Coated particles and method for producing the same

Abstract

The purpose of the present invention is to provide coated particles that can increase conduction reliability and insulation reliability. The coated particles comprise: conductive particles having a metal film formed on the surface of a core material; and insulating microparticles coating the conductive particles, wherein the insulating microparticles do not have a glass transition temperature, and have a sphericity of 0.90 or greater. The surface layer of the insulating microparticles is preferably a polymer containing a crosslinking monomer component, and is also preferably a polymer containing a monomer component having a functional group with an electric charge.

Description

Technical Field

[0001] The present invention relates to coated particles in which conductive particles are coated with an insulating layer.

Background Art

[0002] Conductive particles formed with a metal film such as nickel or gold on the surface of resin particles are used as conductive materials such as conductive adhesives, anisotropic conductive films, and anisotropic conductive adhesives.

[0003] In recent years, with the further miniaturization of electronic devices, the circuit width and pitch of electronic circuits have become increasingly smaller. Along with this, as conductive particles used in the above-mentioned conductive adhesives, anisotropic conductive films, anisotropic conductive adhesives, etc., those with a small particle size are required. When using such conductive particles with a small particle size, in order to enhance their connectivity, the blending amount of the conductive particles in the conductive material must be increased. However, when the blending amount of the conductive particles is increased, conduction in an unintended direction, that is, a short circuit occurs due to conduction in a direction different from between the opposing electrodes, and it has been a problem that it is difficult to obtain insulation in that direction.

[0004] In order to solve the above problems, insulating layer-coated conductive particles in which the surface of the conductive particles is coated with an insulating substance having a functional group having an affinity for the metal film to prevent contact between the metal films of the conductive particles are used. Coated particles having such a configuration usually have the insulating layer melted, deformed, or peeled by thermocompression bonding the coated particles between electrodes, and the metal surface of the conductive particles is exposed, thereby enabling conduction between the electrodes. However, by examining the constituent components of the insulating layer, techniques for improving characteristics such as conduction reliability are known.

[0005] For example, Patent Document 1 describes that conductive particles coated with core-shell particles having a glass transition temperature or softening temperature of the shell layer higher than that of the core particles can reliably establish a conductive connection between substrates and prevent leakage between adjacent particles. Patent Document 2 describes that conductive particles coated with water-dispersible core-shell particles having a glass transition temperature of -30 to 150°C, wherein the core contains a copolymer of styrene and 2-ethylhexyl acrylate and the shell contains a copolymer of styrene and acrylic acid, have been found to have excellent current feeding and insulation properties. Further, Patent Document 3 describes that conductive particles coated with resin particles containing a copolymer of a polymerizable component essentially comprising at least an alkyl (meth)acrylate and a polyvalent (meth)acrylate and having a glass transition temperature of 180°C or lower can provide insulating conductive particles that can reliably suppress lateral conduction while maintaining good conduction between opposing electrodes.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, when the anisotropic conductive material using the conductive particles described in Patent Documents 1 to 3 above is thermocompression bonded between electrodes, the insulating resin particles cannot maintain the desired hardness, and there is a problem that the deformed insulating resin particles are caught and remain between the conductive layer of the conductive particles and the electrodes, so that the desired conductivity cannot be exhibited. In order to reduce the influence on the hardness of the resin particles when heated, it is conceivable to obtain harder resin particles by increasing the proportion of the crosslinkable monomer component in the production of the resin particles and polymerizing. However, when the proportion of the crosslinkable monomer component is increased, the shape of the particles becomes irregular and it becomes difficult to control the particle diameter, resulting in problems with insulation reliability.

[0008] Therefore, an object of the present invention is to provide coated particles capable of enhancing the conductive reliability and insulation reliability that solve the above problems.

Means for Solving the Problems

[0009] As a result of intensive research to solve the above problems, the present inventors polymerize a non-crosslinkable monomer component to obtain a spherical core material portion when obtaining insulating fine particles, and then add and polymerize a crosslinkable monomer component. It has been found that insulating fine particles having no glass transition temperature, having the required hardness, and having a spherical shape and a uniform particle diameter can be obtained. And the insulating fine particles thus obtained are difficult to deform during thermocompression bonding and maintain a spherical shape, and are efficiently excluded without remaining between the conductive layer and the electrode. Therefore, it has been found that the conductive particles coated with this insulating fine particle have excellent conductive reliability, and the present invention has been completed.

[0010] That is, the present invention provides a coated particle having a conductive particle having a metal film formed on the surface of a core material and an insulating fine particle coating the conductive particle, wherein the insulating fine particle has no glass transition temperature and a sphericity of 0.90 or more.

[0011] The present invention also provides a method for producing coated particles having conductive particles with a metal film formed on the surface of a core material and insulating fine particles coating the conductive particles, comprising: a first step of polymerizing a non-crosslinkable monomer component to obtain a precursor of insulating fine particles; a second step of polymerizing a polymerizable compound containing a crosslinkable monomer component in the presence of the precursor of insulating fine particles to obtain insulating fine particles; and a third step of mixing a dispersion containing the insulating fine particles and the conductive particles to attach the insulating fine particles to the surface of the conductive particles.

Advantages of the Invention

[0012] According to the present invention, coated particles coated with insulating fine particles that are spherical and have a uniform particle diameter and do not have a glass transition temperature can be obtained, so that coated particles excellent in conduction reliability and insulation reliability and a method for producing the same can be provided.

Brief Description of the Drawings

[0013]

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BEST MODE FOR CARRYING OUT THE INVENTION

[0014] Hereinafter, the coated particles of the present invention will be described based on their preferred embodiments. The coated particles of the present invention are coated particles having conductive particles with a metal film formed on the surface of a core material and insulating fine particles covering the conductive particles, wherein the insulating fine particles do not have a glass transition temperature and have a sphericity of 0.90 or more.

[0015] As the conductive particles, known ones conventionally used in conductive adhesives, anisotropic conductive films, and anisotropic conductive adhesives can be used.

[0016] The core material in the conductive particles is in the form of particles and can be used without particular limitation whether it is an inorganic substance or an organic substance. Examples of inorganic core material particles include metal particles such as gold, silver, copper, nickel, palladium, and solder, alloys, glass, ceramics, silica, metal or non-metal oxides (including hydrates), metal silicates including aluminosilicates, metal carbides, metal nitrides, metal carbonates, metal sulfates, metal phosphates, metal sulfides, metal oxysalts, metal halides, and carbon. On the other hand, examples of organic core material particles include natural fibers, natural resins, thermoplastic resins such as polyethylene, polypropylene, polyvinyl chloride, polystyrene, polybutene, polyamide, polyacrylate ester, polyacrylonitrile, polyacetal, ionomer, and polyester, alkyd resins, phenol resins, urea resins, benzoguanamine resins, melamine resins, xylene resins, silicone resins, epoxy resins, and diallyl phthalate resins. These may be used alone or in combination of two or more.

[0017] Instead of being made of either the above-described inorganic or organic material, the core material particles may be composed of a material consisting of both an inorganic material and an organic material. When the core material particles are composed of a material consisting of both an inorganic material and an organic material, examples of the modes of existence of the inorganic material and the organic material in the core material particles include, for example, a mode including a core made of an inorganic material and a shell made of an inorganic material covering the surface of the core, or a core-shell type configuration such as a mode including a core made of an organic material and a shell made of an inorganic material covering the surface of the core. In addition to these, a blend type configuration in which an inorganic material and an organic material are mixed or randomly fused in one core material particle can be mentioned. As the core material particles composed of a material consisting of both an inorganic material and an organic material, the materials constituting the above-described inorganic core material particles or organic core material particles can be used. These core material particles may be used so as to be composed of each of the inorganic and organic materials alone, or may be used so as to be composed by combining each of the inorganic and organic materials with two or more types of materials.

[0018] The core material particles are preferably composed of a material consisting of an organic material or both an inorganic material and an organic material, and more preferably composed of a material consisting of both an inorganic material and an organic material. The inorganic material is preferably glass, ceramic, silica, a metal or a non-metal oxide (including hydrates), a metal silicate including aluminosilicate, a metal carbide, a metal nitride, a metal carbonate, a metal sulfate, a metal phosphate, a metal sulfide, a metal oxysalt, a metal halide, and carbon. The organic material is preferably a thermoplastic resin such as natural fiber, natural resin, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polybutene, polyamide, polyacrylate, polyacrylonitrile, polyacetal, ionomer, and polyester. By using a core material made of such a material, the dispersion stability between particles can be enhanced, and when making an electrical connection of an electronic circuit, appropriate elasticity can be exhibited to enhance conduction.

[0019] When using an organic substance as the core material particles, it is preferable that the core material particles do not have a glass transition temperature or that the glass transition temperature is above 100 °C, from the viewpoints that the shape of the core material particles is easily maintained in the anisotropic conductive connection process and that the shape of the core material particles is easily maintained in the process of forming a metal film. Further, when the core material particles have a glass transition temperature, it is preferable that the glass transition temperature is 200 °C or lower, from the viewpoint that the conductive particles are easily softened and the contact area becomes large in the anisotropic conductive connection, making it easier to establish conduction. From this viewpoint, when the core material particles have a glass transition temperature, the glass transition temperature is more preferably above 100 °C and 180 °C or lower, and particularly preferably above 100 °C and 160 °C or lower. The glass transition temperature can be measured by the method described in the examples below.

[0020] When an organic substance is used as the core material particles, when the organic substance is a highly cross-linked resin, even if an attempt is made to measure the glass transition temperature up to 200 °C by the method described in the following examples, it is hardly observed. In this specification, such particles are also referred to as particles having no glass transition point, and in the present invention, such core material particles may be used. Specific examples of the core material particle material having no such glass transition temperature as described above can be obtained by copolymerizing a crosslinkable monomer in combination with the monomer constituting the organic substance exemplified above. Examples of the crosslinkable monomer include tetraethylene di(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol (meth)acrylate, ethylene oxide di(meth)acrylate, tetraethylene oxide (meth)acrylate, 1,6-hexane di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane di(meth)acrylate, tetramethylolmethane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, tetramethylolpropane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, glycerol di(meth)acrylate, glycerol tri(meth)acrylate and other polyfunctional (meth)acrylates, polyfunctional vinyl monomers such as divinylbenzene and divinyltoluene, silane-containing monomers such as vinyltrimethoxysilane, trimethoxysilylstyrene, and γ-(meth)acryloxypropyltrimethoxysilane, and monomers such as triallyl isocyanurate, diallyl phthalate, diallyl acrylamide, and diallyl ether. Particularly in the COG (Chip on Glass) field, core material particles made of such hard organic materials are widely used.

[0021] There is no particular limitation on the shape of the core material particles. Generally, the core material particles are spherical. However, the core material particles may have a shape other than spherical, such as fibrous, hollow, plate-like or needle-like, or may have a large number of protrusions on their surface or be amorphous. In the present invention, spherical core material particles are preferred in terms of excellent filling properties and ease of coating with metal.

[0022] The shape of the conductive particles is not particularly limited, although it depends on the shape of the core material particles. For example, it may be fibrous, hollow, plate-like or needle-like, or may have protrusions on its surface or be amorphous. In the present invention, a spherical shape or a shape having protrusions on the surface is preferred in terms of excellent filling properties and connectivity. When the conductive particles have a shape having protrusions on the surface, it is preferable to have a plurality of protrusions on the surface, and it is more preferable to have a plurality of protrusions on the spherical surface. When the conductive particles have a shape having a plurality of protrusions, the core material particles may have a plurality of protrusions, or the core material particles may have no protrusions and the metal film may have a plurality of protrusions. Preferably, the core material particles have no protrusions and the metal film has a plurality of protrusions.

[0023] In order to ensure electrical conduction, the coated particles of the present invention may have protrusions on the surface of the conductive particles. By having protrusions on the surface of the conductive particles, when the conductive particles are compressed by the electrodes during mounting, the protrusions can effectively push back the insulating layer. The height H of the protrusions of the conductive particles is preferably such that H / L is 0.1 or more from the viewpoint of eliminating the insulating layer during mounting and ensuring electrical conduction, where L is the thickness of the insulating layer. Also, it is preferable that H / L is 10 or less from the viewpoint of obtaining filling properties and insulation in a direction different from the counter electrode. From these points, it is even more preferable that H / L is 0.2 or more and 5 or less. In these preferred ranges, the thickness L refers to the average particle diameter of the insulating fine particles when the insulating layer is insulating fine particles.

[0024] The height H of the protrusions is preferably 20 nm or more, particularly preferably 50 nm or more on average. The number of protrusions depends on the particle size of the conductive particles, but from the viewpoint of further improving the conductivity of the conductive particles, it is preferably 1 to 20,000, particularly 5 to 5,000 per particle. Also, the aspect ratio of the protrusions is preferably 0.3 or more, more preferably 0.5 or more. When the aspect ratio of the protrusions is large, it is advantageous because the oxide film formed on the electrode surface can be easily pierced. The aspect ratio is a value defined as the ratio of the height H of the protrusion to the length D of the base of the protrusion, that is, H / D. The height H of the protrusion and the length D of the base of the protrusion are average values measured for 20 different particles observed by an electron microscope, and the aspect ratio of the protrusions is calculated from the aspect ratios of 20 different particles observed by an electron microscope, and the average value thereof is obtained. The length D of the base refers to the length along the surface of the conductive particle at the base of the protrusion in the electron microscope image.

[0025] The aspect ratio of the protrusions formed on the surface of the conductive particles is as described above. The length D of the base of the protrusion itself is preferably 5 to 500 nm, particularly preferably 10 to 400 nm, and the height H of the protrusion is preferably 20 to 500 nm, particularly preferably 50 to 400 nm.

[0026] The metal film in the conductive particles has conductivity. Examples of the constituent metals include metals such as gold, platinum, silver, copper, iron, nickel, tin, lead, antimony, bismuth, cobalt, indium, titanium, germanium, aluminum, chromium, palladium, tungsten, molybdenum, or alloys thereof, and metal compounds such as ITO and solder. Among them, gold, silver, copper, nickel, palladium, or solder is preferable because of low resistance. In particular, nickel, gold, nickel alloy, or gold alloy is preferably used because of its high binding property with the functional group when the insulating fine particles of the present invention described later have a functional group. The metal in the conductive particles can be used alone or in combination of two or more.

[0027] The metal film may have a single-layer structure or a laminated structure composed of multiple layers. When it has a laminated structure composed of multiple layers, it is preferable that the outermost layer is nickel, gold, a nickel alloy, or a gold alloy. The outermost layer of the metal film preferably contains a small amount of palladium, preferably 5% by mass or less, more preferably 1% by mass or less, and most preferably contains no palladium, from the viewpoint of reducing the amount of expensive noble metals.

[0028] Also, the metal film does not have to cover the entire surface of the core material particles, and may cover only a part of the surface. When only a part of the surface of the core material particles is covered, the covered portions may be continuous, or may be discontinuously covered, for example, in an island shape. The thickness of the metal film is preferably 0.001 μm or more and 2 μm or less.

[0029] Examples of the method for forming a metal film on the surface of the core material particles include dry methods using vapor deposition, sputtering, mechanochemical, hybridization, etc., and wet methods using electrolytic plating, electroless plating, etc. Further, these methods may be combined to form a metal film on the surface of the core material particles.

[0030] The average particle diameter of the conductive particles is preferably 0.1 μm or more and 50 μm or less, more preferably 1 μm or more and 30 μm or less. When the average particle diameter of the conductive particles is within the above range, the obtained coated particles can easily ensure conduction between the counter electrodes without causing a short circuit in a direction different from that between the counter electrodes. In the present invention, the average particle diameter of the conductive particles is the average value of the particle diameters measured using a scanning electron microscope (SEM). When the conductive particles are spherical in the scanning electron microscope image, the particle diameter measured using SEM is the diameter of the circular conductive particle image. When the conductive particles are not spherical, the particle diameter measured using SEM refers to the largest length (maximum length) of the line segments crossing the image of the conductive particles. This also applies to the average particle diameter of the insulating fine particles described later. However, when the conductive particles have protrusions, the average of the above maximum lengths for the portions other than the protrusions is taken as the average particle diameter.

[0031] Specifically, the average particle diameter of the conductive particles is measured by the method described in the examples.

[0032] The insulating fine particles that coat the conductive particles used in the present invention do not have a glass transition temperature. As a result, the coated particles of the present invention are coated with insulating fine particles that are difficult to deform during thermocompression bonding, so that the insulating fine particles are efficiently removed without remaining between the conductive layer and the electrode. Therefore, the coated particles of the present invention have an increased connectivity with the electrode, and while having an effect of preventing a short circuit in a direction different from that between the counter electrodes, an improvement in conduction reliability can be expected.

[0033] Examples of the method for measuring the glass transition temperature include the following methods.

[0034] Using a differential scanning calorimeter (for example, "STAR SYSTEM" manufactured by METTLER TOLEDO), 0.04 to 0.06 g of a sample is heated up to 200 °C, and then cooled from that temperature to 25 °C at a cooling rate of 5 °C / min. Subsequently, the sample is heated at a heating rate of 5 °C / min, and the heat quantity is measured. When a peak is observed, the temperature of the peak is taken. When no peak is observed but a step is observed, the temperature at the intersection of the tangent line indicating the maximum slope of the curve at the step portion and the extension of the baseline on the high-temperature side of the step is taken as the glass transition temperature.

[0035] In the present invention, "not having a glass transition temperature" means that neither a peak nor a step is observed when differential scanning calorimetry is performed by the above method.

[0036] As the insulating fine particles in the present invention, it is preferable that at least the surface layer thereof is made of a polymer containing a crosslinkable monomer component. Since the surface layer of the insulating fine particles is a polymer containing a crosslinkable monomer component, insulating fine particles having no glass transition temperature and having a hardness that can withstand the high temperature during thermocompression bonding can be obtained. Further, as the insulating fine particles in the present invention, it is preferable that the core material portion thereof is made of a polymer obtained by polymerizing a non-crosslinkable monomer component. Since the core material portion of the insulating fine particles is a polymer obtained by polymerizing a non-crosslinkable monomer component, it becomes easier to obtain insulating fine particles that are spherical and have a uniform particle size. In addition, as long as the core material portion can maintain a spherical shape, from the viewpoint of maintaining the strength of the insulating fine particles, it may be a polymer obtained by polymerizing a crosslinkable monomer component in an arbitrary amount in addition to the non-crosslinkable monomer component. From the above, from the viewpoint of obtaining insulating fine particles having the range of sphericity described below and not having a glass transition temperature, in particular, a spherical core material portion made of a polymer obtained by polymerizing a non-crosslinkable monomer component and a surface layer portion made of a polymer containing a crosslinkable monomer component, and the whole particle does not have a glass transition temperature is preferable.

[0037] Examples of the crosslinkable monomer component constituting the insulating fine particles in the present invention include aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; allyl methacrylate, triacrylic formal, triallyl isocyanate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, trimethylolpropane trimethacrylate, glycerin dimethacrylate, dimethylol-tricyclodecane diacrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, neopentyl glycol acrylate benzoate, trimethylolpropane acrylate benzoate, 2-hydroxy-3-acryloyloxypropyl methacrylate, hydroxypivalic acid neopentyl glycol diacrylate, ditrimethylolpropane tetraacrylate, 2-butyl-2-ethyl-1,3-propanediol diacrylate, and other compounds having two or more polymerizable ethylenic unsaturated bonds such as polyfunctional acrylate compounds. These may be used alone or in combination of two or more. When the insulating fine particles contain a plurality of types of crosslinkable monomer components, the mode of existence of the structural units of the crosslinkable monomer components in the polymer may be random, alternating, or block as a copolymer.

[0038] In the present invention, the crosslinkable monomer component is preferably at least one selected from divinylbenzene, allyl methacrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, and 1,10-decanediol di(meth)acrylate. By having a polymer containing such a crosslinkable monomer component on at least the surface layer of the insulating fine particles, not only can the short-circuit prevention effect in a direction different from between the counter electrodes be obtained, but also the insulating fine particles can be efficiently removed without remaining between the conductive layer and the electrode during thermocompression bonding.

[0039] In the polymer constituting the insulating fine particles according to the present invention, the blending amount of the crosslinkable monomer component in all the constituent units is preferably more than 20% by mass and 95% by mass or less, and more preferably 21% by mass or more and 80% by mass or less. By blending the crosslinkable monomer component within this range, insulating fine particles having no glass transition temperature and having the desired hardness during thermocompression bonding can be obtained.

[0040] The insulating fine particles in the present invention preferably further contain a compound containing a functional group having a charge. Thereby, the coating particles of the present invention have high adhesion between the conductive particles and the insulating fine particles. Therefore, the coating particles of the present invention are likely to exhibit a short-circuit prevention effect in a direction different from between the counter electrodes, and an improvement in insulation in that direction can be expected. In particular, it is preferable that the surface layer of the insulating fine particles is a polymer containing a monomer component having a functional group having a charge.

[0041] Examples of the functional group having a charge include onium-based functional groups such as a phosphonium group, an ammonium group, and a sulfonium group, and an amino group. Among these, from the viewpoint of enhancing the adhesion between the conductive particles and the insulating fine particles and forming coating particles having both high insulation and high conduction reliability, an ammonium group or a phosphonium group is preferable, and a phosphonium group is more preferable.

[0042] Examples of the functional group having a charge preferably include those represented by the following general formula (1).

[0043] [Chemical formula] (In the formula, X is a phosphorus atom, a nitrogen atom, or a sulfur atom, R may be the same or different, and is a hydrogen atom, a linear, branched or cyclic alkyl group, or an aryl group. n is 1 when X is a nitrogen atom or a phosphorus atom, and 0 when X is a sulfur atom. * represents a bond.) Examples of the counter ion for the cationic group include, for example, halide ions. Examples of the halide ion include Cl - , F - , Br - , I - .

[0044] In formula (1), examples of the linear alkyl group represented by R include linear alkyl groups having 1 to 20 carbon atoms, specifically, methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, n-nonadecyl group, n-icosyl group, and the like.

[0045] In formula (1), examples of the branched alkyl group represented by R include branched alkyl groups having 3 to 8 carbon atoms, specifically, isopropyl group, isobutyl group, s-butyl group, t-butyl group, isopentyl group, s-pentyl group, t-pentyl group, isohexyl group, s-hexyl group, t-hexyl group, ethylhexyl group, and the like.

[0046] In formula (1), examples of the cyclic alkyl group represented by R include cycloalkyl groups such as cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, and cyclooctadecyl group.

[0047] In formula (1), examples of the aryl group represented by R include phenyl group, benzyl group, tolyl group, o-xylyl group, and the like.

[0048] In general formula (1), from the viewpoints of enhancing the adhesion between the conductive particles and the insulating fine particles and facilitating the detachment of the insulating fine particles from the conductive particles to ensure conductivity when thermocompression bonding occurs inside the anisotropic conductive film, R is preferably an alkyl group having 1 to 12 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms, and most preferably an alkyl group having 1 to 8 carbon atoms. Also, from the viewpoint of facilitating the proximity and adhesion of the insulating fine particles to the conductive particles, it is also preferable that R is a linear alkyl group.

[0049] Examples of the monomer component having a functional group with an electric charge include compounds having a functional group with an electric charge and a polymerizable ethylenically unsaturated bond. Specifically, polymerizable compounds having an ethylenically unsaturated bond with an onium-based functional group include compounds having an ammonium group such as N,N-dimethylaminoethyl methacrylate, N,N-dimethylaminopropyl acrylamide, and N,N,N-trimethyl-N-2-methacryloyloxyethylammonium chloride; compounds having a sulfonium group such as phenyl dimethyl sulfonium methyl sulfate methacrylate; 4-(vinylbenzyl)triethylphosphonium chloride, 4-(vinylbenzyl)trimethylphosphonium chloride, 4-(vinylbenzyl)tributylphosphonium chloride, 4-(vinylbenzyl)trioctylphosphonium chloride, 4-(vinylbenzyl)triphenylphosphonium chloride, 2-(methacryloyloxyethyl)trimethylphosphonium chloride, 2-(methacryloyloxyethyl)triethylphosphonium chloride, 2-(methacryloyloxyethyl)tributylphosphonium chloride, 2-(methacryloyloxyethyl)trioctylphosphonium chloride, 2-(methacryloyloxyethyl)triphenylphosphonium chloride, and other compounds having a phosphonium group.

[0050] In the present invention, it is preferable that the monomer component having a functional group with an electric charge is at least one selected from the compounds having an ammonium group and the compounds having a phosphonium group. By having a polymer containing such a monomer component having a functional group with an electric charge on at least the surface layer of the insulating fine particles, the adhesion between the conductive particles and the insulating fine particles can be enhanced, and the insulating fine particles can be easily arranged regularly, so that coated particles having both high levels of insulation and conduction reliability can be obtained.

[0051] In the polymer constituting the insulating fine particles according to the present invention, the proportion of the constituent units to which functional groups having charges are bonded in all the constituent units is preferably 0.01 mol% or more and 5.0 mol% or less, and more preferably 0.02 mol% or more and 2.0 mol% or less. Further, as one of the monomer components constituting the surface layer of the insulating fine particles, it is preferable to use a monomer having a functional group having a charge.

[0052] The insulating fine particles according to the present invention are polymers containing a crosslinkable monomer component at least on their surface layers. However, substances constituting parts other than the surface layer, for example, the inside of the insulating fine particles, can be used without particular limitation whether they are inorganic substances or organic substances. When using inorganic substances, metal particles such as gold, silver, copper, nickel, palladium, solder, alloys, glass, ceramics, silica, metal or non-metal oxides (including hydrates), metal silicates including aluminosilicates, metal carbides, metal nitrides, metal carbonates, metal sulfates, metal phosphates, metal sulfides, metal acid salts, metal halides, and carbon can be mentioned. On the other hand, when using organic substances, for example, natural fibers, natural resins, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polybutene, polyamide, polyacrylate ester, polyacrylonitrile, polyacetal, ionomer, thermoplastic resins such as polyester, alkyd resins, phenol resins, urea resins, benzoguanamine resins, melamine resins, xylene resins, silicone resins, epoxy resins, diallyl phthalate resins, etc. can be mentioned. These may be used alone or in combination of two or more. Among these, it is preferable to be made of a resin material in terms of having a smaller specific gravity than metals, being difficult to sediment, and having excellent dispersion stability.

[0053] The resin material that constitutes the portion other than the surface layer of the insulating fine particles is preferably a polymer of a polymerizable compound having an ethylenically unsaturated bond. Examples of the polymerizable compound having an ethylenically unsaturated bond include styrenes, olefins, esters, α,β-unsaturated carboxylic acids, amides, nitriles, and the like. Examples of styrenes include nuclear-substituted styrenes such as styrene, o,m,p-methylstyrene, dimethylstyrene, ethylstyrene, chlorostyrene, and styrene derivatives such as α-methylstyrene, α-chlorostyrene, and β-chlorostyrene. Examples of olefins include ethylene, propylene, and the like. Examples of esters include vinyl esters such as vinyl acetate, vinyl propionate, and vinyl benzoate, and esters of (meth)acrylic acid such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and phenyl (meth)acrylate. Examples of α,β-unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, maleic acid, and the like. Salts of these α,β-unsaturated carboxylic acids are also included in α,β-unsaturated carboxylic acids. Examples of amides include acrylamide, methacrylamide, and the like. Examples of nitriles include acrylonitrile, and the like. These may be further substituted, and examples of the substituents include phosphonium group, amino group, quaternary ammonium group, amide group, sulfonium group, sulfonic acid group, thiol group, carboxyl group, phosphate group, cyano group, aldehyde group, ester group, carbonyl group, and the like. These monomers can be used alone or in combination of two or more. In particular, a polymer containing at least one non-crosslinkable monomer component selected from styrenes, esters, and nitriles is preferable in terms of high polymerization rate and easy formation into a spherical shape. When the polymer constituting the resin material has a plurality of types of constitutional units, the existence modes of these constitutional units in the polymer may be random, alternating, or block. The polymer constituting the resin material may be crosslinked or non-crosslinked.In the present invention, from the viewpoint of facilitating the obtaining of spherical insulating fine particles, it is preferable that the resin material constituting the portion other than the surface layer, that is, the core material portion, is composed of a polymer obtained by polymerizing a non-crosslinkable monomer component.

[0054] The average particle diameter (D) of the insulating fine particles is preferably 10 nm or more and 3,000 nm or less, more preferably 15 nm or more and 2,000 nm or less. When the average particle diameter of the insulating fine particles is within the above range, the obtained coated particles can easily ensure conduction between the counter electrodes without causing a short circuit in a direction different from that between the counter electrodes. In the present invention, the average particle diameter of the insulating fine particles is a value measured in an observation using a scanning electron microscope, and specifically, it is measured by the method described in the examples below.

[0055] The particle size distribution of the insulating fine particles measured by the above-described method has a width. Generally, the width of the particle size distribution of the powder is represented by the coefficient of variation (hereinafter also referred to as "C.V.") shown by the following calculation formula (1).

[0056] C.V. (%) = (standard deviation / average particle diameter) × 100 ··· (1) A large C.V. indicates that the particle size distribution has a width, while a small C.V. indicates that the particle size distribution is sharp. For the coated particles of the present embodiment, it is desirable to use insulating fine particles having a C.V. of preferably 0.1% or more and 20% or less, more preferably 0.5% or more and 15% or less, and most preferably 1% or more and 10% or less. When the C.V. is within this range, there is an advantage that the thickness of the coating layer by the insulating fine particles can be made uniform.

[0057] The sphericity of the insulating fine particles is 0.90 or more. In the present invention, the sphericity means the value obtained by dividing the minor axis of the insulating fine particles by the major axis. The sphericity can be measured, for example, at a magnification at which the number of insulating fine particles contained in one visual field is about 50 to 100, using a scanning electron microscope, and the arithmetic mean value based on the number can be calculated. The sphericity is preferably 0.92 or more, more preferably 0.94 or more, and still more preferably 0.95 or more. The upper limit of the sphericity is not particularly limited, but is usually about 0.99. When the sphericity is within this range, the insulating fine particles can be efficiently excluded from between the conductive layer and the electrode during thermocompression bonding, and an improvement in conduction reliability can be expected.

[0058] Next, a suitable manufacturing method for the coated particles of the present embodiment will be described.

[0059] This manufacturing method includes a first step of polymerizing a non-crosslinkable monomer component to obtain an insulating fine particle precursor, a second step of polymerizing a polymerizable compound containing a crosslinkable monomer component in the presence of the insulating fine particle precursor to obtain insulating fine particles, and a third step of mixing a dispersion liquid containing the insulating fine particles and the conductive particles to attach the insulating fine particles to the surface of the conductive particles.

[0060] (First step) The insulating fine particle precursor according to the manufacturing method of the present invention is a polymer obtained by polymerizing a non-crosslinkable monomer component. The non-crosslinkable monomer component is a resin material that constitutes a portion other than the surface layer of the insulating fine particles described above, and examples thereof include polymerizable compounds having an ethylenically unsaturated bond. In particular, the non-crosslinkable monomer component is preferably at least one selected from styrene, o-, m-, or p-methylstyrene, dimethylstyrene, ethylstyrene, chlorostyrene, vinyl acetate, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and phenyl (meth)acrylate. When a plurality of non-crosslinkable monomer components are used, examples of the preferable composition ratio of the polymerizable compounds include those that give the preferable constitutional units and their preferable quantitative ratios of the polymer constituting the insulating fine particle precursor described above.

[0061] In the first step, a polymerizable compound containing a monomer component having a functional group with a charge in addition to the crosslinkable monomer component may be polymerized. Examples of the monomer component having a functional group with a charge include the monomer component having a functional group with a charge that constitutes the above-described insulating fine particles.

[0062] Examples of the polymerization method include emulsion polymerization, soap-free emulsion polymerization, dispersion polymerization, suspension polymerization, etc., and any of them may be used. However, soap-free emulsion polymerization is preferable because it has the advantage of being able to produce monodisperse fine particles without using a surfactant. In the case of soap-free emulsion polymerization, a water-soluble initiator is used as the polymerization initiator. The polymerization is preferably carried out under an inert atmosphere such as nitrogen or argon.

[0063] From the viewpoint of obtaining particles in which the insulating fine particle precursor is spherical and has a uniform particle diameter, the polymerization time is preferably 0.3 hours or more and 20 hours or less, particularly preferably 0.5 hours or more and 12 hours or less.

[0064] Thus, an insulating fine particle precursor is obtained.

[0065] (Second step) In the second step, in the presence of the insulating fine particle precursor obtained in the first step, a polymerizable compound containing a crosslinkable monomer component is polymerized to obtain insulating fine particles. Examples of the crosslinkable monomer component include the crosslinkable monomer component that constitutes the above-described insulating fine particles, and particularly preferably at least one selected from divinylbenzene, allyl methacrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, and 1,10-decanediol di(meth)acrylate. When a plurality of crosslinkable monomer components are used, examples of the preferable composition ratio of the polymerizable compound include those that give the preferable constitutional units and their preferable quantitative ratios of the polymer that constitutes the above-described insulating fine particles.

[0066] In the second step, a polymerizable compound containing a monomer component having a functional group with an electric charge in addition to the crosslinkable monomer component may be polymerized. Examples of the monomer component having a functional group with an electric charge include monomer components having a functional group with an electric charge that constitutes the above-described insulating fine particles.

[0067] Examples of the polymerization method include the same method as in the first step, such as emulsion polymerization, soap-free emulsion polymerization, dispersion polymerization, and suspension polymerization. In particular, soap-free emulsion polymerization is preferable because it has the advantage of being able to produce monodisperse fine particles without using a surfactant. The polymerization is preferably carried out in an inert atmosphere such as nitrogen or argon.

[0068] From the viewpoint of obtaining insulating fine particles that are spherical and have a uniform particle diameter, the polymerization time is preferably 0.3 hours or more and 20 hours or less, particularly preferably 0.5 hours or more and 12 hours or less.

[0069] Thus, insulating fine particles are obtained.

[0070] (Third step) Next, the insulating fine particles and the conductive particles are mixed to attach the insulating fine particles to the surface of the conductive particles. The mixing of the insulating fine particles and the conductive particles is preferably carried out in a liquid medium. Examples of the liquid medium include water, organic solvents, and mixtures thereof, with water being preferred.

[0071] When the insulating fine particles and the conductive particles are mixed in a liquid medium, it is preferable for the dispersion liquid composed of these particles and the liquid medium to contain an inorganic salt, an organic salt, or an organic acid, from the viewpoint of easily obtaining coated particles with a coating rate of a certain level or more. As the inorganic salt, organic salt, or organic acid, those that dissociate anions are preferably used, and as this anion, Cl - , F - , Br - , I - , SO4 2- , CO3 2- , NO3 - , COO - , RCOO -(wherein R is an organic group) and the like are preferred. As the inorganic salts, for example, NaCl, KCl, LiCl, MgCl2, BaCl2, NaF, KF, LiF, MgF2, BaF2, NaBr, KBr, LiBr, MgBr2, BaBr2, NaI, KI, LiI, MgI2, BaI2, Na2SO4, K2SO4, Li2SO4, MgSO4, Na2CO3, NaHCO3, K2CO3, KHCO3, Li2CO3, LiHCO3, MgCO3, NaNO3, KNO3, LiNO3, Mg(NO3)2, Ba(NO3)2, etc. can be used. As the organic salts, sodium succinate, sodium oxalate, sodium acetate, sodium citrate, sodium malonate, sodium tartrate, sodium fumarate, sodium maleate, etc. can be used. As the organic acids, amino acids such as glycine, succinic acid, oxalic acid, acetic acid, citric acid, tartaric acid, malonic acid, fumaric acid, maleic acid, etc. can be used.

[0072] The preferred concentrations of the inorganic salts, organic salts and organic acids vary depending on the coating area occupied by the insulating fine particles on the surface area of the conductive particles. However, in a dispersion containing insulating fine particles and conductive particles, for example, when the concentration is 5 mmol / L or more and 100 mmol / L or less, it has a suitable coating rate and is preferred because it is easy to obtain coated particles with a single layer of insulating fine particles. From this viewpoint, the concentration of the inorganic salts, organic salts and organic acids in the dispersion is more preferably 7 mmol / L or more and 90 mmol / L or less, and particularly preferably 10 mmol / L or more and 80 mmol / L or less.

[0073] When mixing the insulating fine particles and the conductive particles in a liquid medium, the dispersion containing the insulating fine particles and the conductive particles may be mixed, the dispersion containing the conductive particles and the insulating fine particles may be mixed, or the insulating fine particles and the conductive particles may be respectively added to the liquid medium, or the dispersion medium containing the insulating fine particles and the dispersion medium containing the conductive particles may be mixed. In the dispersion containing the conductive particles and the insulating fine particles, the conductive particles are preferably contained at 100 ppm or more and 100,000 ppm or less on a mass basis, and more preferably 500 ppm or more and 80,000 ppm or less.

[0074] In the dispersion liquid containing conductive particles and insulating fine particles, it is preferable that the insulating fine particles are contained in an amount of 10 ppm or more and 50,000 ppm or less based on mass, and more preferably 250 ppm or more and 30,000 ppm or less.

[0075] The temperature of the dispersion liquid containing conductive particles and insulating fine particles is generally preferably 20°C or higher and 100°C or lower, and particularly preferably 40°C or higher and 90°C or lower, from the viewpoint that it is easy to obtain coated particles with constant quality. Within this range, the insulating fine particles adhere to the conductive particles while maintaining their shape, and it is easy to obtain a suitable contact area between the insulating fine particles and the conductive particles.

[0076] In the dispersion liquid after mixing the conductive particles, the time for the insulating fine particles to adhere to the conductive particles is preferably 0.1 hour or more and 24 hours or less. During this time, it is preferable to stir the dispersion liquid. Subsequently, the solid content of the dispersion liquid is washed and dried as necessary, and coated particles in which the insulating fine particles are adhered to the surface of the conductive particles are obtained.

[0077] The coated particles obtained as described above utilize the conductivity of the conductive particles and the insulation between the coated particles due to the advantages of the insulating fine particles having no glass transition temperature and the connectivity between the opposing electrodes, and are suitably used as conductive materials such as conductive adhesives, anisotropic conductive films, and anisotropic conductive adhesives.

Examples

[0078] Hereinafter, the present invention will be described with reference to examples. However, the scope of the present invention is not limited to these examples. The characteristics in the examples were measured by the following methods. (1) Average particle diameter From the scanning electron microscope (SEM) photograph (magnification 100,000 times) of the measurement target, 200 particles were arbitrarily extracted, their particle diameters were measured, and the average value was taken as the average particle diameter. The definition of the average particle diameter is as described above. (2) C.V. (Coefficient of variation) It was determined by the following formula from the measurement of the average particle diameter.

[0079] C.V. (%) = (standard deviation / average particle diameter) × 100 (3) Glass transition temperature Using a differential scanning calorimeter (STAR SYSTEM manufactured by METTLER TOLEDO), the heat change from 25°C to 200°C was measured under a nitrogen atmosphere at a heating and cooling rate of 5°C / min according to the above procedure. (4) Sphericity From the scanning electron microscope (SEM) photograph (magnification 100,000 times) of the measurement object, 200 particles were randomly extracted, their minor axis and major axis were measured, the value obtained by dividing the minor axis of each particle by the major axis was calculated, and the average value was taken as the sphericity. (Example 1) [Production of phosphonium-based insulating fine particles] 1200 mL of pure water was added to a 2000 mL four-necked flask equipped with a stirring blade with a length of 60 mm. Then, 288 mmol of styrene monomer (manufactured by Kanto Chemical Co., Inc.), 63.6 mmol of n-butyl acrylate (manufactured by Kanto Chemical Co., Inc.), and 5.0 mmol of 2,2'-azobis(2-methylpropionamidine) dihydrochloride (manufactured by Wako Pure Chemical Industries, Ltd., V-50) as a polymerization initiator were added. After purging with nitrogen for 15 minutes to expel dissolved oxygen, the temperature was raised to 65°C and maintained for 6 hours to allow the polymerization reaction to proceed.

[0080] Then, 108 mmol of divinylbenzene monomer (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.) and 2.16 mmol of 4-(vinylbenzyl)triethylphosphonium chloride (manufactured by Nippon Chemical Industry Co., Ltd.) were added to the reaction system, and the reaction was terminated by maintaining the temperature at 65°C for 10 hours.

[0081] The dispersion of the particles after overlapping was passed through a SUS sieve with an opening of 150 μm to remove aggregates. The dispersion from which the aggregates were removed was centrifuged at 20,000 rpm for 20 minutes using a centrifuge (manufactured by Hitachi Koki Co., Ltd., CR-21N) to sediment the particles, and the supernatant was removed. Pure water was added to the obtained solid matter for washing to obtain spherical particles. The characteristics of the obtained particles are shown in Table 1. An SEM photograph of the obtained insulating particles is shown in Figure 1. Also, the results of measuring the glass transition temperature are shown in Figure 2. [Production of Insulating Particle-Coated Conductive Particles] Ni-plated particles (manufactured by Nippon Chemical Industry Co., Ltd.) with an average particle diameter of 3 μm and having a nickel film with a thickness of 0.125 μm on the surface of spherical resin particles were prepared. The resin particles were composed of a crosslinkable acrylic resin and had a glass transition temperature of 120°C. 100 mL of pure water was added to 5.0 g of the above Ni-plated particles and stirred to obtain a dispersion of Ni-plated particles. 10 mL of an aqueous solution of 1% by mass benzotriazole was added to this dispersion and stirred for 5 minutes for surface treatment. Then, it was filtered through a membrane filter with an opening of 2.0 μm to recover Ni-plated particles having a benzotriazole layer on the surface. After washing the recovered Ni-plated particles with pure water, 100 mL of pure water was added to obtain a dispersion of Ni-plated particles having a benzotriazole layer on the surface. The insulating particles obtained above and Na2SO4 were added to this dispersion, and this was stirred at 40°C for 30 minutes. After the addition of the insulating particles and Na2SO4, the solid content concentration of the insulating particles in the dispersion was 10,000 ppm on a mass basis, and the concentration of Na2SO4 was 5 mmol / L. After removing the supernatant, it was washed with pure water and then vacuum-dried at 50°C to obtain insulating particle-coated conductive particles. An SEM photograph of the obtained coated particles is shown in Figure 3. (Example 2) [Production of Ammonium-Based Insulating Particles] 1200 mL of pure water was added to a 2000 mL four-necked flask equipped with a stirring blade with a length of 60 mm. Then, 288 mmol of styrene monomer (manufactured by Kanto Chemical Co., Inc.), 63.6 mmol of n-butyl acrylate (manufactured by Kanto Chemical Co., Inc.), and 5.0 mmol of 2,2'-azobis(2-methylpropionamidine) dihydrochloride (manufactured by Wako Pure Chemical Industries, Ltd., V-50) as a polymerization initiator were added. After purging with nitrogen for 15 minutes to expel dissolved oxygen, the temperature was raised to 65 °C and maintained for 6 hours to allow the polymerization reaction to proceed.

[0082] Thereafter, 108 mmol of divinylbenzene monomer (manufactured by Nippon Steel & Sumitomo Metal Corporation) and 2.0 mmol of 4-(vinylbenzyl)triethylammonium chloride (manufactured by Nippon Chemical Industry Co., Ltd.) were added to the reaction system, and the reaction was terminated by maintaining the temperature at 65 °C for 10 hours.

[0083] The dispersion of the polymerized fine particles was passed through a SUS sieve with an opening of 150 μm to remove aggregates. The dispersion from which the aggregates were removed was centrifuged at 20,000 rpm for 20 minutes using a centrifuge (manufactured by Hitachi Koki Co., Ltd., CR-21N) to precipitate the fine particles, and the supernatant was removed. Pure water was added to the obtained solid matter for washing to obtain spherical fine particles. Each property of the obtained fine particles is shown in Table 1. An SEM photograph of the obtained insulating fine particles is shown in Figure 4. Also, the results of measuring the glass transition temperature are shown in Figure 5. [Production of Insulating Fine Particle-Coated Conductive Particles] The insulating fine particle-coated conductive particles were obtained in the same manner as in Example 1. (Comparative Example 1) [Production of Phosphonium-Based Insulating Fine Particles] 1200 mL of pure water was added to a 2000 mL four-necked flask equipped with a stirring blade with a length of 60 mm. Then, 288 mmol of styrene monomer (manufactured by Kanto Chemical Co., Inc.), 63.6 mmol of n-butyl acrylate (manufactured by Kanto Chemical Co., Inc.), 108 mmol of divinylbenzene monomer (manufactured by Nippon Steel & Sumitomo Metal Corporation), 1.44 mmol of 4-(vinylbenzyl)triethylphosphonium chloride (manufactured by Nippon Chemical Industry Co., Ltd.), and 5.0 mmol of 2,2’-azobis(2-methylpropionamidine) dihydrochloride (manufactured by Wako Pure Chemical Industries, Ltd., V-50) as a polymerization initiator were added. After purging with nitrogen for 15 minutes to expel dissolved oxygen, the temperature was raised to 65°C and maintained for 8 hours to allow the polymerization reaction to proceed. The dispersion of the polymerized fine particles was passed through a SUS sieve with an opening of 150 μm to remove aggregates. The dispersion from which aggregates were removed was centrifuged at 20,000 rpm for 20 minutes using a centrifuge (manufactured by Hitachi Koki Co., Ltd., CR-21N) to precipitate the fine particles, and the supernatant was removed. Pure water was added to the obtained solid matter for washing to obtain spherical fine particles. Each property of the obtained fine particles is shown in Table 1. An SEM photograph of the obtained insulating fine particles is shown in Figure 6. Also, the results of measuring the glass transition temperature are shown in Figure 7. [Production of Insulating Fine Particle-Coated Conductive Particles] Nickel-plated particles (manufactured by Nippon Chemical Industry Co., Ltd.) with an average particle diameter of 3 μm and having a nickel film with a thickness of 0.125 μm on the surface of spherical resin particles were prepared. The resin particles were composed of a crosslinkable acrylic resin and had a glass transition temperature of 120°C. 100 mL of pure water was added to 5.0 g of the above nickel-plated particles and stirred to obtain a dispersion of nickel-plated particles. 10 mL of an aqueous solution of 1 mass% benzotriazole was added to this dispersion and stirred for 5 minutes for surface treatment. Then, it was filtered through a membrane filter with a pore size of 2.0 μm to recover nickel-plated particles having a benzotriazole layer on the surface. After washing the recovered nickel-plated particles with pure water, 100 mL of pure water was added to obtain a dispersion of nickel-plated particles having a benzotriazole layer on the surface. To this dispersion, the insulating fine particles obtained above and Na2SO4 were added, and this was stirred at 40°C for 30 minutes. After the addition of the insulating fine particles and Na2SO4, the solid content concentration of the insulating fine particles in the dispersion was 10,000 ppm on a mass basis, and the concentration of Na2SO4 was 5 mmol / L. After removing the supernatant, it was washed with pure water and then vacuum dried at 50°C to obtain insulating fine particle-coated conductive particles. (Comparative Example 2) [Production of Ammonium-Based Insulating Fine Particles] 1200 mL of pure water was added to a 2000 mL four-necked flask equipped with a stirring blade with a length of 60 mm. Then, 288 mmol of styrene monomer (manufactured by Kanto Chemical Co., Inc.), 63.6 mmol of n-butyl acrylate (manufactured by Kanto Chemical Co., Inc.), 108 mmol of divinylbenzene monomer (manufactured by Nippon Steel & Sumitomo Metal Corporation), 2.0 mmol of 4-(vinylbenzyl)triethylammonium chloride (manufactured by Nippon Chemical Industry Co., Ltd.), and 5.0 mmol of 2,2'-azobis(2-methylpropionamidine) dihydrochloride (manufactured by Wako Pure Chemical Industries, Ltd., V-50) as a polymerization initiator were added. After purging with nitrogen for 15 minutes to expel dissolved oxygen, the temperature was raised to 65°C and maintained for 8 hours to allow the polymerization reaction to proceed. The dispersion of the polymerized fine particles was passed through a SUS sieve with an opening of 150 μm to remove aggregates. The dispersion from which the aggregates were removed was centrifuged at 20,000 rpm for 20 minutes using a centrifuge (manufactured by Hitachi Koki Co., Ltd., CR-21N) to precipitate the fine particles, and the supernatant was removed. Pure water was added to the obtained solid matter for washing to obtain spherical fine particles. The characteristics of the obtained fine particles are shown in Table 1. The SEM photograph of the obtained insulating fine particles is shown in Figure 8. Also, the results of measuring the glass transition temperature are shown in Figure 9. [Production of Insulating Fine Particle-Coated Conductive Particles] The same method as in Comparative Example 1 was carried out to obtain insulating fine particle-coated conductive particles. (Comparative Example 3) [Production of Phosphonium-Based Insulating Fine Particles] 1200 mL of pure water was added to a 2000 mL four-necked flask equipped with a stirring blade with a length of 60 mm. Then, 360 mmol of styrene monomer (manufactured by Kanto Chemical Co., Inc.), 63.6 mmol of n-butyl acrylate (manufactured by Kanto Chemical Co., Inc.), 1.44 mmol of 4-(vinylbenzyl)triethylphosphonium chloride (manufactured by Nippon Chemical Industry Co., Ltd.), and 5.0 mmol of 2,2'-azobis(2-methylpropionamidine) dihydrochloride (manufactured by Wako Pure Chemical Industries, Ltd., V-50) as a polymerization initiator were added. After purging with nitrogen for 15 minutes to expel dissolved oxygen, the temperature was raised to 65°C and maintained for 8 hours to allow the polymerization reaction to proceed. The dispersion of the polymerized fine particles was passed through a SUS sieve with an opening size of 150 μm to remove aggregates. The dispersion from which aggregates were removed was centrifuged at 20,000 rpm for 20 minutes using a centrifuge (manufactured by Hitachi Koki Co., Ltd., CR-21N) to precipitate the fine particles, and the supernatant was removed. Pure water was added to the obtained solid matter for washing to obtain spherical fine particles. The characteristics of the obtained fine particles are shown in Table 1. The SEM photograph of the obtained insulating fine particles is shown in Figure 10. Also, the results of measuring the glass transition temperature are shown in Figure 11. [Production of Insulating Fine Particle-Coated Conductive Particles] The same method as in Comparative Example 1 was carried out to obtain insulating fine particle-coated conductive particles.

[0084] [Table 1] (Evaluation of Conductivity and Insulation) [Evaluation of Conductivity] An insulating adhesive prepared by mixing 100 parts by mass of an epoxy resin, 150 parts by mass of a curing agent, and 70 parts by mass of toluene was mixed with 15 parts by mass of the coated particles obtained in the examples and comparative examples to obtain an insulating paste. This paste was applied onto a silicone-treated polyester film using a bar coater, and then the paste was dried to form a thin film on the film. The obtained thin film-forming film was disposed between a glass substrate with aluminum vapor-deposited on the entire surface and a polyimide film substrate on which a copper pattern was formed at a pitch of 50 μm, and electrical connection was performed. By measuring the conduction resistance between these substrates, the conductivity of the coated particles was evaluated at room temperature (25 °C · 50% RH). It can be evaluated that the lower the resistance value, the higher the conductivity of the coated particles. For the evaluation of the conductivity of the coated particles, those with a resistance value of less than 2 Ω were regarded as "very good" (indicated by the symbol "○" in Table 2), those with a resistance value of 2 Ω or more and less than 5 Ω were regarded as "good" (indicated by the symbol "△" in Table 2), and those with a resistance value of 5 Ω or more were regarded as "poor" (indicated by the symbol "×" in Table 2). The results are shown in Table 2. <Evaluation of Insulation> Using a micro compression tester MCTM-500 (manufactured by Shimadzu Corporation), 20 coated particles were targeted, and the coated particles of the examples and comparative examples were compressed under the condition of a loading rate of 0.5 mN / second, and the insulation of the coated particles was evaluated by measuring the compression displacement until a resistance value was detected. It can be evaluated that the larger the compression displacement until a resistance value is detected, the higher the insulation of the coated particles. For the evaluation of the insulation of the coated particles, those with an arithmetic mean value of the compression displacement until a resistance value is detected of 10% or more were regarded as "very good" (indicated by the symbol "○" in Table 2), those with an arithmetic mean value of the compression displacement exceeding 3% and less than 10% were regarded as "good" (indicated by the symbol "△" in Table 2), and those with an arithmetic mean value of the compression displacement of 3% or less were regarded as "poor" (indicated by the symbol "×" in Table 2). The results are shown in Table 2.

[0085]

Table 2

Industrial Applicability

[0086] Since the coated particles of the present invention are coated particles obtained by coating insulating fine particles having a spherical shape and no glass transition temperature with a uniform particle diameter, they can have high conduction reliability and insulation reliability.

Claims

1. Coated particles having conductive particles with a metal film formed on the surface of a core material and insulating fine particles covering the conductive particles, wherein the insulating fine particles are insulating fine particles having no glass transition temperature and a sphericity of 0.90 or more.

2. The coated particles according to claim 1, wherein a surface layer of the insulating fine particles is a polymer containing a crosslinkable monomer component.

3. The coated particles according to claim 2, wherein the crosslinkable monomer component is at least one selected from divinylbenzene, allyl methacrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, and 1,10-decanediol di(meth)acrylate.

4. The coated particles according to any one of claims 1 to 3, wherein a surface layer of the insulating fine particles is a polymer containing a monomer component having a functional group with an electric charge.

5. The coated particles according to claim 4, wherein the functional group is an ammonium group or a phosphonium group.

6. The coated particles according to any one of claims 1 to 5, wherein a coefficient of variation (C.V.) of the particle diameter of the insulating fine particles is 0.1% or more and 20% or less.

7. The coated particles according to any one of claims 1 to 6, wherein the metal film is a film composed of at least one selected from nickel, gold, nickel alloy, and gold alloy.

8. The coated particles according to any one of claims 1 to 7, wherein the conductive particles have a plurality of protrusions on the surface.

9. A conductive material containing the coated particles according to any one of claims 1 to 8 and an insulating resin.

10. A method for producing coated particles having conductive particles with a metal film formed on the surface of a core material and insulating fine particles covering the conductive particles, a first step of polymerizing a non-crosslinkable monomer component to obtain an insulating fine particle precursor, a second step of polymerizing a polymerizable compound containing a crosslinkable monomer component in the presence of the insulating fine particle precursor to obtain insulating fine particles, a third step of mixing a dispersion containing the insulating fine particles and the conductive particles to attach the insulating fine particles to the surface of the conductive particles, The method for producing coated particles having the above steps.

11. The method for producing coated particles according to claim 10, wherein the non-crosslinkable monomer component is at least one selected from styrene, o-, m- or p-methylstyrene, dimethylstyrene, ethylstyrene, chlorostyrene, vinyl acetate, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and phenyl (meth)acrylate.

12. The method for producing coated particles according to claim 10 or 11, wherein the crosslinkable monomer component is at least one selected from divinylbenzene, allyl methacrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, and 1,10-decanediol di(meth)acrylate.

13. The method for producing coated particles according to any one of claims 10 to 12, wherein after obtaining the insulating fine particle precursor in 0.3 hours or more and 20 hours or less by the first step, the second step is carried out.

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