JPH05166234A - Magneto-optical disk and its production - Google Patents

Abstract

PURPOSE:To improve the effect of preventing clash even if a resin substrate consisting of polycarbonate, etc., is used by providing an over coating layer essentially consisting of phosphazene photosetting resin, inorg. compd. powder and lubricant. CONSTITUTION:The magneto-optical disk is formed by providing a magneto- optical recording medium 5, the phosphazene photosetting resin 1, and the over coating layer 4 essentially consisting of alumina particulates 2 and the lubricant 3 of a fatty acid ester system on the polycarbonate substrate 6. A slider 18 comes into contact with the layer 4 and a part of the lubricant 3 bleeds out on the surface of the layer 4 to decrease the coefft. of friction between the layer 4 and the slider 18 when a disk rotational driving device 22 is held static in the contact start-stop operation of this disk. Then, the slider 18 glides and floats smoothly when the device 22 starts driving. The slider shifts from floating travel to gliding travel and stop smoothly on the layer 4 when the device 22 stops. The disk having the high effect of preventing the clash is obtd. by the combined effect of the layer 4 in such a manner.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overwritable magnetic field modulation type magneto-optical disk and a method of manufacturing the same.
The present invention relates to an overcoat layer required 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 it is a recording mode that requires an erasing mode and a writing mode. Therefore, there is a problem that the transfer rate of information is slow.

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

The magnetic field modulation method is a method of fixing the intensity of laser light and modulating the direction of an externally applied magnetic field. As a means for generating the modulated externally applied magnetic field, there is, for example, a floating magnetic head used in a magnetic disk device (for example, Japanese Patent Laid-Open No. 63-29643). This can modulate the current applied to the coil of the magnetic head to modulate the externally applied magnetic field.

The above-mentioned conventional example will be described below with reference to the drawings.

FIG. 7 is a sectional view showing a schematic structure of a conventional magneto-optical disk. In FIG. 7, 11 is a transparent glass substrate, 12 is an ultraviolet curable resin film having a pregroup pattern (usually 10 to 100 μm in thickness), and 13 is a first protective film composed of ZnS or SiN (usually 60 in thickness). ~ 150nm), 14 is TbFeCo
Magneto-optical recording film (usually 20-150 nm thick), 15 is ZnS or S
A second protective film composed of iN (usually a thickness of 60 to 150 nm), 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) 1 μm), 17 is a fluorocarbon 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 device. The slider 18 and the objective lens 20 are movable in a state of being arranged at positions facing each other across the magneto-optical disk.

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

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

When the disk rotation drive device 22 is driven, the slider 18 slides on the surface of the fluorocarbon oil 17.
When the rotation speed of the disk rotation drive device 22 increases and the relative speed between the slider 18 and the anti-crush film 16 reaches approximately 1 m / s or more, the slider 18 and the magnetic head 19 fixed to the slider 18 are fluorinated. Carbon oil 17
Emerge from the surface.

After the slider 18 and the magnetic head 19 have floated,
The objective lens 20 and the laser light 21 arranged at a position facing the magnetic head 19 are simultaneously accessed by an access drive system (not shown).
To move to an arbitrary position on the magneto-optical disk, locally heat the magneto-optical recording film 14 with the laser light 21,
Information is written and recorded in the magneto-optical recording film 14 by passing a modulation current through a coil 19 (not shown). When reproducing information, the magnetic head 19 outputs a demodulation current by the same operation.

When the recording / reproducing of information to / from 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 floating to gliding, and the fluorocarbon oil 17 is used as a lubricant. As it travels in contact, it rests on the crash prevention membrane 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, and the magnetic head 19 and It is necessary to make the distance between the magneto-optical recording films 14 as close as possible. In addition, the floating magnetic head 19 uses the gas lubrication action to achieve a low flying height on the crash prevention film 16.
(For example, a few μm or less), contact start stop (hereinafter CS
(Abbreviated as S) method is essential.

In order to perform the CSS method in the magneto-optical disk, (1) the disk crash prevention film 16 surface and the magnetic head slider 18 surface do not stick to each other when the magneto-optical disk is stationary, and (2) the rotation start of the magneto-optical disk. The magnetic head 19 does not destroy the magneto-optical recording layer 14 of the magneto-optical disk when the magnetic head is in contact with the magnetic head when stopped, and (3) dust that prevents the magnetic head 19 from flying does not adhere to the slider surface of the magnetic head. It is necessary.

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

[0015]

However, in the above structure, since the glass substrate is used and the ultraviolet curable resin film having the groove formed thereon is formed, the material cost and the manufacturing cost are increased and the optical cost is increased. 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 weaker mechanical strength than glass, and the crash-preventing film 16 made of epoxy resin has a low crash-preventing effect. Had.

Further, in the above structure, when dust having a size of the order of submicron 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 long scratches will be generated in the track direction of the magnetic disk, and an error may occur, making it impossible to correct the error.

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 particles enter. A magneto-optical disk having an overcoat layer for crash prevention and a method for manufacturing the same are provided.

[0019]

The magneto-optical disk of the present invention comprises an overcoat layer containing a phosphazene-based photocurable resin, an inorganic compound powder and a fatty acid ester-based lubricant as main components.

Further, a magneto-optical recording medium formed on a polycarbonate substrate, a photocurable resin, and a liquid additive which is hardly soluble in the photocurable resin and has a small specific gravity and does not have photocurability. Means for applying a mixed liquid suspension to the surface of the magneto-optical recording medium to form an overcoat layer, and means for irradiating the overcoat layer with ultraviolet rays to cure the photocurable resin And a means for removing the additive in the cured overcoat layer.

[0021]

According to the present invention, even when a resin substrate such as a polycarbonate is used, a combination of a phosphazene-based photocurable resin having a high hardness, an inorganic compound powder and a resin acid ester-based lubricant has a combined effect of preventing a crash. It is possible to provide a high magneto-optical disk. In addition, a retreat space for the dust that has entered can be formed on the surface of the overcoat layer by the above-described means, and it is possible to prevent the occurrence of a fatal scratch defect on the disk due to the movement of the dust.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A magneto-optical disk according to an 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 an embodiment of the present invention. In FIG. 1, 1 is a phosphazene-based photocurable resin
(Made by Idemitsu Chemical Co., Ltd., product name PPZ), 2 has a central particle size of about 0.
6 μm alumina fine particles (Sumitomo Chemical Co., Ltd., trade name AKP
-20), 3 is a lubricant composed of n-butyl stearate and oleyl oleate, 4 is an overcoat layer containing phosphazene photocurable resin 1, alumina fine particles 2 and lubricant 3 as main components, 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 laser light, 22 is a disk rotation drive device.

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

When the disk rotation driving device 22 is stationary, the slider 18 is in contact with the overcoat layer 4. Since a part of the lubricant 3 exudes to the surface of the overcoat layer 4, the dynamic friction coefficient between the overcoat layer 4 and the slider 18 is
It will be 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 is approximately 1 m /
When reaching s or more, the slider 18 and the magnetic head 19 float above the overcoat layer 4.

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

When the recording / reproducing of information to / from 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 flying to gliding and rest on the overcoat layer 4. This series of operations is called CSS.

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

As can be seen from the figure, in the characteristic A, the error occurrence rate does not change even if the CSS number increases, but in the characteristic B, the error occurrence rate is 5 × 10 ⁶ after the CSS number is 100,000 times.
To 7 × 10 ~ ⁵ .

As described above, according to this embodiment, by providing the overcoat layer 4 containing phosphazene-based photocurable resin 1, alumina fine particles 2 and lubricant 3 as main components, 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. However, when an inorganic compound or 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 for manufacturing a magneto-optical disk of the present invention will be described below with reference to the drawings.

FIG. 3 is a block diagram showing steps of forming an overcoat layer in the method of manufacturing a magneto-optical disk according to an embodiment of the present invention. Further, FIG. 4 is an optical micrograph of the surface of the overcoat layer of the magneto-optical disk manufactured by the manufacturing method of the present invention, and 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 until the curing step. It is a figure.

The circularly visible portion in FIG. 4 is the recess 8 on the overcoat layer 4 shown in FIG. In FIG. 5, 1 is a photocurable resin, 2 is alumina fine particles, 7 is an additive, 4 is a photocurable resin 1, alumina fine particles 2 and an additive 7.
Is a magneto-optical recording medium, and 6 is a polycarbonate substrate.

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

First, the photocurable resin 1, the liquid additive 7 which is hardly soluble in the photocurable resin 1, has a small specific gravity and does not have a photoeffect, and the alumina fine particles 2 are prepared.
(S1). In this example, a phosphazene-based photocurable resin (made by Idemitsu Kagaku Kogyo, trade name PPZ) is used as the photocurable resin 1, and a mixed liquid of n-butyl stearate and oleyl oleate is used as the additive 7. It suffices that the alumina fine particles 2 have a center particle size of submicron order.

Next, the photocurable resin 1, the additive 7 and the alumina fine particles 2 are made into a suspension liquid mixture by using a stirring means such as a shaker, a sand mill or a ball mill (S2), and the liquid mixture is used for the polycarbonate substrate 6 A droplet is applied onto the magneto-optical recording medium 5 formed above. Then, the polycarbonate substrate 6
Is rotated at a rotation speed of about 1000 to 3000 rpm, and the mixed liquid applied is applied and formed on the surface of the magneto-optical recording medium 5 to a predetermined thickness (S3). After that, 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). Additive 7
Is a liquid state 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, the surface tension of the overcoat layer 4 is determined by its surface tension. It becomes a substantially spherical shape and precipitates.

Subsequently, isopropyl alcohol (IPA)
And remove the additive 7 on the overcoat layer 9 (S6),
Isopropyl alcohol is dried and removed (S7), and the process is completed.

The depression 8 shown in FIGS. 4 and 5 is formed on the surface of the overcoat layer 4 by the above-described method for manufacturing a magneto-optical disk of the present invention. The depth and area of the depression are determined by selecting the photocurable resin 1 and the additive 7. As shown in this example, the photocurable resin 1 is a phosphazene-based photocurable resin and an additive. When a mixture of n-butyl stearate and oleyl oleate is used as 7, the ratio of the photocurable resin 1 to the additive 7 is 10: 1 and the diameter is 3
A substantially circular recess having a depth of ˜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 of FIG.
The error rate is shown when the SS test is performed 10,000 times in a dust environment with a particle size of 2 μm or less and then left in an 80 ° C., 80% RH environment for 1000 hours. In FIG. 6, a characteristic C is a change in error occurrence of the magneto-optical disk manufactured by the manufacturing method of the present invention, and a characteristic D is light in which the substrate material of the magneto-optical disk in the configuration of the conventional example is changed from glass to polycarbonate. This is a change in the occurrence of an error in the magnetic disk. As is clear from the figure, the characteristic D
In the characteristic C, the error occurrence rate sharply increases with an increase in the number of dust particles, but in the characteristic C, the error occurrence rate does not increase rapidly with an increase in the number of dust particles.

The reason for this is considered as follows. That is, the dust particles used in the experiment have a particle size of 2 μm or less, which is smaller than the flying height of the magnetic head slider. Therefore, after the information is recorded / reproduced on / from the magneto-optical disk, the disk rotation driving device 22 is stopped, and when the slider 18 and the magnetic head 19 shift from the flying run to the gliding run, the slider 18 and the magnetic head 19 and the overcoat layer 4 are moved. Dust particles are caught between and roll. 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 sandwiched between the slider 18 and the magnetic head 19 and the overcoat layer 4, and the surface of the overcoat layer 4 is shown in FIG. Since the dimples 8 shown in FIG. 5 are formed, the dust particles enter the dimples 8 and are captured, and the rolling of the dust particles is limited to a short distance. Occurrence is prevented.

As described above, the photo-curable resin 1 and the liquid additive 7 which is hardly soluble in the photo-curable resin 1 and has a small specific gravity and no photoeffect are mixed and then applied to the disc. By combining the photo-curing means and the means for removing the liquid additive, it is possible to manufacture a magneto-optical disk with few scratches when dust adheres by a simple equipment construction.

[0044]

As described above, the present invention provides a resin substrate such as polycarbonate 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. Even when using, a magneto-optical disk having a high crash prevention effect can be provided.

Further, a photo-curing resin and a liquid additive which is hardly soluble in the photo-curing resin and has a small specific gravity and no photo-curing property are mixed and then applied to a magneto-optical disk, and a photo-curing means. By combining means for removing the post-liquid additive, it is possible to manufacture a magneto-optical disk capable of reducing the occurrence of errors when dust is attached.

[Brief description of drawings]

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

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

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

FIG. 4 is a diagram showing a surface of an overcoat layer of a magneto-optical disk manufactured by a 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 the amount of sand dust of the magneto-optical disk manufactured by the manufacturing method of the present invention and an error occurrence change of the 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-based photocurable resin, 2 ... Alumina fine particles, 3 ... Lubricant, 4 ... Overcoat layer, 5 ... Magneto-optical recording medium, 6 ... Polycarbonate substrate, 7 ... Additive, 8 ... Dimple, 20 ... Objective lens , 21 ... laser light,
22 ... Disk rotation drive.

Claims (4)

[Claims] 1. An overcoat layer comprising a phosphazene-based photocurable resin represented by the general formula (Chemical Formula 1), an inorganic compound powder, and a fatty acid ester-based lubricant as main components on a magneto-optical recording medium. A magneto-optical disk characterized by. [Chemical 1] 2. A magneto-optical recording medium formed on a polycarbonate substrate, a photocurable resin, and a liquid additive which is sparingly soluble in the photocurable resin, has a small specific gravity, and is not photocurable. Means for applying a mixed liquid suspension to the surface of the magneto-optical recording medium to form an overcoat layer, and means for irradiating the overcoat layer with ultraviolet rays to cure the photocurable resin And a means for removing the additive in the cured overcoat layer, the method for producing a magneto-optical disk. 3. The method for manufacturing a magneto-optical disk 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 additive is a resin acid ester-based oil or fat.