JP2741531B2 - optical disk - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical disc, particularly a magneto-optical recording disc, a phase-change optical recording disc, a pit-forming optical recording disc, a read-only optical disc, and the like.

<Prior Art> Among optical discs, an optical recording disc, in particular, is formed by providing a recording layer as an information carrying portion on a substrate. When recording / reproducing, a laser beam or the like is usually irradiated from the substrate side. It is done by doing.

The substrate used for this purpose is made of a transparent material, for example, glass or resin.

In this case, a resin substrate is conventionally used as the substrate of the optical disk from the viewpoint of weight reduction of the disk and easiness of formation of groups and pits for tracking.

In order to prevent mechanical damage due to picking of the recording layer or the like, a protective substrate is provided on the recording layer side of the substrate, or a pair of substrates are integrated so that the recording layer is enclosed.

In the case where a pair of resin-made substrates or a substrate and a protective substrate are bonded as described above, U.S. Pat.No. 4,503,531 discloses that the softening point is 140 ° C. or less, and the normal tensile adhesive strength is 1 kg at 20 ° C.
It has been proposed to bond with a hot melt adhesive having a melt viscosity of not less than 1000 P / cm ² and a melt viscosity of 160 ° C. at 160 ° C.

Further, Japanese Patent Application No. 62-072888 proposes that a pair of substrates be integrated with a predetermined hot-melt adhesive.

<Problems to be Solved by the Invention> However, constituent layers made of another material such as glass and metal are usually provided in a multilayer structure on a substrate of an optical disk, particularly an optical recording disk.

Therefore, for example, when an optical disk is stored at a high temperature or a low temperature, warpage, stress, or distortion occurs in a substrate, a protective substrate, and constituent layers such as a recording layer, a protective coat, and an adhesive layer.

In particular, a single-sided recording type optical recording disk in which a resin substrate having a constituent layer such as a recording layer and a resin protection substrate are integrated has a higher coefficient of thermal expansion than a glass disk, and both substrates have Causes asymmetrical warpage and stress or strain.

Therefore, for example, under severe thermal conditions in which the temperature changes at −30 to −65 ° C. and 20 ° C./sec, the substrate and the substrate, the substrate and the protective substrate, or these and each of the constituent layers, and further the constituent layers and the constituent layers Will peel off.

The optical disc integrated by the adhesive used in the conventional optical disc as described above has insufficient reliability under severe thermal conditions.

An object of the present invention is to provide a substrate and a substrate, a substrate and a protective substrate, and each of these constituent layers such as a protective coat even when stored under severe thermal conditions in which the temperature changes at -30 to 65 ° C. and 20 ° C./sec. Further, the constituent layers are not separated from each other, so that a highly reliable disk can be provided.

<Means for Solving the Problems> Such an object is achieved by the present invention of the following (1) to (3).

(1) having a pair of substrates, forming an information carrying portion on at least one substrate, and enclosing the information carrying portion,
An optical disc in which the pair of substrates are integrated with an adhesive, wherein the pair of substrates are both made of resin or both made of glass, and the glass transition temperature Tg of the adhesive is −60 to 10 ° C. And
An optical disc having a Young's modulus of not more than 100 kgf / mm ² at -20 ° C and 10 Hz, and a mechanical loss coefficient tanδ of not less than 0.1 at -20 ° C and 10 Hz.

(2) The optical disc according to (1), wherein the information carrying unit is a recording layer.

(3) The above-mentioned (2), wherein the recording layer contains a rare earth metal element, and a resin protective coat is provided on the recording layer.
The optical disk as described in.

<Operation> In the optical disc of the present invention, a pair of glass or resin substrates having an information carrying portion such as a recording layer on at least one side has a predetermined glass transition temperature Tg, a Young's modulus and a mechanical loss coefficient tanδ. They are integrated by an adhesive.

For this reason, between the substrates caused by temperature changes and the like,
Alternatively, the adhesive layer absorbs or alleviates stress, strain, and the like between the constituent layers such as the protective coat and the like, and between the constituent layers.

Therefore, for example, even when stored under severe thermal conditions in which the temperature changes at −30 to 65 ° C. and 20 ° C./sec, the separation between the substrate and the substrate, these and each of the constituent layers, and the constituent layers and the constituent layers is not removed. It can be completely prevented, and high reliability can be obtained.

It should be noted that the information carrying unit in the present invention refers to both a unit that carries information in advance, as in a read-only disc, and a recording layer that can carry information, as in a record / playback disk.

<Specific Configuration> Hereinafter, a specific configuration of the present invention will be described in detail.

FIG. 1 shows a preferred embodiment of the optical disk of the present invention.
1 shows an example of a magneto-optical recording disk.

The magneto-optical recording disk 1 shown in FIG. 1 has a resin layer 3, a protective layer 4, an intermediate layer 5, a recording layer 6 as an information carrying portion, a protective layer 7, a protective coat 8, an adhesive layer on a substrate 2. 9. It has a protection substrate 10 in order.

In the present invention, the substrate 2 is transparent to recording light and reproduction light, and is made of resin or glass.

When the substrate 2 is made of glass, heat resistance and moisture resistance are improved, high rigidity is obtained, and birefringence hardly occurs.

If the substrate 2 is made of resin, the disk can be measured.

 The substrate 2 has a disk shape.

The diameter of the substrate 2 is usually about 50 to 360 mm, and its thickness is about 0.5 to 2 mm.

 When the substrate 2 is made of resin, rigid resin is used.

In this case, the resin to be used is not limited, but for example, a crispy resin, a polycarbonate, an epoxy resin, polymethylpentene, a polyolefin and the like are preferable.

 The substrate 2 may be manufactured according to a known method.

For example, in the case of a resin substrate, predetermined patterns such as pits or groups may be simultaneously formed on the substrate surface by injection molding or the like for tracking, addressing, and the like.

 In this case, the resin layer 3 is not provided.

When the substrate 2 is made of glass, the substrate 2 is preferably made of tempered glass. By using tempered glass,
Higher rigidity and better weather resistance and durability can be obtained.

The tempered glass includes a physically tempered glass and a chemically tempered glass according to the tempering method, and is used depending on the application.

There is no particular limitation on the tempered glass used in the present invention, and a glass tempered using a normal tempering method is used, but a chemically tempered glass is preferably used.

Chemically strengthened glass is compressed into glass by, for example, exchanging some alkali metal ions as glass constituent elements with other kinds of alkali metal ions supplied from outside, especially by exchanging Li and Na and Na and K. It is a glass in which a stress layer is formed and the mechanical strength is increased.

The chemical strengthening treatment is usually performed by heating and melting an alkali salt such as a nitrate or a sulfate, and immersing the glass to be treated in the molten liquid for several hours to several tens of hours.

Glass produced by such a chemical strengthening process,
Usually, it is a surface strengthened glass having a compression stress layer formed only near the glass surface. In this case, the thickness of the compressive stress layer is 10
It is preferably about 200 to 200 μm, particularly about 30 to 75 μm.

As the chemically strengthened glass to be used, soda, lime, silicate glass, etc., which has been subjected to the above-mentioned chemical strengthening treatment, may be used. It is preferable to use those that have been applied.

The alumina silicate glass preferably has an Al ₂ O ₃ content of 10 wt% or more because of its high mechanical strength. In particular, a glass containing 15 to 30 wt% of Al ₂ O ₃ is preferably used. preferable.

The composition range of the alumina silicate glass suitably used in the present invention is shown below.

_{SiO 3 50~60wt% Al 2 O 3} 15~30wt% B 2 O 3 1~10wt% R I 2 O 10~25wt% R II O 1~10wt% ( provided that, R ^I and R ^II are each monovalent And divalent metal) TiO ₂ etc. 0 to 5 wt% And the K ⁺ substitution rate is preferably about 0.01 to 1 mg / cm ³ .

When a glass substrate 2 is used, a resin layer 3 is preferably provided on the substrate 2.

The resin layer 3 has a predetermined pattern such as pits or grooves on its surface for tracking, addressing, and the like. Note that a predetermined pattern may be formed by chemical etching or the like without providing the resin layer 3.

The resin material constituting the resin layer 3 is not particularly limited, and may be appropriately selected from known resins used in a so-called 2P method. In the 2P method, a radiation-curable compound is generally used. In the present invention, for example, a monomer belonging to a polyfunctional ester acrylate, a polyfunctional urethane acrylate, a polyfunctional epoxy acrylate, or the like is mixed with two or three components, or these are mixed. A mixture obtained by mixing a polyester acrylate, an oligoester acrylate, a polyurethane acrylate, an oligourethane acrylate, or the like with a monomer and adding a photopolymerization initiator Irg-907, 651, or the like can be suitably used.

It is preferable to form such a resin layer 3 by a known 2P method.

In the 2P method, first, a radiation-curable compound is spread on the surface of a stamper having a predetermined pattern, and a glass substrate is pressed onto the radiation-curable compound layer. This pressing transfers the pattern on the stamper surface to the layer surface. Next, the resin is cured by irradiating radiation through the glass substrate, and the resin and the glass substrate are bonded to each other. Thereafter, the resin and the stamper are separated.

Through the above steps, the resin layer to which the pattern of the stamper has been transferred is formed on the surface of the glass substrate.

The thickness of the resin layer 3 thus formed is preferably 5 to 100 μm, and more preferably 10 to 30 μm.

The intermediate layer 5 is provided to improve the C / N ratio, and is preferably formed of various dielectric materials, and preferably has a thickness of about 30 to 150 nm. Further, it is preferable to use a vapor phase film forming method such as a sputtering method as a layering method.

Incidentally, such a material for the intermediate layer may be provided as a protective layer 7 on the recording layer 6 described later, and used together with the intermediate layer 5. When used together, the compositions of the intermediate layer 5 and the protective layer 7 may be the same or different.

The protective layer 4 and the protective layer 7 are provided for improving the corrosion resistance of the recording layer 6, and it is preferable that at least one of them, and preferably both of them are provided. These protective layers are preferably composed of an inorganic thin film made of various oxides, carbides, nitrides, sulfides or mixtures thereof. Further, as described above, it may be formed of the above-mentioned intermediate layer material. The thickness of the protective layer is preferably about 30 to 300 nm from the viewpoint of improving corrosion resistance.

Such a protective layer is preferably formed by various vapor deposition methods such as a sputtering method.

In the recording layer 6, information is magnetically recorded by a modulated heat beam or a modulated magnetic field, and the recorded information is reproduced by magneto-optical conversion.

The material of the recording layer 6 is not particularly limited as long as it can perform magneto-optical recording. An alloy containing a rare earth metal element, particularly an alloy of a rare earth metal and a transition metal, is formed by sputtering,
It is preferably formed as an amorphous film by an evaporation method or the like.

As the rare earth metal, it is preferable to use one or more of Tb, Dy, Nd, Gd, Sm, and Ce.

 Fe and Co are preferable as the transition metal.

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

 The balance is substantially a rare earth metal.

Preferred compositions of the recording layer include TbrFCo, Dy
There are TbFeCo, NdDyFeCo, NdGdFeCo and the like.

In the recording layer, Cr, Al, T
i, Pt, Si, Mo, Nn, V, Ni, Cu, Zn, Ge, Au and the like may be contained.

In addition, Sc, Y, La, Ce, Pr, P
Other rare earth metal elements such as m, Sm, Eu, Ho, Er, Tm, Yb, and Lu may be contained.

The layer thickness of such a recording layer 6 is usually about 10 to 1000 nm.

Such a recording layer may be formed using a dry coating method such as an evaporation method, a sputtering method, and an ion plating method. The thickness of the layer is about 20 nm to 1 μm.

The protective coat 8 is provided for improving corrosion resistance and abrasion resistance, and is preferably composed of various organic substances. In particular, radiation curing which can be cured by radiation such as an electron beam or ultraviolet rays. Preferably, the mold compound is composed of a radiation-cured substance.

The radiation-curable compound used for forming such a protective coat 8 preferably contains an oligoester acrylate.

The oligoester acrylate is an oligoester compound having a plurality of acrylate groups or methacrylate groups. Preferred oligosteracrylates include those having a molecular weight of 1,000 to 10,000, preferably 2,000 to 7000, and a degree of polymerization of 2 to 10, preferably 3 to 5. Of these, polyfunctional oligoester acrylates having 2 to 6, preferably 3 to 6, acrylate or methacrylate groups are preferred.

Multifunctional oligoester acrylates include Aronix M-7100, M-5400, M-5500, M-5700, and M-62.
Commercially available products such as 50, M-6500, M-830, M-8060, and M-8100 (manufactured by Toagosei Chemical Co., Ltd.) can be used, and these are represented by the following formulas (A) and (B). It is what is done.

A: acrylate group or methacrylate group, M: dihydric alcohol (eg, ethylene glycol, diethylene glycol, 1,6-hexane glycol, bisphenol A, etc.) residue, N: dibasic acid (eg, terephthalic acid, isophthalic acid, adipine) (Acid, succinic acid, etc.) residues, n: 1 to 10, preferably 2 to 5 Of these, those represented by (A) are preferred.

Such an oligoester acrylate may be used alone.

Further, another radiation-curable compound 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% by weight or more.

Other radiation-curable compounds can be used in combination with the above-mentioned oligoester acrylates, such as acrylic acid and methacrylic acid having an unsaturated double bond that is sensitive to ionization energy and exhibits radical polymerizability. Groups that are cross-linked or polymerized by irradiation such as acrylic double bonds such as acids or their ester compounds, acrylic double bonds such as diallyl phthalate, unsaturated double bonds such as maleic acid and maleic acid derivatives. And monomers, oligomers and polymers containing or introduced in the molecule. These are preferably polyfunctional, particularly preferably trifunctional or higher.

As the radiation-curable monomer, a compound having a molecular weight of less than 2,000 is used, and as the oligomer, one having a molecular weight of 2,000 to 10,000 is used.

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, and the like, and particularly preferable ones Examples of the acrylate include pentaerythritol tetraacrylate (methacrylate), pentaerythritol acrylate (methacrylate), trimethylolpropane triacrylate (methacrylate), trimethylolpropane diacrylate (methacrylate), and an acrylate modified urethane elastomer (Nipporan 4040). With functional groups such as COOH, phenol ethylene oxide adduct Acrylate (methacrylate), a compound having an acrylic group (methacrylate group) or ε-gaprotactone-acryl group attached to a pentaerythritol condensed ring shown in Japanese Patent Application No. 62-072888, and a special compound shown in Japanese Patent Application No. 62-072888. Acrylates and the like.

As the radiation-curable oligomer, an acrylic modified urethane elastomer, or these materials may be used.
Examples include those into which a functional group such as COOH has been introduced.

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

Specific examples of such a radiation-curable resin include acrylic acid having an unsaturated double bond showing radical polymerizability,
Crosslinking or polymerizing by radiation irradiation such as acrylic double bonds such as methacrylic acid or their ester compounds, allyl double bonds such as diallyl phthalanol, unsaturated bonds such as maleic acid and maleic acid derivatives It is a resin in which a group is contained or introduced into a molecule of a thermoplastic resin.

Examples of the thermoplastic resin that can be modified into a radiation-curable resin include a vinyl chloride copolymer, a saturated polyester resin, a polyvinyl alcohol resin, an epoxy resin, a phenoxy resin, and a cellulose derivative.

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

The thickness of the protective coating 8 of such a radiation-curable compound is preferably 0.1 to 100 μm, more preferably about 5 to 30 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 not sufficient,
The durability of the recording layer does not improve. On the other hand, when the thickness exceeds 100 μm, warpage of the recording medium and cracks in the protective film occur due to shrinkage caused when the resin film is cured.

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

In the present invention, examples of the radiation applied to the coating film include an ultraviolet ray and an electron beam, and an ultraviolet ray is preferable.

When ultraviolet rays are used, it is usually preferable to add a photopolymerization sensitizer to the above-mentioned radiation-curable compound.

As the photopolymerization sensitizer used in the present invention, Japanese Patent Application No. 62-07
Compounds described in 2888 and the like are preferred.

The protection substrate 10 is provided to effectively prevent the recording layer 6 from being damaged or the like.

In order to reduce the influence of thermal expansion, the protection substrate 10 used for the glass substrate 2 is made of glass, and the protection substrate 10 used for the resin substrate 2 is made of resin.

The glass or resin used for the protective substrate 10 of the present invention is not limited, and may be opaque, for example.

Note that recording / reproduction is usually performed from the substrate 2 side, but if transparent glass or resin is used as the protection substrate 10, recording / reproduction can also be performed from the protection substrate 10 side.

As the glass protective substrate 10, for example, glass that can be used for the above-described glass substrate 2 can be used. And also in this case, tempered glass, especially chemically strengthened glass is preferable.

The resin protective substrate 10 is preferably made of a rigid resin, for example, polycarbonate, acrylic resin, polyolefin, or the like.

The thickness of the protection substrate 10 should be 0.5 to 0.5 to protect the rigidity.
It should be about 2.0mm.

Then, the shape of the protection substrate 10 may be adjusted to the shape of the glass substrate 2.

In the present invention, the protection substrate 10 is integrated with the substrate 2 by the adhesive layer 9.

For the adhesive layer 9, an adhesive having a glass transition temperature Tg of -60 to -10C, preferably -40 to -15C is used.

Below the range, the flow point (FP) is low, and the adhesive flows out at a high temperature, for example, about 45 to 60 ° C.

If it exceeds the above range, the adhesive strength will be lost at a low temperature, for example, -10 ° C or lower.

Here, the flow point (FP) is a temperature at which the adhesive flows. The measurement of the glass transition temperature Tg and the flow point (FP) is performed at a vibration frequency of 10 Hz (sine wave) by a forced vibration method using a viscoelasticity measuring device. in this case,
Tg is obtained from the temperature at which the peak of the loss elastic modulus E ″ is obtained.
Is determined from the temperature at which the Young's modulus E 'on the temperature side above Tg sharply decreases.

The flow point (FP) of the adhesive having such a glass transition temperature Tg is usually about 60 to 70 ° C.

The adhesive used in the present invention has a Young's modulus of -20 ° C,
At 10 Hz, 100 kgf / mm ² or less, preferably 3 to 100 kgf / mm ² is used.

Beyond the above range, the adhesive layer 9 absorbs or relaxes the stress and strain between the substrate 2 and the protective substrate 10 or between the constituent layers such as the protective coat 8 and between the constituent layers. It is difficult.

For example, under severe conditions in which the temperature changes at -30 to 65 [deg.] C. and 20 [deg.] C./sec, the constituent layers such as the protective coat 8 peel off from the substrate 2 or other constituent layers.

On the other hand, if the Young's modulus is too low, the Young's modulus on the high temperature side is further reduced, and the adhesive strength is reduced.

For this reason, the Young's modulus is preferably 3 to 100 kgf / mm ^{2 as} described above.

Further, the adhesive has a mechanical loss coefficient tan δ of -20 ° C, 10H
The value of z is 0.1 or more, preferably 0.2 to 1.5.

If it is less than the above range, the tackiness is low and it is difficult to obtain a sufficient adhesive strength. For example, under severe conditions in which the temperature changes at −30 to 65 ° C. and 20 ° C./sec, the adhesive layer 9 becomes
It will peel off from the constituent layers such as the protective substrate 10, the substrate 2, or the protective coat 8.

If tan δ is too high, the protective substrate 10 may be displaced when the substrate 2 is warped or an external stress such as an impact is applied.

Therefore, tan δ is preferably 0.2 to 1.5 as described above.

In this case, the Young's modulus and the mechanical loss coefficient tan δ are measured as follows.

The adhesive is applied on a release paper using a roll coater or the like so as to have a thickness of 100 to 500 μm. After drying, it is peeled off from the release paper, and is measured at a vibration frequency of 10 Hz (sine wave) at -50 to 80 ° C. by a forced vibration method using a viscoelasticity measuring device.

As an adhesive having such characteristics, a hot melt adhesive is preferable.

A hot-melt adhesive generally comprises a base polymer as a main component, and additives such as a tackifier, a softener, plasticity, and wax added thereto.

Although there is no limitation on each component of the adhesive used in the present invention, as the base polymer, a polyolefin resin,
For example, polyethylene, polypropylene, polystyrene or a mixture of two or more of such copolymers and the like, and further, a mixture of these with other polyolefins, polyolefin-based copolymers, synthetic rubbers, etc. Good.

Among these, a polystyrene-polypropylene copolymer, a polystyrene-polyisoprene copolymer, a polystyrene-polybutadiene copolymer, and the like, particularly, a polystyrene-atactic polypropylene copolymer, a polystyrene-polyisoprene copolymer, and the like are preferable.

In this case, the molecular weight of the base polymer is preferably about 100,000 to 300,000.

The adhesive used in the present invention is preferably one in which about 100 to 600 parts by weight of a tackifier is added to 100 parts by weight of the base polymer.

Examples of the tackifier include various natural resins, modified products thereof, various synthetic resins, and the like. Of these, rosin, rosin derivatives, pinene-based fats and oils, and petroleum resins are preferable.

The adhesive used is preferably one in which a softener is added in an amount of about 0 to 100 parts by weight based on 100 parts by weight of the base polymer.

 As the softener, various known softeners are used.

 Further, a plasticizer and a wax are added as needed.

Examples of the plasticizer include a phthalate ester type, a phosphate ester type, a resin acid ester type, an adipate ester type, a polyhydric alcohol ester type, and an epoxy type.

As the wax, paraffin wax, low molecular weight polyethylene wax, or the like may be used.

And an ultraviolet absorber, a filler, an antioxidant, etc. may be added as needed.

When bonding, for example, when using a hot melt adhesive, a roll coater or the like may be used.

The thickness of the adhesive layer 9 is 10 to 100 μm, particularly 50 to 80 μm.
It is preferable that

In this case, if the layer thickness is less than the above range, the adhesive strength is insufficient, and if it exceeds the above range, the durability is reduced.

In the present invention, by using an adhesive having such characteristics, a strong adhesion between the substrate 2 on which the constituent layers such as the recording layer 6 and the protective coat 8 as the information carrying portion are formed and the protective substrate 10 can be obtained. It becomes possible.

That is, the adhesive layer 9 absorbs or reduces the stress and strain between the substrate 2, the protective substrate 10, and each of the constituent layers caused by thermal expansion or the like.

Therefore, for example, the magneto-optical recording disk 1 of the present invention is
Even when stored under severe thermal conditions in which the temperature changes at 30 to 65 ° C. and 20 ° C./sec, peeling between the substrate 2, the protective substrate 10, and each constituent layer can be prevented.

In this case, it is particularly effective to use a resin substrate 2 having a higher coefficient of thermal expansion than a glass substrate.

The coefficient of thermal expansion of glass is about 8 to 9 × 10 ⁻⁶ deg ⁻¹ , and the coefficient of thermal expansion of resin is about 5 to 6 × 10 ⁻⁶ deg ⁻¹ .

In the above, the case where the optical disk of the present invention is applied to a single-sided recording type magneto-optical recording disk has been described, but the present invention can also be applied to a double-sided recording type magneto-optical recording disk.

The double-sided recording type magneto-optical recording disk uses two glass substrates 2 having the above-described respective constituent layers, or uses two resin substrates 2 so that the recording layer 7 serving as an information carrying unit has an inner surface. It is obtained by bonding with an adhesive layer 9 so as to be sealed.

Also in this case, the same configuration as the above-described single-sided recording type magneto-optical recording disk can be obtained.

In addition, the present invention can be applied to an optical recording disk having a recording layer of a so-called phase-change type or the like and performing recording / reproduction by changing the reflectance.

As such a recording layer, for example, Japanese Patent Publication No. 54-4190
No. 2, Te 100435, such as Te, Se-based alloys, JP-A-58-54338, Patent No. 974257, Patent No. 974258, Te oxide system described in Patent No. 974257, various other Te, Se-based chalcogen-based, Ge-Sn, Si-Sn, etc., alloys that produce amorphous-crystalline transitions. Color changes occur due to crystal structure changes of Ag-Zn, Ag-Al-Cu, Cu-Al, etc. Alloys, such as alloys, such as In-Sb, which cause a change in the crystal grain size, may be used.

Further, the present invention can be applied to an optical recording disk having a recording layer of a so-called pit type in which a change in reflectance occurs due to pit formation.

Pit-forming recording layers include dyes such as cyanine-based, furocyanine-based, naphthalocyanine-based, anthraquinone-based, azo-based, triphenylmethane-based, pyrylium or thiapyrylium salt-based, or Te-based such as Te-based. Materials are used.

In addition, the present invention may be a read-only optical disc. However, among the above, an optical recording disk in which the information bearing portion is a recording layer is most preferable, and an optical recording disk having a recording layer containing a corrosive metal such as a rare earth metal element is most preferable.

At this time, even if a resin is used as the protective substrate 10, by providing the protective coat 8, the permeation of oxygen and moisture through the resin can be prevented, and in addition to the effects of the present invention,
This is because high reliability can be obtained.

In this case, a sufficient effect is exhibited in the thickness range of the protective coat 10 and the thickness range of 0.5 to 2.0 mm of the protective substrate 10.

In addition, when the substrate 2 and the protective substrate 10 are bonded via the protective coat 8, the generated stress and strain are added to the adhesive layer 9 and the protective coat 8 is also absorbed. The effect of becoming high is exhibited.

The optical disk of the present invention is driven at a rotation speed of 100 rpm or more to perform recording and reproduction. At this time, recording and reproduction may be performed according to a known method.

<Example> Hereinafter, the present invention will be described in more detail with reference to specific examples of the present invention.

Example 1 A glass protective layer 4, an intermediate layer 5 of SiNx, a TbFeCo recording layer 6, a SiNx protective layer 7, and a protective coat 8 were sequentially formed on a resin substrate 2, and finally, a resin layer was formed using an adhesive layer 9. Protection board 10
To produce a single-sided recording type magneto-optical recording disk shown in FIG.

The resin substrate 2 was made of a polycarbonate material, and was formed into a disk shape having an outer diameter of 200 mm and a thickness of 1.2 mm.

The substrate 2 was manufactured by injection molding, and at the same time, a tracking groove was formed on the surface thereof.

The resin protective substrate 10 was also made of polycarbonate as a material, and was formed into a disk having the same size as the substrate 2 by injection molding.

Further, the protective layer 4, the intermediate layer 5, the recording layer 6, and the protective layer 7
Was formed by a sputtering method.

Further, the protective coat 8 is formed by applying an oligoester acrylate and then irradiating ultraviolet rays to crosslink and cure.
The layer was set to 10 μm.

The adhesive layer 9 was formed by a roll coater and had a thickness of 80 μm.

Then, magneto-optical recording disk samples No. 1 to No. 3 using adhesives having different compositions were manufactured.

For the adhesive layer 9 of each sample, a hot melt adhesive containing a petroleum resin, a pinene-based resin, or the like as an additive and a base polymer shown below was used.

Sample No. 1 (the present invention) base polmer polystyrene-atactic polypropylene copolymer (molecular weight 100,000): 100% by weight Sample No. 2 (the present invention) base polymer polystyrene-polyisoprene copolymer (molecular weight 12)
10,000): 15% by weight polystyrene-polyisoprene copolymer (molecular weight 23
10,000): 85% by weight Sample No. 3 (comparative) base polymer Styrene-atactic polypropylene copolymer (molecular weight 70,000): 20% by weight Styrene-atactic polypropylene copolymer (molecular weight 130,000): 80% by weight Table 1 shows the glass transition temperature Tg, flow point (FP), Young's modulus at -20 ° C, and 10 Hz and the mechanical loss coefficient tan δ of the adhesive layer 9 of each sample.

In addition, glass transition temperature Tg and flow point (FP)
Was measured at an excitation frequency (sine wave: 10 Hz) by a forced vibration method using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho.

In addition, the measurement of the Young's modulus and the mechanical loss coefficient tanδ were measured as follows.

Adhesive on release paper using roll coater, thickness 100 ~ 5
It was applied to a thickness of 00 μm and dried. The obtained adhesive layer was peeled off from the release paper, and was applied with a viscoelastic spectrometer manufactured by Iwamoto Seisakusho at an excitation frequency (sine wave) of 10 Hz to −50.
Measured between 8080 ° C.

 The following tests were performed on each of these samples.

(Thermal shock test) The sample was placed in an atmosphere of -30 ° C and stored for 30 minutes.
Heat to ° C. Then, after storing in an atmosphere of 65 ° C. for 30 minutes, it is cooled to −30 ° C. in 5 seconds.

 The above was regarded as one cycle, and 20 cycles were performed.

(Cycle test) The sample is placed in an atmosphere at a temperature of -30 ° C and stored for 4.5 hours. Thereafter, the temperature of the atmosphere is raised to 65 ° C. at a rate of 10 ° C./hour while the sample is kept, and the room temperature is maintained at 80% RH. Then, after storing in an atmosphere of 65 ° C. and 80% RH for 4.5 hours, the speed 1
Cool to -30 ° C at 0 ° C / hour.

 The above was regarded as one cycle, and 14 cycles were performed.

 The results are as shown in Table 1.

The effect of the present invention is clear from the results in Table 1.

A test was also performed on a magneto-optical recording disk in which the glass substrate 2 and the glass protection substrate 10 were integrated, and the same results as in the above-described example were obtained.

<Effect of the Invention> In the optical disc of the present invention, since the pair of substrates are integrated so that the information carrier is enclosed, damage to the information carrier, for example, the recording layer can be sufficiently prevented.

Then, the substrate and the substrate are integrated by an adhesive having a predetermined glass transition temperature Tg, a Young's modulus, and a mechanical loss coefficient tanδ.

Therefore, for example, even when stored under severe thermal conditions in which the temperature changes at −30 to 65 ° C. and 20 ° C./sec, between the substrates, or between these and each constituent layer such as a protective coat,
Furthermore, stress and strain generated between the constituent layers are absorbed or reduced by the adhesive layer, and peeling between the constituent layers can be prevented.

Therefore, a highly reliable product can be obtained as an optical disk.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of the optical disk of the present invention. DESCRIPTION OF SYMBOLS 1 ... Magneto-optical recording disk 2 ... Substrate 3 ... Resin layer 4 ... Protective layer 5 ... Intermediate layer 6 ... Recording layer 7 ... Protective layer 8 ... Protective coat 9 ... Adhesive layer 10 ... Protective substrate

Claims (3)

(57) [Claims] An optical disc having a pair of substrates, wherein an information carrying portion is formed on at least one of the substrates, and the pair of substrates are integrated with an adhesive so that the information carrying portion is enclosed. The pair of substrates are both made of resin or both made of glass, and the glass transition temperature Tg of the adhesive is −60 to −10 ° C.,
An optical disc having a Young's modulus of not more than 100 kgf / mm ² at -20 ° C and 10 Hz, and a mechanical loss coefficient tanδ of not less than 0.1 at -20 ° C and 10 Hz. 2. The optical disk according to claim 1, wherein said information carrying section is a recording layer. 3. The optical disk according to claim 2, wherein the recording layer contains a rare earth metal element, and a protective coat made of resin is provided on the recording layer.