Photocurable adhesive, cured object, and bonded lens

Abstract

The present invention provides a photocurable adhesive which has high adhesiveness and which, after curing, can exhibit a high refractive index. This photocurable adhesive is characterized by comprising a polymerizable compound (A) having a refractive index exceeding 1.55, a polymerizable compound (B) based on a phosphoric acid ester, a silane coupling agent (S), and a photopolymerization initiator (P). Due to the configuration, this photocurable adhesive has high adhesiveness, and upon curing, can form a cured object having a high refractive index.

Description

Light-curing adhesive, cured product, and cemented lens

[0001] The present invention relates to a photocurable adhesive, a cured product, and a cemented lens.

[0002] Photocurable adhesives have traditionally been used to bond optical components such as lenses and prisms in the assembly of optical devices. In recent years, as optical devices have become smaller and thinner, optical components with high refractive indices have been selected. Furthermore, in order to reduce optical loss in line with the high refractive indices of the optical components, photocurable adhesives are also required to be able to form cured products with high refractive indices after curing.

[0003] On the other hand, Patent Document 1 discloses a photocurable resin composition capable of forming a cured product with a high refractive index, which is a hard coat resin composition containing a fluorene-containing curable monomer having at least one (meth)acryloyl group in the molecule and a 9,9-bisarylfluorene skeleton, a polyfunctional curable monomer having three or more (meth)acryloyl groups in the molecule, and a monofunctional diluent monomer having one (meth)acryloyl group in the molecule. By using the fluorene-containing curable monomer, the resin composition can form a cured product with a high refractive index.

[0004] JP 2012-111931 A

[0005] However, the resin composition contains a tri- or higher-functional polyfunctional curing monomer to form a cured product with high hardness. The tri- or higher-functional polyfunctional curing monomer causes the resin composition to shrink significantly upon curing, resulting in reduced adhesiveness. Therefore, the resin composition cannot be used as an adhesive.

[0006] With photocurable adhesives, it is difficult to improve adhesion while maintaining a high refractive index, and there is a need for photocurable adhesives that have high adhesion and can exhibit a high refractive index after curing.

[0007] Therefore, an object of the present invention is to provide a photocurable adhesive that has high adhesiveness and can exhibit a high refractive index after curing.

[0008] The present invention solves the above-mentioned problems by providing a photocurable adhesive containing a polymerizable compound (A) having a refractive index exceeding 1.55, a phosphate ester-based polymerizable compound (B), a silane coupling agent (S), and a photopolymerization initiator (P).

[0009] According to the present invention, it is possible to provide a photocurable adhesive that has high adhesiveness and can exhibit a high refractive index after curing.

[0010] Fig. 1 is a schematic side view showing the procedure for measuring adhesive strength, Fig. 2 is a schematic plan view showing the procedure for measuring adhesive strength, and Fig. 3 is a cross-sectional view showing the main part of a cemented lens manufactured using a photocurable adhesive.

[0011] [Photocurable Adhesive] The photocurable adhesive contains a polymerizable compound (A) having a refractive index exceeding 1.55, a phosphate ester-based polymerizable compound (B), a silane coupling agent (S), and a photopolymerization initiator (P). By using the polymerizable compound (A) having a refractive index exceeding 1.55, the photocurable adhesive can form a cured product having a high refractive index. Furthermore, by using the phosphate ester-based polymerizable compound (B) and the silane coupling agent (S) in combination, the adhesive properties of the photocurable adhesive can be improved without interfering with the high refractive index achieved by the polymerizable compound (A). Therefore, by using the polymerizable compound (A) in combination with the polymerizable compound (B) and the silane coupling agent (S), a photocurable adhesive that combines high adhesiveness and a high refractive index can be provided.

[0012] (Polymerizable Compound (A)) The photocurable adhesive contains a polymerizable compound (A) having a refractive index exceeding 1.55. By using the polymerizable compound (A), the photocurable adhesive can form a cured product having a high refractive index. It is preferable that the polymerizable compound (A) does not contain a phosphorus atom (P). It is also preferable that the polymerizable compound (A) does not contain a silicon atom (Si).

[0013] The refractive index of the polymerizable compound (A) exceeds 1.55, but is preferably 1.56 or more, more preferably 1.57 or more, and even more preferably 1.58 or more. The refractive index of the polymerizable compound (A) is preferably 1.80 or less, more preferably 1.75 or less, more preferably 1.70 or less, and even more preferably 1.65 or less. By making the refractive index of the polymerizable compound (A) exceed 1.55, the photocurable adhesive can form a cured product having a high refractive index.

[0014] In the present invention, the refractive indexes of the polymerizable compound (A), the phosphate ester-based polymerizable compound (B), the aromatic (meth)acrylate (C), and the aliphatic (meth)acrylate (D) described below refer to the refractive index (liquid refractive index) of the compound itself before polymerization (before curing). The refractive indexes of the polymerizable compound (A), the phosphate ester-based polymerizable compound (B), the aromatic (meth)acrylate (C), and the aliphatic (meth)acrylate (D) are the refractive indexes of light with a wavelength of 589 nm under an environment of a temperature of 25°C and a relative humidity of 50%. The refractive indexes can be measured using a commercially available refractometer.

[0015] The polymerizable compound (A) has a polymerizable group. As the polymerizable group, a radical polymerizable group having an ethylenically unsaturated bond such as an ethylenically unsaturated double bond is preferred. Specific examples of the polymerizable group include an acryloyl group, a methacryloyl group, an epoxy group, and a vinyl group. Among them, from the viewpoint of reactivity, an acryloyl group, a methacryloyl group, and a vinyl group are preferred, and an acryloyl group and a methacryloyl group are more preferred. In addition, in the polymerizable compound (A), the polymerizable group may be used alone or in combination of two or more kinds.

[0016] In the polymerizable compound (A), the number of polymerizable groups contained in one molecule is preferably 1 or more. In the polymerizable compound (A), the number of polymerizable groups contained in one molecule is preferably 3 or less, and more preferably 2 or less. In particular, in the polymerizable compound (A), the number of polymerizable groups contained in one molecule is preferably 1. By setting the number of polymerizable groups to 3 or less, it is possible to reduce shrinkage during curing of the photocurable adhesive and maintain high adhesiveness.

[0017] The polymerizable compound (A) preferably further contains at least one of the following structures (a1) to (a4): a structure (a1) having two monocyclic aromatic hydrocarbon rings, which are bonded to each other by a single bond or a divalent linking group, a structure (a2) having one monocyclic aromatic hydrocarbon ring and one aromatic heterocycle, which are bonded to each other by a single bond or a divalent linking group, a structure (a3) ​​containing at least one fused aromatic ring, or a structure (a4) containing a 9,9-bisarylfluorene skeleton.

[0018] The polymerizable compound (A) preferably contains at least one of the above structures (a1) to (a4), but preferably contains only one of the above structures (a1) to (a4).

[0019] The polymerizable compound (A) preferably contains a structure (a1) having two monocyclic aromatic hydrocarbon rings, and these two aromatic hydrocarbon rings are bonded to each other via a single bond or a divalent linking group. The structure (a1) preferably does not contain a fused aromatic ring.

[0020] A preferred example of the monocyclic aromatic hydrocarbon ring in structure (a1) is a benzene ring. Examples of the divalent linking group in structure (a1) include -O-, -OC(=O)-, -OC(=O)O-, -S-, -SO-, and -SO2-. In structure (a1), the two aromatic hydrocarbon rings are preferably bonded to each other via a single bond, -O-, or -S-, and more preferably bonded to each other via a single bond or -O-.

[0021] In the polymerizable compound (A) having structure (a1), the number of polymerizable groups contained in one molecule is preferably 1 or more. In the polymerizable compound (A) having structure (a1), the number of polymerizable groups contained in one molecule is preferably 3 or less, more preferably 2 or less. In particular, in the polymerizable compound (A) having structure (a1), the number of polymerizable groups contained in one molecule is preferably 1. As the polymerizable group, an acryloyl group, a methacryloyl group, and a vinyl group are preferred, and an acryloyl group and a methacryloyl group are more preferred.

[0022] Specific examples of the polymerizable compound (A) having the structure (a1) include ethoxylated o-phenylphenol acrylate [refractive index 1.58, formula (6)] and m-phenoxybenzyl acrylate [refractive index 1.57, formula (8)]. Of these, m-phenoxybenzyl acrylate is preferred.

[0023]

[0024]

[0025] Commercially available products can also be used as the polymerizable compound (A) having the structure (a1). For example, a commercially available product of ethoxylated o-phenylphenol acrylate is available under the trade name "NK Ester A-LEN-10" manufactured by Shin-Nakamura Chemical Co., Ltd., and a commercially available product of m-phenoxybenzyl acrylate is available under the trade name "Light Acrylate POB-A" manufactured by Kyoeisha Chemical Co., Ltd.

[0026] The polymerizable compound (A) preferably contains a structure (a2) having one monocyclic aromatic hydrocarbon ring and one aromatic heterocycle, and the aromatic hydrocarbon ring and the aromatic heterocycle are bonded to each other via a single bond or a divalent linking group. The structure (a2) preferably does not contain a fused aromatic ring.

[0027] A preferred example of the monocyclic aromatic hydrocarbon ring in structure (a2) is a benzene ring. Examples of the aromatic heterocycle in structure (a2) include a furan ring, a thiophene ring, a pyrrole ring, an oxazole ring, a thiazole ring, an imidazole ring, a triazole ring, a pyridine ring, a pyrimidine ring, a pyrazine ring, and a 1,3,5-triazine ring. Of these, a monocyclic aromatic heterocycle is preferred, a furan ring, a thiophene ring, and a pyrrole ring are more preferred, and a thiophene ring is even more preferred.

[0028] The divalent linking group in the structure (a2) is —O—, —OC(═O)—, —OC(═O)O—, —S—, —SO—, —SO—, or —C(═O)O—Y 1 - (in the formula, Y 1represents a single bond or an alkylene group). 1 - is preferred. -C(=O)O-Y 1 In the linking group represented by -, Y 1 represents preferably an alkylene group having 1 to 10 carbon atoms. The alkylene group is linear or branched.

[0029] In the polymerizable compound (A) having structure (a2), the number of polymerizable groups contained in one molecule is preferably 1 or more. In the polymerizable compound (A) having structure (a2), the number of polymerizable groups contained in one molecule is preferably 3 or less, and more preferably 2 or less. In particular, in the polymerizable compound (A) having structure (a2), the number of polymerizable groups contained in one molecule is preferably 1. As the polymerizable group, an acryloyl group, a methacryloyl group, or a vinyl group is preferred, and a vinyl group is more preferred.

[0030] Examples of the polymerizable compound (A) having the structure (a2) include compounds represented by the following formula (I) or (II): The compounds represented by the following formula (I) or (II) each have a refractive index of more than 1.55 and not more than 1.64.

[0031] (In formula (I), R a1 , R a2 and R a3 are the same or different and represent a hydrogen atom, -OR a4 , -SR a4 , —C(═O)—R a4 , a phenyl group, a 2-thienyl group, or a 3-thienyl group; R a2 is R a1 or R a3 may be linked to form a ring containing a sulfur atom together with the two carbon atoms forming the thiophene ring to which they are attached. a4 are the same or different and represent an alkyl group having 1 to 5 carbon atoms. 1 represents a single bond or an alkylene group having 1 to 10 carbon atoms.

[0032] (In formula (II), R a5 , R a6 and R a7are the same or different and represent a hydrogen atom, -OR a4 , -SR a4 , —C(═O)—R a4 , a phenyl group, a 2-thienyl group, or a 3-thienyl group; R a5 is R a6 may be linked to form a ring containing a sulfur atom together with the two carbon atoms forming the thiophene ring to which they are attached. a4 are the same or different and represent an alkyl group having 1 to 5 carbon atoms. 1 represents a single bond or an alkylene group having 1 to 10 carbon atoms.

[0033] In each of the above formulas (I) and (II), R a4 represents an alkyl group having 1 to 5 carbon atoms. Examples of the alkyl group include linear or branched alkyl groups having 1 to 5 carbon atoms. Specific examples include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a t-butyl group, and an n-pentyl group. Of these, a methyl group is preferred.

[0034] In each of the above formulas (I) and (II), Y 1 represents a single bond or an alkylene group having 1 to 10 carbon atoms. Examples of the alkylene group include linear or branched alkylene groups having 1 to 10 carbon atoms. Specific examples include a methylene group, a methylmethylene group, a dimethylene group, a trimethylene group, an ethylmethylene group, a dimethylmethylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, a heptamethylene group, an octamethylene group, a nonamethylene group, and a decamethylene group.

[0035] As the polymerizable compound (A) having the structure (a2), a compound represented by the above formula (I) or (II) is preferred, with the compound represented by the above formula (I) being more preferred, and a compound represented by the following formula (Ia) (refractive index: 1.64) being more preferred:

[0036] Commercially available polymerizable compounds (A) having the structure (a2) may also be used. For example, commercially available compounds of the compound represented by the above chemical formula (Ia) include those manufactured by Shikoku Chemical Industries Co., Ltd. under the trade name "ReX-2."

[0037] The polymerizable compound (A) preferably contains a structure (a3) ​​containing at least one fused aromatic ring. The structure (a3) ​​preferably does not contain a 9,9-bisarylfluorene skeleton, and particularly preferably does not contain a skeleton represented by the following formula (1):

[0038] The fused aromatic ring includes a fused ring formed by condensing two or more monocyclic aromatic hydrocarbon rings, and is preferably a fused ring formed by condensing two or more benzene rings. Specific examples include a naphthalene ring, an anthracene ring, a pyrene ring, and a tetracene ring, and is preferably a naphthalene ring.

[0039] In the polymerizable compound (A) containing structure (a3), the number of fused aromatic rings contained in one molecule is preferably 1 or more. In the polymerizable compound (A) containing structure (a3), the number of fused aromatic rings contained in one molecule is preferably 5 or less, and more preferably 2 or less. In particular, in the polymerizable compound (A) containing structure (a3), the number of fused aromatic rings contained in one molecule is preferably 1.

[0040] In the polymerizable compound (A) having structure (a3), the number of polymerizable groups contained in one molecule is preferably 1 or more. In the polymerizable compound (A) having structure (a3), the number of polymerizable groups contained in one molecule is preferably 2 or less. In particular, in the polymerizable compound (A) having structure (a3), the number of polymerizable groups contained in one molecule is preferably 1. As the polymerizable group, an acryloyl group, a methacryloyl group, and a vinyl group are preferred, and an acryloyl group and a methacryloyl group are more preferred.

[0041] Specific examples of the polymerizable compound (A) having the structure (a3) ​​include 1-naphthylmethyl acrylate [refractive index 1.60, formula (7)].

[0042]

[0043] Commercially available products can also be used as the polymerizable compound (A) having the structure (a3). For example, a commercially available product of 1-naphthylmethyl acrylate is "Light Acrylate NMT-A" manufactured by Kyoeisha Chemical Co., Ltd.

[0044] The polymerizable compound (A) preferably contains a structure (a4) containing a 9,9-bisarylfluorene skeleton.

[0045] In the structure (a4), the 9,9-bisarylfluorene skeleton includes a skeleton represented by the following formula (1).

[0046]

[0047] (In formula (1), R 1 , R 2 , R 3 , and R 4 are each independently the same or different and represent a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, a cycloalkoxyl group having 5 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, or a halogen atom, and *1 and *2 are each single bonds and represent bonding positions.)

[0048] In the polymerizable compound (A) having the structure (a4), the number of polymerizable groups contained in one molecule is preferably 1 or more. In the polymerizable compound (A) having the structure (a4), the number of polymerizable groups contained in one molecule is preferably 2 or less. As the polymerizable group, an acryloyl group, a methacryloyl group, and a vinyl group are preferred, and an acryloyl group and a methacryloyl group are more preferred.

[0049] Examples of the polymerizable compound (A) having the structure (a4) include a polymerizable compound represented by the following formula (2): The compound represented by the following formula (2) has a refractive index of more than 1.55 and not more than 1.62.

[0050] (In formula (2), R 5 and R 6 may be the same or different and represent a hydrogen atom or a methyl group, R7 and R 8 may be the same or different and represent a linear or branched alkylene group, and n and m each independently represent an integer of 1 to 10.

[0051] Specific examples of the polymerizable compound (A) having the structure (a4) include 9,9-bis[4-(2-(meth)acryloyloxyethoxy)phenyl]fluorene, and the like. 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene (refractive index: 1.62) is preferred.

[0052] In the present invention, (meth)acryloyl means acryloyl or methacryloyl.

[0053] Commercially available products can also be used as the polymerizable compound (A) having the structure (a4). For example, 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene is available under the trade name "OGSOL-EA0200" manufactured by Osaka Gas Chemicals Co., Ltd., and under the trade names "OGSOL EA-F5710" and "OGSOL EA-0300" manufactured by Osaka Gas Chemicals Co., Ltd.

[0054] As described above, the adhesiveness of the photocurable adhesive can be improved by using a phosphate ester-based polymerizable compound (B) and a silane coupling agent (S). In particular, by using a combination of a phosphate ester-based polymerizable compound (B) and a silane coupling agent (S), the adhesiveness of the photocurable adhesive can be greatly improved even if the content of these is reduced. This allows the content of the polymerizable compound (A) in the photocurable adhesive to be increased, and the photocurable adhesive can maintain a high refractive index after curing.

[0055] The content of the polymerizable compound (A) in the photocurable adhesive is preferably 70 parts by mass or more, more preferably 75 parts by mass or more, more preferably 80 parts by mass or more, more preferably 85 parts by mass or more, and more preferably 90 parts by mass or more, relative to 100 parts by mass of the total amount of the polymerizable compound (A), the phosphate ester-based polymerizable compound (B), the silane coupling agent (S), and the photopolymerization initiator (P). The content of the polymerizable compound (A) in the photocurable adhesive is preferably 99 parts by mass or less, more preferably 98 parts by mass or less, more preferably 96 parts by mass or less, and more preferably 95 parts by mass or less, relative to 100 parts by mass of the total amount of the polymerizable compound (A), the phosphate ester-based polymerizable compound (B), the silane coupling agent (S), and the photopolymerization initiator (P). As described above, by using the phosphate ester-based polymerizable compound (B) and the silane coupling agent (S) in combination, the content of the polymerizable compound (A) can be increased to 70 parts by mass or more. Therefore, the refractive index of the photocurable adhesive after curing can be improved. By setting the content of the polymerizable compound (A) in the photocurable adhesive to 99 parts by mass or less, it is possible to add sufficient amounts of the phosphate ester-based polymerizable compound (B) and the silane coupling agent (S) necessary for improving adhesion to the photocurable adhesive.

[0056] (Phosphate ester-based polymerizable compound (B)) The photocurable adhesive contains a phosphate ester-based polymerizable compound (B). By using the phosphate ester-based polymerizable compound (B) in combination with a silane coupling agent (S), it is possible to improve the adhesiveness without reducing the refractive index of the photocurable adhesive after curing. It is preferable that the phosphate ester-based polymerizable compound (B) does not contain a silicon atom (Si).

[0057] The refractive index of the phosphate ester polymerizable compound (B) is preferably 1.45 or more, more preferably 1.46 or more. The refractive index of the phosphate ester polymerizable compound (B) is preferably 1.50 or less, more preferably 1.49 or less, more preferably 1.48 or less, and more preferably 1.47 or less. By making the refractive index of the phosphate ester polymerizable compound (B) 1.45 or more, the photocurable adhesive can form a cured product having a high refractive index.

[0058] The phosphate ester-based polymerizable compound (B) has a polymerizable group. As the polymerizable group, a radical polymerizable group having an ethylenically unsaturated bond such as an ethylenically unsaturated double bond is preferred. Specific examples include an acryloyl group, a methacryloyl group, an epoxy group, and a vinyl group. Among these, from the viewpoint of reactivity, an acryloyl group, a methacryloyl group, and a vinyl group are preferred, and an acryloyl group and a methacryloyl group are more preferred. In addition, in the phosphate ester-based polymerizable compound (B), the polymerizable group may be used alone or in combination of two or more types.

[0059] In the phosphate ester-based polymerizable compound (B), the number of polymerizable groups contained in one molecule is preferably 1 or more. In the phosphate ester-based polymerizable compound (B), the number of polymerizable groups contained in one molecule is preferably 3 or less, and more preferably 2 or less. By setting the number of polymerizable groups within the above range, it is possible to reduce shrinkage during curing of the photocurable adhesive and maintain high adhesiveness.

[0060] Examples of the phosphate ester-based polymerizable compound (B) include phosphate ester-based (meth)acrylates. Specific examples include 2-(meth)acryloyloxyethyl acid phosphate, bis(2-(meth)acryloyloxyethyl) acid phosphate, diphenyl-2-(meth)acryloyloxyethyl phosphate, phenyl bis-2-(meth)acryloyloxyethyl phosphate, and phenyl-2-(meth)acryloyloxyethyl acid phosphate. These phosphate ester-based (meth)acrylates each have a refractive index of 1.45 or more and 1.48 or less. Of these, 2-(meth)acryloyloxyethyl acid phosphate and bis(2-(meth)acryloyloxyethyl) acid phosphate are preferred, and bis(2-methacryloyloxyethyl) acid phosphate (refractive index 1.47) is more preferred. The phosphate ester-based polymerizable compound (B) may be used alone or in combination of two or more kinds.

[0061] In the present invention, the term "(meth)acrylate" means acrylate or methacrylate.

[0062] In the photocurable adhesive, the content of the phosphate ester-based polymerizable compound (B) is preferably 0.1 parts by mass or more, preferably 0.2 parts by mass or more, more preferably 0.3 parts by mass or more, and more preferably 0.4 parts by mass or more, relative to 100 parts by mass of the polymerizable compound (A). In the photocurable adhesive, the content of the phosphate ester-based polymerizable compound (B) is preferably 1.0 part by mass or less, more preferably 0.8 parts by mass or less, and more preferably 0.6 parts by mass or less, relative to 100 parts by mass of the polymerizable compound (A). By setting the content of the phosphate ester-based polymerizable compound (B) to 0.1 parts by mass or more, the adhesiveness of the photocurable adhesive can be improved. By setting the content of the phosphate ester-based polymerizable compound (B) to 1.0 part by mass or less, the photocurable adhesive can maintain a high refractive index after curing.

[0063] (Silane Coupling Agent (S)) The photocurable adhesive contains a silane coupling agent (S). As described above, by using the phosphate ester-based polymerizable compound (B) in combination with the silane coupling agent (S), it is possible to improve the adhesiveness without reducing the refractive index of the photocurable adhesive after curing.

[0064] The silane coupling agent (S) has a structure in which a hydrolyzable group is bonded to a silicon atom. The hydrolyzable group is not particularly limited, and examples thereof include a hydrogen atom, an alkoxy group, an acyloxy group, a ketoximate group, an aminooxy group, a mercapto group, and an alkenyloxy group. Since the adhesiveness of the photocurable adhesive is improved, an alkoxy group is preferred, and a methoxy group and an ethoxy group are more preferred.

[0065] The silane coupling agent (S) preferably has a polymerizable group. As the polymerizable group, a radical polymerizable group having an ethylenically unsaturated bond such as an ethylenically unsaturated double bond is preferred. Specific examples include an acryloyl group, a methacryloyl group, an epoxy group, and a vinyl group. Among them, from the viewpoint of reactivity, an acryloyl group, a methacryloyl group, and a vinyl group are preferred, and an acryloyl group and a methacryloyl group are more preferred. In addition, in the silane coupling agent (S), the polymerizable group may be used alone or in combination of two or more kinds.

[0066] In the silane coupling agent (S), the number of polymerizable groups contained in one molecule is preferably 1 or more. In the polymerizable compound (A), the number of polymerizable groups contained in one molecule is preferably 3 or less, and more preferably 2 or less. In particular, in the silane coupling agent (S), the number of polymerizable groups contained in one molecule is preferably 1. By setting the number of polymerizable groups within the above range, it is possible to reduce shrinkage during curing of the photocurable adhesive and maintain high adhesiveness.

[0067] As the silane coupling agent (S), an alkoxysilane having a radical polymerizable group in the molecule is preferred, a trialkoxysilane having a radical polymerizable group in the molecule is more preferred, a trimethoxysilane having a radical polymerizable group in the molecule, or a triethoxysilane having a radical polymerizable group in the molecule is more preferred.

[0068] Specifically, as the silane coupling agent (S), vinylalkoxysilane, methacryloxyalkylalkoxysilane, acryloxyalkylalkoxysilane are preferred, and vinyltrialkoxysilane, methacryloxyalkyltrialkoxysilane, acryloxyalkyltrialkoxysilane are more preferred.The alkoxy group contained in these silane coupling agents (S) is preferably methoxy group, ethoxy group, propoxy group, butoxy group, and more preferably methoxy group, ethoxy group.Silane coupling agent (S) may be used alone or in combination of two or more.

[0069] In the photocurable adhesive, the content of the silane coupling agent (S) is preferably 1.0 part by mass or more, more preferably 3.0 parts by mass or more, more preferably 3.5 parts by mass or more, and more preferably 3.8 parts by mass or more, relative to 100 parts by mass of the polymerizable compound (A). In the photocurable adhesive, the content of the silane coupling agent (S) is preferably 6.0 parts by mass or less, more preferably 5.0 parts by mass or less, more preferably 4.5 parts by mass or less, more preferably 4.0 parts by mass or less, and more preferably 3.9 parts by mass or less, relative to 100 parts by mass of the polymerizable compound (A). By making the content of the silane coupling agent (S) 1.0 part by mass or more, the adhesiveness of the photocurable adhesive can be improved. By making the content of the silane coupling agent (S) 6.0 parts by mass or less, the high refractive index of the photocurable adhesive after curing can be maintained.

[0070] (Aromatic (meth)acrylate (C)) The photocurable adhesive preferably further contains an aromatic (meth)acrylate (C) having a refractive index of 1.50 or more and 1.55 or less. By using the aromatic (meth)acrylate (C), the adhesive properties can be further improved while maintaining a high refractive index after curing of the photocurable adhesive. The aromatic (meth)acrylate (C) preferably does not contain a phosphorus atom (P) in the molecule. The aromatic (meth)acrylate (C) preferably does not contain a silicon atom (Si) in the molecule.

[0071] The refractive index of the aromatic (meth)acrylate (C) is preferably 1.50 or more, more preferably 1.51 or more, and is preferably 1.55 or less, more preferably 1.54 or less.

[0072] The aromatic (meth)acrylate (C) has a (meth)acryloyl group in the molecule. In the aromatic (meth)acrylate (C), the total number of (meth)acryloyl groups contained in one molecule is preferably 1 or more. In the aromatic (meth)acrylate (C), the total number of (meth)acryloyl groups contained in one molecule is preferably 3 or less, more preferably 2 or less. By keeping the total number of (meth)acryloyl groups within the above range, it is possible to reduce shrinkage during curing of the photocurable adhesive and maintain high adhesiveness.

[0073] Examples of the aromatic (meth)acrylate (C) include monofunctional aromatic (meth)acrylates. Examples of the monofunctional aromatic (meth)acrylate include 2-hydroxy-3-phenoxypropyl (meth)acrylate, phenoxybenzyl (meth)acrylate, phenoxyalkyl acrylates (such as phenoxyethyl acrylate), benzyl (meth)acrylate, phenyl (meth)acrylate, and dicyclopentenyl (meth)acrylate. These monofunctional aromatic (meth)acrylates each have a refractive index of 1.50 or more and 1.55 or less. The monofunctional aromatic (meth)acrylates may be used alone or in combination of two or more.

[0074] Examples of the aromatic (meth)acrylate (C) include polyfunctional aromatic (meth)acrylates. Examples of the polyfunctional aromatic (meth)acrylate include bifunctional aromatic (meth)acrylates such as the aromatic (meth)acrylate represented by the following formula (4) and the aromatic (meth)acrylate represented by the following formula (5). The aromatic (meth)acrylate represented by the following formula (4) and the aromatic (meth)acrylate represented by the following formula (5) each have a refractive index of 1.50 or more and 1.55 or less. The polyfunctional aromatic (meth)acrylates may be used alone or in combination of two or more.

[0075] (In formula (4), R 9 and R 10 may be the same or different and represent a hydrogen atom or a methyl group, R 11 and R 12may be the same or different and represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; R 13 and R 14 may be the same or different and represent an alkylene group, and p and q each independently represent an integer of 1 to 20.

[0076] In formula (4), R 11 and R 12 may be the same or different and represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an n-butyl group. Of these, a methyl group and an ethyl group are preferred, and a methyl group is more preferred.

[0077] In formula (4), R 13 and R 14 may be the same or different and represent an alkylene group. The alkylene group preferably has 1 to 10 carbon atoms, more preferably 1 to 5. Examples of the alkylene group include a methylene group (-CH2-), an ethylene group (-CH2-CH2-), an n-propylene group, and an n-butylene group. Of these, an ethylene group and an n-propylene group (-CH2-CH2-CH2-) are preferred.

[0078] (In formula (5), R 15 and R 16 may be the same or different and represent a hydrogen atom or a methyl group, R 17 and R 18 may be the same or different and represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; R 19 and R 20 may be the same or different and represent a hydroxyalkylene group; R 21 and R 22 may be the same or different and represent an alkylene group, and r and s each independently represent 0 or 1.

[0079] In formula (5), R 17 and R 18may be the same or different and represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an n-butyl group. Of these, a methyl group and an ethyl group are preferred, and a methyl group is more preferred.

[0080] In formula (5), R 19 and R 20 may be the same or different and represent a hydroxyalkylene group. A hydroxyalkylene group is an alkylene group in which one of the hydrogen atoms has been substituted with a hydroxyl group. The hydroxyalkylene group preferably has 1 to 4 carbon atoms. Specific examples of the hydroxyalkylene group include a hydroxymethylene group, a hydroxyethylene group, a 1-hydroxypropylene group, a 2-hydroxypropylene group, and a hydroxybutylene group. A 2-hydroxypropylene group is preferred.

[0081] In formula (5), R 21 and R 22 may be the same or different and represent an alkylene group. The alkylene group preferably has 1 to 10 carbon atoms, more preferably 1 to 4 carbon atoms. The alkylene group may be linear or branched, with branched groups being preferred. Examples of alkylene groups include a methylene group, an ethylene group, an n-propylene group, an n-butylene group, a methylmethylene group, a dimethylmethylene group, a 1-methylethylene group, a 1-ethylethylene group, a 1-methylpropylene group, and a 2-methylpropylene group. A 1-methylethylene group is preferred.

[0082] Commercially available products may also be used as the aromatic (meth)acrylate represented by the formula (5). Examples include products under the trade names "Epoxy Ester 3002M(N)," "Epoxy Ester 3002A(N)," "Epoxy Ester 3000MK," and "Epoxy Ester 3000A," all manufactured by Kyoeisha Chemical Co., Ltd.

[0083] The aromatic (meth)acrylate (C) is preferably a monofunctional aromatic (meth)acrylate or a bifunctional aromatic (meth)acrylate, and more preferably 2-hydroxy-3-phenoxypropyl (meth)acrylate or an aromatic (meth)acrylate represented by the above formula (4). The aromatic (meth)acrylate (C) may be used alone or in combination of two or more. The aromatic (meth)acrylate (C) preferably contains at least one of a monofunctional aromatic (meth)acrylate and a bifunctional aromatic (meth)acrylate, and more preferably contains both a monofunctional aromatic (meth)acrylate and a bifunctional aromatic (meth)acrylate.

[0084] In the photocurable adhesive, the content of the aromatic (meth)acrylate (C) is preferably 1.0 part by mass or more, more preferably 2.0 parts by mass or more, more preferably 4.0 parts by mass or more, more preferably 6.0 parts by mass or more, more preferably 7.0 parts by mass or more, more preferably 7.5 parts by mass or more, and more preferably 8.0 parts by mass or more, relative to 100 parts by mass of the polymerizable compound (A). In the photocurable adhesive, the content of the aromatic (meth)acrylate (C) is preferably 15.0 parts by mass or less, more preferably 12.0 parts by mass or less, and more preferably 10.0 parts by mass or less, relative to 100 parts by mass of the polymerizable compound (A). By making the content of the aromatic (meth)acrylate (C) 1.0 part by mass or more, the adhesiveness of the photocurable adhesive can be improved. By making the content of the aromatic (meth)acrylate (C) 15.0 parts by mass or less, the high refractive index of the photocurable adhesive after curing can be maintained.

[0085] (Aliphatic (meth)acrylate (D)) The photocurable adhesive preferably further contains an aliphatic (meth)acrylate (D) having a refractive index of 1.46 or more and 1.55 or less. By using the aliphatic (meth)acrylate (D), it is possible to further improve the adhesiveness while maintaining a high refractive index after curing of the photocurable adhesive. It is preferable that the aliphatic (meth)acrylate (D) does not contain a phosphorus atom (P) in the molecule. It is also preferable that the aliphatic (meth)acrylate (D) does not contain a silicon atom (Si) in the molecule.

[0086] The refractive index of the aliphatic (meth)acrylate (D) is preferably 1.46 or more, more preferably 1.47 or more, and more preferably 1.55 or less, more preferably 1.51 or less, and more preferably 1.50 or less.

[0087] The aliphatic (meth)acrylate (D) has a (meth)acryloyl group in the molecule. In the aliphatic (meth)acrylate (D), the total number of (meth)acryloyl groups contained in one molecule is preferably 1 or more. In the aliphatic (meth)acrylate (D), the total number of (meth)acryloyl groups contained in one molecule is preferably 3 or less, more preferably 2 or less. By keeping the total number of (meth)acryloyl groups within the above range, it is possible to reduce shrinkage during curing of the photocurable adhesive and maintain high adhesiveness. The aliphatic (meth)acrylate (D) may be used alone or in combination of two or more types.

[0088] The aliphatic (meth)acrylate (D) may include a chain aliphatic (meth)acrylate and a (meth)acrylate having an aliphatic ring. The chain aliphatic (meth)acrylate does not contain a ring such as an aliphatic ring or an aromatic ring. The (meth)acrylate having an aliphatic ring does not contain an aromatic ring.

[0089] Examples of the linear aliphatic (meth)acrylate include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, lauryl (meth)methacrylate, and stearyl (meth)acrylate. These alkyl (meth)acrylates each have a refractive index of 1.46 or more and 1.55 or less. The linear aliphatic (meth)acrylates may be used alone or in combination of two or more.

[0090] Examples of (meth)acrylates having an aliphatic ring include bifunctional (meth)acrylates having an aliphatic ring, such as 1,4-cyclohexanedimethanol di(meth)acrylate, norbornane di(meth)acrylate, norbornane dimethanol di(meth)acrylate, dicyclopentanyl di(meth)acrylate, and tricyclodecane dimethanol di(meth)acrylate. These bifunctional (meth)acrylates having an aliphatic ring each have a refractive index of 1.46 or more and 1.55 or less. The (meth)acrylates having an aliphatic ring may be used alone or in combination of two or more.

[0091] The aliphatic (meth)acrylate (D) is preferably a (meth)acrylate having an aliphatic ring, more preferably a bifunctional (meth)acrylate having an aliphatic ring, and more preferably tricyclodecane dimethanol diacrylate (refractive index 1.50) or tricyclodecane dimethanol dimethacrylate (refractive index 1.50). The aliphatic (meth)acrylate (D) may be used alone or in combination of two or more.

[0092] In the photocurable adhesive, the content of the aliphatic (meth)acrylate (D) is preferably 6.0 parts by mass or more, more preferably 7.0 parts by mass or more, and more preferably 8.0 parts by mass or more, relative to 100 parts by mass of the polymerizable compound (A). In the photocurable adhesive, the content of the aliphatic (meth)acrylate (D) is preferably 15.0 parts by mass or less, more preferably 12.0 parts by mass or less, and more preferably 10.0 parts by mass or less, relative to 100 parts by mass of the polymerizable compound (A). By making the content of the aliphatic (meth)acrylate (D) 6.0 parts by mass or more, the adhesiveness of the photocurable adhesive can be improved. By making the content of the aliphatic (meth)acrylate (D) 15.0 parts by mass or less, the high refractive index of the photocurable adhesive after curing can be maintained.

[0093] (Trifunctional or higher polyfunctional (meth)acrylate) The photocurable adhesive may contain a trifunctional or higher polyfunctional (meth)acrylate. A trifunctional or higher polyfunctional (meth)acrylate is a (meth)acrylate having three or more acryloyl groups and methacryloyl groups in the molecule. However, a trifunctional or higher polyfunctional (meth)acrylate may increase the shrinkage of the photocurable adhesive during curing, thereby reducing its adhesiveness. Therefore, it is preferable that the content of the trifunctional or higher polyfunctional (meth)acrylate is low.

[0094] The content of the tri- or higher functional polyfunctional (meth)acrylate in the photocurable adhesive is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, more preferably 1 part by mass or less, more preferably 0.5 parts by mass or less, and more preferably 0.01 parts by mass or less, relative to 100 parts by mass of the polymerizable compound (A). In particular, it is preferable that the photocurable adhesive does not contain a tri- or higher functional polyfunctional (meth)acrylate. By reducing the content of the tri- or higher functional polyfunctional (meth)acrylate, the adhesiveness of the photocurable adhesive can be improved.

[0095] Examples of the trifunctional or higher polyfunctional (meth)acrylate include trimethylolpropane tri(meth)acrylate, glycerin tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate. The polyfunctional (meth)acrylates may be used alone or in combination of two or more.

[0096] (Photopolymerization initiator (P)) The photocurable adhesive contains a photopolymerization initiator (P). The photopolymerization initiator (P) generates radicals when irradiated with radiation, and can radically polymerize monomers such as the polymerizable compound (A) and the phosphate ester-based polymerizable compound (B) contained in the photocurable adhesive.

[0097] Examples of the photopolymerization initiator (P) include α-hydroxyketone-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, thioxanthone-based photopolymerization initiators, and triazine-based photopolymerization initiators. Among these, α-hydroxyketone-based photopolymerization initiators are preferred because they have excellent compatibility with other components contained in the photocurable adhesive and can exhibit high photocurability. The photopolymerization initiator (P) may be used alone or in combination of two or more types.

[0098] The α-hydroxyketone photopolymerization initiator is not particularly limited, and examples thereof include 1-hydroxycyclohexyl phenyl ketone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, etc. Of these, 1-hydroxycyclohexyl phenyl ketone is preferred.

[0099] Examples of the acylphosphine oxide photopolymerization initiator include 2,4,6-trimethylbenzoyldiphenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0100] Examples of thioxanthone-based photopolymerization initiators include 2,4-diethylthioxanthone.

[0101] Examples of the triazine-based photopolymerization initiator include 2-[2-(furan-2-yl)vinyl]-4,6-bis(trichloromethyl)-1,3,5-triazine, 2-[2-(5-methylfuran-2-yl)vinyl]-4,6-bis(trichloromethyl)-1,3,5-triazine, 2-[(4-methoxyphenyl)vinyl]-4,6-bis(trichloromethyl)-1,3,5-triazine, and 2-[(3,4-dimethoxyphenyl)vinyl]-4,6-bis(trichloromethyl)-1,3,5-triazine.

[0102] In the photocurable adhesive, the content of the photopolymerization initiator (P) is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and more preferably 0.3 parts by mass or more, relative to 100 parts by mass of the polymerizable compound (A). In the photocurable adhesive, the content of the photopolymerization initiator (P) is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, and more preferably 2.0 parts by mass or less, relative to 100 parts by mass of the polymerizable compound (A). When the content of the photopolymerization initiator (P) is 0.1 parts by mass or more, the photocurability of the photocurable adhesive is improved. When the content of the photopolymerization initiator (P) is 5.0 parts by mass or less, the adhesiveness of the photocurable adhesive can be improved.

[0103] (Additives) The photocurable adhesive may contain additives such as fillers, thixotropic agents, adhesion-imparting resins, plasticizers, non-thermally expandable fine particles, dyes, pigments, flame retardants, and surfactants, within limits that do not impair the physical properties of the adhesive.

[0104] The method for producing the photocurable adhesive is not particularly limited, and the adhesive can be produced, for example, by mixing the polymerizable compound (A), the phosphate ester-based polymerizable compound (B), the silane coupling agent (S), and the photopolymerization initiator (P), as well as other additives as necessary, in a general manner, preferably under reduced pressure.

[0105] [Cured Product of Photocurable Adhesive] As described above, the photocurable adhesive can improve adhesion while maintaining a high refractive index after curing by using a combination of the polymerizable compound (A), the phosphate ester-based polymerizable compound (B), and the silane coupling agent (S). Therefore, the photocurable adhesive can form a cured product having a high refractive index.

[0106] The refractive index of the cured product of the photocurable adhesive is preferably greater than 1.55, more preferably 1.56 or greater, more preferably 1.57 or greater, more preferably 1.58 or greater, and even more preferably 1.59 or greater. The refractive index of the cured product of the photocurable adhesive is preferably 1.90 or less, more preferably 1.80 or less, and even more preferably 1.70 or less. According to the present invention, the refractive index of the cured product of the photocurable adhesive can be increased to exceed 1.55.

[0107] The refractive index of the cured photocurable adhesive can be measured according to the following procedure. A rectangular through-hole (5 mm long x 15 mm wide x 0.5 mm high) is punched out from the center of a silicone sheet (flat rectangular, 0.5 mm thick). Two release-treated polyethylene terephthalate (PET) sheets are prepared. The silicone sheet with the through-hole is sandwiched between the two PET sheets to obtain a laminate with a rectangular space (5 mm long x 15 mm wide x 0.5 mm high) in the center between the two PET sheets. The photocurable adhesive is filled into the space in the laminate, ensuring that no air gets in, and then a glass plate is placed on the laminate. Next, an ultraviolet lamp is used to irradiate the laminate with the glass plate on it with ultraviolet light at a peak wavelength of 360 nm at an illuminance of 2 mW / cm. 2The photocurable adhesive is cured by irradiating the photocurable adhesive with light at a wavelength of 589 nm for one hour, thereby obtaining a cured photocurable adhesive (cuboid, 5 mm long x 15 mm wide x 0.5 mm high). The refractive index of the cured photocurable adhesive is then measured with an Abbe refractometer at a temperature of 25°C and a relative humidity of 50%.

[0108] When hardening the photo-hardening adhesive, an ultraviolet lamp such as "FL20S-BL" manufactured by Toshiba Lighting & Technology Corporation can be used.

[0109] Photocurable adhesives have high adhesive properties. For example, when a three-point bending test was conducted on a laminate in which two glass plates were bonded together with a cured product of the photocurable adhesive, the adhesive strength of the cured product of the photocurable adhesive to the glass plates was 2.0 N / mm 2 More than 2.5 N / mm is preferable. 2 More preferably, 2.7 N / mm 2 More preferably, 3.0 N / mm 2 More preferably, 3.2 N / mm 2 More preferably, 3.5 N / mm 2 More preferably, 3.9 N / mm 2 Furthermore, when the above three-point bending test was carried out, the adhesive strength of the cured product of the photocurable adhesive to the plate glass was 6.0 N / mm 2 Preferably, 5.5 N / mm or less 2 More preferably, 5.0 N / mm 2 According to the present invention, the adhesive strength of the cured product of the photocurable adhesive is more preferably 2.5 N / mm 2 or more, and the adhesiveness can be improved.

[0110] When a three-point bending test is performed on a laminate in which two glass sheets are bonded together with the cured product of the photocurable adhesive, the adhesive strength of the cured product of the photocurable adhesive to the glass sheets can be measured in accordance with Method A of JIS K6856 (1994). Specifically, the adhesive strength can be measured according to the following procedure. An example of the glass sheets is "blue plate glass" commercially available from Engineering Test Services.

[0111] Two rectangular parallelepiped glass plates 1 and 2, each measuring 50 mm long, 25 mm wide, and 5 mm thick, are prepared. The entire surfaces of the two glass plates are washed with ethanol and dried in advance.

[0112] As shown in Figures 1 and 2, one glass sheet 1 is placed on a horizontal support surface 3, and the long side edge of the other glass sheet 2 is overlapped on the long side edge of the first glass sheet 1. The overlap width between the edges of the two glass sheets 1 and 2 is 12.5 mm. A photocurable adhesive 5 is interposed between the long side edges of the two glass sheets 1 and 2, and the photocurable adhesive 5 fills the entire lateral length between the opposing faces of the long side edges of the two glass sheets 1 and 2. The photocurable adhesive 5 is 25 mm long, 12.5 mm wide, and 0.01 mm thick. A supporting glass sheet 4 is disposed in the gap between the upper overlapping glass sheet and the support surface, and the upper glass sheet 2 is supported by the supporting glass sheet 4.

[0113] The photocurable adhesive 5 placed between the two glass sheets 1 and 2 was irradiated with ultraviolet light having a peak wavelength of 360 nm at an illuminance of 2 mW / cm using an ultraviolet lamp (manufactured by Toshiba Lighting & Technology Corporation, product name "FL20S-BL"). 2 The photocurable adhesive 5 is cured by irradiating the two glass sheets with ultraviolet light for one hour, thereby producing a laminate in which the two glass sheets are bonded together via the cured photocurable adhesive. The ultraviolet lamp is disposed vertically above the overlapping portion of the two glass sheets and at a height of 80 mm from the mounting surface.

[0114] The resulting laminate was subjected to a three-point bending test using a tabletop precision universal testing machine (for example, Shimadzu Corporation's "Autograph AGS-100NX" product name), where the overlapping portion of the two glass sheets was pressed at a pressing speed of 10 mm / min to measure the maximum load (N) at the time of fracture of the laminate. The adhesive strength (N / mm) was calculated based on the following formula: 2 The ambient temperature during the measurement of the maximum load is 25°C and the relative humidity is 50%. Three laminates are prepared according to the above procedure, and the adhesive strength of each laminate is calculated. The arithmetic mean value of the calculated adhesive strengths is taken as the adhesive strength of the cured product of the photocurable adhesive to the glass plate.

[0115] Adhesive strength (N / mm 2 ) = maximum load (N) / [0.025 (m) x 0.0125 (m) x 10 -6 ]

[0116] A conventionally known method is used as a method for producing a cured product of the photocurable adhesive. For example, the photocurable adhesive is irradiated with active energy rays (e.g., ultraviolet rays, electron beams, etc.) to polymerize the polymerizable compound (A), the phosphate ester-based polymerizable compound (B), and the silane coupling agent (S), and, if necessary, the aromatic (meth)acrylate (C) and the aliphatic (meth)acrylate (D), thereby photocuring the photocurable adhesive to obtain a cured product. The active energy rays are not particularly limited, and examples include electron beams, plasma, ultraviolet rays, α rays, β rays, and γ rays. Among these, electron beams and ultraviolet rays are preferred, and ultraviolet rays are more preferred.

[0117] The photocurable adhesive can be used to bond adherends, which include, but are not limited to, thin glass, optical glass, prisms, lenses, silicon wafers, semiconductor mounting components, and synthetic resin molded products (e.g., synthetic resin sheets).

[0118] Photocurable adhesives maintain a high refractive index after curing, reducing optical loss in optical components and improving the degree of freedom in optical design. Therefore, photocurable adhesives are particularly suitable for use as adhesives for optical components such as thin glass, optical glass, prisms, and lenses. For example, photocurable adhesives can be used to bond and integrate multiple optical components together, or to bond and integrate optical components with a housing for fixing the optical components.

[0119] [Cemented Lens] The photocurable adhesive can be used as an adhesive for bonding at least two lenses together in a cemented lens.

[0120] 3 shows a cross-sectional view of an example of a cemented lens 10. The cemented lens 10 has a first lens 11a, a second lens 11b, and an adhesive layer 12 made of a cured photocurable adhesive. The first lens 11a and the second lens 11b are bonded together by the adhesive layer 12.

[0121] The first lens 11a and the second lens 11b may each be a transparent resin lens or a transparent glass lens. Transparent glass lenses are preferred. Examples of materials for the transparent glass lenses include silicate glass, borosilicate glass, phosphate glass, quartz glass, and glass ceramics. The outer shape of each of the first lens 11a and the second lens 11b is preferably circular when viewed in a plane.

[0122] The first lens 11a has a concave lens surface, and the second lens 11b has a convex lens surface. The concave lens surface and the convex lens surface are bonded together by an adhesive layer 12. The outer diameter of the first lens 11a and the outer diameter of the second lens 11b may be different.

[0123] The adhesive layer 12 is made of a cured product of a photocurable adhesive, and the thickness of the adhesive layer 12 is preferably 5 to 50 μm.

[0124] The cemented lens can be manufactured using a known method. For example, a photocurable adhesive is applied to the upper surface of the first lens 11a. Next, the second lens 11b is laminated on the first lens 11a to obtain a laminate. At this time, the first lens 11a and the second lens 11b are aligned so that their centers coincide. Then, the laminate is irradiated with active energy rays to cure the photocurable adhesive and form an adhesive layer 12. This results in a cemented lens in which the first lens 11a and the second lens 11b are bonded together by the adhesive layer 12.

[0125] The cemented lens can be used in a lens unit. The lens unit has a lens barrel and a plurality of lenses, including the cemented lens, supported within the lens barrel. The lens unit may further include one or more lenses other than the cemented lens.

[0126] Furthermore, the lens unit can be combined with an image sensor to form a camera module. The camera module includes a lens unit and an image sensor that forms an image using light rays incident on the lens unit. The camera module is incorporated into imaging devices such as in-vehicle cameras, surveillance cameras, endoscope cameras, and cameras installed in electronic devices such as mobile phones, tablets, and personal computers.

[0127] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0128] Details of each compound used in the examples and comparative examples are given below.

[0129] (Polymerizable Compounds (A)) Polymerizable Compound (A1) (m-phenoxybenzyl acrylate, formula (8), containing structure (a1), refractive index 1.57, manufactured by Kyoeisha Chemical Co., Ltd., trade name "Light Acrylate POB-A") Polymerizable Compound (A2) (ethoxylated-o-phenylphenol acrylate, formula (6), containing structure (a1), refractive index 1.58, manufactured by Shin-Nakamura Chemical Co., Ltd., trade name "NK Ester A-LEN-10" Polymerizable Compound (A3) (having a structure containing a 9,9-bisarylfluorene skeleton, containing formula (1), structure (a4), refractive index 1.60, manufactured by Osaka Gas Chemicals Co., Ltd., trade name "OGSOL EA-F5710") Polymerizable Compound (A4) (having a structure containing a 9,9-bisarylfluorene skeleton, containing formula (1), structure (a4), refractive index 1.56, manufactured by Osaka Gas Chemicals Co., Ltd. Product name: "OGSOL EA-0300") Polymerizable compound (A5) (1-naphthylmethyl acrylate, formula (7), containing structure (a3), refractive index: 1.60, manufactured by Kyoeisha Chemical Co., Ltd., product name: "Light Acrylate NMT-A") Polymerizable compound (A6) (formula (Ia), containing structure (a2), refractive index 1.64, manufactured by Shikoku Chemical Industry Co., Ltd., product name: "Rex-2")

[0130]

[0131]

[0132] (Phosphate Ester-Based Polymerizable Compound (B)) Phosphate Ester-Based Polymerizable Compound (B1) (bis(2-methacryloyloxyethyl) acid phosphate, refractive index 1.47, product name "Light Ester P-2M" manufactured by Kyoeisha Chemical Co., Ltd.)

[0133] (Silane Coupling Agent (S)) 3-acryloxypropyltrimethoxysilane (refractive index 1.43, product name "KBM-5103" manufactured by Shin-Etsu Chemical Co., Ltd.)

[0134] (Aromatic (meth)acrylate (C)) Aromatic (meth)acrylate (C1) (2-hydroxy-3-phenoxypropyl acrylate, refractive index 1.53, product name "Epoxy Ester M-600A" manufactured by Kyoeisha Chemical Co., Ltd.) Aromatic (meth)acrylate (C2) (in the above formula (4), R 9 and R 10 represents a methyl group, and R 11 and R 12 represents a methyl group, and R 13 and R 14 represents an ethylene group, and p and q each independently represent an integer of 1 to 20, EO adduct dimethacrylate of bisphenol A, refractive index 1.54, product name "Light Ester BP-2EM" manufactured by Kyoeisha Chemical Co., Ltd.) Aromatic (meth)acrylate (C3) (in the above formula (4), R 9 and R 10 represents a methyl group, and R 11 and R 12 represents a methyl group, and R 13 and R 14 represents an ethylene group, and the arithmetic mean value of (p + q) is approximately 2.6. EO adduct dimethacrylate of bisphenol A, refractive index 1.54, manufactured by Kyoeisha Chemical Co., Ltd., trade name "Light Ester BP-2EK"

[0135] (Aliphatic (meth)acrylate (D)) Aliphatic (meth)acrylate (D1) (tricyclodecane dimethanol dimethacrylate, refractive index 1.50, product name "NK Ester DCP" manufactured by Shin-Nakamura Chemical Co., Ltd.)

[0136] (Photopolymerization initiator (P)) 1-hydroxycyclohexyl phenyl ketone (manufactured by IGM Resins B.V., trade name "Omnirad 184")

[0137] (Examples 1 to 10, Comparative Examples 1 to 3) The polymerizable compound (A), the phosphate ester-based polymerizable compound (B), the silane coupling agent (S), the aromatic (meth)acrylate (C), the aliphatic (meth)acrylate (D), and the photopolymerization initiator (P) were each supplied to a reaction vessel in the amounts shown in Tables 1 and 2 and mixed uniformly, thereby obtaining a photocurable adhesive.

[0138] The content (parts by mass) of the polymerizable compound (A) relative to 100 parts by mass of the total amount of the polymerizable compound (A), the phosphate ester-based polymerizable compound (B), the silane coupling agent (S), and the photopolymerization initiator (P) in the photocurable adhesive is shown in the column "Content of polymerizable compound (A)" in Tables 1 and 2.

[0139] [Evaluation] The refractive index of the cured products of the photocurable adhesives obtained in the Examples and Comparative Examples was measured according to the procedure described above, and is shown in the "Refractive Index" column of Tables 1 and 2.

[0140] Furthermore, a three-point bending test was performed on a laminate in which two glass plates were bonded together using the cured product of the photocurable adhesive obtained in the Examples and Comparative Examples. The adhesive strength of the cured product of the photocurable adhesive to the glass plates was measured according to the above procedure, and the results are shown in the "Adhesive Strength" column in Tables 1 and 2.

[0141]

[0142]

[0143] (Cross-reference to related applications) This application claims priority based on Japanese Patent Application No. 2023-198917, filed on November 24, 2023, the disclosure of which is incorporated herein by reference in its entirety.

[0144] According to the present invention, it is possible to provide a photocurable adhesive that has high adhesiveness and can exhibit a high refractive index after curing.

[0145] REFERENCE SIGNS LIST 1 Glass plate 2 Glass plate 3 Mounting surface 4 Supporting glass plate 5 Photocurable adhesive 10 Bonded camera 11a First lens 11b Second lens 12 Adhesive layer

Claims

1. A photocurable adhesive comprising a polymerizable compound (A) having a refractive index exceeding 1.55, a phosphate ester-based polymerizable compound (B), a silane coupling agent (S), and a photopolymerization initiator (P).

2. The photocurable adhesive according to claim 1, further comprising an aromatic (meth)acrylate (C) having a refractive index of 1.50 or more and 1.55 or less.

3. The photocurable adhesive according to claim 1, further comprising an aliphatic (meth)acrylate (D) having a refractive index of 1.46 or more and 1.55 or less.

4. A cured product of the photocurable adhesive according to claim 1, characterized in that the cured product has a refractive index of 1.57 or more.

5. When a three-point bending test was performed on a laminate consisting of the cured product and two glass plates bonded together via the cured product, the adhesive strength of the cured product to the glass plates was 2.5 N / mm 2 The cured product according to claim 4.

6. A cemented lens comprising a first lens, a second lens, and an adhesive layer made of a cured product of the photocurable adhesive according to claim 1 or 2, which bonds and integrates the first lens and the second lens.

Images