WO2024150765A1

WO2024150765A1 - Adhesive composition, adhesive film for circuit connection, connection structure, and method for producing connection structure

Info

Publication number: WO2024150765A1
Application number: PCT/JP2024/000306
Authority: WO
Inventors: 裕太山崎; 克彦富坂; 敏光森谷; 勝将宮地; 亮太小林
Original assignee: 株式会社レゾナック
Priority date: 2023-01-12
Filing date: 2024-01-10
Publication date: 2024-07-18
Also published as: JP2024099206A

Abstract

An adhesive composition according to the present invention contains a cationically polymerizable compound and a curing agent. The cationically polymerizable compound contains an epoxy compound having three or more functional groups and an epoxy equivalent weight of more than 100 g/eq to 250 g/eq. The curing agent contains a pyridinium salt, the pyridinium salt has a benzyl group at position 1 and an electron withdrawing group at position 2, and the benzyl group has an electron donating group. An adhesive film for circuit connection according to the present invention comprises an adhesive layer formed from the adhesive composition.

Description

Adhesive composition, adhesive film for circuit connection, connection structure, and method for producing the connection structure

The present disclosure relates to an adhesive composition, an adhesive film for circuit connection, a connection structure, and a method for manufacturing the connection structure.

Conventionally, various adhesive materials have been used to connect circuits. For example, adhesive films with conductive particles dispersed in the adhesive have been used as adhesive materials for connecting a liquid crystal display and an integrated circuit for driving the liquid crystal, connecting a liquid crystal display and a tape carrier package (TCP), connecting a flexible printed circuit board (FPC) and a TCP, or connecting an FPC and a printed wiring board (see, for example, Patent Document 1).

JP 2014-084400 A

From a practical standpoint, it is desirable for an adhesive film to be usable for mounting over a wide range of temperatures, from low to high.

In addition, in recent years, there has been an increase in the level of demand for the connection reliability of assembly bodies to which adhesive films are applied. To improve connection reliability, the assembly body is required to have HAST resistance, which means that the adhesive film is unlikely to peel off even after harsh tests such as HAST (Highly Accelerated Stress Test), and there is little generation of air bubbles.

Therefore, one aspect of the present disclosure aims to provide an adhesive composition that can be mounted at low temperatures (e.g., 120°C) to high temperatures (e.g., 150°C), and that has excellent appearance even after HAST testing and produces little air bubbles in both low-temperature and high-temperature mounting. Another aspect of the present disclosure aims to provide an adhesive composition, an adhesive film for circuit connection, a connection structure, and a method for manufacturing a connection structure that use the adhesive composition.

One aspect of the present disclosure includes the following [1] to [13].
[1] A composition comprising a cationically polymerizable compound and a curing agent,
the cationically polymerizable compound contains an epoxy compound which is tri- or higher functional and has an epoxy equivalent of more than 100 g/eq and not more than 250 g/eq,
the curing agent contains a pyridinium salt;
The pyridinium salt has a benzyl group at the 1-position and an electron-withdrawing group at the 2-position;
The adhesive composition, wherein the benzyl group has an electron donating group.
[2] The adhesive composition according to [1], wherein the epoxy compound has an aromatic ring.
[3] The adhesive composition according to [1] or [2], wherein the epoxy compound is solid at room temperature.
[4] The adhesive composition according to any one of [1] to [3], wherein the cationically polymerizable compound comprises at least one selected from the group consisting of an epoxy compound having a trisphenolmethane structure, an epoxy compound having a bisphenol structure and having a glycidyl group and a glycidyloxy group, an epoxy compound having a tetravalent organic group and an aromatic ring bonded to the organic group, wherein the aromatic ring has a substituent containing an epoxy group, and an epoxy compound having a naphthalene structure.
[5] The adhesive composition according to any one of [1] to [4], wherein the electron-withdrawing group is a cyano group or a halogeno group.
[6] The adhesive composition according to any one of [1] to [5], wherein the electron donating group is an alkyl group or an alkoxy group.
[7] The number of the electron-donating groups in the benzyl group is 3,
The adhesive composition according to any one of [1] to [6], wherein the electron donating group is an alkyl group.
[8] The pyridinium salt comprises a pyridinium cation and an anion,
The adhesive composition according to any one of [1] to [7], wherein the anion is B(C ₆ F ₅ ) ₄ ^-- .
[9] The adhesive composition according to any one of [1] to [8], further comprising conductive particles.
[10] An adhesive film for circuit connection, comprising an adhesive layer formed from the adhesive composition according to any one of [1] to [9].
[11] A first adhesive layer and a second adhesive layer laminated on the first adhesive layer,
An adhesive film for circuit connection, wherein at least one of the first adhesive layer and the second adhesive layer is a layer formed from the adhesive composition according to any one of [1] to [9].
[12] A first circuit member having a first electrode;
a second circuit member having a second electrode;
a connection portion disposed between the first circuit member and the second circuit member, electrically connecting the first electrode and the second electrode to each other;
Equipped with
A connection structure, wherein the connection portion comprises a cured product of the adhesive film for circuit connection according to [10] or [11].
[13] A method for producing a connection structure, comprising the steps of: interposing an adhesive film for circuit connection according to [10] or [11] between a first circuit member having a first electrode and a second circuit member having a second electrode; and thermocompressing the first circuit member and the second circuit member to electrically connect the first electrode and the second electrode to each other.

According to one aspect of the present disclosure, it is possible to provide an adhesive composition that can be mounted at low temperatures (e.g., 120°C) to high temperatures (e.g., 150°C) and that can achieve an excellent appearance even after HAST testing in both low-temperature and high-temperature mounting. In addition, according to another aspect of the present disclosure, it is possible to provide an adhesive composition, an adhesive film for circuit connection, a connection structure, and a method for manufacturing a connection structure that use the adhesive composition.

FIG. 1 is a schematic cross-sectional view showing one embodiment of an adhesive film for circuit connection. FIG. 1 is a schematic cross-sectional view showing one embodiment of an adhesive film for circuit connection. FIG. 1 is a schematic cross-sectional view showing one embodiment of a connection structure. 4A to 4C are schematic cross-sectional views showing a method for manufacturing the connection structure of FIG. 3.

The following describes in detail the embodiments of the present disclosure. Note that the present disclosure is not limited to the following embodiments.

In the numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with the values shown in the examples. In addition, the lower and upper limits of the numerical ranges may be arbitrarily combined with the lower or upper limit of other numerical ranges. In the expression of a numerical range "A to B", the numerical values A and B at both ends are included as the lower and upper limits of the numerical range, respectively. In this specification, for example, the description "10 or more" means 10 and a numerical value exceeding 10, and this also applies when the numerical values are different. In addition, for example, the description "10 or less" means a numerical value less than 10 and a numerical value less than 10, and this also applies when the numerical values are different. In addition, each component and material exemplified in this specification may be used alone or in combination of two or more types, unless otherwise specified. In this specification, the content of each component in the composition means the total amount of the multiple substances present in the composition, unless otherwise specified, when multiple substances corresponding to each component are present in the composition. In addition, in this specification, "(meth)acrylate" means at least one of an acrylate and the corresponding methacrylate. In addition, in this specification, "epoxy group" includes substituents that contain an epoxy group in the structure, such as a glycidyl group and a glycidyloxy group.

<Adhesive Composition>
One embodiment of the present disclosure is an adhesive composition containing a cationically polymerizable compound and a curing agent. The cationically polymerizable compound contains at least an epoxy compound that is trifunctional or higher and has an epoxy equivalent of more than 100 g/eq and 250 g/eq or less. The curing agent contains at least a pyridinium salt, the pyridinium salt having a benzyl group at the 1-position and an electron-withdrawing group at the 2-position, and the benzyl group has an electron-donating group.

(Cationically polymerizable compound)
The cationic polymerizable compound may be, for example, a compound that reacts with a curing agent by heating to crosslink, and includes at least an epoxy compound that is trifunctional or more and has an epoxy equivalent of more than 100 g/eq and 250 g/eq or less (such an epoxy compound is also referred to as "epoxy compound X"). An epoxy compound that is trifunctional or more means an epoxy compound having three or more epoxy groups. The epoxy equivalent means a value measured in accordance with JIS K7236.

The reason why the cationic polymerizable compound contains epoxy compound X and the adhesive composition has excellent appearance and generates less air bubbles is presumed to be as follows. That is, when the number of epoxy groups in the epoxy compound is 3 or more and the epoxy equivalent is 250 g/eq or less, the crosslinking density of the adhesive composition is high, the adhesion to the substrate is improved, and the appearance is excellent even after the HAST test. In addition, when the adhesive composition is made into a film, tack of the film can be suppressed and air bubbles that get between the substrate and the film when the film is attached can be easily removed, thereby suppressing the generation of air bubbles.

The number of epoxy groups in the epoxy compound X may be 4 or more, or 15 or less, 12 or less, 10 or less, 8 or less, 6 or less, or 4 or less.

The epoxy equivalent of the epoxy compound X may be 105 g/eq or more, 110 g/eq or more, 120 g/eq or more, 130 g/eq or more, 140 g/eq or more, or 150 g/eq or more, and may be 240 g/eq or less, 230 g/eq or less, 220 g/eq or less, 210 g/eq or less, or 200 g/eq or less.

Epoxy compound X may have an aromatic ring. When epoxy compound X has an aromatic ring and the epoxy equivalent is within a specific range, the epoxy compound has a rigid skeleton, so that an adhesive composition can be obtained that has a better appearance even after the HAST test and generates less air bubbles.

Epoxy compound X may be a solid at room temperature (25°C). When epoxy compound X is a solid at room temperature and has an epoxy equivalent within a specific range, it is easier to achieve an excellent appearance even after the HAST test and to reduce the generation of bubbles, compared to epoxy compounds that are liquid at room temperature.

The molecular weight of the epoxy compound X may be 200 or more, 250 or more, or 300 or more, and may be 1500 or less, 1000 or less, 900 or less, 800 or less, 700 or less, or 650 or less.

Examples of epoxy compound X include epoxy compounds having a trisphenolmethane structure (hereinafter, such epoxy compounds are also referred to as "compound A"), epoxy compounds having a bisphenol structure and having a glycidyl group and a glycidyloxy group (hereinafter, such epoxy compounds are also referred to as "compound B"), epoxy compounds having a tetravalent organic group and an aromatic ring bonded to the organic group, the aromatic ring having a substituent containing an epoxy group (hereinafter, such epoxy compounds are also referred to as "compound C"), and epoxy compounds having a naphthalene structure (hereinafter, such epoxy compounds are also referred to as "compound D").

Compound A may be a compound represented by the following general formula (1A), from the viewpoint of more easily achieving an excellent appearance even after the HAST test and from the viewpoint of less generation of bubbles.

[In formula (1A), R ¹¹ , R ¹² , and R ¹³ each independently represent a hydrogen atom or an organic group, at least one of R ¹¹ , R ¹² , and R ¹³ represents an organic group having an epoxy group, R ¹⁴ represents a hydrogen atom or an alkyl group, and R ¹⁵ represents a hydrogen atom or an organic group.]

Examples of the organic group represented by R ¹¹ , R ¹² , and R ¹³ include an alkyl group, an alkyl ether group, and an alkenyl group. These organic groups may have a substituent. The number of carbon atoms of the organic group may be, for example, 2 or more, or 3 or more, and may be 8 or less, 6 or less, or 4 or less. At least one of R ¹¹ , R ¹² , and R ¹³ may be an organic group having a glycidyl group, or may be an organic group having a glycidyloxy group. R ¹¹ , R ¹² , and R ¹³ may be the same or different. R ¹¹ , R ¹² , and R ¹³ may be an organic group having a glycidyl group, or may be an organic group having a glycidyloxy group, from the viewpoint of more easily achieving an excellent appearance even after the HAST test and less generation of bubbles.

When R ¹⁴ is an alkyl group, the alkyl group may be, for example, a methyl group, an ethyl group, or a propyl group. The alkyl group may have a substituent. R ¹⁴ may be a hydrogen atom from the viewpoint of more easily achieving an excellent appearance even after the HAST test and from the viewpoint of less generation of bubbles.

The organic group represented by R ¹⁵ may be, for example, an alkyl group, an alkyl ether group, or an alkenyl group. The organic group may have a substituent. R ¹⁵ may be an alkyl group, an alkyl group having a substituent, or an alkyl group having a phenyl group, from the viewpoint of more easily realizing an excellent appearance even after the HAST test and less occurrence of bubbles. The phenyl group may have a substituent, for example, an epoxy group, a glycidyl group, or a glycidyloxy group. R ¹⁵ may be an alkyl group having a phenyl group having a glycidyloxy group, from the viewpoint of more easily realizing an excellent appearance even after the HAST test and less occurrence of bubbles.

The number of epoxy groups contained in compound A may be 15 or less, 12 or less, or 10 or less.

Specifically, compound A may be a compound represented by the following formula (2A).

[In formula (2A), k represents an integer of 1 to 3.]

Compound B may be a compound represented by the following general formula (1B), from the viewpoint of more easily achieving an excellent appearance even after the HAST test and from the viewpoint of less generation of bubbles.

[In formula (1B), R ²¹ , R ²² , R ²³ , and R ²⁴ each independently represent a hydrogen atom, an organic group, an organic group having a glycidyl group, or an organic group having a glycidyloxy group, at least one of R ²¹ , R ²² , R ²³ , and R ²⁴ represents an organic group having a glycidyl group, at least one of R ²¹ , R ²² , R ²³ , and R ²⁴ represents an organic group having a glycidyloxy group, and R ²⁵ and R ²⁶ each independently represent a hydrogen atom or an organic group.]

Examples of the organic group represented by ^R21 , ^R22 , ^R23 , and ^R24 include an alkyl group, an alkyl ether group, and an alkenyl group. These organic groups may have a substituent. The number of carbon atoms of the organic group may be, for example, 2 or more, or 3 or more, and may be 8 or less, 6 or less, or 4 or less.

R ²¹ , R ²² , R ²³ , and R ²⁴ may be the same or different. From the viewpoint of more easily realizing an excellent appearance even after the HAST test and less generation of bubbles, R ²¹ and R ²² may be different from each other, and one of R ²¹ and R ²² may be an organic group having a glycidyl group, and the other may be an organic group having a glycidyloxy group. From the viewpoint of more easily realizing an excellent appearance even after the HAST test and less generation of bubbles, R ²³ and R ²⁴ may be different from each other, and one of R ²³ and R ²⁴ may be an organic group having a glycidyl group, and the other may be an organic group having a glycidyloxy group.

When R ²⁵ and/or R ²⁶ are organic groups, examples of the organic groups include alkyl groups, aryl groups, alkyl ether groups, and alkenyl groups. These organic groups may have a substituent. The alkyl group may be, for example, a methyl group, an ethyl group, or a propyl group. The alkyl group may have a substituent. R ²⁵ and R ²⁶ may be a hydrogen atom, an alkyl group, or a methyl group from the viewpoint of more easily achieving an excellent appearance even after the HAST test and less generation of bubbles.

The number of epoxy groups contained in compound B may be 4 or more, or 10 or less, 8 or less, 6 or less, or 4 or less.

Compound B may be a compound having multiple glycidyl groups and multiple glycidyloxy groups, from the viewpoint of more easily achieving an excellent appearance even after the HAST test and from the viewpoint of less generation of bubbles.

Specifically, compound B may be a compound represented by the following formula (2B).

Compound C may have four aromatic rings bonded to a tetravalent organic group, and each of the four aromatic rings may have an epoxy group, from the viewpoint of more easily achieving an excellent appearance even after the HAST test and less generating bubbles. In this case, the four aromatic rings may be different from each other, or may be the same from the viewpoint of more easily achieving an excellent appearance even after the HAST test and less generating bubbles. Compound C may be, for example, a compound represented by the following general formula (1C).

[In formula (1C), R ³¹ represents a tetravalent organic group, and R ³² represents an organic group having an epoxy group.]

Examples of the organic group represented by R ³¹ include an alkyl group, an alkyl ether group, and an alkenyl group. These organic groups may have a substituent. The number of carbon atoms of the organic group may be, for example, 2 or more, or 3 or more, and may be 8 or less, 6 or less, 4 or less, or 3 or less. R ³¹ may be an alkyl group or an ethyl group from the viewpoint of more easily achieving an excellent appearance even after the HAST test and less generation of bubbles.

R ³² may be an organic group having a glycidyl group or an organic group having a glycidyloxy group. From the viewpoint of more easily realizing an excellent appearance even after the HAST test and from the viewpoint of less generation of bubbles, R ³² may be an organic group having a glycidyloxy group.

The number of epoxy groups possessed by compound C may be 4 or more, or 10 or less, 8 or less, 6 or less, or 4 or less.

Specifically, compound C may be a compound represented by the following formula (2C).

Compound D may be a compound represented by the following general formula (1D), from the viewpoint of more easily achieving an excellent appearance even after the HAST test and from the viewpoint of less generation of bubbles.

[In formula (1), X ⁴¹ represents an oxygen atom, a sulfur atom, or an alkylene group having 1 to 10 carbon atoms, R ⁴² and R ⁴³ each independently represent a glycidyl group or a glycidyloxy group, m and n each independently represent an integer of 1 to 7, and m+n is 3 or greater.]

X ⁴¹ may have a substituent. When X ⁴¹ is an alkylene group, the number of carbon atoms of the alkylene group may be 8 or less, 6 or less, 4 or less, 3 or less, or 2 or less, from the viewpoint of more easily realizing an excellent appearance even after the HAST test and from the viewpoint of less occurrence of bubbles. X ⁴¹ may be an ethylene group, from the viewpoint of more easily realizing an excellent connection resistance even after the HAST test and from the viewpoint of less occurrence of bubbles.

Compound C may be a compound represented by the following formula (2D), from the viewpoint of more easily realizing an excellent appearance even after the HAST test and less generation of bubbles.

[In formula (2D), R ⁴⁴ , R ⁴⁵ , R ⁴⁶ and R ⁴⁷ each independently represent a hydrogen atom, a glycidyl group, or a glycidyloxy group, and three or more of R ⁴⁴ , R ⁴⁵ , R ⁴⁶ and R ⁴⁷ are a glycidyl group or a glycidyloxy group.]

In formula (2D), from the viewpoint of more easily achieving an excellent appearance even after the HAST test and less generation of bubbles, all of R ⁴⁴ , R ⁴⁵ , R ⁴⁶ and R ⁴⁷ may be a glycidyl group or a glycidyloxy group.

The cationic polymerizable compound may contain any one of compounds A to D alone, or may contain two or more of compounds A to D. The cationic polymerizable compound may contain at least one selected from the group consisting of an epoxy compound having a trisphenolmethane structure, an epoxy compound having a bisphenol structure and a glycidyl group and a glycidyloxy group, an epoxy compound having a tetravalent organic group and an aromatic ring bonded to the organic group, the aromatic ring having a substituent containing an epoxy group, and an epoxy compound having a naphthalene structure.

The cationic polymerizable compound may contain, in addition to compounds A to D, cationic polymerizable compounds other than compounds A to D. Examples of cationic polymerizable compounds other than compounds A to D include epoxy compounds (excluding compounds A to D), vinyl ether compounds, and oxetane compounds.

Examples of epoxy compounds (excluding compounds A to D) include bisphenol A type epoxy resins, bisphenol S type epoxy resins, bisphenol F type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, bisphenol A novolac type epoxy resins, bisphenol F novolac type epoxy resins, tetramethyl bisphenol A type epoxy resins, 3',4'-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (bi-7-oxabicyclo[4,1,0]heptane), 3,4-epoxycyclohexylmethyl (meth)acrylate, (3,3',4,4'-diepoxy)bicyclohexyl, dicyclopentadiene dimethanol diglycidyl ether, xylene novolac type glycidyl ether, biphenyl type epoxy resins, etc. The epoxy compound may contain at least one selected from the group consisting of bisphenol A type epoxy resin, tetramethyl bisphenol A type epoxy resin, dicyclopentadiene dimethanol diglycidyl ether, xylene-novolac type glycidyl ether, and alicyclic epoxy resin. The epoxy compound may contain a glycidyl ether compound. From the viewpoint of further improving low-temperature curing properties, the epoxy compound may contain an alicyclic epoxy resin. Furthermore, from the viewpoint of easily achieving both low-temperature curing properties and good storage stability, the epoxy compound does not need to contain an alicyclic epoxy resin.

The cationic polymerizable compound may contain an epoxy compound having two or less functionalities (hereinafter, such an epoxy compound is also referred to as "epoxy compound Y") together with the epoxy compound X. By containing the epoxy compound Y together with the epoxy compound X in the cationic polymerizable compound, the crosslink density can be adjusted.

The epoxy equivalent of epoxy compound Y may be 100 g/eq or more, more than 100 g/eq, 110 g/eq or more, 120 g/eq or more, 140 g/eq or more, or 160 g/eq or more, and may be 300 g/eq or less, 250 g/eq or less, 220 g/eq or less, or 200 g/eq or less.

The ratio of the content of epoxy compound Y to the content of epoxy compound X (content of epoxy compound Y/content of epoxy compound X) may be 0.1 or more, 0.2 or more, 0.5 or more, or 0.8 or more, and may be 10 or less, 8 or less, 6 or less, 4 or less, 2 or less, or 1.5 or less.

As the oxetane compound, any compound having one or more oxetane ring structures in the molecule can be used without any particular restrictions. From the viewpoint of further improving low-temperature curing properties, the cationic polymerizable compound may contain an oxetane compound. Furthermore, from the viewpoint of easily achieving both low-temperature curing properties and good storage stability, the cationic polymerizable compound may not contain an oxetane compound. The cationic polymerizable compound may contain an epoxy compound (excluding compound X) and an oxetane compound together with compound X. Furthermore, from the viewpoint of easily achieving both low-temperature curing properties and good storage stability, the cationic polymerizable compound may contain only one of an epoxy compound (excluding compound X) and an oxetane compound. The case where only one of an epoxy compound (excluding compound X) and an oxetane compound is contained includes the case where, as the cationic polymerizable compound, a single type selected from an epoxy compound other than compound X and an oxetane compound is used together with compound X, and the case where a cationic polymerizable compound such as a vinyl ether compound is used in combination with a type selected from an epoxy compound other than compound X and an oxetane compound is used together with compound X.

Examples of oxetane compounds include xylylene bisoxetane, 2-ethylhexyl oxetane, 3-hydroxymethyl-3-methyl oxetane, 3-hydroxymethyl-3-ethyl oxetane, 3-hydroxymethyl-3-propyl oxetane, 3-hydroxymethyl-3-n-butyl oxetane, 3-hydroxymethyl-3-phenyl oxetane, 3-hydroxymethyl-3-benzyl oxetane, 3-hydroxyethyl-3-methyl oxetane, 3-hydroxyethyl-3-ethyl oxetane, and 3-hydroxyethyl 3-propyloxetane, 3-hydroxyethyl-3-phenyloxetane, 3-hydroxypropyl-3-methyloxetane, 3-hydroxypropyl-3-ethyloxetane, 3-hydroxypropyl-3-propyloxetane, 3-hydroxypropyl-3-phenyloxetane, 3-hydroxybutyl-3-methyloxetane, 4,4'-bis[(3-ethyl-3-oxetanyl)methoxymethyl]biphenyl, and 3-ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane.

The content of the cationic polymerizable compound may be 10 mass% or more, 20 mass% or more, 30 mass% or more, or 35 mass% or more based on the total mass of the adhesive composition, from the viewpoint of ensuring sufficient curability of the adhesive composition. The content of the cationic polymerizable compound may be 70 mass% or less, 60 mass% or less, 50 mass% or less, or 45 mass% or less based on the total mass of the adhesive composition, from the viewpoint of ensuring formability of the adhesive composition.

The content of the epoxy compound (including compounds A to D) in the cationic polymerizable compound may be 50% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more based on the total mass of the cationic polymerizable compound, from the viewpoint of more easily achieving an excellent appearance even after the HAST test and from the viewpoint of less generation of air bubbles. The content of the epoxy compound (including compounds A to D) in the cationic polymerizable compound may be substantially 100% by mass (an embodiment in which the cationic polymerizable compound is composed of the epoxy compound (including compounds A to D)).

The total content of epoxy compound X in the cationic polymerizable compound may be 10% by mass or more, 20% by mass or more, 30% by mass or more, or 40% by mass or more based on the total mass of the cationic polymerizable compound, from the viewpoint of more easily achieving an excellent appearance even after the HAST test and from the viewpoint of less generation of bubbles. The total content of epoxy compound X in the cationic polymerizable compound may be 90% by mass or less, 80% by mass or less, 70% by mass or less, or 60% by mass or less based on the total mass of the cationic polymerizable compound.

The total content of compounds A to D in the cationic polymerizable compound may be 10% by mass or more, 20% by mass or more, 30% by mass or more, or 40% by mass or more based on the total mass of the cationic polymerizable compound, from the viewpoint of more easily achieving an excellent appearance even after the HAST test and from the viewpoint of less generation of bubbles. The total content of compounds A to D in the cationic polymerizable compound may be 90% by mass or less, 80% by mass or less, 70% by mass or less, or 60% by mass or less based on the total mass of the cationic polymerizable compound.

(Hardening agent)
The curing agent contains a pyridinium salt having a benzyl group at position 1 and an electron-withdrawing group at position 2, with the benzyl group having an electron-donating group (hereinafter, such a pyridinium salt is also referred to as "pyridinium salt A"). By containing an epoxy compound X as a cationic polymerizable compound and pyridinium salt A as a curing agent, an adhesive composition can be obtained that is mountable from low temperatures (e.g., 120°C) to high temperatures (e.g., 150°C), and that has excellent appearance even after HAST testing and generates little air bubbles in both low-temperature and high-temperature mounting.

The pyridinium salt A may be, for example, a compound represented by the following general formula (3):

[In formula (1), R ¹ represents an electron-withdrawing group, R ² represents an electron-donating group, and X ⁻ represents an anion.]

The electron-withdrawing group that pyridinium salt A has at the 2-position may be a cyano group, a halogeno group, a nitro group, a carbonyl group, a carboxy group, a sulfo group, etc. The halogeno group may be a fluoro group, a chloro group, a bromo group, an iodo group, etc. From the viewpoint of increasing the activity of the curing agent and curing the adhesive composition in a shorter time, the electron-withdrawing group may be a cyano group or a halogeno group, or may be a cyano group or a chloro group. Pyridinium salt A may contain an electron-withdrawing group other than the potential-withdrawing group located at the 2-position. The number of electron-withdrawing groups that pyridinium salt A has may be 3 or less, 2 or less, or 1.

The electron donating group of the benzyl group arranged at the 1-position of the pyridinium salt A may be an alkyl group, an alkoxy group, a hydroxyl group, an amino group, or an alkylamino group. Examples of the alkyl group include a methyl group, an ethyl group, a normal propyl group, and an isopropyl group. Examples of the alkoxy group include a methoxy group and an ethoxy group. From the viewpoint of increasing the activity of the curing agent and curing the adhesive composition in a shorter time, the electron withdrawing group may be an alkyl group or an alkoxy group, or a methyl group or a methoxy group. The benzene ring may contain multiple electron donating groups, and the number of electron donating groups of the benzyl group arranged at the 1-position of the pyridinium salt A may be 1 or more, 2 or more, or 3 or more, or may be 3. The benzyl group arranged at the 1-position of the pyridinium salt A may have at least one electron donating group at the 4-position (the 4-position when the bonding position of the benzyl group to the pyridine ring is the 1-position. The para-position to the bonding position of the benzyl group to the pyridine ring).

When the number of electron donating groups possessed by the benzyl group arranged at the 1st position of the pyridinium salt A is 3, all of the three electron donating groups may be alkyl groups or may be methyl groups. When the bonding position of the benzyl group to the pyridine ring is the 1st position, the pyridinium salt A may have an alkyl group as an electron donating group at each of the 2nd, 4th, and 6th positions of the benzyl group. By containing a pyridinium salt in which the number of electron donating groups possessed by the benzyl group arranged at the 1st position of the pyridinium salt A is 3 and all of the electron donating groups are alkyl groups (or methyl groups), an adhesive film using such a curing agent has excellent physical properties (e.g., elastic modulus). Therefore, an adhesive film using such a curing agent can achieve, for example, excellent adhesion to circuit members and excellent peelability of the substrate from the adhesive film. In addition, an adhesive film using such a curing agent has, for example, excellent storage stability, and even when the adhesive film is stored for a certain period of time (for example, 15 hours at 40°C), it is easy to maintain excellent adhesion to circuit members and excellent peelability of the substrate from the adhesive film. The reason for this is believed to be that the benzyl group located at position 1 of pyridinium salt A has three electron-donating groups, which results in a well-balanced structure that maintains low-temperature curing properties while preventing deterioration during storage for a certain period of time (e.g., 15 hours at 40°C) (excellent storage stability).

Examples of the pyridinium cation of pyridinium salt A include 2-cyano-1-(4-methoxybenzyl)pyridinium cation, 2-chloro-1-(4-methoxybenzyl)pyridinium cation, 2-bromo-1-(4-methoxybenzyl)pyridinium cation, 2-cyano-1-(4-methylbenzyl)pyridinium cation, 2-chloro-1-(4-methylbenzyl)pyridinium cation, 2-bromo-1-(4-methylbenzyl)pyridinium cation, 2-cyano-1-(2,4,6-trimethylbenzyl)pyridinium cation, 2-chloro-1-(2,4,6-trimethylbenzyl)pyridinium cation, and 2-bromo-1-(2,4,6-trimethylbenzyl)pyridinium cation. From the viewpoint of being able to cure the adhesive composition in a shorter time, the pyridinium cation of the pyridinium salt A may be at least one selected from the group consisting of 2-cyano-1-(4-methoxybenzyl)pyridinium cation, 2-chloro-1-(4-methoxybenzyl)pyridinium cation, 2-cyano-1-(2,4,6-trimethylbenzyl)pyridinium cation, and 2-chloro-1-(2,4,6-trimethylbenzyl)pyridinium cation.

Examples of the anion of pyridinium salt A include SbF ₆ ^- , PF ₆ ^- , PF _X (CF ₃ ) _6-X ^- (wherein X is an integer of 1 to 5), BF ₄ ^- , B(C ₆ F ₅ ) ₄ ^- , RSO ₃ ^- (wherein R is an alkyl group having 1 to 3 carbon atoms, or a substituted or unsubstituted aryl group), C(SO ₂ CF ₃ ) ₃ ^- , N(SO ₂ CF ₃ ) ₂ ^- , O(SO ₂ CF ₃ ) ^- , and B(C ₆ H ₃ (CF ₃ ) ₂ ) ₄ ^- (wherein the CF ₃ group is substituted at the 3- and 5-positions of the phenyl group). The anion of the pyridinium salt A may be B(C ₆ F ₅ ) ₄ ^— , from the viewpoint of excellent connection resistance even after a high temperature and high humidity test (eg, 85° C., 85% RH, 250 hours).

The pyridinium salt A may be a compound that combines the pyridinium cation and the anion. That is, the pyridinium salt A may contain at least any of the pyridinium cations and any of the anions. From the viewpoint of being able to cure the adhesive composition in a shorter time, the pyridinium salt A may be at least one selected from the group consisting of 2-cyano-1-(4-methoxybenzyl)pyridinium tetrakis(pentafluorophenyl)borate, 2-chloro-1-(4-methoxybenzyl)pyridinium tetrakis(pentafluorophenyl)borate, 2-cyano-1-(2,4,6-trimethylbenzyl)pyridinium tetrakis(pentafluorophenyl)borate, and 2-chloro-1-(2,4,6-trimethylbenzyl)pyridinium tetrakis(pentafluorophenyl)borate.

The content of pyridinium salt A in the curing agent may be 80% by mass or more, 90% by mass or more, or 95% by mass or more, based on the total mass of the curing agent, and may be 100% by mass (an embodiment in which the curing agent is essentially composed of pyridinium salt A).

The curing agent may contain a pyridinium salt other than pyridinium salt A. The content of pyridinium salt other than pyridinium salt A in the curing agent may be 20 mass% or less, 10 mass% or less, or 5 mass% or less based on the total mass of the curing agent, or may be 0 mass% (an embodiment in which the curing agent is essentially composed of pyridinium salt A).

A curing agent containing pyridinium salt A can be obtained by a manufacturing method including the steps of reacting at least one of a pyridine compound having an electron-withdrawing group at the 2-position, a benzyl chloride compound having an electron-donating group, or a benzyl bromide compound having an electron-donating group with an alkali metal iodide salt (e.g., sodium iodide) in a solvent (e.g., acetonitrile) to obtain pyridinium iodide having a pyridine ring and a benzene ring, and reacting the obtained pyridinium iodide with an anion salt in a solvent (e.g., dichloromethane) to obtain pyridinium salt A.

The pyridine compound having an electron-withdrawing group at the 2-position may be a pyridine compound having the above-mentioned electron-withdrawing group at the 2-position, and may be, for example, 2-cyanopyridine or 2-chloropyridine.

The benzyl chloride compound having an electron donating group may be a benzyl chloride compound having the above electron donating group, for example, 4-methoxybenzyl chloride, 2,4,6-trimethylbenzyl chloride. The benzyl bromide compound having an electron donating group may be a benzyl bromide compound having the above electron donating group, for example, 4-methoxybenzyl bromide, 2,4,6-trimethylbenzyl bromide.

The anion salt may be any compound capable of introducing the anion possessed by pyridinium salt A, and may be, for example, a lithium salt, sodium salt, potassium salt, or cesium salt of the anion of pyridinium salt A.

In the step of obtaining pyridinium iodide, the reaction may be carried out, for example, at room temperature (20 to 30°C). The reaction time may be, for example, 10 to 50 hours, or 20 to 30 hours. After completion of the reaction, the obtained pyridinium iodide may be washed with acetone, distilled water, etc., and vacuum dried to remove the solvent used.

In the process of obtaining pyridinium iodide, the yield of pyridinium iodide may be 40% or more, 55% or more, 70% or more, or 80% or more. The yield of pyridinium iodide is defined as the ratio of the amount of pyridinium iodide actually obtained to the maximum amount of pyridinium iodide that can be obtained from the raw materials used in the synthesis of pyridinium iodide.

In the step of obtaining pyridinium salt A, the reaction may be carried out, for example, at room temperature (20 to 30°C). The reaction time may be, for example, 1 to 15 hours or 1 to 5 hours. After completion of the reaction, the obtained pyridinium salt A may be washed with acetone, distilled water, etc., and vacuum dried to remove the solvent used.

In the step of obtaining pyridinium salt A, the yield of pyridinium salt A may be 70% or more, 80% or more, or 85% or more. The yield of pyridinium salt A is the ratio of the amount of pyridinium salt A actually obtained to the maximum amount of pyridinium salt A that can be obtained from the pyridinium iodide used in the synthesis of pyridinium salt A.

The fact that pyridinium salt A has been obtained can be confirmed by measuring the obtained compound by nuclear magnetic resonance spectroscopy ( ¹ H-NMR). Specifically, it can be confirmed by the method described in the Examples below.

The content of the curing agent in the adhesive composition may be 1 mass% or more, 2 mass% or more, 3 mass% or more, 4 mass% or more, or 5 mass% or more, based on the total mass of the adhesive composition, from the viewpoint of sufficiently promoting the curing reaction. The content of the curing agent in the adhesive composition may be 20 mass% or less, 15 mass% or less, 10 mass% or less, 8 mass% or less, or 6 mass% or less, based on the total mass of the adhesive composition, from the viewpoint of improving the physical properties of the cured product. From these viewpoints, the content of the curing agent in the adhesive composition may be 1 to 20 mass%, based on the total mass of the adhesive composition.

The content of the curing agent in the adhesive composition may be 1 mass% or more, 3 mass% or more, 5 mass% or more, or 7 mass% or more, based on the total mass of the adhesive composition excluding the conductive particles, from the viewpoint of sufficiently promoting the curing reaction. The content of the curing agent in the adhesive composition may be 30 mass% or less, 25 mass% or less, 20 mass% or less, 15 mass% or less, or 10 mass% or less, based on the total mass of the adhesive composition excluding the conductive particles, from the viewpoint of improving the physical properties of the cured product. From these viewpoints, the content of the curing agent in the adhesive composition may be 1 to 30 mass%, based on the total mass of the adhesive composition excluding the conductive particles.

The content of the curing agent in the adhesive composition may be 1 mass% or more, 3 mass% or more, 5 mass% or more, or 7 mass% or more, based on the total mass of the adhesive composition excluding the conductive particles and filler, from the viewpoint of sufficiently promoting the curing reaction. The content of the curing agent in the adhesive composition may be 30 mass% or less, 25 mass% or less, 20 mass% or less, 15 mass% or less, or 10 mass% or less, based on the total mass of the adhesive composition excluding the conductive particles and filler, from the viewpoint of improving the physical properties of the cured product. From these viewpoints, the content of the curing agent in the adhesive composition may be 1 to 30 mass%, based on the total mass of the adhesive composition excluding the conductive particles and filler.

The content of the curing agent in the adhesive composition may be 1 part by mass or more, 5 parts by mass or more, 8 parts by mass or more, 10 parts by mass or more, or 12 parts by mass or more, based on 100 parts by mass of the cationically polymerizable compound, from the viewpoint of sufficiently promoting the curing reaction. The content of the curing agent in the adhesive composition may be 40 parts by mass or less, 30 parts by mass or less, 20 parts by mass or less, 18 parts by mass or less, or 16 parts by mass or less, based on 100 parts by mass of the cationically polymerizable compound, from the viewpoint of improving the physical properties of the cured product. From these viewpoints, the content of the curing agent in the adhesive composition may be 1 to 40 parts by mass, based on 100 parts by mass of the cationically polymerizable compound.

(Conductive particles)
The adhesive composition may contain conductive particles. The conductive particles are not particularly limited as long as they are conductive particles, and examples thereof include metal particles made of metals such as gold, silver, palladium, nickel, copper, and solder; conductive carbon particles made of conductive carbon; and coated conductive particles having a core containing non-conductive glass, ceramic, plastic (polystyrene, etc.), and a coating layer containing the above metal or conductive carbon and coating the core. The conductive particles may be coated conductive particles, which are easily deformed by heating and/or pressure, and can increase the contact area between the electrodes and the conductive particles when electrically connecting the electrodes, thereby further improving the conductivity between the electrodes.

The average particle diameter of the conductive particles may be 1 μm or more, 2 μm or more, or 2.5 μm or more, from the viewpoint of excellent dispersibility and conductivity. The average particle diameter of the conductive particles may be 20 μm or less, 15 μm or less, 10 μm or less, 8 μm or less, 6 μm or less, 5.5 μm or less, or 5 μm or less, from the viewpoint of ensuring insulation between adjacent electrodes. From these viewpoints, the average particle diameter of the conductive particles may be 1 to 20 μm, 1 to 15 μm, 1 to 10 μm, 1 to 8 μm, or 1 to 6 μm.

The average particle diameter of the conductive particles is determined by observing 300 conductive particles contained in the adhesive composition using a scanning electron microscope (SEM) to measure the particle diameter of each conductive particle, and averaging the particle diameters of the 300 conductive particles. Note that if the conductive particles are not spherical, the particle diameter of the conductive particles is the diameter of a circle circumscribing the conductive particles in the image observed using the SEM.

The particle density of the conductive particles in the adhesive composition may be 100 particles/mm ² or more, 1000 particles/mm ² or more, or 3000 particles/mm ² or more, from the viewpoint of obtaining a stable connection resistance. The particle density of the conductive particles in the adhesive composition may be 100,000 particles/mm ² or less, 50,000 particles/mm ² or less, or 30,000 particles/mm ² or less, from the viewpoint of ensuring insulation between adjacent electrodes. From these viewpoints, the particle density of the conductive particles in the adhesive composition may be 100 to 100,000 particles/mm ² , 1000 to 50,000 particles/mm ² , or 3000 to 30,000 particles/mm ² .

The conductive particle content may be 10% by mass or more, 20% by mass or more, or 25% by mass or more, based on the total mass of the adhesive composition. The conductive particle content may be 50% by mass or less, 40% by mass or less, or 35% by mass or less, based on the total mass of the adhesive composition.

The content of the conductive particles may be 10 parts by mass or more, 30 parts by mass or more, 50 parts by mass or more, or 70 parts by mass or more based on 100 parts by mass of the cationic polymerizable compound. The content of the conductive particles may be 200 parts by mass or less, 150 parts by mass or less, 120 parts by mass or less, or 100 parts by mass or less based on 100 parts by mass of the cationic polymerizable compound.

The adhesive composition may further contain other components in addition to the above components. The other components may include a thermoplastic resin, a coupling agent, a filler, a stabilizer, a colorant, an antioxidant, a curing agent other than the curing agent containing pyridinium salt A, and the like. The adhesive composition may further contain a radically polymerizable compound and a radical polymerization initiator.

(Thermoplastic resin)
The adhesive composition may further contain a thermoplastic resin. The adhesive composition is easily formed into a film by containing a thermoplastic resin. Examples of the thermoplastic resin include phenoxy resin, epoxy resin, polyester resin, polyamide resin, polyurethane resin, polyester urethane resin, acrylic rubber, etc. These may be used alone or in combination of two or more. If the epoxy equivalent of the epoxy resin is 400 g/eq or more, it is treated as a thermoplastic resin.

The weight average molecular weight (Mw) of the thermoplastic resin may be, for example, 5,000 or more, 10,000 or more, 20,000 or more, or 40,000 or more, and may be 200,000 or less, 100,000 or less, 80,000 or less, or 60,000 or less. The weight average molecular weight of the thermoplastic resin is measured by gel permeation chromatography (GPC) and converted using a calibration curve based on standard polystyrene.

The content of the thermoplastic resin may be 5% by mass or more, 10% by mass or more, or 15% by mass or more, based on the total mass of the adhesive composition. The content of the thermoplastic resin may be 60% by mass or less, 50% by mass or less, or 40% by mass or less, based on the total mass of the adhesive composition.

The content of the thermoplastic resin may be 10 parts by mass or more, 30 parts by mass or more, 50 parts by mass or more, or 60 parts by mass or more based on 100 parts by mass of the cationic polymerizable compound. The content of the thermoplastic resin may be 150 parts by mass or less, 120 parts by mass or less, 100 parts by mass or less, 80 parts by mass or less, 60 parts by mass or less, 40 parts by mass or less, or 20 parts by mass or less based on 100 parts by mass of the cationic polymerizable compound.

(Coupling Agent)
The adhesive composition may further contain a coupling agent. By containing the coupling agent, the adhesive composition can further improve the adhesiveness. The coupling agent may be a silane coupling agent, for example, vinyltrimethoxysilane, vinyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, and condensates thereof. These may be used alone or in combination of two or more.

The content of the coupling agent may be 0.5% by mass or more, 1% by mass or more, or 2% by mass or more, based on the total mass of the adhesive composition. The content of the coupling agent may be 15% by mass or less, 10% by mass or less, or 5% by mass or less, based on the total mass of the adhesive composition.

The content of the coupling agent may be 1 part by mass or more, 3 parts by mass or more, or 5 parts by mass or more based on 100 parts by mass of the cationic polymerizable compound. The content of the coupling agent may be 30 parts by mass or less, 20 parts by mass or less, 10 parts by mass or less, or 8 parts by mass or less based on 100 parts by mass of the cationic polymerizable compound.

(Filling material)
The adhesive composition may further contain a filler. By containing the filler, the adhesive composition can further improve the connection reliability. The filler may be a non-conductive filler (e.g., non-conductive particles). The filler may be either an inorganic filler or an organic filler.

Examples of inorganic fillers include metal oxide particles such as silica particles, alumina particles, silica-alumina particles, titania particles, and zirconia particles; metal nitride particles, etc. These may be used alone or in combination of two or more types.

Examples of organic fillers include silicone particles, methacrylate-butadiene-styrene particles, acrylic-silicone particles, polyamide particles, and polyimide particles. These may be used alone or in combination of two or more.

The filler may be an inorganic filler or silica particles from the viewpoint of improving the film formability and the reliability of the connection structure. The silica particles may be crystalline silica particles or non-crystalline silica particles, and these silica particles may be synthetic products. The silica may be synthesized by a dry method or a wet method. The silica particles may include at least one type selected from the group consisting of fumed silica particles and sol-gel silica particles.

The silica particles may be surface-treated silica particles from the viewpoint of excellent dispersibility in the adhesive component. The surface-treated silica particles are, for example, silica particles whose surface hydroxyl groups have been hydrophobized with a silane compound or a silane coupling agent. The surface-treated silica particles may be, for example, silica particles surface-treated with a silane compound such as an alkoxysilane compound, a disilazane compound, or a siloxane compound, or may be silica particles surface-treated with a silane coupling agent.

Alkoxysilane compounds include methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, dimethoxydiphenylsilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, 1,6-bis(trimethoxysilyl)hexane, and 3,3,3-trifluoropropyltrimethoxysilane.

Examples of disilazane compounds include 1,1,1,3,3,3-hexamethyldisilazane, 1,3-diphenyltetramethyldisilazane, 1,3-bis(3,3,3-trifluoropropyl)-1,1,3,3-tetramethyldisilazane, and 1,3-divinyl-1,1,3,3-tetramethyldisilazane.

Siloxane compounds include tetradecamethylcycloheptasiloxane, decamethylcyclopentasiloxane, hexaphenylcyclosiloxane, octadecamethylcyclononasiloxane, hexadecamethylcyclooctasiloxane, dodecamethylcyclohexasiloxane, octaphenylcyclotetrasiloxane, hexamethylcyclotrisiloxane, heptaphenyldisiloxane, tetradecamethylhexasiloxane, dodecamethylpentasiloxane, hexa Methyldisiloxane, decamethyltetrasiloxane, hexamethoxydisiloxane, octamethyltrisiloxane, octamethylcyclotetrasiloxane, 1,3-vinyltetramethyldisiloxane, 2,4,6-trimethyl-2,4,6-trivinylcyclotrisiloxane, 1,3-dimethoxy-1,1,3,3-tetraphenyldisiloxane, 1,1,3,3-tetramethyl-1,3-diphenyldisiloxane, 1,3-dimethyl-1,3-diphenyl-1,3-di Vinyldisiloxane, 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, 1,1,1,3,5,5,5,-heptamethyl-3-(3-glycidyloxypropyl)trisiloxane, 1,3,5-tris(3,3,3-trifluoropropyl)-1,3,5-trimethylcyclotrisiloxane, 1,1,1,3,5,5,5,-heptamethyl-3-[(trimethylsilyl)oxy]trisiloxane, 1,3,-bis[2-(7-methylphenyl)phenyl]phenyl] Examples of such siloxanes include 1,1,3,3-tetramethyldisiloxane, 1,1,1,5,5,5-hexamethyl-3-[(trimethylsilyl)oxy]-3-vinyltrisiloxane, 3-[[dimethyl(vinyl)silyl]oxy]-1,1,5,5-tetramethyl-3-phenyl-1,5-vinyltrisiloxane, octavinyloctasilsesquioxane, and octaphenyloctasilasilsesquioxane.

Silane coupling agents include vinyltrimethoxysilane, vinyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2-(amino ethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, tris-(trimethoxysilylpropyl)isocyanurate, 3-ureidopropyltrialkoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, and 3-trimethoxysilylpropylsuccinic anhydride.

Silica particles that have been surface-treated with a silane compound or a silane coupling agent may be surface-treated with a silane compound such as 3-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, or trimethoxyphenylsilane to further hydrophobize the hydroxyl group residues on the surface of the silica particles.

The surface-treated silica particles may contain at least one selected from the group consisting of a reaction product (hydrolysis product) of silica and trimethoxyoctylsilane, a reaction product of silica and dimethylsiloxane, a reaction product of silicon dioxide or silica and dichloro(dimethyl)silane, a reaction product (hydrolysis product) of silica and bis(trimethylsilyl)amine, and a reaction product of silica and hexamethyldisilazane, or may contain at least one selected from the group consisting of a reaction product of silica and trimethoxyoctylsilane, and a reaction product of silica and bis(trimethylsilyl)amine, from the viewpoint of easily controlling the fluidity when the adhesive film for circuit connection is compressed when the adhesive composition is used as an adhesive film for circuit connection, and from the viewpoint of improving the mechanical properties and water resistance of the connection structure after compression.

The filler content may be 1 mass% or more, 3 mass% or more, or 5 mass% or more, based on the total mass of the adhesive composition. The filler content may be 50 mass% or less, 40 mass% or less, or 35 mass% or less, based on the total mass of the adhesive composition.

The amount of the filler may be 1 part by mass or more, 5 parts by mass or more, or 10 parts by mass or more based on 100 parts by mass of the cationic polymerizable compound. The amount of the filler may be 200 parts by mass or less, 150 parts by mass or less, or 100 parts by mass or less based on 100 parts by mass of the cationic polymerizable compound.

The radical polymerizable compound may be an acrylic compound. Examples of the acrylic compound include (meth)acrylic acid compounds, (meth)acrylate compounds, and imide compounds thereof. These may be used in either a monomer or oligomer state, or a combination of a monomer and an oligomer. The radical polymerizable compound may be used alone or in combination of two or more types.

Acrylic compounds include, for example, alkyl (meth)acrylate compounds such as methyl acrylate, ethyl acrylate, isopropyl acrylate, and isobutyl acrylate; polyol poly(meth)acrylate compounds such as ethylene glycol diacrylate, diethylene glycol diacrylate, trimethylolpropane triacrylate, and tetramethylolmethane tetraacrylate; aryloxy-hydroxyalkyl (meth)acrylate compounds such as 2-hydroxy-1,3-diacryloxypropane, 2,2-bis[4-(acryloxymethoxy)phenyl]propane, and 2,2-bis[4-(acryloxypolyethoxy)phenyl]propane; dicyclopentenyl acrylate, tricyclodecanyl acrylate, and tris(acryloyloxyethyl)isocyanurate.

The radical polymerization initiator may be one that generates free radicals by light or heat. Examples of the radical polymerization initiator include organic peroxides and azo compounds. Examples of the organic peroxides include peroxy esters, dialkyl peroxides, diacyl peroxides, peroxydicarbonates, peroxyketals, hydroperoxides, and silyl peroxides. The radical polymerization initiator may be used alone or in combination of two or more types.

Peroxy esters include cumyl peroxy neodecanoate, 1,1,3,3-tetramethylbutyl peroxy neodecanoate, 1-cyclohexyl-1-methylethyl peroxy neodecanoate, t-hexyl peroxy neodecanoate, t-butyl peroxy pivalate, 1,1,3,3-tetramethylbutyl peroxy 2-ethylhexanoate, 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, 1-cyclohexyl-1-methylethyl peroxy 2-ethylhexanoate, L-hexyl peroxy 2-ethylhexanoate, L- Examples include butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, 1,1-bis(t-butylperoxy)cyclohexane, t-hexylperoxyisopropyl monocarbonate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, 2,5-dimethyl-2,5-di(m-toluoylperoxy)hexane, t-butylperoxyisopropyl monocarbonate, t-butylperoxy-2-ethylhexyl monocarbonate, t-hexylperoxybenzoate, and t-butylperoxyacetate.

Examples of dialkyl peroxides include α,α'-bis(t-butylperoxy)diisopropylbenzene, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, t-butylcumyl peroxide, etc. Examples of hydroperoxides include diisopropylbenzene hydroperoxide and cumene hydroperoxide, etc.

Diacyl peroxides include isobutyl peroxide, 2,4-dichlorobenzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide, succinic peroxide, benzoylperoxytoluene, and benzoyl peroxide.

Examples of peroxydicarbonates include di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, bis(4-t-butylcyclohexyl) peroxydicarbonate, di-2-ethoxymethoxy peroxydicarbonate, di(2-ethylhexylperoxy)dicarbonate, dimethoxybutyl peroxydicarbonate, and di(3-methyl-3-methoxybutylperoxy)dicarbonate.

Specific examples of peroxyketals include 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-hexylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-(t-butylperoxy)cyclododecane, and 2,2-bis(t-butylperoxy)decane.

Specific examples of silyl peroxides include t-butyltrimethylsilyl peroxide, bis(t-butyl)dimethylsilyl peroxide, t-butyltrivinylsilyl peroxide, bis(t-butyl)divinylsilyl peroxide, tris(t-butyl)vinylsilyl peroxide, t-butyltriallylsilyl peroxide, bis(t-butyl)diallylsilyl peroxide, and tris(t-butyl)allylsilyl peroxide.

<Adhesive film for circuit connection>
The adhesive composition may be in the form of a film. That is, another embodiment of the present disclosure is an adhesive film for circuit connection, which contains a cationic polymerizable compound containing an epoxy compound X and a curing agent containing a pyridinium salt A. The adhesive film for circuit connection may contain conductive particles.

The particle density of the conductive particles in the adhesive film for circuit connection may be 100 particles/ ^mm2 or more, 1000 particles/ ^mm2 or more, or 3000 particles/ ^mm2 or more, from the viewpoint of obtaining a stable connection resistance. The particle density of the conductive particles in the adhesive film for circuit connection may be 100,000 particles/ ^mm2 or less, 50,000 particles/ ^mm2 or less, or 30,000 particles/mm2 or ^less , from the viewpoint of ensuring insulation between adjacent electrodes. From these viewpoints, the particle density of the conductive particles in the adhesive film for circuit connection may be 100 to 100,000 particles/ ^mm2 , 1000 to 50,000 particles/ ^mm2 , or 3000 to 30,000 particles/ ^mm2 .

The conductive particle content may be 10% by mass or more, 20% by mass or more, or 25% by mass or more, based on the total mass of the circuit connection adhesive film. The conductive particle content may be 50% by mass or less, 40% by mass or less, or 35% by mass or less, based on the total mass of the circuit connection adhesive film.

The content of the cationic polymerizable compound in the circuit connection adhesive film may be 10% by mass or more, 20% by mass or more, 25% by mass or more, or 30% by mass or more, based on the total mass of the circuit connection adhesive film, from the viewpoint of ensuring sufficient curability of the circuit connection adhesive film. The content of the cationic polymerizable compound in the circuit connection adhesive film may be 60% by mass or less, 50% by mass or less, 45% by mass or less, or 40% by mass or less, based on the total mass of the circuit connection adhesive film, from the viewpoint of ensuring formability of the circuit connection adhesive film. From these viewpoints, the content of the cationic polymerizable compound in the circuit connection adhesive film may be 10 to 60% by mass, based on the total mass of the circuit connection adhesive film.

The content of epoxy compound X in the circuit connection adhesive film may be 5 mass% or more, 10 mass% or more, 12 mass% or more, or 15 mass% or more, based on the total mass of the circuit connection adhesive film, from the viewpoint of ensuring sufficient curing properties of the circuit connection adhesive film. The content of epoxy compound X in the circuit connection adhesive film may be 50 mass% or less, 40 mass% or less, 35 mass% or less, or 30 mass% or less, based on the total mass of the circuit connection adhesive film, from the viewpoint of ensuring formability of the circuit connection adhesive film. From these viewpoints, the content of epoxy compound X in the circuit connection adhesive film may be 10 to 50 mass%, based on the total mass of the circuit connection adhesive film.

The total content of compounds A to D in the circuit connection adhesive film may be 5 mass% or more, 10 mass% or more, 12 mass% or more, or 15 mass% or more, based on the total mass of the circuit connection adhesive film, from the viewpoint of ensuring sufficient curability of the circuit connection adhesive film. The total content of compounds A to D in the circuit connection adhesive film may be 50 mass% or less, 40 mass% or less, 35 mass% or less, or 30 mass% or less, based on the total mass of the circuit connection adhesive film, from the viewpoint of ensuring formability of the circuit connection adhesive film. From these viewpoints, the total content of compounds A to D in the circuit connection adhesive film may be 5 to 50 mass% or 10 to 50 mass%, based on the total mass of the circuit connection adhesive film.

The content of the curing agent in the circuit connection adhesive film may be 1 mass % or more, 2 mass % or more, 3 mass % or more, 4 mass % or more, or 5 mass % or more, based on the total mass of the circuit connection adhesive film, from the viewpoint of sufficiently promoting the curing reaction. The content of the curing agent in the circuit connection adhesive film may be 20 mass % or less, 15 mass % or less, 10 mass % or less, 8 mass % or less, or 6 mass % or less, based on the total mass of the circuit connection adhesive film, from the viewpoint of improving the physical properties of the cured product. From these viewpoints, the content of the curing agent in the circuit connection adhesive film may be 1 to 20 mass %, based on the total mass of the circuit connection adhesive film.

The content of the curing agent in the circuit connection adhesive film may be 1 mass % or more, 3 mass % or more, 5 mass % or more, or 7 mass % or more, based on the total mass of the circuit connection adhesive film excluding the conductive particles, from the viewpoint of sufficiently promoting the curing reaction. The content of the curing agent in the circuit connection adhesive film may be 30 mass % or less, 25 mass % or less, 20 mass % or less, 15 mass % or less, or 10 mass % or less, based on the total mass of the circuit connection adhesive film excluding the conductive particles, from the viewpoint of improving the physical properties of the cured product. From these viewpoints, the content of the curing agent in the circuit connection adhesive film may be 1 to 30 mass %, based on the total mass of the circuit connection adhesive film excluding the conductive particles.

The content of the curing agent in the circuit connection adhesive film may be 1 mass % or more, 3 mass % or more, 5 mass % or more, or 7 mass % or more, based on the total mass of the circuit connection adhesive film excluding the conductive particles and filler, from the viewpoint of sufficiently promoting the curing reaction. The content of the curing agent in the circuit connection adhesive film may be 30 mass % or less, 25 mass % or less, 20 mass % or less, 15 mass % or less, or 10 mass % or less, based on the total mass of the circuit connection adhesive film excluding the conductive particles and filler, from the viewpoint of improving the physical properties of the cured product. From these viewpoints, the content of the curing agent in the circuit connection adhesive film may be 1 to 30 mass %, based on the total mass of the circuit connection adhesive film excluding the conductive particles and filler.

The thermoplastic resin content in the circuit connection adhesive film may be 5 mass% or more, 10 mass% or more, or 15 mass% or more, based on the total mass of the circuit connection adhesive film. The thermoplastic resin content in the circuit connection adhesive film may be 40 mass% or less, 30 mass% or less, or 20 mass% or less, based on the total mass of the circuit connection adhesive film.

The content of the coupling agent in the circuit connection adhesive film may be 0.5 mass% or more, 1 mass% or more, or 1.5 mass% or more, based on the total mass of the circuit connection adhesive film. The content of the coupling agent in the circuit connection adhesive film may be 10 mass% or less, 5 mass% or less, or 3 mass% or less, based on the total mass of the circuit connection adhesive film.

The filler content in the circuit connection adhesive film may be 1 mass % or more, 3 mass % or more, or 5 mass % or more, based on the total mass of the circuit connection adhesive film. The filler content in the circuit connection adhesive film may be 50 mass % or less, 40 mass % or less, or 35 mass % or less, based on the total mass of the circuit connection adhesive film.

The content of each component of the circuit-connecting adhesive film based on 100 parts by mass of the cationic polymerizable compound may be within the same range as the content of each component of the above-mentioned adhesive composition based on 100 parts by mass of the cationic polymerizable compound.

The circuit connection adhesive film may be a single layer, or may have a multilayer structure in which multiple layers are laminated. When the circuit connection adhesive film has a multilayer structure, the circuit connection adhesive film may have, for example, a first adhesive layer containing a cationic polymerizable compound containing an epoxy compound X and a curing agent containing a pyridinium salt A, and a second adhesive layer other than the first adhesive layer. That is, the circuit connection adhesive film may have a first adhesive layer and a second adhesive layer laminated on the first adhesive layer. At least one of the first adhesive layer and the second adhesive layer may contain a cationic polymerizable compound containing an epoxy compound X, a curing agent containing a pyridinium salt A, and conductive particles. When the circuit connection adhesive film has a multilayer structure, the content of each of the above components in each layer may be within the above content range based on the total mass of each layer.

The circuit connection adhesive film may have multiple regions with different types and contents of components. The circuit connection adhesive film may have, for example, a first region and a second region disposed on the first region, and the first region may be a region containing a cationic polymerizable compound containing an epoxy compound X and a curing agent containing a pyridinium salt A. That is, the circuit connection adhesive film may have a first region that is a region formed from a first adhesive composition containing a cationic polymerizable compound containing an epoxy compound X and a curing agent containing a pyridinium salt A, and a second region that is a region formed from a second adhesive composition disposed on the first region. When the circuit connection adhesive film has multiple regions, the content of each of the above components in each region may be within the above content range based on the total mass of each region.

The circuit connection adhesive film may be provided on a substrate (e.g., a PET film) or the like. The circuit connection adhesive film with a substrate can be produced, for example, by applying an adhesive composition containing conductive particles onto a substrate using a knife coater, roll coater, applicator, comma coater, die coater, or the like.

FIG. 1 is a schematic cross-sectional view showing an adhesive film for circuit connection according to one embodiment. As shown in FIG. 1, in one embodiment, the adhesive film for circuit connection 1 is composed of a single layer consisting of an adhesive component 2 and conductive particles 3 dispersed in the adhesive component 2. In one embodiment, the adhesive component 2 contains at least a cationic polymerizable compound containing an epoxy compound X and a curing agent containing a pyridinium salt A. The adhesive film for circuit connection 1 may be in an uncured state or in a partially cured state.

The thickness of the circuit connection adhesive film 1 may be, for example, 3 μm or more or 5 μm or more, and 30 μm or less or 20 μm or less.

In one embodiment, the adhesive film for circuit connection may have a multilayer structure having two or more layers. For example, as shown in FIG. 2, the adhesive film for circuit connection 1 may have a two-layer structure including a layer containing conductive particles 3A (a first adhesive layer consisting of adhesive component 2A and conductive particles 3A dispersed in adhesive component 2A) 1A and a layer not containing conductive particles (a second adhesive layer consisting of adhesive component 2B) 1B. In this case, the first adhesive layer 1A may be a layer consisting of an adhesive composition (first adhesive composition) containing a cationic polymerizable compound containing epoxy compound X, a curing agent containing pyridinium salt A, and conductive particles. The second adhesive layer 1B may be a layer consisting of an adhesive composition (second adhesive composition) containing a cationic polymerizable compound containing epoxy compound X and a curing agent containing pyridinium salt A. The type, content, etc. of each component contained in the second adhesive layer 1B may be the same as or different from that of the first adhesive layer 1A. The first adhesive layer 1A and the second adhesive layer 1B of the circuit connection adhesive film 1 may each be in an uncured state or in a partially cured state.

The thickness of the first adhesive layer 1A may be, for example, 1 μm or more or 3 μm or more, and 15 μm or less or 10 μm or less. The thickness of the second adhesive layer 1B may be, for example, 1 μm or more or 3 μm or more, and 20 μm or less or 15 μm or less. The thickness of the first adhesive layer 1A may be the same as or different from the thickness of the second adhesive layer 1B. The ratio of the thickness of the first adhesive layer 1A to the thickness of the second adhesive layer 1B (thickness of the first adhesive layer 1A/thickness of the second adhesive layer 1B) may be 0.1 or more or 0.3 or more, and 1.5 or less or 0.5 or less.

The above-mentioned circuit connection adhesive film may be an anisotropic conductive adhesive film (anisotropic conductive film), or it may be a conductive adhesive film that does not have anisotropic conductivity.

<Connection structure>
Another embodiment of the present disclosure is a connection structure comprising a first circuit member having a first electrode, a second circuit member having a second electrode, and a connection portion disposed between the first circuit member and the second circuit member and electrically connecting the first electrode and the second electrode to each other, wherein the connection portion comprises a cured product of the above-mentioned adhesive film for circuit connection.

Figure 3 is a schematic cross-sectional view showing one embodiment of a connection structure. As shown in Figure 3, the structure 10 includes a first circuit member 4 and a second circuit member 5 that face each other, and a connection portion 6 that connects the first circuit member 4 and the second circuit member 5 between the first circuit member 4 and the second circuit member 5.

The first circuit member 4 includes a first circuit board 41 and a first electrode 42 formed on the main surface 41a of the first circuit board 41. The second circuit member 5 includes a second circuit board 51 and a second electrode 52 formed on the main surface 51a of the second circuit board 51.

The first circuit member 4 and the second circuit member 5 are not particularly limited as long as they are members on which electrodes that require electrical connection are formed. Examples of members on which electrodes are formed (circuit members, etc.) include inorganic substrates such as semiconductors, glass, and ceramics; polyimide substrates such as TCP, FPC, and COF; substrates on which electrodes are formed on films such as polycarbonate, polyester, and polyethersulfone; printed wiring boards, and the like; and a combination of two or more of these may be used.

The connection portion 6 includes a cured product of the circuit connection adhesive film 1, and contains an insulating material 7, which is a cured product of the adhesive component 2, and conductive particles 3. The conductive particles 3 may be disposed not only between the opposing first electrode 42 and second electrode 52, but also between the main surface 41a of the first circuit board 41 and the main surface 51a of the second circuit board 51. In the structure 30, the first electrode 42 and the second electrode 52 are electrically connected via the conductive particles 3. That is, the conductive particles 3 are in contact with both the first electrode 42 and the second electrode 52.

As described above, in the structure 10, the opposing first electrode 42 and second electrode 52 are electrically connected via the conductive particles 3. This sufficiently reduces the connection resistance between the first electrode 42 and the second electrode 52. This allows the current to flow smoothly between the first electrode 42 and the second electrode 52, allowing the functions of the first circuit member 4 and the second circuit member 5 to be fully exerted.

<Method of Manufacturing Connection Structure>
Another embodiment of the present disclosure is a method for producing a connection structure, comprising the steps of interposing the above-mentioned adhesive film for circuit connection between a first circuit member having a first electrode and a second circuit member having a second electrode, and thermocompressing the first circuit member and the second circuit member to electrically connect the first electrode and the second electrode to each other.

FIG. 4 is a schematic cross-sectional view showing one embodiment of a method for manufacturing a connection structure. As shown in FIG. 4(a), first, a first circuit member 4 and a circuit connection adhesive film 1 are prepared. Next, the circuit connection adhesive film 1 is placed on the main surface 41a of the first circuit member 4. When the circuit connection adhesive film 1 is laminated on a substrate (not shown), the laminate is placed on the first circuit member 4 so that the circuit connection adhesive film 1 side of the substrate faces the first circuit member 4. When the circuit connection adhesive film 1 has a first adhesive layer 1A and a second adhesive layer 1B as shown in FIG. 2, it is preferable to place the adhesive layer (first adhesive layer 1A) containing conductive particles in contact with the main surface 41a of the first circuit member 4 from the viewpoint of increasing the number of conductive particles captured between the opposing electrodes.

Then, the circuit connection adhesive film 1 is pressed in the directions of arrows A and B in FIG. 4(a) to temporarily connect the circuit connection adhesive film 1 to the first circuit member 4 (see FIG. 4(b)). At this time, heating may be performed in addition to the pressing.

Subsequently, as shown in FIG. 4(c), the second circuit member 5 is further placed on the circuit connection adhesive film 1 placed on the first circuit member 4 with the second electrode 52 facing the first circuit member 4 (i.e., the first electrode 42 and the second electrode 52 are placed opposite each other, and the circuit connection adhesive film 1 is interposed between the first circuit member 4 and the second circuit member 5). If the circuit connection adhesive film 1 is laminated on a substrate (not shown), the substrate is peeled off and then the second circuit member 5 is placed on the circuit connection adhesive film 1.

Then, the circuit connection adhesive film 1 is thermocompressed in the directions of arrows A and B in FIG. 4(c). This hardens the circuit connection adhesive film 1, and completes the electrical connection between the first electrode 42 and the second electrode 52. As a result, a structure 10 as shown in FIG. 3 is obtained.

In the structure 10 obtained as described above, it is possible to bring the conductive particles 3 into contact with both the opposing first electrode 42 and second electrode 52, and the connection resistance between the first electrode 42 and the second electrode 52 can be sufficiently reduced.

By heating and pressurizing the circuit connection adhesive film 1, the adhesive component 2 hardens and becomes an insulating material 7 while the distance between the first electrode 42 and the second electrode 52 is kept sufficiently small, and the first circuit member 4 and the second circuit member 5 are firmly connected via the connection portion 6. Furthermore, in the structure 10, the adhesive strength remains sufficiently high for a long period of time. Therefore, in the structure 10, the change over time in the distance between the first electrode 42 and the second electrode 52 is sufficiently suppressed, and the long-term reliability of the electrical properties between the first electrode 42 and the second electrode 52 is excellent.

The present disclosure will be specifically explained below using examples. However, the present disclosure is not limited to the following examples.

<Preparation of hardener>
[Synthesis and analysis of curing agent B1]
100 mL of acetonitrile and a stirrer chip were placed in a 300 mL Erlenmeyer flask and placed on a magnetic stirrer. 12.5 g of 2-cyanopyridine (120 mmol, manufactured by Tokyo Chemical Industry Co., Ltd.), 16.8 g of 2,4,6-trimethylbenzyl chloride (100 mmol, manufactured by Tokyo Chemical Industry Co., Ltd.), and 17.8 g of sodium iodide (119 mmol, manufactured by Tokyo Chemical Industry Co., Ltd.) were added to acetonitrile in a 300 mL Erlenmeyer flask, and the mixture was reacted at room temperature (25°C) for 24 hours to obtain crystals. The obtained crystals were filtered through a glass filter, and the crystals on the glass filter were washed with acetone and distilled water, and then vacuum dried to obtain 29.1 g of 2-cyano-1-(2,4,6-trimethylbenzyl)pyridinium iodide (yield 80%).

200 mL of dichloromethane and a stirrer tip were placed in a 500 mL Erlenmeyer flask and placed on a magnetic stirrer. 3.6 g (10 mmol) of the obtained 2-cyano-1-(2,4,6-trimethylbenzyl)pyridinium iodide was added to a 500 mL Erlenmeyer flask and suspended in dichloromethane in the 500 mL Erlenmeyer flask. 72 g (10.2 mmol, Nippon Shokubai Co., Ltd.) of sodium tetrakis(pentafluorophenyl)borate aqueous solution (solid content 10%) and 50 mL of distilled water were added to the 500 mL Erlenmeyer flask and stirred at room temperature (25°C) for 3 hours to carry out a salt exchange reaction. After stirring, the organic layer was washed with distilled water, concentrated, and vacuum dried to obtain 8.0 g of compound (yield 88%). The obtained compound was designated as curing agent B1.

The resulting compound was measured by nuclear magnetic resonance spectroscopy ( ¹ H-NMR, JNM-ECX400II, manufactured by JEOL Ltd.), and the following spectral data was obtained. From the ¹ H-NMR measurement, it was confirmed that the resulting compound was 2-cyano-1-(2,4,6-trimethylbenzyl)pyridinium tetrakis(pentafluorophenyl)borate having the following structure.
^1H -NMR (400MHz, CD ₃ OD), δ: 2.26 (s, 6H), 2.32 (s, 3H), 6.10 (s, 2H), 7.08 (s, 2H), 8.25 (td, 1H, J = 3.2, 6.4Hz) 8.43 (d, 1H, J = 6.4Hz) 8.77- 8.82 (m, 2H)

<Synthesis of phenoxy resin a>
In a 3000 mL three-neck flask equipped with a Dimroth condenser, a calcium chloride tube, and a Teflon (registered trademark) stirring rod connected to a stirring motor, 45 g of 4,4'-(9-fluorenylidene)-diphenol (Sigma-Aldrich Japan Co., Ltd.) and 50 g of 3,3',5,5'-tetramethylbiphenol diglycidyl ether (product name: YX-4000H, Mitsubishi Chemical Co., Ltd.) were dissolved in 1000 mL of N-methylpyrrolidone to prepare a reaction solution. 21 g of potassium carbonate was added to this reaction solution, and the mixture was stirred for 3 hours while being heated to 110°C with a mantle heater. The reaction solution after stirring was dropped into a beaker containing 1000 mL of methanol, and the precipitate formed by suction filtration was collected by filtration. The collected precipitate was further washed three times with 300 mL of methanol to obtain 75 g of phenoxy resin a. The molecular weight of the obtained phenoxy resin a was measured using a high performance liquid chromatograph (GP8020 manufactured by Tosoh Corporation, column: Gelpack GL-A150S and GLA160S manufactured by Showa Denko Materials K.K., eluent: tetrahydrofuran, flow rate: 1.0 mL/min), and the polystyrene-equivalent molecular weights were Mn=15769, Mw=38045, and Mw/Mn=2.413.

<Preparation of conductive particles>
A layer of nickel was formed on the surface of the crosslinked polystyrene particles to a thickness of 0.15 μm, to obtain conductive particles having an average particle size of 3.0 μm.

<Preparation of Adhesive Film for Circuit Connection>
A first adhesive composition for forming a first adhesive layer and a second adhesive composition for forming a second adhesive layer were prepared by mixing the components in the amounts (unit: parts by mass) shown in Table 1. The details of each component in Table 1 are as follows, and the amount of each component in the table represents the amount of non-volatile content.
Cationic polymerizable compound A1: bisphenol A type epoxy resin (bifunctional epoxy resin, manufactured by Mitsubishi Chemical Corporation, product name: YL980, epoxy equivalent: 180 to 190 g/eq)
A2: Naphthalene-type epoxy resin (tetrafunctional epoxy resin, manufactured by DIC Corporation, product name: HP4700, epoxy equivalent: 165 g/eq, solid at room temperature)
A3: Trisphenolmethane type epoxy resin (multifunctional epoxy resin, manufactured by Mitsubishi Chemical Corporation, product name: jER1032H60, epoxy equivalent: 163 to 175 g/eq, solid at room temperature)
A4: Tetrakisphenolmethane type epoxy resin (tetrafunctional epoxy resin, manufactured by Mitsubishi Chemical Corporation, product name: jER1031S, epoxy equivalent: 180 to 220 g/eq, solid at room temperature)
A5: Bisphenol A type epoxy resin (tetrafunctional epoxy resin, epoxy resin having two glycidyl groups and two glycidyloxy groups, manufactured by Showa Denko K.K., product name: BATG, epoxy equivalent: 120 to 128 g/eq, liquid at room temperature)
A6: Bisphenol F type epoxy resin (bifunctional epoxy resin, manufactured by Mitsubishi Chemical Corporation, product name: YL983U, epoxy equivalent: 165 to 175 g/eq)
A7: Novolac type epoxy resin having an aralkyl skeleton (trifunctional epoxy resin, manufactured by Mitsubishi Chemical Corporation, product name: YX7700, epoxy equivalent: 260 to 285 g/eq, solid at room temperature)
A8: Aliphatic epoxy resin (tetrafunctional epoxy resin, manufactured by Showa Denko K.K., product name: PETG, epoxy equivalent: 90 to 100 g/eq)
Curing agent B1: Curing agent synthesized above B2: Sulfonium salt (manufactured by Sanshin Chemical Industry Co., Ltd., product name: SI60)
Thermoplastic resin C1: Phenoxy resin a synthesized above
C2: Epoxy resin (manufactured by Mitsubishi Chemical Corporation, product name: jER1010, epoxy equivalent: 3000 to 5000 g/eq)
Filler D1: Surface-treated silica particles (hydrolysis product of silica and bis(trimethylsilyl)amine)
D2: Surface-treated silica particles (hydrolysis product of trimethoxyoctylsilane and silica, manufactured by Evonik Industries AG, product name: Aerosil R805, diluted with an organic solvent to a non-volatile content of 10% by mass)
Coupling agent E1: Silane coupling agent (3-glycidoxypropyltrimethoxysilane, product name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.)
Conductive particles F1: Conductive particles prepared as above

The second adhesive composition was applied onto the substrate (PET film) to form a second adhesive layer on the substrate. Furthermore, the first adhesive composition was applied onto the second adhesive layer to form a first adhesive layer, producing an adhesive film for circuit connection in which the first adhesive layer, the second adhesive layer, and the substrate were laminated in this order. In each of the examples and comparative examples, the thickness of the first adhesive layer of the adhesive film for circuit connection was 7 μm, and the thickness of the second adhesive layer was 7 μm.

<Preparation of Connection Structure>
As a first circuit member, an alkali-free glass substrate (OA-11, manufactured by Nippon Electric Glass Co., Ltd., outer dimensions: 38 mm x 28 mm, thickness: 0.3 mm) was prepared on the surface of which was formed a wiring pattern of AlNd (100 nm)/Mo (50 nm)/ITO (100 nm) (pattern width: 19 μm, space between electrodes: 5 μm). As a second circuit member, an IC chip (outer dimensions: 0.9 mm x 20.3 mm, thickness: 0.3 mm, bump electrode size: 70 μm x 12 μm, space between bump electrodes: 12 μm, bump electrode thickness: 8 μm) was prepared in which bump electrodes were arranged in two rows in a staggered pattern.

A connection structure was prepared using each circuit connection adhesive film of each Example and Comparative Example. First, the first adhesive layer of the circuit connection adhesive film was placed on the first circuit member. Using a thermocompression bonding device (manufactured by Ohashi Manufacturing Co., Ltd.) consisting of a stage made of a ceramic heater and a tool (8 mm x 50 mm), the circuit connection adhesive film was attached to the first circuit member by heating and pressing for 1 second under conditions of 60 ° C. and 0.98 MPa (10 kgf / cm ² ). Next, the substrate on the opposite side of the circuit connection adhesive film from the first circuit member was peeled off, and the bump electrodes of the first circuit member and the circuit electrodes of the second circuit member were aligned. Next, using a heat tool (8 mm x 45 mm), the second adhesive layer of the circuit connection adhesive film was attached to the second circuit member by heating and pressing at 60 MPa for 5 seconds at the mounting temperature shown in Table 2 on a pedestal heated to 90 ° C. via a PTFE sheet having a thickness of 50 μm as a buffer material, to prepare a connection structure. The mounting temperature was the highest temperature actually measured of the adhesive film for circuit connection, and the pressure was a value calculated with respect to the total area of the surface of the bump electrodes of the second circuit member facing the first circuit member.

<Appearance evaluation>
The appearance after the HAST test was evaluated. The HAST test was performed by setting the device in an accelerated life tester (manufactured by Hirayama Manufacturing Co., Ltd., product name: PC-242HSR2, conditions: 110°C/85% RH/150 hours). The appearance was evaluated as follows: a peeled area of the circuit connection adhesive film was less than 1% of the area of the adhesive surface, 1% or more and less than 10%, 10% or more and less than 50%, and 50% or more. The evaluation results are shown in Table 2.

<Evaluation of bubbles>
The presence or absence of bubbles after the HAST test was evaluated. The HAST test was performed by setting the film in an accelerated life tester (manufactured by Hirayama Manufacturing Co., Ltd., product name: PC-242HSR2, conditions: 110°C/85% RH/150 hours). The bubble evaluation was performed with the area of the adhesive surface of the circuit connection adhesive film where bubbles occurred being less than 10% as grade A, and the area of the adhesive surface of the circuit connection adhesive film where bubbles occurred being 10% or more as grade B. The evaluation results are shown in Table 2.

As shown in Table 2, the adhesive composition contains an epoxy compound that is trifunctional or higher and has an epoxy equivalent of more than 100 g/eq and 250 g/eq or less as a cationic polymerizable compound, and a pyridinium salt that has a benzyl group at the 1st position and an electron-withdrawing group at the 2nd position, in which the benzyl group has an electron-donating group, as a curing agent. This allows mounting at low temperatures (e.g., 120°C) to high temperatures (e.g., 150°C), and it has been confirmed that the adhesive composition has excellent appearance and little generation of bubbles even after HAST testing in both low-temperature and high-temperature mounting.

REFERENCE SIGNS LIST 1...adhesive film for circuit connection, 1A...first adhesive layer, 1B...second adhesive layer, 2, 2A, 2B...adhesive component, 3, 3A...conductive particles, 4...first circuit member, 5...second circuit member, 6...connection portion, 7...insulating material, 10...structure, 41...first circuit board, 42...first electrode, 51...second circuit board, 52...second electrode.

Claims

Contains a cationic polymerizable compound and a curing agent,
the cationically polymerizable compound contains an epoxy compound which is tri- or higher functional and has an epoxy equivalent of more than 100 g/eq and not more than 250 g/eq,
the curing agent contains a pyridinium salt;
The pyridinium salt has a benzyl group at the 1-position and an electron-withdrawing group at the 2-position;
The adhesive composition, wherein the benzyl group has an electron donating group.
The adhesive composition according to claim 1, wherein the epoxy compound has an aromatic ring.
The adhesive composition of claim 1, wherein the epoxy compound is a solid at room temperature.
The adhesive composition according to claim 1, wherein the cationic polymerizable compound includes at least one selected from the group consisting of an epoxy compound having a trisphenolmethane structure, an epoxy compound having a bisphenol structure and a glycidyl group and a glycidyloxy group, an epoxy compound having a tetravalent organic group and an aromatic ring bonded to the organic group, the aromatic ring having a substituent containing an epoxy group, and an epoxy compound having a naphthalene structure.
The adhesive composition according to claim 1, wherein the electron-withdrawing group is a cyano group or a halogeno group.
The adhesive composition according to claim 1, wherein the electron donating group is an alkyl group or an alkoxy group.
the number of electron-donating groups in the benzyl group is 3;
The adhesive composition of claim 1 , wherein the electron donating group is an alkyl group.
The pyridinium salt comprises a pyridinium cation and an anion,
The adhesive composition of claim 1, wherein the anion is B(C 6 F 5 ) 4 -.
The adhesive composition according to claim 1, further comprising conductive particles.
An adhesive film for circuit connection, comprising an adhesive layer formed from the adhesive composition according to any one of claims 1 to 9.
A first adhesive layer and a second adhesive layer laminated on the first adhesive layer,
An adhesive film for circuit connection, wherein at least one of the first adhesive layer and the second adhesive layer is a layer formed from the adhesive composition according to any one of claims 1 to 9.
a first circuit member having a first electrode;
a second circuit member having a second electrode;
a connection portion disposed between the first circuit member and the second circuit member, electrically connecting the first electrode and the second electrode to each other;
Equipped with
A connection structure, wherein the connection portion comprises a cured product of the adhesive film for circuit connection according to claim 10.
11. A method for producing a connection structure, comprising the steps of: interposing the adhesive film for circuit connection according to claim 10 between a first circuit member having a first electrode and a second circuit member having a second electrode; and thermocompressing the first circuit member and the second circuit member to electrically connect the first electrode and the second electrode to each other.