JPH10102007A - Adhesive for adhering optical disk substrate and production of optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an adhesive for adhering optical disk substrates without causing deformation or erosion of the optical disk substrate, having a very strong adhesive strength and showing an excellent durability and reliability for a long period by including a polymerizable unsaturated compound and a specific visual light-polymerization initator. SOLUTION: This adhesive for adhering an optical disk substrate comprises (A) a polymerizable unsaturated compound [preferably an unsaturated compound having an alicyclic substituting group such as dimethyloldicyclopentadienylene di(meth)acrylate] and (B) a bisacylphosphine oxide compound of formula I (R1 to R3 are each an alkyl, aryl, etc.) and/or an acylphosphine oxide compound of formula II (R4 to R6 are each R1 ) which are a photopolymerization initiator, preferably in 1-10 pts.wt. component B based on 100 pts.wt. component A. The component B is preferably bis(2,6-dimethoxybenzoyl)-2,4,4- trimethylpentylphosphine oxide. An unsaturated compound having phosphoric acid group is preferably blended therewith for improving adhesion to aluminium- deposited surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an adhesive for bonding an optical disk substrate and a method for manufacturing a bonded optical disk. More specifically, the present invention is capable of bonding two opaque optical disk substrates in a short time using photo-curing, and the bonded optical disk has a sufficient adhesive strength for a long time, especially for a digital video disk. The present invention relates to a method for manufacturing an optical disk suitable for a method for manufacturing an optical disk (hereinafter referred to as a DVD).

[0002]

2. Description of the Related Art An optical disk useful as a high-density, high-precision recording medium has an optical recording layer formed on a substrate, and this optical recording layer is irradiated with a laser beam or the like to record and reproduce information. It is. Generally, this optical disk employs a structure in which a protective plate is attached to an optical disk substrate having a recording layer formed on a substrate such as glass or plastic, or the optical disk substrates are bonded to each other.

According to the electronic technology, August 1996, p-52 and Nikkei Science September 1996, p-28, a DVD which has been attracting attention as a recording medium for high-capacity and high-quality digital images is a conventional compact disk. (Hereinafter CD)
Track pitch and shortest pit length less than half,
A single plate with a diameter of 12 cm achieves a high capacity of 4.7 GB. In the case of a two-layer double-sided DVD optical disc, the thickness is 0.
The recording capacity is 9.4 because two 6 mm single plates are bonded together.
G bytes.

According to the electronic technology, July 1995, the following SD (Super Densit) is used depending on the reading method.
y Disc) standard, each of which is S
D-5, double-sided reading SD-10, single-sided double-layer reading SD-9, double-sided double-layer reading SD-18, additional recording type SD-R, and rewritable SD-RAM.

[0005] Among them, DVDs classified as SD-5 can be manufactured by forming a reflective layer of a metal such as aluminum on the surface on which the recording layer is formed, and attaching a protective plate to the surface. DVD classified as SD-9 is Natio
nal Technical Report Vol.41 No.6 p-608-621 Dec.199
According to 5, it can be manufactured by bonding a substrate having a translucent layer formed of various metals or dielectric materials on a recording layer surface and a substrate having a reflective layer formed on a recording surface with both signal surfaces facing each other. . DVDs classified as SD-10 can be manufactured by bonding two substrates each having a reflective film formed on the recording surface such that the reflective films are both on the inside.

Conventionally, this bonding is performed by a method of bonding with an epoxy adhesive or the like, or applying a hot-melt adhesive on a single-plate disk and stacking another single-plate disk coated with the hot-melt adhesive. A method of bonding by air spray or the like, a method of bonding by double-sided adhesive tape, and the like are used.

[0007] However, the method using an epoxy-based adhesive requires the operation of evaluating and mixing two liquids in the case of two liquids, resulting in a complicated process and a problem of pot life.
Further, when the material is cured by heating, the productivity is extremely low, such as using a member fixing jig for a long time, and the substrate may be deformed because the curing method is heating.

In the bonding method using a hot-melt adhesive, the pressure-sensitive adhesive must be melted by heat. If the melting temperature is high, the substrate may be deformed. There are drawbacks, such as difficulty in handling, and an unnecessarily thick coating.

Further, in the bonding method using a double-sided tape, the double-sided tape is cut into a substrate shape, the release paper on one side is peeled off, and the release paper on one side is attached to one substrate, and then the other release paper on the tape is peeled off. After that, the other substrate is attached, which is a method with a very large number of steps and extremely difficult to automate.

In order to solve these problems, Japanese Patent Application Laid-Open Nos. Hei 5-194929, Hei 2-195541 and Hei 5
As shown in JP-67361, development of an ultraviolet (UV) curing adhesive that imparts photocurability to an adhesive, has high adhesive strength, and has small distortion at the time of bonding is progressing. As the ultraviolet light polymerization initiator that can be used for the ultraviolet curable adhesive, conventionally known ones such as carbonyl-based, azo-based, diazo-based, and halide-based ones can be used alone or in combination.

However, an opaque optical disk substrate provided with a reflective film layer such as an aluminum vapor-deposited film generally has a thickness of 300 nm.
The transmittance of light around m was extremely small, and these conventional ultraviolet light initiators could not be sufficiently decomposed via the reflective film layer. Therefore, since none of them has sufficient adhesive strength, it has been impossible to obtain a bonded optical disk free from malfunctions such as focus errors and track errors for a long period of time. Further, there are many polymerization initiators which erode the plastic material such as polycarbonate which is the optical disk substrate or the aluminum vapor deposition layer, and there is a practical problem.

In recent years, Japanese Patent Application Laid-Open No. Hei 8-167172 discloses a method for manufacturing an optical disk by bonding a transparent substrate and a hub with a photocurable resin. However, in this method, it is essential that one of the substrates is transparent, and it cannot be applied to bonding of opaque optical disk substrates provided with a metal vapor-deposited film of aluminum or the like on the optical disk substrate.

[0013]

SUMMARY OF THE INVENTION The present invention relates to a method for manufacturing a single-sided double-layer optical disk or a double-sided optical disk by bonding two opaque optical disk substrates provided with a reflective film layer such as an aluminum vapor-deposited film. It is to solve such problems.

That is, an object of the present invention is to provide an optical disk substrate without deformation and erosion without requiring a complicated process in a short time, obtain an extremely strong adhesive force, and have excellent durability and reliability over a long period of time. It is an object of the present invention to provide an adhesive composition for bonding an optical disk substrate, and a method for manufacturing an optical disk using the adhesive.

[0015]

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that an ultraviolet light polymerization initiator used in an adhesive for bonding an optical disk substrate has been used conventionally. Instead, the present inventors have found that the above problem can be solved by using a visible light polymerization initiator having a specific structure and having absorption in a longer wavelength region, and have completed the present invention.

That is, according to the present invention, a polymerizable unsaturated compound and a photo-polymerization initiator, that is, a bisacylphosphine oxide compound of the general formula (1) and / or an acylphosphine oxide compound of the general formula (2) are contained. Characteristic adhesive composition for bonding optical disk substrates

General formula (1);

Embedded image (Wherein, R _{1 to} R ₃ each independently represent an alkyl group, an aryl group, an allyl group, an aralkyl group, an alkenyl group, an alkynyl group, a heterocyclic group, a substituted alkyl group, a substituted aryl group, a substituted allyl group, a substituted aralkyl Group, substituted alkenyl group, substituted alkynyl group or substituted heterocyclic group) General formula (2);

Embedded image (Wherein, R _{4 to} R ₆ each independently represent an alkyl group, an aryl group, an allyl group, an aralkyl group, an alkenyl group, an alkynyl group, a heterocyclic group, a substituted alkyl group, a substituted aryl group, a substituted allyl group, a substituted aralkyl Group, substituted alkenyl group, substituted alkynyl group or substituted heterocyclic group)

The above-mentioned adhesive composition is applied to one or both surfaces of two optical disk substrates to be bonded and then bonded together, and light containing the absorption wavelength of the photopolymerization initiator is applied to one surface of the two optical disk substrates. Alternatively, the above object has been solved by developing a method of manufacturing an optical disk by bonding optical disk substrates, which is characterized in that both surfaces are irradiated and cured.

The present invention is characterized in that a bisacylphosphine oxide compound represented by the general formula (1) and / or an acyl compound represented by the general formula (2) is used as a photopolymerization initiator of the adhesive composition for bonding an optical disk substrate. Use of a phosphine oxide compound may be mentioned.

Since these initiators are more sensitive to a longer wavelength region (visible light region of 400 nm or more) than a conventional ultraviolet polymerization initiator, they are transmitted through a reflective film layer such as an aluminum vapor-deposited film on an optical disk substrate. It can be efficiently decomposed by the obtained irradiation light. Further, it is said that the polymerization initiation efficiency is higher than that of a conventional ultraviolet light polymerization initiator since the compound is cleaved by light irradiation to generate an acyl radical and a phosphinoyl radical.

An example of using a (bis) acylphosphine compound as a photopolymerization initiator is disclosed in JP-A-61-1302.
No. 96, JP-A-2-1401, etc., JP-A-4-18091
No. 1, JP-A-8-167172. However, all of them are only applied to the composition for dental materials or light curing of lenses, prisms and the like, and one of the lamination of optical disk substrates is only applied to a transparent substrate.

Specific examples of the bisacylphosphine oxide compound of the general formula (1) used in the present invention include bis (2,6-dichlorobenzoyl) -phenylphosphine oxide and bis (2,6-dichlorobenzoyl). −
2,5-dimethylphenylphosphine oxide, bis (2,6-dichlorobenzoyl) -4-ethoxyphenylphosphine oxide, bis (2,6-dichlorobenzoyl) -4-biphenylylphosphine oxide, bis (2,6 -Dichlorobenzoyl) -4-propylphenylphosphine oxide, bis (2,6-dichlorobenzoyl) -2-naphthylphosphine oxide, bis (2,6-dichlorobenzoyl) -1-naphthylphosphine oxide, bis (2 , 6-Dichlorobenzoyl)
-4-chlorophenylphosphine oxide, bis (2,6-dichlorobenzoyl) -2,4-dimethoxyphenylphosphine oxide, bis (2,6-dichlorobenzoyl) -decylphosphine oxide, bis (2,6-di Chlorobenzoyl) -4-octylphenylphosphine oxide, bis (2,6-dichlorobenzoyl) -2,5-dimethylphenylphosphine oxide, bis (2,6-dichlorobenzoyl) -phenylphosphine oxide, bis (2 4,6-trimethylbenzoyl) -2,5-dimethylphenylphosphine oxide, bis (2,6-dichloro-3,4,5-trimethoxybenzoyl) -2,5-dimethylphenylphosphine oxide, bis (2,6 -Dichlor-3,4
5-trimethoxybenzoyl) -4-ethoxyphenylphosphine oxide, bis (2-methyl-1-naphthoyl) -2,5-dimethylphenylphosphine oxide, bis (2-methyl-1-naphthoyl) -2,5-phenyl Phosphine oxide, bis (2-methyl-1-
Naphthoyl) -4-biphenylylphosphine oxide, bis (2-methyl-1-naphthoyl) -4-ethoxyphenylphosphine oxide, bis (2-methyl-
1-naphthoyl) -2-naphthylphosphine oxide, bis (2-methyl-1-naphthoyl) -4-propylphenylphosphine oxide, bis (2-methoxy-1-naphthoyl) -2,5-dimethylphenylphosphine oxide, bis (2-methoxy-1-naphthoyl) -4-ethoxyphenylphosphine oxide, bis (2-methoxy-1-naphthoyl) -4-biphenylylphosphine oxide, bis (2-chloro-1-naphthoyl) -2,5- Dimethylphenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,
4,4-trimethylpentylphosphine oxide and the like can be mentioned.

Specific examples of the acylphosphine oxide compound of the general formula (2) include 2,4,6-trimethylbenzoyldiphenylphosphine oxide, p-
Toluyl-diphenylphosphine oxide, 4-t-
Butylbenzoyldiphenylphosphine oxide, 1
-Methylcyclohexanoyl-diphenylphosphine oxide and the like. Among them, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide and 2,4,6-trimethylbenzoyldiphenylphosphine oxide are preferable, and bis (2,6-dimethoxybenzoyl) -2, 4,4-trimethylpentylphosphine oxide is most preferred.

These initiators are added at a ratio of 0.01 to 50.0 parts by weight based on 100 parts by weight of the total polymerizable unsaturated compound. Preferably 0.1 to 20.0 parts by weight,
More preferably, it is 1.0 to 10.0 parts by weight. When the amount of these initiators added is 100% of the total amount of the polymerizable unsaturated compound,
If the amount is less than 0.01 parts by weight, the curing does not proceed sufficiently, and the adhesive strength may be insufficient. When the amount of the initiator is more than 50.0 parts by weight based on 100 parts by weight of the total amount of the polymerizable unsaturated compound, the radical generation amount becomes extremely large, and the molecular weight of the resin of the adhesive layer becomes small. In addition, the adhesive strength may be insufficient.

These polymerization initiators may be used alone or in combination of two or more.

The method for synthesizing the (bis) acylphosphine oxide compound is described in JP-A-61-130296 and JP-A-55-130296.
No. 13794 and the like. For further details, see JP-B-60-8047 and JP-A-61-1302.
No. 96, JP-A-6-298818, JP-A-7-620
No. 10, etc.

The polymerizable unsaturated compound used in the present invention is a compound having a radical polymerizable unsaturated group,
There are no particular restrictions on monomers, oligomers, and resins having a (meth) acrylic group, a vinyl group, an allyl group, etc., but a compound having a small volumetric shrinkage upon curing to enhance adhesion to a substrate after curing. It is preferable to use Specifically, the volume shrinkage of the entire polymerizable unsaturated compound upon curing is 15% or less, more preferably 10% or less. The volume shrinkage at the time of curing is described in p-1 to 41 of "Refinement of Thermosetting Polymer (CMC Publishing Co., Ltd., 1986)".

Examples of the compound having a small volume shrinkage upon curing include an unsaturated compound having a bulky cyclic substituent in the molecule. Examples of the cyclic substituent include aromatic substituents such as phenyl, naphthyl, and pyridyl, and cycloaliphatic substituents such as cyclohexyl, isobornyl, and dicyclopentadienyl group. Unsaturated compounds are particularly preferred.

Specific examples include dimethylol dicyclopentadienylene di (meth) acrylate, isobornyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate and the like.

Examples of the polymerizable unsaturated monomer other than the low-shrinkable unsaturated compound include aromatic monomers such as styrene, α-methylstyrene, p-methylstyrene, and chlorostyrene, methyl methacrylate, and isobutyl (meth) acrylate. (Meth) acrylate monomers such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and polyoxyethylene (meth) acrylate; N, N-dimethylacrylamide; N, N-diethylacrylamide; N-substituted acrylamides such as acryloylmorpholine and the like. The polymerizable unsaturated oligomers and resins used in the present invention include unsaturated polyester resins, vinyl ester resins, and curable (meth) acrylic resins.

As the unsaturated polyester, a generally known product obtained by reacting an acid or its anhydride with an alcohol by a known method is used.

The vinyl ester resin is manufactured by a known method, and is obtained by reacting an epoxy resin with (meth) acrylic acid.
Polyester (meta) obtained by reacting an acrylate or a polyester having a terminal carboxyl group obtained from a saturated dicarboxylic acid and / or unsaturated dicarboxylic acid and a polyhydric alcohol with an epoxy compound containing an α, β-unsaturated carboxylic ester group A) acrylate and the like.

The curable (meth) acrylic resin is, specifically, 1,4-butanediol dimethacrylate,
Urethane acrylate formed by the reaction of a (meth) acrylate such as 1,6-hexanediol dimethacrylate, trimethylolpropane triacrylate, pentaerythritol trimethacrylate, pentaerythritol tetraacrylate, or a hydroxyalkyl (meth) acrylate with a compound having an isocyanate group. And the like.

Further, as the polymerizable unsaturated compound of the present invention,
In order to increase the adhesion to the aluminum deposition surface, it is preferable that a small amount of a phosphoric acid group-containing unsaturated compound is present. Specific examples include phosphoric acid esters of 2-hydroxyethyl (meth) acrylate and phosphoric acid esters of 2-hydroxyethyl (meth) acrylate modified with caprolactone, and commercially available products are easily available. The amount of addition is in the range of 0.01 to 10 parts by weight, preferably in the range of 0.1 to 5 parts by weight. When the amount of the phosphoric acid group-containing unsaturated compound is 0.01 parts by weight or less, the effect is not recognized. When the amount is 10 parts by weight or more, the substrate or the aluminum deposition surface may be eroded.

Further, the composition of the present invention may be blended with various polymerization accelerators and the like for the purpose of promoting the curing reaction efficiently and for obtaining the desired adhesive strength by post-curing after the end of light irradiation. . Examples of the polymerization accelerator include other photopolymerization initiators, thermal polymerization initiators, and redox polymerization initiators.

A thermal polymerization initiator can be added to the composition of the present invention. Specifically, various peroxides such as t-butylperoxypivalate and lauroyl peroxide, and azobisisobutyronitrile and the like can be used. And lipophilic azobis compounds.

The composition of the present invention may further contain a leveling agent, a plasticizer, an antifoaming agent, a thickener, a polymerization inhibitor, an antioxidant, etc., which are generally used as paint additives. It can be added to such an extent that the adhesive strength between the two bonded optical disk substrates is not impaired.

The adhesive composition of the present invention can be diluted with a solvent or the like to reduce the viscosity before use. The solvent may be a commercially available solvent, but a solvent that corrodes or whitens the reflective film or the optical disk substrate cannot be used.

The method of bonding two optical disk substrates by light curing according to the present invention is generally performed in the following procedure. In the DVD classified as SD-5, first, one of the optical disk substrates is vacuum-adsorbed and fixed on a rotary table with the metal deposition surface facing upward, and the adhesive composition of the present invention is dropped while rotating at a low speed. Next, the adhesive composition is spread by laminating substrates serving as protective plates and rotating the substrates at a high speed. DVDs classified as SD-9 are fixed by vacuum suction on a rotary table with the translucent layer facing upward, and the adhesive composition of the present invention is dropped while rotating at a low speed. Next, a substrate having a recording layer and a reflective layer formed thereon is overlapped with both signal surfaces facing each other, and rotated at a high speed to spread the adhesive composition. For DVDs classified as SD-10, one of the optical disk substrates is vacuum-adsorbed and fixed on a rotary table with the metal-deposited surface facing upward, and the adhesive composition of the present invention is dropped while rotating at a low speed. Next, the other optical disk substrate is superposed from above with the signal side of the metal-deposited surface facing down, and is rotated at a high speed to spread the adhesive composition.

When rotated at a high speed in this manner, the excess adhesive composition is discharged from the outer peripheral edge of the substrate and held between two optical disk substrates on which only a necessary amount of adhesive is bonded.
Thereafter, the two optical disc substrates are fixed to a jig so as not to be displaced, and are used in the present invention on at least one surface to the surface on a device such as a belt conveyor.
By irradiating light containing the absorption wavelength of the acylphosphine oxide compound and the added other photopolymerization initiator, the polymerizable unsaturated compound is cured to form an intermediate layer, and the laminated optical disk is obtained.

As another method, one of the optical disk substrates to be bonded is vacuum-adsorbed and fixed on a rotary table, and the adhesive composition of the present invention is dropped while not rotating or rotating at a low speed. Next, the adhesive is spread by rotating at a high speed, excess adhesive composition is removed from the outer peripheral edge of the substrate, and the other optical disk substrate is overlaid from above. Thereafter, an optical disk bonded through a curing step by light irradiation similar to the above method is obtained.

The method of applying the adhesive composition is not limited to the above method, and the adhesive intermediate layer having an arbitrary thickness may be formed by using a known means such as hand, spatula, roll coat, or spray.

The light irradiation may be any light source having a spectral distribution in the photosensitive wavelength region of the initiator in the composition and capable of irradiating light with an intensity capable of causing a photoreaction.
Xenon lamps, mercury lamps, metal halide lamps,
Sunlight or the like is used. Two or more light sources can be used in combination to match the photosensitive wavelength of the photoinitiator. The light intensity required for the method for producing a bonded optical disk of the present invention varies depending on the photosensitivity (photosensitivity) of the initiator, the curability and the amount of the polymerizable compound, and is generally 10 mJ / cm.
The light intensity is ² or more, preferably 100 mJ / cm ² or more. If the light intensity is too low, the photoreaction does not proceed sufficiently, and the adhesive strength may be insufficient. If the light intensity is excessive, deformation such as warpage of the optical disk occurs, which is not preferable.

Regarding the wavelength of light, there is a problem in safety with only light having a wavelength shorter than 400 nm, and curing in the depth direction may be uneven.

In order to accelerate the polymerization reaction, the bonding step may be performed by heating the optical disk substrate to such an extent that the optical disk substrate is not deformed such as warpage. In general, it is preferable to irradiate light having a spectrum in an infrared region, such as a halogen lamp, because the temperature of an object to be irradiated increases due to the action of heat rays and the curing reaction is accelerated.

[0046]

The present invention will be described below with reference to examples. However, the present invention is not limited to the following examples. In the following description, “parts” means parts by weight unless otherwise specified.

Example 1 120 mm in diameter and 1.2 in thickness
The adhesive composition having the following composition 1 (volume shrinkage ratio: 6.5%) is uniformly applied to the aluminum-deposited surface side of a polycarbonate substrate for DVD having a thickness of 2 mm, and the aluminum-deposited surface of the other optical disk substrate is adhered to 2 kg. / Cm ² was applied. Conveyor type metal halide lamp (irradiation energy 1J / cm ² ) Irradiation height 10c
Irradiation was performed at a speed of 1.4 m / min to form an adhesive layer between the two DVDs, thereby obtaining a bonded double-sided DVD. Composition 1 Light acrylate DCP-A * 100 parts Bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide 3 parts * Light acrylate DCP-A is dimethylol dicyclopent manufactured by Kyoeisha Chemical Co., Ltd. It is a trade name of Tadienylene acrylate. When the bonding surface thus formed was put into a constant temperature / humidity bath at 80 ° C. and 90% relative humidity for 7 days and observed, no peeling was observed at the end, and it was confirmed that the bonding was sufficient. all right.

(Example 2) A test was conducted in exactly the same manner as in Example 1 except that the adhesive composition of the following composition 2 (volume shrinkage 7%) was used instead of the composition 1. Composition 2 Light acrylate DCP-A 100 parts Kayamer PM2 * 0.5 part Bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide 3 parts * Kayamer PM2 is a phosphorus compound manufactured by Nippon Kayaku Co., Ltd. It is a trade name of an acid group-containing polymerizable unsaturated compound. When the bonding surface similarly formed was put in a constant temperature and humidity chamber of 80 ° C. and 90% relative humidity for 7 days and observed, no peeling was observed at the end portion, and it was found that sufficient bonding was achieved. .

Example 3 A test was conducted in exactly the same manner as in Example 1 except that the adhesive composition of the following composition 3 (volume shrinkage 6.5%) was used in place of the composition 1. Composition 3 Light acrylate DCP-A 100 parts 2,4,6-Trimethylbenzoyl-diphenylphosphine oxide 3 parts The same bonding surface was placed in a constant temperature and humidity chamber at 80 ° C. and 90% relative humidity for 7 days and observed. However, no peeling was observed at the end, and it was found that sufficient adhesion was achieved.

Example 4 A test was performed in exactly the same manner as in Example 1 except that the adhesive composition of the following composition 4 (volume shrinkage 7%) was used instead of the composition 1. Composition 4 Light acrylate DCP-A 100 parts Kayamar PM2 0.5 parts 2,4,6-trimethylbenzoyl-diphenylphosphine oxide 3 parts The same bonding surface was placed in a thermo-hygrostat at 80 ° C. and 90% relative humidity. After observation for a period of one day, no exfoliation was observed at the edges, indicating that sufficient adhesion was achieved.

Example 5 A test was performed in exactly the same manner as in Example 1 except that the adhesive composition of the following composition 5 (volume shrinkage 9%) was used in place of the composition 1. Composition 5 Light acrylate DCP-A 50 parts EB-810 * 50 parts Kayamar PM2 0.5 parts Bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide 3 parts * EB-810 is Daicel When the joint surface made in the same manner as polyester acrylate manufactured by UCB was placed in a thermo-hygrostat at 80 ° C. and 90% relative humidity for 7 days and observed, no peeling was seen at the ends, and sufficient adhesion was obtained. I knew it was there.

(Example 6) A test was conducted in exactly the same manner as in Example 1 except that the adhesive composition of the following composition 6 (volume shrinkage 8%) was used instead of the composition 1. Composition 6 Light acrylate DCP-A 50 parts EB-3701 * 50 parts Kayamar PM2 0.5 parts 2,4,6-trimethylbenzoyl-diphenylphosphine oxide 3 parts * EB-3701 is a product name of epoxy acrylate manufactured by Daicel UCB It is. When the bonding surface similarly formed was put in a constant temperature and humidity chamber of 80 ° C. and 90% relative humidity for 7 days and observed, no peeling was observed at the end portion, and it was found that sufficient bonding was achieved. .

Example 7 A test was conducted in exactly the same manner as in Example 1 except that the adhesive composition of the following composition 7 (volume shrinkage 7%) was used instead of the composition 1. Composition 7 Light acrylate DCP-A 100 parts Kayamer PM2 0.5 parts Bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide 2 parts 2,4,6-trimethylbenzoyl-diphenylphosphine oxide 2 Part When the joint surface formed in the same manner was placed in a constant temperature / humidity chamber at 80 ° C. and 90% relative humidity for 7 days and observed, no peeling was observed at the end, and it was found that sufficient bonding was achieved. Was.

(Comparative Example 1) Diameter 120 mm, thickness 1.2
mm DVD polycarbonate substrate on the aluminum deposition side of Cemedine HM408 (manufactured by Cemedine Co., Ltd.)
A hot-melt adhesive for an optical disk) was uniformly applied, and the other optical disk substrate was similarly applied, and the bonding surfaces were adhered to each other and joined by applying a pressure of ² kg / cm ² . When the bonding surface thus formed was placed in a constant temperature and humidity chamber at 80 ° C. and 90% relative humidity for 7 days and observed, peeling was observed from the end.

(Comparative Example 2) A test was conducted in exactly the same manner except that the adhesive composition of the following composition 8 was used instead of the composition 1 of the example 1. Composition 8 Light acrylate DCP-A 100 parts Irgacure 500 (manufactured by Ciba Geigy) 3 parts The adhesive layer thus formed is semi-cured, the adhesive surface is easily peeled off, and the strength is completely insufficient. Was.

(Comparative Example 3) A test was carried out in exactly the same manner as in Example 1 except that the adhesive composition of the following composition 9 was used instead of the composition 1 of Example 1. Composition 9 Light acrylate DCP-A 100 parts Kayamar PM2 0.5 parts Irgacure 500 3 parts The adhesive layer thus formed is semi-cured, the adhesive surface is easily peeled off, and the strength is completely insufficient. I was

(Comparative Example 4) A test was carried out in exactly the same manner as in Example 1 except that the adhesive composition of the following composition 10 was used instead of the composition 1 of Example 1. Composition 10 Light acrylate DCP-A 100 parts Darocure 1173 (manufactured by Ciba Geigy) 3 parts The adhesive layer thus formed was semi-cured, the adhesive surface was easily peeled off, and the strength was completely insufficient. .

(Comparative Example 5) A test was carried out in exactly the same manner as in Example 1 except that the adhesive composition of the following composition 11 was used instead of the composition 1 of Example 1. Composition 11 Light acrylate DCP-A 100 parts Kayamar PM2 0.5 part Darocure 1173 3 parts The adhesive layer thus formed is semi-cured, the adhesive surface is easily peeled off, and the strength is completely lacking. Was.

[0059]

According to the present invention, an adhesive composition for bonding an optical disc substrate comprising a polymerizable compound containing a polymerizable unsaturated compound having low shrinkage and a specific photopolymerization initiator can be used in a short time. Adhesive composition for the production of bonded optical discs, which does not require complicated processes, does not deform the optical disc substrate, and obtains extremely strong adhesive force and has excellent durability and reliability over a long period of time, and the same. A manufacturing method has been provided.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kazuhiko Oga 1-1-1 Ohnodai, Midori-ku, Chiba-shi, Chiba Pref. Showa Denko KK

Claims (5)

[Claims] 1. A polymerizable unsaturated compound comprising a bisacylphosphine oxide compound represented by the general formula (1) and / or an acylphosphine oxide compound represented by the general formula (2), which is a photopolymerization initiator. An adhesive composition for bonding an optical disk substrate, characterized by comprising: General formula (1); (Wherein, R _{1 to} R ₃ each independently represent an alkyl group, an aryl group, an allyl group, an aralkyl group, an alkenyl group, an alkynyl group, a heterocyclic group, a substituted alkyl group, a substituted aryl group, a substituted allyl group, a substituted aralkyl Group, a substituted alkenyl group, a substituted alkynyl group, or a substituted heterocyclic group) General formula (2); (Wherein, R _{4 to} R ₆ each independently represent an alkyl group, an aryl group, an allyl group, an aralkyl group, an alkenyl group, an alkynyl group, a heterocyclic group, a substituted alkyl group, a substituted aryl group, a substituted allyl group, a substituted aralkyl Group, substituted alkenyl group, substituted alkynyl group or substituted heterocyclic group) 2. A polymerizable unsaturated compound, a bisacylphosphine oxide compound represented by the general formula (1) and / or an acylphosphine oxide compound represented by the general formula (2), which is a photopolymerization initiator, and phosphorus 2. The adhesive composition for bonding optical disc substrates according to claim 1, further comprising an acid group-containing unsaturated compound. 3. The polymerizable unsaturated compound having a volume shrinkage of 10
%. The adhesive composition for bonding an optical disc substrate according to claim 1, wherein the content is less than 3%. 4. The content of a phosphate group-containing unsaturated compound is as follows:
The adhesive composition for bonding an optical disc substrate according to claim 2, wherein the adhesive composition is 0.01 to 10% by weight of the whole composition. 5. The adhesive composition according to claim 1, which is applied to at least one of two optical disk substrates to be bonded, and after superimposition, light containing an absorption wavelength of a photopolymerization initiator is applied to the optical disk substrate. A method for manufacturing an optical disk, wherein the adhesive is cured by irradiation from one or both sides.