JP2001250271A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical recording medium suitable for a surface optical recording medium and a near-field optical recording medium and having a recording film which hardly deteriorates. SOLUTION: In the optical recording medium having at least a reflection layer, an optical recording layer and a lubrication layer formed in this order on a substrate, the contact angle of water on the surface of the lubrication layer is specified to >=70 deg.. As for the material to give the above contact angle, a perfluoropolyether derivative, a fluorine-based polymer having at least one fluorine atom in the monomer structure or a dissolved material of these is useful.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rewritable optical recording medium, and more particularly, to a magneto-optical recording medium for recording, reproducing and erasing information by causing an optical change in a recording layer by a laser beam, or a phase change. It relates to a recording medium.

[0002]

2. Description of the Related Art A conventional rewritable optical recording medium generally forms a multilayer film including a recording layer on a disc-shaped substrate such as plastic, and irradiates a laser from the plastic substrate side to perform recording, reproduction and erasing. Was.

On the other hand, a surface optical recording method in which recording and reproduction are performed by irradiating a laser directly from the recording film side without passing through a plastic substrate, particularly a near-field optical recording method, has recently attracted attention as a means for increasing the density. ing.

[0004] In these recording methods, it is necessary to bring the optical head close to the recording medium.
It has been proposed to use a floating slider head such as an Immersion Lens head.

Similarly, in a hard disk using a slider head, a lubricating layer is often provided on the surface of the medium in order to ensure the floating property of the slider head.

[0006]

In the surface optical recording system, particularly in the near-field optical recording system, the recording film having a multilayer structure including the recording layer is on the surface of the medium, so that the recording film is easily deteriorated by the influence of environment such as humidity. There is a problem.

An object of the present invention is to provide an optical recording medium suitable for a surface optical recording medium whose recording film is unlikely to be deteriorated, particularly a near-field optical recording medium.

[0008]

Means for Solving the Problems In view of the above-mentioned situation, the present inventors have made intensive studies and as a result have completed the present invention.

That is, the present invention provides an optical recording medium having at least a reflective layer, an optical recording layer and a lubricating layer formed on a substrate, wherein the contact angle of water on the surface of the lubricating layer is 70 ° or more. It relates to a recording medium.

Hereinafter, the present invention will be described in detail.

The optical recording medium of the present invention has at least a reflective layer, an optical recording layer and a lubricating layer formed on a substrate. If necessary, a dielectric layer may be provided on the optical recording layer, and a lubricating underlayer may be provided on the dielectric layer.

As the reflection layer of the present invention, for example, a metal material such as aluminum, aluminum alloy, gold, silver or the like can be used. As the optical recording layer, for example, TbFe
Co, DyFeCo, GdTbFeCo, NdDyFe
Magneto-optical recording film of Co or GeSbTe, AgI
It is possible to use a film capable of recording by changing the polarization plane, the reflectance, the phase of light, etc., such as a phase change recording film such as nSbTe.

The contact angle of water on the surface of the lubricating layer of the optical recording medium of the present invention is 70 ° or more, preferably 80 ° or more. If the contact angle of water on the surface of the lubricating layer is less than 70 °, many water molecules will be adsorbed on the medium surface from the atmosphere. In this case, the adsorbed moisture enters the defective portion of the recording film, and is likely to cause corrosion. Surface water contact angle 70 °
In the above case, since water molecules do not adsorb to the medium surface, such a problem does not occur.

As the lubricating layer in the optical recording medium of the present invention, for example, a perfluoropolyether derivative, a fluorine-based polymer having at least one fluorine atom in a monomer structure, and a compatible material thereof can be exemplified.

Even when these lubricating layer materials are used, the contact angle of water on the surface of the lubricating layer changes depending on the material used, the thickness of the lubricating layer and the state of application. It needs to be adjusted so that

The main chain structure of perfluoropolyether is
Although a straight chain structure or a side chain structure may be used, a straight chain structure is particularly desirable from the viewpoint of lubricating properties. As a derivative structure, an alcoholic hydroxyl group (—CH ₂ O) is provided at both ends of the main chain or at one end.
H) and those into which a functional group such as an ester group (—COOR) is introduced, and since the adsorptivity to the lubricating underlayer is higher, it is particularly preferable that the functional groups are present at both ends.

Examples of the ester group include an optionally substituted alkyl group having 1 to 10 carbon atoms.

The weight average molecular weight of the perfluoropolyether derivative is from 1,000 to 10,000, especially from 2,000 to 10,000.
0000 is preferred. If the weight average molecular weight is less than 1000, the fluidity is too high, and the distribution on the medium surface may be likely to be non-uniform. If the weight average molecular weight exceeds 10,000, the fluidity is too low and sufficient lubricating properties cannot be obtained. There is. In addition, low molecular weight compounds have higher long-term stability because the weight loss due to thermal decomposition occurs at a lower temperature than high molecular weight compounds.

Such perfluoropolyether derivatives include, for example, “Fomblin Z DOL” series and “Fomblin Z” manufactured by Ausimont.
DEAL ", manufactured by Daikin, and trade names" Demnum SA "and" Demnum SP ". The “Fomblin Z DOL” series has alcoholic hydroxyl groups at both ends, and as a main chain,

[0020]

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A compound having the formula: "Fomblin Z
DEAL "has ester groups at both ends and has a main chain of

[0022]

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Is a compound having

"Demnum SA" has an alcoholic hydroxyl group at one end, and has, as a main chain,

[0025]

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"Demnum SP"
Has an ester group at one end, and as a main chain,

[0027]

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Is a compound having

The constitution of the fluoropolymer having at least one fluorine atom in the monomer structure is as follows:
It may be a homopolymer or a copolymer. In addition, although it may be partially fluorinated or perfluorinated, a perfluorinated homopolymer is desirable from the viewpoint of heat resistance. Further, from the viewpoints of film formability and light transmittance, an amorphous structure is desirable.

The number average molecular weight of the fluoropolymer is preferably from 10,000 to 200,000, more preferably from 10,000 to 100,000. When the number average molecular weight is less than 10,000, the layer has fluidity, so that it may be difficult to obtain sufficient lubricating properties. Also,
If the number average molecular weight exceeds 200,000, the viscosity of the resulting solution tends to be high, and it may be difficult to form a lubricating layer.

The surface formed by the fluoropolymer is
Since it has a lower energy surface than a case where it is formed of an acrylic material or the like, it has excellent lubricity.

Fluoropolymers have high heat resistance,
Even in a high temperature environment, blackening, coloring, etc. do not occur, and optical characteristics do not change.

Examples of such a fluorine-based polymer include “CYTOP” series manufactured by Asahi Glass, “Teflon AF” series manufactured by DuPont, and the like. The CYTOP series, as the main chain,

[0034]

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"Teflon AF"
The series, as the main chain,

[0036]

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Is a compound having

FIG. 1 is a partial sectional view of one embodiment of the optical recording medium of the present invention. On a substrate 11, a reflective layer 12, an optical recording layer 13 composed of a magneto-optical recording film, a dielectric layer 14, a lubricating underlayer 15, and a lubricating layer 16 are laminated.

The substrate 11 is not particularly limited as long as it satisfies the characteristics of a medium substrate such as mechanical characteristics. Glass, polycarbonate, amorphous polyolefin, thermoplastic engineering plastic, or the like can be used. , Pits, grooves or lands. The reflection layer 1 is provided on the substrate 11.
2 is formed using a metal material such as Al, an Al alloy, Au, or Ag by a sputtering method or a vacuum evaporation method. On the reflective layer 12, a recording layer 13 is formed of TbFeCo, DyFeC.
An optical recording film material such as o, GdTbFeCo or NdDyFeCo is used, and is formed by a sputtering method or a vacuum evaporation method. On this recording layer 13, a dielectric layer 14 is formed of AlN, Si.
A material such as N, Ta ₂ O ₅ , ZnS—SiO ₂ is used, and is formed by a sputtering method, a vacuum evaporation method, or the like. A layer made of diamond-like carbon or SiO ₂ is formed as a lubricating underlayer 15 on the dielectric layer 14 by a sputtering method or the like. A layer made of a perfluoropolyether derivative or a fluorine-based polymer and a compatible material thereof is formed as a lubricating layer 16 on the lubricating base layer 15 by a dip method or a spin coating method.

[0040]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to only these Examples.

Example 1 A near-field magneto-optical recording medium having a structure as shown in FIG. 1 was manufactured. That is, a reflecting layer 12 made of Al _0.97 Cr _0.03 and having a thickness of 50 nm made of Al _0.97 Cr _0.03 by a DC sputtering method on a disc-shaped substrate 11 made of polycarbonate having a diameter of 130 mm and provided with a guide groove having a track pitch of 0.45 μm. A magneto-optical recording layer 13 made of Tb ₂₀ (Fe ₉₀ Co ₁₀ ) ₈₀ and having a thickness of 20 nm, on which Si is formed by reactive RF sputtering.
A 30 nm-thick dielectric layer 14 made of N was formed. Further, a 20 nm-thick lubricating underlayer 15 made of diamond-like carbon was formed thereon by a reactive RF sputtering method.

Thereafter, the medium was treated with a perfluoropolyether-based solvent (manufactured by Ausimont, trade name "Galden SV-7").
0 ") in dissolved, perfluoropolyether having a weight average molecular weight has a -CH ₂ OH in the molecular end across a 4000 (Ausimont, Ltd., trade name" Fomblin ZDO
L4000 ”) (0.01 vol.%) For 1 minute, and then the medium was pulled up to produce 10 magneto-optical recording media on which a lubricating layer 16 having a thickness of 1 nm was formed.

The contact angle of water on the surface of the magneto-optical recording medium obtained as described above was 80 °.

Next, these media were put into an environmental tester, and 8
It was charged for 1000 hours in an environment of 0 ° C. and 85% RH. Observation was made on ten media taken out, and no abnormality was observed on the film surface of any of the media.

Example 2 A lubricating underlayer was laminated in the same manner as in Example 1 and then a fluorine-based polymer solution (trade name “CYTOP CTX809A” manufactured by Asahi Glass Co., Ltd.) was spin-coated on the medium. Ten magneto-optical recording media on which a lubricating layer 16 having a thickness of 5 μm was formed were manufactured.

When the contact angle of water on the surface of the medium obtained as described above was measured, it was 120 °.

Next, this medium was put into an environmental tester,
It was charged for 1000 hours in an environment of 85% RH. Observation was made on ten media taken out, and no abnormality was observed on the film surface of any of the media.

COMPARATIVE EXAMPLE 1 Ten magneto-optical recording media were prepared by laminating up to the lubricating underlayer in the same manner as in Example 1, and the contact angle of water on the surface of the recording media was 50 °. .

Next, this medium was put into an environmental tester,
It was charged for 1000 hours in an environment of 85% RH. Observation was made on 10 sheets of the medium taken out, and in each case, a corroded portion was observed on the film surface.

COMPARATIVE EXAMPLE 2 A lubricating underlayer was laminated in the same manner as in Example 1, and then this medium was replaced with a perfluoropolyether-based solvent (Garden S, manufactured by Ausimont, Inc.).
V-70 ") having a weight average molecular weight of 4000
A solution (0.004 vol.%) Of a perfluoropolyether (trade name “Fomblin ZDOL4000” manufactured by Ausimont, Inc.) having —CH ₂ OH at both molecular ends.
The magnetic recording medium 10 in which a lubricating layer 16 having a thickness of 0.3 nm is formed by dipping the medium for 1 minute
Sheets were manufactured.

The contact angle of water on the surface of the magneto-optical recording medium obtained as described above was 65 °.

Next, the medium was put into an environmental tester,
It was charged for 1000 hours in an environment of 85% RH. Observation of 10 media taken out revealed that 8 of them had corroded portions on the film surface.

[0053]

According to the present invention, it is possible to obtain an optical recording medium suitable for a surface optical recording medium and a near-field optical recording medium, in which the recording film hardly deteriorates.

[Brief description of the drawings]

FIG. 1 is a diagram showing a partial cross section of an example of an optical recording medium of the present invention.

[Explanation of symbols]

 11: substrate 12: reflective layer 13: optical recording layer 14: dielectric layer 15: lubricating underlayer 16: lubricating layer

Claims (4)

[Claims] 1. An optical recording medium having at least a reflective layer, an optical recording layer and a lubricating layer formed on a substrate in this order, wherein the contact angle of water on the surface of the lubricating layer is 70 ° or more. . 2. The lubricating layer according to claim 1, wherein the lubricating layer is a layer composed of a perfluoropolyether derivative or a fluoropolymer having at least one fluorine atom in a monomer structure, and a compatible material thereof. Optical recording medium. 3. The optical recording medium according to claim 1, wherein the recording method is a surface optical recording method. 4. The optical recording medium according to claim 1, wherein the recording method is a near-field optical recording method.