Anisotropic conductive material, anisotropic conductive paste, and anisotropic conductive adhesive sheet

Abstract

The present invention provides: an anisotropic conductive material comprising an epoxy resin (A), an acrylic resin (B), and conductive particles (C), wherein the acrylic resin (B) contains monomer units derived from a nitrogen-atom-containing monomer in the amount of 0.5-49.5 mol% with respect to all monomer units of the acrylic resin (B); an anisotropic conductive adhesive sheet; and an anisotropic conductive paste.

Description

Anisotropic conductive material, anisotropic conductive paste, and anisotropic conductive adhesive sheet

[0001] The present invention relates to an anisotropically conductive material, an anisotropically conductive paste, and an anisotropically conductive adhesive sheet.

[0002] Conventionally, a tape material (anisotropic conducting film: ACF) in which a thermosetting resin with dispersed conductive particles is applied to a release film has been used as a means for connecting circuit components. ACF is used to bond and electrically connect components such as terminals of a flexible printed circuit board (FPC) or an IC chip to ITO electrodes formed on the glass substrate of an LCD (liquid crystal display) panel, for example.

[0003] As an organic-inorganic composite that can ensure excellent heat dissipation and electrical conductivity even when the ratio of inorganic material to the composite resin is small, for example, Patent Document 1 discloses an organic-inorganic composite that contains a composite resin having a co-continuous phase separation structure formed from a three-dimensionally continuous first phase made of a first resin and a three-dimensionally continuous second phase made of a second resin different from the first resin, and an inorganic material that is unevenly distributed at the interface between the first phase and the second phase.

[0004] As an example of a conductive paste that can increase the bonding strength with electronic components without using a separate adhesive, Patent Document 2 discloses a conductive paste containing an organic component and conductive particles, in which the storage modulus G' (P100) of a dried film of the conductive paste at 100°C is 0.01 MPa or less, and the storage modulus G' (C25) at 25°C after heating at 140°C for 30 minutes is 0.01 MPa or more.

[0005] As an adhesive composition that can prevent blocking from occurring and achieve good temporary pressure-bonding properties, for example, Patent Document 3 discloses an adhesive composition that contains an epoxy resin, a latent curing agent, and an acrylic rubber having a carboxyl group or a glycidyl group, and is characterized in that the acrylic rubber phase-separates from the epoxy resin at room temperature and is compatible with the epoxy resin at a predetermined temperature that is higher than room temperature and lower than the curing temperature.

[0006] Japanese Patent Publication No. 2010-132894 Japanese Patent No. 7067676 Japanese Patent No. 6408759

[0007] In recent years, finer patterns of wiring, such as in flexible printed circuit boards (FPCs), have become increasingly common, resulting in narrower pitches between wiring. Meanwhile, the limitations of reducing the diameter of metal-plated particles used as conductive particles in ACFs have become apparent, resulting in problems such as conduction between adjacent wiring. Given these circumstances, there is a demand for the development of an anisotropic conductive adhesive sheet with excellent conduction reliability that is less likely to result in unintended conduction or electrode terminals that do not form conduction.

[0008] The problem that one embodiment of the present invention aims to solve is to provide an anisotropic conductive material, an anisotropic conductive adhesive sheet, and an anisotropic conductive paste that, when used in a connection structure, have excellent conductivity between opposing circuit components and maintain insulation between electrodes within the same circuit component.

[0009] Means for solving the above problems include the following aspects. <1> An anisotropically conductive material comprising an epoxy resin (A), an acrylic resin (B), and conductive particles (C), wherein the acrylic resin (B) contains 0.5 to 49.5 mol % of monomer units derived from nitrogen-atom-containing monomers relative to all monomer units of the acrylic resin (B). <2> The anisotropically conductive material according to <1>, wherein the acrylic resin (B) has a weight-average molecular weight (Mw) of 1,000 to 30,000. <3> The anisotropically conductive material according to <1> or <2>, wherein the conductive particles (C) have an average particle size of 0.01 to 20 μm. <4> The anisotropically conductive material according to any one of <1> to <3>, wherein the epoxy resin (A) has a weight-average molecular weight (Mw) of 5,000 to 30,000 and comprises a solvent (D). <5> The solvent (D) has a solubility parameter SP value of 8.2 to 10.6 (cal / cm ３ ) ０．５ <6> The anisotropically conductive material according to any one of <1> to <5>, wherein the acrylic resin (B) contains more than 50 mol% of monomer units derived from alkyl(meth)acrylate in which the alkyl group has 1 to 12 carbon atoms, based on the total monomer units of the acrylic resin (B). <7> An anisotropically conductive paste formed from the anisotropically conductive material according to any one of <1> to <6>. <8> An anisotropically conductive adhesive sheet formed from the anisotropically conductive material according to any one of <1> to <6>.

[0010] According to one embodiment of the present invention, there are provided an anisotropic conductive material, an anisotropic conductive adhesive sheet, and an anisotropic conductive paste that, when used in a connection structure, provide excellent conductivity between opposing circuit components while maintaining insulation between electrodes within the circuit components.

[0011] The present invention will be described in detail below. The following description of the constituent elements may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In this specification, the term "to" indicating a numerical range is used to mean that the numerical values ​​before and after the term are included as the lower and upper limits. In this specification, the units before and after the term "to" indicating a numerical range indicate the same units unless otherwise specified. The term "process" in this specification refers not only to an independent process, but also to a process that cannot be clearly distinguished from other processes, as long as the desired purpose of that process is achieved. Furthermore, in this specification, unless otherwise specified, each component in the anisotropically conductive material may be contained alone or in combination with two or more components. In this specification, when multiple components are present in the anisotropically conductive material, the amount of each component in the anisotropically conductive material refers to the total amount of the corresponding substance present in the anisotropically conductive material, unless otherwise specified. In this specification, a combination of two or more preferred aspects is a more preferred aspect. In this specification, "(meth)acrylate" refers to either or both of "acrylate" and "methacrylate," "(meth)acrylic" refers to either or both of "acrylic" and "methacrylic," and "(meth)acryloyl" refers to either or both of "acryloyl" and "methacryloyl." In this specification, a "monomer unit" refers to a structural unit contained in a polymer compound and derived from a monomer compound. In this specification, the term "total solid content" refers to the total mass of all components of an anisotropically conductive material (composition) excluding the solvent. In addition, in this specification, the term "solid content concentration" refers to the mass percentage of the components other than the solvent relative to the total mass of the anisotropically conductive material (composition). The present invention will be described in detail below.

[0012] <Anisotropically Conductive Material> The anisotropically conductive material according to the present invention comprises an epoxy resin (A), an acrylic resin (B), and conductive particles (C), wherein the acrylic resin (B) contains 0.5 to 49.5 mol % of monomer units derived from a nitrogen-atom-containing monomer, relative to the total monomer units of the acrylic resin (B). Because the anisotropically conductive material according to the present invention has the above-described configuration, when used in a connection structure, it exhibits excellent conductivity (hereinafter sometimes simply referred to as "conductivity") between opposing circuit members, while maintaining insulation (hereinafter sometimes simply referred to as "insulation") between electrodes within the same circuit member. While the reason for this is unclear, the following mechanism is presumed. The anisotropically conductive material according to the present invention contains, as resin components, an acrylic resin (B) containing specific amounts of monomer units derived from a nitrogen-atom-containing monomer and an epoxy resin (A). Therefore, when the anisotropically conductive material is applied to, for example, a substrate, it is presumed that the resin components are likely to form a sea-island structure, and the acrylic resin (B) containing the specific amount of monomer units derived from a nitrogen-atom-containing monomer is likely to form domains (i.e., island structures). Furthermore, although the reason is unclear, it is believed that the conductive particles (C) tend to be unevenly distributed in the acrylic resin (B) phase. When the domain size of the acrylic resin (B) containing the unevenly distributed conductive particles (C) is approximately the same as the spacing between the electrodes of opposing circuit components, but smaller than the spacing between the electrodes within the same circuit component, it is believed that conductivity between the opposing circuit components is more readily achieved, and the insulation between the electrodes within the same circuit component is better maintained. Furthermore, even when the domain size of the acrylic resin (B) containing the unevenly distributed conductive particles (C) is smaller than the spacing between the electrodes of opposing circuit components, it is believed that a conductive path is formed between the electrodes of opposing circuit components by applying the anisotropic conductive material to a substrate and curing it under heat and pressure conditions, resulting in the coalescence of the acrylic resin (B) to form a continuous phase. Therefore, it is believed that, although conduction between opposing circuit components is confirmed in a connection structure containing the anisotropic conductive material, the insulation between the electrodes within the same circuit component is maintained. The details of the anisotropic conductive material according to the present invention are described below.

[0013] <<Epoxy Resin (A)>> The epoxy resin (A) is not particularly limited and may be a resin containing one epoxy group per molecule, or a resin containing two or more epoxy groups per molecule. The epoxy resin (A) may be an epoxy resin having an aromatic ring in the main chain, or an epoxy resin having an alicyclic hydrocarbon group or an aliphatic hydrocarbon group in the main chain, but is preferably an epoxy resin having an aromatic ring in the main chain. The term "main chain" refers to the relatively longest bonding chain among the molecules of the polymer compound constituting the resin. The number of epoxy groups contained in the epoxy resin (A) is preferably 2 to 10, more preferably 2 to 6, and even more preferably 2 to 4, from the viewpoints of ease of forming a phase-separated structure with the acrylic resin (B) and curability.

[0014] Examples of epoxy resins having an aromatic ring in the main chain include bisphenol A liquid epoxy resins obtained by reacting bisphenol A with epichlorohydrin in the presence of an alkali, bisphenol A solid epoxy resins, bisphenol F epoxy resins obtained by reacting bisphenol F with epichlorohydrin in the presence of an alkali, brominated resins of these resins, urethane-modified resins of these resins, phenol novolac epoxy compounds, cresol novolac epoxy compounds, cresol epoxy compounds, polyphenol epoxy compounds, and glycidyl ether epoxy compounds such as hydrogenated bisphenol A epoxy compounds. Among these, from the viewpoint of ease of forming a phase-separated structure with the acrylic resin (B), the epoxy resin (A) is preferably a solid epoxy resin, more preferably a bisphenol A solid epoxy resin or a bisphenol F solid epoxy resin, and even more preferably a bisphenol A solid epoxy resin. A solid epoxy resin refers to an epoxy resin that is solid at a temperature of 25°C and a pressure of 1 atm.

[0015] The epoxy resin (A) may be synthesized or may be a commercially available product. Examples of commercially available bisphenol A type solid epoxy resins include those under the trade names "EPICLON 860", "EPICLON 1050", "EPICLON 1055", "EPICLON 3050", "EPICLON 4050", "EPICLON 7050", "EPICLON AM-020-P", "EPICLON AM-040-P", "EPICLON HM-091", "EPICLON AM-092-P ... HM-101 (all manufactured by DIC), "jER1009", "jER1010", "jER1003F", "jER1004F", "jER1005F", "jER1009F", "jER1004FS", "jER1006FS", "jER1007FS", "jER4005P", "jER4007P", and "jER4010P" (all manufactured by Mitsubishi Chemical).

[0016] The weight average molecular weight (Mw) of the epoxy resin (A) is preferably 5,000 to 30,000, more preferably 7,000 to 20,000, and even more preferably 10,000 to 15,000, from the viewpoint of facilitating the formation of a phase-separated structure with the acrylic resin (B). A weight average molecular weight (Mw) of the epoxy resin (A) within the above range is preferred from the viewpoint of ease of handling and control of the flowability of the anisotropic conductive material. The weight average molecular weight (Mw) is a weight average molecular weight measured by gel permeation chromatography (GPC) in terms of standard polystyrene, and is specifically determined by the measurement method described in the Examples.

[0017] The content of the epoxy resin (A) is preferably 50 to 90 mass %, more preferably 60 to 80 mass %, based on the total solid content of the anisotropic conductive material. The epoxy resin (A) may be used alone or in combination of two or more types.

[0018] <<Acrylic Resin (B)>> The acrylic resin (B) contains 0.5 to 49.5 mol % of monomer units derived from a nitrogen atom-containing monomer based on the total monomer units of the acrylic resin (B).

[0019] [Nitrogen Atom-Containing Monomer] The nitrogen atom-containing monomer is not particularly limited as long as it is a monomer containing a group containing a nitrogen atom and a group having a polymerizable double bond. Examples of the nitrogen atom-containing group include an amino group, an amide group, a nitrogen-based heterocyclic group, and a cyano group. The amino group includes *-NH ２ The amino group may be a primary amino group represented by the formula *, a secondary amino group represented by *-NHR, or a tertiary amino group represented by *-NRR'. Here, examples of R and R' include alkyl groups. The * above is preferably a carbon atom, and more preferably a hydrocarbon.

[0020] Examples of the group having a polymerizable double bond include a (meth)acryloyl group, a vinyl group, an allyl group, etc. Among these, the (meth)acryloyl group is preferred as the group having a polymerizable double bond.

[0021] Examples of monomers containing an amino group include N,N-dialkylaminoalkyl(meth)acrylates such as N,N-dimethylaminoethyl(meth)acrylate and N,N-diethylaminoethyl(meth)acrylate. Examples of monomers containing an amide group include N-alkyl(meth)acrylamides such as (meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, and N-hexyl(meth)acrylamide; and N,N-dialkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide and N,N-diethyl(meth)acrylamide. Examples of monomers containing a nitrogen-based heterocyclic group include N-vinylpyrrolidone, N-vinylcaprolactam, and (meth)acryloylmorpholine. Examples of monomers containing a cyano group include cyano(meth)acrylate and (meth)acrylonitrile.

[0022] Among these, preferred nitrogen-atom-containing monomers are monomers containing an amino group, monomers containing a nitrogen-based heterocyclic group, and monomers containing an amide group, with monomers containing a nitrogen-based heterocyclic group and monomers containing an amide group being more preferred, and (meth)acrylamide, N-vinylpyrrolidone, N-vinylcaprolactam, and (meth)acryloylmorpholine being even more preferred. (Meth)acrylamide is particularly preferred because it facilitates the formation of a sea-island structure when the epoxy resin (A) and the acrylic resin (B) are mixed and then applied to a substrate or the like, and the formed sea-island structure is stably maintained. When the sea-island structure is stably maintained, electrical continuity is confirmed between opposing circuit members in a connection structure including an anisotropically conductive material, and insulation between electrodes within the same circuit member is maintained.

[0023] The content of the monomer units derived from the nitrogen atom-containing monomer is 0.5 to 49.5 mol %, preferably 5 to 35 mol %, more preferably 10 to 30 mol %, and even more preferably 15 to 25 mol %, based on the total monomer units of the acrylic resin (B), from the viewpoint of facilitating the formation of a sea-island structure when the epoxy resin (A) and the acrylic resin (B) are mixed and then applied to a substrate, etc. The monomer units derived from the nitrogen atom-containing monomer may be of one type alone or two or more types may be used in combination.

[0024] From the viewpoint of ease of forming an island-sea structure with the epoxy resin (A), the acrylic resin (B) preferably further contains a monomer unit derived from an alkyl(meth)acrylate, more preferably further contains a monomer unit derived from an alkyl(meth)acrylate having an alkyl group with a carbon number of 1 to 20, and even more preferably further contains a structural unit derived from an alkyl(meth)acrylate having an alkyl group with a carbon number of 1 to 12. The alkyl group may be a linear or branched alkyl group.

[0025] Examples of alkyl(meth)acrylates include methyl(meth)acrylate, ethyl(meth)acrylate, n-propyl(meth)acrylate, isopropyl(meth)acrylate, n-butyl(meth)acrylate, isobutyl(meth)acrylate, tert-butyl(meth)acrylate, pentyl(meth)acrylate, hexyl(meth)acrylate, heptyl(meth)acrylate, and 2-ethylhexyl(meth)acrylate. acrylate, n-octyl(meth)acrylate, iso-octyl(meth)acrylate, n-nonyl(meth)acrylate, iso-nonyl(meth)acrylate, n-decyl(meth)acrylate, iso-decyl(meth)acrylate, undeca(meth)acrylate, lauryl(meth)acrylate, oleyl(meth)acrylate, n-stearyl(meth)acrylate, and iso-stearyl(meth)acrylate.

[0026] The acrylic resin (B) preferably contains more than 50 mol% of monomer units derived from alkyl(meth)acrylate (preferably an alkyl(meth)acrylate having an alkyl group with 1 to 20 carbon atoms, more preferably an alkyl(meth)acrylate having an alkyl group with 1 to 12 carbon atoms) relative to all monomer units of the acrylic resin, more preferably more than 50 mol% and not more than 99.5 mol%, even more preferably more than 50 mol% and not more than 70 mol%, and particularly preferably 52 to 60 mol%. One type of alkyl(meth)acrylate may be contained alone, or two or more types may be contained in combination.

[0027] [Other Monomer Units] The acrylic resin (B) may contain monomer units derived from monomers other than the nitrogen atom-containing monomer and the alkyl(meth)acrylate (hereinafter also referred to as "other monomers"). Examples of other monomers include carboxyl group-containing monomers, hydroxyl group-containing monomers, alicyclic hydrocarbon group- or aromatic hydrocarbon group-containing (meth)acrylates, alkoxypolyalkylene glycol mono(meth)acrylates, styrene-based monomers, and vinyl acetate.

[0028] The carboxy group-containing monomer is not particularly limited as long as it is a monomer containing a carboxy group and a polymerizable double bond. Examples of the carboxy group-containing monomer include (meth)acrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid; acid anhydride group-containing monomers such as phthalic anhydride and maleic anhydride; and carboxy group-containing (meth)acrylates such as β-carboxyethyl (meth)acrylate, 5-carboxypentyl (meth)acrylate, succinic acid mono(meth)acryloyloxyethyl ester, and ω-carboxypolycaprolactone mono(meth)acrylate. The carboxy group-containing monomer includes an acid anhydride group-containing monomer that generates a carboxy group upon ring-opening.

[0029] The hydroxyl group-containing monomer is not particularly limited as long as it contains a hydroxyl group and a polymerizable double bond. Examples of the hydroxyl group-containing monomer include hydroxyl group-containing (meth)acrylates such as hydroxyalkyl (meth)acrylates, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate.

[0030] Examples of the (meth)acrylate containing an alicyclic hydrocarbon group or an aromatic hydrocarbon group include cyclohexyl (meth)acrylate, benzyl (meth)acrylate, and phenyl (meth)acrylate.

[0031] Examples of alkoxypolyalkylene glycol mono(meth)acrylates include methoxydiethylene glycol mono(meth)acrylate, methoxydipropylene glycol mono(meth)acrylate, ethoxytriethylene glycol mono(meth)acrylate, ethoxydiethylene glycol mono(meth)acrylate, and methoxytriethylene glycol mono(meth)acrylate.

[0032] Examples of styrene-based monomers include styrene; alkyl styrenes such as methylstyrene, dimethylstyrene, trimethylstyrene, propylstyrene, butylstyrene, hexylstyrene, heptylstyrene, and octylstyrene; halogenated styrenes such as fluorostyrene, chlorostyrene, bromostyrene, and dibromostyrene; and functionalized styrenes such as nitrostyrene, acetylstyrene, and methoxystyrene.

[0033] The content of monomer units derived from other monomers is preferably 5 to 35 mol %, more preferably 10 to 30 mol %, and even more preferably 15 to 25 mol %, based on the total monomer units of the acrylic resin (B).

[0034] From the viewpoint of ease of forming a phase-separated structure with the epoxy resin (A), the weight-average molecular weight (Mw) of the acrylic resin (B) is preferably 1,000 to 30,000, more preferably 5,000 to 25,000, and even more preferably 10,000 to 20,000. The weight-average molecular weight (Mw) is a weight-average molecular weight measured by gel permeation chromatography (GPC) in terms of standard polystyrene, and is specifically determined by the measurement method described in the Examples.

[0035] The content of the acrylic resin (B) is preferably 5 to 30 parts by mass, more preferably 15 to 20 parts by mass, based on 100 parts by mass of the epoxy resin (A). The acrylic resin (B) may be used alone or in combination of two or more types.

[0036] In the anisotropically conductive material, the content of the resin components (for example, the total amount of the epoxy resin (A) and the acrylic resin (B)) is preferably 50 to 99 mass %, more preferably 70 to 98 mass %, based on the total solid content of the anisotropically conductive material.

[0037] Furthermore, from the viewpoints of easily forming a phase-separated structure, and of providing excellent conductivity and maintaining insulating properties when used in a connection structure, the ratio of the epoxy resin (A) to the acrylic resin (B) (epoxy resin (A):acrylic resin (B)) is preferably 10:90 to 90:10, and more preferably 15:85 to 85:15, on a mass basis.

[0038] <Method for producing acrylic resin (B)> The polymerization method for the acrylic resin (B) according to this embodiment is not particularly limited, and examples thereof include solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, etc. Among these, the solution polymerization and bulk polymerization are preferred as the method for producing the acrylic resin (B).

[0039] An example of the solution polymerization method is a method of producing the acrylic resin (B) by charging a polymerization solvent and monomer components into a reaction vessel, adding a polymerization initiator under an inert gas atmosphere such as nitrogen gas, setting the reaction initiation temperature to usually 40 to 100° C., preferably 50 to 90° C., and maintaining the reaction system at a temperature of usually 50 to 90° C., preferably 60 to 90° C., for 3 to 20 hours. In the method for producing the acrylic resin (B), a chain transfer agent may be added at the time of charging, if desired, and the monomer components, polymerization initiator, chain transfer agent, polymerization solvent, etc. may be additionally added as appropriate during the polymerization reaction.

[0040] In one example of bulk polymerization, monomer components are charged into a reaction vessel, and a polymerization initiator is added as needed under an inert gas atmosphere such as nitrogen gas. The addition of the polymerization initiator increases the temperature in the reaction system, but the polymerization reaction is continued without cooling until the temperature in the reaction system drops. When a drop in the temperature in the reaction system is observed, the monomer components are charged into the reaction vessel again, and if desired, a polymerization initiator may also be added to continue the polymerization reaction. After polymerization is complete, an organic solvent is added to obtain a solution containing the acrylic resin (B). In addition, in the method for producing the acrylic resin (B), a chain transfer agent may be added during charging, if desired, or additional monomer components, polymerization initiator, chain transfer agent, polymerization solvent, etc. may be appropriately added during the polymerization reaction.

[0041] Examples of the polymerization initiator include peroxide-based polymerization initiators, azo-based polymerization initiators, etc. Examples of the peroxide-based polymerization initiator include t-butyl hydroperoxide, cumene hydroxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, di-i-propyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxypivalate, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propanol ... propane, 2,2-bis(4,4-di-t-amylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-octylperoxycyclohexyl)propane, 2,2-bis(4,4-di-α-cumylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)butane, and 2,2-bis(4,4-di-t-octylperoxycyclohexyl)butane.

[0042] Examples of the azo polymerization initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2-(carbamoylazo)isobutyronitrile, 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, 2,2'-azobis(2 Examples of the polymerization initiator include azo compounds such as 2,2'-azobis(N,N'-amidinopropane) dihydrochloride, 2,2'-azobis(N,N'-dimethyleneisobutylamidine), 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide], 2,2'-azobis(isobutylamido) dihydrate, 4,4'-azobis(4-cyanopentanoic acid), 2,2'-azobis(2-cyanopropanol), dimethyl-2,2'-azobis(2-methylpropionate), and 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)propionamide). One polymerization initiator may be used alone, or two or more polymerization initiators may be used in combination. Furthermore, the polymerization initiator may be added multiple times during the polymerization.

[0043] The polymerization initiator is used in an amount within a range of usually 0.001 to 5 parts by mass, preferably 0.005 to 3 parts by mass, per 100 parts by mass of the monomer components forming the acrylic resin (B).

[0044] -Chain Transfer Agent- Examples of the chain transfer agent include a dimer of a nucleus-substituted α-methylstyrene such as α-methylstyrene dimer, mercaptans such as n-butyl mercaptan, n-octyl mercaptan, n-lauryl mercaptan, n-dodecyl mercaptan, and t-dodecyl mercaptan, disulfides such as tetramethylthiuram disulfide and tetraethylthiuram disulfide, and 2-ethylhexyl thioglycolate. Among these, the chain transfer agent is preferably a mercaptan, more preferably n-butyl mercaptan, n-octyl mercaptan, n-lauryl mercaptan, n-dodecyl mercaptan, and t-dodecyl mercaptan. The amount of the chain transfer agent is preferably 0.5 to 5 parts by mass, more preferably 2 to 3 parts by mass, per 100 parts by mass of the monomer components forming the acrylic resin (B). Furthermore, when a chain transfer agent is used in the production of the acrylic resin (B), the content of monomer units derived from the chain transfer agent in the acrylic resin (B) is preferably 0.1 to 3 mol %, more preferably 0.5 to 2 mol %, and even more preferably 1 to 2 mol %, based on the total monomer units of the acrylic resin (B). The chain transfer agents may be used alone or in combination of two or more.

[0045] Examples of the polymerization solvent used in producing the acrylic resin (B) include aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane, and n-octane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, cycloheptane, and cyclooctane; ethers such as diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, dibutyl ether, tetrahydrofuran, dioxane, anisole, phenylethyl ether, and diphenyl ether; halogenated hydrocarbons such as chloroform, carbon tetrachloride, 1,2-dichloroethane, and chlorobenzene; esters such as ethyl acetate, propyl acetate, butyl acetate, and methyl propionate; ketones such as acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, and cyclohexanone; amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; nitriles such as acetonitrile and benzonitrile; and sulfoxides such as dimethyl sulfoxide and sulfolane. The polymerization solvent may be used alone or in combination of two or more.

[0046] <<Conductive Particles (C)>> As the conductive particles (C), known particles used in anisotropic conductive materials can be used. From the viewpoint of excellent conductivity when applied to a connection structure, the conductive particles (C) are preferably at least one selected from gold, silver, copper, platinum, nickel, aluminum, palladium, tin, bismuth, zinc, indium, magnesium, tungsten, titanium, and carbon, and more preferably at least one selected from gold, silver, copper, and nickel. These particle materials may be used alone or in combination of two or more. The conductive particles (C) may be particles of alloys of various metals, or may be particles of metal oxides, glass, ceramics, resins, etc., coated with a metal layer on their surfaces, or composite particles formed by combining multiple materials. In addition, when the conductive particles are resin particles coated with a metal layer on their surfaces, examples of the resin particles include particles of epoxy resins, phenolic resins, acrylic resins, styrene-based resins, etc.

[0047] The conductive particles (C) may be surface-treated. When the conductive particles (C) are surface-treated, the conductive particles (C) tend to be unevenly distributed in a specific phase of the phase-separated structure formed by the resin component. The surface treatment method is not particularly limited, and known surface treatment methods can be used. When the conductive particles (C) are surface-treated, the surfaces of the conductive particles (C) are preferably modified with an organic compound.

[0048] Suitable examples of the organic compound include organic acids and salts thereof. Examples of the organic acid and salts thereof include compounds containing a carboxy group and salts thereof. The number of acid groups in the organic acid is not particularly limited and may be one or two or more. Examples of the acid group include a carboxy group, a sulfo group, and a phosphate group. Among these, the acid group is preferably a carboxy group.

[0049] Examples of organic acids or salts thereof include fatty acids such as succinic acid, glutaric acid, adipic acid, oleic acid, lauric acid, stearic acid, palmitic acid, and myristic acid, and salts thereof. Among these, preferred organic acids or salts thereof are lauric acid, stearic acid, palmitic acid, myristic acid, and ammonium salts thereof, because they can easily achieve the desired surface treatment effect with a small amount of use. When an organic acid salt is used as a surface treatment agent, the conductive particles (C) can be surface-treated in water.

[0050] The amount of organic acid or organic acid salt used for surface treatment is preferably in the range of 0.001 to 0.5 parts by mass per 100 parts by mass of the conductive particles (C). When the amount of the surface treatment agent is 0.001 part by mass or more, the effect of the surface treatment and the effect of actively unevenly distributing the conductive particles (C) are easily obtained. When the amount of the surface treatment agent is 0.5 parts by mass or less, the effect of improving conductivity is easily obtained.

[0051] The shape of the conductive particles (C) is not particularly limited, and may be, for example, spherical, rhombus (a shape formed by agglomeration of multiple spheres), plate-like, needle-like, rod-like, or the like.

[0052] The average particle diameter of the conductive particles (C) is preferably 0.01 to 20 μm. When the average particle diameter of the conductive particles (C) is 0.01 μm or more, the conductive particles (C) can be easily mixed into the resin component, and the applicability of the anisotropic conductive material can also be improved. Furthermore, when the average particle diameter of the conductive particles (C) is 20 μm or less, the anisotropic conductive material can be easily uniformly penetrated into narrow gaps when adhering an adherend having a fine structure. From the above viewpoints, the average particle diameter of the conductive particles (C) is preferably 0.01 to 20 μm, more preferably 0.03 to 10 μm, even more preferably 0.05 to 5 μm, and particularly preferably 0.1 μm to 3 μm.

[0053] The average particle size of the conductive particles (C) is the particle size (D50) at 50% of the integrated value of the volume-based particle size distribution determined by a laser diffraction / scattering particle size distribution measuring device.

[0054] The content of the conductive particles (C) is preferably 1 to 70 parts by mass, more preferably 2 to 35 parts by mass, and even more preferably 5 to 35 parts by mass, relative to 100 parts by mass of the epoxy resin (A). The content of the conductive particles (C) can be adjusted depending on the fineness of the electrodes to be connected, etc. The conductive particles (C) may be of one type alone, or two or more types may be used in combination.

[0055] <<Solvent (D)>> The anisotropically conductive material may contain a solvent (D). The solvent (D) is not particularly limited as long as it has the property of being able to uniformly dissolve or disperse the above-mentioned components. Such a solvent (D) is preferably an organic solvent. From the viewpoint of excellent solubility in the above-mentioned resin components, the solvent (D) preferably has a solubility parameter SP value of 8.2 to 10.6 (cal / cm ３ ) ０．５ More preferably, the solvent has a solubility parameter SP value of 8.2 to 9.0 (cal / cm ３ ) ０．５ The difference in SP value between the epoxy resin (A) and the solvent (D) is preferably 0.5 to 4.0 in absolute value. When the difference in SP value between the epoxy resin (A) and the solvent (D) is within this range, the solubility or dispersibility is excellent.

[0056] The solubility parameter SP value is a Fedors solubility parameter, and is determined by the following formula, according to the method described in "R.F. Fedors, Polym. Eng. Sci., 14, 147 (1974)": SP value=(Ev / v) １／２ = (ΣΔe ｉ / ΣΔv ｉ ) １／２ Ev: evaporation energy v: molar volume Δe ｉ : Evaporation energy of each component atom or atomic group Δv ｉ : Molar volume of each atom or atomic group

[0057] Examples of the solvent (D) include toluene, acetone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran (THF), chloroform, dichloromethane, ethyl acetate, propyl acetate, butyl acetate, and propylene glycol monomethyl ether acetate (PGMEA).

[0058] The content of the solvent (D) is preferably 50 to 1500 parts by mass, more preferably 200 to 1000 parts by mass, based on 100 parts by mass of the resin component. The solvent (D) may be used alone or in combination of two or more types.

[0059] <<Other Components>> The anisotropic conductive material may contain components (hereinafter also referred to as “other components”) other than the above-mentioned epoxy resin (A), acrylic resin (B), conductive particles (C), and solvent (D). Examples of the other components include a curing agent, a curing catalyst, a polymerization initiator, a polymerization inhibitor, a polymerization accelerator, a filler, a softener, an accelerator, an antioxidant, a colorant, a flame retardant, a thixotropic agent, and a resin (hereinafter also referred to as “other resin”) other than the above-mentioned epoxy resin (A) and acrylic resin (B).

[0060] - Curing Agent - Examples of the curing agent include aromatic amines such as 4,4'-diaminodiphenylmethane (DDM) and diaminodiphenyl sulfone, aliphatic amines, imidazole derivatives, dicyandiamide, tetramethylguanidine, thiourea-added amines, carboxylic acid anhydrides such as methylhexahydrophthalic anhydride, carboxylic acid hydrazides, carboxylic acid amides, polyphenol compounds, novolac resins, and polymercaptans. Among these, the curing agent is preferably an aromatic amine, and more preferably 4,4'-diaminodiphenylmethane (DDM).

[0061] The curing agent may be used alone or in combination of two or more. The content of the curing agent is preferably 1% by mass or more, more preferably 1 to 50% by mass, based on the total mass of the resin component.

[0062] Examples of the curing catalyst include Lewis acid complexes such as boron trifluoride ethylamine complex. Furthermore, for example, the dicyandiamide may be combined with a urea derivative such as 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) or an imidazole derivative as a curing accelerator. The carboxylic acid anhydride or novolac resin may be combined with a tertiary amine as a curing accelerator.

[0063] The polymerization initiator may be a radical polymerization initiator, such as an azo compound, an organic peroxide, etc. The radical polymerization initiator may generate radicals by heat or light.

[0064] The polymerization inhibitor may be selected from the group consisting of 2,6-di-t-butyl-p-cresol, 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-thiobis(2-methyl-6-t-butylphenol), hydroquinone, 2-t-butylhydroquinone, 2,5-di-t-butylhydroquinone, p-benzoquinone, 2-ethylanthraquinone, dilaurylthiodipropionate, and cupferron. The accelerator may be a salt of a transition metal, such as cobalt naphthenate.

[0065] Other Resins Examples of other resins include thermoplastic resins other than the acrylic resin (B), such as polysulfone, polyethersulfone, polyetherimide, polyimide, polyamide, polyamideimide, polyetherketone, and polyphenylene ether. The content of other resins is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less, relative to the total mass of the resin components, and it is preferable that the other resins are substantially absent.

[0066] The anisotropic conductive material may be an anisotropic conductive cured product. The curing method for the anisotropic conductive material can be appropriately selected depending on the resin component of the anisotropic conductive material. As for the curing conditions, for example, when the anisotropic conductive material is thermally cured, the heating temperature may be, for example, 150°C or higher and 250°C or lower. Furthermore, pressure may be applied during curing. The pressure during pressing may be, for example, 1 MPa or higher and 100 MPa or lower per total area. The time for pressing and heating may be, for example, 1 second or higher and 5 hours or shorter. As a curing method for the anisotropic conductive material, the material may be brought into a semi-cured state by thermal curing, and then the semi-cured material may be attached to an adherend, and then cured by heating and pressurizing.

[0067] The anisotropically conductive cured product preferably has a phase-separated structure, more preferably a phase-separated structure consisting of two component phases, namely, the epoxy resin (A) and the acrylic resin (B). The phase-separated structure may be a sea-island structure, or a bicontinuous structure in which the epoxy resin (A) phase and the acrylic resin (B) phase each form a continuous phase. From the viewpoint of excellent conductivity between opposing circuit components and maintaining insulation between electrodes within the circuit components, the anisotropically conductive cured product more preferably has a phase-separated structure, and the conductive particles (C) are unevenly distributed in the acrylic resin (B) phase in the phase-separated structure. It is believed that when the anisotropically conductive cured product has a phase-separated structure and the conductive particles (C) are unevenly distributed in the acrylic resin (B) phase, the conductive particles (C) come into contact with each other more frequently, effectively forming continuous conductive paths, and exhibiting higher conductivity even with a relatively small amount of conductive particles (C) contained.

[0068] From the viewpoint of achieving excellent conductivity and maintaining insulating properties, the size (width) of the phases other than the continuous phase (i.e., the independent phases) constituting the phase-separated structure is preferably in the range of 1 nm to 20 μm, more preferably 20 nm to 10 μm, and even more preferably 30 nm to 5 μm.

[0069] From the viewpoint of achieving excellent electrical conductivity and maintaining insulating properties, the phase-separated structure is preferably a sea-island structure, and more preferably, the continuous phase is a phase containing the epoxy resin (A) and the independent phase is a phase containing the acrylic resin (B).

[0070] From the viewpoint of achieving excellent conductivity and maintaining insulating properties, the proportion of conductive particles (C) unevenly distributed in domains in the phase-separated structure in the anisotropically conductive cured product (hereinafter, sometimes simply referred to as the "uneven distribution proportion") is preferably 80% or more, more preferably 90% or more, and even more preferably 95% or more.

[0071] The phase-separated structure and the distribution state of the conductive particles (C) can be confirmed using microscopic techniques such as an optical microscope and an electron microscope. Furthermore, they may be identified by using elemental analysis techniques and image processing in combination, if necessary. When observing the phase-separated structure, etching of the sample by solvent treatment, plasma treatment, corona treatment, or the like may also be performed in combination to enhance contrast.

[0072] <Method for Preparing Anisotropically Conductive Material> The method for preparing the anisotropically conductive material is not particularly limited as long as it allows the above-mentioned components to be mixed, and it can be prepared by a known method. For example, a method can be used to mix resin components such as epoxy resin (A) and acrylic resin (B), the above-mentioned conductive particles (C), and, if necessary, a solvent (D) using a known mixer such as a ball mill, a bead mill, or a homodisper. The temperature at which the resin components are mixed is preferably 10 to 200°C, more preferably 15 to 150°C. From the viewpoint of solubility, the mixing time is preferably 20 minutes to 5 hours, more preferably 30 minutes to 4 hours.

[0073] The shape of the anisotropically conductive material is not particularly limited and can be any desired shape depending on the purpose, such as a sheet, a film, or a paste.

[0074] (Anisotropically conductive adhesive sheet) The anisotropically conductive adhesive sheet according to the present invention is a sheet formed from the above-mentioned anisotropically conductive material, and may comprise only a layer formed from the anisotropically conductive material (anisotropically conductive material layer), or may comprise an anisotropically conductive material layer and a layer other than the anisotropically conductive material layer.

[0075] The anisotropically conductive adhesive sheet may also include the anisotropically conductive material layer and a substrate. The substrate used in the anisotropically conductive adhesive sheet is not particularly limited as long as it can be heat-treated. Examples of such substrates include substrates (e.g., films) made of oriented polypropylene (OPP), polyethylene terephthalate (PET), polyethylene naphthalate, polyethylene isophthalate, polybutylene terephthalate, polyolefin, polyacetate, polycarbonate, polyphenylene sulfide, polyamide, polyimide, cellulose, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, synthetic rubber, liquid crystal polymer, etc. The substrate is preferably subjected to a release treatment.

[0076] The thickness of the anisotropic conductive adhesive sheet is not particularly limited, but is usually 10 to 50 μm, and preferably 15 to 40 μm.

[0077] The method for producing the anisotropically conductive adhesive sheet is not particularly limited, and examples include a method in which the above-mentioned anisotropically conductive material is applied to a substrate using a knife coater, roll coater, applicator, comma coater, die coater, etc., dried, and then the anisotropically conductive material layer is peeled off from the substrate.

[0078] (Anisotropic Conductive Paste) The anisotropic conductive paste according to the present invention is a paste formed from the anisotropic conductive material. The anisotropic conductive paste can be manufactured by appropriately preparing the components of the anisotropic conductive material so that they are paste-like. The anisotropic conductive paste is distinguished from the anisotropic conductive adhesive sheet in that the resin component exhibits liquid properties at room temperature, while the anisotropic conductive adhesive sheet is distinguished in that the resin component exhibits solid properties at room temperature but softens or liquefies partially or entirely upon thermocompression bonding. The anisotropic conductive paste is liquid at room temperature or preferably has a viscosity of 50 mPa·s or more and 10,000,000 mPa·s or less at 25°C. The viscosity can be adjusted by the content and type of the solvent (D).

[0079] The anisotropic conductive material can be suitably used as a member for connecting electronic components (i.e., a connection structure). Examples of the connection structure include a first electronic component having a first electrode provided on a substrate, a second electronic component having a second electrode provided on the substrate, and a connection component provided between the first electronic component and the second electronic component. From the viewpoint of achieving excellent conductivity between opposing circuit components and maintaining insulation between electrodes within the circuit components, the connection component is preferably a cured product of the anisotropic conductive material, and the filling rate of the conductive particles (C) in the connection component in the region between the first electrode and the second electrode is preferably higher than the filling rate of the conductive particles (C) in the region other than the region.

[0080] The connection structure preferably comprises a first electronic component having a first substrate and a first electrode provided on the first substrate, a second electronic component having a second substrate and a second electrode provided on the second substrate, and a connection component disposed between the first electronic component and the second electronic component.

[0081] The connecting member is preferably made of a cured product of an anisotropic conductive material, and is composed of an independent phase and a continuous phase forming a phase separation structure, and conductive particles dispersed in the cured product. In the connection structure, the conductive particles are interposed between the first electrode and the second electrode, thereby electrically connecting the first electronic member and the second electronic member to each other.

[0082] <<Substrate>> In the connection structure, the first substrate can be a known substrate used in connection structures, and for example, a resin substrate can be suitably used.

[0083] The resin substrate is preferably a substrate formed from at least one thermoplastic resin selected from polyimide (PI), polyethylene terephthalate (PET), polycarbonate (PC), and polyethylene naphthalate (PEN), more preferably a substrate formed from polyimide (PI). The first substrate may be a single layer or a substrate formed from multiple layers. Examples of substrates formed from two or more resin layers include a substrate having a first resin layer formed from PET or the like and a second resin layer formed from PI or the like. In this case, it is preferable that the second resin layer has better heat resistance than the first resin layer, and the first electrode is preferably provided on the second resin layer.

[0084] The second substrate may be a known substrate used in a connection structure, such as a polymer substrate, a glass substrate, or a ceramic substrate.

[0085] <<Electrode>> The electrode material for forming the first electrode and the second electrode is not particularly limited, and known electrodes can be used. Examples of the electrode include Ag paste, metals such as Ni, Al, Au, Cu, Ti, and Mo, and transparent conductors such as ITO (indium tin oxide), IZO (indium zinc oxide), silver nanowires, and carbon nanotubes.

[0086] The connection structure has excellent conductivity because the conductive particles in the connection member in the region between the first electrode and the second electrode (hereinafter also referred to as the "inter-electrode region") come into contact with each other and a conductive path is formed. There are no limitations as long as a conductive path is formed in the inter-electrode region, but if the filling rate of the conductive particles (C) in the inter-electrode region is higher than the filling rate of the conductive particles (C) in regions other than the inter-electrode region, the conductivity will be better.

[0087] Whether the filling rate of the conductive particles in the connecting member in the inter-electrode region is higher than the filling rate of the conductive particles in the region other than the inter-electrode region can be confirmed by taking out the connecting member portion from the connection structure and examining the cross section of the connecting member using a microscopic technique such as an optical microscope or an electron microscope. The horizontal cross section of the connecting member in the inter-electrode region is enlarged using the microscopic technique, and the area A1 of the observed conductive particles is calculated. The range of the horizontal cross section of the connecting member to be measured is 10,000 μm ２ Depending on the shape of the connection structure, the connection structure may be divided into multiple sections of 10,000 μm ２ The area A2 of the conductive particles in the region other than the inter-electrode region is calculated in the same manner. Thereafter, the ratio (A1 / A2) of the area A1 of the conductive particles in the inter-electrode region to the area A2 of the conductive particles in the region other than the inter-electrode region is determined. From the viewpoint of excellent conductivity and maintaining insulation, the ratio (A1 / A2) is preferably 1 to 1000, more preferably 1 to 100, and even more preferably 1 to 10.

[0088] The electrical resistance in the region between the first electrode and the second electrode is preferably 0 Ω or more and less than 100 Ω, more preferably 0 Ω or more and less than 10 Ω, and even more preferably 0 Ω or more and less than 1 Ω per 100 μm of distance between the electrodes (thickness of the anisotropic conductive material). When the electrical resistance in the region between the first electrode and the second electrode is 0 Ω or more and less than 100 Ω, excellent conductivity between circuit members is achieved.

[0089] (Method for manufacturing a connection structure) The method for manufacturing a connection structure preferably includes the following steps: (1) applying the anisotropically conductive material to a substrate; (2) drying the anisotropically conductive material applied to the substrate in step (1) to obtain an anisotropically conductive adhesive sheet; and (3) placing the anisotropically conductive adhesive sheet obtained in step (2) between a first electronic component and a second electronic component and thermocompression bonding the components (hereinafter also referred to as the "thermocompression bonding step"). By including the thermocompression bonding step, the method for manufacturing a connection structure includes curing the resin component contained in the anisotropically conductive material, forming a phase-separated structure, in which the conductive particles (C) tend to be unevenly distributed in the thickness direction between the first electronic component and the second electronic component. In other words, it is believed that in an anisotropically conductive cured product having a phase-separated structure, resin flow occurs when pressure is applied, and the discrete phase in which the conductive particles (C) are unevenly distributed changes into a continuous phase, making the conductive particles (C) more likely to be unevenly distributed in the thickness direction. On the other hand, it is presumed that in the low pressure or non-pressurized portions, the change in the phase separation structure is small, and therefore the conductive particles (C) contained in the independent phase are less unevenly distributed in the thickness direction. Therefore, a connection structure including an anisotropic conductive material has excellent conductivity between circuit members, and insulation between electrodes within the circuit member is maintained. Furthermore, the connection structure obtained by the above-mentioned method for producing a connection structure tends to have a higher filling rate of the conductive particles (C) in the connection member in the region between the first electrode and the second electrode than the filling rate of the conductive particles (C) in regions other than the region, and has better conductivity.

[0090] <<Step (1)>> Step (1) is a step of applying an anisotropic conductive material to a substrate. The substrate to which the anisotropic conductive material is applied has the same meaning as the substrate in the anisotropic conductive adhesive sheet, and the preferred embodiments are also the same. In addition, examples of a method for applying the anisotropic conductive material to a substrate include the methods listed in the method for producing an anisotropic conductive adhesive sheet.

[0091] <<Step (2)>> Step (2) is a step of drying the anisotropically conductive material applied to the substrate to obtain an anisotropically conductive adhesive sheet. When the anisotropically conductive material contains a solvent (D), drying conditions can be appropriately set according to the type of solvent (D). Drying methods include, for example, heat drying using an oven, a hot plate, infrared rays, etc., and vacuum drying. The drying temperature is preferably 40 to 120°C, and the drying time is preferably 0.1 to 30 minutes.

[0092] A portion of the solvent (D) may remain in the anisotropically conductive adhesive sheet after drying. In this case, the content of the solvent (D) in the anisotropically conductive adhesive sheet is preferably 10 mass % or less, more preferably 5 mass % or less, and even more preferably 1 mass % or less, relative to the total mass of the anisotropically conductive adhesive sheet.

[0093] <<Step (3)>> Step (3) is a thermocompression bonding step in which the anisotropically conductive adhesive sheet obtained in the above step is placed between a first electronic member and a second electronic member and thermocompressed. From the viewpoints of making it easier for the conductive particles (C) to be unevenly distributed in the thickness direction between the first electronic member and the second electronic member, achieving excellent conductivity between opposing circuit members, and maintaining insulation between electrodes in the circuit members, it is preferable to cure the anisotropically conductive material by heating while applying pressure to the entire anisotropically conductive material in the thermocompression bonding step.

[0094] The pressure applied during pressing is preferably 0.1 to 50 MPa, more preferably 1 MPa or more and 50 MPa or less, per total connection area. The heating temperature is preferably 130 to 200°C. The time for pressing and heating may be, for example, 1 second or more and 5 hours or less. In this way, the first electronic member and the second electronic member are thermocompression bonded via the anisotropically conductive material (i.e., the cured product of the anisotropically conductive material).

[0095] <<Other Steps>> The method for manufacturing a connection structure may further include steps other than the thermocompression bonding step (hereinafter also referred to as “other steps”). Examples of the other steps include a step of preparing an electronic component, a step of preparing an anisotropic conductive material, etc.

[0096] The method for manufacturing a connection structure preferably includes a step of preparing an electronic component prior to the thermocompression bonding step. The step of preparing the electronic component may include, for example, a step of preparing a first electronic component having a first substrate and an electrode (first electrode) provided on the first substrate, and a second electronic component having a second substrate and a second electrode provided on the second substrate.

[0097] The step of preparing the anisotropically conductive material is the same as the above-mentioned method of preparing the anisotropically conductive material, and the preferred embodiments are also the same.

[0098] A specific example of the connection structure is a flexible organic electroluminescent color display (organic EL display) in which a driving circuit element serving as a driver for displaying images is mounted on a plastic substrate on which organic EL (electroluminescence) elements are regularly arranged. Another specific example is a so-called touch panel in which a display element such as an organic EL display is combined with a position input device such as a touchpad. The connection structure can be applied to any electronic device that uses electrical connections, such as general-purpose connectors, semiconductor devices (e.g., integrated circuits (ICs)), wiring boards (e.g., flexible printed circuit boards), display devices (e.g., televisions, displays, head-mounted displays), mobile devices (e.g., smartphones, tablet devices, wearable devices), audio equipment, imaging devices (e.g., image sensors), automotive electrical equipment (e.g., navigation systems), medical equipment, sensor devices (e.g., touch sensors, fingerprint authentication, iris authentication), and solar cells.

[0099] In the first electronic component in the specific example described above, a display area may be formed by regularly arranging a pixel driving circuit such as an organic thin film transistor (TFT) and a plurality of organic EL elements R, G, and B in a matrix on a plastic substrate (first substrate) such as PET or PEN. In this display area, signal lines and scanning lines for displaying images are formed in mutually orthogonal directions. In an organic EL display, for example, a set of organic EL elements R, G, and B that emit red, green, and blue light, respectively, constitutes one pixel. The organic layer on which the organic EL elements are formed is covered with a protective layer and sealed by a sealing substrate via an adhesive layer.

[0100] The first electronic component has electrodes for signal lines and scanning lines for displaying images drawn out to the outside of the display area, and is connected to a drive circuit element, which is a driver for displaying images. The electrodes (first electrodes) for the signal lines and scanning lines connected to the drive circuit element are arranged according to the arrangement of bumps provided on the drive circuit element. Furthermore, by using a light-transmitting substrate as the plastic substrate (first substrate), light from the organic EL element can be extracted from the back side of the substrate.

[0101] The second electronic component in the above specific example may be a semiconductor electronic component, specifically, for example, an IC chip or an optical element such as an LED (Light Emitting Diode).The second electrode in such a second electronic component may be a bump electrode such as a gold stud bump or a solder bump.

[0102] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. In the following descriptions of the examples and comparative examples, "parts" means "parts by mass" unless otherwise specified.

[0103] (Production Example 1) A flask equipped with a stirrer, a nitrogen gas inlet tube, a thermometer, and a reflux condenser was charged with 56.99 parts by mass of n-butyl acrylate (BA), 24 parts by mass of N-vinyl caprolactam (NVC), 19 parts by mass of 2-hydroxyethyl acrylate (2HEA), and 2.4 parts by mass of n-dodecyl mercaptan (NDM). While introducing nitrogen gas into the flask, the contents of the flask were heated to 55°C. Next, a solution prepared by dissolving 0.005 parts by mass of 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (product name: V-70, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in 0.5 parts by mass of n-butyl acrylate (BA) as a polymerization initiator was added to the flask with stirring. After adding the polymerization initiator, the polymerization reaction was continued without cooling until a decrease in the reaction system temperature was confirmed. After a decrease in the reaction system temperature was confirmed, the flask was cooled to a temperature of 55°C, and a solution prepared by dissolving 0.005 parts by mass of the polymerization initiator (V-70) in 0.5 parts by mass of n-butyl acrylate (BA) was added. This addition caused the reaction system temperature to rise, but the polymerization reaction was continued until a decrease in the reaction system temperature was confirmed again. When the reaction system temperature reached 55°C, a solution prepared by dissolving 0.2 parts by mass of 2,2'-azobis(isobutyronitrile) (AIBN) in 40 parts by mass of ethyl acetate was added, and an increase in the reaction system temperature was confirmed. The polymerization reaction was continued until a decrease in the reaction system temperature was confirmed again. When the reaction system temperature reached 80°C, the temperature was maintained while the mixture was refluxed for 60 minutes. Thereafter, a solution prepared by dissolving 0.2 parts by mass of AIBN in 40 parts by mass of ethyl acetate was added, and the mixture was refluxed at 80°C for 60 minutes. After the reaction was completed, 20 parts by mass of ethyl acetate was added to the reaction system to obtain a solution containing an acrylic resin (B1) consisting of BA / NVC / 2HEA / NDM=56.1 / 21.8 / 20.6 / 1.5 [mol %]. The weight average molecular weight (Mw) of the acrylic resin (B1) determined by the following measurement method was 19,000.

[0104] <Weight-average molecular weight (Mw)> The weight-average molecular weight (Mw) was determined by gel permeation chromatography (GPC) using standard polystyrene standards under the following conditions: Measurement device: HLC-8220GPC (manufactured by Tosoh Corporation) GPC column configuration: the following five columns in series (all manufactured by Tosoh Corporation): (1) TSK-GEL HXL-H (guard column) (2) TSK-GEL G7000HXL (3) TSK-GEL GMHXL (4) TSK-GEL GMHXL (5) TSK-GEL G2500HXL Sample concentration: 1.0 mg / cm ３ Dilute with tetrahydrofuran so that: Mobile phase solvent: tetrahydrofuran Flow rate: 1.0 cm ３ / min Column temperature: 40 ° C.

[0105] (Production Examples 2 and 3 and Comparative Production Example 1) Acrylic resins (B2), (B3) and (B'1) were produced in the same manner as in Production Example 1, except that the monomer components used were adjusted to the contents shown in Table 1. The numerical values ​​for the monomers and chain transfer agents shown in Table 1 indicate mol%.

[0106]

[0107] In Table 1, "-" means that the corresponding component is not contained. The abbreviations in Table 1 are as follows: BA: n-butyl acrylate NVC: N-vinylcaprolactam AM: acrylamide 2HEA: 2-hydroxyethyl acrylate AA: acrylic acid NDM: n-dodecyl mercaptan BMPA: β-mercaptopropionic acid

[0108] Example 1 100 parts by mass of EPICLON 7050 (product name, manufactured by DIC, Mw: 13000) as epoxy resin (A), 2.6 parts by mass of curing agent (4,4'-diaminodiphenylmethane), 11.1 parts by mass of Ag particles (average particle size 0.5 μm: oleic acid modified; manufactured by DOWA Electronics) as conductive particles (C), and 1000 parts by mass of chloroform were charged into a container and mixed for 10 minutes using an ultrasonic homogenizer. Thereafter, 18 parts by mass of the acrylic resin (B1) prepared above and chloroform (SP value 8.8 (cal / cm)) were added.３ ) ０．５ 120 parts by mass of acrylic resin (B1) was further added and mixed to obtain a resin composition (1) (anisotropic conductive material). The acrylic resin (B1) used was prepared by distilling off the ethyl acetate used in the production.

[0109] <Measurement of Resistance Value> (1) Evaluation of Insulation A 1.5 mm x 35 mm frame was formed on the alkali glass using sealing tape. A few drops of the dispersion solution (1) of Ag particles prepared above were dropped into the frame, left to stand for 5 minutes, the sealing tape was peeled off, and the resultant was dried at 80 ° C for 10 minutes to prepare a test piece (1) in which an anisotropic conductive material was laminated on the alkali glass. Next, an Al plate, a 50 μm thick polytetrafluoroethylene (PTFE) sheet (PTFE sheet), and the test piece (1) were stacked in this order. At this time, the alkali glass side of the test piece (1) (i.e., the side of the test piece (1) not laminated with the anisotropic conductive material) and the PTFE sheet were stacked so that they were in contact. Furthermore, a polyimide film (thickness: 12.5 μm) as a spacer was arranged next to the test piece (1), and then a flexible printed circuit board (FPC, pitch width: 100 μm), a 50 μm PTFE sheet, and an Al plate were stacked on top of them in this order to prepare a connection structure (1). The Al plate laminated on the FPC was then heated and pressed at 180 ° C. and 5 MPa for 30 minutes. The resistance values ​​at five locations between adjacent electrodes of the connected FPC were then measured using a measuring device (manufactured by Hioki E.E., product name: Milliohm High Tester 3540). Since alkali glass is an insulator, measuring the resistance value when alkali glass is used can evaluate the insulation between adjacent electrodes (in the surface direction). (2) Evaluation of Conductivity In the above evaluation, the resistance value between adjacent electrodes was measured in the same manner as above, except that ITO glass was used instead of alkali glass. Since ITO glass exhibits electrical conductivity, the electrical conductivity between adjacent electrodes (in the surface direction) and the electrical conductivity in the thickness direction can be evaluated by measuring the resistance value when ITO glass is used.

[0110] -Evaluation Criteria- If the resistance value (Ω) when using alkali glass is 30,000 or more and even one of the measurement points shows "O.L.", it can be said that insulation between adjacent electrodes (in the plane direction) is maintained. Note that if the resistance value (Ω) at five measurement points is 100 or less, there is conduction between adjacent electrodes (in the plane direction), and it can be said that the insulation is poor. In Table 2 below, "O.L." represents the measurement limit and means that the resistance value is 30,000 or more. If the resistance value (Ω) when using ITO glass is 100 or less, it can be said that the conductivity between opposing electrodes is excellent. In the above evaluation, if the evaluation using alkali glass shows insulation and the evaluation using ITO glass shows conductivity, it can be seen that there is conduction in the thickness direction, and therefore the connection structure exhibits anisotropic conductivity. Furthermore, if conductivity is shown in both the evaluation using alkali glass and the evaluation using ITO glass, it is confirmed that there is conduction in the plane direction, but it is not possible to confirm whether there is conduction in the thickness direction, so it was determined that the connection structure did not exhibit anisotropic conductivity.

[0111] (Examples 2 to 9 and Comparative Example 1) Resin compositions (anisotropic conductive materials) were prepared in the same manner as in Example 1, except that the type of acrylic resin (B) in Example 1 was changed to the acrylic resin shown in Table 2. Test pieces and connection structures were prepared in the same manner as in Example 1, except that the obtained resin compositions and FPCs having pitch widths shown in Table 2 were used, and the resistance values ​​at five locations between adjacent electrodes of the FPC were measured in the same manner as in Example 1. The results are shown in Table 2.

[0112]

[0113] In Table 2, "-" means that the corresponding component is not contained. The abbreviations in Table 2 are as follows: C1: Ag particles (average particle size 0.5 μm: oleic acid modified; manufactured by Dowa Electronics) C2: Ag particles (average particle size 0.8 μm: oleic acid modified; manufactured by Dowa Electronics)

[0114] It can be seen that the connection structures including the anisotropically conductive adhesive sheets of Examples 1 to 9 according to the present invention have excellent conductivity between opposing circuit members and maintain insulation between electrodes within the circuit members compared to the connection structure of Comparative Example 1. In Example 3, it is presumed that a co-continuous phase separation structure is formed in the anisotropically conductive material by increasing the content of acrylic resin (B) in the anisotropically conductive material to 44 parts by mass, and it can be seen that the resistance value when using alkali glass is also lower than, for example, Example 1. It can be said that the connection structure of Example 3 poses no practical problem in terms of insulation between electrodes within the circuit members. Furthermore, although the resistance values ​​using ITO glass of Example 5 and Comparative Example 1 are similar, indicating conductivity, the resistance value using alkali glass is high in Example 5, and insulation is maintained, so it can be said that the anisotropic conductivity of Example 5 poses no practical problem.

Claims

1. An anisotropic conductive material comprising an epoxy resin (A), an acrylic resin (B), and conductive particles (C), wherein the acrylic resin (B) contains 0.5 to 49.5 mol % of monomer units derived from a nitrogen atom-containing monomer relative to the total monomer units of the acrylic resin (B).

2. The anisotropic conductive material according to claim 1, wherein the weight average molecular weight (Mw) of the acrylic resin (B) is 1,000 to 30,000.

3. The anisotropic conductive material according to claim 1, wherein the conductive particles (C) have an average particle size of 0.01 to 20 μm.

4. The anisotropic conductive material according to claim 1, wherein the weight average molecular weight (Mw) of the epoxy resin (A) is 5,000 to 30,000, and the anisotropic conductive material contains a solvent (D).

5. The solubility parameter SP value of the solvent (D) is 8.2 to 10.6 (cal / cm ３ ) ０．５ 5. The anisotropic conductive material according to claim 4, wherein 6. The anisotropic conductive material according to claim 1, wherein the acrylic resin (B) contains more than 50 mol % of monomer units derived from an alkyl (meth)acrylate having an alkyl group with 1 to 12 carbon atoms, based on the total monomer units of the acrylic resin (B).

7. An anisotropic conductive paste formed from the anisotropic conductive material according to any one of claims 1 to 6.

8. An anisotropic conductive adhesive sheet formed from the anisotropic conductive material according to any one of claims 1 to 6.

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