JP2003242698A - Magneto-optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film surface incidence type magneto-optical disk which is provided with a surface protective layer having an excellent sliding resistance characteristic and an antistatic function. <P>SOLUTION: The surface protective layer of a magneto-optical disk 100 consists of three layers: a transparent resin layer; a hard coat layer; and an antistatic coat layer. The electrical resistivity of the surface protective layer is ≥1.5×10<SP>11</SP>Ω/cm<SP>2</SP>, pencil hardness is ≥F, and the film thickness of the surface protective layer is 2.5 to 25 μm. As a result, it is possible to suppress a dust collection effect by providing a disk surface with an antistatic effect and to improve the durability of the disk surface with respect to the sliding of a floating head at recording or reproduction. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a flying head to stack a reflective layer, a recording layer, a transparent dielectric layer, and a surface protective layer on a substrate in this order, and irradiates a laser beam from the surface protective layer side. The present invention relates to a magneto-optical disk for recording / reproducing, and more specifically to a magneto-optical disk having excellent scratch resistance and antistatic ability.

[0002]

2. Description of the Related Art With the advent of the multimedia age, an optical disk capable of recording a large amount of information at a high density and rapidly recording and reproducing is attracting attention. The optical disc is
Uses a read-only optical disc such as a CD or a laser disc (registered trademark) that can only reproduce information, a write-once optical disc that allows recording only once such as a CD-R, a magneto-optical recording system or a phase change recording system. It is classified into a rewritable optical disc or the like that can rewrite and erase information as many times as necessary. Among these optical discs, magneto-optical discs are mainly used in fields requiring a high transfer rate, but with the increase in the amount of information handled in the past few years, the recording capacity should be further increased in optical recording. Is required.

In order to meet this demand, a method is proposed in which a flying head equipped with an objective lens having a high numerical aperture (NA) and a magnetic field generating coil irradiates a laser beam while seeking on the surface of a magneto-optical disk for recording / reproducing. Has been done. A magneto-optical disk compatible with this recording / reproducing system is provided with at least a reflective film, a recording layer, a transparent dielectric layer, and a surface protective layer in this order on a substrate provided with lands or grooves so that land recording or groove recording can be performed. It has a laminated structure.

In the above recording / reproducing system, since recording / reproducing is performed by the flying head, there is a possibility that the head may come into contact with the disk surface when the flying head performs seek operation or load / unload operation. It is necessary to prevent or suppress damage to the disk surface or the flying type head that occurs due to this head contact. Also, when dust or the like adheres to the disk surface due to the charging of the magneto-optical disk surface,
Dust obstructs the path of laser light irradiation and causes an error when reading and writing data. In the worst case, the dust that adheres may trigger the floating head to crash.

In order to solve the above problems, for example, Japanese Patent No. 3078006 proposes to provide an ultraviolet-curable resin layer having high hardness and low resistance as a surface protective layer of an optical disk.

[0006]

However, when it is attempted to improve the antistatic ability of the ultraviolet curable resin layer,
Usually, a decrease in hardness is unavoidable, and the light transmittance of the ultraviolet curable resin layer also decreases. In fact, there is a limit in satisfying all desired functions such as antistatic property and high hardness with only one resin layer.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a magneto-optical disk having excellent antistatic ability and sliding resistance.

[0008]

An object of the present invention is to form a surface protective layer from three layers of a transparent resin layer, a hard coat layer and an antistatic coat layer, the thickness of the hard coat layer being the thickness of the transparent resin layer. The same or more, the thickness of the antistatic coating layer
0.5 μm or more, the total thickness of the transparent resin layer and the hard coat layer is 2 μm to 20 μm, and the electric resistivity of the magneto-optical disk surface is 1.5 × 10 ¹¹ Ω / cm ² or less, and the pencil hardness is F or more. ,
By using a magneto-optical recording medium having a total thickness of the surface protective layer of 2.5 μm to 25 μm, it has excellent antistatic ability and sliding resistance.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of a magneto-optical disk invented to achieve the above object is shown in FIG. FIG. 1 is a structural sectional view of a magneto-optical disk 100. The magneto-optical disk 100 has a reflective layer (2), a recording layer (3), a transparent dielectric layer (4), and a surface protective layer (5) laminated in this order on a substrate (1). The surface protective layer (5) is composed of a transparent resin layer (6), a hard coat layer (7) and an antistatic coat layer (8). The transparent resin layer (6) is laminated in order to prevent corrosion of the magneto-optical disc laminated film and to protect the disc surface from external impact. Since the flying head is present on the surface protection layer (5) in this recording / reproduction system, it is more transparent and has better sliding resistance than the surface protection layer of the type of optical disk in which light is incident from the base side that has been used conventionally. It is necessary to stack resin layers.
Therefore, the hard coat layer (7) is formed on the transparent resin layer (6).
Were laminated. The pencil hardness of the hard coat layer is preferably F or higher, and particularly preferably 2H or higher. Further, when the surface electric resistance value of the protective layer is high, dust easily adheres to the surface thereof, which causes a head / disk crash. Therefore, an antistatic coat layer was formed on the hard coat layer (7). Considering mass production, it is preferable that the number of layers constituting the transparent resin layer (5) be smaller and have the disk protection, the sliding resistance and the antistatic effect at the same time. It is very difficult to achieve a desired characteristic value while taking into consideration the adhesiveness with the transparent resin layer, the hardness, the antistatic effect, and the light transmission characteristic. Therefore, the surface protective layer of the magneto-optical disk of the present invention has a three-layer structure including a transparent resin layer, a hard coat layer, and an antistatic coat layer.

In the magneto-optical disk 100, an antistatic coating layer (8) is formed on the substrate surface opposite to the substrate surface on which the recording layer (3) is present. If necessary, one or both of the transparent resin layer (6) and the hard coat layer (7) may be formed between the antistatic coating layer (8) and the substrate (1). .

The substrate (1) used in the magneto-optical disk of the present invention is made of resin such as polycarbonate, polyolefin, polymethyl acrylate, polystyrene and nylon, as well as metal such as glass, silicon, thermally oxidized silicon, aluminum and titanium. A disc substrate made of a metal can be used.

As the reflective layer (2) of the present magneto-optical disk, simple metals or alloys of noble metals such as Au, Ag and Cu, these noble metals and other transition group metals, Si, Ge, Sn, Pb, Al, Ga,
An alloy with In or the like, a simple substance of Al or an alloy with another metal can be used. The reflective layer (2) may have a laminated structure of two or more layers having different compositions. Also a reflective layer (2)
Between the substrate and the substrate (1) to improve corrosion resistance, adhesion, etc.
A ceramic layer such as iNx, AlNx, SiCx, SiOx, SiNxOy, GexN, and GeNxOy, and a nonmagnetic transition metal layer such as Ti, Cr, Zr, Nb, and Ta may be formed.

As the recording layer (3) of the present magneto-optical disk, a rare earth-transition metal amorphous alloy such as TbFeCo, DyFeCo, DyTbFeCo and GdFeCo, a laminated film of a noble metal such as Co and Pt and a transition ferromagnetic metal can be used. Is. Cr, Nb, Pt, Ni, Ta, etc. may be contained in these alloys. Further, it is possible to use a laminate of two or more layers of amorphous materials having different compositions or a combination of an amorphous film and a laminated film.

As the recording layer (3), a single layer magneto-optical recording film such as TbFeCo or a film composed of a plurality of magnetic super-resolution type magnetic films can be used. The structure of the recording / reproducing layer in the case of this magnetic super-resolution type is such that the recording film (3) is
When viewed from the light incident side, the reproduction layer of GdFeCo, the mask layer of GdFe,
It is a magnetostatically coupled CAD-type magnetic super-resolution structure composed of a non-magnetic layer and a recording layer mainly composed of TbFeCo. As the non-magnetic layer, a non-magnetic metal such as Al, Ti or Zr can be used in addition to a ceramic layer such as SiNx or AlNx. The recording / reproducing layer may be an exchange coupling type CAD type magnetic super-resolution type without a non-magnetic layer.

SiNx, AlNx, SiCx, SiOx, SiNxOy, GexN, GeNx are provided between the reflective layer (2) and the recording layer (3) for thermal control.
A ceramic layer such as Oy, a nonmagnetic transition metal layer such as Ti, Cr, Zr, Nb, and Ta, and a semiconductor layer such as Si, Ge, ZeS, and ZeSe may be formed.

As the transparent dielectric layer (4) of the present magneto-optical disk, SiNx, SiOx, SiCx, SiNxOy, SiCxOy, SiNxCyO are used.
z, AlNx, AlOx, AlNxOy, ZrOx, ZnS, ZnS- (SiO2) x, Z
A transparent ceramic layer such as rOx, TiOx, DLC carbon can be used.

The material of the transparent resin layer (6) of the present magneto-optical disk is polyester, epoxy, polyurethane,
Photopolymerizable oligomers such as polyether acrylate, monofunctional and polyfunctional acrylates, photopolymerizable monomers such as monofunctional and polyfunctional methacrylates, and ultraviolet rays containing photoinitiators (benzoin-based, acetophenone-based, peroxide-based, etc.) as main components A curable resin can be used. If necessary, a sensitizer, a leveling agent, a plasticizer, an inorganic / organic filler, a thermal polymerization inhibitor, a thixotropic agent, a non-reactive monomer, an organic solvent may be selectively added to the above ultraviolet curable resin. You may.

Hard coat layer (7) of the present magneto-optical disk
As the material of the above, use a photocurable resin containing the above-mentioned ultraviolet curable resin, or this photocurable resin to which various metal oxides such as SiO2 and TiO2 and inorganic fine particles (filler) are added. You can At this time, the solid content weight of the entire material is preferably 10-85%, particularly 40-60%, and the inorganic component weight in the solid content is preferably 10-50%, particularly 35-50%.

Antistatic coating layer of the present magneto-optical disk
As the material of (8), the light containing the above-mentioned UV curable resin is used.
Add various metal oxides and inorganic fine particles (file
It is possible to use a photocurable antistatic agent in which
it can. As the above fine particles, In ₂O₃, SnO₂, Injiu
Mu-tin composite oxide (ITO), MoO₂, Sb₂O₃, IrO₃, Si
O₂, Al₂O3 can be used as a useful material
It At this time, the solid content weight of the entire material and the solid content
The weight of the inorganic component to be contained is preferably within the above range.

The transparent resin layer (6), the hard coat layer (7) and the antistatic coat layer (8) are coated with the resin material of each layer on the disk by a spin coating method and subjected to an appropriate treatment (for example, irradiation with ultraviolet rays) for curing. ) Is performed. It is possible to determine the film thickness of the transparent resin layer (6), hard coat layer (7) and antistatic coat layer (8) by controlling the number of revolutions of the disc during coating, the rotation time, and the amount of resin applied during coating. it can. Considering the corrosion resistance and sliding resistance of the disc, the thickness of the hard coat layer (7) is equal to or greater than the thickness of the transparent resin layer (6), and the thickness of the transparent resin layer (6) and the hard coat layer are Total thickness is 2 μm to 20 μm, especially 5 μm to 20 μm
It is preferably μm. If the hard coat layer (7) is thinner than the transparent resin layer (6), the hardness of the surface protective layer will be insufficient and the durability of the disk will be deteriorated. When the total thickness of the transparent resin layer (6) and the hard coat layer is 2 μm or less,
Corrosion resistance and sliding resistance are not sufficient, and the effect as disk protection is weak. Further, when the thickness is 20 μm or more, the protection effect does not improve so much, so it was determined that sufficient disk protection effect can be obtained if the thickness is 2 μm to 20 m in consideration of economical efficiency and productivity. Therefore, the total thickness of the transparent resin layer (6) and the hard coat layer is preferably 2 μm to 20 μm. Further, it is desirable that the transparent resin layer has a pencil hardness of 2B or more, and the hard coat layer has a pencil hardness of H or more, particularly 2H or more.

The thickness of the antistatic protective coat layer (8) is 0.5 μm.
It is preferably m or more, particularly 1 μm or more. If it is 0.5 μm or less, the antistatic effect does not function sufficiently. It is desirable that the surface of the antistatic coating layer has an electric resistivity of 5 × 10 ¹⁰ Ω / cm ² or less.

The thickness of the hard coat layer (7) is equal to or greater than the thickness of the transparent resin layer (6), and the total thickness of the transparent resin layer (6) and the hard coat layer (7) is 2 μm to 20 μm.
When the thickness of the antistatic protective coat layer is 0.5 μm or more, the surface protective layer (5) composed of the transparent resin layer (6), the hard coat layer (7) and the antistatic coat layer (8) is formed. The film thickness is preferably 2.5 μm to 25 μm. If the hard coat layer (7) is thinner than the transparent resin layer (6), the hardness of the surface protective layer will be insufficient and the durability of the disk will be deteriorated. When the film thickness of the surface protective layer (5) is 2 μm or less, the disk cannot be sufficiently protected and the antistatic effect cannot be expected. Further, when the thickness is 25 μm or more, no noticeable improvement in sliding resistance and antistatic effect was observed.

The present invention is applicable not only to the magneto-optical disk shown in FIG. 1 but also to a magneto-optical disk (magneto-optical disk 200) capable of recording and reproducing from both sides of the disk as shown in FIG.

Based on the above-mentioned examination results, the surface electric resistance value of the magneto-optical disk was 1 × 10 ¹¹ Ω / cm ² or less and the pencil hardness was F or more, which had an antistatic effect and excellent sliding resistance. A magneto-optical disk can be provided.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. Example 1 A magneto-optical disk 100 having the structure shown in FIG. 1 was manufactured by the method described below. A substrate (1) was produced by injection compression molding using a stamper and polycarbonate resin in which grooves and pits were formed in advance. The substrate size is 130 mm in diameter. Using an in-line type DC magnetron sputtering device, an Au layer of 50n was formed as a reflective layer (2).
m, a CAD film (TbFeCo film of 50 nm, a silicon nitride layer of 10 nm, a GdFe layer of 30 nm, a GdFeCo layer of 30 nm as a recording / reproducing layer (3).
4 layers were laminated in this order). A 60 nm silicon nitride layer was formed thereon as a transparent dielectric layer (4).

Acrylic UV curable resin (viscosity 140 mPa · s at 25 ° C.) is applied on the transparent dielectric layer (4) by spin coating, and UV irradiation treatment (total illuminance 840 mJ / cm ² ) is performed. Then, a transparent resin layer (6) having a thickness of 4.5 μm was formed. Next, the main components are UV curable resin and SiO ₂ , and the solid content weight of the entire material is 53% in advance so that the pencil hardness of the cured thin film is 2H, and the SiO ₂ component weight in the solid content is 40%. Photocurable coating agent A (viscosity at 25 ° C: 45mPa ・ s)
Is applied onto the transparent resin layer (6) by spin coating and the temperature is 70 ° C.
A hard coat layer (7) having a thickness of 8.5 μm was formed by performing heat treatment and ultraviolet irradiation treatment (total illuminance: 1000 mJ / cm ² ). Finally, the main components are UV curable resin and ITO filler, the solid content weight of the entire material is 50% in advance so that the surface resistivity is 1.4 × 1010 Ω / cm ^2, and the ITO component weight in the solid content is 30%. % Of the photo-curable coating agent B (viscosity 29 mPa · s at 25 ° C) was applied on the hard coat layer (7) by spin coating, and heat treatment at 50 ° C and UV irradiation treatment (total illuminance 700 mJ / cm2 By carrying out (), an antistatic coat layer (8) having a film thickness of 2.0 μm was formed.

Further, the photocurable coating agent B is applied and cured on the other substrate surface under the same conditions to give a film thickness of 2.0 μm.
Forming an antistatic coating layer (10) of m, magneto-optical disk 1
00 was produced.

The electric resistance value and the pencil hardness of the surface of the magneto-optical disk were measured, and the results are shown in Table 1. These measurements were performed on the substrate surface having the recording layer (on the air bearing surface side of the head).
The surface electrical resistivity was measured according to JIS-K6911 and the pencil hardness was measured according to JIS-K5400.

(Embodiment 2) With the structure shown in FIG. 2, a reflective layer, a recording layer, a transparent dielectric layer, a transparent resin layer, a hard coat layer, and an antistatic coat having the same structure and thickness as those of Embodiment 1 on both sides of the substrate. A magneto-optical disk 200 having layers was produced. Magneto-optical disk 2
The surface electric resistance value and pencil hardness of 00 were measured under the same conditions as in Example 1, and the results are shown in Table 1.

(Comparative Example 1) A magneto-optical disk having the same structure and thickness as in (Example 1) except that the transparent resin layer (6) has a thickness of 7 μm and the hard coat layer (7) has a thickness of 4 μm. Was produced.
The surface electric resistance value and the pencil hardness of the manufactured magneto-optical disk were measured under the same conditions as in Example 1, and the results are shown in Table 1.

(Comparative Example 2) A disk having the same structure and film thickness as in Example 2 except that the film thickness of the antistatic coating layer (7) was 0.3 μm was prepared. The electric resistance value and the pencil hardness of the surface of the manufactured magneto-optical disk were measured under the same conditions as in Example 1,
The results are shown in Table 1.

(Random Seek Test) The magneto-optical disks produced in Examples 1 and 2 and Comparative Examples 1 and 2 were incorporated into the drive described in Japanese Patent Application No. 11-293684, and the flying head had a radius of 28 mm.
From 60 to 60 mm, the degree of scratches on the disk surface (surface protection layer) was examined while randomly seeking. A fluorine-based lubricant was applied to the surface of the magneto-optical disk used in the test. In this test, the number of revolutions of the disk was 2400 revolutions per minute, and the flying height of the flying head was about 1.0 μm. The test conditions were 60 ° C and 80% RH, and a random seek test was conducted for 200 hours continuously. The surface state after random seek was examined visually and with an optical microscope (magnification: 150 times). The surface condition was evaluated on a scale of 5 and the test results are summarized in Table 1. In addition, 100
The surface condition after the time seek is evaluated in the following 5 grades, and 3 or more corresponds to a level where there is no problem in read / write characteristics.

5: No scratches are observed visually or under a microscope. 4: No scratches are visually observed, but when observed with a microscope, several scratches are observed on the entire surface of the disc. 3: Although scratches are visually observed, it is partial (generally about 1/5 of the entire circumference of the disk in an arcuate shape), and numerous small scratches are observed under a microscope. 2: Several scratches extending from about half to the entire circumference and 10 or more small scratches are observed, and countless small scratches are observed under a microscope. 1: Ten or more scratches extending from about half to the entire circumference, and numerous other small scratches are observed. When observed under a microscope, countless small scratches are observed.

[0034]

[Table 1]

* 1: In the observation of the surface of the magneto-optical disk after the test, the number of minute dusts counted was more than twice that of the surface of other magneto-optical disks.

[0036]

The surface protective layer (5) of the magneto-optical disk of the present invention comprises three layers of a transparent resin layer (6), a hard coat layer (7) and an antistatic coat layer (8). The thickness of (7) is equal to or greater than the thickness of the transparent resin layer (6), and the total thickness of the transparent resin layer and the hard coat layer is 2
μm to 20 μm, 0.5 μm thick on top of hard coat layer
By forming the above antistatic protective coat layer, the electrical resistivity of the magneto-optical disk surface is 1.5 × 10 ¹¹ Ω / cm ² or less and the pencil hardness is F or more, the film thickness of the surface protective layer 2.5μm ~ 2
It was 5 μm. As a result, it was possible to impart an excellent antistatic ability to the surface of the magneto-optical disk and improve the durability of the disk surface against sliding of the flying head during recording / reproduction.

[Brief description of drawings]

FIG. 1 is a schematic sectional view illustrating a structure of a magneto-optical disk of the present invention.

FIG. 2 is a schematic sectional view illustrating the structure of the magneto-optical disk of the present invention.

[Explanation of symbols]

1 substrate 2 reflective layer 3 recording layers 4 Transparent dielectric layer 5 Surface protection layer 6 Transparent resin layer 7 Hard coat layer 8, 9 Antistatic coating layer

Claims (2)

[Claims] 1. A substrate, at least a reflective layer, a recording layer, and
In a magneto-optical disk in which a transparent dielectric layer and a surface protective layer are laminated in this order, and laser light from a flying head is irradiated from the surface protective layer side for recording and reproduction, the surface protective layer is a transparent resin layer and a hard disk. It is composed of three layers of a coat layer and an antistatic coat layer, the thickness of the hard coat layer is equal to or more than the thickness of the transparent resin layer, the thickness of the antistatic coat layer is 0.5 μm or more, the transparent resin layer and the hard layer. The total film thickness of the coating layer is 2 μm to 20 μm, and the electrical resistivity of the magneto-optical disk surface is 1.5 × 10 ¹¹ Ω / cm ² or less,
The pencil hardness is F or more, and the film thickness of the surface protective layer is 2.5 μm to 2
A magneto-optical disk characterized by being 5 μm. 2. The magneto-optical disk according to claim 1, wherein the flying height of the flying head is 5 μm or less.