid lubricant 7 which is hardly soluble in the photocurable resin 1 and has a low specific gravity and no photocurability are mixed and then applied to a disk. By combining the means, the photo-curing means, and the means for removing the liquid lubricant 7 , a magneto-optical disk can be manufactured with a simple facility construction and with less occurrence of scratches when dust adheres.

[0044]

As described above, the present invention provides a resin substrate made of polycarbonate or the like by providing an overcoat layer containing a phosphazene-based photocurable resin, an inorganic compound powder and a fatty acid ester-based lubricant as main components. Also, a magneto-optical disk having a high crash prevention effect can be provided.

Means for mixing a photocurable resin and a liquid lubricant which is hardly soluble in the photocurable resin, has a low specific gravity and has no photocurability, and applies the mixture to a magneto-optical disk; By combining the means for removing the post-liquid lubricant , it is possible to manufacture a magneto-optical disk capable of reducing the occurrence of errors when dust adheres.

[Brief description of the drawings]

FIG. 1 is a schematic view of an overcoat layer of a magneto-optical disk according to one embodiment of the present invention.

FIG. 2 is a diagram showing a change in occurrence of an error between the present invention and a conventional example with respect to the number of CSS tests of the magneto-optical disk of FIG. 1;

FIG. 3 is a block diagram showing a step of forming an overcoat layer in the method of manufacturing a magneto-optical disk according to one embodiment of the present invention.

FIG. 4 is a diagram showing a surface of an overcoat layer of a magneto-optical disk manufactured by the manufacturing method of the present invention.

FIG. 5 is a schematic sectional view of an overcoat layer of a magneto-optical disk manufactured by the manufacturing method of the present invention.

FIG. 6 is a diagram showing a comparison between an error occurrence change with respect to a dust amount of a magneto-optical disk manufactured by the manufacturing method of the present invention and an error occurrence change with a conventional example.

FIG. 7 is a sectional view showing a schematic configuration of a magneto-optical disk in a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Phosphazene type photocurable resin, 2 ... Alumina fine particle, 3 ... Lubricant, 4 ... Overcoat layer, 5 ... Magneto-optical recording medium, 6 ... Polycarbonate substrate, 7 ... Lubricant , 8 ... Dentation, 20 ... objective lens, 21 ... laser light,
22 ... Disk rotation drive.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-40149 (JP, A) JP-A-1-143015 (JP, A) JP-A-64-70944 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) G11B 11/10 521 G11B 11/10 541 G11B 5/64 G11B 5/84

Claims (4)

(57) [Claims] 1. An overcoat layer comprising a phosphazene-based photocurable resin represented by the general formula (1), an inorganic compound powder and a fatty acid ester-based lubricant as main components ,
A magneto-optical disk used on a magneto-optical recording medium formed on a substrate . Embedded image 2. A photo-curable resin and a liquid lubricant that is hardly soluble in the photo-curable resin, has a small specific gravity and does not have photo-curability on a magneto-optical recording medium formed on a polycarbonate substrate. A step of applying a suspension of the mixed solution to a predetermined thickness on the surface of the magneto-optical recording medium to form a coating film,
Irradiating the coating film with ultraviolet light to cure the photocurable resin
A step, the lubricant of the cured surface of the coating film removing
Forming an overcoat layer by performing the method described above. 3. The method according to claim 2, wherein the photocurable resin is a phosphazene-based photocurable resin represented by the general formula (1). 4. The method for manufacturing a magneto-optical disk according to claim 2, wherein the lubricant is a fatty acid ester-based fat or oil.