JP4999043B2 - Sulfonium salt compound, cationic polymerization initiator and thermosetting composition - Google Patents

Description

  The present invention relates to a sulfonium salt compound, a cationic polymerization initiator, and a thermosetting composition. More specifically, the present invention relates to a novel sulfonium salt compound, and a cationic polymerization initiator and a thermosetting composition using the same.

  The cationic polymerizable initiator has a function of receiving an energy such as heat and light to generate an acid and curing a cationic polymerizable compound such as an epoxy compound, and a sulfonium salt compound is used.

で表わされる２−ヒドロキシエチルスルホニウム塩が具体的に例示されている。特許文献１のスルホニウム塩化合物は、カチオン重合性化合物を短時間で硬化させる特徴を有する。また、特許文献２の請求項１には、トリフルオロメタンスルホン酸アニオンを対イオンに用いた芳香族スルホニウム塩化合物が開示されている。特許文献２には、当該スルホニウム塩化合物は、対イオンにトリフルオロメタンスルホン酸アニオンを用いることで結晶性が向上し、熱や光に対して良好な安定性を有する旨、記載されている。
特開平７−１２６３１３号公報 特開２００４−２１７５５１号公報 For example, in claim 1 of Patent Document 1, R ₁ S ⁺ R ₂ R ₃ X ⁻ (wherein R ₁ represents an alkyl group having a phenyl group or an ester group which may be substituted at the α-position of a sulfur atom; ₂ and R ₃ each represents an optionally substituted alkyl group, and X represents SbF ₆ , AsF ₆ , PF ₆ or BF ₄ ), and a sulfonium salt compound represented by No. 1 in Table 1 of this document. 3 includes the following formula:

The 2-hydroxyethylsulfonium salt represented by these is specifically illustrated. The sulfonium salt compound of Patent Document 1 has a feature of curing a cationic polymerizable compound in a short time. Further, claim 1 of Patent Document 2 discloses an aromatic sulfonium salt compound using a trifluoromethanesulfonate anion as a counter ion. Patent Document 2 describes that the sulfonium salt compound is improved in crystallinity by using a trifluoromethanesulfonate anion as a counter ion and has good stability to heat and light.
JP-A-7-126313 JP 2004-217551 A

  Although the cationic polymerizable compound can be cured in a short time by the sulfonium salt compound described in Patent Document 1, the cationic polymerizable curable composition is required to have an appropriate curing behavior depending on its use. It is not always preferable to cure the cationically polymerizable compound in a short time. Especially for thermosetting compositions such as interlayer insulating films for printed circuit boards, insulating films for multilayer boards, optical films, protective films for displays, etc., when a high degree of flatness is required for the cured product, When embedding the unevenness of a substrate with unevenness with a cured product, a polymerization initiator that gives rapid curing is not necessarily suitable. This is because it is considered that the gel state during curing improves the reflow property and contributes to flattening. Therefore, what gives the hardening behavior which has time in a gel state is preferable to what gives rapid hardening. Further, if the compatibility with the cationic polymerizable compound is insufficient, unevenness of curing occurs and the flatness is affected. Therefore, those having sufficient compatibility are preferable. For these reasons, a sulfonium salt compound that gives a curing behavior with good reflow properties and good compatibility with a cationically polymerizable compound is desired.

  Accordingly, an object of the present invention is to provide a sulfonium salt compound capable of giving a curing behavior with good reflow property to a cationic polymerizable thermosetting composition, and a cationic polymerization initiator and a thermosetting composition using the sulfonium salt compound. There is to do.

  As a result of intensive studies to solve the above problems, the present inventors have found that when a sulfonium salt compound having a specific structure is used as a cationic polymerization initiator, the thermosetting composition exhibits a curing behavior with good reflow properties. As a result, the present invention has been completed.

（式中、Ａはエチレン基、Ｒ^１およびＲ^２はそれぞれ独立に炭素数１〜８のアルキル基、 または下記一般式（２）、

（式中、Ａ^１はメチレン基、環Ｂはベンゼン環、Ｒ^３は炭素数１〜４のアルキル基、ｎは０または１である。）で表される基であり、Ｘ⁻は、有機スルホン酸アニオン、またはテトラキスアリールホウ素アニオンであり、Ｒ ^１ およびＲ ^２ の少なくとも一方は一般式（２）で表される基である。）で表されることを特徴とするものである。 That is, the sulfonium salt compound of the present invention has the following general formula (1),

(In the formula, A is an ethylene group , R ¹ and R ² are each independently an alkyl group having 1 to 8 carbon atoms, or the following general formula (2),

(Wherein, A ¹ is a methylene group , ring B is a benzene ring, R ³ is an alkyl group having 1 to 4 carbon atoms, and n is 0 or 1 ), and X ⁻ is an organic group . sulfonate anion, or the Ri tetrakis aryl boron anion der, at least one of R ¹ and R ² is a group represented by the general formula (2). ).

  The cationic polymerization initiator of the present invention is the above-described sulfonium salt compound of the present invention.

  Furthermore, the thermosetting composition of the present invention is characterized by containing the cationic polymerization initiator and the cationic polymerizable compound of the present invention.

  The sulfonium salt compound of the present invention functions as a cationic polymerization initiator that gives a cationically polymerizable thermosetting composition good curing behavior with good reflow properties.

で表され、カチオン重合開始剤として有用である。上記一般式（１）において、Ａは炭素数１〜４のアルカンジイル基であり、例えば、−ＣＨ₂−、−ＣＨ₂−ＣＨ₂−、−ＣＨ₂−ＣＨ₂−ＣＨ₂−、−ＣＨ（ＣＨ₃）−ＣＨ₂−、−ＣＨ₂−ＣＨ（ＣＨ₃）−、−Ｃ（ＣＨ₃）₂−、−ＣＨ₂−ＣＨ₂−ＣＨ₂−ＣＨ₂−、−ＣＨ（ＣＨ₃）−ＣＨ₂−ＣＨ₂−、−ＣＨ₂−ＣＨ（ＣＨ₃）−ＣＨ₂−、−ＣＨ₂−ＣＨ₂−ＣＨ（ＣＨ₃）−、−ＣＨ（ＣＨ₃）−ＣＨ（ＣＨ₃）−、−Ｃ（ＣＨ₃）₂−ＣＨ₂−、−ＣＨ₂−Ｃ（ＣＨ₃）₂−が挙げられる。 The sulfonium salt compound of the present invention has the following general formula (1),

And is useful as a cationic polymerization initiator. In the general formula (1), A is an alkanediyl group having 1 to 4 carbon atoms, _{e.g., -CH 2 -, - CH 2} -CH 2 -, - CH 2 -CH 2 -CH 2 -, - CH _{(CH 3) -CH 2 -,} - CH 2 -CH (CH 3) -, - C (CH 3) 2 -, - CH 2 -CH 2 -CH 2 -CH 2 -, - CH (CH 3) - _{CH 2 -CH 2 -, - CH} 2 -CH (CH 3) -CH 2 -, - CH 2 -CH 2 -CH (CH 3) -, - CH (CH 3) -CH (CH 3) -, - C (CH ₃ ) ₂ —CH ₂ —, —CH ₂ —C (CH ₃ ) ₂ — may be mentioned.

で表される基であり、Ｒ¹およびＲ²は、連結してテトラヒドロチオフェン環を形成してもよい。炭素数１〜８のアルキル基としては、メチル、エチル、プロピル、イソプロピル、ブチル、第２ブチル、第３ブチル、イソブチル、アミル、イソアミル、第３アミル、ヘキシル、２−ヘキシル、３−ヘキシル、シクロヘキシル、１−メチルシクロヘキシル、ヘプチル、２−ヘプチル、３−ヘプチル、イソヘプチル、第３ヘプチル、ｎ−オクチル、イソオクチル、第３オクチル、２−エチルヘキシル等が挙げられる。 In the general formula (1), R ¹ and R ² are each independently an alkyl group having 1 to 8 carbon atoms, or the following general formula (2),

R ¹ and R ² may be linked to form a tetrahydrothiophene ring. Examples of the alkyl group having 1 to 8 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, secondary butyl, tertiary butyl, isobutyl, amyl, isoamyl, tertiary amyl, hexyl, 2-hexyl, 3-hexyl, and cyclohexyl. 1-methylcyclohexyl, heptyl, 2-heptyl, 3-heptyl, isoheptyl, tertiary heptyl, n-octyl, isooctyl, tertiary octyl, 2-ethylhexyl and the like.

In the general formula (2), A ¹ represents alkanediyl group having 1 to 4 carbon atoms include the same groups as those exemplified in the above A. Ring B is a benzene ring or naphthalene ring, R ³ is an alkyl group having 1 to 4 carbon atoms, and examples thereof include methyl, ethyl, propyl, isopropyl, butyl, secondary butyl, tertiary butyl, and isobutyl. n is an integer of 0-5.

In the general formula (1), those in which an aromatic ring is directly bonded to S ⁺ are slow to cure and have poor light stability when used as a cationic initiator by thermal curing. Moreover, since compatibility with a cationically polymerizable compound may deteriorate, it is not preferable.

In the sulfonium salt compound represented by the general formula (1) of the present invention, A is ethylene, R ¹ and R ² are each independently methyl, benzyl or 4-methylphenylmethyl, or R ¹ and R ² are linked. The group that forms a tetrahydrothiophene ring is preferable because it can be obtained at low cost and in high yield without impairing the function of the present invention.

Specific examples of the cation component of the sulfonium salt compound of the present invention include the following cation Nos. 1-19 are mentioned.

In the general formula (1), the anion represented by X ⁻ is an organic sulfonate anion, an organic sulfonimide anion, or a tetrakisaryl boron anion. These anions give a curing behavior with good reflowability. For example, a halogen anion, a boron tetrafluoride anion, an antimony hexafluoride anion, and a phosphorus hexafluoride anion cannot be given sufficient reflow properties because they cure quickly.

  Organic sulfonate anions include trifluoromethanesulfonate anion, pentafluoroethanesulfonate anion, heptafluoropropanesulfonate anion, nonafluorobutanesulfonate anion, undecafluoropentanesulfonate anion, tridecafluorohexanesulfonate anion, Pentadecafluoroheptanesulfonate anion, heptadecafluorooctanesulfonate anion, p-toluenesulfonate anion, benzenesulfonate anion, dodecylbenzenesulfonate anion, naphthalenesulfonate anion, anthracenesulfonate anion, acenaphthenesulfonate anion, Phenanthrenesulfonate anion, camphorsulfonate anion, methanesulfonate anion, ethanesulfonic acid Nion, propanesulfonate anion, butanesulfonate anion, pentanesulfonate anion, hexanesulfonate anion, heptanesulfonate anion, octanesulfonate anion, norbornenesulfonate anion, adamantanesulfonate anion, cyclohexanesulfonate anion, diphenylamine-4 -Sulfonic acid anion, 2-amino-4-methyl-5-chlorobenzenesulfonic acid anion, 2-amino-5-nitrobenzenesulfonic acid anion, and the like. As organic sulfonimide anion, bis (trifluoromethanesulfone) imide anion Bis (pentafluoroethanesulfone) imide anion, bis (heptafluoropropanesulfone) imide anion, bis (nonafluorobutanesulfone) Amide anion, bis (undecafluoropentanesulfone) imide anion, bis (pentadecafluoroheptanesulfone) imide anion, bis (tridecafluorohexanesulfone) imide anion, bis (heptadecafluorooctanesulfone) imide anion, (trifluoromethanesulfone) ) (Nonafluorobutanesulfone) imide anion, (methanesulfone) (trifluoromethanesulfone) imide anion, etc., and tetrakisarylboron anion includes tetraphenylboron anion, tetrakis (4-fluorophenyl) boron anion, tetrakis ( Pentafluorophenyl) boron anion and the like.

  As the above-mentioned anion component, the organic sulfonate anion is preferable because it takes a long time in a gel state and the curing behavior is easily controlled, and the trifluoromethanesulfonate anion is more preferable because it provides excellent stability.

In the sulfonium salt compound of the present invention, the production method is not particularly limited, and a method applying a well-known organic synthesis reaction can be used. For example, a salt compound for introducing a thioether compound, a halogenated organic compound, and an anion component X ⁻ can be obtained as a starting material. Specifically, a compound represented by HO-ASR ¹ , a compound represented by Cl—R ² , and a compound represented by M ⁺ X ⁻ (M is an alkali metal) (A, R ¹ , R ² and X ⁻ can be obtained by reacting with the same chemical species as in the general formula (1). In addition, a compound represented by R ¹ SR ² , a compound represented by HO—A—Cl, and a compound represented by M ⁺ X ⁻ (A, R ¹ , R ² , X ⁻ are represented by the above general formula (Represents the same chemical species as (1)).

  The cationic polymerization initiator of the present invention is the sulfonium salt compound of the present invention, and the thermosetting composition of the present invention comprises the cationic polymerization initiator of the present invention and a curable component. As a composition containing a cationically polymerizable compound and being cured by thermal energy. In addition to the cationic polymerization initiator and the cationic polymerizable compound, which are essential components, an optional component such as a solvent or dispersion medium, a polymerizable compound other than the cationic polymerizable compound, and various additives may be contained.

  Examples of the cationic polymerizable compound that is an essential component of the thermosetting composition of the present invention include epoxy compounds, phenol compounds, aldehyde compounds, vinyl ether compounds, styrene compounds, cyclic ether compounds, lactone compounds, episulfide compounds, silicones, and the like. Examples of the compound include one or a mixture of two or more so as to obtain a cured product by cationic polymerization.

  Various organic solvents can be used as the solvent or dispersion medium, which is an optional component in the thermosetting composition of the present invention. Examples of the organic solvent include alcohol solvents, polyol solvents, ketone solvents, ester solvents, ether solvents, polyether solvents, aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents, chlorine solvents. , A hydrocarbon solvent having a cyano group, a pyrrolidone solvent, and the like. These may be used alone or in combination of two or more.

  Examples of the polymerizable compound other than the cationic polymerizable compound which is an optional component in the thermosetting composition of the present invention include radical polymerizable compounds represented by acrylate compounds, methacrylate compounds, and olefin compounds.

  In addition, various additives that are optional components in the thermosetting composition of the present invention include benzotriazole-based, triazine-based, and benzoate-based ultraviolet absorbers; phenol-based, phosphorus-based, sulfur-based antioxidants; cationic interfaces. Antistatic agent comprising activator, anionic surfactant, nonionic surfactant, amphoteric surfactant, etc .; halogen compound, phosphate ester compound, phosphate amide compound, melamine compound, fluororesin or metal Flame retardants such as oxides, (poly) phosphate melamine, (poly) phosphate piperazine; hydrocarbons, fatty acids, aliphatic alcohols, aliphatic esters, aliphatic amides or metal soaps; dyes , Pigments, colorants such as carbon black; fumed silica, fine particle silica, silica, diatomaceous earth, clay, kaolin, diatomaceous earth, Silica-based inorganic additives such as licagel, calcium silicate, sericite, kaolinite, flint, feldspar powder, aragonite, attapulgite, talc, mica, minnesotite, pyrophyllite, silica and the like; fillers such as glass fiber and calcium carbonate; Examples include nucleating agents, crystallization agents such as crystallization accelerators, silane coupling agents, and the like.

  When the amount of the cationic polymerization initiator used in the thermosetting composition of the present invention is less than 0.01 parts by mass relative to 100 parts by mass of the cationic polymerizable compound, curing may be insufficient. If it exceeds 1, the curing is accelerated and the reflow property improvement which is the effect of the present invention cannot be obtained, so 0.01 to 10 parts by mass is preferable, and 0.1 to 5 parts by mass is more preferable.

  In addition, the amount of the solvent or dispersion medium, polymerizable compound other than the cationic polymerizable compound, and optional components such as various additives with respect to 100 parts by mass of the cationic polymerizable compound is generally 0 to 10,000 parts by mass of the solvent or dispersion medium. The polymerizable compound other than the cationic polymerizable compound is 0 to 100 parts by mass, and the various additives are 0 to 10 parts by mass in each component, and the total is 0 to 100 parts by mass.

  Applications of the thermosetting composition of the present invention include ink, protective film (protective layer), paint, adhesive, insulating material, structural material, optical film, FRP, resist and the like. In particular, it is useful as an optical film, specifically as an optical film for liquid crystal or plasma display, and more specifically as a color filter protective film for plasma display, antireflection film, light diffusion film, film sealant, film adhesive, polarizing plate protection It is useful as a film, an antistatic film, a hard coat film, and an optical waveguide clad.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, it is not limited to these.
Synthesis example 1
Cation No. Preparation of 6 trifluoromethanesulfonate salt In a 500 ml reaction flask, 0.54 mol of 2- (methylthio) ethanol, 0.54 mol of 1-chloromethyl-4-methylbenzene, 100 g of methanol, 0.60 of lithium trifluoromethanesulfonate Mole was charged and stirred at 25 ° C. for 24 hours. Next, methanol was removed under reduced pressure, and 100 g of methylene chloride was added to the resulting residue. This was washed with 100 g of water three times, and then the methylene chloride was removed under reduced pressure to obtain white crystals in a yield of 73%. The obtained white crystal was analyzed by ¹ H-NMR, ¹⁹ F-NMR (400 MHz, deuterated chloroform solvent), MALDI TOFMASS, IR, and confirmed to be the target product.

(result of analysis)
・¹ H-NMR (chemical shift; H number; peak)
(7.29-7.38; 4; d) (4.58-4.72; 2; d) (4.00-3.41; 4; m) (2.81; 3; s) (2 .36; 3; s)
¹⁹ F-NMR (chemical shift; F number; peak)
(75.2; 3; s)
・ MALDI TOFASS
Cation mass: 197.6 (theoretical value: 197.3)
Anion mass: 150.0 (theoretical 149.1)
IR (unit: cm ^-1 )
3242, 3186, 3037, 2942, 1602, 1586, 1503, 1457, 1440, 1422, 1366, 1286, 1212, 1187, 1164, 1089, 1023, 983, 924, 878, 834, 819, 771, 760, 720

Synthesis example 2
Cation No. Production of camphorsulfonate of No. 6 A colorless liquid was obtained in a yield of 56% by performing the same operation as in Synthesis Example 1 except that lithium trifluoromethanesulfonate was changed to lithium camphorsulfonate. The obtained liquid was analyzed in the same manner as in Synthesis Example 1 to confirm that it was the target product.

(result of analysis)
・¹ H-NMR (chemical shift; H number; peak)
(7.18-7.43; 4; d) (4.76-4.92; 2; d) (4.09-4.11; 2; t) (3.63-3.77; 2; m) (3.28-3.31; 1; d) (2.95; 3; s) (2.71-2.81; 1; d) (2.62-2.69; 1; m) (2.34; 3; s) (2.32-2.25; 1; m) (2.04-1.94; 2; m) (1.88-1.83; 1; d) (1 .75-1.68; 1; m) (1.39-1.32; 1; m) (1.07; 3; s) (0.81; 3; s)
・ MALDI TOFASS
Cation mass: 198.2 (theoretical value: 197.3)
Anion mass: 231.7 (theoretical value 231.3)
IR (unit: cm ^-1 )
3312, 2957, 2929, 2886, 1741, 1615, 1516, 1456, 1417, 1387, 1373, 1288, 1185, 1171, 1067, 1038, 823, 788, 731

Synthesis example 3
Cation No. 6 Preparation of tetrakis (pentafluorophenyl) boron salt The target product was obtained by the same operation as in Synthesis Example 1 except that lithium trifluoromethanesulfonate was changed to lithium tetrakis (pentafluorophenyl) boron.

Synthesis example 4
Cation No. Production of 10 trifluoromethanesulfonate salt The target product could be obtained by performing the same operation as in Synthesis Example 1 except that 2- (methylthio) ethanol was changed to 2- (4-methylphenylmethylthio) ethanol.

Synthesis example 5
Cation No. 5 Preparation of trifluoromethanesulfonate 1-chloromethyl-4-methylbenzene was changed to chloromethylbenzene, and the same procedure as in Synthesis Example 1 was performed to obtain the desired product.

Synthesis Example 6
Cation No. Preparation of 4 trifluoromethanesulfonate salt A 500 ml reaction flask was charged with 0.54 mol of tetrahydrothiophene, 0.54 mol of 2-chloroethanol, 100 g of methanol, and 0.60 mol of lithium trifluoromethanesulfonate, and 24 hours at 25 ° C. Stir. Subsequently, methanol was removed under reduced pressure, 100 g of methylene chloride was added thereto, and the resulting methylene chloride composition was washed with 100 g of water three times, and then the methylene chloride was removed under reduced pressure to obtain the desired product.

Examples 1-3, Comparative Examples 1 and 2
The cation No. obtained in Synthesis Example 1 was added to 100 parts by mass of a bisphenol A type epoxy resin (Adeka Resin EP-4100; manufactured by Asahi Denka Kogyo Co., Ltd.). No. 6 trifluoromethanesulfonate, the cation No. obtained in Synthesis Example 2. No. 6 camphor sulfonate, the cation No. obtained in Synthesis Example 3. 1 part by mass of 6 tetrakis (pentafluorophenyl) boron salt was added as a cationic polymerization initiator to obtain thermosetting compositions 1 to 3 of Examples.

  The cation No. was added to 100 parts by mass of a bisphenol A type epoxy resin (Adeka Resin EP-4100; manufactured by Asahi Denka Kogyo Co., Ltd.). 6 parts of an antimony hexafluoride salt as a cationic polymerization initiator was added to obtain a thermosetting composition 1 for comparison. In addition, 1 part by mass of 4-hydroxyphenyldimethylsulfonium trifluoromethanesulfonate as a cationic polymerization initiator was added to 100 parts by mass of bisphenol A type epoxy resin (Adeka Resin EP-4100; manufactured by Asahi Denka Kogyo Co., Ltd.) for comparison. The thermosetting composition 2 was obtained.

  About the obtained thermosetting composition, gelation time (tg) and hardening time (ts) were measured, and the time of the gel state was obtained by ts-tg. The test method was a method in which 0.5 g of the thermosetting composition was weighed in an aluminum pan having a diameter of 3 cm and heated on a hot plate heated to 200 ° C. The time until the viscosity of the specimen started to increase by visual inspection and palpation with a spatula was defined as gelation time (tg), and the time until tack-free by palpation with a spatula was determined as the curing time (ts). The obtained results are shown in Table 1.

  From Table 1 above, the thermosetting compositions 1 to 3 (Examples 1 to 3) using the sulfonium salt compound of the present invention as a cationic polymerization initiator have time to maintain a certain gel state. This indicates that the reflow property is good and a flat cured product is obtained. Comparative compound 1 (Comparative Example 1) has a short time to gelation (tg), but also has a short curing time (ts), and does not have sufficient gel state time to obtain reflow properties. Moreover, since the comparative thermosetting composition 2 (Comparative Example 2) has a long tg and ts, it is inefficient.

Examples 4 and 5, Comparative Example 3
The cation No. obtained in Synthesis Example 1 was added to 100 parts by mass of a bisphenol A type epoxy resin (Adeka Resin EP-4100; manufactured by Asahi Denka Kogyo Co., Ltd.). 6 parts of trifluoromethanesulfonate as a cationic polymerization initiator was added to obtain thermosetting composition 4. The cation No. obtained in Synthesis Example 2 was added to 100 parts by mass of bisphenol A type epoxy resin (Adeka Resin EP-4100; manufactured by Asahi Denka Kogyo Co., Ltd.). 6 parts of camphor sulfonate as a cationic polymerization initiator was added to obtain thermosetting composition 5. Further, 100 parts by mass of bisphenol A type epoxy resin (Adeka Resin EP-4100; manufactured by Asahi Denka Kogyo Co., Ltd.) was added to the cation No. 0.5 parts by mass of 6 antimony hexafluoride salt as a cationic polymerization initiator was added to obtain a comparative thermosetting composition 3.

  Using the obtained thermosetting composition, differential thermal analysis measurement was carried out under the conditions of 50 ml / min, 40 ° C. to 300 ° C. and 5 ° C./min temperature increase in a nitrogen stream, and the shapes of DTA peaks were compared. The thermosetting composition 4 (Example 4) had an exothermic peak showing a curing reaction at 110 ° C. to 160 ° C., and the peak width was 50 ° C. The thermosetting composition 5 (Example 5) had an exothermic peak showing a curing reaction at 143 ° C. to 240 ° C., and the peak width was 97 ° C. On the other hand, the comparative thermosetting composition 3 (Comparative Example 3) had an exothermic peak showing a curing reaction at 100 ° C. to 130 ° C., and the peak width was 30 ° C. From this result, the thermosetting compositions 4 and 5 (Examples 4 and 5), which are the sulfonium salts of the present invention having a broad peak, have a mild thermosetting behavior and exhibit reflowability from gelation to curing. It is suggested that there is a margin of time or thermosetting conditions sufficient to improve. On the other hand, it is suggested that the comparative thermosetting composition 3 (Comparative Example 3) having a sharp peak has a fast time from gelation to curing and cannot obtain sufficient reflowability.

Claims (5)

The following general formula (1),

(In the formula, A is an ethylene group , R ¹ and R ² are each independently an alkyl group having 1 to 8 carbon atoms, or the following general formula (2),

(Wherein, A ¹ is a methylene group , ring B is a benzene ring, R ³ is an alkyl group having 1 to 4 carbon atoms, and n is 0 or 1 ), and X ⁻ is an organic group . sulfonate anion, or the Ri tetrakis aryl boron anion der, at least one of R ¹ and R ² is a group represented by the general formula (2). A sulfonium salt compound represented by the formula: Wherein R ¹ is methyl, wherein R ² is benzyl or 4-methylphenyl methylation in a claim 1 sulfonium salt compound according. The sulfonium salt compound according to claim 1 or 2, wherein X ^- is an organic sulfonate anion.   A cationic polymerization initiator, which is the sulfonium salt compound according to any one of claims 1 to 3.   A thermosetting composition comprising the cationic polymerization initiator according to claim 4 and a cationic polymerizable compound.