Adhesive film, connection structure, and method for producing connection structure

Abstract

This adhesive film contains a thermoplastic resin and a polymerizable compound. The polymerizable compound contains a bismaleimide compound containing indane rings.

Description

Adhesive film, connecting structure, and method for manufacturing the connecting structure

[0001] This disclosure relates to an adhesive film, a connecting structure, and a method for manufacturing the connecting structure.

[0002] In recent years, various adhesives have been used in fields such as semiconductors and liquid crystal displays to fix electronic components or to connect circuits. As a circuit connection material, anisotropic conductive adhesives containing conductive particles are used for connections such as between liquid crystal displays and tape carrier packages (TCPs), between flexible printed circuit boards (FPCs) and TCPs, between FPCs and printed circuit boards, between semiconductor silicon chips and substrates, between FPCs and touch panel modules, and between FPCs (see, for example, Patent Document 1 below).

[0003] Japanese Patent Publication No. 2004-263122

[0004] As printed circuit boards and similar components become more densely packed or higher-resolution, adhesives used for circuit connections are required to firmly bond components together.

[0005] This disclosure aims to provide an adhesive film that can bond components together more firmly.

[0006] This disclosure relates to the following [1] to [7].

[0007] [1] An adhesive film containing a thermoplastic resin and a polymerizable compound, wherein the polymerizable compound contains a bismaleimide compound containing an indan ring. [2] The adhesive film according to [1], wherein the bismaleimide compound has a structure represented by the following formula (3). [R in equation (3)] １ and R ６ Each independently represents an alkyl group having 1 to 10 carbon atoms, an alkyloxy group having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, an arylthio group having 6 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a halogen atom, a hydroxyl group, or a mercapto group, R ２ , R ３ and R４ Each of these independently represents an alkyl group having 1 to 10 carbon atoms, R ５ and R ７ Each independently represents an alkyl group having 1 to 10 carbon atoms, an alkyloxy group having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, an arylthio group having 6 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a halogen atom, a nitro group, a hydroxyl group, or a mercapto group; X and Y each independently represent a single bond, an alkylene group having 1 to 5 carbon atoms, or an alkylidene group having 2 to 5 carbon atoms; n1 represents an integer from 0 to 3; n2 to n4 each independently represent an integer from 0 to 4; and m represents a number from 0.95 to 10.0. [3] The adhesive film according to [1] or [2], further comprising conductive particles. [4] The adhesive film according to any one of [1] to [3], wherein the polymerizable compound further comprises urethane (meth)acrylate. [5] The adhesive film according to [4], wherein the ratio of the content of the bismaleimide compound to the content of the urethane (meth)acrylate is 0.05 to 1.5 by mass. [6] A connecting structure comprising a first circuit member having a first electrode, a second circuit member having a second electrode, and a connecting portion disposed between the first circuit member and the second circuit member to electrically connect the first electrode and the second electrode, wherein the connecting portion includes a cured product of the adhesive film according to any one of [1] to [5]. [7] A method for manufacturing a connecting structure, comprising the steps of interposing the adhesive film according to any one of [1] to [5] between the first circuit member having a first electrode and the second circuit member having a second electrode, and heat-pressing the first circuit member and the second circuit member to electrically connect the first electrode and the second electrode.

[0008] According to this disclosure, it is possible to provide an adhesive film that can bond components together more firmly.

[0009] This is a schematic cross-sectional view showing one embodiment of the connection structure according to this disclosure. This is a schematic cross-sectional view showing the manufacturing process of the connection structure shown in Figure 1.

[0010] In this specification, numerical ranges indicated using "~" represent a range that includes the numerical values ​​before and after "~" as the minimum and maximum values, respectively. In numerical ranges described stepwise in this specification, the upper or lower limit of a numerical range in one step may be replaced with the upper or lower limit of a numerical range in another step. Also, in numerical ranges described in this specification, the upper or lower limit of that numerical range may be replaced with the values ​​shown in the examples. Furthermore, the upper and lower limits described individually can be combined in any way. In this specification, "(meth)acrylate" means at least one of acrylate and its corresponding methacrylate. The same applies to other similar expressions such as "(meth)acryloyl". Furthermore, "(poly)" means both with and without the prefix "poly". Furthermore, "A or B" means that either A or B is included, or both are included. Furthermore, unless otherwise specified, the materials exemplified below may be used individually or in combination of two or more. The content of each component in a composition refers to the total amount of any multiple substances present in the composition, unless otherwise specified.

[0011] The embodiments of this disclosure will be described in detail below, with reference to the drawings as appropriate. However, this disclosure is not limited to the embodiments described below.

[0012] <Adhesive Film> The adhesive film of this embodiment contains a thermoplastic resin (hereinafter sometimes referred to as "component (A)") and a polymerizable compound (hereinafter sometimes referred to as "component (B)"), wherein the polymerizable compound contains a bismaleimide compound containing an indan ring.

[0013] [(A) Component: Thermoplastic Resin] As the (A) component, one or more resins selected from polyimide resin, polyamide resin, phenoxy resin, poly(meth)acrylic resin, polyester resin, polyurethane resin, polyester urethane resin, and polyvinyl butyral resin can be mentioned. Examples of resin combinations include, for example, a combination of phenoxy resin and poly(meth)acrylic resin, a combination of phenoxy resin and polyester resin, a combination of phenoxy resin and polyester urethane resin, and a combination of phenoxy resin and polyimide resin.

[0014] The polyester resin may be polyethylene naphthalate resin. The polyethylene naphthalate resin can be obtained by subjecting naphthalene dicarboxylic acid ester and diethylene glycol to a transesterification and polycondensation reaction, or by directly polymerizing naphthalene dicarboxylic acid and diethylene glycol. Also, the phenoxy resin can be obtained by reacting bifunctional phenols and epihalohydrin to a high molecular weight, or by subjecting a bifunctional epoxy resin and bifunctional phenols to a polyaddition reaction.

[0015] The adhesive film of this embodiment may contain a rubber component as the (A) component. Examples of the rubber component include silicone rubber, acrylic rubber, polyisoprene rubber, polybutadiene rubber, carboxyl group-terminated polybutadiene rubber, hydroxyl group-terminated polybutadiene rubber, 1,2-polybutadiene rubber, carboxyl group-terminated 1,2-polybutadiene rubber, hydroxyl group-terminated 1,2-polybutadiene rubber, styrene-butadiene rubber, hydroxyl group-terminated styrene-butadiene rubber, acrylonitrile-butadiene rubber, carboxylated nitrile rubber, hydroxyl group-terminated poly(oxypropylene) rubber, alkoxysilyl group-terminated poly(oxypropylene) rubber, poly(oxytetramethylene) glycol rubber, polyolefin glycol rubber, and poly-ε-caprolactone rubber.

[0016] From the viewpoint of film-forming property, the weight-average molecular weight of the thermoplastic resin may be 5,000 or more, may be 10,000 or more, from the viewpoint of adhesiveness, may be 80,000 or less, may be 150,000 or less, and from the viewpoints of adhesiveness and film-forming property, may be 5,000 to 150,000, or may be 10,000 to 80,000. The weight-average molecular weight of the thermoplastic resin means the weight-average molecular weight (standard polystyrene conversion value) measured by GPC (gel permeation chromatography).

[0017] From the viewpoint of film-forming property, the content of component (A) may be 20% by mass or more, or 30% by mass or more, based on the resin components (for example, components other than conductive particles and fillers) of the adhesive film, may be 60% by mass or less, or 50% by mass or less, and may be 20 to 60% by mass, or 30 to 50% by mass.

[0018] Further, the content of component (A) may be 20 parts by mass or more, 25 parts by mass or more, or 30 parts by mass or more, based on 100 parts by mass of the total amount of components (A) and (B), may be 60 parts by mass or less, 50 parts by mass or less, or 45 parts by mass or less, and may be 20 to 60 parts by mass, 25 to 50 parts by mass, or 30 to 45 parts by mass.

[0019] [(B) component: polymerizable compound] Component (B) is, for example, a compound that polymerizes by radicals, cations or anions generated by a polymerization initiator. The polymerization initiator may be a photopolymerization initiator that generates radicals, cations or anions by irradiation with light (for example, ultraviolet light), or may be a thermal polymerization initiator that generates radicals, cations or anions by heat. Component (B) includes a bismaleimide compound containing an indane ring (hereinafter sometimes referred to as "(b1) component"). As component (B), the compounds described below can be used in either monomer or oligomer state, and it is also possible to use a combination of monomer and oligomer.

[0020] ((b1) component: bismaleimide compound containing an indane ring) Component (b1) may be a bismaleimide compound represented by the following formula (1).

[0021] In the above formula (1), L １ is a divalent organic group containing an indane ring.

[0022] In this specification, the indane ring means a condensed bicyclic structure of an aromatic 6-membered ring and a saturated aliphatic 5-membered ring. The indane ring may be included in the component (b1) as a divalent organic group represented by the following formula (2).

[0023] In the above formula (2), R １ represents an alkyl group having 1 to 10 carbon atoms, an alkyloxy group having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, an arylthio group having 6 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a halogen atom, a hydroxyl group or a mercapto group, and n1 represents an integer of 0 to 3. R ２ , R ３ and R ４ each independently represent an alkyl group having 1 to 10 carbon atoms. Note that * represents a bonding site.

[0024] Examples of the alkyl group having 1 to 10 carbon atoms represented by R １ include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group and the like. These alkyl groups may be either linear or branched.

[0025] Examples of the alkyl group contained in the alkyloxy group having 1 to 10 carbon atoms and the alkylthio group having 1 to 10 carbon atoms represented by R １ are the same as those of the above alkyl group having 1 to 10 carbon atoms.

[0026] Examples of the aryl group having 6 to 10 carbon atoms represented by R １ include a phenyl group, a naphthyl group and the like.

[0027] Examples of the aryl group contained in the aryloxy group having 6 to 10 carbon atoms and the arylthio group having 6 to 10 carbon atoms represented by R １ are the same as those of the above aryl group having 6 to 10 carbon atoms.

[0028] R１ Examples of cycloalkyl groups having 3 to 10 carbon atoms represented by the formula include cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, cyclononyl group, and cyclodecyl group.

[0029] If n1 in equation (2) above is an integer from 1 to 3, then R １ From the viewpoint of solvent solubility and reactivity, alkyl groups having 1 to 4 carbon atoms, cycloalkyl groups having 3 to 6 carbon atoms, and aryl groups having 6 to 10 carbon atoms are preferred, with alkyl groups having 1 to 4 carbon atoms being more preferred. In formula (2) above, n1 is an integer from 0 to 3, and when n1 is 2 or 3, there are multiple R １ They may be the same or they may be different.

[0030] R ２ ~R ４ Examples of C1-C10 alkyl groups represented by include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl groups. These alkyl groups may be linear or branched. Among these, R ２ ~R ４ The alkyl group is preferably a C1-C4 alkyl group, more preferably a methyl group or an ethyl group, and even more preferably a methyl group.

[0031] (b1) The component may be a compound represented by the following formula (3).

[0032] In the above formula (3), R １ and R ６ These are R in equation (2) above. １ This is equivalent to the above equation (3), and R １ and R ６ R in formula (3) above may be the same or may be different. ２ , R ３ and R ４ These are R in equation (2) above. ２ , R ３ and R ４ This is equivalent to the above equation (3), and R ２ , R ３ and R４ They may be the same or they may be different. ５ and R ７ Each independently represents an alkyl group having 1 to 10 carbon atoms, an alkyloxy group having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, an arylthio group having 6 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a halogen atom, a nitro group, a hydroxyl group, or a mercapto group. Each independently represents a single bond, an alkylene group having 1 to 5 carbon atoms, or an alkylidene group having 2 to 5 carbon atoms. In formula (3) above, n1 is the same as n1 in formula (2) above, n2 to n4 each independently represent an integer from 0 to 4, and m represents a number from 0.95 to 10.0.

[0033] If n1 in the above equation (3) is an integer from 1 to 3, then R １ From the viewpoint of solvent solubility and reactivity, alkyl groups having 1 to 4 carbon atoms, cycloalkyl groups having 3 to 6 carbon atoms, and aryl groups having 6 to 10 carbon atoms are preferred, with alkyl groups having 1 to 4 carbon atoms being more preferred. When n1 in formula (3) above is 2 or 3, multiple R １ These may be the same or different. In equation (3) above, n2 to n4 are each an independent integer from 0 to 4. If n2 is one of 2 to 4, then multiple R ５ The same or different Rs may be identical. If n3 is any of 2 to 4, then there are multiple Rs. ６ The same or different Rs may be identical. If n4 is any of 2 to 4, then multiple Rs may be involved. ７ They may be the same or they may be different.

[0034] R ５ and R ７ As for the C1-C10 alkyl group, C1-C10 alkyloxy group, C1-C10 alkylthio group, C6-C10 aryl group, C6-C10 aryloxy group, C6-C10 arylthio group, and C3-C10 cycloalkyl group represented by R １Examples include C1-C10 alkyl groups, C1-C10 alkyloxy groups, C1-C10 alkylthio groups, C6-C10 aryl groups, C6-C10 aryloxy groups, C6-C10 arylthio groups, and C3-C10 cycloalkyl groups.

[0035] Among these, R ５ and R ７ From the viewpoint of solvent solubility and ease of manufacture, each is preferably an alkyl group having 1 to 4 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, or an aryl group having 6 to 10 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and even more preferably a methyl group.

[0036] In formula (3) above, n2 and n4 are integers from 0 to 4, and are preferably integers from 0 to 3, more preferably 0 or 2, from the viewpoint of compatibility with other resins, dielectric properties, adhesion to conductors, and ease of manufacture. When n2 and n4 are 1 or more, the benzene ring and the N-substituted maleimide group have a twisted conformation, and solvent solubility tends to be further improved by suppressing intermolecular stacking. From the viewpoint of suppressing intermolecular stacking, when n2 and n4 are 1 or more, R ５ and R ７ The substitution position is preferably the ortho position relative to the N-substituted maleimide group.

[0037] Examples of C1-C5 alkylene groups represented by X and Y include methylene groups, 1,2-dimethylene groups, 1,3-trimethylene groups, 1,4-tetramethylene groups, and 1,5-pentamethylene groups. C1-C5 alkylene groups are preferably C1-C3 alkylene groups, more preferably C1 or C2 alkylene groups, and even more preferably methylene groups.

[0038] Examples of alkylidene groups having 2 to 5 carbon atoms represented by X and Y include ethylidene, propyridene, isopropylidene, butyridene, isobutylidene, pentyridene, and isopentylidene. Among the alkylidene groups having 2 to 5 carbon atoms, alkylidene groups having 2 to 4 carbon atoms are preferred, alkylidene groups having 2 or 3 carbon atoms are more preferred, and isopropylidene groups are even more preferred.

[0039] In formula (3) above, m is preferably a value of 0.98 to 8.0, more preferably a value of 1.0 to 7.0, and even more preferably a value of 1.1 to 6.0, from the viewpoint of dielectric properties, adhesion, solvent solubility, handling properties, and heat resistance. Note that m represents the average value of the number of structural units containing indan rings.

[0040] Examples of the (b1) component represented by formula (3) above include the compound represented by formula (3A) below, the compound represented by formula (3B) below, the compound represented by formula (3C) below, and the compound represented by formula (3D) below. The m in formulas (3A), (3B), (3C), and (3D) are the same as the m in formula (3) above.

[0041] The number-average molecular weight (Mn) and weight-average molecular weight (Mw) of the bismaleimide represented by formula (3) are not particularly limited. The Mn of the bismaleimide represented by formula (3) may be 600 to 2000, 700 to 1800, or 800 to 1400, from the viewpoint of compatibility with other components, adhesion to conductors, and heat resistance. The weight-average molecular weight (Mw) of the bismaleimide represented by formula (3) may be 1000 to 4000, 1200 to 3500, or 1800 to 3000, from the viewpoint of compatibility with other components, adhesion to conductors, and heat resistance. Mn and Mw can be measured by gel permeation chromatography (GPC) and converted using a calibration curve for standard polystyrene.

[0042] The method for producing component (b1) represented by formula (3) above is not particularly limited. Component (b1) represented by formula (3) above can be produced, for example, by the method described in the Japan Institute of Invention and Innovation Published Technical Report No. 2020-500211. According to the production method described in the Japan Institute of Invention and Innovation Published Technical Report No. 2020-500211, a bismaleimide compound containing an indane skeleton can be obtained.

[0043] The content of component (b1) may be 5 to 70% by mass, 5 to 65% by mass, 5 to 60% by mass, 5 to 40% by mass, or 5 to 35% by mass, based on the total mass of component (B), from the viewpoint of reducing the stickiness of the composition. Furthermore, from the viewpoint of providing superior durability of the adhesive strength of the cured adhesive film, the content of component (b1) may be 5 to 30% by mass, 5 to 25% by mass, or 5 to 20% by mass, based on the total mass of component (B).

[0044] (Component (b2): Urethane (meth)acrylate) The polymerizable compound may contain urethane (meth)acrylate (hereinafter sometimes referred to as "component (b2)"). Urethane (meth)acrylate is a (meth)acrylate compound having one or more urethane bonds. Component (b2) may be a (poly)urethane (meth)acrylate compound having an allophanate bond (-NH-CO-N-COO- group) in the molecule.

[0045] Incidentally, adhesives used for circuit connections are often supplied in the form of a film with a separator, from the viewpoint of process simplicity. Film-type adhesives with separators are used by adhering them to circuit members, then peeling off the separator to connect the circuit members. Such film-type adhesives are required to have sufficient adhesion to circuit members in order to connect them to each other. If the adhesion of the film is low, during the production process of the connection structure, when the separator is peeled off in the process of laminating (temporarily pressing) the film to the circuit members, the film also peels off from the circuit members, resulting in a decrease in productivity. There is a method to increase the tackiness of the film-type adhesive in order to ensure sufficient adhesion, but films with high tackiness tend to be difficult to peel off from the separator and are difficult to handle. In this embodiment, when the polymerizable compound contains component (b2), the adhesion of the adhesive film to the adherend can be improved, and the tackiness of the adhesive film can be made appropriate.

[0046] (b2) The component may be trifunctional or tetrafunctional.

[0047] (b2) The content of component (b2) may be 10 to 70% by mass, 20 to 65% by mass, 30 to 60% by mass, or 35 to 55% by mass, based on the total mass of component (B), from the viewpoint of having superior durability of the adhesive strength of the cured adhesive film and superior adhesion.

[0048] Furthermore, the content of component (b2) may be 15 to 50% by mass, 20 to 45% by mass, or 25 to 40% by mass, based on the total mass of the resin components of the adhesive film (for example, components other than conductive particles and fillers), from the viewpoint of having superior durability of the adhesive strength of the cured adhesive film and superior adhesion.

[0049] Furthermore, the content of component (b2) may be 45 to 90 parts by mass, 50 to 88 parts by mass, 55 to 86 parts by mass, or 70 to 86 parts by mass per 100 parts by mass of the total content of component (b1) and component (b2), from the viewpoint of superior adhesion. The content of component (b2) may be 30 to 90 parts by mass, 40 to 88 parts by mass, or 45 to 86 parts by mass per 100 parts by mass of the total content of component (b1) and component (b2), from the viewpoint of superior adhesion.

[0050] The ratio of the content of component (b1) to the content of component (b2) (component (b1) / component (b2)) may be 0.05 to 1.5, 0.1 to 1.35, or 0.15 to 1.2 by mass, from the viewpoint of the film having appropriate tackiness, and may also be 0.1 to 1.0 or 0.1 to 0.5 from the viewpoint of excellent adhesion of the film. Furthermore, the ratio of the content of component (b1) to the content of component (b2) (component (b1) / component (b2)) may be 0.1 to 0.4 or 0.1 to 0.35 from the viewpoint of superior durability of the adhesive strength of the cured adhesive film.

[0051] (b2) Component has a weight-average molecular weight of 1.0 × 10 ４ It may be greater than or equal to 1.0 × 10 ４ The above 1.0 x 10 ６ The following values ​​may also be used. Note that the weight-average molecular weight refers to the value obtained by measuring with gel permeation chromatography (GPC) and converting it using a calibration curve with standard polystyrene.

[0052] The adhesive film of this embodiment may further contain, as component (B), other polymerizable compounds other than components (b1) and (b2). Examples of other polymerizable compounds include maleimide compounds other than component (b1), (meth)acrylate compounds other than component (b2), vinyl ether compounds, allyl compounds, styrene derivatives, acrylamide derivatives, nadiimide derivatives, natural rubber, isoprene rubber, butyl rubber, nitrile rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, carboxylated nitrile rubber, and the like.

[0053] Examples of (meth)acrylate compounds include epoxy (meth)acrylate, methyl (meth)acrylate, polyether (meth)acrylate, polyester (meth)acrylate, polybutadiene (meth)acrylate, silicone acrylate, ethyl (meth)acrylate, 2-cyanoethyl (meth)acrylate, 2-(2-ethoxyethoxy)ethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-hexyl (meth)acrylate, and 2-hydroxy Ethyl (meth)acrylate, isopropyl (meth)acrylate, hydroxypropyl (meth)acrylate, isobutyl (meth)acrylate, isobornyl (meth)acrylate, isodecyl (meth)acrylate, isooctyl (meth)acrylate, n-lauryl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, 2-(meth)acryloyloxyethyl phosphate, N,N-dimethylaminoethyl ( Meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, polyethylene glycol di(meth)acrylate, polyalkylene glycol di(meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, neopentyl Licol di(meth)acrylate, pentaerythritol(meth)acrylate, dipentaerythritol hexa(meth)acrylate, isocyanuric acid-modified bifunctional(meth)acrylate, isocyanuric acid-modified trifunctional(meth)acrylate, tricyclodecanyl acrylate, dimethylol-tricyclodecane diacrylate, 2-hydroxy-1,3-diacroxypropane, 2,2-bis[4-(acryloxymethoxy)phenyl]propane, 2,2-bis[4-(acryloxypolyethoxy)phenyl]propane, 2,Examples include 2-di(meth)acryloyloxydiethyl phosphate and 2-(meth)acryloyloxyethyl acid phosphate.

[0054] Maleimide compounds include 1-methyl-2,4-bismaleimidebenzene, N,N'-m-phenylenebismaleimide, N,N'-p-phenylenebismaleimide, N,N'-m-toluenebismaleimide, N,N'-4,4-biphenylenebismaleimide, N,N'-4,4-(3,3'-dimethyl-biphenylene)bismaleimide, N,N'-4,4-(3,3'-dimethyldiphenylmethane)bismaleimide, N,N'-4,4-(3,3'-diethyldiphenylmethane)bismaleimide, N,N'-4,4-diphenylmethanebismaleimide, and N,N'-4,4-diphenylp Examples include ropanebismaleimide, N,N'-4,4-diphenyletherbismaleimide, N,N'-3,3-diphenylsulfonbismaleimide, 2,2-bis(4-(4-maleimoidphenoxy)phenyl)propane, 2,2-bis(3-s-butyl-4-(4-maleimoidphenoxy)phenyl)propane, 1,1-bis(4-(4-maleimoidphenoxy)phenyl)decane, 4,4'-cyclohexylidene-bis(1-(4-maleimoidphenoxy)-2-cyclohexyl)benzene, and 2,2'-bis(4-(4-maleimoidphenoxy)phenyl)hexafluoropropane.

[0055] Examples of vinyl ether compounds include diethylene glycol divinyl ether, dipropylene glycol divinyl ether, cyclohexanedimethanol divinyl ether, and trimethylolpropane trivinyl ether.

[0056] Examples of allyl compounds include 1,3-diallyl phthalate, 1,2-diallyl phthalate, and triallyl isocyanurate.

[0057] Other polymerizable compounds may be (meth)acrylate compounds having a high Tg skeleton, such as a tricyclodecane skeleton, from the viewpoint of improving cohesive force, further reducing connection resistance, excellent adhesion, and superior bonding properties.

[0058] The adhesive film according to this embodiment may further contain conductive particles (hereinafter sometimes referred to as "component (C)"). With the increasing density or resolution of printed circuit boards and the like, adhesives used for circuit connections are required to stably reduce the connection resistance between opposing electrodes when connecting circuit members. When the adhesive film according to this embodiment contains component (C), it can reduce the connection resistance when connecting circuit members.

[0059] [Component (C): Conductive Particles] Component (C) is not particularly limited as long as it is conductive, and may be metal particles composed of metals such as Au, Ag, Ni, Cu, or solder, or conductive carbon particles composed of conductive carbon. The conductive particles may also be coated conductive particles comprising a core containing non-conductive glass, ceramic, or plastic (such as polystyrene), and a coating layer containing the above-mentioned metal or conductive carbon that covers the core. Among these, coated conductive particles comprising a core containing metal particles or plastic formed from a heat-meltable metal, and a coating layer containing metal or conductive carbon that covers the core are preferably used. In this case, since the cured product of the adhesive film can be easily deformed by heating or pressurizing, the contact area between the electrodes and the conductive particles can be increased when electrically connecting the electrodes, thereby further improving the conductivity between the electrodes.

[0060] The conductive particles may be the above-mentioned metal particles, conductive carbon particles, or coated conductive particles, and insulating coated conductive particles comprising an insulating layer that covers the surface of the particles and contains an insulating material such as resin. When the conductive particles are insulating coated conductive particles, even if the conductive particle content is high, the surface of the particles is coated with resin, so the occurrence of short circuits due to contact between conductive particles can be suppressed, and the insulation between adjacent electrode circuits can also be improved. Component (C) may be one of the above-mentioned conductive particles used alone or in combination of two or more types.

[0061] The maximum particle size of conductive particles must be smaller than the minimum electrode spacing (the shortest distance between adjacent electrodes). From the viewpoint of excellent dispersibility and conductivity, the maximum particle size of conductive particles may be 1.0 μm or larger, 2.0 μm or larger, or 2.5 μm or larger. From the viewpoint of excellent dispersibility and conductivity, the maximum particle size of conductive particles may be 50 μm or smaller, 30 μm or smaller, or 20 μm or smaller. In this specification, the particle size of any 300 conductive particles (pcs) is measured by observation using a scanning electron microscope (SEM), and the largest value obtained is taken as the maximum particle size of the conductive particles. If the conductive particles have protrusions or are not spherical, the particle size of the conductive particles is taken as the diameter of the circle circumscribing the conductive particles in the SEM image.

[0062] The average particle size of conductive particles may be 1.0 μm or larger, 2.0 μm or larger, or 2.5 μm or larger, from the viewpoint of excellent dispersibility and conductivity. The average particle size of conductive particles may be 50 μm or smaller, 30 μm or smaller, or 20 μm or smaller, from the viewpoint of excellent dispersibility and conductivity. In this specification, the particle size of any 300 conductive particles (pcs) is measured by observation using a scanning electron microscope (SEM), and the average value of the obtained particle sizes is defined as the average particle size.

[0063] In the adhesive film, it is preferable that component (C) is uniformly dispersed. From the viewpoint of obtaining stable connection resistance, the particle density of conductive particles in the adhesive film should be 100 pcs / mm². ２ The above is sufficient, and 1000 pcs / mm ２ The above is sufficient, and 2000 pcs / mm ２ The above is acceptable. The particle density of conductive particles in the adhesive film should be 100,000 pcs / mm² from the viewpoint of improving the insulation between adjacent electrodes. ２ The following may be true: 50,000 pcs / mm ２ The following may be true: 10,000 pcs / mm ２ The following is acceptable:

[0064] The content of component (C) may be 0.1% by volume or more, 1% by volume or more, or 5% by volume or more, based on the total volume of the adhesive film, from the viewpoint of further improving conductivity. The content of component (C) may be 50% by volume or less, 30% by volume or less, or 20% by volume or less, based on the total volume of the adhesive film, from the viewpoint of easily suppressing short circuits. The content of conductive particles in the adhesive film (based on the total volume of the adhesive film) may be the same as the above range.

[0065] (Other components) The adhesive film may further contain other components besides components (A), (B), and (C). Examples of other components include polymerization initiators, coupling agents, and fillers.

[0066] Examples of polymerization initiators include radical polymerization initiators and cationic polymerization initiators. The type of polymerization initiator can be appropriately selected according to the type of components in the adhesive film.

[0067] The polymerization initiator may be a photopolymerization initiator (photoradical polymerization initiator, photocationic polymerization initiator, or photoanionic polymerization initiator) that generates radicals, cations, or anions upon irradiation with light containing wavelengths in the range of 150 to 750 nm, preferably light containing wavelengths in the range of 254 to 405 nm, and more preferably light containing a wavelength of 365 nm (e.g., ultraviolet light), or a thermal polymerization initiator (thermal radical polymerization initiator, thermal cationic polymerization initiator, or thermal anionic polymerization initiator) that generates radicals, cations, or anions upon heat. From the viewpoint of superior connection reliability and easier curing at low temperatures and in short times, the polymerization initiator is preferably a radical polymerization initiator (photoradical polymerization initiator or thermal radical polymerization initiator). A single compound may be used as the polymerization initiator, or a combination of multiple compounds may be used. For example, the adhesive film may contain both a photopolymerization initiator and a thermal polymerization initiator as polymerization initiators.

[0068] Photoradical polymerization initiators decompose upon exposure to light, generating free radicals. In other words, photoradical polymerization initiators are compounds that generate radicals upon application of external light energy. Examples of photoradical polymerization initiators include compounds having structures such as oxime ester structures, bisimidazole structures, acridine structures, α-aminoalkylphenone structures, aminobenzophenone structures, N-phenylglycine structures, acylphosphine oxide structures, benzyldimethylketal structures, and α-hydroxyalkylphenone structures. From the viewpoint of superior connection reliability, it is preferable that photoradical polymerization initiators have at least one structure selected from the group consisting of oxime ester structures, α-aminoalkylphenone structures, and acylphosphine oxide structures.

[0069] Specific examples of compounds having an oxime ester structure include 1-phenyl-1,2-butanedione-2-(o-methoxycarbonyl)oxime, 1-phenyl-1,2-propanedione-2-(o-methoxycarbonyl)oxime, 1-phenyl-1,2-propanedione-2-(o-ethoxycarbonyl)oxime, 1-phenyl-1,2-propanedione-2-o-benzoyloxime, 1,3-diphenylpropanetrione-2-(o-ethoxycarbonyl)oxime, 1-phenyl-3-ethoxypropanetrione-2-(o-benzoyl)oxime, 1,2-octanedione, 1-[4-(phenylthio)phenyl-,2-(o-benzoyloxime)], etanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]-,1-(o-acetyloxime), and the like.

[0070] Specific examples of compounds having an α-aminoalkylphenone structure include 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one and 2-benzyl-2-dimethylamino-1-morpholinophenyl)-butanone-1.

[0071] Specific examples of compounds having an acylphosphine oxide structure include bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

[0072] Thermal radical polymerization initiators decompose upon heat, generating free radicals. In other words, thermal radical polymerization initiators are compounds that generate radicals when external thermal energy is applied. Thermal radical polymerization initiators can be arbitrarily selected from conventionally known organic peroxides and azo compounds. From the viewpoint of stability, reactivity, and compatibility, organic peroxides with a one-minute half-life temperature of 90 to 175°C and a weight-average molecular weight of 180 to 1000 are preferably used as thermal radical polymerization initiators. Having a one-minute half-life temperature within this range provides even better storage stability, sufficiently high radical polymerizability, and enables curing in a short time.

[0073] Specific examples of organic peroxides include 1,1,3,3-tetramethylbutyl peroxyneodecanoate, di(4-t-butylcyclohexyl) peroxydicarbonate, di(2-ethylhexyl) peroxydicarbonate, cumyl peroxyneodecanoate, dilauroyl peroxide, 1-cyclohexyl-1-methylethyl peroxyneodecanoate, t-hexyl peroxyneodecanoate, t-butyl peroxyneodecanoate, t-butyl peroxypivalate, 1,1,3,3-Tetramethylbutylperoxy-2-ethylhexanoate, 2,5-Dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, t-Hexylperoxy-2-ethylhexanoate, t-Butylperoxy-2-ethylhexanoate, t-Butylperoxyneoheptanoate, t-Amylperoxy-2-ethylhexanoate, Di-t-Butylperoxyhexahydroterephthalate, t-Amylperoxy-3,5,5-trimethylhexanoate t-hydroxy-1,1-dimethylbutyl peroxyneodecanoate, t-amyl peroxyneodecanoate, t-amyl peroxy-2-ethylhexanoate, di(3-methylbenzoyl) peroxide, dibenzoyl peroxide, di(4-methylbenzoyl) peroxide, t-hexyl peroxyisopropyl monocarbonate, t-butyl peroxymaleic acid, t-butyl peroxy-3,5,5-trimethylhexanoate, t-butyl peroxylau Examples include phosphate, 2,5-dimethyl-2,5-di(3-methylbenzoylperoxy)hexane, t-butylperoxy-2-ethylhexyl monocarbonate, t-hexylperoxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butylperoxybenzoate, dibutylperoxytrimethyladipate, t-amylperoxyn-octoate, t-amylperoxyisononanoate, and t-amylperoxybenzoate.

[0074] Specific examples of azo compounds include 2,2'-azobis-2,4-dimethylvaleronitrile, 1,1'-azobis(1-acetoxy-1-phenylethane), 2,2'-azobiisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 4,4'-azobis(4-cyanovaleric acid), and 1,1'-azobis(1-cyclohexanecarbonitride).

[0075] The polymerization initiator content may be 0.1% by mass or more, or 0.5% by mass or more, based on the total mass of the adhesive film, from the viewpoint of excellent rapid curing properties and excellent effect in reducing connection resistance. The polymerization initiator content 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 film, from the viewpoint of improved storage stability and excellent effect in reducing connection resistance.

[0076] From the viewpoint of facilitating the manufacture of the cured adhesive film, the adhesive film preferably contains at least one of a photopolymerization initiator and a thermal polymerization initiator as a polymerization initiator, and more preferably contains a thermal polymerization initiator.

[0077] From the viewpoint of pot life, the content of the polymerization initiator may be 0.1% by mass or more, 0.5% by mass or more, or 1% by mass or more, 20% by mass or less, 10% by mass or less, or 5% by mass or less, or 0.1 to 20% by mass, 0.5 to 10% by mass, or 1 to 5% by mass, based on the total mass of the resin components of the adhesive film (e.g., components other than conductive particles and fillers).

[0078] Examples of coupling agents include silane coupling agents having organic functional groups such as (meth)acryloyl groups, mercapto groups, amino groups, imidazole groups, and epoxy groups; silane compounds such as tetraalkoxysilanes; tetraalkoxytitanate derivatives; and polydialkyltitanate derivatives. When the adhesive film contains a coupling agent, the adhesive properties can be further improved. The content of the coupling agent may be, for example, 0.1% by mass or more and 20% by mass or less based on the total mass of the adhesive film.

[0079] Examples of fillers include non-conductive fillers (e.g., non-conductive particles). When the adhesive film contains a filler, further improvement in connection reliability can be expected. The filler may be either an inorganic filler or an organic filler. Examples of inorganic fillers include metal oxide nanoparticles such as silica nanoparticles, alumina nanoparticles, silica-alumina nanoparticles, titania nanoparticles, and zirconia nanoparticles; and inorganic nanoparticles such as nitride nanoparticles. Examples of organic fillers include organic nanoparticles such as silicone nanoparticles, methacrylate-butadiene-styrene nanoparticles, acrylic-silicone nanoparticles, polyamide nanoparticles, and polyimide nanoparticles. These nanoparticles may have a uniform structure or a core-shell structure. Preferably, the maximum diameter of the filler is less than the minimum particle size of the conductive particles. The filler content may be 0.1% by volume or more and 50% by volume or less, based on the total volume of the adhesive film.

[0080] (Other Additives) The adhesive film may contain other additives such as softeners, accelerators, degradation inhibitors, colorants, flame retardants, and thixotropic agents. The content of these additives may be, for example, 0.1 to 10% by mass of the total mass of the adhesive film. These additives may also be contained in the cured product of the adhesive film.

[0081] The thickness of the adhesive film may be set appropriately according to the height of the electrodes of the circuit components to be bonded. For example, the thickness of the adhesive film may be 0.5 μm or more, or 20 μm or less.

[0082] The adhesive film may or may not have anisotropic conductivity. That is, the adhesive film may be anisotropic conductive adhesive film or a non-anisotropic conductive (e.g., isotropic conductive) adhesive film. The adhesive film may be interposed between a first circuit member having a first electrode (the surface on which the first electrode is provided) and a second circuit member having a second electrode (the surface on which the second electrode is provided), and used to electrically connect the first electrode and the second electrode (via conductive particles (or molten solidified conductive particles)) by thermocompressing the first circuit member and the second circuit member (by heating the laminate including the first circuit member, the adhesive film, and the second circuit member while pressing it in the thickness direction of the laminate).

[0083] The adhesive film of this embodiment can be produced by the following method. Specifically, first, components (A) and (B), as well as other components such as polymerization initiators added as needed, are added to a solvent (organic solvent), and dissolved or dispersed by stirring, mixing, kneading, etc., to prepare a varnish composition (varnish-like adhesive composition). Then, the varnish composition is applied to a substrate that has been treated with a release agent using a knife coater, roll coater, applicator, comma coater, die coater, etc., and the solvent is evaporated by heating to form an adhesive film on the substrate.

[0084] The solvent used in preparing the varnish composition may be one that has the property of uniformly dissolving or dispersing each component. Examples of such solvents include toluene, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, propyl acetate, and butyl acetate. These solvents can be used individually or in combination of two or more. The stirring, mixing, and kneading during the preparation of the varnish composition can be carried out using, for example, a stirrer, a sieve, a three-roll mill, a ball mill, a bead mill, or a homodisper.

[0085] The substrate is not particularly limited as long as it has heat resistance that can withstand the heating conditions when the solvent is evaporated. For example, substrates (e.g., films) made of stretched 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., can be used.

[0086] The heating conditions for volatilizing the solvent from the varnish composition applied to the substrate may be such that the solvent volatilizes sufficiently. For example, the heating conditions may be 40°C to 120°C for 0.1 minutes to 10 minutes.

[0087] The adhesive film of this embodiment may have some of the solvent remaining without being removed. The solvent content in the adhesive film of this embodiment may be, for example, 10% by mass or less, or 5% by mass or less, based on the total mass of the adhesive film.

[0088] <Connection structure and method for manufacturing the same> Next, the connection structure and method for manufacturing the same will be described.

[0089] The connection structure of this embodiment comprises a first circuit member having a first electrode, a second circuit member having a second electrode, and a connecting 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 connecting portion includes a cured product of the adhesive film of this embodiment.

[0090] The manufacturing method of the connecting structure of this embodiment comprises the steps of electrically connecting the first electrode and the second electrode by interposing the adhesive film of this embodiment between the first circuit member and the second circuit member, and heat-pressing the first circuit member and the second circuit member together.

[0091] The above process may include a lamination step of attaching a substrate-attached adhesive film to a first circuit member such that the adhesive film is in contact with the first circuit member; a peeling step of peeling the substrate from the substrate-attached adhesive film attached to the first circuit member; and a heating and pressing step of placing a second circuit member on the first circuit member to which the adhesive film has been laminated so that the first electrode and the second electrode face each other, and then heat-pressing the first circuit member and the second circuit member together.

[0092] Figure 1 is a schematic cross-sectional view showing one embodiment of a connection structure. As shown in the figure, the connection structure 1 comprises a first circuit member 4 having a first electrode 42, a second circuit member 5 having a second electrode 52, and a connection portion 6 disposed between the first circuit member 4 and the second circuit member 5, which electrically connects the first electrode 42 and the second electrode 52 to each other. The first circuit member 4 and the second circuit member 5 are arranged such that the first electrode 42 and the second electrode 52 face each other.

[0093] The first circuit member 4 comprises, for example, a first substrate 41 (e.g., a circuit board) and a first electrode 42 (e.g., a circuit electrode) formed on the main surface 41a of the first substrate 41. An insulating layer (not shown) may be formed on the main surface 41a of the first substrate 41.

[0094] The second circuit member 5 comprises, for example, a second substrate 51 (e.g., a circuit board) and a second electrode 52 (e.g., a bump electrode) formed on the main surface 51a of the second substrate 51. An insulating layer (not shown) may also be formed on the main surface 51a of the second substrate 51.

[0095] The first circuit member 4 and the second circuit member 5 are not particularly limited as long as they are members on which electrodes requiring electrical connection are formed. The first substrate and the second substrate can be inorganic substrates such as semiconductors, glass, or ceramics; polyimide substrates represented by TCP, FPC, COF, etc.; substrates on which electrodes are formed on films such as polycarbonate, polyester, or polyethersulfone; printed wiring boards, etc., and combinations of multiple of these can also be used.

[0096] The first electrode and the second electrode may be made of gold, silver, tin, ruthenium, rhodium, palladium, osmium, iridium, platinum, copper, aluminum, molybdenum, titanium, indium tin oxide (ITO), indium zinc oxide (IZO), indium gallium zinc oxide (IGZO), etc. The first electrode and the second electrode may be circuit electrodes or bump electrodes. At least one of the first electrode and the second electrode may be a bump electrode.

[0097] The first circuit member and the second circuit member may be the same or different from each other. The first circuit member and the second circuit member may be a glass substrate or plastic substrate, a printed circuit board, a ceramic circuit board, a flexible circuit board, a semiconductor silicon IC chip, etc., on which the electrodes described above are formed.

[0098] The connecting portion 6 is a part formed by curing the adhesive film 12 and contains the cured adhesive film 12. The connecting portion 6 contains, for example, conductive particles P and an insulating substance (cured adhesive film) 7 formed by curing components other than the conductive particles (adhesive components, etc.) in the adhesive film 12. The connecting portion 6 spreads in layers along the main surface 41a of the first circuit member 4 and the main surface 51a of the second circuit member 5.

[0099] The conductive particles P are positioned between the first electrode 42 and the second electrode 52. These conductive particles P are in contact with the first electrode 42 and the second electrode 52 in a state that is slightly flattened by compression. This enables an electrical connection between the first electrode 42 and the second electrode 52. The conductive particles P may be positioned not only between the opposing first electrode 42 and the second electrode 52, but also between the main surface 41a of the first substrate 41 and the main surface 51a of the second substrate 51.

[0100] The manufacturing method for the connecting structure 1 includes, for example, the step of heat-pressing a first circuit member 4 and a second circuit member 5 with an adhesive film 12 interposed between the first circuit member 4 and the second circuit member 5, and electrically connecting the first electrode 42 and the second electrode 52 to each other. The manufacturing method for the connecting structure 1 will be described below with reference to Figure 2.

[0101] Figure 2 is a schematic cross-sectional view showing the manufacturing process of the connecting structure 1. In the example shown in the figure, first, a first circuit member 4 and a substrate-attached adhesive film 11 comprising a substrate 13 and an adhesive film 12 are prepared (see Figure 2(a)). The substrate 13 is provided on one main surface of the adhesive film 12.

[0102] Next, the adhesive film 11 with the base material is placed on the main surface 41a of the first circuit member 4. The laminate is placed on the first circuit member 4 with the adhesive film 12 side of the adhesive film 11 facing the first circuit member 4.

[0103] Next, the adhesive film 11 with the substrate is pressed in the directions of arrows A and B in Figure 2(a) to temporarily connect the adhesive film 12 to the first circuit member 4 (see Figure 2(b)). At this time, heating may be performed along with pressing using a thermocompression device.

[0104] Lamination conditions may be set appropriately depending on the type of laminator used. The lamination temperature (pressure temperature) may be, for example, 50 to 90°C. The lamination pressure (pressure pressure) may be, for example, 0.5 to 1.5 MPa. The lamination time (pressure time) may be, for example, 0.5 to 1.5 seconds.

[0105] After temporary connection, the substrate 13 is peeled off the adhesive film 12. In the adhesive film 12 of this embodiment, if the polymerizable compound contains component (b2), the adhesive film 12 has appropriate tackiness, and the substrate 13 can be peeled off without leaving any adhesive residue.

[0106] In the peeling process, the substrate 13 is peeled off from the adhesive film 11 attached to the first circuit member 4. In this way, a laminate is obtained in which the adhesive film 12 is provided on the first circuit member 4.

[0107] Next, as shown in Figure 2(c), the second circuit member 5 is further placed on the adhesive film 12 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 positioned facing each other).

[0108] At this time, the first electrode 42 and the second electrode 52 are aligned so that they face each other, and then the second circuit member 5 can be temporarily fixed by heating and pressing from above. This prevents problems such as the circuit member shifting position or falling during transport. It also suppresses misalignment of the electrodes during the subsequent permanent connection. The heating temperature during temporary fixing should be lower than the temperature at which the adhesive film 12 does not harden, and the time from alignment to completion of temporary fixing may be 5 seconds or less to shorten the throughput.

[0109] Then, while heating the adhesive film 12, pressure is applied in the directions of arrows A and B in Figure 2(c). This hardens the adhesive film 12, and the connection is made. As a result, a connection structure 1 as shown in Figure 1 is obtained. The adhesive film of this embodiment can bond members together more firmly. In addition, if the adhesive film contains component (C), the connection resistance when connecting circuit members can be sufficiently reduced.

[0110] The heating temperature of the adhesive film 12 is preferably above the temperature at which polymerization-active species are generated in the curing agent and polymerization of monomers (polymerizable compounds) begins. This heating temperature may be, for example, 80°C to 200°C, 100°C to 180°C, or 90°C to 170°C. The heating time may be, for example, 0.1 seconds to 30 seconds, 1 second to 20 seconds, 10 seconds or less, or 5 seconds or less.

[0111] In the heating and pressing process, the second circuit member 5 is placed on the first circuit member 4, which is laminated with an adhesive film 12, so that the first electrode 42 on the first substrate 41 and the second electrode 52 on the second substrate 51 face each other. While heating the first circuit member 4, the adhesive film 12, and the second circuit member 5, the first circuit member 4 and the second circuit member 5 are pressed together in the thickness direction (in the direction of the arrow shown in Figure 2(c)) by applying pressure to them, thereby thermally bonding the first circuit member 4 and the second circuit member 5 to each other.

[0112] The heating temperature during heat bonding can be set as appropriate, but for example, it may be 150 to 200°C. The pressure applied during heat bonding is not particularly limited as long as it does not damage the adherend, but for example, the area-equivalent pressure at the bump electrode may be 0.1 to 50 MPa, 40 MPa or less, or 0.1 to 40 MPa. The heating and pressurizing times may be in the range of 0.5 to 120 seconds.

[0113] Although Figures 1 and 2 show a single-layer adhesive film, the adhesive film of this embodiment is not limited to these embodiments. For example, it may include a conductive adhesive layer made of an adhesive film containing conductive particles and a non-conductive adhesive layer made of an adhesive film not containing conductive particles. Using an adhesive film having multiple such adhesive layers for connecting circuit members makes it easier to obtain a stable connection resistance. Examples of the components constituting the conductive adhesive layer and the non-conductive adhesive layer include the components constituting the adhesive film of this embodiment described above.

[0114] The thickness of the conductive adhesive layer may be, for example, 30.0 μm or less, and may also be 20.0 μm or less, 15.0 μm or less, 10.0 μm or less, 8.0 μm or less, 5.0 μm or less, 4.5 μm or less, 4.0 μm or less, 3.5 μm or less, 3.0 μm or less, or 2.5 μm or less. By making the thickness of the conductive adhesive layer 30.0 μm or less, the amount of resin between opposing circuits is reduced, which can suppress an increase in the connection resistance between opposing circuits. This tendency is more pronounced when the thickness of the conductive adhesive layer is 5.0 μm or less. The thickness of the conductive adhesive layer may be, for example, 0.1 μm or more or 0.7 μm or more. Furthermore, if a portion of the conductive particles is exposed from the surface of the conductive adhesive layer (for example, protruding toward the non-conductive adhesive layer), the thickness of the conductive adhesive layer is the distance from the side of the conductive adhesive layer opposite to the non-conductive adhesive layer to the boundary between the conductive adhesive layer and the non-conductive adhesive layer located in the spaced portion between adjacent conductive particles, and the exposed portion of the conductive particles is not included in the thickness of the conductive adhesive layer. The length of the exposed portion of the conductive particles may be, for example, 0.1 μm or more and 5.0 μm or less.

[0115] The thickness of the conductive adhesive layer can be measured, for example, by sandwiching an adhesive film between two pieces of glass (thickness: approximately 1 mm), casting a resin composition consisting of 100 g of bisphenol A type epoxy resin (product name: JER811, manufactured by Mitsubishi Chemical Corporation) and 10 g of a hardener (product name: Epomount hardener, manufactured by Refinetech Co., Ltd.), then performing cross-sectional polishing using a polishing machine, and measuring the thickness using a scanning electron microscope (SEM, product name: SE-8020, manufactured by Hitachi High-Tech Science Corporation). This operation may be repeated multiple times, and the average value may be used as the thickness of the conductive adhesive layer.

[0116] The thickness of the conductive adhesive layer may be 0.1 times or more, 0.2 times or more, or 0.3 times or more of the average particle size of the conductive particles, from the viewpoint of making it easier for conductive particles to be trapped between electrodes and further reducing connection resistance. The thickness of the conductive adhesive layer may be 1.0 times or less, 0.8 times or less, or 0.7 times or less of the average particle size of the conductive particles, from the viewpoint of making it easier for conductive particles to be crushed when they are sandwiched between opposing electrodes during heat compression bonding and further reducing connection resistance. From these viewpoints, the thickness of the conductive adhesive layer may be 0.1 to 0.7 times, 0.2 to 0.8 times, 0.2 to 0.7 times, or 0.3 to 0.7 times the average particle size of the conductive particles. Note that the thickness of the conductive adhesive layer refers to the thickness of the adhesive film located in the spaced portion between adjacent conductive particles.

[0117] The thickness of the non-conductive adhesive layer may be set appropriately according to the height of the electrodes of the circuit components to be bonded, for example, it may be 5 to 200 μm. From the viewpoint of sufficiently filling the space between electrodes and sealing the electrodes, and obtaining better connection reliability, the thickness of the non-conductive adhesive layer may be 5.0 μm or more or 7.0 μm or more, and may be 30.0 μm or less, 20.0 μm or less, 15.0 μm or less, or 13.0 μm or less. In the case where a part of the conductive particles is exposed from the surface of the conductive adhesive layer (for example, protruding toward the non-conductive adhesive layer), the thickness of the non-conductive adhesive layer is the distance from the surface of the non-conductive adhesive layer opposite to the conductive adhesive layer to the boundary between the conductive adhesive layer and the non-conductive adhesive layer located in the separated portion of adjacent conductive particles.

[0118] The thickness of the non-conductive adhesive layer can be determined, for example, in the same manner as the method for measuring the thickness of the conductive adhesive layer described above.

[0119] The sum of the thickness of the conductive adhesive layer and the non-conductive adhesive layer constituting the adhesive film may be, for example, 5 μm or more and 230 μm or less.

[0120] The adhesive film is not limited to the embodiments described above. For example, the adhesive film may be a three-layer film consisting of an adhesive layer containing conductive particles and adhesive layers without conductive particles provided on both sides thereof.

[0121] The present disclosure will be described in more detail below with reference to examples. However, the present disclosure is not limited to these examples.

[0122] The following materials were prepared.

[0123] <Synthesis of Polyester Urethane Resin> In a stainless steel autoclave equipped with a heater, a stirrer, thermometer, condenser, vacuum generator, and nitrogen gas inlet tube, 48 parts by mass of isophthalic acid and 37 parts by mass of neopentyl glycol were added, and then 0.02 parts by mass of tetrabutoxytitanate as a catalyst was added. Next, the temperature was raised to 220°C under a nitrogen stream and stirred for 8 hours. After that, the pressure was reduced to atmospheric pressure (760 mmHg) and cooled to room temperature. This caused a white precipitate to form. Next, the white precipitate was removed, washed with water, and then vacuum dried to obtain a polyester polyol. After the obtained polyester polyol was thoroughly dried, it was dissolved in MEK (methyl ethyl ketone) and placed in a four-necked flask equipped with a stirrer, dropping funnel, reflux condenser, and nitrogen gas inlet tube. Furthermore, as a catalyst, dibutyltin dilaurate was added in an amount of 0.05 parts by mass per 100 parts by mass of polyester polyol, and 4,4'-diphenylmethane diisocyanate in an amount of 50 parts by mass per 100 parts by mass of polyester polyol was dissolved in MEK and added using a dropping funnel. The mixture was stirred at 80°C for 4 hours to obtain the target polyester urethane resin. The weight-average molecular weight of the polyester urethane resin was 25,000. The weight-average molecular weight was measured using a calibration curve with standard polystyrene by gel permeation chromatography (GPC) according to the following conditions. (Measurement conditions) Equipment used: GPC-8020 manufactured by Tosoh Corporation Detector: RI-8020 manufactured by Tosoh Corporation Column: Gelpack GLA160S + GLA150S manufactured by Resonaq Corporation Sample concentration: 120 mg / 3 mL Solvent: Tetrahydrofuran Injection volume: 60 μL Pressure: 2.94 × 10⁻⁶ ６ Pa (30kgf / cm ２ ) Flow rate: 1.00mL / min

[0124] <Synthesis of Polyurethane Acrylate (UA1)> In a reaction vessel equipped with a stirrer, thermometer, reflux condenser with calcium chloride drying tube, and nitrogen gas inlet tube, 2500 parts by mass (2.50 mol) of poly(1,6-hexanediol carbonate) (trade name: Duranol T5652, manufactured by Asahi Kasei Chemicals Corporation, number average molecular weight 1000) and 666 parts by mass (3.00 mol) of isophorone diisocyanate (manufactured by Sigma-Aldrich) were uniformly added dropwise over 3 hours. Then, after sufficiently introducing nitrogen gas into the reaction vessel, the reaction was carried out by heating the inside of the reaction vessel to 70-75°C. Next, 0.53 parts by mass (4.3 mmol) of hydroquinone monomethyl ether (Sigma-Aldrich) and 5.53 parts by mass (8.8 mmol) of dibutyltin dilaurate (Sigma-Aldrich) were added to the reaction vessel. Then, 238 parts by mass (2.05 mol) of 2-hydroxyethyl acrylate (Sigma-Aldrich) were added, and the reaction was carried out at 70°C for 6 hours under an air atmosphere. This yielded polyurethane acrylate (UA1). The weight-average molecular weight of polyurethane acrylate (UA1) was 15,000. The weight-average molecular weight was measured using a calibration curve with standard polystyrene by gel permeation chromatography (GPC) according to the above conditions.

[0125] <Preparation of conductive particles (F1)> A layer made of nickel with a layer thickness of 0.2 μm was formed on the surface of polystyrene particles to obtain conductive particles with an average particle size of 3 μm, a maximum particle size of 3.5 μm, and a specific gravity of 2.5.

[0126] [Thermoplastic Resin] A1: Polyester urethane resin synthesized as described above. A2: A 40% by mass solution prepared by dissolving 40 g of bisphenol A type phenoxy resin (trade name: PKHC, manufactured by Union Carbide) in 60 g of methyl ethyl ketone (the amounts in the table indicate the amount of bisphenol A type phenoxy resin).

[0127] [Polymerizable Compounds] B1: Bismaleimide compound containing an indan ring (bismaleimide compound represented by formula (3) above, Mn: approximately 1000, Mw: approximately 2100) B2: Bismaleimide compound not containing an indan ring (trade name: BMI-2300, manufactured by Yamato Chemical Industries, Ltd.) B3: Polyurethane acrylate (UA1) synthesized as described above B4: Diacrylate having a tricyclodecane skeleton (dicyclopentadiene type diacrylate) (trade name: DCP-A, manufactured by Kyoeisha Chemical Co., Ltd.) B5: 2-methacryloyloxyethyl acid phosphate (trade name: Light Ester P-2M, manufactured by Kyoeisha Chemical Co., Ltd.)

[0128] [Polymerization initiator] C1: Benzoyl peroxide (Trade name: Niper BMT-K40, manufactured by NOF Corporation)

[0129] [Filler] D1: Silica microparticles (product name: R104, manufactured by Nippon Aerosil Co., Ltd., average particle size (primary particle size): 12 nm)

[0130] [Coupling agent] E1: 3-Methacryloxypropyltrimethoxysilane (silane coupling agent, trade name: KBM503, manufactured by Shin-Etsu Chemical Co., Ltd.)

[0131] [Conductive Particles] F1: Conductive particles (F1) prepared as described above.

[0132] <Preparation of Adhesive Films with Substrates> (Examples 1-3 and Comparative Examples 1 and 2) A varnish composition was prepared by mixing the thermoplastic resin, polymerizable compound, polymerization initiator, filler, and coupling agent in the amounts (parts by mass) shown in Table 1 with conductive particles in the amounts (volume %) shown in Table 1. The content (volume %) of conductive particles listed in Table 1 is the content based on the total volume of the varnish composition.

[0133] The prepared varnish composition was applied to a substrate (PET film) with a thickness of 50 μm using a coating apparatus. Next, it was dried with hot air at 70°C for 3 minutes to form an adhesive layer (adhesive film) on the substrate, and an adhesive film with a substrate attached was produced. The thickness of the adhesive layer (thickness after drying) was 14 μm.

[0134]

[0135] [Evaluation of Adhesion Strength] A glass substrate with SiN (silicon nitride) (thickness: 0.5 mm) was prepared as the first circuit component, and an FPC (Flat Printed Circuit) with a pitch of 200 μm (manufactured by Taiyo Technorex Co., Ltd.) was prepared as the second circuit component.

[0136] The prepared adhesive film with a substrate was cut to a width of 1.0 mm, and the adhesive film with a substrate was placed on the first circuit member so that it was in contact with the first circuit member. Using a thermal bonding device (LD-06, manufactured by Ohashi Seisakusho Co., Ltd.) consisting of a ceramic heater stage and a tool (8 mm x 50 mm), the adhesive film with a substrate was attached to the first circuit member by heating and pressurizing at 70°C and 1 MPa for 1 second, and the substrate on the side of the adhesive film with a substrate that was opposite the first circuit member was peeled off. Next, the second circuit was positioned opposite to the first circuit member, and then the connection structure was obtained by heating and pressurizing at 170°C and 4 MPa for 7 seconds using a thermal bonding device (heating method: constant heat type, manufactured by Shibaura Mechatronics Co., Ltd.).

[0137] The adhesive strength (unit: N / m) of the fabricated connecting structures was measured immediately after connection using the 90-degree peel method in accordance with JIS-Z0237. For the connecting structures in the examples, the adhesive strength was also measured using the same method after storage for 32 hours in an environment of 110°C and 85% RH (32 hours after connection). A Tensilon UTM-4 (peel rate: 50 mm / min, manufactured by Toyo Baldwin Co., Ltd.) was used as the adhesive strength measuring device. The results are shown in Table 2.

[0138] <Fabrication of the connecting structure> An FPC (manufactured by Taiyo Technorex Co., Ltd.) with a pitch of 200 μm and a glass substrate with a thin-film electrode (height: 250 nm) made of titanium-aluminum on a glass substrate (manufactured by Inabata Sangyo Co., Ltd.) were connected over a width of 1.65 cm (ACF width: 1.0 mm) using a thermocompression bonding device (heating method: constant heat type, manufactured by Shibaura Mechatronics Co., Ltd.) by heating and pressing at 170°C, 6 MPa, and 7 seconds. This resulted in a connecting structure (circuit connecting structure) in which the FPC and the glass substrate with the thin-film electrode were connected by the cured adhesive film.

[0139] [Evaluation of Connection Resistance] The connection resistance of the obtained connection structures was evaluated immediately after connection using the following method. The connection resistance between opposing electrodes in the connection structure was measured using a multimeter. The connection resistance value was determined as the average value of 16 resistance points between opposing electrodes. In addition, for the connection structures of the examples, the connection resistance after being stored for 12 hours after connection in an environment of 110°C and 85% RH (12 hours after connection) was evaluated using the same method. The results are shown in Table 2.

[0140]

[0141] The adhesive films of Examples 1 to 3 were able to bond components more firmly, and also exhibited sufficiently low connection resistance and excellent connection reliability. Furthermore, the adhesive films of Examples 1 and 2 maintained sufficiently low connection resistance even after high temperature and high humidity tests, demonstrating excellent durability of adhesive strength.

[0142] Reference Examples 1 and 2 were prepared in the same manner as the Examples and Comparative Examples, except that the types and amounts (parts by mass) of the components used were changed as shown in Table 3 below.

[0143]

[0144] <Evaluation of Tackiness (Adhesive Residue)> The tackiness of the substrate-attached adhesive films of Examples 1-3, Comparative Example 1, and Reference Examples 1 and 2 was evaluated using the following procedure. First, a measuring film with a width of 2.5 mm and a length of 40 mm was cut from each substrate-attached adhesive film. The adhesive layer of the measuring film was pressed onto CrIZO coated glass (a base glass with a thickness of 0.5 mm, coated with a metal layer consisting of an outermost layer of IZO (thickness 100 nm), a second layer of Cr (thickness 50 nm), and a third layer of AlNd (thickness 200 nm) on the outermost layer of IZO (thickness 100 nm), a second layer of Cr (thickness 50 nm), and a third layer of AlNd (thickness 200 nm)) using a transfer device (product name LD-06, manufactured by Ohashi Seisakusho Co., Ltd.) and a temporary pressing tool equipped with a cushioning material (product name TC-20A, manufactured by Shin-Etsu Chemical Co., Ltd.) at 70°C, 1 MPa, and 1 second.

[0145] Next, on a hot plate heated to 45°C, the edges of the substrate of the measurement film, which had been pressed onto the glass, were attached to a tensile testing machine (manufactured by Toyo Baldwin Co., Ltd., model number: Tensilon UTM-4). The substrate was then pulled upward at a speed of 50 mm / min perpendicular to the glass surface to separate it from the adhesive layer. After that, the presence or absence of adhesive residue in the separated portion of the substrate was visually observed. The results are shown in Table 4.

[0146] <Glass Adhesion Evaluation> The glass adhesion strength of the substrate-attached adhesive films of Examples 1-3, Comparative Example 1, and Reference Examples 1 and 2 was evaluated. First, a measurement film with a width of 2.5 mm and a length of 40 mm was cut from each substrate-attached adhesive film. The adhesive layer of the measurement film was pressed onto CrIZO coated glass (a base glass with a thickness of 0.5 mm, coated with a metal layer consisting of an outermost layer of IZO (thickness 100 nm), a second layer of Cr (thickness 50 nm), and a third layer of AlNd (thickness 200 nm) on the outermost layer of IZO (thickness 100 nm), a second layer of Cr (thickness 50 nm), and a third layer of AlNd (thickness 200 nm)) using a transfer device (product name LD-06, manufactured by Ohashi Seisakusho Co., Ltd.) and a temporary pressing tool equipped with a cushioning material (product name TC-20A, manufactured by Shin-Etsu Chemical Co., Ltd.) at 70°C, 1 MPa, and 1 second.

[0147] Subsequently, the substrate was peeled off the attached adhesive film, and a 2.3 mm wide tape was fixed to the adhesive layer to obtain a sample for measuring glass adhesion strength. In Comparative Example 1 and Reference Example 2, the adhesive film with substrate had too much tack, making it impossible to properly peel off the substrate, and therefore a sample for measuring glass adhesion strength could not be obtained.

[0148] Next, on a hot plate heated to 45°C, the end of the tape on the measurement film, which was pressed onto the glass, was attached to a tensile testing machine (manufactured by Toyo Baldwin Co., Ltd., model number: Tensilon UTM-4). The tape was pulled up perpendicular to the glass surface at a speed of 50 mm / min to peel the adhesive layer with the tape from the glass, and the adhesion force (mN / cm) between the adhesive layer and the glass was measured. The results are shown in Table 4.

[0149]

[0150] The adhesive films of Examples 1 to 3 had sufficient adhesion to the substrate while also possessing a moderate tackiness that did not impair workability.

[0151] 1...connecting structure, 4...first circuit member, 5...second circuit member, 6...connecting part, 7...insulating material, 41...first substrate, 41a...main surface of the first substrate, 42...first electrode, 51...second substrate, 51a...main surface of the second substrate, 52...second electrode, 11...adhesive film with substrate, 12...adhesive film, 13...substrate, P...conductive particles.

Claims

1. An adhesive film containing a thermoplastic resin and a polymerizable compound, wherein the polymerizable compound contains a bismaleimide compound containing an indan ring.

2. The adhesive film according to claim 1, wherein the bismaleimide compound has a structure represented by the following formula (3). [R in equation (3)] １ and R ６ Each independently represents an alkyl group having 1 to 10 carbon atoms, an alkyloxy group having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, an arylthio group having 6 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a halogen atom, a hydroxyl group, or a mercapto group, R ２ , R ３ and R ４ Each of these independently represents an alkyl group having 1 to 10 carbon atoms, R ５ and R ７ Each of the following independently represents an alkyl group having 1 to 10 carbon atoms, an alkyloxy group having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, an arylthio group having 6 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a halogen atom, a nitro group, a hydroxyl group, or a mercapto group; X and Y independently represent a single bond, an alkylene group having 1 to 5 carbon atoms, or an alkylidene group having 2 to 5 carbon atoms; n1 represents an integer from 0 to 3; n2 to n4 each independently represent an integer from 0 to 4; and m represents a number from 0.95 to 10.

0.

3. The adhesive film according to claim 1 or 2, further containing conductive particles.

4. The adhesive film according to claim 1 or 2, wherein the polymerizable compound further comprises urethane (meth)acrylate.

5. The adhesive film according to claim 4, wherein the ratio of the content of the bismaleimide compound to the content of the urethane (meth)acrylate is 0.05 to 1.5 by mass.

6. A connecting structure comprising: a first circuit member having a first electrode; a second circuit member having a second electrode; and a connecting 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 connecting portion includes a cured product of the adhesive film described in claim 1 or 2.

7. A method for manufacturing a connection structure, comprising the steps of interposing an adhesive film according to claim 1 or 2 between a first circuit member having a first electrode and a second circuit member having a second electrode, and then heat-pressing the first circuit member and the second circuit member to electrically connect the first electrode and the second electrode to each other.

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