JP7655745B2 - 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 conductive particles with such small particle diameters 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 core is partially modified with organic particles made of an organic compound containing a functional group that has a binding ability to the metal, and the organic compound has a positive or negative charge.

Patent Document 2 also describes coated particles similar to those 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 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 give examples of the functional groups as ammonium groups and sulfonium groups.

Patent Document 3 also describes that insulating resin fine particles that contain heteroelements or functional groups on the surface that have a bonding force with metals are applied to the surface of metal-coated particles, and then the particles are heated to obtain anisotropic insulating conductive particles that have 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 for conductive particles coated with insulating particles has been to improve the adhesion between the insulating particles and the conductive particles. The adhesion between the insulating particles and the 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 the insulating particles and the conductive particles. In addition, because the mechanical force applied during thermocompression causes the conductive particles to shift from the electrodes, there is also a demand for improved electrical conduction reliability.

Therefore, the object of the present invention is to provide coated particles that have excellent adhesion and electrical conductivity reliability between insulating particles and conductive particles, and a conductive material that contains the coated particles.

In light of the above situation, the inventors have conducted extensive research and have discovered that, in coated particles in which the surface of conductive particles having a metal film formed on the surface of a core material is coated with insulating particles, when the insulating particles are silica particles having an uneven surface to which a compound containing a charged functional group or a condensation product thereof is fixed, the coated particles have excellent adhesion between the insulating particles and the conductive particles and also have excellent electrical conductivity reliability, leading to the completion of 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 an insulating particle, and the insulating particle is characterized in that a compound containing a functional group having an electric charge or a condensate thereof is fixed to the surface of a silica particle having an uneven surface.

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 present invention provides coated particles that have excellent adhesion between insulating particles and conductive particles and also have excellent electrical conductivity reliability.

TEM photograph (50,000x) of the silica particles having irregularities used in the examples.

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 the insulating particles are characterized in that a compound containing a functional group having an electric charge or a condensation product thereof is fixed to the surface of a silica particle having an uneven surface.

(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, and styrene-acrylate-silica composite resin. 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. The composite material of organic and inorganic substances may also 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 substance is used as the core particle, if the organic substance 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 having no glass transition point, and such core particles may be used in the present invention. Specific examples of the core particle material having no glass transition temperature can be obtained by copolymerizing the monomer constituting the organic substance 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 varies depending 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 in that 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 are preferred from the viewpoint of suppressing corrosion of electrodes, etc.

The insulating particles used in the present invention are silica particles having an uneven surface, to which a compound containing a charged functional group or a condensation product thereof is fixed.

The silica particles used in the present invention are silica particles with an uneven surface. The silica particles with an uneven surface are obtained by bonding small silica particles to the surface of large silica particles, and it is preferable to use large silica particles having uneven surfaces caused by small silica particles.

The particle size of the large silica particles is 50 to 500 nm, preferably 60 to 250 nm, as determined by TEM observation. By having the average particle size of the large silica particles within the above range, the insulating particles are more likely to be adsorbed in a uniformly dispersed state on the particle surface of the conductive particles.

The particle size of the small silica particles is 3 to 30 nm, preferably 3 to 10 nm, as determined by TEM observation, from the viewpoints of providing excellent adhesion between the insulating particles and the conductive particles, suppressing displacement of the conductive particles from the electrode due to mechanical forces during thermocompression bonding of the electrodes, and providing excellent electrical conductivity reliability.

The ratio of large silica particles to small silica particles is preferably 10 to 80 parts by weight, and more preferably 20 to 80 parts by weight, of small silica particles per 100 parts by mass of large silica particles, from the viewpoint of obtaining insulating particles with a higher coverage rate than silica particles with a smooth surface.

The silica particles having an uneven surface can be produced by a known method (for example, see JP-A-2013-227168).
For example, a particle binder is added to colloidal silica consisting of the large silica particles and the small silica particles to bond the small particles to the surfaces of the large particles, and active silicic acid is further added under heating to integrate the particles.

The binder may be an aluminum compound such as sodium aluminate or an aluminum halide compound. The amount of the aluminum compound to be added is calculated from the specific surface area of the large silica particles. For example, colloidal silica containing 100 g of 50 nm silica particles as SiO ₂ has a specific surface area of 54.4 ^{m 2} /g, so the total specific surface area is 5440 m ² , that is, 5.44×10 ²¹ nm ² , and the silanol group density is 8/nm ² , so the total number of silanol groups is 4.35×10 ²² , and if aluminate ions Al(OH) ^4- are bonded to 10% of the total silanol groups, the amount of aluminate ions is 4.35×10 21 , which is 0.0073 mol in molar terms, and the amount of sodium aluminate used as Al ₂ O ₃ is 0.74 g.

Activated silicic acid is then added to integrate the particles, and the amount of activated silicic acid added can be calculated based on the particle size of the larger silica particles. The amount of activated silicic acid added must contain enough silica to increase the particle size of the larger silica particles by 3 to 7 nm. If the amount of activated silicic acid added is less than 3 nm, the bonds are easily broken. If it is more than 7 nm, the degree of unevenness is small and the difference in performance with silica particles with a smooth surface becomes unclear. A value of 4 to 6 nm is more preferable.

The activated silicic acid is added under heating. This is the same as the build-up process for colloidal silica, where a mixture of two types of silica particles (large and small) and a binder is heated to 60-100°C, and while maintaining that temperature, the activated silicic acid is added at a rate that allows the silica component of the activated silicic acid to cover the combined large and small particles. While the activated silicic acid is being added, an alkaline agent is added at the same time to keep the pH of the solution at 9-11. Examples of alkaline agents that can be used include caustic soda, caustic potash, and tetramethylammonium hydroxide.
By doing so, it is possible to obtain silica particles having an uneven surface.

In the compound containing a charged functional group to be fixed to the surface of the silica particle having an uneven surface, the charged functional group may be one having a positive charge or one having a negative charge.
Examples of the positively charged functional group include a phosphonium group, an ammonium group, a sulfonium group, and an amino group.
Examples of the negatively charged functional group include a carboxyl group, a hydroxyl group, a thiol group, a sulfonic acid group, and a phosphate group.

In the present invention, the charged functional group is preferably a group selected from a phosphonium group, an ammonium group, a thiol group, and a sulfonic acid group, from the viewpoint of achieving even closer adhesion of the insulating particles to the conductive particles.

（式中、ＱはＰ原子又はＮ原子を示す。Ｘは一価のアニオンを示す。）
前記一般式（１）の式中、Ｒ^１、Ｒ^２、Ｒ^３及びＲ^４は、炭素数１～１８の直鎖状若しくは分岐鎖状のアルキル基、シクロアルキル基、アリル基、又はフェニル基を示す。また、Ｒ^１、Ｒ^２、Ｒ^３及びＲ^４はシリカ原子を含む基であってもよい。Ｒ^１、Ｒ^２、Ｒ^３及びＲ^４が、シクロアルキル基又はフェニル基の場合、例えば、４－メチルシクロヘキシル基、４－メチルフェニル基のように、シクロアルキル環又はベンゼン環の水素原子の一部が、アルキル基で置換されていてもよい。また、Ｒ^１、Ｒ^２、Ｒ^３及びＲ^４は、同一の基であっても異なる基であってもよい。また、Ｒ^１、Ｒ^２、Ｒ^３及びＲ^４は、炭素数１～１８の直鎖状若しくは分岐鎖状のアルキル基、シクロアルキル基、アリル基又はフェニル基の水素原子の一部が、ヒドロキシル基、アミノ基、アルコキシ基等の置換基で置換されている基であってもよい。 As the compound having a phosphonium group or an ammonium group, a compound represented by the following general formula (1) is preferable.

(In the formula, Q represents a P atom or a N atom, and X represents a monovalent anion.)
In the formula (1), R ¹ , R ² , R ³ and R ⁴ represent a linear or branched alkyl group, a cycloalkyl group, an allyl group, or a phenyl group having 1 to 18 carbon atoms. R ¹ , R ² , R ³ and R ⁴ may be a group containing a silica atom. When R ¹ , R ² , R ³ and R ⁴ are a cycloalkyl group or a phenyl group, some of the hydrogen atoms of the cycloalkyl ring or the benzene ring may be substituted with an alkyl group, such as a 4-methylcyclohexyl group or a 4-methylphenyl group. R ¹ , R ² , R ³ and R ⁴ may be the same group or different groups. R ¹ , R ² , R ³ and R ⁴ may be a linear or branched alkyl group, a cycloalkyl group, an allyl group, or a phenyl group having 1 to 18 carbon atoms, some of the hydrogen atoms of which are substituted with a substituent such as a hydroxyl group, an amino group, or an alkoxy group.

Examples of the anion of X include a benzotriazole ion, a fluorine ion, a chloride ion, a bromide ion, an iodide ion, BF ₄ ⁻ , PF ₆ ⁻ , PO ₂ (OMe) ₃ ⁻ , PS ₂ (OEt) ₂ ⁻ , (CO ₂ Me) ₂ PhSO ₃ ⁻ , CF ₃ SO ₃ ⁻ , HSO ₄ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ and the like, and the anions exemplified here are preferred in terms of ease of production.

（式中、ＱはＰ原子又はＮ原子を示す。Ｒ^５、Ｒ^６及びＲ^７は炭素数１～１８の直鎖状若しくは分岐状のアルキル基を示す。Ｒ^８は炭素数１～５の直鎖状若しくは分岐状のアルキル基を示す。ｎは１～５の整数を示す。Ｘはアニオン基を示す。） In the present invention, the compound having a preferred phosphonium group or ammonium group is preferably a phosphonium salt or ammonium salt represented by the following general formula (2). The phosphonium salt and ammonium salt having a silyl group represented by the general formula (2) have a hydrolyzable silyl group site. In the method for preparing silica particles having an ionic liquid fixed to the particle surface described below, the hydrolyzable site is hydrolyzed by an alkali in the same manner as alkoxysilane and directly bonds to the silica particles, which is preferable from the viewpoint of further improving adhesion to the metal coating.

(In the formula, Q represents a P atom or an N atom. R ⁵ , R ⁶ and R ⁷ represent a linear or branched alkyl group having 1 to 18 carbon atoms. R ⁸ represents a linear or branched alkyl group having 1 to 5 carbon atoms. n represents an integer of 1 to 5. X represents an anionic group.)

In general formula (2), Q represents a P atom or an N atom, and is preferably a P atom. In general formula (2), R ⁵ to R ⁷ preferably represent a linear or branched alkyl group having 1 to 5 carbon atoms. R ⁸ is preferably an alkyl group having 1 to 2 carbon atoms. n is preferably 2 to 4.
The type of anion for X is not particularly limited, and examples thereof include benzotriazole ion, fluorine ion, chloride ion, bromide ion, iodide ion, BF ₄ ⁻ , PF ₆ ⁻ , PO ₂ (OMe) ₃ ⁻ , PS ₂ (OEt) ₂ ⁻ , (CO ₂ Me) ₂ PhSO ₃ ⁻ , CF ₃ SO ₃ ⁻ , HSO ₄ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ and the like, with the anions exemplified here being preferred in terms of ease of production.

（式中、Ｒ^９及びＲ^１０は、炭素数１～５のアルキル基を示す。Ｚ_１はフェニレン基、炭素数１～５のアルキレン基を示す。Ｚ_２は、-（Ｃ＝Ｏ）Ｏ－を示す。Ｒ^１１は炭素数１～２０のアルキル基を示す。Ｘ^１は、アニオンを示す。） As the compound having a sulfonium group, a compound represented by the following general formula (3) is preferable.

(In the formula, R ⁹ and R ¹⁰ represent an alkyl group having 1 to 5 carbon atoms. Z ₁ represents a phenylene group or an alkylene group having 1 to 5 carbon atoms. Z ₂ represents —(C═O)O—. R ¹¹ represents an alkyl group having 1 to 20 carbon atoms. X ¹ represents an anion.)

The type of anion of ^X1 in the general formula (3) is not particularly limited, and examples thereof include a fluorine ion, a chloride ion, a bromide ion, an iodide ion, a perchlorate ion, a hydrogen sulfate ion, and a p-toluenesulfonate ion. The anions exemplified here are preferred in terms of ease of production.

The compound having a charged functional group selected from an amino group, a carboxyl group, a hydroxyl group, a sulfonic acid group, and a phosphoric acid group is preferably one represented by the following general formula (4).
R ¹² Si(OR ¹³ ) ₃ (4)

In the general formula (4), R ¹² represents a hydrocarbon group having 1 to 8 carbon atoms and having 1 to 3 functional groups having a charge selected from amino groups, carboxyl groups, hydroxyl groups, sulfonic acid groups, and phosphoric acid groups, an alicyclic hydrocarbon group having 1 to 3 functional groups having a charge selected from amino groups, carboxyl groups, hydroxyl groups, sulfonic acid groups, and phosphoric acid groups, or an aromatic hydrocarbon group having 6 to 8 carbon atoms and having 1 to 3 functional groups having a charge selected from amino groups, carboxyl groups, hydroxyl groups, sulfonic acid groups, and phosphoric acid groups. R ¹³ 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. Each of the R ¹² may be the same group or different groups.

The content of the compound having a charged functional group selected from a phosphonium group, an ammonium group, and a sulfonium group, or a condensate thereof (hereinafter sometimes referred to as a "compound having functional group 1") in the insulating particles is preferably 0.001 to 50 mass%, preferably 0.1 to 30 mass%, and more preferably 0.1 to 10 mass%, from the viewpoint of increasing adhesion to the metal coating.

The compound having functional group 1 can be fixed to silica particles having an uneven surface (hereinafter, sometimes referred to as "uneven silica particles") by adding an alkali to a reaction raw material liquid containing uneven silica particles, an alkoxysilane, a compound having functional group 1, and a reaction solvent to hydrolyze the alkoxysilane, and then carrying out a surface treatment process to perform surface treatment on the silica particles.

The uneven silica particles and the compound having functional group 1 used in the surface treatment process can be those described above.

Examples of alkoxysilanes used in the surface treatment process include tetraalkoxysilanes such as tetramethoxysilane and tetraethoxysilane, alkyltrialkoxysilanes such as methyltrimethoxysilane and methyltriethoxysilane, dialkyldialkoxysilanes such as dimethyldimethoxysilane and dimethyldiethoxysilane, and alkoxytrialkylsilanes such as hexyloxytrimethylsilane. The carbon chain length of the alkyl group in these alkoxysilanes is preferably 1 to 6. The carbon chain length of the alkoxy group is also preferably 1 to 6. Of these, tetraethoxysilane and tetramethoxysilane are preferred in terms of ease of handling in manufacturing. The alkoxysilanes may be used alone or in combination of two or more.

The reaction solvent used in the surface treatment step is one that dissolves alkoxysilane and a compound having functional group 1. Examples of reaction solvents used in the surface treatment step include lower alcohols such as methanol, ethanol, and isopropyl alcohol, and among these, methanol is particularly preferred from the viewpoint of high reaction efficiency. A mixed solvent of water and a lower alcohol may also be used.

The content of the silica particles having an uneven surface in the reaction raw material liquid is not particularly limited, but is preferably 1 to 80 mass%, and particularly preferably 3 to 50 mass%. When the content of the silica particles having an uneven surface in the reaction raw material liquid is within the above range, the dispersion stability of the silica particles having an uneven surface to which the compound having functional group 1 is fixed is increased.

The content of alkoxysilane in the reaction raw liquid is 0.05 to 1.5 mmol, preferably 0.08 to 1.05 mmol, per 1 g of uneven silica particles. By having the content of alkoxysilane in the reaction raw liquid within the above range, the fixation rate of the compound having functional group 1 to the uneven silica particle surface is increased.

The content of the compound having functional group 1 in the reaction raw liquid is 0.001 ml or more, preferably 0.005 to 1.5 ml, and particularly 0.01 to 1.0 ml per gram of uneven silica particles. By having the content of the compound having functional group 1 in the reaction raw liquid within the above range, the fixation rate of the compound having functional group 1 to the uneven silica particle surface is increased, and the adhesion with the metal coating is also increased.

In the surface treatment step, the alkali to be added to the reaction raw material liquid is not particularly limited as long as it can hydrolyze alkoxysilane. For example, examples of alkali include ammonium hydroxide, sodium hydroxide, potassium hydroxide, etc., but ammonium hydroxide is particularly preferred from the viewpoint of high reactivity and ability to obtain the target product with high purity.

The amount of alkali added to the reaction mixture is not particularly limited and may be selected as appropriate.

The reaction temperature when the alkali is mixed into the reaction liquid to hydrolyze the alkoxysilane is 15 to 60°C, preferably 20 to 35°C. By keeping the reaction temperature within the above range, the fixation rate of the compound having functional group 1 to the uneven silica particle surface is increased, and the adhesion to the metal film is also increased.

The reaction time is not particularly limited and may be selected appropriately, but is preferably 1 to 72 hours, and particularly preferably 1 to 24 hours.

After a surface treatment step in which an alkali is added to the reaction raw solution to hydrolyze the alkoxysilane, the solids are separated from the reaction solution by centrifugation or the like, and if necessary, the solids obtained are dispersed in a solvent and centrifuged again. This operation is repeated several times, and then the mixture is dried to obtain silica particles with irregularities on which a compound having functional group 1 is fixed to the particle surface.

In addition, after the surface treatment step, the reaction solution may be heated under normal or reduced pressure to a temperature at which the reaction solvent evaporates, and silica particles having an uneven surface and a compound having functional group 1 fixed to the particle surface may be recovered directly from the reaction solution.

When a compound having a phosphonium group or an ammonium group represented by the general formula (3) is used as the compound having functional group 1, the compound having a phosphonium group or an ammonium group has a hydrolyzable silyl group site, so that the surface treatment step may be performed without using an alkoxysilane in the surface treatment step.

When a compound having a phosphonium group or an ammonium group represented by the general formula (3) is used as the compound having functional group 1, what is fixed to the uneven silica particles is a condensate of the compound having a phosphonium group or an ammonium group represented by the general formula (3).

The content of the compound having a functional group with a charge selected from an amino group, a carboxyl group, a hydroxyl group, a sulfonic acid group, and a phosphate group, or a condensate thereof (hereinafter, sometimes referred to as a "compound having functional group 2") in the insulating particles is 0.1 to 10 mass%, preferably 1 to 5 mass%, which is preferable from the viewpoint of being able to uniformly coat the uneven surface of the silica particles.

The method of fixing the compound having functional group 2 to the uneven silica particle surface can be carried out by a wet method or a dry method. In addition, when a compound represented by general formula (5) is used as the compound having a functional group with a charge in the compound having functional group 2, the compound having functional group 2 fixed to the uneven silica particle surface may be a condensation product thereof.

When the compound represented by the general formula (5) is used to fix uneven silica particles by a wet method, examples of the fixing method include: 1) immersing uneven silica particles in a solvent containing a compound having functional group 2 at a desired concentration, heating if necessary to promote the reaction between the uneven silica particles and the compound having functional group 2, and then spray drying together with the solvent or performing solid-liquid separation and drying; 2) adding a compound having functional group 2 to a dispersion containing uneven silica particles and a solvent, heating to 50 to 100°C to cause a reaction, and then spray drying together with the solvent or performing solid-liquid separation and drying.

Solvents that can be used in the wet method include alcohols such as methanol, ethanol, and propanol, or mixtures of these alcohols with water.

When a compound having functional group 2 is used to perform a dry fixation process on uneven silica particles, examples of the fixation method include a method of dry mixing the compound having functional group 2 and the uneven silica particles using a mechanical means such as a Henschel mixer or an airflow grinder, or a method of diluting the compound having functional group 2 with a solvent, mixing the diluted solution with the uneven 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.

In the case of a compound in which R ¹² in the formula (3) is a sulfonic acid group, a condensate of the compound in which R ¹² in the formula (3) is a mercapto group may be fixed to the silica particles having irregularities as described above, and then the mercapto group may be converted to a sulfonic acid group by oxidation treatment with an oxidizing agent in a solvent.

Solvents that can be used include alcohols such as methanol, ethanol, and propanol, or mixtures of these alcohols with water.

Usable oxidizing agents include hydrogen peroxide, peracetic acid, and perbenzoic acid, and it is particularly preferable to use hydrogen peroxide from the viewpoint of obtaining a product of high purity.
The amount of the oxidizing agent added is preferably 2 to 6 moles per mole of the compound having functional group 2, from the viewpoint of minimizing the amount of residual oxidizing agent.
The temperature for the oxidation reaction is not particularly limited, but is usually 5 to 100° C., preferably 20 to 100° C. The reaction time varies depending on the reaction temperature, but is usually 1 hour or more, preferably 2 to 40 hours.

(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.

When mixing insulating particles and conductive particles in a liquid medium, a dispersion liquid containing insulating particles may be mixed with conductive particles, a dispersion liquid containing conductive particles may be mixed with insulating fine particles, or insulating particles and conductive particles may be added to a solvent, or a dispersion medium containing insulating particles may be mixed with a dispersion medium containing conductive particles. In a dispersion liquid containing conductive particles and insulating particles, the conductive particles are preferably contained in an amount of 100 ppm or more and 100,000 ppm or less by mass, and more preferably 500 ppm or more and 80,000 ppm or less.

In a dispersion liquid containing conductive particles and insulating particles, the insulating particles are preferably contained in an amount of 10 ppm or more and 50,000 ppm or less by mass, and more preferably 250 ppm or more and 10,000 ppm or less.

In the dispersion liquid after mixing the conductive particles, the time for the insulating particles to adhere to the conductive particles is preferably 0.1 hours or more and 24 hours or less. During this time, it is preferable to stir the dispersion liquid. Next, the solid content of the dispersion liquid is washed and dried as necessary to obtain coated particles in which the insulating particles are adhered to the surfaces of the conductive particles.

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 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.

When the insulating particles and the conductive particles are mixed in a solvent, the dispersion liquid consisting of these particles and the solvent may contain an inorganic salt, an organic salt or an organic acid as necessary for the purpose of increasing the coverage of the insulating particles. As the inorganic salt, organic salt or organic acid, one that dissociates an anion is preferably used, and as this anion, Cl ^- , F ^- , Br ^- , I ^- , SO ₄ ^2- , CO ₃ ^2- , NO ₃ ^- , COO ^- , RCOO ^- (R is an organic group), etc. are preferred. Examples of inorganic salts that can be used include 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 , _MgNO3 , _{and BaNO3} . As the organic salt, sodium succinate, sodium oxalate, sodium acetate, sodium citrate, sodium malonate, sodium tartrate, sodium fumarate, sodium maleate, etc. As the organic acid, 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.

The preferred concentrations of inorganic salts, organic salts, and organic acids vary depending on the extent to which the insulating particles occupy a surface area of the conductive particles, but in a dispersion containing insulating particles and conductive particles, a concentration of, for example, 5 mmol/L to 100 mmol/L is preferred because it has a suitable coverage rate and makes it easy to obtain coated particles in which the insulating particles are a single layer. From this perspective, the concentrations of inorganic salts, organic salts, and organic acids in the dispersion are more preferably 7 mmol/L to 90 mmol/L, and particularly preferably 10 mmol/L to 80 mmol/L.

When an inorganic salt, an organic salt, or an organic acid is added to a dispersion liquid containing conductive particles and insulating particles, a temperature of 20°C or higher and 100°C or lower is generally preferred in that coated particles of consistent quality can be easily obtained, and a temperature of 40°C or higher and 90°C or lower is particularly preferred. This range is preferred because it is easy to obtain a suitable contact area between the insulating particles and the conductive particles.

The coated particles of the present invention may also be obtained by a method in which a compound having, in the same molecule, a functional group (A) that is reactive with the metal film in the conductive particle and a functional group (B) that is reactive with the charged functional group in the compound containing a charged functional group contained in the insulating particle (hereinafter sometimes referred to as a "reactive compound") is reacted with the metal film 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 silane groups, silanol groups, carboxyl groups, amino groups, ammonium groups, nitro groups, hydroxyl groups, carbonyl groups, thiol groups, sulfonic acid groups, sulfonium groups, boric acid groups, oxazoline groups, pyrrolidone groups, phosphate groups, and nitrile groups.

The functional group (B) varies depending on the type of compound or condensate thereof that contains a functional group having an electric charge to be fixed to the uneven silica particles. For example, in the case of a compound having a mercapto group, examples of the compound containing a functional group having an electric charge 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.

In the case of a compound having a sulfonic acid group as a compound containing a functional group having a charge, examples of the functional group (B) include an epoxy group, an amino group, a hydroxyl group, an isocyanate group, an oxazoline group, a carbodiimide group, and a halogen group.

When the compound containing a functional group having a charge is a compound having a phosphonium group or an ammonium group, the functional group (B) may be, for example, an amino group, a halide group, a hydroxyl group, a carboxyl group, a sulfonic acid group, a phosphonic acid group, or a phosphate 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 the solid content 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 for 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))

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-based compounds, titanate-based coupling agents, higher fatty acids and their derivatives, phosphates, 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 bonded to the conductive particles 1) via a hydrophobizing agent present on the particle surface of the conductive particles, or 2) 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（４）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（４）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 (4).

(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 (4), 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 (4), 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 (4) 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 are each an alkyl group, an alkyl group in which a methylene group other than the terminal one is substituted with an oxygen atom, an alkenyl group, or an alkenyl group in which a methylene group other than the terminal one is substituted with an oxygen atom. B ⁹ is an alkyl group.)
In the above-mentioned formula (i), two or three groups among B ¹ to B ⁴ may be the same, or B ¹ to B ⁴ may all be different. In the compound represented by formula (ii), 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 ^9s may be the same or different. In the compound represented by formula (i), the number of alkanoyl groups, dialkyl pyrophosphate 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 the above alkyl groups in which one or more of the carbon-carbon single bonds 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, it may be present on the entire surface of the conductive particle, or may be present only on a part of the surface. In addition, the hydrophobizing agent may form a layer that covers a part or the entire surface of the conductive particle.

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.

The dispersion liquid after the treatment is filtered and, if necessary, dried to obtain conductive particles having a hydrophobizing agent on the surface thereof.
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 coated 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 agent 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, amine imides, 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 Dispersion Containing Uneven Silica Particles>
117 g of JIS No. 3 sodium silicate ( _SiO2 : 29.0%, _Na2O : 9.7%, _H2O : 61.3%) was added to 733 g of deionized water and mixed uniformly to prepare diluted sodium silicate containing 4.0% _SiO2 . This diluted sodium silicate was passed through a column of H-type strongly acidic cation exchange resin that had been regenerated with hydrochloric acid in advance to dealkalize it, obtaining 900 g of active silicic acid with a silica concentration of 3.5% and a pH of 2.9.
217g of large-particle colloidal silica with a silica concentration of 41% and a particle size of 80 nm was mixed with 2783g of deionized water to obtain a diluted large-particle colloidal silica with a silica concentration of 3%. Separately, 20g of small-particle colloidal silica with a silica concentration of 15% and a particle size of 7 nm was mixed with 280g of deionized water to obtain a diluted small-particle colloidal silica with a silica concentration of 1%. The diluted small-particle colloidal silica was added to the diluted large-particle colloidal silica under stirring. Next, 26g of a solution in which 2.6g of aluminum chloride hexahydrate ( _AlCl3.6H2O ) was dissolved in _23.4g of deionized water was mixed. The entire solution was mixed and stirred for 30 minutes, then heated to 98°C, and this temperature was maintained for 1 hour, after which 900g of active silicic acid and 81g of 1% caustic soda were added over 1.6 hours. The temperature was kept at 98°C during the addition, and after the addition was completed, the mixture was heated to 98°C and kept at this temperature for 1 hour, and then allowed to cool to 50°C. The obtained colloidal silica dispersion was subjected to pressure filtration by pump circulation using a hollow fiber ultrafiltration membrane (Microza UF module SIP-1013, manufactured by Asahi Kasei Corporation) with a molecular weight cutoff of 6000, to obtain about 400 g of uneven silica with a silica concentration of 30%. TEM images of this colloidal silica showed that the particle surfaces were uneven, and the average particle size determined from the TEM was 99 nm.
The average particle size measured by TEM was determined by randomly selecting 50 particles, measuring their particle sizes, and averaging the measurements.
FIG. 1 shows a TEM photograph of the resulting silica particles having projections and recesses.

<Preparation of insulating particle samples>
(Insulating Particle 1)
In a reaction vessel, 45 g of methanol was added to 58.2 g of the dispersion containing the uneven silica particles obtained above (SiO2: 30 mass%, water: 70 mass%) to obtain a dispersion. Next, 0.15 g of 3-mercaptopropyltrimethoxysilane was added to the dispersion with stirring, and the mixture was stirred for 20 minutes.
Then, the temperature of the reaction vessel was raised to 60° C., and the mixture was 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 1 in which the surfaces of the uneven silica particles were surface-treated with 3-mercaptopropyltrimethoxysilane.

(Insulating Particles 2)
Into a reaction vessel, 45 g of methanol was added to 58.2 g of the dispersion containing the uneven silica particles obtained above (SiO ₂ : 30 mass %, water: 70 mass %) to obtain a dispersion. Next, 0.15 g of 3-mercaptopropyltrimethoxysilane was added to the dispersion with stirring, and the mixture was stirred for 20 minutes.
Then, the temperature of the reaction vessel was raised to 60° C. and the mixture was stirred for 3 hours to complete the reaction.
Next, the reaction solution was cooled to room temperature (25° C.), and 0.25 g of 31% by weight hydrogen peroxide solution was added thereto, followed by reaction for 5 hours while boiling.
After the reaction was completed, the solids were recovered by filtration, washed with methanol, and dried at 120°C under vacuum for 12 hours to obtain silica particles with irregularities in which a condensate of a silane coupling agent having a sulfonic acid group was fixed to the particle surface via a chemical bond, which was designated as insulating particles 2.

容器に、メタノール２００ｍｌを入れ、次いで、化合物（ａ）０．５ｍｌ、上記で得られた凹凸のあるシリカ粒子を含む分散液（ＳｉＯ_２：３０質量％、水：７０質量％）５８．２ｇを添加し分散液を得た。次いでテトラエトキシシラン２３ｍｍｏｌを入れ、撹拌混合した。次いで、十分に撹拌しながら、２５％アンモニウム水５ｍｌを加え、３０℃でそれぞれ一晩撹拌した後、濃縮した。濃縮後、固形分にメタノールを入れ、一晩撹拌して固形分を分散させた後、遠心分離を行うという操作を２回繰り返し、精製を行った。精製後の固形分を、減圧デシケーター内で真空乾燥させ、化合物（ａ）の反応残基を固定した凹凸のあるシリカ粒子を得た。
また、得られた化合物（ａ）の反応残基を固定した凹凸のあるシリカ粒子について、元素分析をおこなったところ、化合物（ａ）の反応残基の含有量は３．０質量％であった。これを絶縁性粒子３とした。 (Insulating Particles 3)
As the compound containing a functional group having a charge, the following compound (a) was used.

200 ml of methanol was added to a container, and then 0.5 ml of compound (a) and 58.2 g of the dispersion containing the uneven silica particles obtained above (SiO ₂ : 30% by mass, water: 70% by mass) were added to obtain a dispersion. Then, 23 mmol of tetraethoxysilane was added and mixed by stirring. Then, 5 ml of 25% ammonium water was added while stirring thoroughly, and the mixture was stirred at 30° C. overnight, and then concentrated. After concentration, methanol was added to the solid content, and the solid content was dispersed by stirring overnight, and then centrifuged. This operation was repeated twice to purify the solid content after purification. The purified solid content was vacuum-dried in a reduced pressure desiccator to obtain uneven silica particles with the reaction residue of compound (a) fixed thereto.
Furthermore, elemental analysis of the resulting silica particles having irregularities and having the reaction residue of compound (a) fixed thereto revealed that the content of the reaction residue of compound (a) was 3.0% by mass. These were designated insulating particles 3.

容器に、メタノール２００ｍｌを入れ、次いで、化合物（ｂ）０．５ｍｌ、上記で得られた凹凸のあるシリカ粒子を含む分散液（ＳｉＯ_２：３０質量％、水：７０質量％）５８．２ｇを添加し分散液を得た。次いでテトラエトキシシラン２３ｍｍｏｌを入れ、撹拌混合した。次いで、十分に撹拌しながら、２５％アンモニウム水５ｍｌを加え、２５℃で５時間撹拌し反応を行った。反応終了後、反応液を減圧下に５０℃で蒸留し溶媒を除去し化合物（ｂ）の反応残基を固定した凹凸のあるシリカ粒子を得た。また、得られた化合物（ｂ）の反応残基を固定した凹凸のあるシリカ粒子について、元素分析をおこなったところ、化合物（ｂ）の反応残基の含有量は２．０質量％であった。 (Insulating Particles 4)
As the compound containing a functional group having a charge, the following compound (b) was used.

200 ml of methanol was placed in a container, and then 0.5 ml of compound (b) and 58.2 g of the dispersion containing the uneven silica particles obtained above (SiO ₂ : 30% by mass, water: 70% by mass) were added to obtain a dispersion. Then, 23 mmol of tetraethoxysilane was added and mixed by stirring. Then, while stirring thoroughly, 5 ml of 25% ammonium water was added, and the reaction was carried out by stirring at 25° C. for 5 hours. After the reaction was completed, the reaction solution was distilled under reduced pressure at 50° C. to remove the solvent, and uneven silica particles with the reaction residue of compound (b) fixed were obtained. In addition, elemental analysis was performed on the obtained uneven silica particles with the reaction residue of compound (b) fixed, and the content of the reaction residue of compound (b) was 2.0% by mass.

(Insulating Particles 5)
Except for not adding tetraethoxysilane, silica particles having projections and recesses and having reaction residues of compound (b) fixed thereto were obtained in the same manner as insulating particles 4. Furthermore, elemental analysis was performed on the obtained silica particles having projections and recesses and having reaction residues of compound (b) fixed thereto, and the content of reaction residues of compound (b) was found to be 2.2% by mass.

(Insulating Particles 6)
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.

(Insulating Particles 7)
Insulating particles 7 were obtained in which the surfaces of the silica particles were surface-treated with 3-mercaptopropyltrimethoxysilane in the same manner as insulating particles 1, except that a dispersion containing commercially available colloidal silica (SiO ₂ : 30% by mass, water: 70% by mass) was used instead of a dispersion containing uneven silica particles (SiO ₂ : 30% by mass, water: 70% by mass).
According to a TEM image, this colloidal silica was spherical and had an average particle size of 95 nm.
The average particle size measured by TEM was determined by randomly selecting 50 particles, measuring their particle sizes, and averaging the measurements.

(Insulating Particles 8)
Except for using a dispersion liquid containing commercially available colloidal silica (SiO ₂ : 30 mass %, water: 70 mass %) instead of the dispersion liquid containing uneven silica particles (SiO ₂ : 30 mass %, water: 70 mass %), silica particles having a condensate of a silane coupling agent having a sulfonic acid group fixed to the particle surface via a chemical bond were obtained in the same manner as for insulating particles 2, and these were designated as insulating particles 8. TEM images showed that this colloidal silica was spherical and had an average particle diameter of 95 nm.
The average particle size measured by TEM was determined by randomly selecting 50 particles, measuring their particle sizes, and averaging the measurements.

<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 for 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 conductive layer of gold-nickel 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 1-2 and Reference Examples 1-2}
Pure water was added to prepare an insulating particle dispersion liquid so that the solid content of the insulating particles obtained above was 10,000 ppm and the total volume was 20 ml. 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.

{Examples 3 to 9}
100 ml of pure water was added to 5.0 g of the conductive particles, and the mixture was stirred to obtain a dispersion of conductive particles. The insulating particles and _Na2SO4 prepared above were added to this dispersion, and the mixture was stirred at 40°C for 30 minutes _. After the insulating particles and _Na2SO4 were added, the solid content concentration of the insulating _particles in the dispersion was 10,000 ppm by mass, and the concentration of _Na2SO4 was 5 mmol/ _l . After removing the supernatant, the mixture was washed with pure water and then vacuum dried at 50°C, and this was used as a coated particle sample.

{Comparative Example 1}
The insulating particle dispersion liquid was prepared by adding pure water and NaCl to the insulating particles 6 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 the 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 using 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 evaluated by calculating the degree of adhesion using the following formula, 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 10}
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 4 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 4 were added, the solid-liquid concentration of the insulating particles 4 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 9, and the results are shown in Table 2.

{Example 11}
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 4 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 4 were added, the solid-liquid concentration of the insulating particles 4 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 (8)

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 insulating particle being characterized in that a compound or a condensation product thereof containing a functional group having an electric charge is fixed to the surface of a silica particle having an uneven surface, and the silica particle having an uneven surface is a particle in which a smaller silica particle is bonded to the surface of a larger silica particle . The coated particles according to claim 1, characterized in that the core particles are 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 particle according to any one of claims 1 to 4, characterized in that the charged functional group is a group selected from a phosphonium group, an ammonium group, a mercapto group, and a sulfonic acid group. The coated particles according to any one of claims 1 to 5, characterized in that the conductive particles are surface-treated with a hydrophobizing agent. The coated particles according to claim 6, characterized in that the hydrophobizing agent is a benzotriazole-based compound or a titanate-based coupling agent. A conductive material comprising the coated particles according to any one of claims 1 to 7 and an insulating resin.