JPH0827990B2 - 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 perpendicular to the film surface and that the Kerr effect 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 irradiated, the temperature rises and approaches the holding force Hc when approaching the Curie point and further exceeding the Curie point. Then, when the laser beam is turned off and returned to room temperature, the magnetization is reversed by making 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. However, the signal “1” is recorded. In addition, since the initial state of recording is "0", "0" remains as it is 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.

Third, a magnetically and mechanically uniform film can be obtained over a relatively large 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. It will be oxidized, making it impossible to record or reproduce information.

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.

Moreover, even a room temperature curable coating-supporting coating layer does not have sufficient moisture resistance, and is affected by moisture and oxygen permeation 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), among which a cured coating film containing an oligoester acrylate and methylbenzoyl formate (Vicure 55 manufactured by Stofer Japan) as a photosensitizer is disclosed. However, these are still insufficient in terms of protective layer function and curability.

Specifically, there are problems such as low curing rate, insufficient strength of the cured film when formed into a thin film, and necessity of increasing the film thickness. These problems are 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 with each other via an adhesive layer.

As an adhesive used in these cases, an epoxy adhesive or a solvent-based adhesive has been used, but an epoxy adhesive has a problem that the curing time is long and the initiator attacks the recording layer. The solvent-type adhesive has a problem of attacking a resin substrate.

For this reason, it has been proposed to use a hot-melt type adhesive as an adhesive that has a short curing time and does not attack the medium constituent materials (Japanese Patent Laid-Open Nos. 58-6536 and 58-1080).
No. 44, etc.).

However, although the above problems can be solved by using a hot-melt type adhesive, the above-mentioned substrate having the organic protective coating layer is bonded onto the recording layer using the above-mentioned hot-melt type adhesive. In this case, during storage under conditions of high temperature / high humidity or changes in temperature / humidity, peeling or the like occurs between the adhesive layer and the organic protective coat layer, and there is a problem in terms of durability.

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 the optical recording medium that is integrated with the adhesive layer inside so that there is no 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. Another object of the present invention is to provide an optical recording medium having excellent durability and moisture resistance.

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, a recording layer on at least one of the substrates, and an organic protective coating layer on the recording layer. The organic protective coating layer is formed by radiation-curing a coating film containing a radiation-curable compound and a photopolymerization initiator, and the adhesive layer is a hot-melt adhesive agent. The hardness of the organic protective coating layer and the adhesive layer is H ~ 3H and 3B in pencil hardness (JISK-5400) at 25 ° C, respectively.
To HB, and the photopolymerization initiator is an optical recording medium 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, a recording layer on at least one of the substrates, and an organic protective coating layer on the recording layer. To be integrated via an adhesive layer.

The organic protective coat layer is a radiation-cured coating film containing a radiation-curable compound and a photopolymerization sensitizer,
The adhesive layer is formed of a hot melt type adhesive.

And, the hardness of the organic protective coat layer and the adhesive layer,
Each pencil hardness (JISK-5400) at 25 ℃ is H-3H.
And 3B to HB.

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.

More specifically, if the hardness of the organic protective coating layer is softer than H, the durability becomes insufficient, and if it becomes harder than 3H, the coating film becomes brittle and the film forming ability deteriorates. The adhesive strength is reduced.

Further, if the hardness of the adhesive layer is softer than 3B, the durability is insufficient, and if it is harder than HB, the relaxation force of the distortion of the disk such as the warp of the substrate decreases.

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

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

The oligoester acrylate is an oligoester compound having a plurality of acrylate groups or methacrylate groups. The preferred oligosteric 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 Kagaku Co.) 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 group or methacrylate group, M: dihydric alcohol (for example, ethylene glycol, diethylene glycol, 1,6-hexane glycol, bisphenol A, etc.) residue, N: Residue of dibasic acid (for example, phthalic acid, isophthalic acid, adipic acid, succinic acid, etc.), n: 1 to 10, preferably 2 to 5 Of these, the one represented by (A) is preferable.

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.

Other radiation-curable compounds may be used in combination with the above oligoester acrylates. Examples of such compounds include acrylic acid and methacrylic acid having an unsaturated double bond that is sensitive to ionization energy and exhibits razyl 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 Phenol ethylene oxide adduct, although functional groups such as COOH were introduced into the product (Meth) acrylate, 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 = CHCO (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,
Examples thereof include polyvinyl alcohol resin, epoxy resin, phenoxy resin, and fibrin derivative.

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 the moisture-proof effect 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 one with a polyfunctional oligoester acrylate, the hardness described above can be easily obtained and the physical properties of the film can be improved.

Then, 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 sensitizer, the following known compounds may 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 optical recording medium of the present invention is formed of a hot melt type adhesive as described above.

Examples of the hot-melt adhesive used in the present invention include polyolefin resins such as polyethylene, polypropylene, polystyrene, and copolymers containing these, and the like, or a mixture of two or more thereof. It may be one to which a polyolefin, a polyolefin-based copolymer, a synthetic rubber or the like is added.

Then, for these 100 parts by weight, tackifier 100 ~
It is preferable to add 600 parts by weight, a softening agent of 0 to 100 parts by weight, and the like.

The softening temperature (according to the R and B method) of such a hot-melt adhesive is 150 ° C or lower, particularly 100 to 145 ° C, and the melt viscosity at 160 ° C is 1000 ps or less in the adhesive work and the recording layer. It is preferable in terms of influence on the substrate and the substrate.

Examples of the tackifier include various natural resins, modified products thereof, various synthetic resins and the like, and various known softening agents are used as the softening agent.

Such an adhesive may include an ultraviolet protection material, if necessary.
A filler and an antiaging agent may be contained.

The layer thickness of the adhesive layer formed from such a hot melt adhesive is preferably 10 to 50 μm, and particularly preferably 10 to 30 μm.

If the layer thickness is less than 10 μm, the adhesive strength will be insufficient, and 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 depth of the groove is about λ / 8n, particularly λ / 6n to λ / 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.

This calibration improves the write sensitivity and the read C / N ratio, and increases the tracking control signal.

Further, other shapes of the substrate may be tapes, drums, and the like.

 Examples of the 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 and the like 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), 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, 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 , Z
Various derivative substances such as nS, 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% silicon oxide, BaO, CaO, SrO, MgO, ZnO,
Those containing 50 wt% or less of a divalent metal oxide such as PbO and / or 10 wt% or less of an alkali metal oxide, and boron oxide and / or aluminum oxide.

(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 at 800 nm of 1.8-3.
0 is preferable, Si and rare earth metal and / or Al
Those containing and and 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 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 Various thermoplastic resins such as vinylidene chloride, polycarbonate, polyacetal, fluororesin, phenol resin, urea resin, unsaturated polyester resin, polyurethane, alkyd resin, melamine resin, epoxy resin, silicon resin, etc. can be used. Is.

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, a recording layer on at least one substrate, and an organic protective coat layer on the recording layer. The substrate is integrated with an adhesive layer formed of a hot-melt type adhesive so that the recording layer faces inside.

The organic protective coat layer is a radiation-cured coating containing a radiation-curable compound, and the hardness of the organic protective coat layer is greater than the hardness of the adhesive layer. Therefore, even when stored under conditions of high temperature, high humidity, or changes in temperature and humidity, there is no peeling between the organic protective coating layer and the adhesive layer, no change in characteristics or 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 A glass (SiO ₂ 48 wt%, Al ₂ O ₃ 15 wt%, B ₂ O ₃ 14 wt%, Na ₂ 13 cm, 1.2 mm thick bisphenol A-based polycarbonate resin (molecular weight 15000) was placed on a substrate. ₂ O 3
wt%, K ₂ O 2wt%, BaO 5wt%, CaO 9wt%, MgO 4wt%) film thickness 900 by high frequency magnetron sputtering
Layered in Å.

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, trimethylpropane acrylate 70% by weight, trade name Aronix M-80
30; manufactured by Toagosei Co., Ltd.] 100 parts by weight Photopolymerization sensitizer (the compound A: trade name IRGACURE907; manufactured by Ciba-Geigy Co., Ltd.) 5 parts by weight After applying such a coating composition, 120 w / cm of ultraviolet light is applied to 1
It was irradiated for 5 seconds and crosslinked and cured to obtain a cured film.

 The film thickness at this time was 5 μm.

A polypropylene hot-melt adhesive XW-13 (manufactured by Toagosei) (melt viscosity 250 ps at 160 ° C) was applied on this organic protective coat layer by a roll coater, and the same material as the above-mentioned substrate I stuck a protective plate of the size.

The thickness of the adhesive layer thus formed was 30 μm.

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

Aronix M of 100 parts by weight of multifunctional oligoester acrylate used for the organic protective coating layer of sample No. 1
Sample No. 2 was prepared in the same manner as Sample No. 1 except that -8030 was replaced with 50 parts by weight of Aronix M-400 (monofunctional or higher functional monomer) and 50 parts by weight of Aronix M-309 (trifunctional monomer). .

In addition, 100 parts by weight of sample No. 1 Aronix M-8
50 parts by weight of 030 was replaced with Aronix M-111 (monofunctional monomer), and a synthetic rubber hot melt adhesive HM-1275 (manufactured by HB Fuller Japan Co., Ltd.) was applied as an adhesive layer with a roll coater to a thickness of 30 μm. Sample No. 3 was prepared in the same manner as Sample No. 1 except for the above.

In addition, sample No. 1 Aronix M-8030 (100
50 parts by weight of Aronix M-6100 (bifunctional oligoester acrylate) and the above Aronix M-11.
Sample No. 4 was prepared in the same manner as Sample No. 1 except that the amount was changed to 50 parts by weight.

Furthermore, a one-pack type epoxy resin type Araldite AT-1 (manufactured by Ciba-Geigy Co., Ltd.) was applied as an adhesive layer by spinner coating to a layer thickness of 30 μm.
Sample No. 5 was prepared in the same manner as No. 1.

In addition, Sample No. 6 was prepared in the same manner as Sample No. 1 except that the adhesive layer was formed of HM-1275.

Furthermore, Sample No. 7 was prepared in the same manner as Sample No. 1 except that the photopolymerization sensitizer was changed to 5 parts by weight of BIQURE-55 (manufactured by Stofer Japan).

 The following tests were performed on these samples.

Durability test The characteristics (C / N ratio and bit error rate) and appearance change of the medium were observed after storage under conditions of high temperature and high humidity (80 ° C, 80% RH).

 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. The pencil hardness of the organic protective coat layer of Sample No. 7 was HB at the inner peripheral portion and H at the outer peripheral portion.

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

In addition, such an effect is caused by a so-called phase transition type Te-G.
The same was realized with recording layers such as e, TeO _x , and Te-Se.

Claims (2)

[Claims] 1. A pair of substrates, a recording layer on at least one of the substrates, and an organic protective coating layer on the recording layer, the pair of substrates having the recording layer inside. Is integrated via an adhesive layer, the organic protective coating layer is a radiation-cured coating film containing a radiation-curable compound and a photopolymerization initiator, and the adhesive layer is a hot-melt adhesive agent. The hardness of the organic protective coating layer and the adhesive layer is H ~ 3H and 3B ~ in pencil hardness (JISK-5400) at 25 ° C, respectively.
An optical recording medium, which is HB, wherein 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 optical recording medium according to claim 1, wherein the radiation-curable compound contains an oligoester acrylate.