WO2012147712A1

WO2012147712A1 - Curable composition and adhesive for optical applications

Info

Publication number: WO2012147712A1
Application number: PCT/JP2012/060903
Authority: WO
Inventors: 岡崎　仁; 康佑並木; 竹内　基晴
Original assignee: 三菱瓦斯化学株式会社
Priority date: 2011-04-28
Filing date: 2012-04-24
Publication date: 2012-11-01
Also published as: CN103562271B; TW201305730A; CN103562271A; TWI529488B

Abstract

Provided is a curable composition which has a further augmented high refractive index and also has simultaneously the capabilities required of adhesives for optical applications: low shrinkage, photocurability, colorless transparency, and viscosity suitable for operations. This invention provides a curable composition containing a poly(meth)acrylate compound with a fluorene ring (component A), a polythiol compound with an aromatic ring or thioalkyl structure (component B), and a photopolymerization initiator (component C).

Description

Curable composition and optical adhesive

The present invention relates to an optical adhesive used for producing a composite optical element.

A photocurable composition mainly composed of an acrylate compound or the like is widely used as an adhesive for producing an optical element. For adhesives, adhesiveness, curability, mechanical strength, durability, and optical properties are basic performances, but in recent years, the refractive index has become an important performance as the functionality of optical elements increases. In particular, increasing the refractive index of the adhesive is highly desired because the degree of freedom in optical design is expanded. Examples of applications in which an adhesive having a high refractive index is used include an achromatic lens (achromatic lens) composed of two lenses bonded together, a hybrid aspherical lens composed of a composite of glass and resin, and dichroic Examples include prisms having complicated shapes such as prisms. Adhesives used for these applications naturally require not only a high refractive index but also performance such as adhesion, photocurability, colorless transparency, and viscosity suitable for work.

As a polyfunctional (meth) acrylate compound having a high refractive index, 9,9-bis (4- (2-acryloxyethoxy) phenyl) fluorene (hereinafter referred to as A-BPEF) (refractive index of cured product 1. 62), 4,4′-bis (methacryloylthio) diphenyl sulfide (hereinafter referred to as MPSMA) (refractive index of cured product 1.69) and the like are known. However, since these compounds are solid at room temperature, it is difficult to use them alone.

In general, a polyfunctional (meth) acrylate compound has a large shrinkage due to curing, and causes a decrease in adhesion when used as an adhesive. On the other hand, it is known that an ene / thiol composition obtained by combining an ethylenically unsaturated compound such as a (meth) acrylate compound and a thiol compound has a small shrinkage due to curing.

Patent Document 1 describes an ene-thiol composition composed of A-BPEF, an ethylenically unsaturated compound, and a thiol compound. According to the examples, the refractive index of the cured product is at most in the range of 1.58 to 1.61.
Patent Document 2 describes an ene-thiol composition composed of MPSMA, a vinyl monomer, and a polythiol compound. According to the example, the refractive index of the cured product is 1.649 at the maximum. However, MPSMA is easily yellow-colored and has a limit in the amount of dissolution in the composition because it is solid.
Patent Document 3 describes a resin composition composed of a resin component having a fluorene ring and a sulfur-containing compound having a diphenyl sulfide skeleton such as MPSMA, and a resin having a refractive index of 1.724. Illustrated. However, the resin composition in the present invention is substantially a thermoplastic resin obtained by kneading a polyester having a fluorene ring and a sulfur-containing compound and is not a curable composition, and of course, photocurability cannot be imparted.

JP 2010-254732 A Japanese Patent Laid-Open No. 03-021638 JP 2005-187661 A

Accordingly, an object of the present invention is to provide a curable composition that aims at further increasing the refractive index and also has performance as an optical adhesive such as low shrinkage, photocurability, colorless transparency, and viscosity suitable for work. To provide things.

As a result of intensive studies to solve the above problems, the present inventors have found an ene / thiol composition in which a poly (meth) acrylate compound having a fluorene ring and a polythiol compound having an aromatic ring or a thioalkyl structure are combined. The present inventors have found that it is possible to further increase the refractive index and have the necessary performance as an optical adhesive. Furthermore, it has been found that by containing an ethylenically unsaturated bond compound having a di (thiophenyl) sulfide structure or a di (thiophenyl) sulfone structure, it is possible to further increase the refractive index while maintaining the physical property balance. Moreover, it discovered that a viscosity could be adjusted freely, maintaining a physical property balance by containing a specific ethylenically unsaturated bond compound as a diluting monomer. The present invention has been achieved based on the above findings.
That is, the present invention
It is a curable composition containing a poly (meth) acrylate compound having a fluorene ring (component A), a polythiol compound having an aromatic ring or a thioalkyl structure (component B), and a photopolymerization initiator (component C).
In the present specification, acrylate compounds and methacrylate compounds are collectively referred to as (meth) acrylate compounds. Therefore, the (meth) acryloyl group includes both an acryloyl group and a methacryloyl group.

According to the present invention, a curable composition having a higher refractive index than conventional ones and also having the necessary performance as an optical adhesive such as low shrinkage, photocurability, colorless transparency, and viscosity suitable for work. Things can be provided.

The curable composition of the present invention contains a poly (meth) acrylate compound having a fluorene ring (A component), a polythiol compound having an aromatic ring or a thioalkyl structure (B component), and a photopolymerization initiator (C component). To do. Furthermore, it is preferable to contain an ethylenically unsaturated compound (component D) having a di (thiophenyl) sulfide structure or a di (thiophenyl) sulfone structure. Moreover, it is preferable to contain ethylenically unsaturated compounds (E component) other than A component and D component as a diluting monomer.

The poly (meth) acrylate compound (component A) having a fluorene ring is a compound having a fluorene ring and having two or more (meth) acryloyl groups in one molecule. The fluorene ring has the effect of increasing the refractive index. Moreover, the shrinkage accompanying hardening is small due to the bulky structure of the fluorene ring. Especially when pursuing higher refractive index, the following general formula (2)

(In the formula, m and n represent an integer in which the sum of m and n satisfies 0 to 4, R ³ represents an alkylene group having 1 to 5 carbon atoms, R ⁴ represents a hydrogen atom or a methyl group, R ⁵ represents a hydrogen atom or a methyl group.)
The compound represented by these is preferable. Examples of the compound represented by the general formula (2) include 9,9-bis (4- (2-acryloxyethoxy) phenyl) fluorene.

¡A component may be used alone or in combination of two or more. The content of component A is not particularly limited, but is preferably in the range of 10 to 90 parts by weight, more preferably 30 to 70 parts by weight, and particularly preferably in the range of 40 to 70 parts by weight with respect to 100 parts by weight of the curable composition. preferable.

As the polythiol compound (component B) having an aromatic ring or thioalkyl structure used in the present invention, the following general formula (1) -a

(In the formula, p represents an integer of 0 to 3, and R ¹ represents an alkylene group having 1 to 3 carbon atoms.)
The compound represented by these is preferable. Since the compound contains sulfur atoms and benzene rings in the molecule at a high concentration, the effect of increasing the refractive index is great. Moreover, although the aromatic ring contained in A component and D component is easily oxidized and yellowed by light or heat, the thiol group has an antioxidant effect, so that a cured product having excellent colorless transparency can be obtained. The component A is a solid or high-viscosity liquid at room temperature, but is adjusted to a viscosity suitable for work by the dilution effect of the component B. Moreover, since addition polymerization with the ethylenically unsaturated bond of a thiol group has little shrinkage | contraction accompanying hardening, when it uses as an adhesive agent, favorable adhesiveness is obtained. Examples of the compound represented by the general formula (1) -a include xylylene dithiol.

In addition, the polythiol compound (component B) having an aromatic ring or thioalkyl structure used in the present invention includes the following general formula (1) -b

(In the formula, q represents an integer of 0 to 3, and R ² represents a simple bond or an alkylene group having 1 to 3 carbon atoms.)
Also preferred are compounds represented by: Since the compound contains many thioalkyl structures containing a sulfur atom in the molecule, the effect of increasing the refractive index is great. Moreover, although the aromatic ring contained in A component and D component is easily oxidized and yellowed by light or heat, the thiol group has an antioxidant effect, so that a cured product having excellent colorless transparency can be obtained. The component A is a solid or high-viscosity liquid at room temperature, but is adjusted to a viscosity suitable for work by the dilution effect of the component B. Moreover, since the addition polymerization with the ethylenically unsaturated bond of a thiol group has small shrinkage | contraction accompanying hardening, when it uses as an adhesive agent, favorable adhesiveness is obtained. Examples of the compound represented by the general formula (1) -b include 2,5-bis (dimercaptomethyl) -1,4-dithiane.

Further, the polythiol compound (component B) having an aromatic ring or thioalkyl structure used in the present invention includes the following general formula (1) -c

(Wherein r1 to r3 represent an integer of 0 to 1, and X ₁ to X ₆ each independently represent hydrogen or a methylthiol group.)
The thiol compound represented by these is also preferable. Since the compound contains many thioalkyl structures containing a sulfur atom in the molecule, the effect of increasing the refractive index is great. Moreover, although the aromatic ring contained in A component and D component is easily oxidized and yellowed by light or heat, the thiol group has an antioxidant effect, so that a cured product having excellent colorless transparency can be obtained. The component A is a solid or high-viscosity liquid at room temperature, but is adjusted to a viscosity suitable for work by the dilution effect of the component B. Moreover, since the addition polymerization with the ethylenically unsaturated bond of a thiol group has small shrinkage | contraction accompanying hardening, when it uses as an adhesive agent, favorable adhesiveness is obtained. Examples of the compound represented by the general formula (1) -c include 1,5-dimercapto-3-thiapentane, 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane, 4,8-bis ( Mercaptomethyl) -1,11-dimercapto-3,6,9-trithiaundecane, 4,7-bis (mercaptomethyl) -1,11-dimercapto-3,6,9-trithiaundecane, 5,7- Examples thereof include bis (mercaptomethyl) -1,11-dimercapto-3,6,9-trithiaundecane.

¡B component may be used alone or in combination of two or more. The higher the content of the B component, the higher the refractive index, the lower shrinkage, the colorless transparency, and the better the dilution effect. However, the thiol group undergoes an addition reaction with the ethylenically unsaturated bond group in a one-to-one mole, so The thiol group is not preferable because it remains unreacted and remains. Therefore, with respect to the content of the B component, the functional group equivalent ratio of the thiol group contained in the B component is 0.2 to the total amount of the ethylenically unsaturated bond groups contained in the A component, the D component, and the E component. It is preferably in the range of 1.5, more preferably in the range of 0.5 to 1.35.

The photopolymerization initiator (component C) is not particularly limited as long as it generates active radical species by irradiation with actinic rays (ultraviolet rays, visible light, etc.). Specific examples of component C include 2,2-methoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -1-butanone, bis ( 2,4,6-Trimethylbenzoyl) -phenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, and the like.

¡C component may be used alone or in combination of two or more. The content of component C is not particularly limited, but is preferably in the range of 0.1 to 10 parts by weight and more preferably in the range of 0.5 to 5 parts by weight with respect to 100 parts by weight of the curable composition.

The following general formula (3)

(In the formula, X represents a sulfur atom or a sulfonyl group, and Z represents a (meth) acryloyl group, a vinyl group, or an allyl group.)
The ethylenically unsaturated compound (component D) represented by the formula is effective in increasing the refractive index due to the di (thiophenyl) sulfide structure and the di (thiophenyl) sulfone structure. Examples of the compound represented by the general formula (3) include 4,4′-bis (methacryloylthio) diphenyl sulfide.

D component may be used alone or in combination of two or more. The greater the content of the component D, the greater the effect of increasing the refractive index. On the other hand, yellow coloring increases, and the component D may not dissolve in the composition liquid. Accordingly, the content of the component D is preferably in the range of 50 parts by weight or less, more preferably in the range of 25 parts by weight or less, with respect to 100 parts by weight of the curable composition.

An ethylenically unsaturated compound (component E) other than component A and component D contained as a dilutable monomer is a compound having one or more ethylenically unsaturated bond groups in the molecule, and the viscosity of the composition is There is no limitation as long as it has an effect of lowering. In particular, a compound having an aromatic ring or a heterocyclic ring is preferable for the purpose of increasing the refractive index. Preferable specific examples of the component E include triallyl isocyanurate, triallyl cyanurate, diallyl phthalate, diallyl isophthalate, diallyl terephthalate, triallyl trimellitic acid, tetraallyl pyromellitic acid, phenyl (meth) acrylate, 2-phenoxyethyl ( Examples include meth) acrylate, o-phenylphenol (meth) acrylate, 2- (o-phenylphenoxy) ethyl (meth) acrylate, benzyl (meth) acrylate, 2- (benzyloxy) ethyl (meth) acrylate, and the like.

¡E component may be used alone or in combination of two or more. The greater the content of component E, the higher the dilution effect, but the lower the refractive index. Therefore, the content of the component E is preferably in the range of 40 parts by weight or less, more preferably in the range of 15 parts by weight or less with respect to 100 parts by weight of the curable composition.

If necessary, a polymerization inhibitor, an antioxidant, a light stabilizer (HALS), an ultraviolet absorber, a silane coupling agent, a release agent, a pigment, a dye, and the like may be added to the curable composition of the present invention. Is possible.

The curable composition of the present invention can be obtained by uniformly mixing each component at room temperature or under heating according to a conventional method. The composition after mixing may be filtered or defoamed as necessary.

∙ Regarding the viscosity of the optical adhesive, if the viscosity is too low, the adhesive may sag or flow, or the substrate may be displaced during pasting. On the other hand, if the viscosity is too high, it is not preferable because it becomes difficult to discharge or apply the adhesive, or bubbles are bitten during the bonding. The viscosity suitable for workability in the present invention depends on the use form of the adhesive such as the coating method and the laminating method, and cannot be defined unconditionally. However, as the B component, the general formula (1) -a or the general formula (1 ) When the polythiol compound represented by -c is used, it is preferably in the range of 500 to 20,000 mPa · s, more preferably in the range of 1,000 to 10,000 mPa · s. On the other hand, when the polythiol compound represented by the general formula (1) -b is used as the B component, it is preferably in the range of 1,000 to 30,000 mPa · s, more preferably 1,000 to 10,000 mPa · s. It is the range of s.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, the cure shrinkage rate in an Example was computed from the refractive index before and behind hardening according to the following formula.
X = (1−d1 / d2) × 100 [%]
R = (n ² −1) / (n ² +2) × M / d
Since R / M is constant before and after curing,
X = [1-{(n1 ² −1) / (n1 ² +2)} / {(n2 ² −1) / (n2 ² +2)}] × 100 [%]
(Where X is the curing shrinkage ratio, d is the specific gravity, d1 is the specific gravity before curing, d2 is the specific gravity after curing, R is the molecular refraction, n is the refractive index, n1 is the refractive index before curing, and n2 is the after curing. The refractive index of M and M represents the molecular weight.)

The viscosity of the curable composition was measured at a temperature of 25 ° C. using a cone / plate viscometer DV-II + (manufactured by Brookfield). The refractive index of the curable composition and the cured product was measured using an Abbe refractometer NAR-3T (manufactured by Atago Co., Ltd.). The transmittance of the cured product was measured using a spectrophotometer U-3500 (manufactured by Hitachi High-Tech) at a thickness of 0.25 mm and a wavelength of 400 nm.

Example 1
In a 300 ml flask, 71 g of 9,9-bis (4- (2-acryloxyethoxy) phenyl) fluorene (component A), 29 g of m-xylylene thiol (component B), and 3 g of 1-hydroxy-cyclohexyl phenyl ketone (C Component) was taken and stirred at 60 ° C. for 1 hour to prepare a curable composition.
The curable composition was sandwiched between two release-treated glass plates and irradiated with light from a metal halide lamp (120 W / cm) for 3 minutes from a distance of 30 cm. A cured film having a thickness of 0.25 mm was produced by the above procedure.
The physical properties of the curable composition and the cured film were as shown in Table 1.

Examples 2-5
A curable composition and a cured film were prepared in the same manner as in Example 1 except that the types and amounts of the A component, B component, D component, and E component were changed to those shown in Table 1. The physical properties of the curable composition and the cured film were as shown in Table 1.

Comparative Examples 1-10
A curable composition and a cured film were prepared in the same manner as in Example 1 except that the types and amounts of components A, B, D, and E were changed to those shown in Table 2. The physical properties of the curable composition and the cured film were as shown in Table 2. In addition, the value in which a physical property is inferior compared with an Example was underlined.

Explanation of Abbreviations in Tables a-1: 9,9-bis (4- (2-acryloxyethoxy) phenyl) fluorene a-2: 2,2-bis (4- (acryloxydiethoxy) phenyl) propane b- 1: m-xylylenedithiol b-2: pentaerythritol tetrakis (3-mercaptobutyrate)
b-3: 2,5-dimercaptomethyl-1,4-dithian b-4: 1,5-dimercapto-3-thiapentane d-1: 4,4′-bis (methacryloylthio) diphenyl sulfide e-1: 2-phenoxyethyl acrylate e-2: triallyl isocyanurate e-3: benzyl acrylate e-4: divinylbenzene

Example 6
In a 300 ml flask, 66 g of 9,9-bis (4- (2-acryloxyethoxy) phenyl) fluorene (component A), 34 g of 2,5-dimercaptomethyl-1,4-dithiane (component B), and 1- 3 g of hydroxy-cyclohexyl phenyl ketone (component C) was taken and stirred at 60 ° C. for 1 hour to prepare a curable composition.
The curable composition was sandwiched between two release-treated glass plates and irradiated with light from a metal halide lamp (120 W / cm) for 3 minutes from a distance of 30 cm. A cured film having a thickness of 0.25 mm was produced by the above procedure.
The physical properties of the curable composition and the cured film were as shown in Table 3.

Examples 7 to 13
A curable composition and a cured film were prepared in the same manner as in Example 6 except that the types and amounts of components A, B, D, and E were changed to the contents shown in Table 3. The physical properties of the curable composition and the cured film were as shown in Table 3.

Comparative Examples 11-20
A curable composition and a cured film were prepared in the same manner as in Example 6 except that the types and amounts of components A, B, D, and E were changed to the contents shown in Table 4. The physical properties of the curable composition and the cured film were as shown in Table 4. In addition, the value in which a physical property is inferior compared with an Example was underlined.

Explanation of Abbreviations in Table (a′-1) 9,9-Bis (4- (2-acryloxyethoxy) phenyl) fluorene (a′-2) 2,2-bis (4- (acryloxydiethoxy) phenyl ) Propane (b'-1) 2,5-dimercaptomethyl-1,4-dithiane (b'-2) pentaerythritol tetrakis (3-mercaptobutyrate)
(B'-3) 1,5-dimercapto-3-thiapentane (d'-1) 4,4'-bis (methacryloylthio) diphenyl sulfide (e'-1) triallyl isocyanurate (e'-2) benzyl acrylate (E'-3) 2- (o-phenylphenoxy) ethyl acrylate (e'-4) diallyl phthalate (e'-5) 2-phenoxyethyl acrylate (e'-6) divinylbenzene

Example 14
In a 300 ml flask, 80 g of 9,9-bis (4- (2-acryloxyethoxy) phenyl) fluorene (component A), 20 g of 1,5-dimercapto-3-thiapentane (component B), and 1-hydroxy-cyclohexylphenyl 3 g of ketone (C component) was taken and stirred at 60 ° C. for 1 hour to prepare a curable composition.
The curable composition was sandwiched between two release-treated glass plates, irradiated with light from a metal halide lamp (120 W / cm) for 3 minutes from a distance of 30 cm, and then the cured film was peeled from the glass plate. A cured film having a thickness of 0.25 mm was produced by the above procedure.
The physical properties of the curable composition and the cured film were as shown in Table 5.

Examples 15-27
A curable composition and a cured film were prepared in the same manner as in Example 14 except that the types and amounts of components A, B, D, and E were changed to the contents shown in Table 5. The physical properties of the curable composition and the cured film were as shown in Table 5.

Comparative Examples 21-30
A curable composition and a cured film were prepared in the same manner as in Example 14 except that the types and amounts of components A, B, D, and E were changed to the contents shown in Table 6. The physical properties of the curable composition and the cured film were as shown in Table 6. In addition, the value in which a physical property is inferior compared with an Example was underlined.

Explanation of abbreviations in the table a "-1: 9,9-bis (4- (2-acryloxyethoxy) phenyl) fluorene a" -2: 2,2-bis (4- (acryloxydiethoxy) phenyl) propane b ″ -1: 1,5-dimercapto-3-thiapentane b ″ -2: 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane b ″ -3: 4,8-bis (mercaptomethyl)- 1,11-dimercapto-3,6,9-trithiaundecane, 4,7-bis (mercaptomethyl) -1,11-dimercapto-3,6,9-trithiaundecane, and 5,7-bis (mercapto) Methyl) -1,11-dimercapto-3,6,9-trithiaundecane isomer mixture b "-4: pentaerythritol tetrakis (3-mercaptobutyrate)
d "-1: 4,4'-bis (methacryloylthio) diphenyl sulfide e" -1: benzyl acrylate e "-2: 2- (o-phenylphenoxy) ethyl acrylate e" -3: diallyl phthalate e "- 4: triallyl isocyanurate e "-5: 2-phenoxyethyl acrylate e" -6: divinylbenzene

Claims

A curable composition containing a poly (meth) acrylate compound having a fluorene ring (A component), a polythiol compound having an aromatic ring or a thioalkyl structure (B component), and a photopolymerization initiator (C component).
B component is (i) the following general formula (1) -a

(Wherein p represents an integer of 0 to 3, R 1 represents an alkylene group having 1 to 3 carbon atoms), (ii) the following general formula (1) -b

(Wherein q represents an integer of 0 to 3, R 2 represents a simple bond or an alkylene group having 1 to 3 carbon atoms), and (iii) the following general formula (1) -c

(Wherein r1 to r3 represent an integer of 0 to 1, and X 1 to X 6 each independently represent hydrogen or a methylthiol group), Item 2. The curable composition according to Item 1.
A component is the following general formula (2)

(In the formula, m and n represent an integer in which the sum of m and n satisfies 0 to 4, R 3 represents an alkylene group having 1 to 5 carbon atoms, R 4 represents a hydrogen atom or a methyl group, R 5 represents a hydrogen atom or a methyl group.)
The curable composition according to claim 1, which is a compound represented by the formula:
The curable composition according to claim 3, wherein the compound represented by the general formula (2) is 9,9-bis (4- (2-acryloxyethoxy) phenyl) fluorene.
The curable composition according to claim 2, wherein the compound represented by the general formula (1) -a is xylylene dithiol.
The curable composition according to claim 2, wherein the compound represented by the general formula (1) -b is 2,5-bis (dimercaptomethyl) -1,4-dithiane.
The compound represented by the general formula (1) -c is 1,5-dimercapto-3-thiapentane, 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane, 4,8-bis (mercaptomethyl) -1,11-dimercapto-3,6,9-trithiaundecane, 4,7-bis (mercaptomethyl) -1,11-dimercapto-3,6,9-trithiaundecane and 5,7-bis (mercapto) The curable composition according to claim 2, which is one or more compounds selected from the group consisting of (methyl) -1,11-dimercapto-3,6,9-trithiaundecane.
Furthermore, the following general formula (3)

(In the formula, X represents a sulfur atom or a sulfonyl group, and Z represents a (meth) acryloyl group, a vinyl group, or an allyl group.)
The curable composition in any one of Claim 1 to 7 containing the ethylenically unsaturated compound (D component) represented by these.
The curable composition according to claim 8, wherein the compound represented by the general formula (3) is 4,4'-bis (methacryloylthio) diphenyl sulfide.
Furthermore, the curable composition of Claim 8 or 9 which contains ethylenically unsaturated compounds (E component) other than A component and D component as a dilutable monomer.
E component is triallyl isocyanurate, triallyl cyanurate, diallyl phthalate, diallyl isophthalate, diallyl terephthalate, triallyl trimellitic acid, tetraallyl pyromellitic acid, phenyl (meth) acrylate, 2-phenoxyethyl (meth) acrylate, o One or more compounds selected from the group consisting of phenylphenol (meth) acrylate, 2- (o-phenylphenoxy) ethyl (meth) acrylate, benzyl (meth) acrylate and 2- (benzyloxy) ethyl (meth) acrylate The curable composition according to claim 10.
An optical adhesive containing the curable composition according to any one of claims 1 to 11.