Film-like adhesive composition, adhesive film, connecting structure, and method for manufacturing the same

Abstract

To provide a film-like adhesive composition and adhesive film that can stably exhibit connection performance, as well as a connection structure and a method for manufacturing the same that exhibit excellent connection reliability under high temperature and high humidity conditions. [Solution] The film-like adhesive composition contains a thermoplastic resin, a radical polymerizable compound, and conductive particles, wherein the conductive particles comprise a core and a nickel-containing conductive layer provided on the surface of the core, and the conductive layer contains a nickel-tin alloy.

Description

[Technical Field]

[0001] The present invention relates to a film-like adhesive composition, an adhesive film, a connecting structure, and a method for producing the same. [Background technology]

[0002] In recent years, various adhesives have been used in fields such as semiconductors and liquid crystal displays to fix electronic components or connect circuits. In these applications, increasing density and resolution are driving the demand for adhesives with high adhesion and reliability. As a circuit connection material, anisotropic conductive adhesives containing conductive particles are used in 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). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2004-263122 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Anisotropic conductive adhesives are often supplied in film form for ease of processing. Such anisotropic conductive film adhesives are required to stably exhibit connection performance that sufficiently reduces the connection resistance between opposing electrodes when connecting circuit components. Furthermore, the resulting connection structure must not exhibit a significant increase in connection resistance during reliability tests under high temperature and high humidity conditions.

[0005] The present invention aims to provide a film-like adhesive composition and adhesive film that can stably exhibit connection performance, as well as a connection structure that exhibits excellent connection reliability under high temperature and high humidity conditions, and a method for manufacturing the same. [Means for solving the problem]

[0006] In other words, this disclosure includes the following aspects: [1] A film-like adhesive composition comprising a thermoplastic resin, a radical polymerizable compound, and conductive particles, wherein the conductive particles comprise a core and a nickel-containing conductive layer provided on the surface of the core, and the conductive layer comprises a nickel-tin alloy. [2] The film-like adhesive composition according to [1], wherein a nickel-tin alloy region and a nickel region are provided in this order from the outer surface of the conductive layer toward the inside. [3] The film-like adhesive composition according to [1] or [2], wherein the core is a resin particle. [4] The film-like adhesive composition according to any one of [1] to [3], wherein the thermoplastic resin comprises at least one resin selected from the group consisting of polyester urethane resin and phenoxy resin. [5] The film-like adhesive composition according to any one of [1] to [4], wherein the radical polymerizable compound comprises a (poly)urethane (meth)acrylate compound. An adhesive film comprising an adhesive layer made of a film-like adhesive composition according to any one of [6] [1] to [5]. An adhesive film comprising a conductive adhesive layer made of a film-like adhesive composition according to any one of [1] to [5], and a non-conductive adhesive layer containing a thermoplastic resin and a radical polymerizable compound. [8] 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 for 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 [6] or "7". [9] A method for manufacturing a connection structure, comprising the steps of interposing an adhesive film according to [6] or [7] 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. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a film-like adhesive composition and adhesive film that can stably exhibit connection performance, as well as a connection structure that exhibits excellent connection reliability under high temperature and high humidity conditions, and a method for manufacturing the same. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic cross-sectional view showing an adhesive film according to one embodiment. [Figure 2] This is a schematic cross-sectional view showing an adhesive film according to another embodiment. [Figure 3] This is a schematic cross-sectional view showing one embodiment of the connecting structure. [Modes for carrying out the invention]

[0009] 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.

[0010] In this specification, numerical ranges indicated using "~" represent a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described stepwise in this specification, the upper or lower limit of one step in the numerical range may be replaced with the upper or lower limit of another step in the numerical range. 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, if multiple substances corresponding to each component are present in the composition.

[0011] <Film-like adhesive composition> The film-like adhesive composition of this embodiment contains a thermoplastic resin, a radical polymerizable compound, and conductive particles. The film-like adhesive composition of this embodiment may further contain components such as a radical polymerization initiator, a filler, and a silane coupling agent, as needed.

[0012] [Conductive particles] The conductive particles contained in the film-like adhesive composition of this embodiment comprise a core and a nickel-containing conductive layer provided on the surface of the core, wherein the conductive layer contains a nickel-tin alloy.

[0013] Examples of the core particles include organic particles such as resin particles, inorganic particles, metal particles, and organic-inorganic hybrid particles. The core particles may be particles having a core-shell structure. The core-shell structure may be a combination of an organic core and an inorganic shell.

[0014] From the viewpoint of improving the flatness of the conductive particles, the core particles may be resin particles formed of a resin. Examples of the resin forming the resin particles include polyolefin resins such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyisobutylene, and polybutadiene; acrylic resins such as polymethyl methacrylate and polymethyl acrylate; polyalkylene terephthalate, polycarbonate, polyamide, phenol formaldehyde resin, melamine formaldehyde resin, benzoguanamine formaldehyde resin, urea formaldehyde resin, phenol resin, melamine resin, benzoguanamine resin, urea resin, epoxy resin, unsaturated polyester resin, saturated polyester resin, polysulfone, polyphenylene oxide, polyacetal, polyimide, polyamideimide, polyether ether ketone, polyether sulfone, and polymers obtained by polymerizing one or more monomers having an ethylenically unsaturated group.

[0015] Examples of monomers having the above-mentioned ethylenically unsaturated group include styrene monomers such as styrene and α-methylstyrene; carboxyl group-containing monomers such as (meth)acrylic acid, maleic acid, and maleic anhydride; alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate; oxygen atom-containing (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, glycerol (meth)acrylate, polyoxyethylene (meth)acrylate, and glycidyl (meth)acrylate; nitrile-containing monomers such as (meth)acrylonitrile; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, and propyl vinyl ether; vinyl acetate and vinyl butyrate. Vinyl esters such as vinyl laurate and vinyl stearate; unsaturated hydrocarbons such as ethylene, propylene, isoprene, and butadiene; halogen-containing monomers such as trifluoromethyl (meth)acrylate, pentafluoroethyl (meth)acrylate, vinyl chloride, vinyl fluoride, and chlorostyrene; tetramethylolmethane tetra(meth)acrylate, tetramethylolmethane tri(meth)acrylate, tetramethylolmethane di(meth)acrylate, trimethylolpropane Polyfunctional (meth)acrylates such as nitrate tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, glycerol tri(meth)acrylate, glycerol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, (poly)tetramethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, etc.Examples of the silane-containing monomers include triallyl (iso) cyanurate, triallyl trimellitate, divinylbenzene, diallyl phthalate, diallyl acrylamide, diallyl ether, γ-(meth)acryloxypropyltrimethoxysilane, trimethoxysilylstyrene, vinyltrimethoxysilane, and the like.;

[0016] The polymer obtained by polymerizing one or more monomers having an ethylenically unsaturated group can be obtained by known methods such as, for example, a method of suspension-polymerizing the above-mentioned monomers in the presence of a radical polymerization initiator, and a method of swelling and polymerizing the above-mentioned monomers together with a radical polymerization initiator using non-crosslinked seed particles.

[0017] When the core is inorganic particles or organic-inorganic hybrid particles, examples of the inorganic substance forming the core include silica and carbon black. When forming the core with silica, for example, a silicon compound having two or more hydrolyzable alkoxysilyl groups can be hydrolyzed to form crosslinked polymer particles, and then firing can be performed as necessary. Examples of the organic-inorganic hybrid particles include organic-inorganic hybrid particles formed from a crosslinked alkoxysilyl polymer and an acrylic resin.

[0018] When the core is metal particles, examples of the metal forming the core include silver, copper, nickel, silicon, gold, and titanium.

[0019] The particle diameter of the core may be 0.1 μm or more, 1 μm or more, 1.5 μm or more, or 2 μm or more, and may be 1000 μm or less, 500 μm or less, 300 μm or less, 50 μm or less, 30 μm or less, 10 μm or less, 5 μm or less, or 3 μm or less. From the viewpoint of improving the connectivity of the microcircuit, it may be 2 - 5 μm or 5 - 10 μm.

[0020] The particle diameter of the core indicates the diameter when the core is spherical, and indicates the maximum diameter when the core is not spherical.

[0021] From the viewpoint of reducing the connection resistance between electrodes, the conductive layer may have an average nickel content of 50% by mass or more, 65% by mass or more, 70% by mass or more, 75% by mass or more, 80% by mass or more, 85% by mass or more, or 90% by mass or more, based on the total amount of the conductive layer, and may be 95% by mass or less, 90% by mass or less, 85% by mass or less, or 80% by mass or less.

[0022] Furthermore, from the viewpoint of making the conductive layer less susceptible to corrosion even under high temperature and high humidity conditions, the average tin content of the conductive layer may be 5% by mass or more, 10% by mass or more, 15% by mass or more, or 20% by mass or more, based on the total amount of the conductive layer, and from the viewpoint of maintaining the hardness of the conductive layer, it may be 50% by mass or less, or 45% by weight or less.

[0023] Methods for measuring the average metal content in a conductive layer include, for example, absorption spectroscopy or spectral analysis. Absorption spectroscopy can utilize flame spectrophotometers and electric furnace spectrophotometers. Spectral analysis can utilize plasma emission spectrometry and plasma ion source mass spectrometry. An ICP emission spectrometer may also be used to measure the average content.

[0024] From the viewpoint of adhesion between the core and the nickel-containing conductive layer, and the reliability of the connection between electrodes, the average tin content in region A, which extends from the inner surface of the nickel-containing conductive layer outward to a thickness of 1 / 10, may be 10% by mass or less, or 9% by mass or less. Alternatively, the average tin content in region A may be 5% by mass or more.

[0025] From the viewpoint of adhesion between the core and the nickel-containing conductive layer, and the reliability of the connection between electrodes, the average tin content in region B, which is half the thickness from the inner surface outward of the nickel-containing conductive layer, may be 12% by mass or more, 20% by mass or more, 40% by mass or less, or 35% by mass or less.

[0026] From the viewpoint of maintaining connection performance even under high temperature and high humidity conditions, the average tin content in region C, which is half the thickness from the outer surface of the nickel-containing conductive layer inward, may be 20% by mass or more, or 25% by mass or more, and may be 48% by mass or less, or 45% by mass or less.

[0027] The conductive particles may be arranged in such an order from the outer surface of the conductive layer inward that regions of nickel-tin alloy and regions of nickel are provided. In this case, the conductive layer may have a multilayer structure in which, for example, a nickel layer provided on the core is the inner layer and a nickel-tin alloy layer provided on the nickel layer is the outermost layer.

[0028] The conductive layer may further contain phosphorus or boron. The conductive layer may also contain other metals besides nickel and tin. Examples of these other metals include gold, silver, copper, platinum, zinc, iron, lead, aluminum, cobalt, indium, palladium, chromium, seaborgium, titanium, antimony, bismuth, thallium, germanium, cadmium, silicon, tungsten, and molybdenum. These metals may be used individually or in combination of two or more. Furthermore, multiple metals may be alloyed.

[0029] Methods for forming a conductive layer on the surface of a core include, for example, physical deposition such as electroless plating, electroplating, vacuum deposition, ion plating, and ion sputtering; coating the surface of the core or other conductive layer with metal powder or a paste containing metal powder and a binder; and methods combining these methods.

[0030] When measuring the average metal content in each region in the thickness direction of a conductive layer, an FE-TEM device may be used.

[0031] Methods for controlling the respective nickel and tin content and average content in each region of the conductive layer include, for example, controlling the pH of the nickel plating solution when forming the conductive layer by electroless nickel plating, adjusting the concentration of a boron-containing reducing agent or a phosphorus-containing reducing agent when forming the conductive layer by electroless nickel plating, adjusting the tin concentration in the nickel plating solution, and adjusting the nickel concentration in the nickel plating solution.

[0032] A method for forming a conductive layer by electroless plating may comprise a catalytic step and an electroless plating step.

[0033] In the catalytic process, a catalyst, which serves as a starting point for forming a plating layer by electroless plating, is formed on the surface of a core (e.g., resin particles). Specifically, for example, resin particles may be added to a solution containing palladium chloride and tin chloride, and then the surface of the resin particles may be activated with an acidic or alkaline solution to precipitate palladium on the surface of the resin particles. Alternatively, resin particles may be added to a solution containing palladium sulfate and aminopyridine, and then the surface of the resin particles may be activated with a solution containing a reducing agent to precipitate palladium on the surface of the resin particles.

[0034] As a reducing agent, a boron-containing reducing agent or a phosphorus-containing reducing agent can be used.

[0035] In the electroless plating process, a nickel plating bath containing a nickel-containing compound, the boron-containing reducing agent or phosphorus-containing reducing agent mentioned above, a complexing agent, and a tin-containing compound is prepared. By immersing resin particles in this nickel plating bath, nickel can be deposited on the surface of the resin particles on which the catalyst has formed, thereby forming a conductive layer containing nickel and tin. Furthermore, by co-depositing tin when depositing nickel, an alloy plating layer containing nickel and tin can be formed.

[0036] Examples of nickel-containing compounds include nickel sulfate and nickel chloride.

[0037] Examples of phosphorus-containing reducing agents include sodium hypophosphite. Examples of boron-containing reducing agents include dimethylamine borane, sodium borohydride, and potassium borohydride.

[0038] Examples of tin-containing compounds include sodium stannate trihydrate, potassium stannate trihydrate, tin(II) sulfate, tin(IV) chloride pentahydrate, and tin(II) chloride dihydrate.

[0039] Examples of complexing agents include monocarboxylic acid complexing agents such as sodium acetate and sodium propionate; dicarboxylic acid complexing agents such as disodium malonate; tricarboxylic acid complexing agents such as disodium succinate; hydroxy acid complexing agents such as lactic acid, DL-malic acid, Rochelle salt, sodium citrate, and sodium gluconate; amino acid complexing agents such as glycine and EDTA; amine complexing agents such as ethylenediamine; organic acid complexing agents such as maleic acid; and salts thereof.

[0040] The total thickness of the conductive layer may be 0.005 μm or more, 0.01 μm or more, or 0.05 μm or more, and may be 1 μm or less, or 0.3 μm or less, or 0.05 μm to 0.3 μm.

[0041] The conductive particles preferably have a core particle size of 2 μm to 5 μm, and the total thickness of the conductive layer is preferably 0.05 μm to 0.3 μm or less. In this case, the film-like adhesive composition can be suitably used in applications where a large current flows.

[0042] The thickness of the conductive layer can be measured, for example, by observing the cross-section of the conductive particles using a transmission electron microscope (TEM).

[0043] The conductive layer may be formed by a single layer or by multiple layers. In addition to the conductive layer containing nickel, the conductive particles may include, as an outermost layer, a gold layer, a nickel layer, a palladium layer, a copper layer, or an alloy layer containing tin and silver.

[0044] Conductive particles may have multiple protrusions on their surface. For example, by arranging multiple core materials on the surface of a core body, the conductive layer can have multiple protrusions on its outer surface. That is, the outer surface of the conductive layer may be raised by the multiple core materials to form protrusions. In this case, the multiple core materials may be embedded within the conductive layer, or the conductive layer may cover the multiple core materials.

[0045] An oxide film is often formed on the surface of electrodes connected by conductive particles. Furthermore, an oxide film is often formed on the surface of the conductive layer of the conductive particles. By using conductive particles with protrusions, the oxide film is effectively removed by the protrusions when the conductive particles are placed between electrodes and then pressed together. As a result, the electrodes and conductive particles can be made to contact more reliably, and the connection resistance between the electrodes can be reduced.

[0046] Methods for forming protrusions with a core material include a method in which a core material is attached to the surface of a core body and then a conductive layer is formed by electroless plating; a method in which a conductive layer is formed on the surface of a core body by electroless plating, then a core material is attached, and then a conductive layer is formed by electroless plating; and a method in which the core material is added during the process of forming a conductive layer on the surface of a core body by electroless plating. Other methods for forming the above protrusions include a method in which a first conductive layer is formed on the surface of a core body, then a core material is placed on the first conductive layer, and then a second conductive layer is formed; and a method in which the core material is added during the process of forming a conductive layer on the surface of a core body.

[0047] The core material can be made from either conductive or non-conductive materials. Examples of conductive materials include metals, metal oxides, conductive nonmetals such as graphite, and conductive polymers. Examples of conductive polymers include polyacetylene. Examples of non-conductive materials include silica, alumina, barium titanate, and zirconia.

[0048] The core material may be in the form of a lump. Examples of the core material include particulate lumps, aggregates of multiple fine particles, and amorphous lumps.

[0049] The average diameter (average particle diameter) of the core material may be 0.001 μm or more or 0.05 μm or more, and may be 0.9 μm or less or 0.2 μm or less.

[0050] The "average diameter (average particle diameter)" of the core material refers to the number-mean diameter (number-mean particle diameter). The average diameter of the core material can be determined by observing 50 arbitrary core material samples using an electron microscope or optical microscope and calculating the average value.

[0051] The number of protrusions per conductive particle can be appropriately set considering the particle size of the conductive particle, for example, it may be three or more, or five or more.

[0052] The average height of the protrusions may be 0.001 μm or more or 0.05 μm or more, and may be 0.9 μm or less or 0.2 μm or less.

[0053] The conductive particles may further comprise an insulating material disposed on the surface of the conductive layer. In this case, even if the conductive particle content is high, the surface of the particles is coated with a resinous material, which suppresses the occurrence of short circuits due to contact between conductive particles and also improves the insulation between adjacent electrode circuits.

[0054] Conductive particles can be used individually or in combination of two or more types.

[0055] 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 are not spherical, such as having protrusions, the particle size of the conductive particles is taken as the diameter of the circle circumscribing the conductive particles in the SEM image.

[0056] 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.

[0057] The content of conductive particles may be in the range of 0.1 to 30 parts by volume per 100 parts by volume of the resin component of the adhesive composition, as this facilitates obtaining stable connection resistance. The content of conductive particles may also be 0.1 to 10 parts by volume, from the viewpoint of preventing short circuits in adjacent circuits due to excessive conductive particles.

[0058] The content of conductive particles may be 0.5 to 60% by mass, 3 to 45% by mass, or 6 to 30% by mass, based on the total mass of the thermoplastic resin, radical polymerizable compound, and radical polymerization initiator in the adhesive composition, in order to easily obtain a stable connection resistance.

[0059] [Thermoplastic resin] Suitable thermoplastic resins include polyvinyl butyral resin, polyvinyl formal resin, polyamide resin, polyester resin, phenolic resin, epoxy resin, phenoxy resin, polystyrene resin, xylene resin, polyurethane resin, and polyester urethane resin. These can be used individually or in combination of two or more.

[0060] The weight-average molecular weight of the thermoplastic resin is 1.0 × 10⁶, from the viewpoint of achieving excellent film-forming properties of the adhesive composition. 4 The above is also acceptable, and from the viewpoint of mixability, 1.0 × 10 4 The above 1.0 × 10 6 It may be less than [amount missing]. The weight-average molecular weight here is measured using a calibration curve with standard polystyrene by gel permeation chromatography (GPC) according to the conditions described in the examples.

[0061] Furthermore, as a thermoplastic resin, it has a Tg (glass transition temperature) of 40°C or higher and a weight-average molecular weight of 1.0 × 10⁻⁶. 4 A hydroxyl group-containing resin (e.g., phenoxy resin) can be used. The hydroxyl group-containing resin may be modified with an epoxy group-containing elastomer.

[0062] Phenoxy resins can be obtained by reacting difunctional phenols with epihalohydrins to a high molecular weight, or by polyaddition reaction between difunctional epoxy resins and difunctional phenols.

[0063] Polyester urethane resin may be used as the thermoplastic resin.

[0064] In this specification, thermoplastic resins having radically polymerizable functional groups are to be blended as the radically polymerizable compounds described above.

[0065] The thermoplastic resin content may be 5% by mass or more, or 30% by mass or more, and may be 80% by mass or less, or 60% by mass or less, based on the total mass of the resin components of the adhesive composition.

[0066] [Radical polymerizable compounds] Radical polymerizable compounds are compounds that have functional groups capable of radical polymerization. Examples of such compounds include vinyl compounds having a vinyl group and (meth)acrylate compounds having a (meth)acryloyl group. Radical polymerizable compounds may be used in monomer or oligomer form, or in combination of monomer and oligomer. Radical polymerizable compounds can be used individually or in combination of two or more.

[0067] From the viewpoint of good reactivity, the radical polymerizable compound is preferably a (meth)acrylate compound. Examples of (meth)acrylate compounds include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, 2-hydroxy-1,3-di(meth)acryloxypropane, 2,2-bis[4-((meth)acryloxymethoxy)phenyl]propane, 2,2-bis[4-((meth)acryloxypolyethoxy)phenyl]propane, dicyclopentenyl(meth)acrylate, tricyclodecanyl(meth)acrylate, tris((meth)acryloyloxyethyl) isocyanurate, (poly)urethane(meth)acrylate, dimethyloltricyclodecane di(meth)acrylate, isocyanurate EO (ethylene oxide) modified diacrylate, and 2-methacryloyloxyethyl acid phosphate.

[0068] The (meth)acrylate compound may be (poly)urethane (meth)acrylate, in order to balance crosslink density and curing shrinkage, further reduce connection resistance, and improve high-temperature and high-humidity connection reliability. The (poly)urethane (meth)acrylate content may be 20% by mass or more, 40% by mass or more, or 60% by mass or more, or 90% by mass or less, or 80% by mass or less, based on the total mass of the radical polymerizable compound.

[0069] Polyurethane (meth)acrylate has a weight-average molecular weight of 1.0 × 10⁻⁶ 4 It may be greater than or equal to 1.0 × 10⁻⁶, and from the viewpoint of mixability, 1.0 × 10⁻⁶ 4 The above 1.0 × 10 6 The following may also apply. The weight-average molecular weight here is measured using a calibration curve with standard polystyrene by gel permeation chromatography (GPC) according to the conditions described in the examples.

[0070] The (meth)acrylate compound may also have at least one substructure selected from the group consisting of a dicyclopentane skeleton, a tricyclodecane skeleton, and a triazine ring. By using such a substructured (meth)acrylate compound as the radical polymerizable compound, the cured product of the adhesive composition will have excellent heat resistance. From the viewpoint of balancing crosslinking density and curing shrinkage and further reducing connection resistance, the (meth)acrylate compound may also be a (meth)acrylate compound having a tricyclodecane skeleton. From the viewpoint of balancing crosslinking density and curing shrinkage, the content of the (meth)acrylate compound having a tricyclodecane skeleton may be 1% by mass or more, 5% by mass or more, or 10% by mass or more, and may be 90% by mass or less, 60% by mass or less, or 30% by mass or less, based on the total mass of the radical polymerizable compound.

[0071] The (meth)acrylate compound may be a compound represented by the following formula (1) (a (meth)acrylate compound having a phosphate ester structure). In this case, the adhesive strength to the surface of inorganic materials (such as metals) is improved, resulting in better adhesion between electrodes (for example, between circuit electrodes). [ka] In formula (1), n ​​represents an integer from 1 to 3, and R represents a hydrogen atom or a methyl group.

[0072] The (meth)acrylate compound represented by formula (1) can be obtained, for example, by reacting phosphoric anhydride with 2-hydroxyethyl (meth)acrylate. Specific examples of the (meth)acrylate compound represented by formula (1) include mono(2-(meth)acryloyloxyethyl) acid phosphate, di(2-(meth)acryloyloxyethyl) acid phosphate, and the like.

[0073] From the viewpoint of easily obtaining the crosslinking density necessary for reducing the connection resistance and improving the connection reliability, the content of the (meth)acrylate compound represented by formula (1) may be 1% by mass or more, or 2% by mass or more, based on the total mass of the radically polymerizable compound, and may be 20% by mass or less, 10% by mass or less, or 5% by mass or less.

[0074] As the radically polymerizable compound other than the (meth)acrylate compound, for example, the compounds described in Patent Document 5 (International Publication No. 2009 / 063827) can be used.

[0075] The radically polymerizable compound may be a polymer such as polyurethane, polystyrene, polyethylene, polyvinyl butyral, polyvinyl formal, polyimide, polyamide, polyester, polyvinyl chloride, polyphenylene oxide, urea resin, melamine resin, phenol resin, xylene resin, epoxy resin, polyisocyanate resin, phenoxy resin, etc. These polymers have at least one radically polymerizable functional group in the molecule.

[0076] When a polymer is used as the radically polymerizable compound, the handleability of the adhesive composition is excellent, and the stress relaxation during curing is excellent. Further, when the polymer has a functional group such as a hydroxyl group, the adhesiveness is also excellent. From this viewpoint, those obtained by modifying each polymer with a radically polymerizable functional group are more preferable.

[0077] The weight average molecular weight of the polymer may be 1.0×10 4 or more, and from the viewpoint of miscibility, it is 1.0×10 4 or more and 1.0×106 The following may also apply. The weight-average molecular weight here is measured using a calibration curve with standard polystyrene by gel permeation chromatography (GPC) according to the conditions described in the examples.

[0078] The film-like adhesive composition of this embodiment may contain, as a radical polymerizable compound, (poly)urethane (meth)acrylate and the compound represented by formula (1) above, from the viewpoint of suppressing the aggregation of the conductive particles described above.

[0079] The content of radical polymerizable compounds may be 5% by mass or more, 20% by mass or more, or 40% by mass or more, or 90% by mass or less, 75% by mass or less, or 60% by mass or less, based on the total mass of the resin components of the adhesive composition (components other than conductive particles and fillers (details described later); the same applies hereinafter), from the viewpoint of reducing connection resistance and making it easier to obtain the crosslink density necessary to improve high temperature and high humidity connection reliability.

[0080] [Radical polymerization initiator] Radical polymerization initiators are compounds that generate free radicals. Examples include peroxide compounds and azo compounds that decompose upon heating to generate free radicals. Radical polymerization initiators are selected appropriately depending on the desired connection temperature, connection time, etc. Radical polymerization initiators can be used individually or in combination of two or more.

[0081] Examples of radical polymerization initiators include diacyl peroxides, peroxydicarbonates, peroxyesters, peroxyketals, dialkyl peroxides, and hydroperoxides.

[0082] Examples of diacyl peroxides include 2,4-dichlorobenzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide, succinic peroxide, benzoyl peroxytoluene, and benzoyl peroxide.

[0083] Examples of peroxydicarbonates include di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, bis(4-t-butylcyclohexyl)peroxydicarbonate, di-2-ethoxymethoxyperoxydicarbonate, di(2-ethylhexylperoxy)dicarbonate, dimethoxybutyl peroxydicarbonate, and di(3-methyl-3-methoxybutylperoxy)dicarbonate.

[0084] Peroxyesters include 1,1,3,3-tetramethylbutyl peroxyneodecanoate, 1-cyclohexyl-1-methylethyl peroxyneodecanoate, t-hexyl peroxyneodecanoate, t-butyl peroxypivalate, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanonate, 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, 1-cyclohexyl-1-methylethyl peroxy-2-ethylhexanonate, t-hexyl peroxy-2-ethylhexanonate, and t-butyl peroxy Examples include c-2-ethylhexanonate, t-butyl peroxyisobutyrate, 1,1-bis(t-butylperoxy)cyclohexane, t-hexylperoxyisopropyl monocarbonate, t-butylperoxy-3,5,5-trimethylhexanonate, t-butylperoxylaurate, 2,5-dimethyl-2,5-di(m-toluylperoxy)hexane, t-butylperoxyisopropyl monocarbonate, t-butylperoxy-2-ethylhexyl monocarbonate, t-hexylperoxybenzoate, and t-butylperoxyacetate.

[0085] Examples of peroxyketals include 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-hexylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-(t-butylperoxy)cyclododecane, and 2,2-bis(t-butylperoxy)decane.

[0086] Examples of dialkylperoxides include α,α'-bis(t-butylperoxy)diisopropylbenzene, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and t-butylcumyl peroxide.

[0087] Examples of hydroperoxides include diisopropylbenzene hydroperoxide and cumene hydroperoxide.

[0088] These radical polymerization initiators may be used in combination with decomposition accelerators, inhibitors, etc. Furthermore, microencapsulating these radical polymerization initiators with polyurethane-based or polyester-based polymers is preferable because it extends their shelf life.

[0089] From the viewpoint of pot life, the content of the radical polymerization initiator may be 0.1% by mass or more, 0.5% by mass or more, or 1% by mass or more, and may be 20% by mass or less, 10% by mass or less, or 5% by mass or less, based on the total mass of the resin components of the adhesive composition.

[0090] [Other ingredients] The adhesive composition may further contain other components in addition to those described above. Examples of other components include coupling agents and fillers. These components may be used individually or in combination of two or more.

[0091] As a coupling agent, a compound having at least one of a vinyl group, an acryloyl group, an amino group, an epoxy group, or an isocyanate group can be used from the viewpoint of improving adhesion.

[0092] Examples of fillers include non-conductive fillers (e.g., non-conductive particles). The filler may be either an inorganic or 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. The maximum diameter of the filler may be less than the minimum particle size of the conductive particles.

[0093] The filler content may be 4 to 60% by volume, 5 to 50% by volume, or 6 to 30% by volume, based on the total volume of the adhesive composition. From the viewpoint of improving connection reliability, the filler content may be 3 to 60% by mass, 4 to 40% by mass, or 5 to 20% by mass, based on the total mass of the thermoplastic resin, radical polymerizable compound, and radical polymerization initiator of the adhesive composition.

[0094] The adhesive composition may further contain other additives such as softeners, accelerators, antioxidants, colorants, flame retardants, thixotropic agents, and polymerization inhibitors. Examples of polymerization inhibitors include hydroquinone and methyl ether hydroquinones.

[0095] The film-like adhesive compositions described above are suitably used as adhesive compositions for circuit connections to connect circuit members having electrodes with the electrodes facing each other, and are particularly suitably used as anisotropic conductive adhesive compositions for connecting circuit members.

[0096] <Adhesive film> The adhesive film of this embodiment comprises an adhesive layer made of the film-like adhesive composition of this embodiment described above.

[0097] Figure 1 is a schematic cross-sectional view showing an adhesive film according to one embodiment. The adhesive film 1A shown in Figure 1 comprises an adhesive layer 2 made of the above-described film-like adhesive composition. The adhesive layer 2 contains adhesive components (components other than conductive particles in the adhesive composition) 3 and conductive particles 4 dispersed in the adhesive components 3. The thickness of the adhesive film 1A may be 10 μm or more and 50 μm or less.

[0098] In other embodiments, the adhesive film may comprise a conductive adhesive layer made of the film-like adhesive composition of the above embodiment, and a non-conductive adhesive layer containing a thermoplastic resin and a radically polymerizable compound. When an adhesive film comprising multiple such adhesive layers is used to connect circuit members, a stable connection resistance is more easily obtained. Figure 2 is a schematic cross-sectional view of an adhesive film according to another embodiment. The adhesive film 1B shown in Figure 2 comprises a conductive adhesive layer 5 and a non-conductive adhesive layer 6 laminated on the conductive adhesive layer 5.

[0099] The conductive adhesive layer 5 is composed of the film-like adhesive composition described above. Specifically, the conductive adhesive layer 5 contains an adhesive component 3 and conductive particles 4 dispersed in the adhesive component 3.

[0100] The non-conductive adhesive layer 6 may further contain a radical polymerization initiator. The thermoplastic resin, radical polymerizable compound, and radical polymerization initiator contained in the non-conductive adhesive layer 6 may be those used in the film-like adhesive composition described above. The non-conductive adhesive layer 6 may further contain the components exemplified as other components in the film-like adhesive composition described above.

[0101] The thicknesses of the conductive adhesive layer 5 and the non-conductive adhesive layer 6 may be set appropriately according to the height of the electrodes of the circuit member to be bonded. The thickness of the conductive adhesive layer 5 may be, for example, 0.5 μm or more and 20 μm or less. The thickness of the non-conductive adhesive layer 6 may be, for example, 5 μm or more and 200 μm or less. The thickness of the adhesive film 1B (the sum of the thickness of the conductive adhesive layer 5 and the thickness of the non-conductive adhesive layer 6) may be, for example, 5 μm or more and 200 μm or less.

[0102] 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.

[0103] The adhesive film described above can be suitably used as a circuit connection adhesive film for connecting circuit members having electrodes in a state where the electrodes are facing each other.

[0104] The adhesive film of this embodiment can be manufactured by the following method. Specifically, first, each component contained in the adhesive layer (for example, adhesive components and conductive particles) is added to a solvent such as an 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.

[0105] 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 may 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 3-roll mill, a ball mill, a bead mill, or a homodisper.

[0106] The base material is not particularly limited as long as it has heat resistance that can withstand the heating conditions when the solvent is evaporated. For example, films formed from 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.

[0107] 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.

[0108] 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.

[0109] <Circuit connection structure and method for manufacturing the same> Next, a circuit connection structure and its manufacturing method will be described.

[0110] 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 contains a cured product of the adhesive composition of this embodiment.

[0111] Figure 3 is a schematic cross-sectional view showing one embodiment of the connection structure. The connection structure 10 shown in Figure 3 comprises a first circuit member 13 having a first substrate 11 and a first electrode (first connection terminal) 12 formed on its main surface 11a, a second circuit member 16 having a second substrate 14 and a second electrode (second connection terminal) 15 formed on its main surface 14a, and a connecting portion 17 interposed between the first circuit member 13 and the second circuit member 16 to bond them together. The second circuit member 16 is positioned opposite the first circuit member 13 such that the second electrode 15 faces the first electrode 12.

[0112] The connecting portion 17 includes a cured adhesive film and is composed of a cured adhesive component 18 and conductive particles 4 dispersed in the cured adhesive component 18. The opposing first electrode 12 and second electrode 15 are electrically connected via the conductive particles 4. On the other hand, the first electrodes 12 and the second electrodes 15 formed on the same substrate are insulated from each other.

[0113] Examples of the first substrate 11 and the second substrate 14 include chip components such as semiconductor chips, resistor chips, and capacitor chips, and substrates such as printed circuit boards. While circuit components typically have numerous connection terminals, the number of connection terminals may be limited to one in some cases. More specifically, substrates made of inorganic materials such as semiconductors, glass, and ceramics, plastic substrates, or glass / epoxy substrates are used. Examples of plastic substrates include polyimide film, polycarbonate film, and polyester film.

[0114] The first electrode 12 and the second electrode 15 are formed from a metal such as copper. To obtain a better electrical connection, it is preferable to form a surface layer containing a metal selected from gold, silver, tin, and platinum group metals on at least one of the first electrode 12 and the second electrode 15. The surface layer may be selected from gold, silver, platinum group metals, or tin, or a combination of these may be used. Alternatively, a multilayer structure may be formed by combining multiple metals, such as copper / nickel / gold.

[0115] One of the first circuit member 13 and the second circuit member 16 may be a liquid crystal display panel having a glass substrate or a plastic substrate as its circuit board and connection terminals formed from ITO or the like. Alternatively, one of the first circuit member 13 and the second circuit member 16 may be a flexible printed circuit board (FPC), tape curia package (TCP), or chip-on-film (COF) having a polyimide film as its circuit board, or a semiconductor silicon chip having a semiconductor substrate as its circuit board. These various circuit members can be combined as needed to form a connection structure.

[0116] Furthermore, it is preferable that the substrate on which the electrodes are provided be preheated before joining with the adhesive composition in order to eliminate the influence of volatile components caused by heating during connection on the connection.

[0117] The method for manufacturing the connection structure according to this embodiment includes the step of interposing the adhesive film of this embodiment 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 together to electrically connect the first electrode and the second electrode to each other.

[0118] Specifically, first, a first circuit member 13 having a first substrate 11 and a first electrode (first connection terminal) 12 formed on its main surface 11a, and a second circuit member 16 having a second substrate 14 and a second electrode (second connection terminal) 15 formed on its main surface 14a are prepared. Then, the first circuit member 13 and the second circuit member 16 are arranged so that the first electrode 12 and the second electrode 15 face each other, and an adhesive film is placed between the first circuit member 13 and the second circuit member 16.

[0119] The adhesive film placed between the first circuit member 13 and the second circuit member 16 may be the adhesive film 1A or 1B described above.

[0120] When using an adhesive film 1B having two adhesive layers, the adhesive film 1B may be arranged such that the conductive adhesive layer 5 side containing conductive particles faces the first circuit member 13 and the non-conductive adhesive layer 6 side not containing conductive particles faces the second circuit member 16, or the adhesive film 1B may be arranged such that the conductive adhesive layer 5 side faces the second circuit member 16 and the non-conductive adhesive layer 6 side faces the first circuit member 13.

[0121] Next, the first circuit member 13, the adhesive film 1A, and the second circuit member 16 are heated, and the first circuit member 13 and the second circuit member 16 are pressed together in the thickness direction, thereby thermally bonding them to each other. The adhesive component of the adhesive film hardens due to the heating, and as a result, the first circuit member 13 and the second circuit member 16 are pressed together via the hardened adhesive film.

[0122] The pressure applied during pressurization is not particularly limited as long as it does not damage the adherend, but generally 0.1 to 10 MPa is preferred. The heating temperature is not particularly limited, but 100 to 200°C is preferred. These pressurization and heating processes are preferably carried out for a period of 0.5 to 100 seconds, and bonding is also possible with heating at 130 to 180°C, 3 MPa, and 10 seconds. [Examples]

[0123] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to these examples.

[0124] <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, followed by 0.02 parts by mass of tetrabutoxytitanate as a catalyst. The mixture was then heated 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. The white precipitate was then removed, washed with water, and vacuum-dried to obtain a polyester polyol. After thoroughly drying the obtained polyester polyol, 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, dibutyltin dilaurate was added as a catalyst 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 Resona Corporation Sample concentration: 120mg / 3mL Solvent: tetrahydrofuran Injection volume: 60μL Pressure: 2.94 × 10 6Pa(30kgf / cm 2 ) Flow rate: 1.00mL / min

[0125] <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.

[0126] <Fabrication of conductive particles (F1)> According to the method described in Example 15 of Japanese Patent Publication No. 2019-024006, conductive particles (F1) were obtained in which a nickel-tin alloy layer (thickness 109 nm) was provided on the surface of organic-inorganic hybrid particles, and composite Ni protrusions were formed on the outer surface of the nickel-tin alloy layer.

[0127] <Preparation of conductive particles (F2)> A layer of nickel with a 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.

[0128] <Preparation of adhesive film (Example 1 and Comparative Example 1)> The following components were mixed in the amounts (parts by mass) shown in Table 1 to prepare varnish compositions (varnish-like adhesive compositions). Conductive particles were also prepared separately by storing them under high temperature and high humidity conditions (85°C, 85% humidity) for 6 hours, and varnish compositions using these particles were also prepared.

[0129] [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).

[0130] [Radical polymerizable compounds] B1: Polyurethane acrylate (UA1) synthesized as described above. B2: Diacrylate with a tricyclodecane skeleton (dicyclopentadiene type diacrylate) (Trade name: DCP-A, manufactured by Kyoeisha Chemical Co., Ltd.) B3: 2-Methacryloyloxyethyl acid phosphate (Product name: Light Ester P-2M, manufactured by Kyoeisha Chemical Co., Ltd.)

[0131] [Radical polymerization initiator] C1: Benzoyl peroxide (Product name: Niper BMT-K40, manufactured by NOF Corporation)

[0132] [Filling material] D1: Silica microparticles (product name: R104, manufactured by Nippon Aerosil Co., Ltd., average particle size (primary particle size): 12 nm)

[0133] [Coupling agent] E1:3-Methacryloxypropyltrimethoxysilane (Trade name: KBM503, manufactured by Shin-Etsu Chemical Co., Ltd.)

[0134] [Conductive particles] F1: Conductive particles (F1) prepared as described above. F2: Conductive particles (F2) prepared as described above.

[0135] [Table 1]

[0136] The above varnish composition was applied to a substrate (PET film) with a thickness of 50 μm using a coating apparatus. Next, hot air drying was performed at 70°C for 3 minutes to form an adhesive layer (film-like adhesive composition) on the substrate, and an adhesive film with a substrate was prepared. The thickness of the adhesive layer (thickness after drying) was 14 μm.

[0137] Two types of adhesive films with a substrate were prepared: Adhesive film A, made using conductive particles treated with high temperature and high humidity, and Adhesive film B, made using untreated conductive particles.

[0138] <Fabrication of connecting structures> A 200 μm pitch FPC (manufactured by Taiyo Technorex Co., Ltd.) and a PI substrate with a thin-film electrode (manufactured by Inabata & Co., Ltd.) equipped with a titanium-aluminum-titanium thin-film electrode (height: 550 nm) on a PI substrate were connected over a width of 1.65 cm (ACF width: 1.4 mm) using a thermocompression bonding device (heating method: constant heat type, manufactured by Taiyo Machinery Co., Ltd.) by heating and pressurizing at 160°C and 6 MPa for 7 seconds. This resulted in a connection structure (circuit connection structure) in which the FPC and the PI substrate with the thin-film electrode were connected by the cured film of the above-mentioned film-like adhesive composition.

[0139] <Evaluation of the connection structure immediately after connection and after high temperature and high humidity testing> The connection resistance of the connection structure was evaluated immediately after connection and after the high-temperature, high-humidity test using the following method. The high-temperature, high-humidity test was performed by leaving the connection structure in a constant temperature and humidity chamber at 110°C and 85%RH for 32 hours.

[0140] [Connection resistance] The connection resistance between opposing electrodes in the connection structure was measured using a multimeter. The connection resistance was calculated as the average value of 16 resistance points between opposing electrodes.

[0141] [evaluation] For both the connection resistance immediately after connection and the connection resistance after high-temperature and high-humidity testing, the percentage increase in connection resistance was calculated using the connection resistance value immediately after connection of the connection structure made with adhesive film B as the baseline.

[0142] [Table 2]

[0143] <Evaluation of the dispersibility of conductive particles> The dispersibility of conductive particles was evaluated as follows: Adhesive film B was prepared in the same manner as in Example 1, except that a varnish composition with the composition shown in Table 3 below was used. A transmission image of a 700 × 900 μm area was captured at a size of 2048 × 1536 pixels using a microscope (Shimadzu Rika Co., Ltd., "Panthera C2"). The number of aggregates in which five or more conductive particles are clustered together in this image was measured.

[0144] [Table 3]

[0145] [Table 4]

[0146] As shown in Table 4, conductive particles F1 tend to have inferior dispersibility in thermoplastic resins compared to conductive particles F2, but it can be seen that dispersibility is improved by using a radical polymerizable compound in combination. [Explanation of Symbols]

[0147] 1A, 1B...Adhesive film, 2...Adhesive layer, 3...Adhesive component, 4...Conductive particles, 5...Conductive adhesive layer, 6...Non-conductive adhesive layer, 10...Connecting structure, 11...First substrate, 12...First electrode, 13...First circuit member, 14...Second substrate, 15...Second electrode, 16...Second circuit member, 17...Connecting part.

Claims

1. It contains a thermoplastic resin, a radical polymerizable compound, and conductive particles. The conductive particle comprises a core and a nickel-containing conductive layer provided on the surface of the core, A film-like adhesive composition in which the conductive layer contains a nickel-tin alloy.

2. The film-like adhesive composition according to claim 1, wherein a nickel-tin alloy region and a nickel region are provided in this order from the outer surface of the conductive layer toward the inside.

3. The film-like adhesive composition according to claim 1, wherein the core is a resin particle.

4. The film-like adhesive composition according to claim 1, wherein the thermoplastic resin comprises at least one resin selected from the group consisting of polyester urethane resins and phenoxy resins.

5. The film-like adhesive composition according to claim 1, wherein the radical polymerizable compound comprises a (poly)urethane (meth)acrylate compound.

6. An adhesive film comprising an adhesive layer made of the film-like adhesive composition according to any one of claims 1 to 5.

7. A conductive adhesive layer comprising a film-like adhesive composition according to any one of claims 1 to 5, A non-conductive adhesive layer containing a thermoplastic resin and a radical polymerizable compound, An adhesive film equipped with [the necessary components].

8. A first circuit member having a first electrode, A second circuit member having a second electrode, It comprises a connecting portion disposed between the first circuit member and the second circuit member, which electrically connects the first electrode and the second electrode to each other, A connecting structure wherein the connecting portion includes a cured product of the adhesive film described in claim 6.

9. A first circuit member having a first electrode, A second circuit member having a second electrode, It comprises a connecting portion disposed between the first circuit member and the second circuit member, which electrically connects the first electrode and the second electrode to each other, A connecting structure wherein the connecting portion includes a cured product of the adhesive film described in claim 7.

10. A method for manufacturing a connection structure, comprising the steps of interposing an adhesive film according to claim 6 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 together to electrically connect the first electrode and the second electrode.

11. A method for manufacturing a connection structure, comprising the steps of interposing an adhesive film according to claim 7 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 together to electrically connect the first electrode and the second electrode.

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