Polymer particles, conductive particles and anisotropic conductive materials

Abstract

To provide a base particle for a conductive particle in a smaller particle size, for producing a conductive particle capable of avoiding aggregation of the base particle for a conductive particle in plating or a pre-treatment thereof, resulting in a lower initial resistance value and a higher connection reliability, and a utilization technique thereof.SOLUTION: A base particle for a conductive particle includes a polymer having a structure derived from a monomer unit expressed by a specific chemical formula (1), and has the structure derived from the formula (1) in a specific ratio. A production method of a base particle for a conductive particle includes: a step of preparing a seed particle; a step of making the seed particle absorb a monomer expressed by the chemical formula (1) and a polymerization initiator; and a step of polymerizing the monomer. A conductive particle has a conductive metallic layer formed on a surface of the base particle for a conductive particle. An anisotropic conductive material includes the conductive particle.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a substrate particle for a conductive particle and its use. [Background technology]

[0002] Conventionally, in the assembly of electronic devices, a connection method using anisotropic conductive materials has been adopted to electrically connect a large number of opposing electrodes or wirings. Anisotropic conductive materials are materials in which conductive particles are mixed with a binder resin or the like. Furthermore, the conductive particles used in anisotropic conductive materials are metal particles or conductive particle substrate particles whose surfaces are coated with a conductive metal layer.

[0003] There are conductive particles in which inorganic fine particles or organic resin fine particles with a uniform particle size are used as base particles for conductive particles, and the surfaces of these base particles are coated with a metal such as nickel by electroless plating (for example, Patent Documents 1 and 2). These conductive particles have the problem that the plating layer can peel off from the base particles for conductive particles or the plating can crack, resulting in a decrease in conductivity when the conductive particles are pressure-bonded to a substrate or electrode terminal. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-64500 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-68143 Summary of the Invention [Problem to be solved by the invention]

[0005] Furthermore, if the particle diameter of the base particles for conductive particles is small, there is a problem that the base particles for conductive particles aggregate when plating the base particles for conductive particles with a conductive metal layer or during pretreatment therefor, and the conductive metal layer is not formed uniformly. In general, in electroless plating, in order to improve the adhesion between the base particles and the plating layer, pretreatment processes such as degreasing of the base particles, etching to form minute irregularities on the surface of the base particles, and catalysis to support a catalyst on the surface of the base particles are carried out prior to electroless plating. In particular, alkaline permanganate treatment solutions are currently widely used in resin etching, so dispersion of resin particles in alkaline aqueous solutions is important for the formation of a uniform conductive metal layer. However, the simple hydrophilic treatments that have been studied so far have still had problems improving dispersibility in alkaline solutions.

[0006] An object of one aspect of the present invention is to provide a base particle for conductive particles having a small particle size, which prevents the base particle for conductive particles from agglomerating during plating and pretreatment, thereby producing conductive particles with low initial resistance and high connection reliability, and a technology for using the same. [Means for solving the problem]

[0007] As a result of intensive research to solve the above-mentioned problems, the present inventors have found that base particles for conductive particles containing a polymer having a structure derived from a monomer unit represented by formula (1) have particularly excellent dispersibility in water and alkaline aqueous solutions compared to other particles, and therefore can prevent particle aggregation during plating and its pretreatment, thereby obtaining conductive particles with low initial resistance and high connection reliability, and have completed the present invention.

[0008] The present invention includes the following configurations. [1] A base particle for a conductive particle, characterized by containing a polymer having a structure derived from a monomer unit represented by formula (1).

[0009] [ka] In the above formula (1), R 1 is hydrogen or an organic group having 1 to 8 carbon atoms, R 2 , R 3are the same or different and are a hydrogen atom, a methyl group, or an ethyl group, X is a methylene group, or a methylene group in which a hydrogen atom is substituted with a methyl group or a halogen. [2] The base particle for conductive particles according to [1], characterized in that the structure derived from the monomer unit represented by formula (1) is 1 to 25 parts by mass relative to 100 parts by mass of the polymer. [3] The base particle for conductive particles according to [1] or [2], characterized in that the polymer is contained in an amount of 90 parts by mass or more per 100 parts by mass of the base particle for conductive particles. [4] The base particle for conductive particles according to any one of [1] to [3], characterized in that the base particle has an alkali dispersibility of 10% or less. [5] The base particle for conductive particles according to any one of [1] to [4], which is a particle containing Si atoms. [6] The base particle for conductive particles according to any one of claims 1 to 5, wherein the content of Si is 1 to 25 parts by mass relative to 100 parts by mass of the polymer. [7] The base particle for conductive particles according to any one of [1] to [6], characterized in that the number average particle diameter is 1.0 to 7.0 μm. [8] A method for producing a base particle for a conductive particle, comprising the steps of preparing a seed particle, allowing the seed particle to absorb a monomer represented by formula (1) and a polymerization initiator, and polymerizing the monomer. [9] The method for producing a base particle for a conductive particle according to [8], wherein the seed particle is a seed particle obtained by condensing an organic silane compound.

[10] Conductive particles, comprising the base particle for conductive particles according to any one of [1] to [7], and at least one conductive metal layer formed on the surface thereof.

[11] An anisotropic conductive material comprising the conductive particles according to

[10] .

[12] An anisotropic conductive paste comprising the conductive particles according to

[10] and a binder resin. [Effects of the Invention]

[0010] According to one aspect of the present invention, aggregation of base particles for conductive particles can be prevented during plating and pretreatment thereof, and as a result, conductive particles having low initial resistance and high connection reliability can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0011] One embodiment of the present invention will be described below, but the present invention is not limited thereto. The present invention is not limited to the respective configurations described below, and various modifications are possible within the scope of the claims. Embodiments and examples obtained by appropriately combining the technical means disclosed in different embodiments and examples are also included in the technical scope of the present invention. Furthermore, all academic literature and patent documents described in this specification are incorporated herein by reference. Furthermore, unless otherwise specified in this specification, "A to B" representing a numerical range means "greater than or equal to A and less than or equal to B."

[0012] [1. Base material particles for conductive particles] A base particle for conductive particles according to one embodiment of the present invention (hereinafter also referred to simply as "base particle for conductive particles" or "base particle") is characterized by containing a polymer having a structural unit derived from a monomer unit represented by formula (1) (the structure of the polymer includes a structure derived from the monomer component of formula (1)).

[0013] [ka] In the above formula (1), R 1 is hydrogen or an organic group having 1 to 8 carbon atoms, R 2 , R 3 are the same or different and are a hydrogen atom, a methyl group, or an ethyl group, X is a methylene group, or a methylene group in which a hydrogen atom is substituted with a methyl group or a halogen.

[0014] In formula (1), R 1is an organic group having 1 to 8 carbon atoms, and the organic group is preferably composed of a hydrocarbon group, which may have an ether group and whose hydrogen atoms may be substituted. The organic group may be linear or branched, and may also have a cyclic structure. Examples of the hydrocarbon group include a chain saturated hydrocarbon group, a chain unsaturated hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group. Of these, a chain saturated hydrocarbon group having 1 to 8 carbon atoms, a chain unsaturated hydrocarbon group having 2 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 8 carbon atoms, and an aromatic hydrocarbon group having 6 to 8 carbon atoms are preferred. Examples of substituents that may substitute for hydrogen atoms in the hydrocarbon group include halogen atoms such as fluorine, chlorine, bromine, and iodine atoms, a cyano group, and a trimethylsilyl group, but the present invention is not limited to these examples.

[0015] Examples of the chain saturated hydrocarbon group include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-amyl, sec-amyl, tert-amyl, neopentyl, n-hexyl, sec-hexyl, n-heptyl, n-octyl, sec-octyl, tert-octyl, and 2-ethylhexyl groups, with methyl and ethyl being particularly preferred. However, the present invention is not limited to these examples.

[0016] Examples of the chain unsaturated hydrocarbon group include a 1-propenyl group, a 2-propenyl group, a 1-methyl-1-propenyl group, a 1-methyl-2-propenyl group, a 2-methyl-1-propenyl group, a 2-methyl-2-propenyl group, a 1-butenyl group, a crotyl group, a 1,1-dimethyl-2-propenyl group, a 2-methyl-butenyl group, a 3-methyl-2-butenyl group, a 3-methyl-3-butenyl group, and a 2-methyl-3-butenyl group, but the present invention is not limited to these examples.

[0017] Examples of the alicyclic hydrocarbon group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclopentylmethyl group, a cyclohexyl group, a cyclohexylmethyl group, and a 4-methylcyclohexyl group, but the present invention is not limited to these examples.

[0018] Examples of the aromatic hydrocarbon group include a phenyl group, a methylphenyl group, a dimethylphenyl group, a benzyl group, and a styryl group, but the present invention is not limited to these examples.

[0019] Examples of hydrocarbon groups having an ether bond include chain ether groups such as a methoxyethyl group, an ethoxyethyl group, a methoxyethoxyethoxyethyl group, a 3-methoxybutyl group, and an ethoxyethoxyethyl group; groups having both an alicyclic hydrocarbon group and a chain ether group, such as a cyclopentoxyethyl group and a cyclohexyloxyethyl group; groups having both an aromatic hydrocarbon group and a chain ether group, such as a phenoxyethyl group; and cyclic ether groups such as a glycidyl group, a β-methylglycidyl group, a β-ethylglycidyl group, a 3,4-epoxycyclohexylmethyl group, a 2-oxetanemethyl group, a 3-methyl-3-oxetanemethyl group, a 3-ethyl-3-oxetanemethyl group, a tetrahydrofurfuryl group, a tetrahydrofuranyl group, a tetrahydropyranyl group, a dioxazolanyl group, and a dioxanyl group, but the present invention is not limited to these examples.

[0020] R 1 is preferably a chain saturated hydrocarbon group having 1 to 6 carbon atoms, more preferably a chain saturated hydrocarbon group having 1 to 4 carbon atoms, even more preferably a chain saturated hydrocarbon group having 1 to 3 carbon atoms, and most preferably a chain saturated hydrocarbon group having 1 or 2 carbon atoms from the viewpoint of the balance between hydrophilicity and hydrophobicity.

[0021] In formula (1), X is preferably a methylene group or a methylene group in which a hydrogen atom is substituted with a methyl group, and more preferably a methylene group.

[0022] R 2 and R 3 is preferably a hydrogen atom. The polymer contained in the base particle for conductive particles according to one embodiment of the present invention preferably contains 1 to 25 parts by mass of a structure derived from the monomer unit represented by the formula (1) above, relative to 100 parts by mass of the polymer.

[0023] If the structure derived from the monomer unit represented by formula (1) is less than 1 part by mass, the dispersibility in water and alkaline aqueous solution will be insufficient, and the plating ability of the base particle will be insufficient, making it difficult to achieve excellent initial resistance and connection reliability. On the other hand, if the structure derived from the monomer unit represented by formula (1) is more than 25 parts by mass, the excessive presence of the structure derived from formula (1) will cause aggregation during the plating process to produce conductive particles, resulting in insufficient alkaline dispersibility, and there is a risk that uniform plating will not be achieved.

[0024] For this reason, the polymer contained in the base particle for the conductive particle preferably contains 1 to 25 parts by mass of the structure derived from the monomer unit represented by formula (1), more preferably 5 to 24 parts by mass, particularly preferably 7 to 23 parts by mass, and most preferably 10 to 20 parts by mass.

[0025] In one embodiment of the present invention, the polymer contained in the base particle for conductive particles may have a structural unit derived from the monomer unit represented by formula (1), and may also have a structural unit derived from a vinyl-based monomer other than the monomer unit represented by formula (1). Furthermore, the polymer contained in the base particle for conductive particles is not limited to a polymer having only a structural unit derived from a vinyl-based monomer, and may also be a polymer further containing a structural unit containing a Si atom, which will be described later.

[0026] Examples of vinyl monomers other than the monomer unit represented by formula (1) include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate; cyclopropyl (meth)acrylate, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, and cyclooctyl (meth)acrylate; cycloalkyl (meth)acrylates such as phenyl (meth)acrylate, cycloundecyl (meth)acrylate, cyclododecyl (meth)acrylate, isobornyl (meth)acrylate, and 4-t-butylcyclohexyl (meth)acrylate; aromatic ring-containing (meth)acrylates such as phenyl (meth)acrylate, benzyl (meth)acrylate, tolyl (meth)acrylate, and phenethyl (meth)acrylate; styrene-based monofunctional monomers such as alkylstyrenes such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, and pt-butylstyrene; and halogen group-containing styrenes such as o-chlorostyrene, m-chlorostyrene, and p-chlorostyrene; and other vinyl-based monofunctional monomers.

[0027] Further, examples of vinyl-based monomers other than the monomer unit represented by formula (1) include allyl (meth)acrylates such as allyl (meth)acrylate; alkanediol di(meth)acrylates such as ethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, and 1,3-butylene di(meth)acrylate; diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, decaethylene glycol di(meth)acrylate, pentadecaethylene glycol di(meth)acrylate, pentadecaethylene glycol di(meth)acrylate, and polyethylene glycol di(meth)acrylate. Examples of suitable crosslinking agents include di(meth)acrylates such as polyalkylene glycol di(meth)acrylates (e.g., polypropylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate), tri(meth)acrylates such as trimethylolpropane tri(meth)acrylate, tetra(meth)acrylates such as pentaerythritol tetra(meth)acrylate, hexa(meth)acrylates such as dipentaerythritol hexa(meth)acrylate, aromatic hydrocarbon crosslinking agents (preferably styrene-based multifunctional monomers such as divinylbenzene) such as divinylbenzene, divinylnaphthalene, and derivatives thereof, and heteroatom-containing crosslinking agents (e.g., N,N-divinylaniline, divinyl ether, divinyl sulfide, divinyl sulfonic acid). The term "vinyl multifunctional monomer" refers to a monomer having two or more vinyl groups in one molecule.

[0028] Furthermore, the vinyl-based polyfunctional monomer other than the monomer represented by formula (1) preferably has a structural unit derived from divinylbenzene, ethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, or 1,6-hexanediol di(meth)acrylate.

[0029] Furthermore, the base particle for a conductive particle according to one embodiment of the present invention may be a particle containing Si atoms, which can achieve high hardness, which is a characteristic of particles containing inorganic substances.

[0030] In this specification, "particles containing Si atoms" refers to particles containing a polymer having both a polysiloxane structure and a structure derived from an organic component monomer. The polysiloxane structure can be obtained, for example, by hydrolysis and condensation of a silane compound. The silane compound preferably includes a silane compound having a vinyl group or a (meth)acryloxy group. The organic component monomer preferably includes the vinyl monomer described above.

[0031] The silane compound having a vinyl group is not particularly limited, but examples thereof include vinyltrimethoxysilane and vinyltriethoxysilane.

[0032] Furthermore, the silane compound having a (meth)acryloxy group is not particularly limited, but examples thereof include γ-(meth)acryloxypropyltrimethoxysilane, γ-(meth)acryloxypropyltriethoxysilane, γ-(meth)acryloxypropyltriacetoxysilane, γ-(meth)acryloxyethoxypropyltrimethoxysilane (also referred to as γ-trimethoxysilylpropyl-β-(meth)acryloxyethyl ether), γ-(meth)acryloxypropylmethyldimethoxysilane, and γ-(meth)acryloxypropylmethyldiethoxysilane.

[0033] The silane compounds may be used in combination of two or more kinds.Other silane compounds are not particularly limited, but examples thereof include tetrafunctional silanes such as tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, and tetraacetoxysilane, trifunctional silanes such as methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, phenyltrimethoxysilane, methyltriacetoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3,4-epoxybutyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-glycidoxypropyltriethoxysilane, and bifunctional silanes such as dimethyldimethoxysilane, dimethyldiethoxysilane, diacetoxydimethylsilane, and diphenyldisilanediol.

[0034] The content of Si atoms in the base particles for conductive particles derived from these silane compounds is preferably 1 to 25 parts by mass relative to 100 parts by mass of the polymer.

[0035] When the proportion of Si atoms in the polymer is within the above range, the particles have effective hardness and mechanical recovery. If the proportion is less than 1 part by mass per 100 parts by mass of the polymer, the hardness characteristic of inorganic materials is not exhibited. If the proportion is more than 25 parts by mass, the mechanical recovery of the organic polymer structure may be impaired or the particles may crack. To achieve more effective hardness and mechanical recovery, the proportion of Si atoms per 100 parts by mass of the polymer is preferably 1 to 25 parts by mass, more preferably 3 to 23 parts by mass, particularly preferably 5 to 20 parts by mass, and most preferably 8 to 18 parts by mass.

[0036] The proportion of Si atoms in the polymer can be determined by measuring the mass of the base particle for conductive particles according to the present invention before and after firing in an oxidizing atmosphere.

[0037] <Measurement of Si content in base particles for conductive particles> The mass equivalent to Si is calculated from the ash mass (referred to as the SiO2 mass) when the conductive particle base material particle is fired at 950°C in an oxidizing atmosphere such as air, and the Si content is calculated by dividing the Si mass by the mass of the conductive particle base material particle subjected to the firing treatment. Note that to calculate the mass equivalent to the Si amount from the ash mass, the ash mass is multiplied by 0.4672 (Si atomic weight / SiO2 formula weight).

[0038] The base particle for conductive particles according to the present invention preferably contains, per 100 parts by mass, 90 parts by mass or more of a polymer containing a structure derived from a monomer unit represented by formula (1). By containing a large amount of the polymer containing a structure derived from a monomer unit represented by formula (1), base particles for conductive particles having excellent connection reliability can be obtained, which is preferable. The content of the polymer is more preferably 95 parts by mass or more, even more preferably 98 parts by mass or more, and particularly preferably 99 parts by mass or more.

[0039] The proportion of the polymer in the base particle for conductive particles according to the present invention can be determined by measuring the mass of the base particle for conductive particles before and after heat treatment in an inert atmosphere.

[0040] <Measurement of the polymer ratio in the base particles for conductive particles> The proportion of polymer in the base particle for conductive particles is determined by dividing the remaining mass after treating the base particle for conductive particles at 105°C for 60 minutes in an inert atmosphere such as nitrogen by the mass of the base particle for conductive particles subjected to the heat treatment.

[0041] In one embodiment of the present invention, the number average particle diameter of the base particles for conductive particles is preferably 1.0 to 7.0 μm. Because they are less likely to aggregate during plating, the number average particle diameter of the base particles for conductive particles is preferably 1.2 to 5.0 μm, and particularly preferably 1.5 to 3.0 μm. The number average particle diameter of the base particles for conductive particles can be measured by the method described in the examples.

[0042] In addition, the base particles for conductive particles according to the present invention preferably have excellent dispersibility in an alkaline solution, because when the base particles for conductive particles have excellent dispersibility in an alkaline solution, aggregation of the base particles for conductive particles is unlikely to occur during the plating treatment and pretreatment steps described below, resulting in good plating properties.

[0043] For example, the dispersibility of the base particles for conductive particles in an alkaline solution is preferably such that the value of α (dispersibility in alkaline solution) calculated by the following formula is 10% or less.

[0044] α(%)=(|Da-Db| / Db)×100 Here, Da represents the average dispersed particle size of conductive particle substrate particles in an alkaline solution, and Db represents the average dispersed particle size of conductive particle substrate particles in ion-exchanged water containing a dispersant. Da is the volume-based average particle size measured using a Coulter Multisizer III (manufactured by Beckman Coulter, Inc., measurement range 1 to 10 μm, with coincidence correction) after adding 1 part of conductive particle substrate particles to 20 parts of a 0.1% by mass sodium hydroxide aqueous solution (a mixed solution of water:methanol in a 1:1 mass ratio).

[0045] On the other hand, the Db was determined by adding 1 part of conductive particle base particles to 4000 parts of a 1% by mass aqueous solution of Hitenol (registered trademark) N-08 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), ultrasonicating for 10 minutes to disperse the conductive particle base particles in the aqueous solution, and then magnifying the sample 500 times with a Power High Scope (manufactured by HiROX, KH-2700) to confirm the absence of agglomerated particles. The volume-based average diameter Db (average primary particle diameter) was then measured using a Coulter Multisizer III (measurement range 1-10 μm, with coincidence correction). In other words, Db approximates the state in which the conductive particle base particles are dispersed as primary particles.

[0046] In order to prevent particle aggregation during plating and its pretreatment, the alkali dispersibility of the conductive particle substrate particle in the present invention is preferably 10% or less, more preferably 8% or less, even more preferably 5% or less, and particularly preferably 3% or less, in terms of α value. The lower limit is not particularly specified, but may be 0.1% or more.

[0047] In addition, the base particle for conductive particles according to the present invention preferably has excellent dispersibility in an aqueous solution. The dispersibility in water can be evaluated by the following procedure.

[0048] <Evaluation of dispersibility in water> 0.1 parts of conductive particle base particles, 4 parts of 1% emulsified water, and 1.2 parts of methanol were added to a sample tube and stirred with a stirrer for 15 minutes. After stirring, the dispersion state of the conductive particle base particles was observed using a microscope at 2500x magnification, with a field of view of 122.5 μm square and at least 100 fields of view, and the presence or absence of aggregation was confirmed visually.

[0049] [2. Conductive Particles] A conductive particle according to one embodiment of the present invention (hereinafter also simply referred to as "conductive particle") has at least one conductive metal layer formed on the surface of a base particle for a conductive particle.

[0050] The metal constituting the conductive metal layer is not particularly limited, and examples thereof include metals and metal compounds such as gold, silver, copper, platinum, iron, lead, aluminum, chromium, palladium, nickel, rhodium, ruthenium, antimony, bismuth, germanium, tin, cobalt, indium, nickel-phosphorus, and nickel-boron, as well as alloys thereof. Among these, gold, nickel, palladium, silver, copper, and tin are preferred because they form conductive fine particles with excellent conductivity. Furthermore, in terms of cost, nickel and nickel alloys (Ni-Au, Ni-Pd, Ni-Pd-Au, Ni-Ag); copper and copper alloys (Cu alloys with at least one metal element selected from the group consisting of Fe, Co, Ni, Zn, Sn, In, Ga, Tl, Zr, W, Mo, Rh, Ru, Ir, Ag, Au, Bi, Al, Mn, Mg, P, and B, preferably Ag, Ni, Sn, and Zn); silver and silver alloys (Ag alloys with Fe, Co, An alloy with at least one metal element selected from the group consisting of Ni, Zn, Sn, In, Ga, Tl, Zr, W, Mo, Rh, Ru, Ir, Au, Bi, Al, Mn, Mg, P, and B, preferably Ag-Ni, Ag-Sn, and Ag-Zn; tin, tin alloys (e.g., Sn-Ag, Sn-Cu, Sn-Cu-Ag, Sn-Zn, Sn-Sb, Sn-Bi-Ag, Sn-Bi-In, Sn-Au, and Sn-Pb), and the like are preferred.

[0051] The conductive metal layer may be a single layer or multiple layers. In the case of multiple layers, preferred combinations include nickel (nickel alloy)-gold, nickel (nickel alloy)-palladium, nickel (nickel alloy)-palladium-gold, and nickel (nickel alloy)-silver.

[0052] The thickness of the conductive metal layer is preferably 0.01 μm or more, more preferably 0.03 μm or more, even more preferably 0.05 μm or more, and is preferably 0.20 μm or less, more preferably 0.18 μm or less, even more preferably 0.15 μm or less, even more preferably 0.12 μm or less, and particularly preferably 0.08 μm or less. In conductive particles in which the base particles for conductive particles that serve as the base have a fine particle diameter, if the thickness of the conductive metal layer is within the above range, stable electrical connection can be maintained when the conductive particles are used as an anisotropic conductive material.

[0053] The method for forming the conductive metal layer is not particularly limited, and examples thereof include a method of plating the surface of a substrate by electroless plating, electrolytic plating, etc., and a method of forming a conductive metal layer on the surface of a substrate by a physical vapor deposition method such as vacuum deposition, ion plating, ion sputtering, etc. Among these, the electroless plating method is particularly preferred because it does not require a large-scale apparatus and can easily form a conductive metal layer.

[0054] Typically, electroless plating consists of three steps: (1) a hydrophilic step (etching), (2) a catalytic step, and (3) an electroless plating step.

[0055] The hydrophilization step (etching) is carried out to form minute irregularities on the surface of the base particle to improve the adhesion of the metal plating layer. The hydrophilization step (etching) forms minute irregularities on the surface of the base particle using, for example, an oxidizing agent such as chromic acid, a sulfuric acid-chromic acid mixture, or a permanganic acid solution; a strong acid such as hydrochloric acid or sulfuric acid; or a strong alkaline solution such as sodium hydroxide or potassium hydroxide.

[0056] The catalyzing step is carried out to form a catalyst layer on the surface of the base particle, which can serve as a starting point for the electroless plating step. Any appropriate method can be used to form the catalyst layer.

[0057] For example, a commercially available catalytic reagent for electroless plating can be used, such as Pink Sumer (manufactured by Nippon Kanigen Co., Ltd.) and Red Sumer (manufactured by Nippon Kanigen Co., Ltd.).

[0058] Specific examples of methods for forming a catalyst layer include a method in which base particles are immersed in a solution consisting of palladium chloride and tin chloride, and then activated with a strong acid such as sulfuric acid or hydrochloric acid or a strong alkaline solution such as sodium hydroxide to precipitate palladium on the surface of the base particles; and a method in which base particles are immersed in a palladium sulfate solution, and then activated with a solution containing a reducing agent such as dimethylamine borane to precipitate palladium on the surface of the base particles.

[0059] In the electroless plating step, the base particles are preferably thoroughly dispersed in an aqueous medium to prepare an aqueous slurry. Here, it is preferable that the base particles are thoroughly dispersed in the aqueous medium. If the metal plating layer is formed with the base particles in an agglomerated state, the untreated surface may be exposed. Any appropriate dispersion method can be used to disperse the base particles. Examples include normal stirring, high-speed stirring, and dispersion using a shear dispersion device such as a colloid mill or homogenizer. Ultrasonic irradiation may be used in combination with the dispersion. A dispersant such as a surfactant may also be used in the dispersion. Next, the dispersed base particle slurry is added to an electroless plating bath containing a metal salt, a reducing agent, a complexing agent, etc., and electroless plating is performed.

[0060] When a nickel salt is used, examples of the metal salt include nickel chloride, nickel sulfate, and nickel acetate.

[0061] Examples of the reducing agent include sodium hypophosphite, dimethylamine borane, sodium borohydride, potassium borohydride, and hydrazine.

[0062] Examples of the complexing agent include citric acid, hydroxyacetic acid, tartaric acid, malic acid, lactic acid, gluconic acid, or carboxylic acid salts such as alkali metal salts or ammonium salts thereof, amino acids such as glycine, amine acids such as ethylenediamine and alkylamines, ammonium compounds, EDTA, pyrophosphoric acid (salts), etc. The complexing agents may be used alone or in combination of two or more.

[0063] The pH of the plating bath in the electroless plating method is preferably 4-14.

[0064] In the electroless plating method, when the slurry of base particles is added, a reaction begins immediately, accompanied by the generation of hydrogen gas. The electroless plating process is considered to be complete when the generation of hydrogen gas is no longer observed.

[0065] [3. Anisotropic Conductive Materials] The anisotropic conductive material according to one embodiment of the present invention (hereinafter also simply referred to as "anisotropic conductive material") may be any material that contains the conductive particles described above.

[0066] The form of the anisotropic conductive material is not particularly limited, and various forms such as anisotropic conductive films, anisotropic conductive pastes, anisotropic conductive adhesives, and anisotropic conductive inks can be used. By providing these anisotropic conductive materials on opposing substrates or on electrode terminals, good electrical connection can be achieved. The anisotropic conductive material using the conductive particles of the present invention also includes conductive materials for liquid crystal display elements (conductive spacers and compositions thereof).

[0067] In the anisotropic conductive material, the content of conductive particles may be determined appropriately depending on the application, but is, for example, preferably 1% by volume or more, more preferably 2% by volume or more, and even more preferably 5% by volume or more, and preferably 50% by volume or less, more preferably 30% by volume or less, and even more preferably 20% by volume or less, relative to the total amount of the anisotropic conductive material. If the content of conductive particles is too low, it may be difficult to obtain sufficient electrical conductivity, while if the content of conductive particles is too high, the conductive particles may come into contact with each other, making it difficult to function as an anisotropic conductive material.

[0068] An anisotropic conductive paste according to one embodiment of the present invention (hereinafter also referred to simply as "anisotropic conductive paste") contains the conductive particles described above and a binder resin. The anisotropic conductive paste is formed by dispersing the conductive particles in the binder resin.

[0069] The binder resin is not particularly limited as long as it is an insulating resin, and examples thereof include thermoplastic resins such as acrylic resin, ethylene-vinyl acetate resin, and styrene-butadiene block copolymer; curable resin compositions that are cured by reaction with a curing agent such as a monomer or oligomer having a glycidyl group and an isocyanate; and curable resin compositions that are cured by light or heat.

[0070] The film thickness of the anisotropic conductive material, the coating thickness of the paste or adhesive, the printing thickness, etc. are preferably set appropriately taking into consideration the particle diameter of the conductive fine particles used and the specifications of the electrodes to be connected, so that the conductive particles are sandwiched between the electrodes to be connected and the gaps between the bonding substrates on which the electrodes to be connected are formed are sufficiently filled with the binder resin layer.

[0071] 4. Method for producing substrate particles for conductive particles The method for producing the conductive particle substrate particles is not particularly limited, and examples thereof include emulsion polymerization, suspension polymerization, dispersion polymerization, seed polymerization, and sol-gel seed polymerization. However, to adjust the particle diameter of the conductive particle substrate particles to a desired range, for example, a method in which conductive particle substrate particles are synthesized by seed polymerization and then classified is preferably employed. By adopting seed polymerization for synthesizing conductive particle substrate particles, conductive particle substrate particles with a narrow particle size distribution can be obtained. Furthermore, by classifying the synthesized conductive particle substrate particles to remove coarse particles, the average particle diameter can be adjusted to a desired range.

[0072] The seed polymerization method includes a seed particle preparation step, an absorption step, and a polymerization step. For example, when synthesizing particles composed only of a vinyl polymer, the seed particles can be prepared from a vinyl monomer such as the monomer unit represented by formula (1). When synthesizing particles composed of a vinyl monomer and a material having a polysiloxane structure, the seed particles (i.e., polysiloxane particles) can be prepared from the silane compound.

[0073] A method for preparing seed particles (i.e., polysiloxane particles) from a silane compound includes hydrolysis and condensation polymerization in a solvent containing water. Furthermore, when a polysiloxane structure and a vinyl polymer are to be composited, a silane-based crosslinkable monomer having a radical polymerizable group is used as the silane compound to prepare polymerizable polysiloxane particles (i.e., particles having a polysiloxane structure having a radical polymerizable group). Any method, such as batch, division, or continuous hydrolysis and condensation polymerization, can be used. For hydrolysis and condensation polymerization, a basic catalyst such as ammonia, urea, ethanolamine, tetramethylammonium hydroxide, alkali metal hydroxide, or alkaline earth metal hydroxide can be preferably used as a catalyst.

[0074] The water-containing solvent may contain an organic solvent in addition to water and a catalyst. Examples of the organic solvent include alcohols such as methanol, ethanol, isopropanol, n-butanol, isobutanol, sec-butanol, t-butanol, pentanol, ethylene glycol, propylene glycol, and 1,4-butanediol; ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate; (cyclo)paraffins such as isooctane and cyclohexane; and aromatic hydrocarbons such as benzene and toluene. These may be used alone or in combination of two or more.

[0075] In the hydrolysis condensation, anionic, cationic, or nonionic surfactants, or polymer dispersants such as polyvinyl alcohol or polyvinylpyrrolidone can also be used in combination. These can be used alone or in combination of two or more. The hydrolysis condensation can be carried out by mixing the raw material silane monomer with a catalyst, water, and a solvent containing an organic solvent, and then stirring the mixture at a temperature of 0°C to 100°C, preferably 0°C to 70°C, for 10 minutes to 100 hours.

[0076] In the absorption step, a vinyl monomer, such as a monomer unit represented by formula (1), is absorbed into seed particles. The absorption method is not particularly limited as long as it proceeds in the presence of seed particles and the vinyl monomer. Therefore, the vinyl monomer may be added to a solvent in which seed particles are dispersed, or the seed particles may be added to a solvent containing the vinyl monomer. Of these, the former method, in which the vinyl monomer is added to a solvent in which seed particles are previously dispersed, is preferred. In particular, the method of adding the vinyl monomer to the reaction liquid (seed particle dispersion liquid) obtained in the hydrolysis and condensation steps without removing the seed particles from the reaction liquid is preferred because it does not complicate the process and is highly productive.

[0077] In the absorption step, the timing of adding the vinyl monomer is not particularly limited, and the vinyl monomer may be added all at once, may be added in several portions, or may be fed at any rate. When adding the vinyl monomer, either the vinyl monomer alone or a solution of the vinyl monomer may be added, but it is preferable to mix an emulsion in which the vinyl monomer is previously emulsified and dispersed in water or an aqueous medium with an emulsifier with the seed particles, because this allows the vinyl monomer to be absorbed into the seed particles more efficiently.

[0078] The emulsifier is not particularly limited, but for example, anionic surfactants and nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxysorbitan fatty acid esters, polyoxyethylene alkylamines, glycerin fatty acid esters, and oxyethylene-oxypropylene block polymers are preferred because they can stabilize the dispersion state of the seed particles after absorbing the vinyl monomer. These emulsifiers may be used alone or in combination of two or more.

[0079] When emulsifying and dispersing a vinyl monomer with an emulsifier, it is preferable to use water or a water-soluble organic solvent in an amount of 0.3 to 10 times the mass of the vinyl monomer. Examples of the water-soluble organic solvent include alcohols such as methanol, ethanol, isopropanol, n-butanol, isobutanol, sec-butanol, t-butanol, pentanol, ethylene glycol, propylene glycol, and 1,4-butanediol; ketones such as acetone and methyl ethyl ketone; and esters such as ethyl acetate.

[0080] The absorption step is preferably carried out at a temperature ranging from 0°C to 60°C for 5 minutes to 720 minutes with stirring. These conditions may be appropriately set depending on the types of seed particles and monomers used, and one or more of these conditions may be used. Whether the vinyl monomer has been absorbed into the seed particles in the absorption step can be easily determined, for example, by observing the particles with a microscope before adding the vinyl monomer and after the absorption step is completed, and confirming that the particle size has increased due to the absorption of the vinyl monomer.

[0081] In the polymerization step, the vinyl monomer absorbed into the seed particles is polymerized. When the seed particles are polymerizable polysiloxanes, the absorbed vinyl monomer and the radically polymerizable groups of the polymerizable polysiloxane structure are polymerized, resulting in a composite of the polysiloxane structure and the vinyl polymer. The polymerization method is not particularly limited, but examples include methods using a radical polymerization initiator. The radical polymerization initiator is not particularly limited, but examples include peroxide initiators and azo initiators. These radical polymerization initiators may be used alone or in combination.

[0082] The reaction temperature during radical polymerization is preferably 40° C. or higher, more preferably 50° C. or higher, and is preferably 100° C. or lower, more preferably 80° C. or lower. If the reaction temperature is too low, the degree of polymerization will not increase sufficiently, and the mechanical properties of the particles will tend to be insufficient. On the other hand, if the reaction temperature is too high, aggregation between particles will tend to occur more easily during polymerization.

[0083] The reaction time for radical polymerization may be appropriately changed depending on the type of polymerization initiator used, but is usually preferably 5 minutes or more, more preferably 10 minutes or more, and preferably 600 minutes or less, more preferably 300 minutes or less. If the reaction time is too short, the degree of polymerization may not be sufficiently increased, and if the reaction time is too long, aggregation between particles tends to occur easily.

[0084] The conductive particle substrate particles synthesized as described above are preferably classified to a predetermined particle size, if necessary. The classification method is not particularly limited, and examples include sieving using an electroformed sieve or the like; filtration using a filter such as a membrane filter, pleated filter, or ceramic membrane filter; and classification using known devices that classify based on the interaction between mass difference and fluid resistance difference (gravity classifiers, which rely on the gravitational difference in particle falling speed, etc.; (semi-)free vortex centrifugal classification, which relies on the balance between centrifugal force generated by a free or semi-free vortex and air drag; and centrifugal classification with rotating blades, which relies on the balance between centrifugal force generated by a rotating flow created by a rotating classification blade (rotor) and air drag). Among these, classification using an electroformed sieve is preferred from the standpoint of classification accuracy and productivity.

[0085] When using an electroformed sieve for classification, it is preferable to pass a dispersion of conductive particle substrate particles in a liquid medium through the electroformed sieve. Examples of the liquid medium include water; alcohols such as methanol, ethanol, propanol, and butanol; hydrocarbons such as hexane and octane; and aromatic hydrocarbons such as benzene, toluene, and xylene.

[0086] These may be used alone or in combination of two or more. Among these, alcohols and hydrocarbons are preferred, and methanol and hexane are more preferred. In addition, various dispersants may be added to the liquid medium to improve the dispersibility of the conductive particle substrate particles.

[0087] The amount of the liquid medium used is preferably 100 parts by mass or more, more preferably 200 parts by mass or more, and even more preferably 500 parts by mass or more, relative to 100 parts by mass of the base particles for conductive particles, and is preferably 10,000 parts by mass or less, more preferably 5,000 parts by mass or less, and even more preferably 2,000 parts by mass or less. The method for dispersing the base particles for conductive particles in the liquid medium is not particularly limited, and examples thereof include a method of dispersing by irradiation with ultrasonic waves; a method of dispersing by using a shear dispersion device such as a normal stirrer, a high-speed stirrer, a colloid mill, or a homogenizer; and the like.

[0088] The temperature of the dispersion liquid when passing through the electroformed sieve is not particularly limited and may be adjusted appropriately depending on the liquid medium used, but is usually between 0°C and 100°C. The temperature of the dispersion liquid is, of course, below the boiling point of the liquid medium. The size of the sieve holes in the electroformed sieve may be changed depending on the desired average particle size and coefficient of variation. By classifying using an electroformed sieve, coarse particles can be removed, and the coefficient of variation of the particle size of the conductive particle substrate particles can be reduced.

[0089] The number-based coefficient of variation of the particle diameter of the conductive particle substrate particles after synthesis is preferably 15% or less, more preferably 10% or less, and even more preferably 8% or less. The particle diameter and the coefficient of variation of the conductive particle substrate particles can be measured by the method described in the Examples.

[0090] After synthesis, the conductive particle base particles, which have been classified as necessary, are usually dried and, in some cases, subjected to the above-mentioned firing (heat treatment). Heat treatments such as drying and firing may be carried out according to known methods.

[0091] The shape of the base particle (base material) for conductive particles obtained as described above is not particularly limited, and may be, for example, spherical, spheroidal, confetti-like, thin plate-like, needle-like, cocoon-like, etc., but spherical is preferred, and true sphere is particularly preferred. [Example]

[0092] The present invention will be described in more detail below with reference to examples. The present invention is not limited to the following examples, and can of course be practiced with appropriate modifications within the scope of the above and below-described aims, provided that such modifications do not deviate from the spirit of the present invention, and all such modifications are included in the technical scope of the present invention.

[0093] 1. Physical property measurement and evaluation methods Various physical properties were measured by the following methods.

[0094] <Number average particle size and coefficient of variation (CV value) of seed particles and base particles for conductive particles> 20 parts of a 1% aqueous solution of polyoxyethylene alkyl ether sulfate ester ammonium salt (Hitenol® N-08, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), an emulsifier, was added to 0.005 parts of seed particles or conductive particle substrate particles, and after 10 minutes of ultrasonic treatment, the particle sizes (μm) of 30,000 particles were measured using a particle size distribution analyzer (Coulter Multisizer III, manufactured by Beckman Coulter, Inc.) to determine the number-based average particle size. The number-based average particle size and standard deviation of the particle sizes were also determined, and the number-based CV value (coefficient of variation) of the particle sizes was calculated according to the following formula: Coefficient of variation of particles (%) = 100 x (standard deviation of particle size / number-based average particle size)

[0095] <Evaluation of dispersibility in water> 0.1 parts of conductive particle base particles, 4 parts of 1% emulsified water, and 1.2 parts of methanol were added to a sample tube and stirred with a stirrer for 15 minutes. After stirring, the dispersion state of the conductive particle base particles was observed using a microscope with a magnification of 2500x, covering a field of view of 122.5 μm square, with at least 100 fields of view. The results were evaluated under the following conditions. ○: Dispersed into single particles. △1: Single particles are present, but less than 2 to 5 particles are aggregated. △2: There are two or more aggregates consisting of five or more particles. ×: Aggregates of 10 or more particles are present.

[0096] <Evaluation of alkali dispersibility> One part of the base particles for conductive particles is added to 20 parts of a 0.1 mass % aqueous solution of sodium hydroxide (a mixed solution of water and methanol in a mass ratio of 1:1), and the mixture is stirred at 25°C for 20 minutes. Thereafter, the volume-based average particle diameter Da is measured using a Coulter Multisizer III (manufactured by Beckman Coulter, Inc., measurement range 1 μm to 10 μm, with coincidence correction).

[0097] Next, 1 part of the base particles for conductive particles is added to 4000 parts of a 1 mass % aqueous solution of Hitenol (registered trademark) N-08 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), and ultrasonic treatment is performed for 10 minutes to disperse the base particles for conductive particles in the aqueous solution. After that, the sample is magnified 500 times with a microscope (manufactured by HiROX, KH-2700) to confirm the absence of agglomerated particles, and the volume-based average diameter Db (average primary particle diameter) is measured using a Coulter Multisizer Model III (measurement range 1 μm to 10 μm, with coincidence correction).

[0098] The obtained values ​​of Da and Db were introduced into the following formula to calculate the dispersibility α (%) in the alkaline solution, which was then evaluated according to the following criteria. α(%)=(|Da-Db| / Db)×100 ○: α is less than 10% △: α is less than 20% ×: α is 20% or more

[0099] <Measurement of Si content in base particles for conductive particles> The mass equivalent to Si was calculated from the ash mass Xa (referred to as the SiO2 amount) when the conductive particle substrate particle was fired at 950°C in an oxidizing atmosphere such as air, and the Si amount was divided by the mass Xb of the conductive particle substrate particle subjected to the firing treatment. To calculate the mass equivalent to Si from the ash mass, the ash mass Xa was multiplied by 0.4672 (Si atomic weight / SiO2 formula weight). That is, the Si content β was calculated using the following formula: β(%)=(Xa×0.4672) / Xb

[0100] <Measurement of the polymer ratio in the base particles for conductive particles> The proportion of polymer in the base particle for conductive particles was determined by dividing the remaining mass after treating the base particle for conductive particles at 105°C for 60 minutes in an inert atmosphere such as nitrogen by the mass of the base particle for conductive particles subjected to the heat treatment.

[0101] 2. Preparation of base particles for conductive particles

[0102] [Example 1] A four-neck flask equipped with a condenser, a thermometer, and a dropping nozzle was charged with 1,600 parts of ion-exchanged water, 20 parts of 25% aqueous ammonia, and 400 parts of methanol. With stirring, 80.0 parts of 3-methacryloxypropyltrimethoxysilane (KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd., hereinafter referred to as "MPTMS") was added as a polymerizable silane compound (inorganic component) through the dropping nozzle. The mixture was stirred to carry out a hydrolysis and condensation reaction of MPTMS, thereby preparing an emulsion of polysiloxane particles (seed particles) having methacryloyl groups.

[0103] Next, 0.64 parts of a 20% aqueous solution of polyoxyethylene styrenated phenyl ether sulfate ester ammonium salt (Dai-ichi Kogyo Seiyaku Co., Ltd. "Hitenol (registered trademark) NF-08") as an emulsifier was dissolved in 40.4 parts of ion-exchanged water, and 32.0 parts of divinylbenzene (DVB, Nippon Steel Chemical Co., Ltd.: containing 96% divinylbenzene and 4% ethylvinylbenzene) as an absorbing monomer (monomer component), 16.0 parts of 2-(hydroxymethyl)methyl acrylate (RHMA), and 1.9 parts of 2,2'-azobis(2,4-dimethylvaleronitrile) (Wako Pure Chemical Industries, Ltd. "V-65") were added to the solution, and the mixture was emulsified and dispersed using a TK Homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to prepare an emulsion of the absorbing monomer. After 1 hour from the start of emulsification and dispersion, the resulting emulsion was added to the emulsion of polysiloxane particles (seed particles) and further stirred. One hour after the addition of the emulsion, a sample of the mixed liquid was taken and observed under a microscope, and it was confirmed that the polysiloxane particles had absorbed the absorbing monomer and had become enlarged.

[0104] Next, 2.0 parts of a 20% aqueous solution of polyoxyethylene styrenated phenyl ether sulfate ester ammonium salt was added, and the reaction solution was heated to 65°C under a nitrogen atmosphere and maintained at 65°C for 2 hours to carry out radical polymerization of the monomer components. The emulsion after radical polymerization was subjected to solid-liquid separation, and the resulting cake was washed with ion-exchanged water and methanol, and then vacuum-dried at 80°C for 4 hours under a nitrogen atmosphere to obtain base particles for conductive particles (1).

[0105] [Example 2] A base particle (2) for conductive particles was obtained in the same manner as in Example 1, except that vinyltrimethoxysilane (KBM-1003 manufactured by Shin-Etsu Chemical Co., Ltd., hereinafter referred to as VTMS) was used instead of MPTMS as the polymerizable silane compound (inorganic component).

[0106] [Comparative Example 1] Base particle (3) for conductive particles was obtained in the same manner as in Example 1, except that only 32.0 parts of divinylbenzene (DVB) was used as the absorbing monomer.

[0107] Comparative Example 2 Base particle (4) for conductive particles was obtained in the same manner as in Example 1, except that 80.0 parts of medivinylbenzene (DVB) and 80.0 parts of methyl 2-(hydroxymethyl)acrylate (RHMA) were used as the absorbing monomers.

[0108] Comparative Example 3 Base particle (5) for conductive particles was obtained in the same manner as in Example 1, except that 32.0 parts of 2-hydroxyethyl methacrylate (HEMA) was used instead of 2-(hydroxymethyl)methyl acrylate (RHMA) as the absorbing monomer.

[0109] Comparative Example 4 A base particle (6) for conductive particles was obtained in the same manner as in Comparative Example 3, except that the absorbing monomer was changed from 2-hydroxyethyl methacrylate (HEMA) to 32.0 parts of 2-(dimethylamino)ethyl methacrylate (DAM, Light Ester DM manufactured by Kyoeisha Chemical Co., Ltd.).

[0110] Comparative Example 5 Base particle (7) for conductive particles was obtained in the same manner as in Example 2, except that only 32.0 parts of divinylbenzene (DVB) was used as the absorbing monomer.

[0111] The number average particle diameter, coefficient of variation and dispersibility of the base particles for conductive particles (1) to (7) were evaluated as shown in Table 1.

[0112] [Table 1]

[0113] When Examples 1 and 2, which contain polymers having structural units derived from monomer units represented by formula (1), are compared with Comparative Examples 1 to 5 (which do not contain structural units derived from monomer units represented by formula (1) or contain an excessive amount of such units), it was confirmed that Examples 1 and 2 are superior to Comparative Examples 1 to 5 in both water dispersibility and alkali dispersibility. [Industrial Applicability]

[0114] The present invention can be utilized in fields where conductive materials are used.

Claims

1. The number average particle diameter is 1.0 to 7.0 μm, A base particle for a conductive particle, characterized in that it contains, on the particle surface, a polymer having a structure derived from a monomer unit represented by formula (1). 【Chemistry 1】 In the above formula (1), R １ is hydrogen or an organic group having 1 to 8 carbon atoms, R ２ , R ３ are the same or different and are a hydrogen atom, a methyl group, or an ethyl group, X is a methylene group, or a methylene group in which a hydrogen atom is substituted with a methyl group or a halogen.

2. 2. The base particle for conductive particles according to claim 1, wherein the structure derived from the monomer unit represented by formula (1) is 1 to 25 parts by mass relative to 100 parts by mass of the polymer.

3. 3. The base particle for conductive particles according to claim 1, wherein the polymer is present in an amount of 90 parts by mass or more relative to 100 parts by mass of the base particle for conductive particles.

4. The base particle for conductive particles according to any one of claims 1 to 3, characterized in that the base particle has an alkali dispersibility of 10% or less.

5. The base particle for a conductive particle according to any one of claims 1 to 4, which is a particle containing Si atoms.

6. The base particle for conductive particles according to any one of claims 1 to 5, wherein the content of Si is 1 to 25 parts by mass relative to 100 parts by mass of the polymer.

7. A method for producing a base particle for a conductive particle, comprising the steps of preparing a seed particle, allowing the seed particle to absorb a monomer represented by formula (1) and a polymerization initiator, and polymerizing the monomer. 【Chemistry 2】 In the above formula (1), R 1 is hydrogen or an organic group having 1 to 8 carbon atoms; R 2 and R 3 are the same or different and each represents a hydrogen atom, a methyl group, or an ethyl group; X is a methylene group, or a methylene group in which a hydrogen atom is substituted with a methyl group or a halogen.

8. The method for producing a base particle for a conductive particle according to claim 7 , wherein the seed particle is a seed particle obtained by condensing an organic silane compound.

9. A conductive particle comprising the substrate particle for conductive particles according to any one of claims 1 to 6, and at least one conductive metal layer formed on the surface thereof.

10. An anisotropic conductive material comprising the conductive particles of claim 9 .

11. An anisotropic conductive paste comprising the conductive particles according to claim 9 and a binder resin.

Images