JPH08297295A - Conductive fine particle and its production - Google Patents

Abstract

PURPOSE: To obtain fine particles excellent in accuracy of particle diameter conductivity and having high strength, high hardness and high durability by subjecting spherical particles of metal oxide to surface treatment with a silane coupling agent and coating the surface of the surface-treated particles with a polymer layer having conjugate π-electrons. CONSTITUTION: The conductive fine particles are produced by surface treating spherical particles of metal oxide with a silane coupling agent having polymerizable functional groups and then coating the surface of the spherical particles with a polymer (conductive polymer) having conjugate π-electrons. The spherical particles of metal oxide as the base body of the conductive fine particles are spherical particles of silica, alumina, titania, zirconia or composite material of these. These particles are produced by hydrolysis of silicon alkoxide to obtain monodispersion silica fine particles having a sharp distribution of particle diameter. The particle diameter of the particles is usually 0.1-30.0μm, and preferably 0.5-15.0μm, and more preferably 0.8-12μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to conductive fine particles which can be used for anisotropic conductive films and the like and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, a semiconductor chip or a lead wire of a liquid crystal display device and a connecting portion of a drive circuit (LSI or the like) thereof are connected to each other by forming a bump or a carrier tape. Has been done by the method of using. However, these methods are unsuitable for forming a more compact connecting portion. Therefore, at present, anisotropic conductive films capable of forming finer connection parts have been used.

The anisotropic conductive film is composed of two films having terminals provided at a distance corresponding to the distance between the lead wires, with the surfaces on which the terminals are provided facing inward, respectively, and the conductive film between them. It is prepared by inserting a dispersion liquid of particles having the above, pressing the film under pressure, and sandwiching conductive particles between the terminals facing each other. The anisotropic conductive film manufactured in this manner ensures conductivity between the upper and lower terminals, but has no conductivity between adjacent terminals on the left and right, and maintains an insulating state.

Conventionally, as conductive particles for producing an anisotropic conductive film, there has been one in which the surface of resin beads is plated with a metal such as nickel or gold, but these have the following problems. I was holding. That is, (a) the particle size accuracy of the conductive fine particles is greatly influenced by the particle size accuracy of the resin beads that are the mother particles, but the particle size accuracy of the resin beads is generally poor, and the resulting conductive particles are The particle size accuracy of is also poor.

(B) A large amount of agglomeration of resin beads as mother particles occurs during the plating process, and when the electroconductive fine particles obtained after plating are used, the agglomerated portion is crushed. Incomplete plating may cause poor conduction.

(C) Since the resin beads have insufficient hardness and strength, conductive fine particles containing resin beads as the mother particles cannot be used for applications requiring higher strength and hardness.

Although fine particles of metal such as nickel itself may be used as the conductive fine particles, they are easily agglomerated and the insulation between terminals cannot be secured in many cases.

Further, conductive fine particles obtained by plating fine particles of metal oxide with nickel and / or gold have been proposed, but these are also easily aggregated and the adhesion between the mother particles and the coating metal is poor. In some cases, the coated metal part may fall off during the crushing or kneading process, resulting in a marked decrease in conductivity.

Therefore, an object of the present invention is to provide a novel conductive fine particle having high strength, high hardness and high durability which is excellent in particle size accuracy and conductivity, and a method for producing the same.

[0010]

Means for Solving the Problems The conductive fine particles of the present invention which achieve the above object are conjugated π on the surface of spherical particles composed of a metal oxide surface-treated with a silane coupling agent having a polymerizable functional group. A layer made of a polymer having electrons (hereinafter, abbreviated as a conductive polymer) is coated.

Further, the method for producing electrically conductive fine particles of the present invention which achieves the above object is obtained by conjugating a dispersion liquid containing spherical particles made of a metal oxide surface-treated with a silane coupling agent having a polymerizable functional group. A monomer capable of forming a polymer having π electrons is added and oxidatively polymerized to form a polymer layer having conjugated π electrons (hereinafter abbreviated as a conductive polymer layer) on the surface of spherical particles made of a metal oxide. Is characterized by.

First, the conductive fine particles of the present invention will be described.

As the spherical particles made of a metal oxide, which is the base material of the conductive fine particles of the present invention, spherical particles made of a metal oxide such as silica, alumina, titania, zirconia or a complex thereof are used. Of these, it is particularly preferable to use spherical particles made of silica having a very sharp particle size distribution. Although the spherical silica particles can be produced by various methods, a particularly preferable method is a method of hydrolyzing silicon alkoxides to obtain monodispersed silica fine particles having a sharp particle size distribution. The particle size of the silica fine particles is usually 0.1 to 30.0 μm, preferably 0.5 to 15.0 μm, and particularly preferably 0.1.
It is 8 to 12 μm. The variation coefficient of the particle size distribution of the silica fine particles (hereinafter referred to as CV value) is 2% or less of CV.
It may be any value as long as the conductive fine particles having a certain value can be obtained.

The coefficient of variation (CV value) is obtained by the following equation. CV value (%) = (standard deviation of particle size) ÷ (average particle size) × 1
50 The silane coupling agent having a polymerizable functional group for surface-treating the metal oxide spherical particles (hereinafter, abbreviated as silane coupling agent) is a vinyl group or an allyl group on the surface of the metal oxide. Any one that can introduce a polymerizable functional group such as an acryloyl group, a methacryloyl group, and a glycidoxy group may be used. Specific examples thereof include trimethoxyvinylsilane, triethoxyvinylsilane, allylmethoxysilane, allyltriethoxysilane, vinyltris (β-methoxyethoxy) silane,
Methylvinyldichlorosilane, γ- (meth) acryloxypropyltrimethoxysilane, vinyltrichlorosilane, vinyltris (β-methoxy) silane, γ-methacryloxypropyltrimethoxysilane, N-β (N-vinylbenzylaminoethyl) -γ -Aminopropyltrimethoxysilane, vinyltriacetoxysilane, γ-methacryloxypropylmethyldimethoxysilane, and other vinylsilane coupling agents; β- (3,4-epoxycyclohexyl) ethyltriethoxysilane, γ-glycidoxypropyltri Examples thereof include epoxysilane coupling agents such as methoxysilane, γ-glycidoxypropylmethyldimethoxysilane, and methyltri (glycidyloxy) silane. The silane coupling agent having a polymerizable functional group may be only one kind or plural kinds.

The amount of the silane coupling agent with respect to the metal oxide is such that the polymerizable functional group introduced on the surface of the metal oxide spherical particles reacts with a monomer capable of forming a polymer having a conjugated π electron as described later. It is necessary to make the amount capable of forming a polymer coating layer having excellent adhesiveness on the surface of the oxide spherical particles, but more specifically, in the charged amount during the surface treatment, silane is used for the entire surface of the spherical particles of the metal oxide. The amount of the system coupling agent is preferably 0.01 to 10 mmol / m ² per unit area, and more preferably 0.1 to 5 mmol / m ^2.
It is preferably m ² .

Alkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane and tetrabutoxysilane may be used together with the silane coupling agent. When the alkoxysilane is used in combination, it is preferable to charge the alkoxysilane simultaneously with the silane coupling agent or before the silane coupling agent, and the latter is particularly preferable. The amount of alkoxysilane used is 0.5 in terms of molar ratio to the silane coupling agent.
The following is preferable, and 0.25 or less is particularly preferable.

In the conductive fine particles of the present invention, the surface of the spherical particles made of the metal oxide surface-treated with the above-mentioned silane coupling agent is coated with a layer made of a polymer having conjugated π electrons. Is characterized by.

A polymer having a conjugated π electron (conductive polymer) has the formula R _x —C ₆ H _(5-x) —NH (R ¹ ) (I) (wherein R is the ortho position of the aromatic ring and / or Or a C ₁ -C ₁₈ alkyl group substituted in the meta position or a halogen atom, x represents the number of R, is 0 to 4, and R ¹ is hydrogen or a C _{1 to} C ₁₈ alkyl group). Polymers obtained by polymerizing the indicated aniline or its derivatives, or formulas

Embedded image (In the formula, R ² and R ³ are each independently hydrogen, a C _{1 to} C ₁₈ alkyl group, a C _{1 to} C ₁₈ alkoxy group or a halogen atom, and X is an NH group, a sulfur or an oxygen atom) It is preferably a polymer obtained by polymerizing pyrrole, thiophene, furan or a derivative thereof.

The concentration of the monomer, that is, the aniline represented by the above formula (I) or its derivative, or the pyrrole, thiophene, furan or its derivative represented by the above formula (II), is in the range of 1 to 1000 mmol / liter. Yes, and preferably within the range of 2 to 100 mmol / liter.

The electric conductivity of the conductive fine particles of the present invention varies depending on the substituents of the monomers used and the doping ratio, but it is 10 ^-9.
To 100 S (Siemens) / cm, preferably 10 ^{−6 to} 50 S / cm.

Next, the method of the present invention for producing conductive fine particles will be described.

In the present invention, spherical particles composed of a metal oxide surface-treated with a silane coupling agent having a polymerizable functional group are used as starting materials.

The surface treatment of the spherical particles made of metal oxide with the silane coupling agent is carried out as follows. First, using ultrasonic vibration or the like, spherical particles are dispersed in an alcohol solvent such as methanol, ethanol, or 2-propanol to obtain a desired dispersion liquid. The solvent at this time may be one type of alcohol or a mixture of a plurality of types of alcohol. The amount of the alcohol solvent is preferably 5 to 30 times that of the spherical particles. In the dispersion liquid thus obtained, 2 to the weight of the spherical particles is used.
25 to 30% of 30-fold ammonia water is added, and further a silane coupling agent is added. If necessary, add a small amount (0.5 in molar ratio to the silane coupling agent).
The following) alkoxysilanes may be preferably added before or during the addition of the silane coupling agent. The purpose of adding the alkoxysilane is to make the amount of the silane coupling agent bonded to the surface of the silica fine particles uniform by allowing the alkoxysilane having a high hydrolysis rate to coexist. Specific examples of the silane coupling agent and the alkoxysilane are as exemplified in the above description of the conductive fine particles of the invention. After that, the liquid temperature of the dispersion liquid is set to 20
Stir for 1 to 24 hours while maintaining at ~ 80 ° C. As a result, the spherical particles are surface-treated with the silane coupling agent, and a polymerizable functional group is introduced on the surface of the spherical particles.

In the method for producing conductive fine particles of the present invention, a monomer capable of forming a polymer having conjugated π-electrons is added to a dispersion liquid containing spherical oxide particles surface-treated with a silane coupling agent to carry out oxidative polymerization. Then, a polymer layer having conjugated π electrons in a doped state is formed on the surface of the spherical particles made of a metal oxide.

This polymer layer forming step employs oxidative polymerization, and basically, POLYMER and 199 are used.
1 year, Vol. 32, No. 13, pages 2325 to 2330. However, according to the method of this document, silica particles are directly dispersed in a medium containing an oxidation catalyst and the like without any surface treatment, and monomers such as aniline and pyrrole are injected into the obtained dispersion liquid to carry out oxidative polymerization. In the method described in this document, (i) the silica particles are aggregated during the polymerization, and it is not possible to form a uniform conductive polymer layer on the particle surface. Electrical conductivity required for particles used for a conductive film (hereinafter abbreviated as electrical conductivity) (10
^-2 to 10 ^-3 S / cm) cannot be sufficiently satisfied, (ii) conductive fine particles having a uniform particle size distribution cannot be obtained, (iii) no chemical bond with silica fine particles,
Due to physical adsorption, the conductive polymer layer is very easily peeled off. (Iv) When the silica particles are large particles having a particle size of, for example, more than 1 μm, the polymer layer can hardly be formed on the silica particles. It has drawbacks.

Therefore, in the method of the present invention, as the metal oxide spherical particles for forming the polymer layer, those surface-treated with the silane coupling agent having a polymerizable functional group are used, and the metal oxide spherical particles are used. The polymerizable functional group in the silane coupling agent bonded on the surface of the is involved in the oxidative polymerization of the monomer capable of forming the polymer having the conjugated π electron, and the polymerizable functional group is the polymer having the conjugated π electron. By chemically bonding with, the drawbacks (i), (ii), (iii) and (iv) of the method described in the above literature are solved. That is, by surface-treating the metal oxide spherical particles with a silane coupling agent, aggregation of the spherical particles is prevented, and by interposing a silane coupling agent between the spherical particles and the polymer layer, Even if the spherical particles have a large diameter, it is possible to form a polymer layer having a uniform and excellent adhesion on the spherical particles. By the surface treatment with a silane coupling agent, the reason why the aggregation of spherical particles is prevented is because the terminal of the silane coupling agent bonded to the surface of the silica particles is an organic group such as a vinyl group, Since it has hydrophobicity, it is considered to prevent particles from repulsing each other and coalescing.

Examples of the monomer capable of forming a polymer having conjugated π electrons include aniline represented by the above formula (I) or a derivative thereof or pyrrole, thiophene, furan or a derivative represented by the above formula (II).

The concentration of the monomer in the dispersion in the oxidative polymerization is not critical, but preferably 1 to 1000 mmo.
It is in the range of 1 / liter, particularly preferably 2 to 100.
It is in the range of mmol / liter.

The medium of the dispersion liquid is not particularly limited as long as it is a solvent used in general oxidative polymerization, and specifically, water; alcohols such as methanol, ethanol and isopropyl alcohol; nitriles such as acetonitrile and benzonitrile. Examples include system solvents. Further, a plurality of these solvents may be mixed and used, and 0.01 to 10 mol / liter of hydrogen halides such as sulfuric acid, nitric acid and hydrochloric acid, and protic acid such as perchloric acid are added to these solvents. Can also be used as a medium.

The oxidizing agent at the time of polymerization is not particularly limited as long as it can oxidize a monomer, but specifically, salts of trivalent iron such as iron trichloride; divalent copper including cupric chloride. Examples thereof include persulfates such as ammonium persulfate and potassium persulfate. The amount of the oxidizing agent added is in the range of 0.01 to 100 times by mole, and more preferably in the range of 0.1 to 10 times by mole with respect to the monomer. In this case, the dopant anion doped in the obtained conductive film becomes the transition metal compound or the protonic acid of the added oxidizing agent.

In addition to the above-mentioned oxidizing agents, salts of halogen anions such as tetraethylammonium, tetra-n-butylammonium and tetra-n-propylammonium, electrolyte anions such as fluoroborate anions and perchlorate anions are added in an amount of 0.01 to Polymerization can also be carried out by adding to the reaction solvent at a concentration of 10 mol / liter. In this case, the dopant anion doped in the obtained conductive coating becomes the electrolyte anion added here.

According to a particularly preferred embodiment of the method of the present invention, by adding a dispersion stabilizer to the dispersion liquid, the agglomeration of the metal oxide spherical particles is further enhanced before, during and after the formation of the polymer layer. Since it is prevented and the dispersion state of the spherical particles and the monomer is maintained more uniformly, it is possible to obtain monodisperse spherical particles having a uniform polymer coating layer.

As the dispersion stabilizer for forming a uniform polymer without particles agglomerating, polyvinylpyrrolidone, polyvinylmethyl ether, polyethyleneimine, polyacrylic acid, polyvinyl alcohol, ethyl cellulose, methyl cellulose, hydroxypropyl cellulose, acrylic Resin, polycarbonate, etc. may be mentioned.

The amount of the dispersion stabilizer added was 0.
02 to 20% by weight is preferable, and 0.2 to 6% by weight is particularly preferable. If the addition amount is less than 0.02% by weight, the silica fine particles agglomerate and coalesce, making it impossible to obtain conductive fine particles having a uniform particle size distribution. On the other hand, if the amount added is more than 20% by weight, the conductive polymer cannot be uniformly coated, and the electric conductivity tends to decrease.

Here, the reaction mechanism of the oxidative polymerization reaction by the dispersion polymerization method for forming the conductive polymer coating layer will be described by taking aniline as an example. First, aniline is oxidized and the para position of the aromatic ring becomes a cation. The generated cation attacks the N-unpaired electron of aniline, and head-tail type coupling occurs. In the case of a conductive polymer, the easiness of oxidation is in the order of monomer <dimer <trimer <... Polymer, so that the polymer is sequentially oxidized and polymerized. On the other hand, the oxidized cationic aniline attacks electron-rich vinyl groups to form bonds. Similarly, the aniline bound to the vinyl group is gradually polymerized (grafted). Precipitated polymer is several nm
The particles are particles having a particle size of several tens of nanometers and gather on the surface of the seed particles (polyaniline graft particles) in a form where the polyanilines attract each other, and are further oxidized to form a bond with the surface to form a coat layer.

The above oxidative polymerization reaction in the case where the monomer is aniline is represented by the following reaction formula.

[Chemical 4] Also, the monomer

Embedded image In the case of, R ² = R ³ = hydrogen atom, X = NH
The oxidative polymerization reaction in the case of a group, that is, in the case of a pyrrole is represented by the following reaction formula.

[Chemical 6]

The dopant anion (electron-accepting dopant) doped in the conductive polymer obtained by the chemical oxidative polymerization as shown in the above polymerization reaction formula was used in the polymerization reaction as described above. It is, for example, a transition metal compound, a protic acid or an electrolyte anion derived from an oxidant or a salt of the electrolyte anion added during the polymerization reaction. However, the conductive polymer obtained by the above-mentioned oxidative polymerization can be dedoped once and then redoped to obtain a conductive polymer having a different dopant anion. The re-doping method includes a chemical doping method and an electrochemical doping method, and any method may be used. Examples of the chemical doping method include a method of exposing a dry dedoped polymer to iodine gas and the like, and a method of stirring in a solution of a protonic acid (which may be a polymer sulfonic acid). The electrochemical doping method is
Put the polymer in the undoped state in the cell containing the solution obtained by dissolving the electrolyte in a suitable solvent, apply an arbitrary voltage to the working electrode while stirring well, oxidize the polymer on the working electrode,
This is a method of forcibly taking in anions.

Examples of dopant anions which can be doped by re-doping include FeCl ₃ and Fe.
OCl, TiCl ₄ , ZrCl ₄ , HfCl ₄ , NbF ₅ ,
NbCl ₅ , TaCl ₅ , MoF ₅ , MoCl ₅ , WF ₆ ,
WCl ₆ , UF ₆ , LnCl ₃ (Ln = La, Ce, P
r, Nd, lanthanoids such as Sm) and other transition metal compounds; HF, HCl, HNO ₃ , H ₂ SO ₄ , HClO ₄ , F
SO ₃ H, ClSO ₃ H, CF ₃ SO ₃ H, various organic acids, protonic acids such as amino acids; Cl ⁻ , Br ⁻ , I ⁻ , Cl
O ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , BF ₄ ⁻ , high molecular weight polysulfonate anion, for example

[Chemical 7] , Other electrolyte anions such as sulfonate anions; Cl
₂ , halogens such as Br ₂ , I ₂ , ICl, ICl ₃ , IBr, and IF; PF ₆ , AsF ₅ , SbP ₅ , BF ₃ , BCl ₃ ,
Lewis acids such as BBr ₃ and SO ₃ ; other O ₂ , XeOF ₄ ,
^{_{(NO 2 +) (SbF 6}} -), (NO 2 +) (SbCl 6 -),
^{_{(NO 2 +) (BF 4}} -), FSO 2 OOSO 2 F, AgCl
_{O 4, H 2 IrCl 6,} La (NO 3) 3 · 6H 2 O , and the like. By once de-doping and re-doping in this way, it is possible to increase the conductivity of the conductive coating and the durability of the conductive coating.

As is clear from the above, according to the method of the present invention, since the oxidative polymerization from the monomer state is carried out through the polymerizable functional group bonded to the surface of the metal particles, a very strong conductive layer can be obtained. It is formed, and peeling or elution from the metal particles does not substantially occur. Furthermore, when the oxidative polymerization is carried out in the presence of the dispersion stabilizer, the aggregation of the metal oxide spherical particles is further prevented before the formation of the conductive polymer layer, during the formation of the conductive polymer layer, and after the formation of the conductive polymer layer. Since the dispersed state of the spherical particles and the monomer is maintained more uniformly, it is possible to obtain the monodispersed spherical particles having the conductive polymer layer with improved conductivity.

The conductive fine particles of the present invention produced by the above-mentioned method of the present invention are excellent in particle size accuracy and conductivity, and are also excellent in strength, hardness and durability. Therefore, it is very suitable for use as an anisotropic conductive film or the like.

[0041]

The present invention will be further described with reference to the following examples.

Example 1 (1) Surface Treatment of Silica Particles with Vinylsilane Coupling Agent 200 g of monodispersed silica fine particles (average particle size 5.19 μm, CV value 0.91%) were placed in a flask having an internal volume of 5 liters, After adding 1260 g of isopropyl alcohol thereto, ultrasonic vibration was applied to obtain a dispersion liquid. 1260 g of methanol and 1000 of 25 wt% ammonia water were added to this dispersion.
g was added and stirred at a liquid temperature of 30 ° C. for 30 minutes to obtain a mixed liquid. 86 g of γ-methacryloxypropyltrimethoxysilane, which is a vinylsilane-based coupling agent, was added to this mixed liquid.
A mixture of (0.35 mol) and 11.2 g (0.054 mol) of tetraethoxysilane, which is one of the alkoxysilanes, was added over 15 minutes. After the addition was completed, the liquid temperature of the obtained mixed liquid was raised to 60 ° C., and then the surface treatment was performed while stirring the mixed liquid for 10 hours. After the completion of the surface treatment, the liquid was allowed to stand and the silica particles were allowed to settle, and the supernatant liquid was removed to obtain precipitated particles (silica particles after the surface treatment). These particles were washed by repeating precipitation and decantation in methanol, and after removing methanol, they were dried in an oven at 150 ° C. for 1 hour. Thus, silica fine particles having a vinyl group introduced on the surface were obtained.

(2) Production of Polyaniline Coated Silica Fine Particles 20 g of polyvinylpyrrolidone K-90 (manufactured by Wako Pure Chemical Industries, Ltd .: molecular weight 400,000) as a dispersion stabilizer was dissolved in 500 ml of 1.2N hydrochloric acid aqueous solution to give a solution ( 10 g of the vinyl group-introduced silica fine particles obtained in 1) was added, and ultrasonic vibration was applied to well disperse the vinyl group-introduced silica fine particles to obtain a dispersion liquid. To this dispersion, 2.5 g (0.011 mol) of ammonium peroxodisulfate was added as an oxidizing agent and stirred well, and then 1 g (0.011 mol) of aniline was added as a monomer capable of forming a polymer having conjugated π electrons. The oxidative polymerization reaction was carried out while stirring at room temperature. After 2 hours, the reaction solution was poured into 500 ml of water to terminate the oxidative polymerization reaction.

The mixed solution was allowed to stand as it was to precipitate fine silica particles having a polyaniline coating layer on the surface. After settling, the supernatant was removed, and a mixed solution of methanol: water = 1: 1 (volume ratio) (500 ml) was added as a washing solution and stirred to disperse the particles in the washing solution. Subsequently, the polyaniline-coated silica fine particles were washed by performing a series of operations of sedimentation and removal of the supernatant liquid five times. After replacing the washing solvent with methanol, it was air-dried.
By heating for an hour, methanol was evaporated and drying was performed. The polyaniline-coated silica fine particles thus obtained have a deep green color, and by observation with a scanning electron microscope, there is no coalescence between the individual particles and the particle size is 5.41 μm (CV value of particle size distribution). : 1.29%), polyaniline was uniformly coated to a thickness of 0.11 μm.

Further, when the electric conductivity was measured by the four-terminal method, it was found to be 3.2 × 10 ⁻³ S / cm, and when an anisotropic conductive film was produced using the conductive fine particles, excellent anisotropic conductivity was obtained. Showed sex.

(3) Coating durability test of polyaniline-coated silica fine particles The polyaniline-coated silica fine particles obtained in (2) were dispersed in methanol and irradiated with ultrasonic waves of 150 W for 30 minutes. After that, the particle size of the particles was determined by scanning electron microscope observation, and it was found that the particle size was 5.40 μm, peeling due to ultrasonic irradiation was not observed, and the polyaniline coating layer had excellent durability. .

Example 2: Preparation of polypyrrole-coated silica fine particles 1 g of polyvinylpyrrolidone K-90 (manufactured by Wako Pure Chemical Industries, Ltd .: molecular weight 400,000) as a dispersion stabilizer was dissolved in 500 ml of water to prepare a solution of Example 1. 10 g of the vinyl group-introduced silica fine particles obtained in (1) were added, and ultrasonic vibration was applied to disperse the fine particles to obtain a dispersion liquid. After adding 5.7 g (0.045 mol) of iron trichloride as an oxidizing agent to this dispersion and stirring well, 0.67 g (0.01 mol) of pyrrole was added as a monomer capable of forming a polymer having conjugated π electrons. Add
The oxidative polymerization reaction was carried out with stirring at room temperature. After 15 hours, the reaction solution was poured into 500 ml of water to terminate the oxidative polymerization reaction.

The mixed liquid was allowed to stand as it was, to precipitate fine silica particles having a polypyrrole coating layer on the surface. After settling, the supernatant was removed, and 500 ml of a mixed solution of methanol: water = 1: 1 (volume ratio) was added as a washing solution and stirred to disperse the polypyrrole-coated silica fine particles in the washing solution.
Then, the polypyrrole-coated silica fine particles were washed by performing a series of operations of sedimentation and removal of the supernatant liquid six times. After replacing the washing solvent with methanol, air-dry,
Further, it was heated at 80 ° C. for 1 hour to evaporate methanol for drying. According to the scanning electron microscope observation, the polypyrrole-coated silica fine particles thus obtained have no coalescence between individual particles and have a particle diameter of 5.49 μm (CV value of particle size distribution: 1.20%). , Polypyrrole is 0.2
It was uniformly coated with a thickness of 0 μm.

Further, the electric conductivity was measured by the four-terminal method and found to be 2.5 × 10 ^-1 S / cm. When an anisotropic conductive film was prepared using the conductive fine particles, excellent anisotropic conductivity was obtained. Showed sex.

Example 3 (1) Surface Treatment of Silica Particles with Allylsilane Coupling Agent In a flask having an inner volume of 1 liter, silica fine particles having a monodispersed particle size distribution (average particle size 6.51 μm, CV value 0.8%, Individual particles are substantially spherical) 50g (total surface area = 30.4)
m ² ), and 315 g of isopropyl alcohol
Then, the silica fine particles were well dispersed by utilizing ultrasonic vibration. After adding 315 g of methanol to this dispersion liquid, stirring was performed for 15 minutes while maintaining the liquid temperature at 40 ° C., subsequently 125 g of 25 wt% ammonia water was added, and further stirred for 15 minutes at the liquid temperature of 40 ° C. to obtain a mixed liquid. . In this mixed solution, 10.22 g (0.050 mol) of allyltrimethoxysilane, which is one of silane coupling agents having an allyl group, and 1.04 g (0.005 mol of tetraethoxysilane, which is one of alkoxysilanes). ) Mixed solution with 10
Added over minutes. After the addition was completed, the liquid temperature of the obtained solution was raised to 60 ° C., and the surface treatment of the silica fine particles was performed while stirring the solution for 10 hours.

After completion of the surface treatment, the solution was allowed to stand to precipitate silica fine particles, and the supernatant was removed to obtain precipitated fine particles. The precipitated fine particles were washed by repeating precipitation and decantation in methanol, and after removing the methanol, the particles were heated and dried in an oven at 150 ° C. for 1 hour.

In the silica fine particles after the surface treatment thus obtained, allyl groups were introduced on the surface of the individual silica fine particles constituting the silica fine particles, and each silica fine particle exhibited water repellency. The introduction of the allyl group on the surface of the silica fine particles was confirmed by the fact that the absorption of vinyl group was observed by the measurement of the infrared absorption spectrum.

(2) Production of Polyaniline-Coated Silica Fine Particles 10 g of polyvinylpyrrolidone K-90 (Wako Pure Chemical Industries, Ltd., molecular weight 400,000), which is a dispersion stabilizer, was dissolved in 500 ml of 1.2N hydrochloric acid aqueous solution to give a solution (1 ) The allyl group-introduced silica fine particles obtained in step 1) were added, and ultrasonic vibration was applied to well disperse the allyl group-introduced silica to obtain a dispersion. To this dispersion solution, 2.5 g (0.011) mol of ammonium peroxodisulfate was added as an oxidizing agent and stirred well, and then 1 g (0.011 mol) of aniline was added as a monomer capable of forming a polymer having conjugated π electrons. Oxidation polymerization was carried out while stirring at room temperature. After 2 hours, the reaction solution was poured into 500 ml of water to complete the oxidative polymerization. The mixed liquid was allowed to stand as it was, and the silica fine particles having the polyaniline coating layer on the surface were allowed to settle. After settling, the supernatant was removed, and a mixed solution of methanol: water = 1: 1 (volume ratio) was added as a washing solution and stirred to disperse the particles in the washing solution. Then, washing was performed by performing a series of operations of sedimentation of the polyaniline-coated silica fine particles and removal of the supernatant liquid 5 times. After replacing the washing liquid with methanol, the washing solvent was evaporated to dry (drying condition: after natural drying,
Heat at 80 ° C for 1 hour). The polyaniline-coated silica thus obtained was observed by a scanning electron microscope,
There was no coalescence between individual particles, the particle size was 6.75 μm (CV value of particle size distribution: 1.32%), and polyaniline was 0.1%.
It was uniformly coated with a thickness of 2 μm.

Further, the electric conductivity was measured by the four-terminal method and found to be 4.8 × 10 ⁻³ S / cm. An anisotropic conductive film was prepared using these conductive fine particles, and it was found that excellent anisotropic conductivity was obtained. Showed sex.

Comparative Example Surface treatment was carried out in the same manner as in (1) of Example 1 except that only methyltriethoxysilane was used as the alkoxysilane without using the silane coupling agent having a polymerizable functional group. Silica fine particles were prepared. Using the obtained surface-treated silica fine particles, aniline was subjected to oxidative polymerization in the same manner as in (2) of Example 1. as a result,
The obtained silica fine particles were observed by a scanning electron microscope to have an average particle diameter of 5.2 μm, and it was revealed that the surface of the silica fine particles was not coated with polyaniline at all.

Further, when the electric conductivity was measured by the four-terminal method, it showed an insulating property of 3.7 × 10 ^-13 S / cm, and it is impossible to produce an anisotropic conductive film using these conductive fine particles. Met.

[0057]

EFFECTS OF THE INVENTION According to the present invention, there are provided a novel conductive fine particle having high strength, high hardness and high durability which is excellent in particle size accuracy and conductivity, and a method for producing the same.

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[Procedure amendment]

[Submission date] October 2, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

The coefficient of variation (CV value) is obtained by the following equation. CV value (%) = (standard deviation of particle size) ÷ (average particle size) × 1
The silane coupling agent having a polymerizable functional group for surface-treating the metal oxide spherical particles (hereinafter, abbreviated as silane coupling agent) is a vinyl group or an allyl group on the surface of the metal oxide. Any one that can introduce a polymerizable functional group such as an acryloyl group, a methacryloyl group, and a glycidoxy group may be used. Specific examples thereof include trimethoxyvinylsilane, triethoxyvinylsilane, allylmethoxysilane, allyltriethoxysilane, vinyltris (β-methoxyethoxy) silane,
Methylvinyldichlorosilane, γ- (meth) acryloxypropyltrimethoxysilane, vinyltrichlorosilane, vinyltris (β-methoxy) silane, γ-methacryloxypropyltrimethoxysilane, N-β (N-vinylbenzylaminoethyl) -γ -Aminopropyltrimethoxysilane, vinyltriacetoxysilane, γ-methacryloxypropylmethyldimethoxysilane, and other vinylsilane coupling agents; β- (3,4-epoxycyclohexyl) ethyltriethoxysilane, γ-glycidoxypropyltri Examples thereof include epoxysilane coupling agents such as methoxysilane, γ-glycidoxypropylmethyldimethoxysilane, and methyltri (glycidyloxy) silane. The silane coupling agent having a polymerizable functional group may be only one kind or plural kinds.

Claims (7)

[Claims] 1. A conductive material characterized in that a layer of a polymer having conjugated π electrons is coated on the surface of a spherical particle made of a metal oxide surface-treated with a silane coupling agent having a polymerizable functional group. Fine particles. 2. The conductive fine particles according to claim 1, wherein the metal oxide is silica. 3. A polymer having conjugated π electrons has the formula R _x —C ₆ H _(5-x) —NH (R ¹ ) (I) (wherein R is at the ortho and / or meta position of the aromatic ring). A substituted C ₁ -C ₁₈ alkyl group or a halogen atom, x represents the number of R, is 0 to 4, and R ¹ is hydrogen or a C ₁ -C ₁₈ alkyl group); A polymer obtained by polymerizing the derivative, or a compound of the formula: (In the formula, R ² and R ³ are each independently hydrogen, a C _{1 to} C ₁₈ alkyl group, a C _{1 to} C ₁₈ alkoxy group or a halogen atom, and X is an NH group, a sulfur or an oxygen atom) The conductive fine particles according to claim 1, which is a polymer obtained by polymerizing pyrrole, thiophene, furan or a derivative thereof. 4. An oxidative polymerization is carried out by adding a monomer capable of forming a polymer having conjugated π electrons to a dispersion liquid containing spherical particles made of a metal oxide surface-treated with a silane coupling agent having a polymerizable functional group. The method for producing conductive fine particles according to claim 1, wherein a polymer layer having conjugated π electrons is formed on the surface of the spherical particles made of metal oxide. 5. The method of claim 4, wherein the metal oxide is silica. 6. The method according to claim 4, wherein the dispersion containing the spherical particles of metal oxide contains a dispersion stabilizer. 7. A monomer capable of forming a polymer having a conjugated π electron has a formula R _x —C ₆ H _(5-x) —NH (R ¹ ) (I) (wherein R is an ortho position of an aromatic ring and And / or a C ₁ -C ₁₈ alkyl group substituted in the meta position or a halogen atom, x represents the number of R, is 0 to 4, and R ¹ is hydrogen or a C _{1 to} C ₁₈ alkyl group) An aniline represented by: or a derivative thereof, or a compound represented by the formula: (In the formula, R ² and R ³ are each independently hydrogen, a C _{1 to} C ₁₈ alkyl group, a C _{1 to} C ₁₈ alkoxy group or a halogen atom, and X is an NH group, a sulfur or an oxygen atom) The method according to claim 4, which is pyrrole, thiophene, furan or a derivative thereof.