Dual-cure adhesive composition

Abstract

To provide a dual-curing adhesive composition which has low toxicity, can be cured at a low temperature, and can form a cured product having high heat resistance.SOLUTION: The present invention relates to the dual-curing adhesive composition containing (a1) an oxetane compound, (a2) an alicyclic epoxy compound, (a3) an aromatic glycidyl ether-based epoxy compound, (b) a photo-cationic polymerization initiator, and (c) a thermal cationic polymerization initiator containing a tetrakis(pentafluorophenyl)borate compound. Based on 100 pts.mass of the total of the components (a1), (a2) and (a3), the content of (a1) is 20-95 pts.mass, the content of (a2) is 3-55 pts.mass, and the content of (a3) is 3-45 pts.mass.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a dual-cure adhesive composition that can be cured by cationic polymerization upon irradiation with light and heating, a cured product thereof, and a camera module using the same. [Background technology]

[0002] A camera module installed in a car, a smartphone, etc. has a lens, a cylindrical lens holder that holds the lens, and an image sensor fixed on a substrate that converts the light collected by the lens into an electrical signal. In assembling this camera module, it is necessary to firmly bond the lens holder to the substrate on which the image sensor is fixed. An adhesive is used for this bonding (Patent Document 1).

[0003] When bonding the lens holder to the substrate on which the imaging element is fixed, it is necessary to maintain an accurate distance between the lens and the imaging element. Specifically, the distance between the lens and the light-receiving surface of the imaging element must match the focal length of the lens. For this purpose, it has been proposed to use a UV / thermosetting adhesive (Patent Document 2).

[0004] Among UV- and heat-curable adhesive compositions, compositions containing epoxy resins are known for their high adhesion and excellent mechanical strength and water resistance. However, compositions containing epoxy resins often require high-temperature curing at temperatures above 150°C, making them unsuitable for bonding heat-sensitive components. Therefore, there was a need for the development of an adhesive composition that can be rapidly cured at low temperatures and form a cured product with high heat resistance.

[0005] As an adhesive that cures with both light and heat, for example, Patent Document 3 proposes a cationically curable epoxy resin composition containing an epoxy resin component, a photocationic initiator, a thermal cationic initiator, and a filler. In the examples of Patent Document 3, an antimony-containing compound is used as the photocationic initiator and the thermal cationic initiator. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-184801 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-141406 [Patent Document 3] WO2005 / 059002 publication Summary of the Invention [Problem to be solved by the invention]

[0007] It is known that the use of an antimony-containing compound as a thermal cationic polymerization initiator results in a high curing rate and enables curing at low temperatures, as in Patent Document 3. However, antimony has the problem of being highly toxic and difficult to handle, so there has been a demand for the development of an adhesive composition that can be cured at low temperatures without using antimony and that can achieve high heat resistance in the cured product.

[0008] Therefore, an object of the present invention is to provide an adhesive composition that is low in toxicity, can be cured at low temperatures, and produces a cured product with high heat resistance. [Means for solving the problem]

[0009] The present invention and preferred embodiments thereof are as follows.

[0010] 1. Component (a1): an oxetane compound; Component (a2): an alicyclic epoxy compound, Component (a3): an aromatic glycidyl ether epoxy compound, Component (b): a photocationic polymerization initiator; Component (c): a thermal cationic polymerization initiator containing a tetrakis(pentafluorophenyl)borate compound; A dual cure adhesive composition comprising: With respect to a total of 100 parts by mass of the component (a1), the component (a2), and the component (a3), The content of the component (a1) is 20 to 95 parts by mass, the content of the component (a2) is 3 to 55 parts by mass, The dual-cure adhesive composition contains the component (a3) ​​in an amount of 3 to 45 parts by mass.

[0011] 2. The dual-cure adhesive composition according to claim 1, wherein component (c) is an ammonium salt of tetrakis(pentafluorophenyl)boronic acid.

[0012] 3. The dual-cure adhesive composition according to 1 or 2 above, further comprising component (d) an inorganic filler.

[0013] 4. The dual-cure adhesive composition according to any one of 1 to 3 above, which is used for assembling a camera module.

[0014] 5. A cured product obtained by curing the dual cure adhesive composition described in any one of 1 to 4 above.

[0015] 6. A camera module comprising the cured product described in 5 above. [Effects of the Invention]

[0016] According to this embodiment, a dual-cure adhesive composition can be provided that can be cured at a low temperature of 120° C. or less without using an antimony compound, and that produces a cured product with excellent heat resistance. DETAILED DESCRIPTION OF THE INVENTION

[0017] One aspect of the dual cure adhesive composition of the present embodiment (hereinafter also simply referred to as "composition" or "adhesive composition") is Component (a1): an oxetane compound; Component (a2): an alicyclic epoxy compound, Component (a3): an aromatic glycidyl ether epoxy compound, Component (b): a photocationic polymerization initiator; Component (c): a thermal cationic polymerization initiator containing a tetrakis(pentafluorophenyl)borate compound; Including, With respect to a total of 100 parts by mass of the component (a1), the component (a2), and the component (a3), The content of the component (a1) is 20 to 95 parts by mass, the content of the component (a2) is 3 to 55 parts by mass, The content of the component (a3) ​​is 3 to 45 parts by mass.

[0018] The dual-cure adhesive composition of this embodiment can be thermally cured at a high reaction rate at low temperatures (for example, 120°C or lower, preferably 100°C or lower, more preferably 90°C or lower, and even more preferably 80°C or lower), and the cured product has a high glass transition temperature (Tg). Furthermore, the dual-cure adhesive composition of this embodiment does not require the use of highly toxic antimony-containing compounds as a thermal cationic polymerization initiator, and is therefore highly safe.

[0019] Each component will be described below.

[0020] <Component (a1): Oxetane compound> The oxetane compound (also simply referred to as component (a1)) is not particularly limited as long as it is a compound having an oxetane ring in the molecule, and preferably has a 3-oxetanyl group, and may have other functional groups as necessary. The oxetane compound may have at least one oxetane ring in the molecule, but preferably has two or more oxetane rings. The oxetane equivalent of a polyfunctional monomer having two or more oxetane groups is not particularly limited, but is preferably 400 or less, more preferably 300 or less, and preferably 100 or more.

[0021] The oxetane compound is not particularly limited, and examples thereof include bis[1-ethyl(3-oxetanyl)]methyl ether [(3-ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane)] represented by the following formula (a1-1), xylylene bisoxetane represented by the following formula (a1-2), 4,4'-bis[3-ethyl-(3-oxetanyl)methoxymethyl]biphenyl, 3-ethyl-3-[(2-ethylhexyloxy)methyl]oxetane, 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3-(4-hydroxybutyl)oxymethyloxetane, 1,4-bis(3-ethyl-3-oxetanylmethoxy)methylbenzene, (3-ethyloxetan-3-yl)methyl methacrylate, and (bis[(3-ethyl-3-oxetanyl)methyl]isophthalate).

[0022] The oxetane compounds may be used alone or in combination of two or more.

[0023] In one aspect of this embodiment, component (a1) preferably contains 3-ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane, which is represented by the following formula (a1-1): The content of the compound represented by formula (a1-1) in the total amount of component (a1) is preferably 80 mass% or more, and may be 100 mass%.

[0024] [ka]

[0025] [ka]

[0026] An example of a commercially available product of the compound represented by formula (a1-1) is OXT-221 (trade name, manufactured by Toagosei Co., Ltd.) Other commercially available products of the oxetane compound include OXT-212, OXT-101, and OXT-121 manufactured by Toagosei Co., Ltd., and EHO, OXMA, OXBP, HBOX, and OXIPA manufactured by Ube Industries, Ltd.

[0027] The composition containing component (a1) improves the rate of photocationic polymerization and the reaction rate in thermal cationic polymerization. In this specification, the reaction rate in thermal cationic polymerization can be calculated by the method described in the Examples below.

[0028] In the dual-cure adhesive composition of this embodiment, the content of component (a1) relative to 100 parts by mass of the total of components (a1), (a2), and (a3) ​​is preferably 20 parts by mass or more, more preferably 25 parts by mass or more, even more preferably 30 parts by mass or more, and still more preferably 35 parts by mass or more, and the upper limit is preferably 95 parts by mass or less, more preferably 90 parts by mass or less, even more preferably 80 parts by mass or less, and still more preferably 60 parts by mass or less.

[0029] If the content of component (a1) is too low, the photocationic curing property may decrease, whereas if the content of component (a1) is too high, the adhesive strength may decrease, or the self-reaction heat may become too large, raising safety concerns when exposed to light such as UV.

[0030] <Component (a2): Alicyclic epoxy compound> The alicyclic epoxy compound (also referred to as component (a2)) is not particularly limited as long as it is a compound having an alicyclic epoxy group in the molecule. As the alicyclic epoxy group, either one formed by oxygen atoms bonding to two adjacent carbon atoms constituting a cyclic aliphatic skeleton, or one formed by oxygen atoms bonding to two non-adjacent carbon atoms, can be used. From the viewpoint of reactivity and storage stability, it is preferable to use an alicyclic epoxy group formed by oxygen atoms bonding to two adjacent carbon atoms. The number of carbon atoms in the cyclic aliphatic skeleton is not particularly limited. For example, the cyclic aliphatic skeleton is preferably a 5- to 8-membered ring, more preferably a 5- or 6-membered ring, and even more preferably a 6-membered ring.

[0031] The number of alicyclic epoxy groups in the alicyclic epoxy compound is not particularly limited. The number of alicyclic epoxy groups is preferably 2 to 6 from the viewpoints of heat resistance and flexibility of the composition after curing, and more preferably 2 to 4 from the viewpoint of reducing the viscosity of the composition.

[0032] When the number of alicyclic epoxy groups in the alicyclic epoxy compound is two or more, the alicyclic epoxy groups may be bonded to each other by a single bond or via a linking group. The type of linking group that bonds the alicyclic epoxy groups to each other is not particularly limited. Examples of the linking group include a divalent hydrocarbon group, a carbonyl group (—CO—), an ether bond (—O—), an ester bond (—COO—), a carbonate bond (—OCOO—), and combinations thereof. Examples of the divalent hydrocarbon group include a linear or branched alkylene group having 1 to 18 carbon atoms (preferably 1 to 6 carbon atoms) and a divalent alicyclic hydrocarbon group (particularly a divalent cycloalkylene group). Examples of the linear or branched alkylene group include a methylene group, a methylmethylene group, a dimethylmethylene group, an ethylene group, a propylene group, and a trimethylene group. Furthermore, examples of the divalent alicyclic hydrocarbon group include divalent cycloalkylene groups (including cycloalkylidene groups) such as a 1,2-cyclopentylene group, a 1,3-cyclopentylene group, a cyclopentylidene group, a 1,2-cyclohexylene group, a 1,3-cyclohexylene group, a 1,4-cyclohexylene group, and a cyclohexylidene group.

[0033] In one aspect of this embodiment, the alicyclic epoxy compound may be one having an epoxy group with ring strain, such as a cyclohexene oxide structure or a cyclopentene oxide structure, in the molecule. In particular, one having two or more such epoxy groups in one molecule is preferred.

[0034] Examples of the alicyclic epoxy compound include compounds represented by the following formulas (1) to (5), ε-caprolactone-modified 3′,4′-epoxycyclohexylmethyl(3,4-epoxy)cyclohexanecarboxylate, 1,2-epoxy-4-vinylcyclohexane, and epoxy-modified organosiloxane.

[0035] [ka]

[0036] The alicyclic epoxy compounds may be used alone or in combination of two or more.

[0037] In one aspect of this embodiment, component (a2) preferably contains 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate represented by the above formula (1), and the content of the compound represented by formula (1) in the total amount of component (a2) is preferably 80 mass% or more, and may be 100 mass%.

[0038] An example of a commercially available product of the compound represented by formula (1) is Celloxide 2021P (trade name, manufactured by Daicel Corporation). Other commercially available products of alicyclic epoxy compounds include Celloxide 2081, Celloxide 2000, and Celloxide 8010, all manufactured by Daicel Corporation, and KR470, manufactured by Shin-Etsu Chemical Co., Ltd.

[0039] By including the component (a2), the composition can improve the Tg of the cured product.

[0040] In the dual-cure adhesive composition of this embodiment, the content of component (a2) relative to 100 parts by mass of the total of components (a1), (a2), and (a3) ​​is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, even more preferably 10 parts by mass or more, and still more preferably 20 parts by mass or more, and the upper limit is preferably 55 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 45 parts by mass or less.

[0041] If the content of component (a2) is too low, the Tg of the cured product may be low, resulting in reduced heat resistance, whereas if the content of component (a2) is too high, the low-temperature curing property may be reduced.

[0042] <Component (a3): Aromatic glycidyl ether epoxy compound> The aromatic glycidyl ether epoxy compound (also referred to as component (a3)) is not particularly limited as long as it is a compound having an aromatic hydrocarbon structure and a glycidyl ether group in the molecule, and preferably has two or more aromatic hydrocarbon structures and two or more glycidyl ether groups in the molecule.

[0043] Examples of component (a3) ​​include bisphenol-type epoxy compounds such as bisphenol A-type epoxy compounds, bisphenol F-type epoxy compounds, and bisphenol S-type epoxy compounds; novolac-type epoxy compounds such as phenol novolac-type epoxy compounds and cresol novolac-type epoxy compounds; and biphenyl-type epoxy compounds.

[0044] Component (a3) ​​preferably contains a bisphenol-type epoxy compound, preferably at least one selected from bisphenol A-type epoxy compounds and bisphenol F-type epoxy compounds, and more preferably contains at least a bisphenol A-type epoxy compound. Generally, bisphenol A-type epoxy compounds and bisphenol F-type epoxy compounds are derived by reacting bisphenol A and bisphenol F with epichlorohydrin, respectively. In one aspect of this embodiment, the content of the bisphenol A-type epoxy compound and / or bisphenol F-type epoxy compound in the total amount of component (a3) ​​is preferably 80 mass% or more, and may be 100 mass%.

[0045] The aromatic glycidyl ether epoxy compounds may be used alone or in combination of two or more.

[0046] Component (a3) ​​is preferably liquid or semi-solid at room temperature (about 23°C), but a solid compound may also be dissolved and used. The epoxy equivalent of component (a3) ​​is not particularly limited, but is preferably 50 to 480, and more preferably 60 to 450.

[0047] Commercially available aromatic glycidyl ether epoxy compounds include bisphenol A epoxy compounds such as 840, 840S, 850, 850S, EXA-850CRP, 850LC, 860, 1050, and 1055 manufactured by DIC Corporation; bisphenol F epoxy compounds such as 830, 830S, 835, EXA830CRP, EXA830LVP, and EXA835LV manufactured by DIC Corporation; bisphenol A epoxy compounds such as 825, 827, 828, 1001, and 1002 manufactured by Mitsubishi Chemical Corporation; bisphenol F epoxy compounds such as 806, 806H, and 807 manufactured by Mitsubishi Chemical Corporation; bisphenol A epoxy compounds such as RE-310S manufactured by Nippon Kayaku Co., Ltd.; bisphenol F epoxy compounds such as RE-303S-L manufactured by Nippon Kayaku Co., Ltd.; and NC-3000L and NC-2000L manufactured by Nippon Kayaku Co., Ltd.

[0048] Component (a3) ​​can impart adhesive strength to the dual cure adhesive composition.

[0049] In the dual-cure adhesive composition of this embodiment, the content of component (a3) ​​relative to 100 parts by mass of the total of components (a1), (a2), and (a3) ​​is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, even more preferably 10 parts by mass or more, and still more preferably 15 parts by mass or more, and the upper limit is preferably 45 parts by mass or less, more preferably 40 parts by mass or less, even more preferably 35 parts by mass or less, and still more preferably 30 parts by mass or less.

[0050] If the content of component (a3) ​​is too low, the adhesive strength may decrease, whereas if the content of component (a3) ​​is too high, the low-temperature curing property may decrease.

[0051] By containing components (a1), (a2), and (a3) ​​within the above-mentioned ranges, the dual-cure adhesive composition of this embodiment can form a cured product that has excellent adhesion, can be cured at a high reaction rate at low temperatures, and has high heat resistance.

[0052] In the dual-cure adhesive composition of this embodiment, the mass ratio of component (a1):component (a2):component (a3) ​​is, for example, preferably 20-95:3-55:3-45, more preferably 25-70:5-50:5-35, and even more preferably 30-60:7-45:5-27.

[0053] The total content of components (a1), (a2), and (a3) ​​is preferably 30% by mass or more, more preferably 40% by mass or more, and is preferably 80% by mass or less, more preferably 70% by mass or less, based on 100% by mass of the total mass of the composition.

[0054] <Component (b): Photocationic polymerization initiator> The photocationic polymerization initiator is a compound that generates cationic active species upon irradiation with light (preferably ultraviolet light). + B - where cation A + The aromatic iodonium ion is preferably an aromatic sulfonium ion, for example. The aromatic iodonium ion is represented by the formula: Ar 1 -I + -Ar 2 As expressed by + Group Ar bonded to 1 and Ar 2 Preferably, both of these are independently aromatic groups, and particularly preferably, an optionally substituted phenyl group.

[0055] The aromatic sulfonium ion is represented by the formula:

[0056] [ka] As expressed by S + Ar bonded to the center 1 , Ar 2 and Ar 3are each independently an aryl group, particularly a phenyl group which may have a substituent. Examples of the substituent include an alkyl group, a hydroxy group, a carboxyl group, an alkoxy group, an aryloxy group, an alkylcarbonyl group, an arylcarbonyl group, an aralkylcarbonyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an aralkyloxycarbonyl group, an alkylcarbonyloxy group, an arylcarbonyloxy group, an aralkylcarbonyloxy group, an alkoxycarbonyloxy group, an aryloxycarbonyloxy group, an aralkyloxycarbonyloxy group, an arylthiocarbonyl group, an arylthio group, an alkylthio group, an aryl group, a heterocyclic hydrocarbon group, an alkylsulfinyl group, an arylsulfinyl group, an alkylsulfonyl group, an arylsulfonyl group, and a hydroxy(poly)alkyleneoxy group.

[0057] In one aspect of this embodiment, the anion B - But B(C6F5)4 - B(aryl)4 such as - It may also contain an initiator that is an ion. B(aryl)4 - As for B(C6F5)4 - In addition to B(C6F4OCF3)4, - , B(C6F4CF3)4 - Anion B - However, B(aryl)4 - Initiators that are ionic tend to have faster cure rates.

[0058] To further improve adhesion, anion B - B(aryl)4 - The initiator may contain an anion other than the anion B. - As for PF6 - , (Rf) b PF 6-b 〕 - (Rf represents an alkyl group in which 80% or more of the hydrogen atoms are substituted with fluorine atoms. b represents the number of alkyl groups and is an integer of 1 to 5. Rf may be the same or different.) AsF6 - , BF4- The following can be mentioned:

[0059] As photocationic polymerization initiators, (4-hydroxyphenyl)methylbenzylsulfonium tetrakis(pentafluorophenyl)borate, 4-(4-biphenylylthio)phenyl-4-biphenylylphenylsulfonium tetrakis(pentafluorophenyl)borate, 4-(phenylthio)phenyldiphenylsulfonium phenyltris(pentafluorophenyl)borate, [4-(4-biphenylylthio)phenyl]-4-biphenylylphenylsulfonium phenyltris(pentafluorophenyl)borate, diphenyl[4-(phenylthio)phenyl]sulfonium tris(pentafluoroethyl)trifluorophosphate, diphenyl[4-(phenylthio)phenyl]sulfonium tetrakis(pentafluorophenyl)borate, diphenyl[4-(phenylthio)phenyl]sulfonium hexafluorophosphate, and 4-(4-biphenylylthio)phenyl-4-biphenylylphenylsulfonium Examples include tris(pentafluoroethyl)trifluorophosphate, bis[4-(diphenylsulfonio)phenyl]sulfide phenyltris(pentafluorophenyl)borate, [4-(2-thioxanthonylthio)phenyl]phenyl-2-thioxanthonylsulfonium phenyltris(pentafluorophenyl)borate, and compounds represented by the following formula:

[0060] [ka]

[0061] Commercially available products that can be used as photocationic polymerization initiators include CPI-100P, CPI-101A, CPI-200K, CPI-210S, CPI-310B, CPI-310FG, CPI-410S, and IK-1 manufactured by San-Apro Co., Ltd.; Irgacure 250 and Irgacure 270 manufactured by Chiba Specialty Chemicals; and BLUESIL PI 2074 manufactured by Elkem.

[0062] The cationic photopolymerization initiators may be used alone or in combination of two or more.

[0063] The content of the cationic photopolymerization initiator is not particularly limited, but the lower limit is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and the upper limit is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, relative to 100 parts by mass of the total content of the components (a1), (a2), and (a3).

[0064] In terms of reducing toxicity, the content of the antimony-containing compound in the cationic photopolymerization initiator is preferably small. The content of the antimony-containing compound is preferably 3% by mass or less, more preferably 1% by mass or less, and even more preferably 0% by mass, based on 100% by mass of the total mass of the cationic photopolymerization initiator.

[0065] <Component (c): Thermal cationic polymerization initiator> A thermal cationic polymerization initiator is a compound that generates cationic active species by heat but cannot generate a practical amount of cationic active species by light irradiation. + B - In this embodiment, the temperature at which the cationic active species is generated is low, with the lower limit being preferably 60°C or higher, more preferably 70°C or higher, and the upper limit being preferably 120°C or lower, more preferably 100°C or lower, even more preferably 90°C or lower, and still more preferably 80°C or lower.

[0066] In this embodiment, the thermal cationic polymerization initiator is an anion B - However, the following formula (c-1):

[0067] [ka] It is preferable that the compound contains an anion species represented by the formula: ##STR1## namely, a tetrakis(pentafluorophenyl)borate compound.

[0068] Cationic species A of tetrakis(pentafluorophenyl)borate compounds + is expressed by the following formula (c-2):

[0069] [ka] Preferably, the ammonium cation is represented by the formula:

[0070] In the formula (c-2), Y1, Y2, Y3, and Y4 each independently represent a hydrogen atom, a linear, branched, or cyclic alkyl group having 1 to 20 carbon atoms, or an aryl group. At least one of Y1, Y2, Y3, and Y4 is preferably an aryl group.

[0071] In formula (c-2), the alkyl group has 1 to 20 carbon atoms, preferably 1 to 15. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, and a cyclohexyl group. Examples of the aryl group include a phenyl group.

[0072] The alkyl group or aryl group may have a substituent. Examples of the substituent that the alkyl group may have include a phenyl group, an alkoxy group having 1 to 15 carbon atoms, and a hydroxy group. When the alkyl group has a substituent, the number of carbon atoms in the alkyl group does not include the number of carbon atoms in the substituent. Examples of the substituent that the aryl group may have include an alkyl group having 1 to 15 carbon atoms, a hydroxyalkyl group having 1 to 15 carbon atoms, an alkoxy group having 1 to 15 carbon atoms (preferably an alkoxy group having 1 to 8 carbon atoms, more preferably a methoxy group or an ethoxy group), and a phenylthio group.

[0073] In one aspect of this embodiment, the thermal cationic polymerization initiator A + B - A +is preferably a quaternary ammonium cation, and in the above formula (c-2), Y1, Y2, Y3, and Y4 are each preferably independently a linear, branched, or cyclic alkyl group having 1 to 20 carbon atoms, or an aryl group, and it is more preferable that two of Y1, Y2, Y3, and Y4 are each independently an aryl group which may have a substituent, and the remaining two are each independently an alkyl group having 1 to 15 carbon atoms (preferably an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms) which may have a substituent.

[0074] Examples of thermal cationic polymerization initiators include dimethylphenyl(4-methoxybenzyl)ammonium tetrakis(pentafluorophenyl)borate, dimethylphenyl(4-methylbenzyl)ammonium hexafluorotetrakis(pentafluorophenyl)borate, methylphenyldibenzylammonium tetrakis(pentafluorophenyl)borate, phenyltribenzylammonium tetrakis(pentafluorophenyl)borate, and dimethylphenyl(3,4-dimethylbenzyl)ammonium tetrakis(pentafluorophenyl)borate. Among these, dimethylphenyl(4-methoxybenzyl)ammonium tetrakis(pentafluorophenyl)borate is preferred. Commercially available products include, for example, CXC1821 (trade name, manufactured by King Industries).

[0075] The thermal cationic polymerization initiator may be used alone or in combination of two or more.

[0076] As another example of the tetrakis(pentafluorophenyl)borate compound as a thermal cationic polymerization initiator, the cationic A + may be a sulfonium ion in which at least one of the three groups bonded to S is an alkyl group. In this case, two groups may be combined to form an alkylene group to form a ring together with S. The remaining group is preferably an aryl group which may have a substituent, an alkyl group or an alkenyl group which may be substituted with an aryl, or the like.

[0077] Specifically, the following formula (c-3):

[0078] [ka] When expressed as S + R bonded to 1 , R 2 and R 3 At least one of these is an alkyl group.

[0079] Preferred cation A + In formula (c-3), R 1 represents an optionally substituted phenyl group or naphthyl group, R 2 represents an alkyl group having 1 to 8 carbon atoms, and R 3 represents an optionally substituted phenyl group or naphthyl group, an optionally substituted alkyl group, a cycloalkyl group, an optionally substituted alkenyl group, or a 2-indanyl group.

[0080] Specifically, R 1 represents an optionally substituted phenyl group or naphthyl group, which may have, as a substituent, an alkyl group having about 1 to 18 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, or hexyl; an alkoxy group having about 1 to 18 carbon atoms, such as methoxy, ethoxy, propyl, butoxy, hexyloxy, decyloxy, or dodecyloxy; a carbonyl group, such as acetoxy, propionyloxy, decylcarbonyloxy, dodecylcarbonyloxy, methoxycarbonyl, ethoxycarbonyl, or benzoyloxy; a phenylthio group; a halogen atom, such as fluorine, chlorine, bromine, or iodine; a cyano group; a nitro group; or a hydroxy group.

[0081] R 2 represents an alkyl group having 1 to 8 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, or hexyl.

[0082] R 3When is an optionally substituted phenyl group or naphthyl group, examples of the substituent include an alkyl group having about 1 to 18 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, or hexyl; an alkoxy group having about 1 to 18 carbon atoms, such as methoxy, ethoxy, propyl, butoxy, hexyloxy, decyloxy, or dodecyloxy; a carbonyl group, such as acetoxy, propionyloxy, decylcarbonyloxy, dodecylcarbonyloxy, methoxycarbonyl, ethoxycarbonyl, or benzoyloxy; a phenylthio group; a halogen atom, such as fluorine, chlorine, bromine, or iodine; a cyano group; a nitro group; and a hydroxy group.

[0083] R 3 When is an optionally substituted alkyl group, the number of carbon atoms in the alkyl chain is preferably 1 to 18, more preferably 1 to 12, and most preferably 1 to 6. The substituent may be an alkoxy group such as methoxy, ethoxy, propyl, butoxy, hexyloxy, decyloxy, or dodecyloxy; a carbonyl group such as acetoxy, propionyloxy, decylcarbonyloxy, dodecylcarbonyloxy, methoxycarbonyl, ethoxycarbonyl, or benzoyloxy; a phenylthio group; a halogen atom such as fluorine, chlorine, bromine, or iodine; a cyano group, a nitro group, a hydroxy group, or a phenyl group.

[0084] R 3 When is a cycloalkyl group, it is preferably one having 3 to 12 carbon atoms, and examples thereof include a cyclohexyl group, a cyclohexanonyl group, a cyclopentyl group, a 1-acenaphthenyl group, a bicyclononyl group, a norbornyl group, a coumarinyl group, a dihydrobenzofuranyl group, and a camphor group.

[0085] R 3When is an optionally substituted alkenyl group, the number of carbon atoms in the alkenyl chain is preferably 1 to 18, more preferably 1 to 12, and most preferably 1 to 6. The substituent may be an alkoxy group such as methoxy, ethoxy, propyl, butoxy, hexyloxy, decyloxy, or dodecyloxy; a carbonyl group such as acetoxy, propionyloxy, decylcarbonyloxy, dodecylcarbonyloxy, methoxycarbonyl, ethoxycarbonyl, or benzoyloxy; a phenylthio group; a halogen atom such as fluorine, chlorine, bromine, or iodine; a cyano group, a nitro group, a hydroxy group, or a phenyl group. 2-Alken-1-yl type alkenyl is particularly preferred.

[0086] Commercially available thermal cationic polymerization initiators having a cation represented by formula (c-3) include, for example, the San-Aid SI series (SI-B2A, SI-B7, SI-B3A, SI-B3, SI-B5, SI-B4) manufactured by Sanshin Chemical Industry Co., Ltd.

[0087] Other preferred cations A + is expressed as the following equation (c-4):

[0088] [ka]

[0089] where n is 1 to 3, and most preferably 2. 4 represents an optionally substituted phenyl group or naphthyl group, an optionally substituted alkyl group, a cycloalkyl group, an optionally substituted alkenyl group, or a 2-indanyl group. 3 Examples of the groups include those listed in the above.

[0090] The thermal cationic polymerization initiator may contain other thermal cationic polymerization initiators other than the tetrakis(pentafluorophenyl)borate compound as long as the effects of the present invention can be achieved. - PF6 - , AsF6- , BF4 - , B(aryl)4 - ions, etc. (excluding tetrakis(pentafluorophenyl)borate ions), and the cationic species A + Examples of the cationic species include those represented by the above formulae (c-2), (c-3) and (c-4).

[0091] Conventionally, antimony-containing compounds have been used as thermal cationic polymerization initiators to achieve low-temperature curing at 120°C or less, but antimony-containing compounds have the problem of being highly toxic and difficult to handle. However, the dual-cure adhesive composition of the present embodiment is capable of low-temperature curing without substantially containing an antimony-containing compound as a thermal cationic polymerization initiator, and is therefore low in toxicity and excellent in safety.

[0092] In this embodiment, the amount of the tetrakis(pentafluorophenyl)borate compound is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass, of the total mass (100% by mass) of the thermal cationic polymerization initiator. It is particularly preferable that the tetrakis(pentafluorophenyl)borate compound is a quaternary ammonium salt. Furthermore, in this embodiment, from the viewpoint of reducing toxicity, the smaller the content of the antimony-containing compound, the better. In this embodiment, the content of the antimony-containing compound is preferably 3% by mass or less, more preferably 1% by mass or less, and even more preferably 0% by mass, of the total mass (100% by mass) of the thermal cationic polymerization initiator.

[0093] The content of the thermal cationic polymerization initiator is not particularly limited, but the lower limit is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and the upper limit is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 3 parts by mass or less, relative to 100 parts by mass of the total content of the components (a1), (a2), and (a3).

[0094] <Component (d): Inorganic filler> One aspect of the dual-cure adhesive composition of this embodiment may contain an inorganic filler (also referred to as component (d)) in addition to the above-described components (a1) to (c). This allows the linear expansion coefficient of the dual-cure adhesive composition to be controlled. Examples of the inorganic filler (d) include silica fillers such as colloidal silica, hydrophobic silica, fine silica, and nanosilica, as well as acrylic beads, glass beads, urethane beads, bentonite, acetylene black, and ketjen black. Note that if the dual-cure adhesive composition of this embodiment contains a basic filler, it may be best not to use it because it will react with the cations generated from the polymerization initiator.

[0095] The average particle size of component (d) (or its maximum average particle size if not particulate) is not particularly limited, but is preferably 0.01 μm or more, as this results in excellent handling of the dual-cure adhesive composition. Furthermore, the average particle size of inorganic filler (d) (or its maximum average particle size if not particulate) is preferably 50 μm or less, as this results in uniform dispersion in the dual-cure adhesive composition. In the present invention, the average particle size of the inorganic filler is measured using a dynamic light scattering Nanotrac particle size analyzer.

[0096] Commercially available products of component (d) include high-purity synthetic spherical silica (product name "SO-E5", manufactured by Admatechs, average particle size: 2 μm; product name "SO-E2", manufactured by Admatechs, average particle size: 0.6 μm), silica (product name "FB7SDX", manufactured by Tatsumori, average particle size: 10 μm), and silica (product name "TS-10-034P", manufactured by Micron, average particle size: 20 μm).

[0097] The component (d) may be used singly or in combination of two or more.

[0098] The content of component (d) is not particularly limited, but the lower limit is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, and even more preferably 70 parts by mass or more, relative to 100 parts by mass of the total content of components (a1), (a2), and (a3), and the upper limit is preferably 200 parts by mass or less, more preferably 180 parts by mass or less, and even more preferably 150 parts by mass or less.

[0099] <Ingredient (e): Other ingredients> One aspect of the dual-cure adhesive composition of this embodiment may further contain other components, such as a thixotropic agent such as fumed silica, and various coupling agents such as silanes and titanates.

[0100] By including a thixotropic agent such as fumed silica in the composition, stringiness and spreading of the composition can be suppressed during application. Commercially available fumed silica products include Cab-O-Sil TS-720 and TS-530 manufactured by Cabot Corporation and Aerosil R974 manufactured by Nippon Aerosil Co., Ltd.

[0101] The silane coupling agent may have a vinyl group, an epoxy group, a styryl group, an acryloyl group, a methacryloyl group, an amino group, a ureido group, an isocyanate group, an isocyanurate group, a mercapto group, or the like. The silane coupling agent is not particularly limited, but examples thereof include γ-aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-glycidoxypropyltrimethoxysilane. Commercially available products include KBM-303, 402, 403, and KBE-402, 403 manufactured by Shin-Etsu Chemical Co., Ltd.

[0102] When the composition contains fumed silica, its content is not particularly limited, but is preferably 1 to 15 parts by mass, more preferably 1 to 7 parts by mass, per 100 parts by mass of the total content of components (a1), (a2), and (a3).When the composition contains a silane coupling agent, its content is not particularly limited, but is preferably 0.1 to 8 parts by mass, more preferably 0.2 to 5 parts by mass, per 100 parts by mass of the total content of components (a1), (a2), and (a3).

[0103] The composition of the present embodiment may further contain, as necessary, a colorant, a surfactant, a storage stabilizer, a plasticizer, a lubricant, an antifoaming agent, a leveling agent, a photosensitizer such as thioxanthone, and the like.

[0104] The composition may also contain a diluent for the epoxy compound. The diluent may be a known compound, such as vinyl ethers or polyols. Examples of vinyl ethers include mono- or polyfunctional vinyl ethers such as cyclohexanedimethanol divinyl ether, triethyleneglycol divinyl ether, and hydroxybutyl vinyl ether. Polyols not only function as a diluent but also improve adhesion in the resin system of the present invention. Examples include alkyl polyols, polyester polyols, polyether polyols, acrylic polyols, polybutadiene polyols, and phenolic polyols. Among these, alkyl polyols, polyester polyols, and polyether polyols are preferred, with polyether polyols being particularly preferred.

[0105] The dual-cure adhesive composition of this embodiment can be thermally cured at a high reactivity at low temperatures, and the cured product has a high glass transition temperature. For example, the composition preferably has a reactivity of 83% or more at 80°C (see the Examples for the calculation method), and the Tg of the cured product after photocuring and thermal curing is preferably 85°C or higher. The upper limit of the Tg of the cured product is not particularly limited, but is, for example, 150°C or lower.

[0106] The viscosity of the composition is not particularly limited, but it is preferably a paste at room temperature (about 25°C). From the viewpoint of ejection properties, the viscosity of the composition is preferably 10 Pa·s to 100 Pa·s at 25°C, and more preferably 20 Pa·s to 80 Pa·s. The viscosity of the composition at 25°C is measured using an E-type viscometer (cone angle 1.565°, rotation speed 5 rpm).

[0107] <Method for preparing dual-cure adhesive composition> The dual cure adhesive composition may be prepared by any method that can disperse and mix the various components described above. A typical method involves weighing the components, mixing and kneading them using a mixing machine, a mixing roll (such as a three-roll mill), a planetary mixer, or the like, and degassing as necessary to obtain the dual cure adhesive composition.

[0108] <Curing method> The method for curing the dual-cure adhesive composition of this embodiment preferably includes a photocuring step in which the composition is cured by light irradiation and a thermal curing step in which the composition is further post-cured by heating. By curing by light irradiation and then applying a thermal treatment, durability such as adhesion and water resistance is improved.

[0109] In the photo-curing step, the light to be irradiated preferably includes light in the wavelength range of 300 nm to 500 nm, and more preferably includes ultraviolet light with a wavelength of 400 nm or less (preferably 380 to 20 nm). Examples of light sources include, but are not limited to, ultraviolet LEDs, blue LEDs, white LEDs, lasers, metal halide lamps, xenon lamps, and high- or medium-pressure mercury lamps. The amount of light irradiation is not particularly limited, but preferably has an intensity of 0.1 to 1000 mW / cm at a wavelength of 365 nm. 2 The preferred range is 1 to 800 mW / cm 2 The light irradiation time is not particularly limited, but is, for example, 2 seconds to 5 minutes.

[0110] In the thermal curing step, the heating temperature is preferably 60° C. to 120° C., and more preferably 80° C. to 100° C. The heating time is not particularly limited, but is preferably, for example, 10 minutes to 4 hours.

[0111] <Application> In one aspect of this embodiment, the dual-cure adhesive composition can be used in a variety of fields. In the field of optical equipment, the dual-cure adhesive composition can be used as an adhesive for camera modules, LiDAR modules (light detection and ranging, including laser and infrared light), still camera lens materials, viewfinder prisms, target prisms, viewfinder covers, light-receiving sensor sections, photographic lenses, projection lenses for projection televisions, and the like. Examples of bonding locations in camera modules include between an image sensor (imaging element) such as a CMOS or CCD and a substrate, between a cut filter and a substrate, between a substrate and a housing, between a housing and a cut filter, and between a housing and a lens unit. In other fields, in the automotive and transportation fields, it can be used for bonding automotive switches, electrical components, etc.; in flat panel displays, it can be used for sealing and bonding liquid crystal displays, organic electroluminescence displays, light-emitting diode displays, and field emission displays, as well as ink materials; in the recording field, it can be used for bonding video discs, CDs, DVDs, MDs, pickup lenses, hard disk peripherals (spindle motor components, magnetic head actuator components, etc.), and Blu-ray discs; in the electronic materials field, it can be used for structural bonding and coating of electronic components; and in the optical components field, it can be used for sealing and bonding optical switch peripherals in optical communication systems, optical fiber materials around optical connectors, optical passive components, optical circuit components, and optoelectronic integrated circuit peripherals.

[0112] Adherends for which the dual-cure adhesive composition of this embodiment can be used include, for example, glass, various metals, porous members, and resin films and plates. Examples of the various metals include aluminum, nickel, iron, and stainless steel. Examples of the porous members include ceramic. Examples of resins that are raw materials for the resin films and plates include polycarbonate, PPS, PBT, PA, LCP, FR4, and FR5.

[0113] In a preferred embodiment, the dual-cure adhesive composition of the present invention is used for assembling a camera module. More specifically, the dual-cure adhesive composition of the present invention is preferably used in assembling a camera module to bond a lens holder to a substrate on which an imaging element is fixed. In the above, the camera module is not particularly limited and may be, for example, a small camera module used in a smartphone, an in-vehicle camera, or the like. [Example]

[0114] EXAMPLES Hereinafter, the present invention will be described in more detail and specifically using examples, but these examples do not limit the present invention in any way.

[0115] In the examples and comparative examples, the components blended into the dual-cure adhesive compositions are shown below.

[0116] Component (a1): Oxetane compound (a1-1) OXT-221 (product name, manufactured by Toagosei Co., Ltd.) Component (a2): Alicyclic epoxy compound (a2-1) Celoxide 2021P (product name, manufactured by Daicel Corporation) Component (a3): Aromatic glycidyl ether epoxy compound (a3-1) EPICLON EXA-850CRP (product name, manufactured by DIC Corporation)

[0117] Component (b): Photocationic polymerization initiator (b-1) CPI-200K (product name, manufactured by San-Apro Co., Ltd.)

[0118] Component (c): Thermal cationic polymerization initiator (c-1) CXC1821 (trade name, King Industries, dimethylphenyl(4-methoxybenzyl)ammonium tetrakis(pentafluorophenyl)borate) (c'-2) CXC1612 (trade name, King Industries, dimethylphenyl(4-methoxybenzyl)ammonium hexafluoroantimonate) (c'-3) TA100 (trade name, manufactured by San-Apro Ltd., structural formula represented by the following formula (c'-3))

[0119] [ka]

[0120] Component (d): inorganic filler (d-1) Spherical silica: SO-E5 (trade name, manufactured by Admatechs Co., Ltd.)

[0121] Ingredient (e) Other (e-1) Thixotropic agent: Cabo-Sil TS720 (trade name, manufactured by Cabot) (e-2) Silane coupling agent: KBM403 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd., 3-glycidoxypropyltrimethoxysilane)

[0122] <Preparation of Composition> The components (a1-1) to (e-2) were blended in the proportions shown in Table 1 and kneaded and dispersed using a three-roll mill to prepare dual-cure adhesive compositions for each of the Examples and Comparative Examples.

[0123] The dual-cure adhesive compositions obtained were evaluated as follows, and the results are shown in Table 1.

[0124] <Light curing> 50 mg of each composition was placed on a glass plate and irradiated with 365 nm UV-LED (500 mW / cm 2 The coating was irradiated for 5 seconds using a Panasonic UV irradiator UJ35, and then poked with a skewer and evaluated according to the following criteria. Table 1 shows the results of UV curing. ◯: No adhesion of the composition to the bamboo skewer was observed. ×: Adhesion of the composition to the bamboo skewer was observed.

[0125] <Thermal curing reaction rate> 10 mg of each composition was placed in an oven at 80°C for 1 hour to allow for thermal curing. Calorimetry was performed on each of the compositions before and after curing using a DSC6220 (temperature range: 30-150°C, heating rate: 5°C / min). From the DSC curves obtained, the cumulative calorific value of the composition before curing and the residual cumulative calorific value of the cured product after curing were calculated. Based on these cumulative calorific values, the reaction rate was calculated using the following formula: Reaction rate (%) = 100 x (cumulative heat generation of the composition before curing - residual cumulative heat generation of the cured product) / cumulative heat generation of the composition before curing

[0126] <Glass transition temperature (Tg)> The adhesive composition was applied to a release film to a thickness of 2 mm, and then 365 nm UV-LED (500 mW / cm) was used. 2 After irradiating the sample with UV light for 5 seconds, the sample was cured in a hot air circulating oven at 80°C for 1 hour. The cured product was thermally analyzed using a TMA (TMA / SS6100, thermomechanical analyzer) in compression mode (load 49 mN) at a heating rate of 5°C / min to measure its Tg.

[0127] [Table 1]

[0128] Comparative Example 1 shows the results for a composition using a conventionally used antimony-containing compound (which is toxic) as the thermal cationic polymerization initiator. On the other hand, Examples 1 to 6 and Comparative Examples 2 to 9 show the results for a composition using a quaternary ammonium salt of tetrakis(pentafluorophenyl)boric acid, which has low toxicity, as the thermal cationic polymerization initiator. By varying the blending amounts of components (a1), (a2), and (a3) ​​as shown in Table 1, Examples 1 to 6 achieved high UV curability, low-temperature curing reactivity, and cured product Tg. These results indicate physical properties comparable to or not significantly inferior to those of Comparative Example 1. Comparative Examples 4 to 6 did not achieve sufficient UV curability due to the low amount of oxetane compound (component (a1)). Furthermore, the blending ratios of Comparative Examples 1 to 3 and Comparative Examples 7 to 9 resulted in significantly inferior results for at least one of the low-temperature curing reactivity and Tg. Comparative Example 10 used a compound represented by formula (c'-3) as the thermal cationic polymerization initiator, but the low-temperature curing reactivity was lower than that of the Examples.

[0129] The above results indicate that when a tetrakis(pentafluorophenyl)borate compound is used as an antimony-free thermal cationic polymerization initiator and components (a1), (a2), and (a3) ​​are included in the specified blending amounts, a dual-cure adhesive composition can be obtained that has excellent low-temperature curing properties and a high Tg of the cured product.

[0130] As is clear from the above, various modifications are possible with respect to the dual-cure adhesive composition without departing from the spirit of the present invention. Therefore, the embodiments described herein are merely examples, and the scope of the present invention as defined in the claims is not limited thereto. [Industrial Applicability]

[0131] The present invention can provide a dual-cure adhesive composition suitable for assembling camera modules, etc.

Claims

1. Component (a1): an oxetane compound containing a compound represented by the following formula (a1-1), Component (a2): an alicyclic epoxy compound containing a compound represented by the following formula (1); Component (a3): an aromatic glycidyl ether epoxy compound including a bisphenol A epoxy compound; Component (b): a photocationic polymerization initiator; Component (c): a thermal cationic polymerization initiator containing a tetrakis(pentafluorophenyl)borate compound; Component (e): a silane coupling agent A dual cure adhesive composition comprising: With respect to 100 parts by mass of the total of the components (a1), (a2), and (a3), The content of the component (a1) is 20 to 94 parts by mass, The content of the component (a2) is 3 to 55 parts by mass, a dual-cure adhesive composition in which the content of the component (a3) ​​is 3 to 45 parts by mass; 。

2. The dual-cure adhesive composition of claim 1, wherein component (c) is an ammonium salt of tetrakis(pentafluorophenyl)borate.

3. The dual-cure adhesive composition according to claim 1 or 2, wherein component (b) is a salt represented by A + B - , where A + is an aromatic iodonium ion or an aromatic sulfonium ion, and B - is at least one selected from the group consisting of PF 6 - , [(Rf) b PF 6-b ] - (where Rf represents an alkyl group in which 80% or more of the hydrogen atoms are substituted with fluorine atoms, and b represents the number of alkyl groups and is an integer from 1 to 5; Rf may be the same or different), AsF 6 - , and BF 4 - .

4. A dual-cure adhesive composition described in any one of claims 1 to 3, further comprising component (d) an inorganic filler.

5. A dual-cure adhesive composition described in any one of claims 1 to 4, which does not contain an antimony-containing compound.

6. For a total of 100 parts by mass of the components (a1), (a2) and (a3), The content of the component (b) is 0.5 parts by mass or more and 10 parts by mass or less, The dual-cure adhesive composition according to any one of claims 1 to 5, wherein the content of component (c) is 0.1 parts by mass or more and 10 parts by mass or less.

7. A dual-cure adhesive composition described in any one of claims 1 to 6, used for assembling a camera module.

8. A dual-cure adhesive composition described in any one of claims 1 to 7, used in assembling a camera module to bond a lens holder to a substrate on which an imaging element is fixed.

9. A cured product obtained by curing the dual-cure adhesive composition described in any one of claims 1 to 8.

10. A camera module comprising the cured product described in claim 9.

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