JPH0817073A - Optical disk and its production - Google Patents

Abstract

PURPOSE:To suppress the deterioration of an optical disk due to an adhesive layer during production, use and preservation. CONSTITUTION:Two substrates 3 each consisting of a recording film 2 and a transparent substrate 1 are coated with an adhesive contg. 95-75% UV-curing monofunctional acrylic resin and 5-25% UV-curing epoxy resin to form adhesive layers 4. The two transparent substrates are placed opposite to each other with the adhesive layers inward and they are press-bonded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk suitable for recording and reproducing audio, images, information, etc., and a method for manufacturing the same.

[0002]

2. Description of the Related Art An optical disc is formed by forming a recording metal film on a transparent replica substrate such as glass or transparent plastic having groove-shaped or hole-shaped irregularities for a servo track and the like. The films are formed by facing each other with a constant gap so that the films are on the inside, and then bonding the films with an adhesive.

In the conventional method of manufacturing an optical disk, a hot melt adhesive or a chemical reaction adhesive is used for adhering a transparent replica substrate. Hot melt adhesives are excellent in terms of simplification of manufacturing workability and cost reduction, and in JP-A-63-67238, a thermoplastic hot melt adhesive is used.

Further, the chemical reaction type adhesive has an effect of suppressing the deformation of the disk and has a one-component anaerobic curing type adhesive (described in JP-A-61-151853).
Liquid non-mixing type adhesive (described in Japanese Patent Laid-Open No. 61-50231) and one-component moisture-curing adhesive (described in Polymer 42, February issue (1993) 111p). ) Was used.

In recent years, demands for increasing the amount of information to be recorded and increasing the processing speed of optical discs are rapidly increasing in recent years. In order to meet these requirements, it is necessary to increase the storage capacity and rotate the disk at high speed.

As a technique of mixing and using two kinds of adhesives, Japanese Patent Laid-Open No. 59-68849, Japanese Patent Laid-Open No. 2-3117, Japanese Patent Laid-Open No. 1-173340,
JP-A-2-223037, JP-A-2-22303
8 and JP-A-3-219476.

[0007]

However, the above-mentioned adhesive has the following problems. Thermoplastic hot-melt adhesives suffer from defects due to heat during adhesive application and pressure during bonding, or plasticity and elastic deformation during high-speed rotation, and deformation and peeling due to changes with time during storage.

The one-component anaerobic curable adhesive has a short curing time of seconds and is bonded and cured under normal pressure. For this reason, bubbles are easily mixed, and the mixed bubbles are hard to come off, and the mixture is cured with the bubbles mixed therein. Further, since the cured product obtained by curing is hard, the bubbles cannot be sufficiently absorbed and relaxed, resulting in defects such as poor flatness of the disk and the uncured product in the bubble portion corroding the recording layer.

When a two-liquid non-mixing type adhesive is used, the two liquids are separately applied in order to a film thickness of several tens of μm, and pressure is applied to bond the substrates. When such a bonding method is adopted, unevenness in curing will occur due to the pressure at the time of bonding. This is because the adhesive coating film is liquid and thick, so that the adhesive flows at the bonding interface, resulting in non-uniform mixing of the two liquids. Such uneven curing causes wrinkles in the recording layer, which causes defective recording and reproduction.

The one-part moisture-curable adhesive is one in which a reaction is initiated by the surrounding moisture to make the adhesive surface tacky. When the adhesive is used, the adhesive is applied to the substrate and then adhered before the tackiness is lost. Since the one-component moisture-curable adhesive reacts with ambient moisture, it is difficult to control the curing and the workability is poor. Further, the curing speed of the adhesive after bonding is extremely slow, which causes deformation of the disk.

As described above, when a thermoplastic hot melt adhesive is used, defects may occur during the manufacture of optical disks. Further, when the optical disc is used, deformation may occur due to high-speed access and high-speed rotation. Further, when the optical disc is stored, it may be deformed or peeled off due to aging. When using a one-component anaerobic curing type adhesive, a two-component non-mixing type adhesive, or a one-component moisture curing type adhesive,
Although there is no problem during use and storage, there is a problem that defects occur during the manufacture of the optical disc.

Therefore, the present invention reduces an optical disc manufacturing defect, deformation due to high-speed access and high-speed rotation when the optical disc is used, and deformation and peeling due to aging during storage of the optical disc and the optical disc. It is intended to provide a manufacturing method.

[0013]

In order to achieve the above object, the present invention has a pair of opposing substrates and an adhesive layer, at least one of the substrates having a recording film, and the adhesive layer Provides an optical disc in which the adhesive layer contains an ultraviolet-curable monofunctional acrylic resin and an ultraviolet-curable epoxy resin in the optical disc disposed in the gap between the pair of opposed substrates. The adhesive layer has a combined amount of the UV-curable monofunctional acrylic resin and the UV-curable epoxy resin of 100.
%, The blending amount of the UV-curable monofunctional acrylic resin is preferably 95 to 75%, and the blending amount of the UV-curable epoxy resin is preferably 5 to 25%.

Further, in the present invention, an adhesive applying step of applying an adhesive to two transparent substrates having a recording layer formed on at least one side to form an adhesive layer, and the adhesive layer is placed inside. In the optical disc manufacturing method, which includes a bonding step in which the two transparent substrates are opposed to each other and are pressed and bonded, the adhesive contains a UV-curable monofunctional acrylic adhesive and a UV-curable epoxy adhesive. An optical disc manufacturing method is provided. When the total amount of the UV-curable acrylic adhesive and the UV-curable epoxy adhesive is 100%, the amount of the UV-curable monofunctional acrylic adhesive is 95 to 75.
%, And the compounding amount of the ultraviolet curable epoxy adhesive is 5
25%. It is desirable to perform an ultraviolet irradiation step of irradiating the adhesive layer with ultraviolet rays between the adhesive application step and the adhesive step. Furthermore, it is desirable that the bonding step be performed in a reduced pressure atmosphere.

[0015]

According to the present invention, an ultraviolet curable monofunctional acrylic adhesive (95
~ 75%) and UV curable epoxy adhesive (5-25
%). By doing so, the adhesive layer for adhering the substrate can be cured in two or more steps, and further, by irradiating with ultraviolet rays in advance before adhering, the adhesive layer made of the adhesive is made to have tackiness. You can

It is desirable that the adhesive has tackiness before adhesion. This is to prevent the adhesive layer from becoming non-uniform due to the pressure applied during bonding. If the adhesive layer becomes non-uniform, the flatness may be lost or the recording layer may be defective. Further, the tackiness of the adhesive needs to be rapidly developed. This is because if it takes a long time to develop tackiness as in the case of a one-component moisture-curable adhesive, foreign matter is mixed into the adhesive layer during that time. Therefore, in the present invention, an adhesive which is a mixture having the above-mentioned composition is used.
In curing the mixture, the UV-curable monofunctional acrylic adhesive is first cured. At this time, the adhesive layer is in a state in which the cured product and an adhesive that has not yet been cured and has a slow curing speed are mixed. Since the cured product has flexibility, tackiness is exhibited in the adhesive layer in which the cured product having flexibility and the liquid epoxy adhesive are mixed. The development of tackiness depends on the curing of an adhesive having a high curing rate, and therefore occurs rapidly after ultraviolet irradiation.

On the other hand, in the case of adhering only with an adhesive having a high curing speed, the adhesive layer will be cured with air bubbles mixed therein. In order to ensure the flatness of the optical disc, the adhesive has enough time for the mixed bubbles to escape.
A slow cure is desirable. In the present invention, the adhesive contains an epoxy adhesive having a slow curing rate, and the mixed air bubbles can be released before the adhesive layer is completely cured.

It is desirable that the unevenness of application of the adhesive is 1 μm or less. By doing so, it is possible to further eliminate the uneven flow of the adhesive at the time of bonding and prevent unevenness due to uneven curing.

Further, it is desirable that the bonding step is performed under a reduced pressure atmosphere. This is to prevent air bubbles from being mixed into the adhesive layer and the generation of an uncured product, and further to promote the release of air bubbles once mixed. In an atmospheric pressure atmosphere, the bubbles mixed in cause unevenness in the recording film, and oxygen in the bubbles reacts with the radicals generated during the curing reaction and oxygen,
It does not cure uniformly, which has the adverse effect of producing uncured products.

Next, the chemical reaction type adhesive used for the optical disk of the present invention will be described in detail. The chemical reaction type adhesive is one in which an object to be bonded and an adhesive are bonded by a chemical reaction, and is superior in adhesive strength, heat resistance and mechanical strength as compared with a thermoplastic hot melt adhesive, When used as an adhesive for optical discs, it has excellent adhesive strength and high reliability, and has excellent heat resistance, making it suitable for various environments.
Due to its excellent mechanical strength, it is possible to obtain an optical disk that can withstand high speed rotation. A mixture of a UV-curable monofunctional acrylic adhesive and a UV-curable epoxy adhesive is used as the chemical reaction adhesive.

The UV-curable monofunctional acrylic adhesive is suitable for application to the adhesive of the present invention because the curing rate does not change depending on the material of the adhesive surface and the curing rate is generally high. Specifically, as long as it has a characteristic that it cures in a single item in 10 to 60 seconds, a pair of transparent substrates can be aligned and workability is good. In the present invention, it is desirable to use one that has a high curing rate as a single item, does not change even when mixed with an ultraviolet curable epoxy adhesive, and has flexibility after curing. This is because the tackiness of the mixed adhesive is expressed by the softness.

The UV-curable monofunctional acrylic adhesive is composed of a monofunctional acryloyl group-containing monomer, a monofunctional methacryloyl group-containing monomer, or an oligomer of these monomers as a main component, and a curing agent and a promoter. An agent, a storage stabilizer, etc. are preferably added. In addition, in the present invention, as the main agent, one type of the above-mentioned monomer or oligomer may be used, or two or more types may be mixed and used. Examples of the above monomers include hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, tetrafurfuryl acrylate, tetrafurfuryl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, benzyl acrylate. , Benzyl methacrylate, methoxy polyethylene glycol acrylate, lauryl acrylate, lauryl methacrylate,
Stearyl acrylate, stearyl methacrylate,
Examples include isobornyl acrylate, isobornyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, phenoxypolyethylene glycol acrylate, and phenoxypolyethylene glycol methacrylate.

Examples of the above curing agent include benzyl, benzyls such as methyl-o-benzoate,
Benzoin, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether and other benzoins, benzophenone, 4-methoxybenzophenone and other benzophenones, acetophenone,
Acetophenones such as 2,2-diethoxyacetophenone, benzylmethyl ketal, 4- (isopropylphenyl) -2-hydroxy-2-methylpropanol-
1-one and the like, which are used alone or in combination of two or more.

Examples of the stabilizer include benzoquinone and hydroquinone. Furthermore, it is also possible to add an appropriate amount of a thickener, a plasticizer and the like.

The ultraviolet-curing type epoxy adhesive is suitable for application to the adhesive of the present invention because the curing rate does not change depending on the material of the adhesive surface and the curing rate is generally slow. In the present invention, it is desirable to use an ultraviolet curable monofunctional acrylic adhesive whose curing rate does not change even when mixed with it. It should be noted that if the curing rate is such that it cures in 1 to 3 minutes, a pair of transparent substrates can be aligned and workability is good. Further, it is desirable to use a material that mixes uniformly with the UV-curable monofunctional acrylic adhesive.

In the constitution of the above-mentioned UV-curable epoxy adhesive, a bifunctional glycidyl group-containing monomer or an oligomer thereof is used as a main component, and a curing agent, an accelerator, a storage stabilizer and the like are preferably blended. Here, the bifunctional glycidyl group-containing monomer includes alicyclic epoxy, bisphenol A type epoxy, bisphenol F type epoxy, novolac type epoxy, hydrogenated bisphenol A type epoxy, epoxidized polybutadiene or butadiene copolymer. .

Examples of the above curing agent include diallyl iodonium salt, diphenyl iodonium tetrafluoroborate, triallyl sulfonium salt, triphenyl sulfonium hexafluoroantimonate and triallyl selenium salt.

[0028]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic view of the optical disc of the present invention. When the optical disk has a disk shape with a hole 34 in the center, it is shown as a partially cutaway, partially sectional view in order to make it easier to see the internal structure. 2 is a sectional view taken along the line AB in FIG. The optical disk of each of the following examples has a pair of opposing substrates 3 and an adhesive layer 4. The adhesive layer 4
Is disposed in the gap between the pair of opposed substrates 3 and is made of a cured product of a two-step curable adhesive. The substrate 3 has a transparent replica substrate 1 and a recording metal film (recording film) 2 and faces each other with the recording film 2 inside. In each of the following examples, two substrates 3 having the same unevenness and recording film are bonded to each other to manufacture an optical disc capable of recording information on both sides. However, one substrate is
It is not necessary to have the unevenness or the recording film 2. In this case, information can be recorded on only one side.

The transparent replica substrate 1 is a medium through which a laser for recording / reproducing is transmitted. For this reason, it is necessary to have characteristics such that it is optically isotropic and has an optical strain of 50 nm or less, which is a measure of optical characteristics. The type is not particularly limited, but examples include a glass substrate and polymethylmethacrylate.
Substrate, polycarbonate substrate, polyolefin substrate,
There is a heat or light curing resin substrate or the like.

The recording film 2 corresponds to a light spot diameter of about 0.6 to 1 μm, forms a recording domain in which the shape of the recording film does not change such as phase change and magneto-optical property, and has a C / N ratio. 6
The type is not particularly limited as long as the characteristic of 0 dB or more can be obtained. For example, tellurium oxide film (TeO)
x), SbSe / BiTe laminated film, rare earth-transition metal amorphous alloy, TbFeCo-based oxide film, GdTbFe
-Based oxide film, DyFeCo-based oxide film, TbDyFeCo-based oxide film, garnet-based oxide film, Pt / Co laminated material, G
eSbTe, InSeTeCo, InSbTe, In-
Examples include Sb-based alloys.

In each of the following examples, the adhesive layer 4 is formed by using a two-step curable adhesive (a mixture of two kinds of adhesives having different curing rates). An agent (a mixture of three or more kinds of adhesives having different curing rates) may be used.

In each of the following examples, a mixture of an acrylic adhesive and an epoxy adhesive was used as the two-step curable adhesive. As the acrylic adhesive, a two-component acrylic adhesive containing phenoxyethyl methacrylate (PO-A) or lauryl acrylate (LA) as a base monomer and hydroxybutyl methacrylate (HOB) as a diluent was used. As the epoxy adhesive, a bisphenol A type Ep-828 manufactured by Yuka Shell Co., Ltd.
(Molecular weight about 380) or Ep-1 manufactured by Yuka Shell Co., Ltd.
007 (molecular weight about 2900) was used. The mixing ratio of each adhesive and its characteristics in Examples 1 to 8 are shown in (Table 1). The unit of the mixing ratio described in (Table 1) is% by weight.

[0033]

[Table 1]

Each of the above acrylic adhesives cures in a few seconds when irradiated with ultraviolet rays, and has softness even after curing.
Further, each of the epoxy adhesives is cured in 30 seconds to 1 minute when irradiated with ultraviolet rays, and after curing, becomes harder than the cured product of the acrylic adhesive. Therefore, the mixture of the acrylic adhesive and the epoxy adhesive, if pre-irradiated with ultraviolet rays before adhesion, the portion of the acrylic adhesive having flexibility in a few seconds is cured, the epoxy adhesive is cured. Before starting, it will develop tackiness. This tackiness prevents the adhesive layer from becoming non-uniform due to adhesive flow during lamination. Also, because the epoxy adhesive cures slowly,
It is avoided that the bubbles are cured while being mixed in the adhesive layer.

As the curing agent for each adhesive, the following polymerization initiators were used. As for the acrylic adhesive, a radical reaction type photopolymerization initiator (Darocur 11 manufactured by Ciba-Geigy Co., Ltd.) is used in an amount of 5% by weight based on the amount of the acrylic adhesive compounded.
73) was added. Also, for epoxy adhesives,
An ionic polymerization type photopolymerization initiator (SP-150 manufactured by ADEKA CORPORATION) was added in an amount of 5% by weight based on the amount of the epoxy adhesive compounded.

In each of the embodiments described below, a stamper is used to manufacture an optical disc. In addition, the stamper has an uneven shape corresponding to the information pattern,
The type of the uneven surface is not particularly limited as long as it is a copy type having excellent releasability. For example, any of an electroformed stamper, a resin stamper, a glass stamper, etc. may be used. The stamper used in each example was prepared according to the manufacturing method of (a) to (f) shown in FIG.

First, a glass disk 17 whose both surfaces are polished
(Outer diameter: 350 mm, inner diameter: 10 mm, thickness: 10 m
m) is prepared (a). Next, a positive type photoresist is spin-coated on one surface of the glass disk 17 to give 0.14
A photoresist film 16 having a film thickness of μm is formed (b). Then, using a recorder, the photoresist film 1
An information signal is written in 6 using an Ar laser (wavelength: 458 nm), and the photoresist film is developed to form grooves and pits representing the information signal (c). In addition,
In the optical disc manufactured in this example, the irregularities represent auxiliary information such as an address for reading information recorded on the recording film. 40 is formed on the photoresist film 16 having the irregularities formed as described above by the vacuum deposition method.
A Ni film 5 having a thickness of nm is formed (d). Further, using the Ni film 5 as an electrode, 300
A Ni electroformed film 6 having a thickness of μm was formed (e), and the glass disk 17 and the Ni film 5 were separated to produce a Ni stamper 7 (f).

(Examples 1 and 2) As the adhesive, an adhesive having the composition described in the columns of Examples 1 and 2 in Table 1 was used,
An optical disc was manufactured as follows. Manufacturing method,
As shown in FIG. In this embodiment, a replica substrate 1 made of a polycarbonate resin is prepared, and as the recording film 2, a SiN enhance film 12, a TbFeCo magnetic film 13, an AlN reflective film 14, and a SiN protective film 15 are used as a replica substrate. An optical disk was obtained by forming the optical disk on the surface of No. 1 and bonding with the above adhesive.

First, a Ni stamper 7 is prepared (a). The stamper 7 is attached to a molding die 8 having an injection hole, and a polycarbonate resin 10 is placed in a gap 9 in the molding die 8.
(Molecular weight: about 15,000) is melted by heating and injected (b). The gap 9 has a disk shape with an outer diameter of 300 mm and a thickness of 1.2 mm, and has a central hole with an inner diameter of 35 mm at the center (that is, the molding die 8 has an outer diameter of 35 mm at the center). It has a cylindrical protrusion (not shown), and there is no gap in this part.) Next, the polycarbonate resin is cooled and cured, and the stamper 7 and the molding die 8 are removed, and the replica substrate 1 made of the polycarbonate resin (outer diameter:
(300 mm, central hole diameter: 35 mm, thickness: 1.2 mm)
Can be obtained (c).

Then, on the surface (information pattern surface) on which the unevenness of the obtained replica substrate 1 is transferred, the SiN enhance film 12 (thickness: 30 nm) and the TbFeCo magnetic film 13 are formed.
(Thickness: 30 nm), AlN reflective film 14 (thickness: 30 n
m) and the SiN protective film 15 (thickness: 30 nm) were sequentially formed by the sputtering method to form the recording film 2 and the substrate 3 was obtained (d).

On the recording film 2 of the substrate 3 produced as described above, a reactive adhesive having the composition described in the columns of Examples 1 and 2 in Table 1 was applied by spin coating to give 50 μm.
An adhesive layer 4 having a thickness of m was formed (e). further,
The above steps were repeated to produce another substrate 3 coated with the adhesive layer 4.

Next, the ultraviolet ray irradiation device 20 was used to apply the adhesive layer 4 on the two substrates 3 to each other for 10 seconds at 100 m.
Ultraviolet irradiation was performed at an intensity of W / cm ² (f). Thereby, the tackiness of the adhesive surface is developed. The two substrates 3 irradiated with the above-mentioned ultraviolet rays are placed in an airtight container 21 to form an adhesive layer 4
Inside so that the gap 35 between the substrates 3 becomes 5 mm, and the pressure inside the closed container 21 is reduced to 20 mTorr to obtain a deoxidized atmosphere (g).

Thereafter, the adhesive layers 4 of the two substrates 3 were brought into contact with each other, and a pressure of 0.4 kg / cm ² was applied for 5 seconds to bond them (h). Finally, it was taken out from the container 21 to obtain an optical disc having two substrates 3 and an adhesive layer 2 (i).

(Examples 3 and 4) In this example, an adhesive having the composition shown in the columns of Examples 3 and 4 in Table 1 was used as an adhesive, and an optical disk was manufactured as follows. The manufacturing method is shown in FIG. In this embodiment, a replica substrate 1 made of an ultraviolet curable resin and a plastic plate is prepared, and the recording film 2 is formed of GeSbTe recording films 25 and Sb.
A Bi reflection film 26 and a three-layer film of the SiN protective film 15 were formed on the replica substrate 1 and adhered using the above adhesive to obtain an optical disc.

First, a Ni stamper 7 is prepared (a). The ultraviolet curable resin 22 is formed on the uneven surface of the stamper 7.
(Viscosity: 200 cp) was dropped, and a transparent and flat plastic plate 23 (outer shape: 300 mm, inner diameter: 35 mm, thickness: 1.1 mm) was used, and the film thickness of the ultraviolet curable resin 22 was 8
Push it to 0 μm. Next, by the ultraviolet irradiation device 20, from the plastic plate 23 side, 30 seconds, 1
Ultraviolet rays having an intensity of 00 mW / cm ² are irradiated to cure the ultraviolet curable resin 22 (b). When the stamper 7 and the ultraviolet curable resin 22 are separated from each other, the replica substrate 1 having the grooves and pits of the stamper 7 transferred thereon is obtained (c).

On the information pattern surface of the replica substrate 1,
GeSbTe recording film 25 (thickness: 30 nm), SbBi
A reflective film 26 (thickness: 20 nm) and a SiN protective film 15 (thickness: 30 nm) were sequentially formed by a sputtering method to produce a substrate 3 having a recording film 28 formed on the replica substrate 1 (d). .

On the recording film 2 of the substrate 3 produced as described above, a reactive adhesive having the composition described in the columns of Examples 3 and 4 in Table 1 was applied by spin coating to give 50 μm.
An adhesive layer 4 having a thickness of m was formed (e). further,
The above steps were repeated to produce another substrate 3 coated with the adhesive layer 4.

Next, by the ultraviolet irradiation device 20, the adhesive layers 4 on the two substrates 3 are each treated for 10 seconds at 100 m.
Ultraviolet irradiation was performed at an intensity of W / cm ² (f). Thereby, the tackiness of the adhesive surface is developed. The two substrates 3 irradiated with the above-mentioned ultraviolet rays are placed in an airtight container 21 to form an adhesive layer 4
Inside, and the gap 35 between the substrates 3 is made to face each other so as to be 5 mm, and the pressure inside the closed container 21 is reduced to 20 mTorr to obtain a deoxidized atmosphere (g).

After that, the adhesive layers 4 of the two substrates 3 were brought into contact with each other and bonded for 5 seconds under a pressure of 0.4 kg / cm ² (h). Finally, it was taken out from the container 21 to obtain an optical disc having two substrates 3 and an adhesive layer 2 (i).

(Examples 5 and 6) As the adhesive, adhesives having the formulations shown in the columns of Examples 5 and 6 in Table 1 were used.
An optical disc was manufactured as follows. Manufacturing method,
As shown in FIG. In this example, a replica substrate 1 made of a polycarbonate resin was prepared, and the recording film 2 was made of GeSbT.
The e recording film 25, the SbBi reflective film 26, and the SiN protective film 15 having three layers were formed on the replica substrate 1 and adhered using the above adhesive to obtain an optical disc.

First, a Ni stamper 7 is prepared (a). The stamper 7 is attached to a molding die 8 having an injection hole, and a polycarbonate resin 10 is placed in a gap 9 in the molding die 8.
(Molecular weight: about 15,000) is melted by heating and injected (b). The gap 9 has a disk shape with an outer diameter of 300 mm and a thickness of 1.2 mm, and has a central hole with an inner diameter of 35 mm at the center (that is, the molding die 8 has an outer diameter of 35 mm at the center). It has a cylindrical protrusion (not shown), and there is no gap in this part.) Next, the polycarbonate resin is cooled and cured, and the stamper 7 and the molding die 8 are removed, and the replica substrate 1 made of the polycarbonate resin (outer diameter:
(300 mm, central hole diameter: 35 mm, thickness: 1.2 mm)
Can be obtained (c).

On the information pattern surface of the replica substrate 1,
GeSbTe recording film 25 (thickness: 30 nm), SbBi
A reflective film 26 (thickness: 20 nm) and a SiN protective film 15 (thickness: 30 nm) were sequentially formed by a sputtering method to produce a substrate 3 having a recording film 28 formed on the replica substrate 1 (d). .

On the recording film 2 of the substrate 3 produced as described above, a reactive adhesive having the composition described in the columns of Examples 7 to 9 in Table 1 was applied by spin coating to give 50 μm.
An adhesive layer 4 having a thickness of m was formed (e). further,
The above steps were repeated to produce another substrate 3 coated with the adhesive layer 4.

Next, the ultraviolet irradiation device 20 was used to apply 100 m of adhesive to the adhesive layers 4 on the two substrates 3 for 10 seconds each.
Ultraviolet irradiation was performed at an intensity of W / cm ² (f). Thereby, the tackiness of the adhesive surface is developed. The two substrates 3 irradiated with the above-mentioned ultraviolet rays are placed in an airtight container 21 to form an adhesive layer 4
Inside so that the gap 35 between the substrates 3 becomes 5 mm, and the pressure inside the closed container 21 is reduced to 20 mTorr to obtain a deoxidized atmosphere (g).

After that, the adhesive layers 4 of the two substrates 3 were brought into contact with each other and a pressure of 0.4 kg / cm ² was applied for 5 seconds to bond them (h). Finally, it was taken out from the container 21 to obtain an optical disc having two substrates 3 and an adhesive layer 2 (i).

(Examples 7 and 8) In this example, an adhesive having the composition shown in the columns of Examples 7 and 8 in Table 1 was used as an adhesive to manufacture an optical disk as follows. The manufacturing method is shown in FIG. In this embodiment, a replica substrate 1 made of an ultraviolet curable resin and a plastic plate is prepared, and the recording film 2 is made of SiN enhance film 12, Tb.
FeCo magnetic film 13, AlN reflective film 14, and Si
4 layers of N protective film 15 are formed on the replica substrate 1,
An optical disk was obtained by bonding with the above adhesive.

First, a Ni stamper 7 is prepared (a). The ultraviolet curable resin 22 is formed on the uneven surface of the stamper 7.
(Viscosity: 200 cp) was dropped, and a transparent and flat plastic plate 23 (outer shape: 300 mm, inner diameter: 35 mm, thickness: 1.1 mm) was used, and the film thickness of the ultraviolet curable resin 22 was 8
Push it to 0 μm. Next, by the ultraviolet irradiation device 20, from the plastic plate 23 side, 30 seconds, 1
Ultraviolet rays having an intensity of 00 mW / cm ² are irradiated to cure the ultraviolet curable resin 22 (b). When the stamper 7 and the ultraviolet curable resin 22 are separated from each other, the replica substrate 1 having the grooves and pits of the stamper 7 transferred thereon is obtained (c).

Next, the SiN enhance film 12 (thickness: 30 n is formed on the information pattern surface of the obtained replica substrate 1.
m), TbFeCo magnetic film 13 (thickness: 30 nm), A
1N reflective film 14 (thickness: 30 nm), SiN protective film 15
(Thickness: 30 nm) are sequentially formed by a sputtering method,
Substrate 3 was obtained as recording film 2 (d).

On the recording film 2 of the substrate 3 produced as described above, a reactive adhesive having the composition described in the columns of Examples 1 and 2 in Table 1 was applied by spin coating to give 50 μm.
An adhesive layer 4 having a thickness of m was formed (e). further,
The above steps were repeated to produce another substrate 3 coated with the adhesive layer 4.

Next, by the ultraviolet irradiation device 20, the adhesive layers 4 on the two substrates 3 were each treated for 10 seconds at 100 m.
Ultraviolet irradiation was performed at an intensity of W / cm ² (f). Thereby, the tackiness of the adhesive surface is developed. The two substrates 3 irradiated with the above-mentioned ultraviolet rays are placed in an airtight container 21 to form an adhesive layer 4
Inside so that the gap 35 between the substrates 3 becomes 5 mm, and the pressure inside the closed container 21 is reduced to 20 mTorr to obtain a deoxidized atmosphere (g).

After that, the adhesive layers 4 of the two substrates 3 were brought into contact with each other, and a pressure of 0.4 kg / cm ² was applied for 5 seconds to bond them (h). Finally, it was taken out from the container 21 to obtain an optical disc having two substrates 3 and an adhesive layer 2 (i).

Next, for comparison with each of the above-mentioned examples, an optical disk was produced using an adhesive which cures in one step and an adhesive having a high compounding ratio of the epoxy adhesive. The mixing ratio of each adhesive and its characteristics in Comparative Examples 1 to 5 are shown in (Table 2) below. The unit of the mixing ratio described in (Table 2) is% by weight. Comparative Example 1
Also in Nos. 5 to 5, the curing agent was used as in Examples 1 to 8.

[0063]

[Table 2]

(Comparative Example 1) In this comparative example, an optical disk was prepared by the same manufacturing method as in Example 1 using the adhesive having the composition shown in the column of Comparative Example 1 in Table 2.

(Comparative Example 2) In this comparative example, an optical disk was prepared by the same manufacturing method as in Example 3 using the adhesive having the composition described in the column of Comparative Example 2 in Table 2.

(Comparative Examples 3 and 4) In this comparative example, an optical disk was prepared by the same manufacturing method as in Example 5 using the adhesives having the formulations shown in the columns of Comparative Examples 3 and 4 in Table 2, respectively. It was created.

(Comparative Example 2) In this comparative example, an optical disk was prepared by the same manufacturing method as in Example 3 using the adhesive having the composition described in the column of Comparative Example 5 in Table 2.

Further, in order to compare with Examples 1 to 11 using the chemical reaction type adhesive, an optical disk was produced using another type of adhesive. In Comparative Examples 6 to 9, the optical disc was manufactured by the same method as in Examples 1 and 2 (see FIG.
Prepare two substrates 3 (shown in FIG. 4D) on which the recording film 2 is formed, prepared by (d) and bond the two substrates using an adhesive. It was produced by. Table 3 shows the adhesives used in Comparative Examples 6 to 9 and their properties. All units are% by weight, except for the properties column.

[0069]

[Table 3]

(Comparative Example 6) In this comparative example, a hot-melt adhesive was applied to the recording film 2 of the two substrates 3 with a hot-melt coater so that the film thickness was 30 μm, and the adhesive-coated surface was Optical disks were produced by making them face-to-face and pasted together under a load of ² kg / cm ² .

(Comparative Example 7) In this comparative example, the one-part anaerobic curable adhesive was spin-coated on the recording film 2 of one of the two substrates 3 to form two substrates. 3 for recording film 2
Were opposed to each other and bonded under a reduced pressure of 20 mTorr to produce an optical disc.

(Comparative Example 8) In this comparative example, the above two substrates 3 were bonded together by using a two-liquid non-mixing adhesive composed of two agents A and B. Of the two substrates 3, the agent A is spin-coated on the recording film 2 of one of the substrates 3 and the agent B is spin-coated on the recording film 2 of the other substrate 3 to spin the two substrates 3 together. , Under a reduced pressure of 20 mTorr, and bonded to produce an optical disk.

(Comparative Example 9) In this comparative example, first, the above 2
The one-component moisture-curing adhesive was spin-coated on each of the recording films 2 of the substrates 3 and allowed to stand for 300 seconds to develop tackiness. After the surface of the adhesive layer became tacky and before the tackiness was lost, the surfaces were coated with the adhesive-coated surfaces facing each other to prepare an optical disk.

(Effects of Each Example) As described above, Examples 1 to 8 and Comparative Examples 1 to 12 bonded by using various adhesives.
For the optical disc of No. 3, the vertical deflection acceleration corresponding to the occurrence state of uneven defects after bonding, the tilt angle corresponding to the deformed state of the disk, the amount of substrate deviation after leaving at 80 ° C./1 h, and immediately after bonding (during manufacturing) Then, the presence or absence (visual observation) of defects such as irregularities and warpage on the disk surface after heat treatment (during use and storage) was examined. The measurement results for Examples 1-8 are shown in (Table 4), and the measurement results for Comparative Examples 1-9 are shown in (Table 5).

The measurement of these characteristics was performed as follows. Mechanical characteristics (vertical deflection acceleration and tilt angle)
Is an optical disc mechanical characteristic measuring device (laser wavelength: 780n
m, measurement rotation speed: 2400 rpm, measurement position: φ290
mm). The amount of deviation is the disk piece (film thickness:
A displacement amount was measured when a shear load of 500 g was applied to 30 μm and an adhesion area: 6 cm ² ). The presence or absence of defects by visual observation was determined by a device (shadow graph) that applies light to the object to be irradiated and magnifies and projects the reflected light. For example, when the surface of the optical disc is uneven or warped, the light and darkness of the light and the size of the projection are differently projected on the projection object.

[0076]

[Table 4]

[0077]

[Table 5]

In Examples 1 to 8, the adhesive applied to the substrate exhibits tackiness by ultraviolet irradiation which is performed before the bonding. Therefore, the adhesive layer becomes uniform, and the occurrence of uneven defects is extremely small. Therefore, as shown in (Table 4), the discs of Examples 1 to 8 have small vertical deflection acceleration. The vertical deflection acceleration is preferably 2 G or less, but all the optical discs of Examples 1 to 8 satisfy this criterion.

On the other hand, in Comparative Examples 2, 3, 5, 7, and 8, the adhesive layer could not be made tacky before the bonding. In Comparative Examples 2, 3, and 5, this is
This is because the compounding ratio of the epoxy adhesive in the adhesive is too large, and in Comparative Examples 7 and 8, the adhesive is liquid and its viscosity is poor. Therefore, the adhesive layer became non-uniform and uneven defects were generated, and the vertical deflection acceleration was large, and the above reference value could not be satisfied. Further, in Comparative Example 6 using the hot-melt adhesive, the adhesive layer had adhesiveness, but a defect occurred due to the pressure at the time of bonding, and the vertical deflection acceleration was large.

Furthermore, in Examples 1 to 8, since the adhesives including the slow-setting epoxy adhesives are used for adhesion,
There is time to allow bubbles mixed in the adhesive layer to escape. Therefore, the flatness of the disk is good and the tilt angle is small as shown in (Table 4). The tilt angle is preferably 5 mrad or less, but the optical disks of Examples 1 to 8
All meet this criterion.

On the other hand, in Comparative Example 4, since only the acrylic adhesive is used, the adhesive layer can be made to have tackiness, but the curing speed is fast, and the adhesive layer is cured with air bubbles mixed therein. Therefore, the inclination angle was large, and the above reference value could not be satisfied. Furthermore, in Comparative Example 6 (hot melt adhesive), Comparative Example 9 was used due to the pressure at the time of bonding.
With the (moisture-curing adhesive), it takes a long time for the adhesive to exhibit tackiness, and foreign matter or the like adheres to the adhesive during that time, resulting in deformation of the respective disks and a large tilt angle.

Further, since the epoxy resin is excellent in heat resistance, Examples 1 to 8 containing an epoxy adhesive in the adhesive were used.
Also has a small amount of deviation after heating (left at 80 ° C. for 1 hour).
The amount of deviation is preferably 20 μm or less, but Examples 1 to 8 all satisfy this criterion.

However, the monofunctional acrylic resin is weak against heat, and in Comparative Examples 1 and 4 in which only the acrylic adhesive is used, the amount of substrate displacement due to heating does not meet the target. Further, since the hot melt adhesive is softened by heat, the displacement amount becomes large in Comparative Example 6, which does not satisfy the target.

Next, the presence / absence of defects by visual observation will be described during disk manufacturing and after heat treatment. In each of Examples 1 to 8, no defects occurred during manufacturing and after heat treatment. This is because the deformation of the disk during production and the inclusion of bubbles and foreign matter were very small.

On the other hand, in Comparative Examples 2, 3, and 5 in which the compounding ratio of the epoxy adhesive in the adhesive was too high, and in Comparative Examples 7 and 8 in which the non-viscous liquid adhesive was used, the adhesive layer was formed. Due to lack of tackiness, the adhesive layer became non-uniform and defects were produced during manufacturing.

After heating (1 hour at 80 ° C.), defects were generated in all of Comparative Examples 1 to 9. This is because the monofunctional acrylic resin is vulnerable to heat (Comparative Examples 1 and 4), and the adhesive layer becomes non-uniform due to lack of tackiness, which causes warpage and unevenness during heating (Comparative Example 2,
3, 7 and 8), the hot melt adhesive is softened by heat (Comparative Example 6), and the time until adhesiveness develops is too long, so that foreign matter is mixed in and causes warpage or unevenness during heating. (Comparative Example 9) and the like are conceivable.

Further, with respect to the optical disks of Examples 1 to 8, recording was performed at a disk rotation speed of 2400 rpm by a recording / reproducing apparatus (optical head using a condensing lens having a numerical aperture of 0.55 with a laser of 680 nm as a light source). As a result of the reproduction, no recording / reproduction failure occurred.

From the above results, the optimum range of the acrylic adhesive and the epoxy adhesive is the acrylic adhesive 95-75.
%, The epoxy adhesive is 5 to 25%.
The optical discs produced by using the adhesives in the optimum range according to each of Examples 1 to 8 were excellent in flatness and highly precise with little unevenness or deformation even in a heating atmosphere.

[0089]

According to the present invention, it is possible to realize an optical disc having high precision and high reliability by reducing high-speed access, deformation due to high-speed rotation, deformation and peeling due to aging during storage, and a manufacturing method thereof. be able to.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an optical disc.

FIG. 2 is a sectional view of an optical disc.

FIG. 3 is an explanatory diagram showing a stamper manufacturing process.

FIG. 4 is a polycarbonate resin replica substrate and 4
FIG. 6 is an explanatory view showing a manufacturing process of an optical disc having a recording film of layers.

FIG. 5 is an explanatory diagram showing a manufacturing process of an optical disc having a replica substrate made of an ultraviolet curable resin and a plastic plate, and a three-layer recording film.

FIG. 6 is a polycarbonate resin replica substrate and 3
FIG. 6 is an explanatory view showing a manufacturing process of an optical disc having a recording film of layers.

FIG. 7 is an explanatory diagram showing a manufacturing process of an optical disc having a replica substrate made of an ultraviolet curable resin and a plastic plate and four recording films.

[Explanation of symbols]

1 ... Replica substrate, 2 ... Recording metal film, 3 ... Substrate,
4 ... Adhesive layer, 5 ... Ni film, 6 ... Ni electroformed film, 7
... Stamper, 8 ... Mold, 9 ... Mold gap, 1
0 ... Polycarbonate resin, 12 ... SiN enhance film, 13 ... TbFeCo magnetic film, 14 ... AlN reflective film, 15 ... SiN protective film, 16 ... Photoresist film, 17 ... Glass disk, 18 ... Reduced pressure, 20 ... UV irradiation device, 21 ... Airtight container, 22 ... UV curable resin, 23 ... Plastic plate, 25 ... GeSbTe recording film, 26 ... SbBi reflective film, 27 ... SiN protective film, 34 ... Hole in the center of optical disc, 35 ... Substrate gap.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuo Tajima 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa, Ltd. Inside the Hitachi, Ltd. Institute of Industrial Science (72) Inventor Toshiaki Taii 1-1, Tora, Ibaraki-shi, Osaka No. 88 in Hitachi Maxell Co., Ltd.

Claims (4)

[Claims] 1. A pair of opposed substrates, and an adhesive layer,
At least one of the substrates has a recording film, and the adhesive layer is an optical disc arranged in a gap between the pair of opposed substrates. The adhesive layer comprises an ultraviolet curable monofunctional acrylic resin and an ultraviolet curable epoxy. When the total amount of the UV-curable monofunctional acrylic resin and the UV-curable epoxy resin is 100%, the compounding amount of the UV-curable monofunctional acrylic resin is 95.
Is 75%, and the compounding amount of the above ultraviolet curable epoxy resin is 5 to 25%.
An optical disc characterized by: 2. An adhesive applying step of applying an adhesive to two transparent substrates having a recording layer formed on at least one side to form an adhesive layer, and the above two sheets so that the adhesive layers are on the inner side. In the optical disc manufacturing method, which comprises a transparent substrate facing and pressurizing and adhering the transparent substrate, the adhesive contains an ultraviolet curable acrylic adhesive and an ultraviolet curable epoxy adhesive, and the ultraviolet curable acrylic adhesive is used. When the compounding amount of the agent and the ultraviolet curable epoxy adhesive is 100% in total, the compounding amount of the ultraviolet curable acrylic adhesive is 95 to 7
It is 5%, and the compounding amount of the ultraviolet curing epoxy adhesive is 5 to 25
%, The optical disk manufacturing method. 3. The optical disc manufacturing method according to claim 2, further comprising an ultraviolet irradiation step of irradiating the adhesive layer with ultraviolet rays between the adhesive applying step and the adhering step. 4. The method of manufacturing an optical disc according to claim 2, wherein the bonding step is performed in a reduced pressure atmosphere.