JPH0827989B2 - Optical recording medium - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium such as a magneto-optical recording medium that records and reproduces information using heat and light such as laser light.

2. Related Art and Problems There is a magneto-optical memory medium as one of optical recording media.

Materials such as MnBi, MnAlGe, MnSb, MnCuBi, GdFe, TbFe, GdCo, PtCo, TbCo, TbFeCo, GdFeCo, TbFeO ₃ , GdIG, GdTbFe, GdTbFeCoBi, and CoFe ₂ O ₄ are known as recording media for magneto-optical memory. ing. These are formed as thin films on a transparent substrate such as plastic or glass by a method such as a vacuum evaporation method or a sputtering method. The characteristics common to these magneto-optical recording media are that the easy axis of magnetization is in the direction perpendicular to the film surface and that Kerr hardening and the Faraday effect are large.

As a recording method of a magneto-optical recording medium utilizing this property, there is, for example, the following method.

First, the entire film is "0", that is, uniformly magnetized (this is called erasure). Next, a laser beam is applied to the portion where "1" is to be recorded. When the laser beam is emitted, the temperature rises, and when the Curie point is approached and when the Curie point is exceeded, the holding power is maintained.
Approach Hc. Then, when the laser beam is turned off and returned to room temperature, the magnetization is reversed by the energy of the demagnetizing field, and when the laser beam is irradiated, an external magnetic field is applied in the direction opposite to the initial direction to return to room temperature. It is inverted and the signal "1" is recorded.

In addition, since the initial state of recording is "0", "0" remains in the portion not irradiated with the laser beam.

Similarly, the reading of the recorded magneto-optical memory is performed by using a laser beam and rotating the polarization plane of the reflected light depending on the direction of magnetization of the laser beam irradiation light, that is, the magneto-optical effect.

The first requirement for such a medium is that the Curie point is about 100 to 200 ° C and the compensation point is near room temperature.

Second, there are relatively few defects such as grain boundaries that cause noise.

Thirdly, it is possible to obtain a magnetically and mechanically uniform film over a comparatively large platform area without using a method such as high temperature film formation or long time film formation.

In response to such demands, in recent years among the above materials,
Amorphous perpendicular magnetic thin films of rare earth-transition metals have received a lot of attention.

However, when the magneto-optical recording medium made of such a rare earth-transition metal amorphous thin film is stored in contact with the atmosphere, the rare earth is selectively corroded or corroded by oxygen or water in the atmosphere penetrating through the substrate. You will not be able to record and play back information because you will be participating.

Therefore, in general, much research has been conducted on a structure having a protective layer between the magnetic thin film layer and the substrate and / or on the magnetic thin film layer.

Conventionally, as such a moisture-proof protective layer, there has been disclosed an attempt to provide an inorganic vacuum vapor deposition film of silicon monoxide, silicon dioxide or the like (JP-A-58-80142). Of these protective layers, an inorganic protective layer such as SiO is formed by a sputtering method, a vapor deposition method, or the like.

However, according to these methods, it is difficult to form a uniform, dense, and uniformly coated film, and a protective layer having sufficient moisture resistance cannot be obtained. Therefore, deterioration over time of the magnetic thin film layer of the magneto-optical recording medium is not improved.

Even a coating protective layer of a room temperature curable resin does not have sufficient moisture resistance, and is affected by permeation of moisture and oxygen during storage, which promotes deterioration.

In addition, an organic protective coating layer has been proposed in which a coating film of a radiation-curable compound is cured by ultraviolet rays or the like (Japanese Patent Laid-Open No. S60-12065).
61-133067), in which a coating film containing an oligoester acrylate, methyl benzoyl as a photosensitizer, and formate (Vicure 55 manufactured by Stofer Japan) is cured.

However, these are still insufficient in terms of protective layer function and curability.

Specifically, there are problems such as low curing speed, insufficient strength of the cured film when formed into a thin film, and necessity of increasing the film thickness. This is mainly due to insufficient photoabsorption of the photopolymerization initiator or the photosensitizer and the difficulty of radical cleavage.

Further, if the curing is not sufficient, the crosslinking density becomes low, and the uncured monomer or oligomer penetrates into the recording layer and adversely affects the recording layer. Such a phenomenon becomes noticeable especially when stored at high temperature and high humidity.

Therefore, it cannot be said that the optical recording medium using such a cured film has sufficient reliability.

By the way, in an optical recording medium, normally, a protective plate in the case of a single-sided recording type and a substrate in the case of a double-sided recording type are integrated via an adhesive layer.

As the adhesive used in these cases, a hot melt adhesive or a thermosetting adhesive is generally used.

However, the hot-melt adhesive has a bad influence on the recording layer and the substrate because it becomes a high temperature of 100 ° C. or more at the time of adhesion.
There are drawbacks such as warping of the medium after adhesion.

Further, the thermosetting adhesive also requires a high temperature of 100 ° C. or higher for quick adhesion, and has the same drawbacks as the above hot-melt adhesive.

In order to eliminate such a defect, a transparent portion having no recording layer is provided on the inner and outer peripheral portions of the substrate, and such a substrate has an adhesive having both a UV curing function and an anaerobic curing function. There has been proposed an information recording disk which is constructed by joining with each other (Japanese Patent Laid-Open No. 61-217944).

This is because the substrates are superposed on each other, and the inner and outer peripheral parts are first irradiated with ultraviolet rays to bond them, and then left to stand naturally to anaerobically cure to bond the remaining parts to each other. No heat is applied to the substrates, and no displacement occurs between the substrates during anaerobic curing.

However, when the substrates are bonded to each other with such an adhesive, when the organic protective coat layer as described above is formed on the recording layer, that is, when the adhesive layer and the organic protective coat layer are in contact with each other. When the medium after adhesion is stored under conditions of high temperature and high humidity or changes in temperature and humidity, peeling occurs between the adhesive layer and the organic protective coating layer, and a medium with high durability cannot be obtained. .

Incidentally, such a problem also applies to an optical recording medium having a so-called phase transition type recording layer.

II Object of the Invention An object of the present invention is to have a pair of substrates, a recording layer on at least one of the substrates, and an organic protective coating layer on the recording layer. In an optical recording medium that is integrated via an adhesive layer so that it is on the inside, there is no adverse effect on the medium due to heat when bonding both substrates, the bonding is quick and there is no gap between the substrates during bonding. Provided is an optical recording medium which is excellent in durability and moisture resistance without warping of the substrate and without peeling between the organic protective coating layer and the adhesive layer even when stored under conditions of high temperature / high humidity or changes in temperature / humidity. Especially.

III DISCLOSURE OF THE INVENTION Such an object is achieved by the present invention described below.

That is, the present invention has a pair of substrates, has a recording layer on at least one of the substrates except the inner peripheral portion and the outer peripheral portion of the substrate, and has an organic protective coating layer on the recording layer. In an optical recording medium in which the substrate is integrated with an adhesive layer so that the recording layer is on the inside, the organic protective coating layer is coated with a radiation-curable compound and a photopolymerization initiator. It is a cured product, and the adhesive layer is a film obtained by radiation-curing and anaerobically curing a coating film of an adhesive containing a compound having an acrylic or methacrylic group, and the hardness of the organic protective coating layer is the same as that of the adhesive layer. An optical recording medium having a hardness higher than that of the photopolymerization initiator and containing a compound represented by the following general formula (I).

General formula (I) {In the above general formula (I), R represents an alkyl group,
L represents an alkylene group and Y represents a heterocyclic group. } IV Specific Structure of the Invention Hereinafter, the specific structure of the present invention will be described in detail.

The optical recording medium of the present invention has a pair of substrates, has a recording layer on at least one of the substrates except the inner peripheral portion and the outer peripheral portion of the substrate, and has an organic protective coating layer on the recording layer. ,
The pair of substrates are integrally formed with the recording layer on the inner side through an adhesive layer.

The organic protective coating layer is a radiation-cured coating containing a radiation-curable compound, and the adhesive layer is a radiation-cured and anaerobic-cured coating of an adhesive containing a compound having an acrylic or methacrylic group. It was done.

The hardness of the organic protective coat layer is higher than the hardness of the adhesive layer.

With this structure, the organic protective coat layer and the adhesive layer are not separated even when stored under high temperature / high humidity or temperature / humidity change conditions.

The hardness of such an organic protective coating layer is preferably about H to 3H in pencil hardness (JIS K-5400) at 25 ° C.
When it is softer than H, the durability is insufficient, and when it is harder than 3H, the coating film becomes brittle and the film forming ability is deteriorated, and also the adhesive force to the sputtered film such as the substrate and the recording layer is deteriorated.

The hardness of the adhesive layer is preferably about 2B to H in terms of pencil hardness. If it is softer than 2B, the durability is insufficient, and if it is harder than H, the ability to relax the distortion of the disk such as the warp of the substrate decreases.

The hardnesses of the organic protective coat layer and the adhesive layer are in the above-described relationship within such a range.

When the organic protective coating layer and the adhesive layer are applied by, for example, spin coating, they may have a film thickness difference between the inner peripheral portion and the outer peripheral portion, and this difference in film thickness may cause difference in hardness. is there. Even in such a case, the present invention requires that both layers have the above hardness in the entire region.

The radiation-curable compound used for forming such an organic protective coat layer preferably contains an oligoester acrylate.

The oligoester acrylate is an oligoester compound having a plurality of acrylate groups or methacrylate groups. The preferred oligoester acrylates include those having a molecular weight of 1,000 to 10,000, preferably 2,000 to 7,000, and a degree of polymerization of 2 to 10, preferably 3 to 5. Further, among these, polyfunctional oligoester acrylates having 2 to 6, and preferably 3 to 6 acrylate groups or methacrylate groups are preferable.

As a polyfunctional oligoester acrylate, Aronix M-7100, M-5400, M-5500, M-5700, M-62
Commercially available products such as 50, M-6500, M-8030, M-8060, M-8100 (manufactured by Toagosei Co., Ltd.) can be used, and these are represented by the following formulas (A) and (B). It is what is done.

(B) A-M-N n -M-A A: acrylate or methacrylate groups, M: 2 dihydric alcohols (such as ethylene glycol, diethylene glycol, 1,6-hexane glycol, bisphenol A, etc.) residues, N: Dibasic acid (eg, terephthalic acid, isophthalic acid, adipic acid, succinic acid, etc.) residue, n: 1 to 10, preferably 2 to 5 Of these, those represented by (A) are preferred.

Such oligoester acrylate may be used alone.

Also, other radiation-curable compounds may be used in combination. In such a case, the oligoester acrylate is preferably present in the radiation curable compound in an amount of 20 wt% or more.

The above-mentioned oligoester acrylate may be used in combination with other radiation-curable compounds, such as acrylic acid or methacrylic acid having an unsaturated double bond which is sensitive to ionization energy and exhibits radical polymerizability. Radical crosslinkable or polymerizable groups such as acids or acrylic double bonds such as ester compounds thereof, allylic double bonds such as diallyl phthalate, unsaturated double bonds such as maleic acid and maleic acid derivatives, etc. Examples thereof include monomers, oligomers and polymers containing or introduced in the molecule. It is preferable that these are polyfunctional, especially trifunctional or more.

A compound having a molecular weight of less than 2000 is used as the radiation-curable monomer, and a compound having a molecular weight of 2000 to 10,000 is used as the oligomer.

These include styrene, ethyl acrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol methacrylate, 1,6-hexane glycol diacrylate, 1,6-hexane glycol dimethacrylate, etc., but particularly preferred ones Examples include pentaerythritol tetraacrylate (methacrylate), pentaerythritol acrylate (methacrylate), trimethylolpropane triacrylate (methacrylate), trimethylolpropane diacrylate (methacrylate), acrylic modified urethane elastomer (Nipporan 4040), or these Products with functional groups such as COOH introduced, phenol ethylene oxide adducts Acrylate (methacrylate), pentaerythritol fused ring acrylic group (methacryl group) represented by the following general formula or ε- caprolactone - compound with a acryl group, 1) (CH ₂ = CHCOOCH ₂ ) ₃ -CCH ₂ OH (special acrylate A) 2) (CH ₂ = CHCOOCH ₂ ) ₃ -CCH ₂ OH ₃ (special acrylate B) 3) [CH ₂ = CHOC (OC ₃ H ₆ ) _n -OCH ₂ ] _3- CCH ₂ CH ₃ (special acrylate C) In the formula, a compound of m = 1, a = 2, b = 4 (hereinafter referred to as a special pentaerythritol condensate A), a compound of m = 1, a = 3, b = 3 (hereinafter referred to as a special pentaerythritol condensate B) , M = 1, a = 6, b = 0 compound (hereinafter referred to as special pentaerythritol condensate C), m = 2, a = 6, b = 0 compound (hereinafter referred to as special pentaerythritol condensate D) ,) And special acrylates represented by the following general formula.

_{8) CH 2 = CHCOO- (CH} 2 CH 2 O) 4 -COCH = CH 2 ( special acrylate H) Further, as the radiation-curable oligomer, acrylic modified urethane elastomer, or these
Examples thereof include those into which a functional group such as COOH has been introduced.

Further, in addition to or instead of the above compounds, a radiation curable compound obtained by subjecting a thermoplastic resin to radiation-sensitive modification may be used.

Specific examples of such a radiation curable resin include acrylic acid having an unsaturated double bond exhibiting radical polymerizability,
Groups that crosslink or polymerize upon irradiation, such as acrylic double bonds such as methacrylic acid or their ester compounds, allyl double bonds such as diallyl phthalate, and unsaturated bonds such as maleic acid and maleic acid derivatives. Is contained or introduced in the molecule of the thermoplastic resin.

Examples of thermoplastic resins that can be modified into radiation-curable resins include vinyl chloride copolymers, saturated polyester resins, polyvinyl alcohol resins, epoxy resins, phenoxy resins, fibrin derivatives and the like.

Other resins that can be used for radiation-sensitive modification include polyfunctional polyester resins, polyetherester resins, polyvinylpyrrolidone resins and derivatives (PVP
Olefin copolymers), polyamide resins, polyimide resins, phenol resins, spiro acetal resins, acrylic resins containing at least one hydroxyl group-containing acrylic ester and methacrylic ester as a polymerization component are also effective.

The film thickness of the organic protective coating layer of such a radiation-curable compound is 0.1 to 30 μm, more preferably 1 to 10 μm.

If this film thickness is less than 0.1 μm, a uniform film cannot be formed, and moisture-proof curing in an atmosphere with high humidity is insufficient,
The durability of the recording layer is not improved. If it exceeds 30 μm, warpage of the recording medium or cracks in the protective film may occur due to shrinkage during curing of the resin film, which is not practical.

Such a coating film may be usually formed by combining various known methods such as spinner coating, gravure coating, spray coating and dipping. The layer forming conditions of the coating film at this time may be appropriately determined in consideration of the viscosity of the mixture of the coating film composition, the target coating film thickness, and the like.

In the present invention, the radiation applied to the coating film is preferably ultraviolet light.

When ultraviolet rays are used, a photopolymerization sensitizer is added to the above radiation-curable compounds.

The photopolymerization initiator used in the present invention (also referred to as "photopolymerization sensitizer" as described later) is a compound represented by the following general formula (I).

By using this with a polyfunctional oligoester acrylate, the hardness described above can be easily obtained and the physical properties of the film can be improved. Further, peeling from the adhesive layer is reduced, and durability and moisture resistance are improved.

General formula (I) In the above general formula (I), R represents a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms, for example, a methyl group, an ethyl group, a propyl group, a butyl group or the like, and among them, a methyl group, an ethyl group or the like is preferable. .

L is a substituted or unsubstituted alkylene group having 1 to 3 carbon atoms, for example -CH ₂ -, Etc., among other things Is preferred.

Y is a heterocyclic group, for example, a morpholino group, a 2-morpholinyl group, a piperidino group, a 4-piperidinyl group, a 2-pyridyl group, a 2-quinolyl group, a 1-pyrrolidinyl group, 1-
It represents a pyrrolyl group, a 2-thienyl group, a 2-furyl group or the like, and among them, a morpholino group is preferable.

RS- may be bonded to the benzene ring at any substitutable position of the benzene ring in the general formula (I), Is preferably the p-position.

In the present invention, the most preferable compounds among the compounds represented by the general formula (I) are as follows.

This compound A is commercially available as IRGACURE907 (manufactured by Japan Ciba Geigy).

The compound represented by formula (I) acts as a photopolymerization initiator or a photopolymerization sensitizer during radiation curing.

The content of such a compound in the organic protective coating layer is 0.1 to 20 wt%, preferably 1 to 10 wt%.

This is because if it is less than 0.1 wt%, the action as a photopolymerization initiator or photosensitizer is insufficient, and if it exceeds 20 wt%, the remaining photopolymerization initiator or photopolymerization sensitizer penetrates into the recording layer, This is because it adversely affects the recording layer.

Further, as the photopolymerization initiator, the following known compounds can be used in combination with the compound represented by the general formula (I), if necessary.

For example, benzoin methyl ether, benzoin ethyl ether, α-methylbenzoin, α-chlordeoxybenzoin and other benzoin compounds, benzophenone, acetophenone, bisdialkylaminobenzophenone and other ketones, acetolaquinone, phenanthraquinone and other quinones, benzyl disulfide. And sulfides such as tetramethylthiuram monosulfide.

Then, in order to cure the coating film containing such a photopolymerization sensitizer and the radiation-curable compound by ultraviolet rays, various known methods may be used.

For example, a UV bulb such as a xenon discharge tube or a hydrogen discharge tube may be used.

 An electron beam can also be used depending on the case.

 Next, the adhesive layer will be described.

The adhesive layer of the present invention is, as described above, a radiation-cured and anaerobically-cured coating of an adhesive containing a compound having an acrylic or methacrylic group.

The compound having a (meth) acrylic group is preferably oligoester acrylate.

As the oligoester acrylate, the same ones as described above in the explanation of the organic protective coat layer are preferable.

The oligoester acrylate may be used alone or in combination with another radiation-curable compound having a (meth) acrylic group or a radiation-curable compound having no acrylic group. When used in combination with another radiation-curable compound, the oligoester acrylate is preferably present in the radiation-curable compound in an amount of 50 wt% or more, preferably 70 wt% or more.

As the other radiation-curable compound, the same compounds as those described above in the description of the organic protective coat layer can be used.

However, the above-mentioned monomer is likely to remain uncured, and this may adversely affect the recording layer and the like. Therefore, it is preferable that the addition amount be as small as possible.

Examples of the radiation used for curing such a radiation-curable compound include ultraviolet rays and electron beams, but it is preferable to use ultraviolet rays.

As the ultraviolet light source, for example, an ultraviolet light bulb such as a xenon discharge tube or a hydrogen discharge tube may be used.

When ultraviolet rays are used, a photopolymerization sensitizer is usually added to the adhesive. As the photopolymerization sensitizer, the compounds described above in the explanation of the organic protective coat layer are preferable.

The adhesive preferably contains a component containing an oxidizing agent and a component containing a reducing agent in addition to the above-mentioned radiation-curable compound and photopolymerization sensitizer, and these reactions generate an initiating species. It is preferable that the compound having the (meth) acrylic group is anaerobically cured.

The adhesive used in the present invention is usually a so-called two-component type anaerobic curable adhesive, that is, a component containing an oxidizing agent and a component containing a reducing agent are separated, and at least one of these ( A compound containing a (meth) acryl group is preferably used, and these two components are mixed and used when the adhesive is applied.

Diacyl peroxide, dialkyl peroxide and the like are useful as the oxidizing agent to be used, and specific examples thereof include benzoyl peroxide and the like.

Further, as the reducing agent, a tertiary amine or a mercaptan compound is useful, and specific examples thereof include, for example,
Examples thereof include N, N-dimethylaniline.

The amount ratio of the oxidizing agent and the reducing agent to the radiation-curable compound is preferably about 0.1 to 10 mol% of the oxidizing agent and the reducing agent with respect to the radiation-curable compound.

If this value is less than 0.1 mol%, the redox reaction is less likely to occur and the initiation species are less likely to occur, and if it exceeds 10 mol%, the unreacted reagent may adversely affect the recording layer or the pot life may be shortened.

Such an adhesive may be formed by various known methods as described above in the description of the organic protective coat layer.

The thickness of the adhesive layer obtained by radiation-curing and anaerobically curing such an adhesive is preferably 5 to 50 μm. If the thickness is less than 5 μm, the adhesiveness will deteriorate,
If it exceeds 50 μm, the durability will decrease.

The substrate used in the optical recording medium of the present invention is formed of resin, various kinds of glass, or the like.

Preferred resins include acrylic resins, polycarbonate resins, epoxy resins, polymethylpentene resins and the like.

Since recording is performed through the substrate, the transmittance for writing light or reading light is 86% or more.

The substrate is usually disk-shaped and has a thickness of about 1.2 to 1.5 mm.

Grooves or pits for tracking may be formed on the recording layer forming surface of such a disc-shaped substrate.

The groove is added to about γ / 8n, particularly γ / 6n to γ / 12n (where n is the refractive index of the substrate). The width of the groove is about the track width.

Then, normally, it is preferable to irradiate the writing light and the reading light from the back surface side of the substrate with the recording layer located in the concave portion of the groove as a recording track portion.

With this configuration, the write sensitivity and the read C / N ratio are improved, and the tracking control signal is increased.

Further, the substrate may have another shape, such as a tape or a drum.

Examples of the recording layer used in the present invention include a magnetic thin film layer.

The magnetic thin film layer is one in which information is magnetically recorded by a modulated heat beam or a modulated magnetic field,
The recorded information is magnetic-optically converted and reproduced.

As a material of such a magnetic thin film layer, an alloy of a rare earth metal such as Gd and Tb and a transition metal such as Fe and Co is formed as an amorphous film by sputtering, vapor deposition, etc. Co is an essential component.

In this case, the total content of Fe and Co is preferably 65 to 85 at%.

And the balance is substantially rare earth metals, especially Gd and / or
Or Tb.

And, as a preferable example thereof, TbFeCo, GdFeCo, GdTb
FeCo etc.

In these magnetic thin film layers, C is contained in the range of 10 at% or less.
r, Al, Ti, Pt, Si, Mo, Mn, V, Ni, Cu, Zn, Ge, Au
Etc. may be contained.

In addition, as a rare earth element, Sc, Y, and
La, Ce, Pr, Nd, Pm, Sm, Eu, Dy, Ho, Er, Tm, Yb, Lu
Etc. may be contained.

The thickness of such a magnetic thin film layer is preferably 0.01 to 1 μm.

Other materials for the recording layer include so-called phase transition type materials such as Te-Se, Te-Se-Sn, Te-Ge, Te-In, Te-Sn, Te-Ge-Sb-S and Te. -Ge-As-Si, Te-Si, Te-Ge-Si-Sb, Te-Ge-Bi, Te-Ge-In-Ga, Te-Si-Bi-Tl, Te-Ge-Bi-In-S , Te-As-Ge-Sb, Te-Ge-Se-S, Te-Ge-Se, Te-As-Ge-Ga, Te-Ge-S-In, Se-Ge-Tl, Se-Te-As , Se-Ge-Tl-Sb, Se-Ge-Bi, Se-S (above, Japanese Patent Publication No. 54-41902, Japanese Patent No. 1004835, etc.) TeO _x (Japanese Patent Laid-Open No. 58-54338, Japanese Patent No. 974257) Te
Te dispersed in oxide), TeO _x + PbO _x (patent No. 974258), TeO _x + VO _x (patent No. 974257), others, Te-Tl, Te
-Tl-Si, Se-Zn-Sb, Te-Se-Ga, TeN _{x and} other Te, Se-based chalcogen-based Ge-Sn, Si-Sn and other amorphous-crystalline transition alloy Ag There are alloys such as —Zn, Ag—Al—Cu, and Cu—Al that change color due to a change in crystal structure, and alloys such as In—Sb that cause a change in crystal grain size.

In the present invention, such a recording layer and a protective layer, an intermediate layer, etc., which are provided if necessary, are provided excluding the inner peripheral portion and the outer peripheral portion of the substrate. By providing the layers in this way, when the substrates are adhered to each other, the above-mentioned adhesive layer can be easily and reliably cured by radiation.

In the present invention, an intermediate layer may be provided between the substrate and the recording layer.

The material of the intermediate layer is a compound containing oxygen, carbon, nitrogen, sulfur, etc., for example, SiO ₂ , SiO, AlN, Al ₂ O ₃ , Si ₃ N ₄ ,
Various derivative substances such as ZnS, BN, TiO ₂ , TiN, etc. or mixtures thereof; glass, such as borosilicate glass, barium borosilicate glass, aluminum borosilicate glass, etc., or those containing Si ₃ N ₄ etc. You can use it. Above all, borosilicate glass with SiO ₂ 40-80 wt%,
Barium borosilicate glass, aluminum borosilicate glass, and those obtained by substituting a part of SiO ₂ with Si ₃ N ₄ or the like are preferable.

Among these, the following are particularly preferable.

(1) 40-60 wt% of silicon oxide, 50 wt% or less of divalent metal oxide such as BaO, CaO, SrO, MgO, ZnO, PbO and / or 10 wt% of alkali metal oxide, boron oxide and / or oxidation Those containing aluminum.

(2) Ba, Ca, Sr, M as Si and other metals or metalloid elements
at least one of g, Zn, Pb, etc., at least one of Al, B, and at least one of alkali metal elements,
The Si atomic ratio in all metals or semimetals is 0.3 to 0.9, O and N are further contained, and O / (O + N) is 0.4 to 0.8.

Such an intermediate layer is 500 ~ 3000 Å, preferably 800 ~
A thickness of 2500Å is recommended.

This is because if it is less than 500 Å, the weather resistance is not sufficient, and if it exceeds 1500 Å, the sensitivity is lowered when the medium is too thick.

As these intermediate layers, the above-mentioned glass layer is formed as an intermediate layer base on the order of 300 to 1000 Å, and a Si layer is formed on the glass layer.
_{O 2, SiO, Si 3 N} 4, AlN, Al 2 O 3, ZnS , etc., or a mixture thereof dielectric material as the dielectric layer 500 to 1,500
It is preferable to have a layer of about Å.

In this case, the dielectric layer has a refractive index of 1.8 to 3.0 at 800 nm.
Those containing Si and rare earth metals and / or Al, and those containing O and N are preferred.

A layer made of the same material as the intermediate layer may be provided as a protective intermediate layer between the recording layer and the protective layer. The thickness may be about the same.

The optical recording medium of the present invention is prepared by further using one set of substrates having the recording layer, the organic protective coating layer and the like as described above, facing each other with both recording layers facing inward, and pasted using the adhesive layer. Together, write from the back side of both boards,
A so-called double-sided recording type can be used.

The present invention can also be applied to a so-called single-sided recording type in which the recording layer is provided on only one substrate.

The resin material of the substrate on which the recording layer is not provided is not particularly required to have transparency, and various resins such as polyethylene, polyvinyl chloride, polystyrene, polypropylene, polyvinyl alcohol, methacrylic resin, polyamide, poly Vinylidene chloride, polycarbonate, polyacetal, various thermoplastic resins such as fluorine resin, phenol resin, urea resin, unsaturated polyester resin, polyurethane, alkyd resin, melamine resin, epoxy resin,
Various thermoplastic resins such as silicon resin can be used.

Various inorganic materials such as glass and ceramics may be used.

The shape and dimensions of this product are almost the same as those of the substrate provided with the recording layer.

Further, it is preferable to provide a hard coat layer as various protective films on the back surface (the surface on the side where the recording layer is not provided) of these substrates.

The material of the hard coat layer may be the same as the material of the organic protective coat layer described above.

V. Specific Action and Effect of the Invention The optical recording medium of the present invention has a pair of substrates, and has a recording layer on at least one of the substrates excluding the inner peripheral portion and the outer peripheral portion of the substrate. It has an organic protective coat layer,
The pair of substrates are integrated with each other with an adhesive layer so that the recording layer faces inside.

Since the adhesive layer is used for radiation-curing and anaerobic-curing a coating film of an adhesive having an acrylic or methacrylic group, when the two substrates are integrated, first, radiation such as ultraviolet rays is applied. The inner peripheral portion and the outer peripheral portion of the substrate can be adhered to each other, and then the remaining portions can be adhered by anaerobic curing. Therefore, heat is not applied to the medium at the time of adhesion, and the recording layer and the substrate are not adversely affected. Further, the warp of the substrate does not occur after the bonding. Furthermore, the bonding is quick and there is no gap between the substrates during bonding, and finally the entire surface of the substrate is firmly bonded.

Further, the organic protective coat layer is a coating film containing a radiation-curable compound that is radiation-cured, and the hardness of the organic protective coat layer is higher than the hardness of the adhesive layer. Therefore, even when stored under conditions of high temperature / high humidity or changes in temperature / humidity, there is no peeling between the organic protective coating layer and the adhesive layer and changes in characteristics / appearance, and optical recording with excellent durability and humidity resistance The medium is realized.

VI Specific Examples of the Invention Hereinafter, the present invention will be described in more detail by showing specific examples of the invention.

Example 1 Glass (SiO ₂ 48w%, Al ₂ O ₃ 15wt%, B ₂ O ₃ 14wt%, Na on a substrate made of bisphenol A-based polycarbonate resin (molecular weight 15000) having a diameter of 13cm and a thickness of 1.2mm. ₂ O
3wt%, K ₂ O 2wt%, BaO 5wt%, CaO 9wt%, MgO 4w
%) Intermediate layer was formed to a film thickness of 900 Å by high frequency magnetron sputtering.

21at% Tb, 68at% Fe, 7at% Co, 4at on this intermediate layer
A% Cr alloy thin film was sputtered to a thickness of 800Å to form a magnetic thin film layer. The magnetic thin film layer was formed except for the inner peripheral portion and the outer peripheral portion of the substrate. The target used was an Fe target on which Tb, Co, and Cr chips were placed.

On this magnetic thin film layer, a protective interlayer of glass (same as the case of the intermediate layer) is formed by sputtering to a film thickness of 1000Å, and the following radiation-curable compound and photopolymerization sensitizer are placed on this protective intermediate layer. The coating composition containing the same was applied by spinner coating as an organic protective coating layer.

(Coating composition) Polyfunctional oligoester acrylate [Oligoester acrylate (trifunctional or more) 30% by weight, trimethylpropaacrylate 70% by weight, trade name Aronix M-803
0; manufactured by Toagosei Co., Ltd.] 100 parts by weight Photopolymerization sensitizer (the compound A: trade name IRGACURE907; manufactured by Ciba-Geigy Co., Ltd. Japan) 5 parts by weight After applying such a coating composition, 120 w / cm of ultraviolet light is applied to 1
The film was cured by cross-linking and irradiating for 5 seconds to form a cured film. The film thickness at this time was 5 μm.

On this organic protective coat layer, a compound having an acrylic group and a photopolymerization sensitizer are contained, and in addition thereto, an equal amount of the following two kinds of adhesives containing an oxidizing agent and a reducing agent. After mixing, they were applied by spinner coating, and a protective plate of the same material and size as the above-mentioned substrate was stuck on this. Then, radiation curing and anaerobic curing were performed under the following conditions.

Adhesive (oligoester acrylate type) Arontite LA-7 Arontite LB-8 (both manufactured by Toa Gosei) Curing conditions Radiation curing: 120 W / cm UV irradiation for 15 seconds Anaerobic curing: leaving at room temperature for 10 minutes The thickness of the formed adhesive layer is 30 μm
Met.

A single-sided recording type optical recording medium was obtained as described above, and was designated as sample No. 1.

The polyfunctional oligoester acrylate used for the organic protective coating layer of Sample No. 1 was mixed with Aronix M-400 (6
Monofunctional or higher monomer) 50 parts by weight and Aronix M-309
Sample No. 2 was prepared in the same manner as Sample No. 1 except that it was mixed with 50 parts by weight of (trifunctional monomer).

In addition, polyfunctional oligoester acrylate, Aronix M-6100 (bifunctional oligoester acrylate)
50 parts by weight and Aronix M-111 (monofunctional monomer) 50
Replaced with parts by weight, and others in the same manner as sample No. 1,
Sample No. 3 was prepared.

Furthermore, one-pack type epoxy resin-based Araldite AT-
Samples except that 1 (manufactured by Ciba-Geigy Co., Ltd.) was applied as a spinner coat to a layer thickness of 5 μm to form an organic protective coat layer.
Sample No. 4 was prepared in the same manner as No. 1.

Furthermore, sample No. 1 oligoester acrylate was replaced with urethane acrylate (Aronix M-110
0) Sample No. 5 was prepared in the same manner as Sample No. 1 except for 100 parts by weight.

In sample No. 1, the photopolymerization sensitizer was BIQURE.
Sample No. 6 was prepared in the same manner as Sample No. 1 except that 5 parts by weight of -55 (made by Stouffer Japan) was used.

 The following tests were performed on these samples.

Storage test It was stored at high temperature and high humidity (80 ℃, 80% RH), and the characteristics of the medium (C / N ratio and bit error rate) and appearance change were observed.

 Table 1 shows the results.

The pencil hardness of the organic protective coat layer and the adhesive layer of each sample at 25 ° C. is shown in Table 1.
Further, the pencil hardness of the organic protective coat layer of Sample No. 6 is
The inner peripheral portion of the organic protective coat layer was HB, and the outer peripheral portion was H.

 From the above results, the effect of the present invention is clear.

Incidentally, such hardening is a so-called phase transition type Te-G.
The same was realized with recording layers such as e, TeO _x , and Te-Se.

Claims (4)

[Claims] 1. A pair of substrates, and a recording layer on at least one of the substrates except an inner peripheral portion and an outer peripheral portion of the substrate,
In an optical recording medium having an organic protective coating layer on this recording layer, and a pair of these substrates being integrated via an adhesive layer so that the recording layer is on the inside, the organic protective coating layer is A radiation-cured coating film containing a curable compound and a photopolymerization initiator, wherein the adhesive layer is a radiation- and anaerobic-cured coating film of an adhesive containing a compound having an acrylic or methacrylic group. Wherein the hardness of the organic protective coat layer is larger than the hardness of the adhesive layer, and the photopolymerization initiator contains a compound represented by the following general formula (I). General formula (I) {In the above general formula (I), R represents an alkyl group,
L represents an alkylene group and Y represents a heterocyclic group. ｝ 2. The light according to claim 1, wherein the hardness of the organic protective coat layer and the hardness of the adhesive layer are H to 3H and 2B to H in pencil hardness (JIS K-5400) at 25 ° C., respectively. recoding media. 3. A radiation-curable compound containing an oligoester acrylate according to claim 1 or 2.
An optical recording medium according to item. 4. An adhesive having an oxidant-containing component and a reducing agent-containing component, and an initiator is generated by these reactions to anaerobically cure a compound having an acrylic group or a methacrylic group. The optical recording medium according to any one of claims 1 to 3, wherein