JP7585016B2 - Coated particles and conductive materials containing same - Google Patents

Description

The present invention relates to coated particles in which conductive particles are coated with an insulating layer and to a conductive material containing the same.

2. Description of the Related Art Conductive particles, which are resin particles having metals such as nickel and gold formed on the surfaces thereof, are used as conductive materials such as conductive adhesives, anisotropic conductive films, and anisotropic conductive adhesives.
In recent years, with the further miniaturization of electronic devices, the circuit width and pitch of electronic circuits are becoming smaller and smaller. Accordingly, conductive particles with small particle diameters are required for use in the above-mentioned conductive adhesives, anisotropic conductive films, anisotropic conductive adhesives, etc. When such small particle diameter conductive particles are used, the amount of conductive particles must be increased to improve the connectivity. However, when the amount of conductive particles is increased, a short circuit occurs due to conduction in an unintended direction, i.e., conduction in a direction different from that between the opposing electrodes, and it is difficult to obtain insulation in that direction. In order to solve this problem, insulating coated conductive particles are used in which the surfaces of the conductive particles are coated with an insulating material to prevent contact between the metal layers of the conductive particles.

For example, Patent Document 1 describes coated particles in which a particle having a surface made of a conductive metal is used as a core, and the surface of the particle is partially modified with organic particles made of an organic compound containing a functional group that has a binding ability to the metal, and it is described that the organic compound has a positive or negative charge.
Patent Document 2 describes coated particles similar to those described in Patent Document 1. The document describes that the coated particles form a single-layer coating layer by chemically bonding insulating fine particles to particles having a surface made of a conductive metal via functional groups that have binding properties to metal. The document describes that the coated particles having such a configuration can be thermocompressed between electrodes to melt, deform, or peel off the insulating fine particles, thereby exposing the metal surface of the metal-coated particles, thereby enabling conduction between the electrodes and obtaining connectivity. Patent Documents 1 and 2 exemplify ammonium groups and sulfonium groups as the functional groups.

Patent Document 3 also describes that insulating resin fine particles that have a hetero element or functional group on the surface that has a bonding force with a metal are applied to the surface of metal-coated particles, and then the particles are heated to obtain anisotropic insulating conductive particles having an insulating layer that does not have a particle shape on the surface of the metal-coated particles.

International Publication No. 2002/035555 International Publication No. 2003/025955 International Publication No. 2005/109448

The challenge with conductive particles coated with insulating particles has been to improve the adhesion between the insulating and conductive particles. The adhesion between insulating and conductive particles is important for achieving electrical conduction between opposing electrodes while obtaining insulation in a direction different from that of the opposing electrodes (hereinafter, also referred to simply as connection reliability), so there is a demand for the development of coated particles that have even better adhesion between insulating and conductive particles.

Therefore, the object of the present invention is to provide coated particles with improved adhesion between insulating particles and conductive particles, and a conductive material containing the same.

In light of the above situation, the inventors conducted extensive research and discovered that, in coated particles in which conductive particles having a metal film formed on the surface of a core material are coated with insulating particles, the insulating particles are silica particles whose surfaces have been surface-treated with a silane coupling agent having a mercapto group, resulting in coated particles with excellent adhesion between the insulating particles and the conductive particles, and thus completing the present invention.

In other words, the first invention that the present invention aims to provide is a coated particle in which the surface of a conductive particle having a metal film formed on the surface of a core particle is coated with insulating particles, and the insulating particles are silica particles whose surfaces have been surface-treated with a silane coupling agent having a mercapto group.

The second invention that the present invention provides is a conductive material containing the coated particles of the first invention and an insulating resin.

The coated particles of the present invention have excellent adhesion to conductive particles due to the silane coupling agent having a mercapto group present on the surface of the silica particles used as the insulating particles.
Such coated particles of the present invention can have high connection reliability.

The present invention will now be described based on preferred embodiments.
The coated particles of this embodiment are conductive particles having a metal coating formed on the surface of a core particle, the surface of which is coated with insulating particles, and are characterized in that the insulating particles are silica particles whose surfaces have been surface-treated with a silane coupling agent having a mercapto group.

(Conductive particles)
As the conductive particles, known particles that have been conventionally used in conductive adhesives, anisotropic conductive films, and anisotropic conductive adhesives can be used.

The core particles in the conductive particles can be inorganic or organic, with no particular restrictions. Examples of inorganic core particles include metal particles such as gold, silver, copper, nickel, palladium, and solder, alloys, glass, ceramics, silica, metal or nonmetal 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. On the other hand, examples of organic core particles include thermoplastic resins such as natural fibers, natural resins, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polybutene, polyamide, polyacrylic ester, polyacrylonitrile, polyacetal, ionomers, and polyesters, alkyd resins, phenolic 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. A composite material of an organic substance and an inorganic substance may also be used. Examples include styrene-silica composite resin, acrylic-silica composite resin, crosslinked alkoxysilyl polymer-acrylic resin, polyorganosiloxane-silica, etc. Among these, core particles made of resin or a composite material of organic and inorganic substances are preferred because they have a smaller specific gravity than core particles made of metal and are less likely to settle, have excellent dispersion stability, and are easier to maintain electrical connection due to the elasticity of the resin. In addition, the composite material of organic and inorganic substances may have a core-shell structure.

When an organic substance is used as the core particle, it is preferable that the core particle does not have a glass transition temperature or that the glass transition temperature is greater than 100°C, since the shape of the core particle is easily maintained in the anisotropic conductive connection process and in the process of forming the metal film. When the core particle has a glass transition temperature, the glass transition temperature is preferably 200°C or less, since the conductive particles are easily softened in the anisotropic conductive connection and the contact area is increased, making it easier to obtain electrical continuity. From this perspective, when the core particle has a glass transition temperature, the glass transition temperature is more preferably greater than 100°C and less than 180°C, and particularly preferably greater than 100°C and less than 160°C.

When an organic material is used as the core particle, if the organic material is a highly crosslinked resin, the glass transition temperature is hardly observed even when the measurement is attempted up to 200°C by the method described in the following examples. In this specification, such particles are also referred to as particles without a glass transition point, and such core particles may be used in the present invention. Specific examples of the core particle material without such a glass transition temperature can be obtained by copolymerizing the monomer constituting the organic material exemplified above with a crosslinkable monomer. Examples of crosslinkable monomers include tetramethylene di(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(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, trimeterolpropane tri(meth)acrylate, tetramethylolmethane di(meth)acrylate, tetramethylolmethane tri(meth)acrylate, Examples of such hard organic materials include polyfunctional (meth)acrylates such as tetramethylolmethane tetra(meth)acrylate, tetramethylolpropane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, glycerol di(meth)acrylate, glycerol tridi(meth)acrylate, etc., polyfunctional vinyl monomers such as divinylbenzene and divinyltoluene, silane-containing monomers such as vinyltrimethoxysilane, trimethoxysilylstyrene, γ-(meth)acryloxypropyltrimethoxysilane, etc., and monomers such as triallyl isocyanurate, diallyl phthalate, diallyl acrylamide, diallyl ether, etc. In particular, in the field of COG (Chip on Glass), core particles made of such hard organic materials are often used.

There are no particular limitations on the shape of the core particles. In general, the core particles are spherical. However, the core particles may be in a shape other than spherical, for example, fibrous, hollow, plate-like or needle-like, and may have a large number of protrusions on their surface or may be amorphous. In the present invention, spherical core particles are preferred because they have excellent filling properties and are easy to coat with metal.

The particle size distribution of the powder made of core particles measured by the above-mentioned method has a certain range. In general, the range of the particle size distribution of a powder is represented by the coefficient of variation shown in the following formula (1).
Coefficient of variation (%) = (standard deviation / average particle size) x 100 (1)
A large coefficient of variation indicates that the distribution is broad, while a small coefficient of variation indicates that the particle size distribution is sharp. In the present invention, it is preferable to use core particles having a coefficient of variation of 30% or less, particularly 20% or less, and especially 10% or less. The reason for this is that when the conductive particles of the present invention are used as conductive particles in an anisotropic conductive film, there is an advantage in that the contribution ratio effective for connection is high.

In addition, other physical properties of the core material particles are not particularly limited, but when the core material particles are resin particles, it is preferable that the value of K defined by the following formula (2) is in the range of 100 N/mm ² to 100,000 N/mm ² at 20° C., and the recovery rate after 10% compressive deformation is in the range of 1% to 100% at 20° C. By satisfying these physical property values, sufficient contact with the electrodes can be achieved without damaging the electrodes when they are pressed together.
K value (N/ ^mm2 ) = (3/√2) x F x S ^-3/ 2 x R ^-1/2 (2)
(Here, F and S shown in formula (2) are the load value (N) and compression displacement (mm) at 10% compression deformation of the microsphere when measured using a microcompression tester MCTM-500 (manufactured by Shimadzu Corporation), and R is the radius of the microsphere (mm).)

The shape of the conductive particles is not particularly limited, although it depends on the shape of the core particles. For example, they may be fibrous, hollow, plate-like, or needle-like, but spherical ones are preferred because they have excellent filling properties and connectivity.

The conductive particles may have a smooth surface. Alternatively, the conductive particles may have a plurality of protrusions protruding from the surface. If the protrusions are a continuum made of the same material as the metal coating, the conductivity is further improved, which is preferable. More specifically, the metal coating has a flat portion and a plurality of protrusions protruding from the flat portion and forming a continuum from the flat portion, and the flat portion and the protrusions are preferably made of the same material. The term "continuum" means that the protrusions and flat portion of the metal coating are formed by a single process, and there is no part between the flat portion and the protrusions of the metal coating that impairs the sense of unity, such as a seam. However, with regard to the protrusions, the protrusions are made of a particle linkage formed by connecting a plurality of particles made of the material that constitutes the metal coating in a row, and it is acceptable for grain boundaries to be observed between the particles. Therefore, for example, when a core particle for forming a protrusion, such as a non-metallic inorganic material such as a metal, a metal oxide, graphite, or a conductive polymer, is attached to the surface of a core particle, and the protrusion is formed with the core particle as the starting point of growth, the flat portion and the protrusion are not formed in a single process, and therefore are not included in the continuum referred to in the present invention. However, it should be noted that a conductive particle having a protrusion formed by attaching such a core particle to a core particle and using the core particle as the starting point of growth is also within the scope of the present invention.

When the conductive particles have protrusions of the above-mentioned configuration, the protrusions can break through the oxide film formed on the electrode surface when the electrodes are electrically connected, thereby reducing the connection resistance.

The height H of the protrusions is preferably 20 nm or more, particularly 50 nm or more, on average. The number of protrusions depends on the particle size of the conductive particles, but it is preferable that there be 1 to 20,000 protrusions, particularly 5 to 5,000 protrusions per particle, from the viewpoint of further improving the conductivity of the conductive particles. The aspect ratio of the protrusions is preferably 0.5 or more, more preferably 1 or more. A large aspect ratio of the protrusions is advantageous because they can easily break through the oxide film described above.
In addition, when an anisotropic conductive film is formed using conductive particles, it is believed that a large aspect ratio of the protrusions increases the resin rejection property and therefore the conductivity becomes high. The aspect ratio is the ratio of the height H of the protrusions to the length D of the base of the protrusions, i.e., a value defined as H/D.

The aspect ratio of the protrusions is as described above, and the length D of the base of the conductive particle protrusions is preferably 5 to 500 nm, particularly 10 to 400 nm, and the height H of the protrusions is preferably 5 to 500 nm, particularly 10 to 400 nm.

The metal coating in the conductive particles is conductive, and examples of the constituent metals include metals such as gold, platinum, silver, copper, iron, zinc, nickel, tin, lead, antimony, bismuth, cobalt, indium, titanium, antimony, bismuth, germanium, aluminum, chromium, palladium, tungsten, and molybdenum, as well as alloys thereof, and metal compounds such as ITO and solder. Among these, gold, silver, copper, nickel, palladium, and solder are preferred because of their low resistance, and nickel, palladium, gold, nickel alloys, palladium alloys, and gold alloys are particularly preferred because of their high bonding with insulating particles. The metals in the conductive particles can be used alone or in combination of two or more. Nickel alloys also include nickel-phosphorus, nickel-boron, and nickel-boron-phosphorus, and palladium alloys also include palladium-phosphorus and palladium-boron.

The metal coating may be a single layer structure or a laminated structure consisting of multiple layers. In the case of a laminated structure consisting of multiple layers, it is preferable from the viewpoint of reducing the connection resistance, particularly when the metal coating is formed by electroless plating, that the underlayer be nickel or a nickel alloy and the outermost layer be nickel, palladium, gold, a nickel alloy, a palladium alloy or a gold alloy.

The thickness of the metal coating on the surface of the core particles is preferably 0.001 μm to 2 μm, and more preferably 0.005 to 1 μm.

Methods for forming a metal coating on the surface of core particles include dry methods using deposition, sputtering, mechanochemical methods, hybridization methods, etc., and wet methods using electrolytic plating, electroless plating, etc. In addition, a metal coating may be formed on the surface of core particles by combining these methods, but conductive particles in which a metal coating is formed on the surface of core particles by electroless plating are preferred because the particle surface can be uniformly and densely coated.

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 do not cause a short circuit in a direction different from that between the opposing electrodes, and it is easy to ensure conduction between the opposing electrodes. In the present invention, the average particle diameter of the conductive particles is the average particle diameter measured using a scanning electron microscope (SEM). In addition, 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 insulating particles are not spherical, the particle diameter measured using SEM refers to the longest length (maximum length) of the line segments that cross the image of the conductive particles.

Specifically, the average particle size of the conductive particles is measured by the method described in the examples.

In addition, conductive particles that contain fewer impurity ions such as alkali metal ions, halogen ions, and organic acid ions that dissolve are preferred from the viewpoint of suppressing corrosion of electrodes, etc.

(Insulating Particles)
The insulating particles used in the present invention are silica particles whose surfaces have been treated with a silane coupling agent having a mercapto group.

Examples of silica particles that can be used include those produced by growing particles from sodium silicate or an active silicic acid solution, those produced using an organic silicon compound as a raw material, vapor-phase silica, precipitated silica, etc.

The preferred physical properties of the silica particles are an average particle size of 5 to 500 nm, preferably 10 to 300 nm, as determined by dynamic light scattering. By having the average particle size of the silica particles within the above range, the insulating particles are easily adsorbed in a uniformly dispersed state on the particle surface of the conductive particles.

The silane coupling agent having a mercapto group for surface-treating the silica particles is a silica compound having a mercapto group and a hydrolyzable group, and is preferably represented by the following general formula (1).
R ¹ Si(OR ² ) ₃ (1)
(In the formula, R ¹ represents a hydrocarbon group having 1 to 8 carbon atoms and having 1 to 3 mercapto groups, an alicyclic hydrocarbon group having 1 to 3 mercapto groups, or an aromatic hydrocarbon group having 6 to 8 carbon atoms and having 1 to 3 mercapto groups. ^{R 2} represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 8 carbon atoms. Note that each R ² may be the same group or different groups.)

Specific examples of compounds include 3-mercaptopropyltrimethoxysilane, 2-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, and 2-mercaptoethyltriethoxysilane.

The amount of the silane coupling agent having a mercapto group to be coated is preferably 0.1 to 10% by mass, and more preferably 1 to 5% by mass, from the viewpoint of being able to uniformly coat the surface of the silica particles.

The amount of the silane coupling agent having a mercapto group coated on the silica particles is preferably 0.8×10 ⁻²⁴ to 6.6×10 ⁻²⁴ mol, and more preferably 3.3×10 ⁻²⁴ ×6.6×10 ⁻²⁴ mol per nm ² of the specific surface area of the silica particles.

The surface treatment of silica particles with a silane coupling agent having a mercapto group can be carried out in a wet or dry manner.

When the surface treatment of silica particles with a silane coupling agent having a mercapto group is carried out by a wet method, examples of the surface treatment method include: 1) a method in which silica particles are immersed in a solvent containing a silane coupling agent having a mercapto group at a desired concentration, and if necessary heated to promote the reaction between the silica particles and the silane coupling agent having a mercapto group, and then spray-dried together with the solvent or solid-liquid separation is performed, followed by drying; and 2) a method in which a silane coupling agent having a mercapto group is added to a dispersion containing silica particles and a solvent, and the reaction is carried out by heating to 50 to 100° C., and then spray-dried together with the solvent or solid-liquid separation is performed, followed by drying.
The solvent that can be used in the wet method can be alcohol such as methanol, ethanol, propanol, or a mixed solvent of these alcohols and water.In addition, commercially available silica sol can be used as silica particles, and in the case of aqueous silica sol, alcohol is added to make a mixed solution of alcohol and water, and for example, in the above 2), a silane coupling agent having a mercapto group is added to this mixed solution to use as a dispersion.

When surface treatment of silica particles with a silane coupling agent having a mercapto group is performed by a dry method, examples of the surface treatment method include a method of dry mixing the silane coupling agent having a mercapto group and silica particles using mechanical means such as a Henschel mixer or an airflow grinder, or a method of diluting the silane coupling agent having a mercapto group with a solvent, mixing the diluted solution with silica particles, and heating and drying the resulting mixture.

In the present invention, it is preferable to use insulating particles obtained by the wet method 2) above, because it is easy to obtain monodispersed insulating particles and to obtain particles with a high coverage rate.

(Coated Particles)
The surface of the conductive particles may be coated with the insulating particles by a wet method or a dry method.

In the dry method, the mixture is prepared by mechanical means that exerts a strong shearing force. Apparatuses that can be used in the dry method include high-speed mixers, super mixers, turbosphere mixers, Eirich mixers, Henschel mixers, hybridization systems, Nauta mixers, ribbon blenders, jet mills, and cosmoizers.

The wet method is a method in which insulating particles and conductive particles are brought into contact with each other through a solvent under stirring, and the insulating particles are attached to the surfaces of the conductive particles. Examples of solvents that can be used include water, acetone, methanol, ethanol, and mixtures of these. The temperature at which the insulating particles and conductive particles are brought into contact is not particularly limited, but is 5 to 100°C, preferably 10 to 50°C, and is also sufficient even at around room temperature (25°C). The coated particles of the present invention can be obtained by recovering the solid content from the solvent by a conventional method, and washing and drying as necessary.

Alternatively, the coated particles of the present invention may be obtained by a method in which a compound having, within the same molecule, a functional group (A) reactive with the metal coating in the conductive particle and a functional group (B) reactive with the mercapto group in the insulating particle (hereinafter sometimes referred to as a "reactive compound") is reacted with the metal coating of the conductive particle in a first step, and then reacted with the insulating particle in a second step.
Examples of the functional group (A) include a silane group, a silanol group, a carboxyl group, an amino group, an ammonium group, a nitro group, a hydroxyl group, a carbonyl group, a thiol group, a sulfonic acid group, a sulfonium group, a boric acid group, an oxazoline group, a pyrrolidone group, a phosphate group, and a nitrile group.
Examples of the functional group (B) include an epoxy group, an amino group, a halide group, a hydroxyl group, a carboxylic acid halide group, a carboxylic acid anhydride group, a group having a carbon-carbon double bond, a cyclic ether group, a cyclic thioether group, an isocyanato group, and an isothiocyanato group.

The first step can be carried out by a known method, for example, the method described in WO2003/025955, JP2001-342377A, JP2003-26813A, etc.

The second step can be carried out wet or dry.

In the dry method, the mixture is prepared by mechanical means that exerts a strong shearing force. Apparatuses that can be used in the dry method include high-speed mixers, super mixers, turbosphere mixers, Eirich mixers, Henschel mixers, hybridization systems, Nauta mixers, ribbon blenders, jet mills, and cosmoizers.

The wet method is a method in which insulating particles and conductive particles coated with a reactive compound are brought into contact with each other through a solvent under stirring, and the insulating particles are attached to the surfaces of the conductive particles coated with the reactive compound. Examples of solvents that can be used include water, acetone, methanol, ethanol, and mixtures of these. The temperature at which the insulating particles and the conductive particles coated with the reactive compound are brought into contact is not particularly limited, but is 5 to 100°C, preferably 10 to 50°C, and is sufficient even at around room temperature (25°C). The coated particles of the present invention can be obtained by recovering solids from the solvent by a conventional method, and washing and drying are performed as necessary.

The coated particles according to the present invention preferably have a coverage rate of 30% or more, preferably 30 to 100%, and particularly 30 to 80%, of the insulating particles, from the viewpoint of achieving excellent electrical reliability when the coated particles are used to electrically connect upper and lower electrodes.

The coverage rate was calculated by counting the number n of insulating particles attached to the conductive particles using a SEM and using the following formula: The coverage rate used in the evaluation was the average value of 20 coated particles.
Coverage (%) = (n/N) x 100
N: The number of insulating particles when the insulating particles are arranged in close packing on the surface of a conductive particle, N = 4π(R + r) ² / 2√3r ²
(R: radius of conductive particle (nm), r: radius of insulating particle (nm))

The coated particles of the present invention use silica particles treated with a silane coupling agent having a mercapto group as the insulating particles. The silane coupling agent having a mercapto group is a silica compound having a mercapto group and a hydrolyzable group, and the hydrolyzable group of the silica compound reacts easily with the silica particles, and the silica compound bonds to the silica particles. Meanwhile, the mercapto group bonds firmly to the metal coating of the conductive particles or the functional group (B) of the reactive compound. Therefore, the coated particles of the present invention have excellent adhesion between the insulating particles and the conductive particles.

In addition, the coated particles according to the present invention may be conductive particles that have been surface-treated with a hydrophobizing agent. The presence of a hydrophobizing agent on the surface of the conductive particles provides excellent affinity with the insulating particles, and the coverage of the insulating particles can be further increased.
Examples of the hydrophobizing agent include benzotriazole compounds, titanate coupling agents, higher fatty acids or derivatives thereof, phosphates, and phosphites, etc. These may be used alone or in combination of two or more kinds, if necessary.

In this case, the insulating particles may be 1) bonded to the conductive particles via a hydrophobizing agent present on the particle surface of the conductive particles, 2) bonded directly to the particle surface of the conductive particles without the hydrophobizing agent, or may be bonded in a mixture of 1) and 2).

（式中、Ａ₁、Ａ₂は同一の又は異なるアルキル基、アリール基、ハロゲン原子、水酸基、アミノ基又はカルボキシル基を示し、ｐ１、ｑ１は同一の又は異なる０～２の整数を示す。）
前記一般式（２）の式中のＡ₁及びＡ₂は、アルキル基、アリール基、ハロゲン原子、水酸基、アミノ基又はカルボキシル基を示す。該アルキル基としては、メチル基、エチル基、プロピル基、ブチル基等の炭素数が１～５のものが好ましい。該アリール基としては、フェニル基、トリル基、キシリル基、ナフチル基が好ましい。該ハロゲン原子としては、塩素、臭素、ヨウ素が挙げられる。前記一般式（２）中のｐ１及びｑ１は、同一の又は異なる０～２の整数を示す。また、Ａ₁とＡ₂は同一の基でも異なる基であってもよい。 The benzotriazole compound is preferably one represented by the following general formula (2).

(In the formula, A ₁ and A ₂ are the same or different and each represents an alkyl group, an aryl group, a halogen atom, a hydroxyl group, an amino group, or a carboxyl group, and p1 and q1 are the same or different and each represents an integer of 0 to 2.)
In the general formula (2), A ₁ and A ₂ represent an alkyl group, an aryl group, a halogen atom, a hydroxyl group, an amino group, or a carboxyl group. The alkyl group is preferably an alkyl group having 1 to 5 carbon atoms, such as a methyl group, an ethyl group, a propyl group, or a butyl group. The aryl group is preferably a phenyl group, a tolyl group, a xylyl group, or a naphthyl group. The halogen atom includes chlorine, bromine, and iodine. In the general formula (2), p1 and q1 represent integers of 0 to 2, which may be the same or different. A ₁ and A ₂ may be the same or different groups.

Specific preferred examples of the benzotriazole-based compound represented by the general formula (2) include benzotriazole, 4-methylbenzotriazole, 5-methylbenzotriazole, 4-ethylbenzotriazole, 5-ethylbenzotriazole, 4,5-dimethylbenzotriazole, 4,6-dimethylbenzotriazole, 5,6-dimethylbenzotriazole, 4,5-diethylbenzotriazole, 4,6-diethylbenzotriazole, 5,6-diethylbenzotriazole, 4-phenylbenzotriazole, 5-phenylbenzotriazole, 4-chlorobenzotriazole, 5-chlorobenzotriazole, 4-carboxybenzotriazole, 5-carboxybenzotriazole, 4,5-dicarboxybenzotriazole, and 4,6-dicarboxybenzotriazole.

Examples of titanate coupling agents include those represented by the following formula (i) or formula (ii).
(B ¹ O) Ti (OB ² ) (OB ³ ) (OB ⁴ ) (i)
(In the formula, B ¹ is an alkyl group, and B ² to B ⁴ are each a group selected from an alkyl group, a group in which a methylene group other than the terminal group in an alkyl group is substituted with an oxygen atom, an alkenyl group, a group in which a methylene group other than the terminal group in an alkenyl group is substituted with an oxygen atom, an alkanoyl group, a dialkyl pyrophosphate group, and an alkylbenzenesulfonyl group; provided that at least one of B ² to B ⁴ is an alkanoyl group, a dialkyl pyrophosphate group, or an alkylbenzenesulfonyl group. B ¹ and B ² may join together to form a ring.)

(B ⁵ O)Ti(OB ⁶ )(OB ⁷ )(OB ⁸ )・[P(OB ⁹ ) ₂ OH] ₂ (ii)
(In the formula, B ⁵ to B ⁸ each represent an alkyl group, an alkyl group in which a methylene group other than the terminal is substituted with an oxygen atom, an alkenyl group, or an alkenyl group in which a methylene group other than the terminal is substituted with an oxygen atom. ^B9 is an alkyl group.
In the above-mentioned formula (i), two or three of the groups B ¹ to B ⁴ may be the same, or B ¹ to B ⁴ may all be different. In the compound, two or three groups among B ⁵ to B ⁸ may be the same, or B ⁵ to B ⁸ may all be different. Two B ⁹ groups may be the same or different. In the compound represented by formula (i), the number of alkanoyl groups, dialkylpyrophosphate groups or alkylbenzenesulfonyl groups is preferably 1 to 3, more preferably 2 to 3, and particularly preferably 3.

Examples of the alkyl groups listed above include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, 2-methylbutyl, 1-methylbutyl, n-hexyl, isohexyl, 3-methylpentyl, 2-methylpentyl, 1-methylpentyl, heptyl, octyl, isooctyl, 2-ethylhexyl, 3,7-dimethyloctyl, nonyl, decyl, undecyl, dodecyl, lauryl, tetradecyl, hexadecyl, octadecyl (including stearyl), nonadecyl, eicosyl, triacontyl, and tetracontyl. Examples of the alkenyl groups include groups in which one or more of the carbon-carbon single bonds of the above alkyl groups are changed to carbon-carbon double bonds.

An example of an alkyl group in which a methylene group other than the terminal is replaced with an oxygen atom is not an alkoxy group, but rather a group in which an oxygen atom interrupts the methylene groups in the alkyl group. Similar examples of an alkenyl group in which a methylene group other than the terminal is replaced with an oxygen atom.

The number of carbon atoms of the alkyl groups represented by B ¹ to B ⁴ and B ⁵ to B ⁸ , the groups in which the methylene groups other than the terminals in the alkyl groups are substituted with oxygen atoms, the alkenyl groups, and the groups in which the methylene groups other than the terminals in the alkenyl groups are substituted with oxygen atoms, is preferably 3 to 40, more preferably 3 to 32. The alkanoyl groups represented by ^{B 2} to B ⁴ preferably have 2 to 40 carbon atoms. The alkyl groups of the dialkyl pyrophosphate groups represented by ^{B 2} to B 4 preferably have 3 to 40 carbon atoms. The alkyl groups of the alkylbenzenesulfonyl groups represented by B 2 to B ⁴ preferably have 3 to 40 carbon atoms. The alkyl groups of the alkylbenzenesulfonyl groups represented by ^{B 2} to B ⁴ preferably have 3 to 40 carbon atoms. The alkyl groups of the alkyl groups represented by ^{B 9} preferably have 3 to 40 carbon atoms.

The ring formed by B ¹ and B ² taken together includes a ring formed by -CH ₂ -CH ₂ - or -CH ₂ -COO-, etc., together with the oxygen atom and titanium atom in formula (i).

Each group represented by the above formula (i) or formula (ii) may be substituted with a substituent. In this case, examples of the substituent include a halogen atom, an epoxy group, an amino group, a vinyl group, an acrylic group, an isocyanate group, and a mercapto group.

Specific examples of titanate-based coupling agents used in the present invention include isopropyl triisostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, isopropyl tris(dioctyl pyrophosphate) titanate, tetraisopropyl(dioctyl phosphite) titanate, tetraisopropyl bis(dioctyl phosphite) titanate, tetraoctyl bis(ditridecyl phosphite) titanate, tetra(2,2-diallyloxymethyl-1-butyl)bis(ditridecyl)phosphite titanate, bis(dioctyl pyrophosphate)oxyacetate titanate, bis(dioctyl pyrophosphate)ethylene titanate, and the like. These may be used alone or in combination of two or more.
These titanate coupling agents are commercially available, for example, from Ajinomoto Fine-Techno Co., Ltd.

The higher fatty acid is preferably a saturated or unsaturated linear or branched mono- or polycarboxylic acid, more preferably a saturated or unsaturated linear or branched monocarboxylic acid, and even more preferably a saturated or unsaturated linear monocarboxylic acid. The fatty acid preferably has 7 or more carbon atoms. The derivative refers to a salt or amide of the fatty acid.

The fatty acid or its derivative used in the present invention preferably has 7 to 23 carbon atoms, more preferably 10 to 20. Examples of such fatty acids or their derivatives include saturated fatty acids such as capric acid, lauric acid, myristic acid, palmitic acid, and stearic acid, unsaturated fatty acids such as oleic acid, linoleic acid, linolenic acid, and arachidonic acid, and metal salts or amides thereof. Examples of metal salts of fatty acids include salts of alkali metals, alkaline earth metals, transition metals such as Zr, Cr, Mn, Fe, Co, Ni, Cu, and Ag, and metals other than transition metals such as Al and Zn, and are preferably polyvalent metal salts such as Al, Zn, W, and V. The fatty acid metal salt may be mono-, di-, tri-, or tetra-form depending on the valence of the metal. The fatty acid metal salt may be any combination of these.

As the phosphate ester and the phosphite ester, those having an alkyl group having 6 to 22 carbon atoms are preferably used.
Examples of phosphate esters include hexyl phosphate, heptyl phosphate, monooctyl phosphate, monononyl phosphate, monodecyl phosphate, monoundecyl phosphate, monododecyl phosphate, monotridecyl phosphate, monotetradecyl phosphate, and monopentadecyl phosphate.
Examples of phosphite esters include hexyl phosphite, heptyl phosphite, monooctyl phosphite, monononyl phosphite, monodecyl phosphite, monoundecyl phosphite, monododecyl phosphite, monotridecyl phosphite, monotetradecyl phosphite, and monopentadecyl phosphite.

In the present invention, the hydrophobizing agent is preferably a triazole-based compound or a titanate-based coupling agent, since it has excellent affinity with insulating particles and is highly effective in increasing the coverage of insulating particles. In particular, benzotriazole, 4-carboxybenzotriazole, isopropyl triisostearoyl titanate, and tetraisopropyl (dioctyl phosphite) titanate are particularly preferred.

In the present invention, the hydrophobizing agent may be present on the surface of the conductive particle, and in that case, the hydrophobizing agent may be present on the entire surface of the conductive particle or only on a part of the surface. The hydrophobizing agent may also form a layer that covers a part or the entire surface of the conductive particle.
The hydrophobizing agent may be present on the surface of the conductive particles as a condensation product thereof.

There are no particular limitations on the method for surface-treating the conductive particles with a hydrophobizing agent, and any known method can be used. One example is a method in which the conductive particles and the hydrophobizing agent are mixed in a solvent.

The solvent may be water or an organic solvent, or may be a mixed solvent of water and an organic solvent. Examples of organic solvents include toluene, methanol, ethanol, propanol, butanol, isobutyl alcohol, acetone, methyl ethyl ketone, tetrahydrofuran, acetonitrile, N-methylpyrrolidone, and dimethylformamide. In a dispersion in which conductive particles and a hydrophobizing agent are added to a solvent, the concentration of the hydrophobizing agent is 0.01 to 20% by mass. The concentration of the conductive particles in this dispersion is 1 to 50% by mass.

After the treatment, the dispersion liquid is filtered and, if necessary, dried to obtain conductive particles having a hydrophobizing agent on their surfaces.

In addition, as a method for coating the insulating particles on the particle surfaces of the conductive particles that have been surface-treated with a hydrophobizing agent, a method similar to the method for coating the insulating particles on the particle surfaces of the conductive particles described above can be used.

The coated particles of the present invention are suitable for use as, for example, anisotropic conductive films (ACFs), heat seal connectors (HSCs), and conductive materials for connecting electrodes of liquid crystal display panels to the circuit boards of driving LSI chips, taking advantage of the insulating properties between coated particles and the connectivity between opposing electrodes. In particular, they are suitable for use as conductive fillers in conductive adhesives.

The conductive adhesive is preferably used as an anisotropic conductive adhesive that is placed between two substrates on which a conductive base material is formed, and that adheres the conductive base material to provide electrical conductivity by heating and pressurization. This anisotropic conductive adhesive contains the conductive particles of the present invention and an adhesive resin. Any adhesive resin that is insulating and can be used as an adhesive resin can be used without particular restrictions. It may be either a thermoplastic resin or a thermosetting resin, and it is preferable that the adhesive performance is expressed by heating. Such adhesive resins include, for example, a thermoplastic type, a thermosetting type, and an ultraviolet curing type. In addition, there are so-called semi-thermosetting types that show intermediate properties between the thermoplastic type and the thermosetting type, and composite types of a thermosetting type and an ultraviolet curing type. These adhesive resins can be appropriately selected according to the surface characteristics of the circuit board or the like to be adhered and the form of use. In particular, adhesive resins that contain a thermosetting resin are preferable because they have excellent material strength after adhesion.

Specific examples of adhesive resins include those prepared using as the main component one or a combination of two or more selected from ethylene-vinyl acetate copolymer, carboxyl-modified ethylene-vinyl acetate copolymer, ethylene-isobutyl acrylate copolymer, polyamide, polyimide, polyester, polyvinyl ether, polyvinyl butyral, polyurethane, SBS block copolymer, carboxyl-modified SBS copolymer, SIS copolymer, SEBS copolymer, maleic acid-modified SEBS copolymer, polybutadiene rubber, chloroprene rubber, carboxyl-modified chloroprene rubber, styrene-butadiene rubber, isobutylene-isoprene copolymer, acrylonitrile-butadiene rubber (hereinafter referred to as NBR), carboxyl-modified NBR, amine-modified NBR, epoxy resin, epoxy ester resin, acrylic resin, phenolic resin, and silicone resin. Of these, styrene-butadiene rubber and SEBS are preferred as thermoplastic resins because they have excellent reworkability. Epoxy resin is preferred as a thermosetting resin. Of these, epoxy resin is the most preferred due to its advantages of high adhesive strength, excellent heat resistance and electrical insulation, low melt viscosity, and the ability to connect at low pressure.

As the epoxy resin, any commonly used epoxy resin can be used as long as it is a polyhydric epoxy resin having two or more epoxy groups in one molecule. Specific examples include novolac resins such as phenol novolac and cresol novolac; polyhydric phenols such as bisphenol A, bisphenol F, bisphenol AD, resorcin, and bishydroxydiphenyl ether; polyhydric alcohols such as ethylene glycol, neopentyl glycol, glycerin, trimethylolpropane, and polypropylene glycol; polyamino compounds such as ethylenediamine, triethylenetetramine, and aniline; and polyvalent carboxy compounds such as adipic acid, phthalic acid, and isophthalic acid, and glycidyl-type epoxy resins obtained by reacting epichlorohydrin or 2-methylepichlorohydrin. Other examples include aliphatic and alicyclic epoxy resins such as dicyclopentadiene epoxide and butadiene dimer diepoxide. These can be used alone or in combination of two or more.

In addition, from the viewpoint of preventing ion migration, it is preferable to use high-purity adhesive resins with reduced impurity ions (such as Na and Cl) and hydrolyzable chlorine as the various adhesive resins mentioned above.

The amount of conductive particles used in an anisotropic conductive adhesive is usually 0.1 to 30 parts by mass, preferably 0.5 to 25 parts by mass, and more preferably 1 to 20 parts by mass, per 100 parts by mass of the adhesive resin component. By keeping the amount of conductive particles within this range, increases in connection resistance and melt viscosity are suppressed, connection reliability is improved, and sufficient anisotropy of the connection can be ensured.

In addition to the conductive particles and adhesive resin described above, the anisotropic conductive adhesive may contain additives known in the art. The amount of additives may be within the range known in the art. Examples of other additives include tackifiers, reactive assistants, epoxy resin curing agents, metal oxides, photoinitiators, sensitizers, curing agents, vulcanizing agents, deterioration inhibitors, heat resistance additives, thermal conductivity enhancers, softeners, colorants, various coupling agents, and metal deactivators.

Examples of tackifiers include rosin, rosin derivatives, terpene resins, terpene phenol resins, petroleum resins, coumarone-indene resins, styrene resins, isoprene resins, alkylphenol resins, and xylene resins. Examples of reactive auxiliaries, i.e., crosslinking agents, include polyols, isocyanates, melamine resins, urea resins, utropines, amines, acid anhydrides, and peroxides. As epoxy resin curing agents, any agent having two or more active hydrogens per minute can be used without any particular restrictions. Specific examples include polyamino compounds such as diethylenetriamine, triethylenetetramine, metaphenylenediamine, dicyandiamide, and polyamidoamine; organic acid anhydrides such as phthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, and pyromellitic anhydride; and novolac resins such as phenol novolac and cresol novolac. These can be used alone or in combination of two or more. A latent curing agent may also be used as necessary. Examples of usable latent curing agents include imidazoles, hydrazides, boron trifluoride-amine complexes, sulfonium salts, aminimides, polyamine salts, dicyandiamide, and modified versions of these. These can be used alone or as a mixture of two or more.

The anisotropic conductive adhesive is manufactured using manufacturing equipment commonly used in the technical field. For example, it is manufactured by blending conductive particles and adhesive resin, as well as a curing agent and various additives as necessary, and mixing them in an organic solvent if the adhesive resin is a thermosetting resin, or by melt-kneading them at a temperature above the softening point of the adhesive resin, specifically preferably at about 50 to 150°C, if the adhesive resin is a thermoplastic resin. The anisotropic conductive adhesive obtained in this way may be applied as a coating or in the form of a film.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.
<Preparation of insulating particle samples>
(Insulating Particle 1)
In a reaction vessel, 34.1 g of methanol was added to 44.1 g of aqueous silica sol (SiO ₂ : 22.7 mass%, water: 77.3 mass%) to obtain a dispersion. Next, 0.15 g of 3-mercaptopropyltrimethoxysilane was added to the dispersion while stirring, and the mixture was stirred for 20 minutes. Next, the reaction vessel was heated to 60°C and stirred for 3 hours to complete the reaction.
After the reaction was completed, the solid content was recovered by filtration, washed with methanol, and dried at 120° C. under vacuum for 12 hours to obtain insulating particles in which the surfaces of the silica particles were surface-treated with 3-mercaptopropyltrimethoxysilane.
The aqueous silica sol used was commercially available and had a particle size of 219 nm as determined by dynamic light scattering.

(Insulating Particles 2)
In a reaction vessel, 35.9 g of methanol was added to 55.9 g of aqueous silica sol (SiO ₂ : 22.7 mass%, water: 77.3 mass%) to obtain a dispersion. Next, 0.39 g of 3-mercaptopropyltrimethoxysilane was added to the dispersion while stirring, and the mixture was stirred for 20 minutes. Next, the reaction vessel was heated to 60°C and stirred for 3 hours to complete the reaction.
After the reaction was completed, the solid content was recovered by filtration, washed with methanol, and dried at 120° C. under vacuum for 12 hours to obtain insulating particles in which the surfaces of the silica particles were surface-treated with 3-mercaptopropyltrimethoxysilane.
The aqueous silica sol used was commercially available and had a particle size of 144 nm as determined by dynamic light scattering.

(Insulating Particles 3)
100 ml of pure water was added to a 200 ml four-neck flask equipped with a stirring blade. Then, 30.00 mmol of styrene monomer, 0.03 mmol of 4-(vinylbenzyl)triethylammonium chloride, and 0.50 mmol of 2,2'-azobis(2-methylpropionamidine)dihydrochloride as a polymerization initiator were added. Nitrogen was aerated for 15 minutes to expel dissolved oxygen, and the temperature was raised to 60°C and maintained for 6 hours to allow the polymerization reaction to proceed. The dispersion of the fine particles after polymerization was passed through a SUS sieve with a mesh size of 150 μm to remove aggregates. The dispersion from which the aggregates had been removed was centrifuged to settle the fine particles, and the supernatant was removed. Pure water was added to the obtained solid content and washed to obtain spherical fine particles of poly(styrene/4-(vinylbenzyl)triethylammonium chloride). The average particle diameter of the obtained fine particles was 272 nm.

<Preparation of Conductive Particle Sample>
The conductive particles used were the following commercially available conductive particles.
The average particle diameter of the conductive particles was determined by randomly extracting 200 particles from a scanning electron microscope (SEM) photograph (magnification: 100,000 times), measuring their particle diameters, and averaging the measured values.

(Conductive Particle 1)
Ni-plated particles (manufactured by Nippon Chemical Industry Co., Ltd.) having an average particle size of 3 μm and having a nickel coating with a thickness of 0.125 μm on the surface of spherical resin particles were prepared. The resin particles were made of a crosslinkable acrylic resin and had a glass transition temperature of 120° C.
The average particle size was determined by measuring the particle sizes of particles randomly extracted from a scanning electron microscope (SEM) photograph (magnification: 100,000 times), and averaging the measurements.

(Conductive Particles 2)
Ni-plated particles (manufactured by Nippon Chemical Industry Co., Ltd.) having an average particle diameter of 3 μm and a nickel coating having a thickness of 0.125 μm and 1,030 protrusions on the surface of spherical resin particles, with an average height of 0.1 μm, an average base length of 0.197 μm, and an aspect ratio of 0.5. The resin particles were made of a crosslinked acrylic resin and had a glass transition temperature of 120° C. The average particle diameter was measured in the same manner as the conductive particles 1.

(Conductive Particles 3)
Gold-plated particles (manufactured by Nippon Chemical Industry Co., Ltd.) having an average particle size of 4.6 μm and a gold-nickel conductive layer on the surface of spherical resin particles were used. The resin particles were made of a crosslinkable acrylic resin and had a glass transition temperature of 120° C.
The average particle size was determined by measuring the particle sizes of particles randomly extracted from a scanning electron microscope (SEM) photograph (magnification: 100,000 times), and averaging the measurements.

{Examples 1 to 6}
The insulating particle dispersion liquid was prepared by adding pure water to a total volume of 20 ml so that the solid content concentration of the insulating particles obtained above was 10,000 ppm. 50 mg of each of the conductive particle samples was added to this dispersion liquid and stirred at room temperature (25° C.) for 15 hours.
Next, the solid content was separated from the stirred dispersion using a membrane filter with 10 μm openings, washed with water, and dried to obtain a coated particle sample.

{Comparative Example 1}
The insulating particle dispersion liquid was prepared by adding pure water and NaCl to the insulating particles 3 obtained above so that the solid content concentration was 10,000 ppm, the NaCl concentration was 25 mmol, and the total volume was 20 ml. 50 mg of conductive particle sample 1 was added to this dispersion liquid, and the mixture was stirred at room temperature (25° C.) for 15 hours.
Next, the solid content was separated from the stirred dispersion using a membrane filter with 10 μm openings, washed with water, and dried to obtain a coated particle sample.

(Evaluation of Coverage Rate)
The difference in coverage when insulating particles are coated on conductive particles was evaluated from the coated particles obtained in the examples and comparative examples. The results are shown in Table 1. The coverage was determined by the following method.

<Method of measuring coverage>
The number N of insulating particles when the insulating particles are arranged in closest packing on the surface of a conductive particle was calculated using the following formula.
N=4π(R+r) ² /2√3r ²
(R: radius of conductive particle (nm), r: radius of insulating particle (nm))
The number n of insulating particles attached to the conductive particles was counted using an SEM, and the coverage rate was calculated using the following formula. The results are shown in Table 1.
Coverage (%) = (n/N) x 100
The coverage used in the evaluation was the average value for 20 conductive particles.

(Evaluation of Adhesion)
1 g of the coated particles obtained in the examples and comparative examples was added to 100 mL of pure water, and ultrasonic treatment was performed for 2 minutes using an ultrasonic device (VS-D100, manufactured by VELVO-CLEAR) at an oscillation frequency of 24 kHz to obtain coated particles. The coverage of the particles was calculated in the same manner as in the evaluation of the coverage, and the adhesion was calculated using the following formula to evaluate the adhesion, and the results are shown in Table 1. The higher the adhesion value, the less the insulating particles fell off due to ultrasonic treatment, which means that the adhesion between the conductive particles and the insulating particles is high.
Adhesion rate (%)=(coverage rate after ultrasonic treatment/coverage rate before ultrasonic treatment)×100

{Example 7}
100 ml of pure water was added to the conductive particles 2 (5 g) obtained above, and the mixture was stirred to obtain a dispersion of conductive particles 2. 10 ml of a 1 mass% aqueous solution of benzotriazole was added to this dispersion, and the mixture was stirred for 5 minutes to perform a surface treatment. Thereafter, the mixture was filtered through a membrane filter with an opening of 2.0 μm, and conductive particles 2 having a benzotriazole layer on the surface were collected. The collected conductive particles 2 were washed with pure water, and then 100 ml of pure water was added to obtain a dispersion of conductive particles 2 having a benzotriazole layer on the surface.
The insulating particles 1 obtained above were added to this dispersion liquid, and the dispersion liquid was stirred at room temperature (25°C) for 15 hours. After the insulating particles 1 were added, the solid-liquid concentration of the insulating particles 1 in the dispersion liquid was 10,000 ppm by mass. After removing the supernatant, the particles were washed with pure water and then vacuum dried at 50°C to obtain a coated particle sample. The coverage and adhesion of the obtained coated particle sample were evaluated in the same manner as in Examples 1 to 6, and the results are shown in Table 2.

{Example 8}
25 ml of toluene was added to the conductive particles 2 (5 g) obtained above, and the mixture was stirred to obtain a dispersion of conductive particles 2. 0.1 g of isopropyl triisostearoyl titanate (Plenact KR-TTS, manufactured by Ajinomoto Fine-Techno Co., Ltd.) was added to this dispersion, and the mixture was stirred at room temperature for 20 minutes to perform surface treatment. Thereafter, the mixture was filtered through a membrane filter with an opening of 2.0 μm, and conductive particles 2 having a titanate-based coupling agent layer on the surface were collected. 100 ml of a mixture of ethanol:pure water = 75:25 by mass was added to the collected conductive particles 2 to obtain a dispersion of conductive particles 2 having a titanate-based coupling agent layer on the surface.
The insulating particles 1 obtained above were added to this dispersion liquid, and the dispersion liquid was stirred at room temperature (25°C) for 15 hours. After the insulating particles 1 were added, the solid-liquid concentration of the insulating particles 1 in the dispersion liquid was 10,000 ppm by mass. After removing the supernatant, the particles were washed with pure water and then vacuum dried at 50°C to obtain a coated particle sample. The coverage and adhesion of the obtained coated particle sample were evaluated in the same manner as in Examples 1 to 6, and the results are shown in Table 2.

<Evaluation of Conductivity>
An insulating adhesive containing 100 parts by weight of epoxy resin, 150 parts by weight of hardener, and 70 parts by weight of toluene was mixed with 15 parts by weight of the coated particle sample obtained in the example to obtain an insulating paste. This paste was applied to 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 placed between a glass substrate with aluminum vapor-deposited on the entire surface and a polyimide film substrate with a copper pattern formed at a pitch of 50 μm, and an electrical connection was performed. The electrical resistance between the substrates was measured to evaluate the electrical conductivity of the coated particles at room temperature (25° C., 50% RH). The lower the resistance value, the higher the electrical conductivity of the coated particles. The conductivity of the coated particles was evaluated as follows: a resistance value of less than 2 Ω was rated as "very good" (indicated by "◯" in Table 3), a resistance value of 2 Ω or more and less than 5 Ω was rated as "good" (indicated by "△" in Table 3), and a resistance value of 5 Ω or more was rated as "poor" (indicated by "×" in Table 3). The results are shown in Table 3.

Claims (6)

A coated particle in which the surface of a conductive particle having a metal coating formed on the surface of a core particle is coated with an insulating particle, the conductive particle being surface-treated with a hydrophobizing agent selected from a benzotriazole-based compound and a titanate-based coupling agent, and the insulating particle being silica particle surface-treated with a silane coupling agent having a mercapto group. The coated particles according to claim 1, characterized in that the core particles are made of a resin or a composite material of an organic substance and an inorganic substance. The coated particle according to any one of claims 1 to 2, wherein the metal coating is at least one coating selected from nickel, palladium, gold, a nickel alloy, a palladium alloy, and a gold alloy. The coated particles according to any one of claims 1 to 3, characterized in that the conductive particles have multiple protrusions on the metal coating. The coated particles according to any one of claims 1 to 4, characterized in that the silane coupling agent having a mercapto group is mercaptopropyltrimethoxysilane. A conductive material comprising the coated particles according to claim 1 and an insulating resin .