JP7614512B2 - Cationically curable composition, cured product and bonded body - Google Patents

Description

The present invention relates to a cationic curable composition, a cured material and a bonded body.

Traditionally, cationic curable compositions containing epoxy resins and the like have been used in a variety of applications, such as adhesives, sealants, potting agents, coating agents, and conductive pastes, due to their excellent adhesion, sealing properties, high strength, heat resistance, electrical properties, and chemical resistance. Their applications are diverse, and in particular in electronic and electrical devices, they are used in flat panel displays such as liquid crystal displays, organic electroluminescence, and touch panels, hard disk drives, mobile terminal devices, semiconductors, and camera modules.

JP 59-204676 A discloses a photocationically polymerizable resin composition containing an epoxy resin and a photocationic polymerization initiator that generates a Lewis acid when irradiated with active energy rays such as ultraviolet light. In addition, WO 2005/059002 (corresponding to the specification of U.S. Patent Application Publication No. 2007/0208106) discloses a cationically curable epoxy resin composition containing an epoxy resin component, a photocationic polymerization initiator, a thermal cationic polymerization initiator, and a filler.

However, the cationic polymerizable resin composition disclosed in JP-A-59-204676 had a problem that it could not cure in places not exposed to light. To solve this problem, it can be heated to about 200°C to generate acid from the cationic initiator and cure the composition, but the high curing temperature makes it difficult to apply to applications such as liquid crystal display elements and organic EL elements that are easily deteriorated by heat. On the other hand, the cationic curable epoxy resin composition disclosed in WO 2005/059002 (corresponding to U.S. Patent Application Publication No. 2007/0208106) has been improved by formulating a thermal cationic polymerization initiator so that it can cure at a relatively low temperature in places not exposed to light, but it has poor adhesion to aluminum die casting, polyphenylene sulfide (PPS), etc., which are widely used in recent years as materials for electronic and electrical component modules and in-vehicle parts.

The object of the present invention is to solve the above-mentioned problems, i.e., to provide a cationic curable composition that has excellent adhesion to aluminum die casting, PPS, etc. while maintaining photocurability and low-temperature curability.

The present invention overcomes the above-mentioned problems of the conventional art. That is, the present invention has the following gist:

[1] A cationic curable composition comprising the following components (A) to (E), containing 12 to 100 parts by mass of component (E) per 100 parts by mass of the total amount of component (A) and component (B):
Component (A): aromatic epoxy resin; Component (B): at least one of a hydrogenated epoxy resin (B1) and an alicyclic epoxy resin (B2); Component (C): photocationic polymerization initiator; Component (D): thermal cationic polymerization initiator; Component (E): polycaprolactone polyol having tri- or higher functional hydroxyl groups and a molecular weight of 1,700 or less.

[2] The cationic curable composition described in [1] above, in which the content of component (B) is 10 to 80 parts by mass per 100 parts by mass of the total amount of component (A) and component (B).

[3] The cationic curable composition according to [1] or [2] above, wherein the component (D) is at least one selected from the group consisting of aromatic sulfonium-based thermal cationic polymerization initiators, aromatic iodonium-based thermal cationic polymerization initiators, and thermal cationic polymerization initiators containing amine salts.

[4] The cationic curable composition according to any one of [1] to [3] above, wherein the component (D) is a thermal cationic polymerization initiator containing a salt having a quaternary ammonium cation.

[5] The cationic curable composition according to any one of [1] to [4] above, wherein the component (C) contains at least one of an aromatic iodonium salt and an aromatic sulfonium salt.

[6] The cationic curable composition according to any one of [1] to [5] above, wherein the component (A) contains at least one selected from the group consisting of aromatic bisphenol A type epoxy resins, aromatic bisphenol F type epoxy resins, and aromatic bisphenol E type epoxy resins.

[7] A cationic curable composition according to any one of [1] to [6] above, wherein the component (B) contains only one of the hydrogenated epoxy resin (B1) and the alicyclic epoxy resin (B2).

[8] The cationic curable composition according to any one of [1] to [6] above, wherein the component (B) comprises a hydrogenated epoxy resin (B1) and an alicyclic epoxy resin (B2).

[9] A cationic curable composition described in any one of [1] to [8] above, for use as an adhesive.

[10] A cationic curable composition according to any one of [1] to [8] above, which is used as an adhesive for an adherend whose substrate is aluminum die casting or PPS.

[11] A cured product of the cationic curable composition described in any one of [1] to [10] above.

[12] A bonded body obtained by bonding an adherend using the cationic curable composition described in any one of [1] to [10] above.

The present invention will be described in detail below. In this specification, "X to Y" is used to mean that the numerical values (X and Y) written before and after it are included as the lower and upper limits, and means "X or more and Y or less."

<Cationic curable composition>
The components (A) to (E) contained in the cationic curable composition of the present invention are as follows.

Component (A): aromatic epoxy resin; Component (B): at least one of a hydrogenated epoxy resin (B1) and an alicyclic epoxy resin (B2); Component (C): photocationic polymerization initiator; Component (D): thermal cationic polymerization initiator; Component (E): polycaprolactone polyol having tri- or higher functional hydroxyl groups and a molecular weight of 1,500 or less.

<Component (A)>
The aromatic epoxy resin, which is the component (A) of the present invention, is a compound that undergoes a crosslinking reaction due to cationic species generated from a cationic polymerization initiator by irradiation with active energy rays or heating. The type of the component (A) is not particularly limited, but examples thereof include aromatic bisphenol A type epoxy resin, aromatic bisphenol F type epoxy resin, aromatic bisphenol E type epoxy resin, diglycidyl ether of an alkylene oxide adduct of aromatic bisphenol A type, diglycidyl ether of an alkylene oxide adduct of aromatic bisphenol F type, diglycidyl ether of an alkylene oxide adduct of aromatic bisphenol E type, aromatic novolac type epoxy resin, urethane-modified aromatic epoxy resin, nitrogen-containing aromatic epoxy resin, rubber-modified aromatic epoxy resin containing polybutadiene or nitrile butadiene rubber (NBR), etc. Among these, aromatic bisphenol A type epoxy resin, aromatic bisphenol F type epoxy resin, or aromatic bisphenol E type epoxy resin is preferred from the viewpoint of obtaining a cationic curable composition having excellent adhesion to aluminum die casting, PPS, etc.

Examples of commercially available aromatic epoxy resins include jER (registered trademark, the same applies below) 825, jER827, jER828, jER828EL, jER828US, jER828XA, jER834, jER806, jER806H, jER807, jER807ST, jER604, and jER630 (all manufactured by Mitsubishi Chemical Corporation), EPICLON (registered trademark, the same applies below) 830, EPICLON EXA-830LVP, EPICLON EXA-850CRP, EPICLON 835LV, EPICLON HP4032D, EPICLON 703, EPICLON 720, EPICLON 726, and EPICLON HP820, EPICLON N-660, EPICLON N-680, EPICLON N-695, EPICLON N-655-EXP-S, EPICLON N-665-EXP-S, EPICLON N-685-EXP-S, EPICLON N-740, EPICLON N-775, EPICLON N-865 (all manufactured by DIC Corporation), ADEKA RESIN (registered trademark, the same applies below) EP4100, ADEKA RESIN EP4000, ADEKA RESIN EP4080, ADEKA RESIN EP4085, ADEKA RESIN EP4088, ADEKA RESIN EP4100HF, ADEKA RESIN EP4901HF, ADEKA RESIN EP4000S, ADEKA RESIN EP4000L, ADEKA RESIN EP4003S ... Examples of the aromatic epoxy resin include, but are not limited to, Deca Resin EP4010S, Adeka Resin EP4010L (both manufactured by ADEKA Corporation), Denacol (registered trademark, the same applies below) EX-614B, Denacol EX-411, Denacol EX-314, Denacol EX-201, Denacol EX-212, and Denacol EX-252 (all manufactured by Nagase ChemteX Corporation). These aromatic epoxy resins may be used alone or in combination of two or more.

<Component (B)>
The component (B) of the present invention is at least one of hydrogenated epoxy resin (B1) and alicyclic epoxy resin (B2), and is a compound that undergoes a crosslinking reaction by cationic species generated from a cationic polymerization initiator by irradiation with active energy rays or heating. The hydrogenated epoxy resin (B1) and the alicyclic epoxy resin (B2) may be used alone, or the hydrogenated epoxy resin (B1) and the alicyclic epoxy resin may be used in combination. When the hydrogenated epoxy resin (B1) and the alicyclic epoxy resin (B2) are used alone, they are preferred because they have even better adhesion to aluminum die casting. In addition, when these are used in combination, they are preferred because they have an excellent balance between photocurability and low-temperature curability and can maintain appropriate adhesion to various members. The hydrogenated epoxy resin (B1) is a compound without unsaturated bonds obtained by nuclear hydrogenation of the aromatic ring of an aromatic epoxy resin.

The type of hydrogenated epoxy resin (B1) is not particularly limited, but examples thereof include hydrogenated bisphenol A type epoxy resin, hydrogenated bisphenol F type epoxy resin, hydrogenated bisphenol E type epoxy resin, diglycidyl ether of hydrogenated bisphenol A type alkylene oxide adduct, diglycidyl ether of hydrogenated bisphenol F alkylene oxide adduct, hydrogenated phenol novolac epoxy resin, hydrogenated cresol novolac epoxy resin, etc. Among these, hydrogenated bisphenol A type epoxy resin, hydrogenated bisphenol F type epoxy resin, or hydrogenated bisphenol E type epoxy resin is preferred from the viewpoint of obtaining a cationic curable composition having excellent adhesion to aluminum die casting, PPS, etc.

Commercially available hydrogenated bisphenol A epoxy resins include, for example, jER YX-8000, jER YX-8034 (all manufactured by Mitsubishi Chemical Corporation), EPICLON EXA-7015 (manufactured by DIC Corporation), ST-3000 (manufactured by Nippon Steel Chemical & Material Co., Ltd.), Rikaresin HBE-100 (manufactured by New Japan Chemical Co., Ltd.), and Denacol EX-252 (manufactured by Nagase ChemteX Corporation). Commercially available hydrogenated bisphenol F epoxy resins include, for example, YL-6753 (manufactured by Mitsubishi Chemical Corporation).

Alicyclic epoxy resins (B2) include compounds having a functional group represented by the following formula (1). More specific examples include, but are not limited to, 3,4-epoxycyclohexylmethyl (3',4'-epoxy)cyclohexane carboxylate, ε-caprolactone-modified 3',4'-epoxycyclohexylmethyl, 3,4-epoxycyclohexane carboxylate, bis(3,4-epoxycyclohexyl)adipate, 1,2-epoxy-4-vinylcyclohexane, 1,4-cyclohexanedimethanol diglycidyl ether, epoxyethyldivinylcyclohexane, diepoxyvinylcyclohexane, 1,2,4-triepoxyethylcyclohexane, limonene dioxide, and alicyclic epoxy group-containing silicone oligomers. Among these, from the viewpoint of obtaining a cationic curable composition having excellent adhesion to aluminum die casting, PPS, etc., 3,4-epoxycyclohexylmethyl (3',4'-epoxy)cyclohexane carboxylate, ε-caprolactone-modified 3',4'-epoxycyclohexylmethyl, 3,4-epoxycyclohexane carboxylate, bis(3,4-epoxycyclohexyl)adipate, 1,2-epoxy-4-vinylcyclohexane, and 1,4-cyclohexanedimethanol diglycidyl ether are preferred.

Commercially available alicyclic epoxy resins (B2) are not particularly limited, but include, for example, CELLOXIDE (registered trademark) 2081 (3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate), CELLOXIDE (registered trademark) 2021P (3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate), CELLOXIDE (registered trademark) 2000 (1,2-epoxy-4-vinylcyclohexane), CELLOXIDE (registered trademark) 3000 (1-methyl-4-(2-methyloxiranyl)-7-oxabicyclo[4.1.0]heptane), EHPE3150 (1,2-epoxy-4-(2-oxiranyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol) (all manufactured by Daicel Corporation), TTA21 (Jiangsu Examples of suitable tertiary amine compounds include, but are not limited to, X-40-2670, X-22-169AS, and X-22-169B (all manufactured by Shin-Etsu Chemical Co., Ltd.).

The amount of the (B) component added is not particularly limited, but is preferably 10 to 95 parts by mass, more preferably 20 to 90 parts by mass, and even more preferably 30 to 85 parts by mass, of the total amount of the (A) component and the (B) component, 100 parts by mass. The amount of the hydrogenated epoxy resin of the (B) component added is not particularly limited, but is preferably in the range of 50 to 700 parts by mass, more preferably in the range of 100 to 600 parts by mass, and even more preferably in the range of 150 to 550 parts by mass, of the (A) component, 100 parts by mass. The amount of the alicyclic epoxy resin of the (B) component added is not particularly limited, but is preferably in the range of 20 to 300 parts by mass, more preferably in the range of 50 to 250 parts by mass, and even more preferably in the range of 70 to 200 parts by mass, of the (A) component, 100 parts by mass. By adjusting the amount of the component (B) to be added within the above range, it is possible to provide a cationically curable composition that has even better adhesion to aluminum die castings, PPS, and the like.

When hydrogenated epoxy resin (B1) and alicyclic epoxy resin (B2) are used in combination as component (B), it is preferable to use 10 to 300 parts by mass of alicyclic epoxy resin (B2) per 100 parts by mass of hydrogenated epoxy resin (B1), more preferably 30 to 150 parts by mass, and even more preferably 40 to 100 parts by mass of alicyclic epoxy resin (B2). When hydrogenated epoxy resin (B1) and alicyclic epoxy resin (B2) are used in combination as component (B), the ratio of component (A) to component (B) is as described above. By keeping the amounts of component (B1) and component (B2) used within the above ranges, a good balance of photocurability and low-temperature curability can be achieved, and appropriate adhesion to various members can be maintained.

<Component (C)>
The component (C) of the present invention is a photocationic polymerization initiator, which is a compound that generates cationic species by irradiation with active energy rays. The type of the component (C) is not particularly limited, but examples thereof include onium salts such as aromatic sulfonium salts and aromatic iodonium salts. The component (C) may be used alone or in combination of two or more kinds. In addition, a cationic polymerization initiator that is active against both active energy rays and heat is treated as the component (C) in the present invention.

The aromatic iodonium salts include salts containing an iodonium ion in which the two groups bonded to the iodine atom are aryl groups. More specifically, examples of such salts include diphenyliodonium tetrakis(pentafluorophenyl)borate, diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, di(4-nonylphenyl)iodonium hexafluorophosphate, and 4-methylphenyl-4-(1-methylethyl)phenyliodonium tetrakis(pentafluorophenyl)borate.

Commercially available aromatic iodonium salts include, for example, Omnicat (registered trademark) 250 (manufactured by IGM Resins B.V.), Bluesil PI 2074 (manufactured by Rhodia, 4-methylphenyl-4-(1-methylethyl)phenyliodonium-tetrakis(pentafluorophenyl)borate), B2380 (bis(4-tert-butylphenyl)iodonium hexafluorophosphate), B2381, D2238, D2248, D2253, I0591 (all manufactured by Tokyo Chemical Industry Co., Ltd.), and WPI-113 (bis[4-n-alkyl(C10-13)phenyl]iodonium hexafluorophosphate). Examples of suitable iodonium tetrakisfluorophenylborate include bis[4-n-alkyl(C10-13)phenyl]iodonium tetrakisfluorophenylborate), WPI-116 (bis[n-alkyl(C10-13)phenyl]iodonium hexafluoroantimonate), WPI-169, WPI-170 (bis(4-tert-butylphenyl)iodonium hexafluorophosphate), and WPI-124 (bis[4-n-alkyl(C10-13)phenyl]iodonium tetrakisfluorophenylborate) (all manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.).

The aromatic sulfonium salt includes sulfonium ions in which all three groups bonded to the sulfur atom are aryl groups. More specifically, for example, triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis(pentafluorophenyl)borate, 4,4'-bis[diphenylsulfonio]diphenylsulfide-bishexafluorophosphate, 4,4'-bis[di(β-hydroxyethoxy)phenylsulfonio]diphenylsulfide-bishexafluoroantimonate, 4,4'-bis[di(β-hydroxyethoxy)phenylsulfonio]diphenylsulfide-bishexafluorophosphate, 7-[di(p-toluyl)sulfonio]-2-isopropylthioxanthone hexafluoroantimonate, 7-[di(p-toluyl)sulfonio]-2-isopropylthioxanthone Examples of the aromatic sulfonium salt include tetrakis(pentafluorophenyl)borate, 4-phenylcarbonyl-4'-diphenylsulfonio-diphenylsulfide-hexafluorophosphate, 4-(p-tert-butylphenylcarbonyl)-4'-diphenylsulfonio-diphenylsulfide-hexafluoroantimonate, 4-(p-tert-butylphenylcarbonyl)-4'-di(p-toluyl)sulfonio-diphenylsulfide-tetrakis(pentafluorophenyl)borate, 4-methylphenyl-4-(1-methylethyl)phenyliodonium-tetrakis(pentafluorophenyl)borate, etc. However, the aromatic sulfonium salt is not limited to these. These aromatic sulfonium salts may be used alone or in combination of two or more.

Commercially available aromatic sulfonium salts include, for example, ADEKA ARCLES (registered trademark, the same applies below) SP-150, ADEKA ARCLES SP-170, ADEKA ARCLES SP-172 (all manufactured by ADEKA Corporation), CPI-100P, CPI-101A, CPI-110B, CPI-200K, CPI-210S (all manufactured by San-Apro Co., Ltd.), T1608, T1609, T2041 (tris(4-methylphenyl)sulfonium hexafluorophosphate), T2042 (tri-p-tolylsulfonium trifluoromethanesulfonate) (all manufactured by Tokyo Chemical Industry Co., Ltd.), Cyracure UVI-6990, Cyracure UVI-6974 (both manufactured by Union Carbide Corporation), DTS-200 (manufactured by Midori Chemical Industry Co., Ltd.), etc.

The amount of component (C) in the cationic curable composition of the present invention is not particularly limited, but is preferably within the range of 0.1 to 30 parts by mass, and more preferably within the range of 0.5 to 15 parts by mass, per 100 parts by mass of the total amount of components (A) and (B). If the content of component (C) is 0.1 part by mass or more per 100 parts by mass of the total amount of components (A) and (B), sufficient photocurability is obtained, and if it is 30 parts by mass or less, it is preferable from the viewpoint of excellent adhesion to aluminum die casting, PPS, etc.

<Component (D)>
The component (D) of the present invention is a thermal cationic polymerization initiator, which is a compound that generates cationic species by heating.The type of the initiator is not particularly limited, but examples thereof include aromatic sulfonium-based thermal cationic polymerization initiators, aromatic iodonium-based thermal cationic polymerization initiators, and thermal cationic polymerization initiators containing amine salts.Among these, the thermal cationic polymerization initiators containing amine salts are preferred from the viewpoint of obtaining a cationic curable composition that has excellent adhesiveness to aluminum die casting, PPS, etc. while maintaining photocurability and low-temperature curability.These initiators may be used alone or in combination of two or more.

Examples of the thermal cationic polymerization initiator containing the amine salt include a thermal cationic polymerization initiator containing a salt having a quaternary ammonium cation. More specific examples of the salt having a quaternary ammonium cation include a salt consisting of a quaternary ammonium cation and a borate anion, a salt consisting of a quaternary ammonium cation and an antimony anion, and a salt consisting of a quaternary ammonium cation and a phosphate anion. Among these, a salt consisting of a quaternary ammonium cation and a borate anion, or a salt consisting of a quaternary ammonium cation and an antimony anion is preferred because of its excellent adhesiveness to aluminum die casting, PPS, and the like.

Examples of the borate anion include tetrafluoroborate anion, tetrakis(perfluorophenyl)borate anion, etc. Examples of the antimony anion include tetrafluoroantimony anion, tetrakis(perfluorophenyl)antimony anion, etc. Examples of the phosphate anion include hexafluorophosphate anion, trifluoro[tris(perfluoroethyl)], etc.

Examples of commercially available thermal cationic polymerization initiators containing the amine salt include K-PURE (registered trademark, the same applies below) CXC-1612 (manufactured by King Industries, a thermal cationic polymerization initiator containing a salt consisting of a quaternary ammonium cation and a borate anion), K-PURE CXC-1821 (manufactured by King Industries, a thermal cationic polymerization initiator containing a salt consisting of a quaternary ammonium cation and an antimony anion), etc.

Commercially available aromatic sulfonium-based thermal cationic polymerization initiators include San-Aid (registered trademark, hereinafter the same) SI-60, San-Aid SI-60L, San-Aid SI-80, San-Aid SI-80L, San-Aid SI-100, San-Aid SI-100L, San-Aid SI-180L, San-Aid SI-B2A, San-Aid SI-B3A (all manufactured by Sanshin Chemical Industry Co., Ltd.), CI-2624 (manufactured by Nippon Soda Co., Ltd.), etc. Furthermore, examples of the aromatic iodonium-based thermal cationic polymerization initiators include diphenyliodonium trifluoromethanesulfonate (reagent), etc.

The amount of component (D) in the cationic curable composition of the present invention is not particularly limited, but is preferably within the range of 0.1 to 30 parts by mass, and more preferably within the range of 0.5 to 15 parts by mass, per 100 parts by mass of the total amount of components (A) and (B). If the amount of component (D) is 0.1 parts by mass or more per 100 parts by mass of the total amount of components (A) and (B), sufficient low-temperature curing properties are obtained, and if it is 30 parts by mass or less, it is preferable from the viewpoint of excellent adhesion to aluminum die casting, PPS, etc.

<Component (E)>
The component (E) of the present invention is not particularly limited as long as it is a polycaprolactone polyol having three or more functional hydroxyl groups and a molecular weight of 1700 or less. The component (E) of the present invention can have a remarkable effect of maintaining photocurability and low-temperature curability while exhibiting excellent adhesion to aluminum die casting, PPS, etc., by combining it with other components of the present invention and adjusting the blending ratio to a predetermined range described below. The molecular weight of the component (E) is more preferably in the range of 200 to 1500, and particularly preferably in the range of 250 to 1000. The molecular weight is a value obtained by measuring the hydroxyl value of the polycaprolactone polyol measured in accordance with JIS K1557-1:2007.

The component (E) is not particularly limited, but examples thereof include compounds represented by the following general formula (2):

Specific examples of the compound (E) include polycaprolactone triol, polycaprolactone tetraol, etc. Commercially available products of the component (E) include PLACCEL (registered trademark, the same applies below) 303, PLACCEL 305, PLACCEL 308, PLACCEL 309, PLACCEL 312, and PLACCEL 400 (manufactured by Daicel Corporation).

The cationic curable composition of the present invention is characterized in that it contains 12 to 100 parts by mass of component (E) per 100 parts by mass of the total amount of components (A) and (B). The amount is preferably 15 to 70 parts by mass, and more preferably 17 to 50 parts by mass. By keeping the amount within the above range, it is possible to obtain a cationic curable composition that has excellent adhesion to aluminum die casting, PPS, etc., while maintaining photocurability and low-temperature curability.

<Optional ingredients>
Furthermore, the cationic curable composition of the present invention may contain an appropriate amount of additives such as a silane coupling agent, a colorant, an oxetane compound, a vinyl ether compound, a sensitizer, a peroxide, a thiol compound, and a storage stabilizer, as long as the properties of the present invention are not impaired. Furthermore, the cationic curable composition of the present invention may contain various additives in appropriate amounts, within the range not impairing the characteristics of the present invention, such as inorganic fillers having an average particle size of 0.001 to 100 μm, such as calcium carbonate, magnesium carbonate, titanium oxide, magnesium hydroxide, talc, silica, alumina, glass, aluminum hydroxide, boron nitride, aluminum nitride, and magnesium oxide; conductive particles such as silver; flame retardants; rubbers such as acrylic rubber and silicone rubber; plasticizers; organic solvents; antioxidants such as phenolic antioxidants and phosphorus-based antioxidants; light stabilizers; ultraviolet absorbers; defoamers; foaming agents; release agents; leveling agents; rheology control agents; tackifiers; cure retarders; polymers and thermoplastic elastomers, such as polyimide resins, polyamide resins, phenoxy resins, cyanate esters, poly(meth)acrylate resins, polyurethane resins, polyurea resins, polyester resins, polyvinyl butyral resins, styrene-butadiene-styrene copolymers (SBS), and styrene-ethylene-butylene-styrene copolymers (SEBS). By adding these, it is possible to obtain a cationically curable composition and a cured product thereof that are excellent in resin strength, adhesive strength, flame retardancy, thermal conductivity, workability, etc.

A silane coupling agent is a compound that can improve the compatibility of components (A) to (E), improve low-temperature curing properties, and result in a cationic curable composition that has excellent adhesion to aluminum die castings, PPS, etc. The silane coupling agent is not particularly limited, but specific examples thereof include glycidyl group-containing silane coupling agents such as 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycidoxypropylmethyldiethoxysilane; vinyl group-containing silane coupling agents such as vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, and vinyltrimethoxysilane; (meth)acrylic group-containing silane coupling agents such as γ-methacryloxypropyltrimethoxysilane; amino group-containing silane coupling agents such as N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and N-phenyl-γ-aminopropyltrimethoxysilane; and others such as γ-mercaptopropyltrimethoxysilane and γ-chloropropyltrimethoxysilane. Among these, glycidyl group-containing silane coupling agents are preferably used, and among the glycidyl group-containing silane coupling agents, 3-glycidoxypropyltrimethoxysilane and 3-glycidoxypropyltriethoxysilane are preferred. These silane coupling agents may be used alone or in combination of two or more. The amount of the silane coupling agent is not particularly limited, but is preferably in the range of 0.1 to 30 parts by mass, more preferably 0.5 to 15 parts by mass, per 100 parts by mass of the total of the (A) component and the (B) component.

Examples of colorants include pigments and dyes, among which pigments are preferred from the viewpoint of durability. Furthermore, among pigments, black pigments are preferred from the viewpoint of excellent hiding power. Examples of black pigments include carbon black, black titanium oxide, copper chrome black, cyanine black, aniline black, etc. Among these, carbon black is preferred from the viewpoint of hiding power and dispersibility in the (A) component of the present invention. The amount of colorant in the cationic curable composition of the present invention is not particularly limited, but is preferably within the range of 0.01 to 30 parts by mass, more preferably within the range of 0.05 to 10 parts by mass, and even more preferably within the range of 0.1 to 5 parts by mass, relative to 100 parts by mass of the total amount of the (A) component and the (B) component.

Examples of oxetane compounds include 3-ethyl-3-hydroxymethyloxetane, 3-(meth)allyloxymethyl-3-ethyloxetane, (3-ethyl-3-oxetanylmethoxy)methylbenzene, 4-fluoro-[1-(3-ethyl-3-oxetanylmethoxy)methyl]benzene, [1-(3-ethyl-3-oxetanylmethoxy)ethyl]phenyl ether, isobutoxymethyl (3-ethyl-3-oxetanylmethyl) ether, 2-ethylhexyl (3-ethyl-3-oxetanylmethyl) ether, ethyl diethylene glycol (3-ethyl-3-oxetanylmethyl) ether, tetrahydrofurfuryl (3-ethyl-3-oxetanylmethyl) ether, tetrabromophenyl (3-ethyl-3-oxetanylmethyl) ether, 2-tetrabromophenoxyethyl (3-ethyl-3-oxetanylmethyl) ether, phenyl ether, pentachlorophenyl (3-ethyl-3-oxetanylmethyl) ether, pentabromophenyl (3-ethyl-3-oxetanylmethyl) ether, ethylene glycosyl bis (3-ethyl-3-oxetanylmethyl) ether, triethylene glycol bis (3-ethyl-3-oxetanylmethyl) ether, tetraethylene glycol bis (3-ethyl-3-oxetanylmethyl) ether, trimethylolpropane tris (3-ethyl-3-oxetanylmethyl) ether, pentaerythritol tris (3-ethyl-3-oxetanylmethyl) ether, pentaerythritol tetrakis (3-ethyl-3-oxetanylmethyl) ether, dipentaerythritol tetrakis (3-ethyl-3-oxetanylmethyl) ether, ditrimethylolpropane tetrakis (3-ethyl-3-oxetanylmethyl) ether, and the like. Examples of commercially available oxetane compounds include ARON OXETANE (registered trademark, the same applies below) OXT-212, ARON OXETANE OXT-221, ARON OXETANE OXT-213, and ARON OXETANE OXT-101 (manufactured by Toagosei Co., Ltd.).

Examples of vinyl ether compounds include 1,4-butanediol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, tetraethylene glycol divinyl ether, normal propyl vinyl ether, isopropyl vinyl ether, normal butyl vinyl ether, isobutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexyl vinyl ether, 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, 4-hydroxybutyl vinyl ether, 2-(2-vinyloxyethoxy)ethyl acrylate, 2-(2-vinyloxyethoxy)ethyl methacrylate, etc. Commercially available vinyl ether compounds include NPVE, IPVE, NBVE, IBVE, 2-EHVE, CHVE (all manufactured by Nippon Carbide Industries Co., Ltd.), HEVE, DEGV, HBVE (all manufactured by Maruzen Petrochemical Co., Ltd.), VEEA, VEEM (all manufactured by Nippon Shokubai Co., Ltd.), etc.

Examples of sensitizers include 9-fluorenone, anthrone, dibenzosuberone, fluorene, 2-bromofluorene, 9-bromofluorene, 9,9-dimethylfluorene, 2-fluorofluorene, 2-iodofluorene, 2-fluoreneamine, 9-fluorenol, 2,7-dibromofluorene, 9-aminofluorene hydrochloride, 2,7-diaminofluorene, 9,9'-spirobi[9H-fluorene], 2-fluorenecarboxaldehyde, 9-fluorenylmethanol, 2-acetylfluorene, benzophenone, and diethoxyacetophenone. Examples of the sensitizer include butanone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyl dimethyl ketal, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-methyl-2-morpholino(4-thiomethylphenyl)propan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone, 2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone oligomer, nitro compounds, dyes, etc. The amount of the sensitizer to be added is not particularly limited, but may be appropriately determined with reference to the absorption wavelength and molar extinction coefficient.

<Curing method>
The cationic curable composition of the present invention can be cured by irradiation with active energy rays (photocurable). The cationic curable composition of the present invention can be cured under low temperature conditions (low temperature curable). The cationic curable composition of the present invention can be cured by irradiation with active energy rays and under low temperature conditions. Examples of active energy rays include ultraviolet rays, electron beams, and visible light. The wavelength of the active energy rays is preferably 150 to 830 nm, more preferably 200 to 600 nm, and even more preferably 250 to 380 nm.

The above "low temperature" means that the curable temperature of the cationic curable composition of the present invention is low, and actually corresponds to the heating conditions of the curing method of the cationic curable composition of the present invention. The heating conditions (curable temperature) are not particularly limited, but are, for example, 45°C to 150°C, preferably 45°C or higher and lower than 150°C, more preferably 50°C or higher and lower than 140°C, and even more preferably 55°C or higher and lower than 130°C. In the case of a heat curing temperature of 45°C or higher and lower than 150°C, the heating time is preferably in the range of 3 minutes to less than 5 hours, more preferably 10 minutes to 3 hours. In addition, the cationic curable composition of the present invention can be cured by irradiation with active energy rays. In this case, examples of active energy rays include ultraviolet rays, electron beams, visible light, and the like, but are not particularly limited. The integrated light amount of the active energy rays is, for example, 300 to 100,000 mJ/cm ² , preferably 500 to 50,000 mJ/cm ² , more preferably 1,000 to 10,000 mJ/cm ² , even more preferably 2,000 to 5,000 mJ/cm ² , and particularly preferably 3,000 mJ/cm ^2. The wavelength of the active energy rays is preferably 150 to 830 nm, more preferably 200 to 600 nm, and even more preferably 250 to 380 nm.

<Adhesion method>
The cationic curable composition of the present invention can be used for adhering adherends. A specific example of the adhering method includes a method for adhering adherends, which includes step 1 of disposing the cationic curable composition of the present invention between a pair of adherends, step 2 of irradiating the cationic curable composition with active energy rays, and step 3 of heating the composition at a temperature of 45° C. or higher and lower than 150° C. after the irradiation. Each step will be described below.

[Step 1]
The cationic curable composition of the present invention is disposed between a pair of adherends. Specifically, for example, the cationic curable composition is dropped or applied onto one of the adherends, and the other adherend is disposed on the cationic curable composition, and the pair of adherends are aligned and positioned as desired. For application, for example, a coating method used for a known sealant or adhesive may be used. Specific examples of the coating method include dispensing using an automatic coater, spraying, inkjet, screen printing, gravure printing, dipping, spin coating, and the like. As the adherend, for example, metal, glass, plastic, and the like can be used, but from the viewpoint of compatibility with the cationic curable composition of the present invention, aluminum die casting and PPS are preferably used.

[Step 2]
The cationic curable composition arranged in step 1 is irradiated with active energy rays, and the curing of the cationic curable composition proceeds, and a pair of adherends are temporarily bonded. The curing of the cationic curable composition by irradiation with active energy rays proceeds particularly on the surface of the composition and in its vicinity. The irradiation may be performed directly on the arranged cationic curable composition, or may be performed indirectly through the adherend, particularly when the adherend is transparent or translucent.

[Step 3]
After the irradiation of the active energy rays in step 2, the cationic curable composition is further heated at a predetermined temperature, the cationic curable composition is completely cured, and the pair of adherends are completely bonded (mainly bonded). The curing of the cationic curable composition by heating proceeds particularly inside the composition other than the surface of the composition and its vicinity. By carrying out the curing reaction by irradiation in the above step 2 before the curing reaction by heating in step 3, the curing (crosslinking) reaction of the resin composition is quickly initiated, and the reaction inside the cationic curable composition not exposed to the active energy rays proceeds quickly due to the subsequent curing reaction by heating in step 3, and the complete curing of the cationic curable composition can be achieved. The heating temperature in step 3 is preferably 45°C to 150°C, more preferably 45°C or more and less than 140°C, even more preferably 50°C or more and less than 130°C, and particularly preferably 55°C or more and less than 125°C.

<Uses of the Cationic Curable Composition>
The applications of the cationically curable composition of the present invention are not particularly limited, and examples thereof include adhesives, sealants, coating agents, potting agents, conductive pastes, and the like. In addition, the fields to which the cationic curable composition of the present invention can be applied include, but are not limited to, the following: automotive fields such as switch parts, headlamps, internal engine parts, electrical components, driving engines, and brake oil tanks; flat panel display fields such as liquid crystal displays, organic electroluminescence, touch panels, plasma displays, and light-emitting diode display devices; recording fields such as video discs, CDs, DVDs, MDs, pickup lenses, hard disk peripheral parts, and Blu-ray discs; electronic materials fields such as sealing materials for electronic components, electric circuits, relays, electric contacts, and semiconductor elements, die bonding agents, conductive adhesives, anisotropic conductive adhesives, and interlayer adhesives for multilayer substrates including build-up substrates; camera modules such as CMOS image sensors; battery fields such as Li batteries, manganese batteries, alkaline batteries, nickel-based batteries, fuel cells, silicon-based solar cells, dye-sensitized solar cells, and organic solar cells; optical components fields such as optical fiber materials, optical passive components, optical circuit components, and optoelectronic integrated circuit peripherals in optical communication systems; mobile terminal devices; the architectural field; and the aviation field.

The cationic curable composition of the present invention has excellent adhesion to aluminum die casting, PPS, etc. while maintaining photocurability and low-temperature curability, and can therefore be particularly suitably used as an adhesive for assembling electronic/electrical component modules, vehicle-mounted components, etc. Examples of the electronic/electrical component modules include display housings, personal computer housings, optical pickup modules, mobile device housings, HDD housings, camera modules, projector housings, CD and DVD player housings, heat sinks, relays, connectors, module cases, etc. Examples of the vehicle-mounted components include ECU cases, vehicle-mounted camera modules, vehicle-mounted sensor modules (vehicle-mounted radar modules, vehicle-mounted lidar modules, etc.), capacitor cases, power modules, connectors, ignition coils, etc.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples.

<Preparation of Cationic Curable Composition>
Example 1
As the component (A), 20 parts by mass of aromatic bisphenol F type epoxy resin (a1) (manufactured by Mitsubishi Chemical Corporation, jER807ST),
As the component (B), 50 parts by mass of hydrogenated bisphenol A type epoxy resin (b1) (manufactured by Mitsubishi Chemical Corporation, jER YX-8000) and 30 parts by mass of 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate (b2) (manufactured by Daicel Corporation, Celloxide 2021P),
As the component (C), 3 parts by mass of 4-methylphenyl-4-(1-methylethyl)phenyliodonium tetrakis(pentafluorophenyl)borate (c1) (manufactured by Rhodia, Bluesil PI-2074),
As the component (D), 2 parts by mass of a thermal cationic polymerization initiator (d1) (K-PURE CXC-1821, manufactured by King Industries) containing a salt of a quaternary ammonium cation and a borate anion;
As the component (E), 25 parts by mass of a polycaprolactone triol (e1) (manufactured by Daicel Corporation, Plaxel 305) having three functional hydroxyl groups and a molecular weight of 550;
As a silane coupling agent, 2 parts by mass of 3-glycidoxypropyltrimethoxysilane,
The mixture was mixed for 60 minutes in a planetary mixer at room temperature (25° C.) in the dark to obtain a cationic curable composition of Example 1.

Example 2
A cationic curable composition of Example 2 was obtained by preparing the same as in Example 1, except that in Example 1, 20 parts by mass of the (a1) component was changed to 50 parts by mass, the (b1) component was not used, and 30 parts by mass of the (b2) component was changed to 50 parts by mass.

Example 3
A cationic curable composition of Example 3 was obtained in the same manner as in Example 1, except that in Example 1, 50 parts by mass of the (b1) component was changed to 80 parts by mass and the (b2) component was not used.

Comparative Example 1
A cationic curable composition of Comparative Example 1 was obtained by preparing the composition in the same manner as in Example 1, except that the component (a1) was removed and the amount of (b1) was changed from 50 parts by mass to 70 parts by mass.

Comparative Example 2
A cationic curable composition of Comparative Example 2 was obtained in the same manner as in Example 1, except that the component (e1) was omitted.

Comparative Example 3
A cationic curable composition of Comparative Example 3 was prepared in the same manner as in Example 1, except that the amount of the component (e1) was changed from 25 parts by mass to 10 parts by mass.

Comparative Example 4
A cationic curable composition of Comparative Example 4 was prepared in the same manner as in Example 1, except that the (e1) component in Example 1 was changed to a polycaprolactone polyol (e'1) (manufactured by Daicel Corporation, PLACCEL 205) having two hydroxyl groups and a molecular weight of 500.

Comparative Example 5
A cationic curable composition of Comparative Example 5 was prepared in the same manner as in Example 1, except that the (e1) component in Example 1 was changed to a polycaprolactone polyol (e'2) (manufactured by Daicel Corporation, PLACCEL 320) having three hydroxyl groups and a molecular weight of 2,000.

Comparative Example 6
A cationic curable composition of Comparative Example 6 was obtained in the same manner as in Example 1, except that the component (d1) was omitted.

<Photocuring test>
0.01 g of the cationic curable composition was dropped onto a glass test piece measuring 25 mm wide x 100 mm long x 5 mm thick. Then, an ultraviolet irradiation device (manufactured by JATEC Corporation, model number: JUL-M-433AN-05, ultraviolet wavelength: 365 nm) was used to irradiate the test piece with an integrated light quantity of 3000 mJ/ ^cm2 of active energy rays to obtain a test piece. Next, a glass rod with a sharp tip was brought into contact with the test piece, and the curability of the cationic curable composition was evaluated based on the following criteria. If the following criteria are evaluated as ○, it can be said that the curability is good.

[Evaluation Criteria]
◯: No adhesion to the rod. ×: There is adhesion to the rod.

<Low temperature curing test>
0.1 g of each cationic curable composition was dropped onto a hot plate set at 100° C., and after 30 minutes, a sharp-tipped glass rod was brought into contact with the cured product, and the curability of the composition was evaluated based on the following criteria. If the composition was rated as ○ in the following criteria, it can be said that the low-temperature curability was good.

[Evaluation Criteria]
◯: No adhesion to the rod. ×: There is adhesion to the rod.

<Tensile shear adhesive strength test for aluminum die casting>
The cationic curable compositions of the Examples and Comparative Examples were applied to a test piece made of aluminum die-cast ADC12 having a width of 25 mm, a length of 100 mm, and a thickness of 1 mm. Then, another test piece made of aluminum die-cast ADC12 was attached to the test piece so that the overlapping surface was 25 mm x 10 mm, and fixed with a clip. Then, the test piece was cured for 60 minutes in a hot air drying oven set at 120°C to obtain a test piece. Then, the tensile shear adhesive strength (unit: MPa) was measured using the test piece at 25°C using a universal tensile tester (tensile speed: 50 mm/min.) in accordance with JIS K6850:1999. The tensile shear adhesive strength was the value at the maximum strength. In order to use the cationic curable composition of the present invention as an adhesive for assembling electronic/electrical component modules, in-vehicle components, and the like, the tensile shear adhesive strength is preferably 5.0 MPa or more.

<Lasting shear adhesive strength test for polyphenylene sulfide (PPS)>
The cationic curable compositions of the Examples and Comparative Examples were applied to a PPS test piece having a width of 25 mm, a length of 100 mm, and a thickness of 1 mm. Then, another PPS test piece was attached to the test piece so that the overlapping surface was 25 mm x 10 mm, and fixed with a clip. Then, the test piece was cured for 60 minutes in a hot air drying oven set at 120°C to obtain a test piece. Then, the tensile shear adhesive strength (unit: MPa) was measured using the test piece at 25°C with a universal tensile tester (tensile speed: 50 mm/min.) in accordance with JIS K6850:1999. The tensile shear adhesive strength was the value at the maximum strength. In order to use the cationic curable composition of the present invention as an adhesive for assembling electronic/electrical component modules, in-vehicle components, and the like, the tensile shear adhesive strength is preferably 5.0 MPa or more.

The above test results are summarized in Table 1 below. Note that "-" in Table 1 below indicates that no measurement was performed.

As is clear from Table 1 above, the cationic curable compositions of Examples 1 to 3 were found to have excellent adhesion to aluminum die casting, PPS, etc. while maintaining photocurability and low-temperature curability.

Comparative Example 1 is a cationic curable composition that does not contain the (A) component of the present invention, but it was found that the adhesiveness to PPS was poor. Comparative Example 2 is a cationic curable composition that does not contain the (E) component of the present invention, but it was found that the adhesiveness to aluminum die casting and PPS was poor. Comparative Example 3 is a cationic curable composition in which the (E) component of the present invention is added in an amount outside the specified range, but it was found that the adhesiveness to aluminum die casting and PPS was poor. Comparative Examples 4 and 5 are cationic curable compositions in which a polyol other than the (E) component of the present invention is used, but it was found that the adhesiveness to aluminum die casting was poor. Comparative Example 6 is a cationic curable composition that does not contain the (D) component of the present invention, but it was found that the low-temperature curing test showed poor results.

The cationic curable composition of the present invention has excellent adhesion to aluminum die casting, PPS, etc. while maintaining photocurability and low-temperature curability, and is therefore industrially useful since it can be applied in a wide range of fields, such as bonding modular components of electrical and electronic components.

This application is based on Japanese Patent Application No. 2019-223752, filed on December 11, 2019, the disclosure of which is incorporated herein by reference in its entirety.

Claims (12)

A cationic curable composition comprising the following components (A) to (E), in which the component (B) is contained in an amount of 10 to 95 parts by mass and the component (E) is contained in an amount of 12 to 100 parts by mass relative to 100 parts by mass of the total amount of the components (A) and (B):
Component (A): Aromatic epoxy resin Component (B): At least one of a hydrogenated epoxy resin (B1) obtained by hydrogenating the aromatic ring of an aromatic epoxy resin and an alicyclic epoxy resin (B2) having a functional group represented by formula (1)

Component (C): a photocationic polymerization initiator; Component (D): a thermal cationic polymerization initiator; Component (E): a polycaprolactone polyol having three or more functional hydroxyl groups and a molecular weight of 1,700 or less. The cationic curable composition according to claim 1, which contains 10 to 80 parts by mass of component (B) per 100 parts by mass of the total amount of component (A) and component (B). The cationic curable composition according to claim 1 or 2, wherein the component (D) is at least one selected from the group consisting of aromatic sulfonium-based thermal cationic polymerization initiators, aromatic iodonium-based thermal cationic polymerization initiators, and thermal cationic polymerization initiators containing amine salts. The cationic curable composition according to any one of claims 1 to 3, wherein the component (D) is a thermal cationic polymerization initiator containing a salt having a quaternary ammonium cation. The cationic curable composition according to any one of claims 1 to 4, wherein the component (C) contains at least one of an aromatic iodonium salt and an aromatic sulfonium salt. The cationic curable composition according to any one of claims 1 to 5, wherein the component (A) contains at least one selected from the group consisting of aromatic bisphenol A type epoxy resins, aromatic bisphenol F type epoxy resins, and aromatic bisphenol E type epoxy resins. The cationic curable composition according to any one of claims 1 to 6 , wherein the component (B) comprises only one of a hydrogenated epoxy resin (B1) obtained by nuclear hydrogenation of an aromatic ring of the aromatic epoxy resin and an alicyclic epoxy resin (B2) having a functional group represented by the formula (1). The cationic curable composition according to any one of claims 1 to 6, wherein the component (B) comprises a hydrogenated epoxy resin (B1) obtained by nuclear hydrogenation of an aromatic ring of the aromatic epoxy resin , and an alicyclic epoxy resin (B2) having a functional group represented by the formula (1). The cationic curable composition according to any one of claims 1 to 8, which is used as an adhesive. The cationic curable composition according to any one of claims 1 to 9, which is used as an adhesive for an adherend that is an aluminum die cast or PPS. A cured product of the cationic curable composition according to any one of claims 1 to 10. A bonded body obtained by bonding an adherend using the cationic curable composition according to any one of claims 1 to 10.