JP2741530B2 - optical disk - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an optical disk, particularly a magneto-optical recording disk, a phase-change optical recording disk, a pit-forming optical recording disk, a read-only optical disk, and the like.

<Conventional technology> Among optical discs, optical recording discs, in particular, are formed by providing a recording layer as an information carrier on a substrate, and 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 in terms of weight reduction of the disk and ease of forming grooves and pits for tracking.

In addition, recently, in order to obtain a high transfer rate, high speed rotation is required for recording / reproducing.

However, in the case of a resin substrate, surface rigidity is insufficient due to insufficient rigidity, and the focus tracking error increases when driving at a high speed of 1800 rpm or more, especially 3000 rpm or more.

Therefore, in order to cope with the high-speed rotation drive that has recently been required, particularly at 1800 rpm or more, and further at 3000 rpm or more, it is necessary to consider using a glass substrate with high mechanical strength. No.

However, if the glass substrate is accidentally dropped or hit, the glass substrate may be damaged.

In addition, when chemically strengthened glass having a particularly high strength is used, there is a disadvantage that the glass is broken into small pieces and the small pieces are scattered.

On the other hand, in order to prevent mechanical damage due to cracking or the like of the recording layer, it is necessary to provide a protective substrate on the recording layer side of the substrate or to integrate a pair of substrates so that the recording layer is enclosed.

In this case, when a glass protective substrate or the like is bonded to the glass substrate to prevent peeling due to a difference in thermal expansion coefficient,
The mass of the disc exceeds the limit. For this reason, it is difficult to obtain a necessary rotation speed, particularly a stable high rotation speed.

 In addition, the problem at the time of damage is not solved.

In order to prevent peeling due to a difference in the coefficient of thermal expansion, a resin substrate or a protection substrate can be bonded to the resin substrate to prevent mechanical damage to the recording layer.

However, also in this case, the problem of the focus tracking error due to the high-speed rotation drive is not solved.

In order to solve such a problem, in particular, the problem at the time of high-speed rotation drive, one of the pair of substrates or one of the substrate and the protection substrate may be made of glass, and the other is made of resin.

However, an optical disk in which one of a pair of substrates or a substrate and a protection substrate is made of glass and the other is made of resin has not been known.

This is presumably because bonding glass and resin having different coefficients of thermal expansion was not considered to be advisable for an optical disk that could be placed under severe storage conditions.

By the way, U.S. Pat.No. 4,503,531 discloses that a resin substrate and a resin substrate have a softening point of 140 ° C. or less, a normal tensile adhesive strength of 1 kg / cm ² or more at 20 ° C., and a melt viscosity of 160 P at 160 ° C.
It has been proposed to bond with the following hot melt adhesives.

However, such an adhesive exerts an adhesive effect when bonding a resin substrate having substantially the same coefficient of thermal expansion to a resin substrate or a protective substrate, but a glass substrate having a different coefficient of thermal expansion, It is not suitable for bonding with a resin substrate or protection substrate.

In other words, when an optical disk in which a glass substrate and a resin substrate or a protection substrate are integrated with an adhesive is stored under a high or low temperature, for example, under severe conditions in which the temperature changes at −20 to 55 ° C. Due to the difference in the coefficient of thermal expansion, stress and strain are generated in the substrate, the protective substrate, or the constituent layers such as the recording layer, the protective coat, and the adhesive layer. For this reason, even if they are integrated with an adhesive used for a conventional optical disk, the substrate and the substrate, the substrate and the protective substrate, or these and each of the constituent layers, or the constituent layers and the constituent layers are peeled off.

As described above, it is difficult to obtain a highly reliable optical disk by integrating the glass substrate and the resin substrate or the protection substrate with the adhesive used for the conventional optical disk.

<Problems to be Solved by the Invention> The object of the present invention is under high and low temperatures, for example, -20 to
Even when placed under severe conditions where the temperature changes at 55 ° C., each of the constituent layers such as the substrate and the substrate, the substrate and the protective substrate, these and the protective coat, and further, the constituent layers and the constituent layers do not peel off, and An object of the present invention is to provide an optical disk which can perform stable high-speed rotation without causing surface wobble and deformation and has good recording / reproducing characteristics.

<Means for Solving the Problems> Such an object is achieved by the present invention of the following (1) to (6).

(1) having a pair of substrates, forming an information carrier on at least one substrate, and enclosing the information carrier,
An optical disc in which the pair of substrates is integrated with an adhesive, wherein one of the pair of substrates is made of glass, the other is made of resin, and has a glass transition temperature of the adhesive.
An optical disc characterized by a Tg of −60 to −10 ° C. (2) Of the pair of substrates, an information carrying portion is formed on a glass substrate, and this is integrated with a resin protection substrate. The optical disc according to the above (1).

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

(4) The above-mentioned (3), wherein the recording layer contains a rare earth metal element, and a protective coat made of resin is provided on the recording layer.
An optical disk according to claim 1.

(5) The adhesive has a Young's modulus of 100k at -20 ° C and 10Hz.
The optical disc according to any one of (1) to (4), which has a gf / mm ² or less.

(6) The mechanical loss factor tan δ of the adhesive is −20 ° C., 1
The optical disc according to any one of the above (1) to (5), which has a value of 0.1 or more at 0 Hz.

<Operation> The optical disk of the present invention is a glass substrate having at least one information carrying portion such as a recording layer and a resin protection substrate, an adhesive having a glass transition temperature Tg of -60 to -10 ° C. Be integrated. For this reason, even when stored under severe conditions of high or low temperature, for example, a temperature change at −20 to 55 ° C., between a glass substrate and a resin substrate, or between these and each constituent layer such as a protective coat, and The adhesive layer absorbs or alleviates the stress, strain, and the like generated between the constituent layers, and the peeling can be completely prevented.

Therefore, it is possible to realize a lightweight and rigid optical disk in which one of the pair of substrates is made of glass and the other is made of resin, and sufficient reliability can be obtained.

According to the optical disc of the present invention, stable high-speed rotation drive of 1800 rpm or more, especially 3000 rpm or more can be easily performed, and in this case, surface shake and deformation can be prevented.

Further, since one substrate is made of resin, it is possible to prevent breakage when the optical disc is dropped or scattered glass when broken.

In particular, according to an optical disk in which an information carrying portion such as a recording layer is formed on a glass substrate and integrated with a protective substrate made of resin, it is possible to prevent birefringence which is an obstacle to recording / reproduction. it can. The glass substrate on which recording / reproduction is performed is excellent in heat resistance and moisture resistance, and therefore hardly deforms or deteriorates even when stored for a long time at high or low temperature and high or low humidity.

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, preferably glass.

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

 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, acrylic resin, polycarbonate, epoxy resin, polymethylpentene, 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, a predetermined pattern such as pits or grooves may be simultaneously formed on the substrate surface for tracking, addressing, etc. by using injection molding or 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 or the like which has been subjected to the above-mentioned chemical strengthening treatment may be used. However, since the mechanical strength is particularly high, the alumina silicate glass is subjected to the chemical treatment. It is preferable to use those that have been used.

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 2 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. 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 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 from various derivative substances, and the layer thickness is preferably 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 recording layer compositions include TbFeCo, Dy
There are TbFeCo, NdDyFeCo, NdGdFeCo and the like.

In the recording layer, Cr, Al, T
i, Pt, Si, Mo, Mn, 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 curable by radiation such as electron beams and ultraviolet rays. The curable compound is preferably 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 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. 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: an acrylate group or a methacrylate group, M: a dihydric alcohol (eg, ethylene glycol, diethylene glycol, 1,6-hexane glycol, bisphenol A, etc.) residue, N: dichloric acid (eg, terephthalic acid, isophthalic acid, adipine) Acid, succinic acid, etc.) residue, n: 1-10,
Preferably 2-5 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 crosslinked or polymerized by irradiation such as acrylic double bonds such as acids or their ester compounds, allyl double bonds such as diallyl phthalate, unsaturated double bonds such as maleic acid and maleic acid derivatives, etc. 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 thereof include pentaerythritol tetraacrylate (methacrylate), pentaerythritol acrylate (methacrylate), trimethylolpropane triacrylate (methacrylate), trimethylolpropane diacrylate (methacrylate), an acrylic modified product of urethane elastomer (Nipporan 4040), or these. Products with functional groups such as COOH, phenol ethylene oxide adducts Acrylate (methacrylate), pentaerythritol fused ring acrylic group (methacryl group) shown in Japanese Patent Application Sho 62-072888 or ^epsilon - caprolactone - compound with a acryl group, and special shown in Japanese Patent Application Sho 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,
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 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 6 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.

The protection substrate 10 used for the glass substrate 2 is made of resin, and the protection substrate 10 used for the resin substrate 2 is made of glass.

Thus, one of the pair of substrates 2 and 10 is made of glass,
When the other is made of resin, a disk which is lightweight and has high rigidity can be obtained. For this reason, stable high-speed rotation drive without surface shake, for example, rotation drive of 3000 rpm or more can be performed.

Furthermore, since one of the substrates is made of resin, it is possible to prevent breakage when the disk is dropped or to prevent glass from scattering when the disk is broken.

Particularly preferred in the present invention is a disk in which the glass substrate 2 and the resin protection substrate 10 are integrated.

In other words, according to this disk, in addition to the prevention of birefringence and the improvement of weather resistance and durability described above, it is possible to further reduce surface blur during high-speed rotation driving.

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 such as polycarbonate, acrylic resin, and polyolefin.

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

Then, the shape of the protection substrate 10 may be adjusted to the shape of the 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 above range, the flow point (FP) is low, and the adhesive flows out at a high temperature, for example, about 45 to 50 ° 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 determined from the temperature at which the peak of the loss modulus E ″ occurs, and FP is determined from the temperature at which the Young's modulus E ′ on the high temperature side above Tg rapidly 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,
10Hz at 100 kgf / mm ² or less, particularly preferably those of 3~100kgf / mm ^2.

Beyond the above range, the adhesive layer 9 absorbs or relieves stress and strain generated between the substrate 2 and the protective substrate 10 or between each of the constituent layers such as the protective coat 8 and between the constituent layers. Is difficult.

For example, under severe conditions in which the temperature changes at -20 to 55 [deg.] C., 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.

Therefore, the Young's modulus is, as described above, particularly 3 to 100 kgf / m
m ² is preferred.

Further, the adhesive has a mechanical loss coefficient tan δ of -20 ° C, 10H
It is preferable that z is 0.1 or more, especially 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 where the temperature changes at -20 to 55 ° C., the adhesive layer 9 becomes
0, peels off from the constituent layers such as 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 particularly 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, a plasticizer, and a wax.

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, if one or a mixture of two or more kinds of polyethylene, polypropylene, polystyrene and copolymers containing them, and the like, and further added with other polyolefins, polyolefin-based copolymers, synthetic rubbers and the like are used. 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 suitable.

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 resins, petroleum resins and the like 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 fatty 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, the substrate 2 made of glass and resin having different coefficients of thermal expansion and the protective substrate 10 can be firmly bonded.

That is, the constituent layers such as the recording layer 6 and the protective coat 8 as the information carrying unit are formed on the substrate 2, but the stress and strain generated between the substrate 2, the protective substrate 10 and each constituent layer are not adhered. It is absorbed or relaxed by the agent layer 9.

Therefore, for example, the magneto-optical recording disk 1 of the present invention is
Even under severe conditions in which the temperature changes at 20 to 55 ° C., peeling between the substrate 2, the protective substrate 10, and each constituent layer can be prevented.

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 ⁻⁵ 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 includes an adhesive layer such that a glass substrate 2 having the above-described respective constituent layers and a resin substrate 2 are enclosed in a recording layer 7 as an information carrier. 9 obtained by bonding.

Also in this case, the same effects as those of 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, described in Patent No. 100004835, Te, Se-based alloy, 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 also be applied to an optical recording disk having a so-called pit forming type recording layer in which a change in reflectance occurs due to pit formation.

Pit-forming recording layers include dyes such as cyanine-based, phthalocyanine-based, naphthalocyanine-based, anthraquinone-based, azo-based, triphenylmethane-based, pyrylium or thiapyrylium salt-based, and 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, the provision of the protective coat 8 can prevent the permeation of oxygen and moisture through the resin, and achieve high reliability in addition to the effect of the present invention. Because you can get it.

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 bonding the protective substrate 10 made of resin via the protective coat 8, the difference in the coefficient of thermal expansion between the two materials, glass and resin, which have significantly different coefficients of thermal expansion, is determined by the adhesive layer 9.
In addition, since the protective coat 8 is also absorbed, an effect that the preservability at high and low temperatures is extremely 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.

In the present invention, sufficient characteristics can be obtained by rotation at 1800 rpm or more, particularly 3000 rpm or more, and more preferably 3000 to 5000 rpm.

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

[Example 1] A resin layer 3, a glass protective layer 4,
An intermediate layer 5, a TbFeCo recording layer 6, a SiNx protective layer 7, and a protective coat 8 of SiNx are formed, and a resin protective substrate 10 is finally bonded by an adhesive layer 9 to form a single-sided recording type shown in FIG. A magneto-optical recording disk was manufactured.

The glass substrate 2 was made of alumina silicate-based chemically strengthened glass and had a disk shape with an outer diameter of 200 mm and a thickness of 1.2 mm.

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

The resin layer 3 was formed by the 2P method, and a tracking groove was formed on the surface thereof. The protective layer 4, the intermediate layer 5, the recording layer 6, and the protective layer 7 were 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 a base polymer shown below and additives was used.

Sample No. 1 (the present invention) base polymer 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) of 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 -20 ° C and stored for 30 minutes.
Heat to ° C. Then, after storing in an atmosphere of 55 ° C. for 30 minutes, it is cooled to −20 ° 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 -20 ° C and stored for 4.5 hours. Thereafter, the temperature of the atmosphere is increased to 55 ° C. at a rate of 10 ° C./hour while the sample is kept, and the humidity is maintained at 80% RH.

Then, after storing in an atmosphere of 55 ° C and 80% RH for 4.5 hours,
Cool to -20 ° C at a rate of 10 ° 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.

In this case, the comparative sample No. 3 showed 10% in the thermal shock test.
As shown in Table 1, 8 out of 10 peeled off after the cycle.

The peeling between the glass substrate 2 and the resin protective substrate 10 in the thermal shock test and the cycle test occurred between the adhesive layer 9 and the protective coat 8.

<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.

Since one substrate is made of glass and the other substrate is made of resin, the substrate has sufficiently high rigidity, and the weight can be reduced.

For this reason, stable high-speed rotation drive of 1800 rpm or more, especially 3000 rpm or more can be easily performed, and surface blurring and deformation can be prevented.

Therefore, according to the optical disk of the present invention, good recording / reproducing characteristics can be obtained even during high-speed rotation driving.

Further, since one of the substrates is made of resin, it is possible to prevent breakage when the optical disc is dropped or scattering of the glass when it is broken.

Further, the glass substrate and the resin substrate are integrated by an adhesive layer having a glass transition temperature Tg of −60 to −10 ° C.

For this reason, the stress or strain between the glass substrate and the resin substrate, or between them, and each of the constituent layers such as a protective coat, a recording layer, an adhesive layer, and the like, and also between the constituent layers, caused by a difference in the coefficient of thermal expansion. Absorbed or mitigated by the adhesive layer.

Therefore, even when stored under severe conditions in which the temperature changes at a high or low temperature, for example, at −20 to 55 ° C., the glass substrate and the resin substrate, and these and each of the constituent layers and the constituent layers and the constituent layers Peeling can be prevented. Therefore, a highly reliable product can be obtained as an optical disk.

In particular, an optical disk of the present invention in which an information carrying portion such as a recording layer is formed on a glass substrate and integrated with a protective substrate made of resin has a glass substrate side on which recording / reproduction is performed. Excellent in nature. For this reason, even if the glass substrate is stored for a long period of time under high or low temperature and high or low humidity, the glass substrate hardly undergoes transformation or deterioration.

Since birefringence hardly occurs, recording and reproduction can be performed more accurately by using this 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 (6)

(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. An optical disk, wherein one of the pair of substrates is made of glass, the other is made of resin, and the glass transition temperature Tg of the adhesive is −60 to −10 ° C. 2. The optical disk according to claim 1, wherein an information carrying portion is formed on a glass substrate of said pair of substrates, and is integrated with a resin protective substrate. 3. The optical disc according to claim 1, wherein the information carrying section is a recording layer. 4. The optical disk according to claim 3, wherein the recording layer contains a rare earth metal element, and a resin protective coat is provided on the recording layer. 5. The optical disk according to claim 1, wherein the adhesive has a Young's modulus of not more than 100 kgf / mm ² at −20 ° C. and 10 Hz. 6. The adhesive has a mechanical loss coefficient tanδ of -2.
The optical disc according to any one of claims 1 to 5, wherein the optical disc temperature is 0.1 or more at 0 ° C and 10 Hz.