JP5583613B2 - Conductive fine particles - Google Patents

Description

  The present invention relates to fine conductive fine particles, and particularly relates to conductive fine particles capable of realizing a low resistance value when used for electrical connection.

  In recent years, miniaturization and high functionality of electronic devices have been increasingly progressed. Along with this, electronic components mounted on electric devices are being downsized and mounted with high density, and electrodes and wirings in electronic circuits are becoming finer and narrower. 2. Description of the Related Art Conventionally, in assembling electronic devices, a connection method using an anisotropic conductive material has been adopted to make electrical connection between a large number of opposing electrodes and wirings. An anisotropic conductive material is a material in which conductive fine particles are mixed with a binder resin, for example, anisotropic conductive paste (ACP), anisotropic conductive ink, anisotropic conductive film (ACF), anisotropic conductive. There are sheets. In addition, as the conductive fine particles used for the anisotropic conductive material, those obtained by coating the surfaces of metal particles or resin particles as a substrate with a conductive metal layer are used.

  As described above, with the progress of miniaturization and narrowing of the electrodes and wirings of electronic circuits, conductive fine particles used for anisotropic conductive materials are also required to have a smaller particle diameter. As such conductive particles having a small particle size, for example, a microsphere made of a resin or an inorganic compound and having an average particle size of 0.5 to 2.5 μm and a particle size CV value of 20% or less is used as a base material. The conductive fine particles used are described (see Patent Document 1 (paragraphs 0009 and 0010)).

  Further, the conductive fine particles preferably have a low connection resistance value and a stable connection in making an electrical connection between electrodes and wiring. From such a viewpoint, various studies have been made on conductive metal layers constituting conductive fine particles. For example, Patent Documents 2 to 5 propose forming a silver layer as a conductive metal layer. However, a conductive metal layer specialized for fine conductive fine particles has not been studied.

JP 2000-30526 A International Publication No. 2006/018995 Japanese Patent Laid-Open No. 2-47549 JP 2001-155540 A Japanese Patent No. 4154919

  When the particle diameter of the conductive fine particles is reduced, the connection area obtained by deformation of the conductive fine particles becomes very small at the time of pressure connection, and the connection resistance value in electrical connection tends to increase. Moreover, since the conductive metal layer is hard in the electroconductive fine particles which gave nickel plating as a conductive metal layer like patent document 1, the deformation | transformation of base particle will be inhibited with this electroconductive metal layer. Therefore, there is a problem that the deformation amount of the conductive fine particles is further reduced and the connection resistance value is further increased.

  The present invention has been made in view of the above circumstances, and is a very small conductive fine particle having a number average particle diameter of 1.1 μm to 2.8 μm, and realizes a low resistance value when used for electrical connection. An object is to provide conductive fine particles.

  The conductive fine particles of the present invention that have solved the above problems are conductive fine particles having a base material composed of resin particles and at least one conductive metal layer formed on the surface of the base material. The conductive fine particles themselves have a number average particle diameter of 1.1 μm to 2.8 μm, and at least one layer of the conductive metal layer has a silver-based metal layer formed of silver or a silver alloy. To do. The thickness of the silver metal layer is preferably 0.02 μm to 0.10 μm. The number average particle diameter of the resin particles is preferably 1.0 μm to 2.5 μm.

  According to the present invention, even a very small conductive fine particle having a number average particle diameter of 1.1 μm to 2.8 μm can realize a low resistance value when used for electrical connection.

1. TECHNICAL FIELD The present invention aims to improve fine conductive fine particles. The conductive fine particles to be the subject of the present invention have a number average particle diameter of 1.1 μm or more, preferably 1.2 μm or more, more preferably 1.3 μm or more, and further preferably 1.4 μm or more. It is 8 μm or less, preferably 2.6 μm or less, more preferably 2.4 μm or less, and further preferably 2.2 μm or less. If the number average particle diameter is within this range, it can be suitably used for electrical connection of miniaturized and narrowed electrodes and wirings.

  The fine conductive fine particles of the present invention are composed of a substrate made of resin particles and one or more conductive metal layers formed on the surface of the substrate, and at least one layer of the conductive metal layer is silver or A silver-based metal layer formed from a silver alloy. In the case of conductive fine particles having a very small particle diameter, the connection area obtained by deformation of the conductive fine particles during pressure connection is very small. For this reason, in the case where a hard metal such as nickel plating is used as the conductive metal layer as in the prior art, the connection resistance value tends to be higher as the particle diameter of the conductive fine particles is smaller. However, since the silver-based metal layer is very flexible and does not hinder the deformation of the resin particles during pressure connection, a larger connection area can be secured. Further, the silver-based metal layer has a very high electric conductivity. Therefore, although the conductive fine particles of the present invention have a small diameter, a low resistance value can be realized when used for electrical connection.

  Furthermore, the use of fine conductive particles for high-density wiring with a small distance between wirings increases their usefulness, but in order to ensure connection stability, the volume ratio of resin particles in the conductive particles is higher. Is preferred. In other words, the conductive metal layer is required to have a low connection resistance value even if it is thin. By using a conductive metal layer as a silver-based metal layer, a low connection resistance value and high connection stability can be achieved even for a thin film. Can be secured. This effect is a finding that can be found for the first time after conducting studies using fine conductive particles.

  The metal other than silver contained in the silver alloy may be any metal that can eutect with silver and form an alloy film. Examples of such metals include Fe, Co, Cu, Ni, Zn, Sn, In, Ga, Tl, Zr, W, Mo, Rh, Ru, Ir, Au, Pt, Bi, Al, Mn, Mg etc. are mentioned. These metals may contain 1 type and may contain 2 or more types. Among these, Ni, Sn, Zn, Au, and Cu are preferable. When using a silver alloy, the silver content in the silver alloy is preferably 50% by mass or more, more preferably 70% by mass or more, and further preferably 90% by mass or more. Moreover, phosphorus, boron, etc. which are contained in plating solution may be contained as components other than the said silver.

  Moreover, the silver-type metal layer may contain the phase which consists of other metal components other than silver or a silver alloy in the range which does not impair the effect of this invention. As a phase which consists of another metal component, the form disperse | distributed granularly in a silver-type metal layer is mentioned, for example. As another metal component, the metal which can form the above-mentioned silver alloy is mentioned, for example. The silver or silver alloy content in the silver-based metal layer having a phase composed of such other metal components is preferably 90% by mass or more with respect to 100% by mass of the silver-based metal layer.

  The thickness of the silver-based metal layer is preferably 0.02 μm or more, more preferably 0.03 μm or more, further preferably 0.04 μm or more, preferably 0.10 μm or less, more preferably 0.09 μm or less, Preferably it is 0.08 micrometer or less. If the silver-based metal layer is 0.10 μm or less, the characteristics of the resin particles as the base material are utilized, and the flexibility of the conductive fine particles becomes better. Note that the silver-based metal layer may be provided with a plurality of layers having different compositions. In this case, the total thickness of the plurality of silver-based metal layers may be in the above range.

  The ratio of the number average particle diameter of the resin particles (base material) to the film thickness of the silver-based metal layer (silver-based metal layer / number-average particle diameter of resin particles) is preferably 0.01 or more, more preferably 0.00. 02 or more, more preferably 0.03 or more, preferably 0.10 or less, more preferably 0.08 or less, still more preferably 0.06 or less.

  The conductive metal layer may be a single layer or multiple layers (two or more layers). When the conductive metal layer is a multilayer, it may have a layer made of a metal other than silver or a silver alloy. Examples of other metals include metals such as Ni, Pd, Au, Pt, Fe, Co, Ti, Zn, Al, Sn, Pb, and Bi, and alloys containing two or more metals selected from these metals. Is preferred. In addition, when an electroconductive metal layer is a multilayer, it is also a preferable aspect that an outermost layer is a low melting metal layer.

  In particular, the silver-based metal layer is oxidized when exposed to a high-temperature and high-humidity atmosphere, and the connection resistance value may increase when used for electrical connection. Therefore, in order to prevent oxidation of the silver-based metal layer, it is preferable to form a Pd (palladium) layer or an Au (gold) layer on the surface of the silver-based metal layer. When the Pd layer or Au layer is formed, the thickness is preferably 0.005 μm or more, more preferably 0.010 μm or more, still more preferably 0.015 μm or more, and preferably 0.10 μm or less, more preferably 0. 0.07 μm or less, more preferably 0.05 μm or less.

  In order to improve the adhesion of the silver-based metal layer to the substrate, it is also preferable to form a layer (Ni-based metal layer) made of Ni or Ni alloy as the underlayer before forming the silver-based metal layer. However, since the layer made of Ni or Ni alloy is usually hard, it is preferably a thin film. Specifically, the thickness of the layer made of Ni or Ni alloy is preferably 0.08 μm or less, more preferably 0.07 μm or less, and still more preferably 0.05 μm or less. On the other hand, from the viewpoint of adhesion between the layer made of Ni or Ni alloy and the silver-based metal layer, the thickness of the layer made of Ni or Ni alloy is preferably 0.005 μm or more, more preferably 0.01 μm or more, even more preferably. Is 0.02 μm or more.

  Moreover, it is preferable that the outermost surface of the conductive metal layer is subjected to an antioxidant treatment. Examples of the antioxidant include hydroquinone, catechol, resorcin, pyrgarol, various phenol sulfonic acids and naphthol sulfonic acids. These antioxidants may be used independently and 2 or more types may be used together.

  The method for forming the conductive metal layer is not particularly limited, for example, a method in which the surface of the substrate is plated by an electroless plating method, an electrolytic plating method, or the like; physical properties such as vacuum deposition, ion plating, ion sputtering on the surface of the substrate A method of forming a conductive metal layer by a general vapor deposition method; Among these, the electroless plating method is particularly preferable in that a conductive metal layer can be easily formed without requiring a large-scale apparatus.

  When forming a conductive metal layer by an electroless plating method, it is preferable to perform an electroless plating step after an etching step and a catalytic step.

Etching treatment step In the etching treatment step, the resin particles are oxidized with chromic acid, chromic anhydride-sulfuric acid mixture, permanganic acid, etc .; strong acids such as hydrochloric acid, sulfuric acid, hydrofluoric acid, nitric acid; sodium hydroxide, potassium hydroxide, etc. The surface of the resin particles is formed with fine irregularities using a strong alkaline solution of the above, etc., and the anchor effect of the irregularities is used to improve the adhesion between the resin particles after electroless plating, which will be described later, and the conductive metal layer. .

Catalytic Step In the catalytic step, a palladium catalyst that serves as a base point for plating deposition is adsorbed on the surface of the resin particles. The method for adsorbing the palladium catalyst is not particularly limited, and may be performed using a catalytic reagent commercially available for electroless plating. As a method for catalyzing, for example, a solution containing palladium chloride and stannous chloride is used as a catalyzing reagent, and the resin particles are immersed in the solution to adsorb the catalytic metal on the surface of the resin particles, and then sulfuric acid, hydrochloric acid, etc. A method of depositing palladium on the surface of resin particles by reducing the palladium ions with an alkaline solution such as acid or sodium hydroxide (catalyst-accelerator method) or a solution containing tin ions (Sn ²⁺ ) A method in which tin ions are adsorbed on the surface of resin particles by bringing the particles into contact with each other and then immersed in a solution containing palladium ions (Pd ²⁺ ) to precipitate palladium on the surface of the resin particles (Sensitizing-Activate) Ting method) and the like.

  The liquid temperature and immersion time when the resin particles are immersed in the tin ion-containing solution and the palladium ion-containing solution are not particularly limited as long as each ion can be sufficiently adsorbed to the resin particles, and may be adjusted as appropriate. C. to 60.degree. C. is preferable, and the immersion time is preferably 1 minute to 120 minutes.

Electroless Plating Step In the electroless plating step, a conductive metal layer is formed on the surface of the catalytic resin particles that have adsorbed the palladium catalyst in the catalytic step. The electroless plating process involves immersing catalyzed resin particles in a plating solution in which a reducing agent and a desired metal salt are dissolved to reduce the metal ions in the plating solution with a reducing agent, starting from the palladium catalyst. A desired metal is deposited on the particle surface to form a conductive metal layer.

  In the electroless plating step, first, the catalyzed resin particles are sufficiently dispersed in water to prepare an aqueous slurry of the catalyzed resin particles. Here, in order to develop stable conductive characteristics, it is preferable to sufficiently disperse the catalyzed resin particles in an aqueous medium to be plated. As a means for dispersing the catalyzed resin particles in the aqueous medium, for example, a conventionally known dispersing means such as a normal stirring device, a high-speed stirring device, a shearing dispersion device such as a colloid mill or a homogenizer may be employed, and as necessary. You may use together an ultrasonic wave and a dispersing agent (surfactant etc.).

  Next, an electroless plating solution containing the desired conductive metal salt, reducing agent, complexing agent, various additives, and the like is added to the electroless plating solution prepared above to produce an electroless Causes a plating reaction. The electroless plating reaction starts quickly when an aqueous slurry of catalyzed resin particles is added. Moreover, since this reaction is accompanied by the generation of hydrogen gas, the electroless plating reaction may be terminated when the generation of hydrogen gas is not recognized. After the electroless plating reaction is completed, the resin particles on which the conductive metal layer is formed are taken out from the reaction system, and washed and dried as necessary to obtain conductive fine particles.

  Examples of the conductive metal salt include nitrates, acetates, chlorides, sulfates, and the like of metals exemplified as the metal constituting the conductive metal layer. For example, when forming a silver layer as a conductive metal layer, non-cyanide silver salts such as silver nitrate, silver sulfate, silver perchlorate and silver acetate; cyanogen silver such as potassium cyanide and sodium cyanide A silver salt such as a salt may be contained in the electroless plating solution. In the case of forming a silver alloy layer, in addition to the silver salt, a metal salt (for example, nickel salt such as nickel chloride, nickel sulfate, nickel acetate) included in the silver alloy layer is included in the electroless plating solution. Just do it. The concentration of the conductive metal salt in the electroless plating solution may be appropriately determined in consideration of the size (surface area) of the resin particles so that a conductive metal layer having a desired film thickness is formed.

  Examples of the reducing agent include aldehyde compounds such as formaldehyde, acetaldehyde, and glyoxal; hypophosphorous acid compounds such as sodium hypophosphite and potassium hypophosphite; dimethylamine borane, sodium borohydride, potassium borohydride Boron hydride compounds such as glyoxylic acid, carboxylic acids such as gluconic acid or carboxylic acids (salts) such as alkali metal salts and ammonium salts thereof; ascorbic acids such as ascorbic acid and sodium ascorbate; hydrazine, hydrazine sulfate, etc. Hydrazines; hydroxylamines such as hydroxylamine and hydroxylamine sulfate; saccharides having an aldehyde group (—CHO) such as glucose and invert sugar; and the like. Only one reducing agent may be used, or two or more reducing agents may be used.

  As the complexing agent, a compound having a complexing action on the conductive metal ions can be used. For example, glycerol, tartaric acid, iminodiacetic acid, citric acid, hydroxyacetic acid, tartaric acid, malic acid, lactic acid, succinic acid, malonic acid, pyrophosphoric acid, tripolyphosphoric acid, gluconic acid or carboxylic acids such as alkali metal salts and ammonium salts thereof (Salts); alkali cyanides such as potassium cyanide and sodium cyanide; sugars such as D-sorbitol and dulcitol; amino acids such as glycine; amines such as ethylenediamine, triethanolamine and alkylamine; other ammonium, EDTA (ethylenediamine Acetic acid) or a salt thereof (for example, EDTA4Na (ethylenediaminetetraacetic acid tetrasodium)), 2,2′-bipyridine, pyrophosphoric acid (salt); and the like. Only one type of complexing agent may be used, or two or more types may be used.

  Examples of the various additives include pH adjusters, buffers, accelerators, stabilizers and the like. Examples of the pH adjuster include plating bath sodium hydroxide, sodium hydroxide, ammonium hydroxide, inorganic acid, organic acid and the like. Buffering agents include organic acids, alkali metal salts of inorganic acids, sodium citrate, sodium acetate, oxycarboxylic acid, dihydrogen phosphate, boric acid, and carbonic acid to alleviate sudden changes in pH during plating. . An accelerator is added to suppress the generation of hydrogen, and examples thereof include sulfides and fluorides. Stabilizers include lead chlorides, sulfides, nitrides and the like.

  The pH of the electroless plating solution is not limited, but is preferably 4-14.

  The electroless plating process may be repeated as necessary. For example, by repeating the electroless plating process using electroless plating solutions of different metal types, the surface of the resin particles can be coated with several layers of different metals. Specifically, after silver plating is performed on resin particles to obtain silver-coated particles, the outermost layer is covered with a gold layer by further introducing the silver-coated particles into an electroless gold plating solution and performing gold displacement plating. Thus, conductive fine particles having a silver layer on the inside can be obtained.

  In order to adjust the film thickness of the conductive metal layer, specifically, the resin particle concentration (amount of resin particles per treatment liquid) during electroless plating treatment and the electroless plating used in the electroless plating treatment What is necessary is just to adjust the density | concentration of liquid, pH, or the reaction temperature of electroless-plating process. For example, if the amount of the resin particles with respect to the treatment liquid for the electroless plating treatment is increased or the concentration of the electroless plating liquid used in the electroless plating treatment is reduced, the film thickness of the conductive metal layer is reduced.

Activation Step It is preferable to provide an activation step for activating the palladium catalyst on the surface of the catalyzed resin particles before performing electroless plating. By activating the palladium catalyst, the adhesion between the conductive metal layer and the resin particles can be enhanced, and the deposition of the metal in the electroless plating can be promoted. In the activation step, the catalyzed resin particles are immersed in an activation liquid (accelerator solution) containing an activator. Examples of the activator include sulfuric acid, hydrochloric acid, sodium hydroxide, potassium hydroxide, ammonia solution and the like.

  The conductive fine particles use resin particles as a base material for forming the conductive metal layer. The resin particles only need to contain a resin component, and are not limited to particles composed only of organic materials, but may be particles composed of organic-inorganic composite materials. By using resin particles, conductive fine particles having excellent elastic deformation characteristics can be obtained.

  Examples of the organic material constituting the resin particles include polyolefins such as polyethylene, polypropylene, polyvinyl chloride, polytetrafluoroethylene, polyisobutylene, and polybutadiene; vinyl heavy resins such as styrene resins, acrylic resins, and styrene-acrylic resins. Polyesters such as polyethylene terephthalate and polyethylene naphthalate; polycarbonates; polyamides; polyimides; phenol formaldehyde resins; melamine formaldehyde resins; melamine benzoguanamine formaldehyde resins; urea formaldehyde resins; Examples of the organic-inorganic composite material include a material containing the organic material and a polysiloxane skeleton (for example, a material in which a polysiloxane skeleton and a vinyl polymer are combined). The material which comprises these resin particles may be used independently, and 2 or more types may be used together.

  Among the materials constituting the resin particles, those containing a vinyl polymer and / or a polysiloxane skeleton are preferable. A material containing a vinyl polymer has an organic skeleton formed by polymerizing vinyl groups, and is excellent in elastic deformation during pressure connection. In particular, a vinyl polymer containing divinylbenzene as a polymerization component has little decrease in particle strength after coating with a conductive metal. In addition, the material containing the polysiloxane skeleton has excellent contact pressure with respect to the connected body during pressure connection. In particular, a material in which a polysiloxane skeleton and a vinyl polymer are combined is preferable because it is excellent in elastic deformability and contact pressure, and the connection reliability of the obtained conductive fine particles becomes more excellent.

  The vinyl polymer is obtained by polymerizing a vinyl group-containing monomer (radical polymerization), and the “vinyl group” includes not only a carbon-carbon double bond but also a (meth) acryloxy group, an allyl group, isopropenyl. Substituents having a polymerizable carbon-carbon double bond such as a group, vinylphenyl group and isopropenylphenyl group are also included. In this specification, “(meth) acryloxy group”, “(meth) acrylate” and “(meth) acryl” are “acryloxy group and / or methacryloxy group”, “acrylate and / or methacrylate” and “acryl and / Or methacryl ".

  The vinyl group-containing monomer includes a monomer (1) having one vinyl group in the molecule, one vinyl group in the molecule and a functional group other than the vinyl group (a protic hydrogen such as a carboxyl group or a hydroxyl group). Monomer having a terminal group such as a containing group and an alkoxy group) (2) a crosslinkable vinyl group-containing monomer having three or more vinyl groups in one molecule (hereinafter referred to as “crosslinkable vinyl”). Sometimes referred to as a “group-containing monomer”). These monomers (1) to (3) may be used alone or in combination of two or more. Among these, the crosslinkable vinyl group-containing monomer (3) is preferable.

  Examples of the monomer (1) include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, pentyl (meth) acrylate, Hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, etc. Alkyl (meth) acrylates; cyclopropyl (meth) acrylate, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, cyclooctyl (meth) acrylate, cycloundecyl (meth) a Cycloalkyl (meth) acrylates such as relate, cyclododecyl (meth) acrylate, isobornyl (meth) acrylate, 4-t-butylcyclohexyl (meth) acrylate; phenyl (meth) acrylate, benzyl (meth) acrylate, tolyl (meth) ) Aromatic ring-containing (meth) acrylates such as acrylate and phenethyl (meth) acrylate; alkyl such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, and pt-butylstyrene And styrene monofunctional monomers such as halogen group-containing styrenes such as styrenes, o-chlorostyrene, m-chlorostyrene, and p-chlorostyrene. A monomer (1) may be used independently and may use 2 or more types together. Among these, styrene monofunctional monomers are preferable, and styrene is more preferable.

  Examples of the monomer (2) include monomers having a carboxyl group such as (meth) acrylic acid; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxy Monomers having hydroxy groups such as hydroxy group-containing (meth) acrylates such as butyl (meth) acrylate, hydroxy group-containing styrenes such as p-hydroxystyrene; 2-methoxyethyl (meth) acrylate, 3-methoxybutyl Examples include (meth) acrylates, alkoxy group-containing (meth) acrylates such as 2-butoxyethyl (meth) acrylate, and monomers having an alkoxy group such as alkoxystyrenes such as p-methoxystyrene. A monomer (2) may be used independently and may use 2 or more types together. Here, a carboxyl group, a hydroxy group, an alkoxy group, and the like can form a crosslinked structure when a group serving as a reaction (bonding) partner is present in another monomer.

  Examples of the monomer (3) (crosslinkable vinyl group-containing monomer) include allyl (meth) acrylates such as allyl (meth) acrylate; ethylene glycol di (meth) acrylate and 1,4-butanediol. Di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 1,10-decanediol di (meth) acrylate, 1,3-butylene di (meth) Alkanediol di (meth) acrylate such as acrylate; diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, decaethylene glycol di (meth) acrylate, pentadecaethylene glycol di (meth) acrylate, penta contactor ethylene Glycol di (meta Di (meth) acrylates such as polyalkylene glycol di (meth) acrylate such as acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, polytetramethylene glycol di (meth) acrylate; trimethylolpropane tri Tri (meth) acrylates such as (meth) acrylate; Tetra (meth) acrylates such as pentaerythritol tetra (meth) acrylate; Hexa (meth) acrylates such as dipentaerythritol hexa (meth) acrylate; Divinylbenzene, divinyl Aromatic hydrocarbon crosslinking agents such as naphthalene and derivatives thereof (preferably styrenic polyfunctional monomers such as divinylbenzene); N, N-divinylaniline, divinyl ether, Vinyl sulfide, hetero atom-containing crosslinking agents such as divinyl sulfonic acid; and the like. These crosslinkable vinyl group-containing monomers may be used alone or in combination of two or more. Among these, a monomer having two or more (meth) acryloyl groups in one molecule and a styrene polyfunctional monomer are preferable. Among the monomers having two or more (meth) acryloyl groups in one molecule, a monomer having two or more acryloyl groups in one molecule is preferable, and a monomer having two acryloyl groups in one molecule is preferable. More preferred are dimers (diacrylates), more preferred are alkanediol diacrylates and polyalkylene glycol diacrylates, and particularly preferred are alkanediol diacrylates. Of the styrenic polyfunctional monomers, divinylbenzene is preferred.

  The vinyl polymer includes, as a constituent, the crosslinkable vinyl group-containing monomer (3); the monomer (1) and the crosslinkable vinyl group-containing monomer (3). Is preferred. Specifically, as the former, as a constituent, an embodiment containing a monomer having two or more (meth) acryloyl groups in one molecule; an embodiment containing a styrene polyfunctional monomer; two or more in one molecule An embodiment comprising a monomer having a (meth) acryloyl group and a styrenic polyfunctional monomer is preferred. The latter includes a styrene monofunctional monomer and a monomer having two or more (meth) acryloyl groups in one molecule. And an embodiment containing a styrene monofunctional monomer and a styrene polyfunctional monomer are preferred.

  The polysiloxane skeleton is obtained by hydrolytic condensation of a silane monomer, and examples of the silane monomer include non-crosslinkable silane monomers and crosslinkable silane monomers. Examples of the non-crosslinkable silane monomer include bifunctional silane monomers such as dialkylsilane such as dimethyldimethoxysilane and dimethyldiethoxysilane; and trialkylsilane such as trimethylmethoxysilane and trimethylethoxysilane. And monofunctional silane-based monomers.

  The crosslinkable silane monomer can form a crosslinked structure. The cross-linked structure formed by the cross-linkable silane monomer includes one that cross-links an organic polymer skeleton (for example, a vinyl polymer skeleton) and an organic polymer skeleton (first form); One that crosslinks a polysiloxane skeleton (second form); one that crosslinks an organic polymer skeleton and a polysiloxane skeleton (third form).

  Examples of those that can form the first form include dimethyldivinylsilane, methyltrivinylsilane, and tetravinylsilane. Examples of what can form the second form include tetrafunctional silane monomers such as tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, and tetrabutoxysilane; methyltrimethoxysilane, methyltriethoxysilane And trifunctional silane monomers such as ethyltrimethoxysilane and ethyltriethoxysilane. Examples of those that can form the third form include 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane, And those having a vinyl group such as 3-methacryloxyethoxypropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and p-styryltrimethoxysilane;

  Here, the polysiloxane skeleton preferably has a skeleton derived from a polymerizable polysiloxane having a radical-polymerizable carbon-carbon double bond (for example, a vinyl group or a (meth) acryloyl group). That is, the polysiloxane skeleton is a crosslinkable silane monomer (preferably having a (meth) acryloyl group, more preferably 3-methacryloxy) capable of forming at least the third form of the crosslinked structure as a constituent component. It preferably contains a polysiloxane skeleton formed by hydrolysis and condensation of propyltrimethoxysilane).

  The resin particles have a content of a crosslinkable monomer (crosslinkable vinyl group-containing monomer, crosslinkable silane monomer) of 5% by mass or more in all monomer components constituting the polymer. More preferably, it is 10 mass% or more, More preferably, it is 15 mass% or more, 80 mass% or less is preferable, More preferably, it is 70 mass% or less, More preferably, it is 60 mass% or less.

  The number average particle diameter of the resin particles (base material) is preferably 1.0 μm or more, more preferably 1.1 μm or more, further preferably 1.2 μm or more, particularly preferably 1.3 μm or more, and 2.5 μm. The following is preferable, more preferably 2.3 μm or less, further preferably 2.1 μm or less, and particularly preferably 1.9 μm or less. The number-based variation coefficient (CV value) of the resin particles is preferably 10% or less, more preferably 8% or less, and even more preferably 6% or less.

  As the method for producing the resin particles, emulsion polymerization, suspension polymerization, dispersion polymerization, seed polymerization, sol-gel seed polymerization method and the like can be adopted, but seed polymerization and sol-gel seed polymerization method are preferable because the particle size distribution can be reduced. . The sol-gel seed polymerization method is an embodiment of seed polymerization, and particularly means that seed particles are synthesized by the sol-gel method. For example, the case where polysiloxane obtained by the hydrolysis condensation reaction of alkoxysilane is used as seed particles can be used. Therefore, the seed polymerization includes a case where the seed particles are made of an organic material and a case where the seed particles are made of a material in which an organic material and an inorganic material are combined (in the case of a sol-gel seed polymerization method).

  As described above, the resin particles preferably have a vinyl polymer skeleton and a polysiloxane skeleton. Therefore, as a method for producing resin particles, a crosslinkable silane monomer having a radical polymerizable group is hydrolyzed and subjected to a condensation reaction to prepare polymerizable polysiloxane particles, and then the above-mentioned vinyl is added to the polymerizable polysiloxane particles. The method of absorbing and polymerizing group-containing monomers and the like can be mentioned.

2. Resin-coated conductive fine particles The conductive fine particles of the present invention may further form an insulating resin layer on the surface of the conductive metal layer. The insulating resin layer is not particularly limited as long as the insulating property between the particles of the conductive fine particles can be ensured, and the insulating resin layer can be easily collapsed or peeled off by a constant pressure and / or heating. For example, polyolefins such as polyethylene; (meth) acrylate polymers and copolymers such as polymethyl (meth) acrylate; thermoplastic resins such as polystyrene; and particularly cross-linked products thereof; heat such as epoxy resins, phenol resins, and melamine resins Curable resins; water-soluble resins such as polyvinyl alcohol and mixtures thereof.

  However, when the insulating resin layer is too hard compared to the polymer fine particles serving as the base material, the polymer fine particles themselves may be destroyed before the insulating resin layer is destroyed. Therefore, it is preferable to use uncrosslinked or relatively low degree of crosslinking resin for the insulating resin layer.

  The insulating resin layer may be a single layer or a plurality of layers. For example, single or multiple film-like layers; layers with insulating particles, spheres, lumps, scales and other shapes attached to the surface of the conductive fine particles; and the surface of the conductive fine particles is chemically modified Or a layer formed by doing so. The thickness of the resin insulation layer is preferably 0.01 μm to 1 μm, more preferably 0.02 μm to 0.5 μm, and still more preferably 0.03 μm to 0.4 μm. When the thickness of the resin insulating layer is within the above range, the electrical insulation between the particles is good while maintaining the conduction characteristics by the conductive fine particles.

3. Anisotropic Conductive Material The conductive fine particle of the present invention is also suitable as a constituent material of the anisotropic conductive material, and the anisotropic conductive material using the conductive fine particle of the present invention is also preferable implementation of the present invention. This is one aspect. The form of the anisotropic conductive material is not particularly limited as long as the conductive fine particles of the present invention are used. For example, an anisotropic conductive film, an anisotropic conductive paste, an anisotropic conductive adhesive is used. And various forms such as anisotropic conductive ink. That is, electrical connection can be achieved by providing these anisotropic conductive materials between opposing substrates or between electrode terminals. The anisotropic conductive material using the conductive fine particles of the present invention includes a conductive material for a liquid crystal display element (conductive spacer and composition thereof).

  The anisotropic conductive material is produced by dispersing the conductive fine particles of the present invention in an insulating binder resin to obtain a desired form. Of course, the insulating binder resin and the conductive fine particles May be used separately to connect between substrates or between electrode terminals. The binder resin is not particularly limited, and is, for example, a thermoplastic resin such as an acrylic resin, an ethylene-vinyl acetate resin, a styrene-butadiene block copolymer; a monomer or oligomer having a glycidyl group, and a curing agent such as isocyanate. Examples thereof include a curable resin composition that is cured by reaction and a curable resin composition that is cured by light and heat.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to the following examples, and may be appropriately modified and implemented within a range that can meet the purpose described above and below. All of which are within the scope of the present invention. In the following, “part” means “part by mass” and “%” means “mass%” unless otherwise specified.

1. Evaluation method 1-1. Number average particle size, coefficient of variation (CV value)
<Resin particles>
Measure the particle size of 30000 particles with a particle size distribution analyzer (“Coulter Multisizer III type”, manufactured by Beckman Coulter, Inc.) to obtain the number average particle size and the standard deviation of the particle size. CV value (coefficient of variation) was calculated.
Variation coefficient of particles (%) = 100 × (standard deviation of particle diameter / number average particle diameter)
<Conductive fine particles>
Using a flow type particle image analyzer (manufactured by Sysmex Corporation, “FPIA (registered trademark) -3000”), the particle diameter (μm) of 3000 conductive fine particles was measured, and the number average particle diameter was determined.

1-2. Conductive metal layer thickness Using a flow type particle image analyzer ("FPIA (registered trademark) -3000" manufactured by Sysmex Corporation), particles and conductive metal layer (plating) before forming the conductive metal layer (plating layer) Layer) The number average particle diameter of 3000 particles was measured for each of the formed particles, and the film thickness of the conductive metal layer was calculated from the difference.
Conductive metal layer thickness (μm) = (Da−Db) / 2
Da (μm): Number average particle diameter of 3000 particles after formation of conductive metal layer (plating layer) Db (μm): 3000 particles of particles before formation of conductive metal layer (plating layer) Number average particle diameter

For example, when the conductive metal layer is composed of one silver-based metal layer, the film thickness of the silver-based metal layer was calculated according to the following formula.
Film thickness of silver-based metal layer (μm) = (Y ₁ −X ₁ ) / 2
X ₁ (μm): number average particle diameter of 3000 resin particles Y ₁ (μm): number average particle diameter of 3000 particles after formation of the silver-based metal layer

Further, when two layers of a nickel plating layer and a silver-based metal layer are sequentially formed on the surface of the resin particle as a conductive metal layer, the thickness of the nickel-plated layer and the thickness of the silver-based metal layer are expressed by the following formula: Calculated according to
Nickel plating layer thickness (μm) = (Z ₂ −X ₂ ) / 2
X ₂ (μm): Number average particle diameter of 3000 resin particles Z ₂ (μm): Number average particle diameter of 3000 particles after formation of nickel plating layer Film thickness (μm) of silver-based metal layer = (Y ₂ − Z ₂ ) / 2
Z ₂ (μm): number average particle diameter of 3000 particles after forming the nickel plating layer Y ₂ (μm): number average particle diameter of 3000 particles after forming the silver-based metal layer

1-3. Initial resistance value and occurrence of short circuit 10 parts by mass of conductive fine particles and 100 parts by mass of epoxy resin (manufactured by Mitsubishi Chemical, “JER828”) as a binder resin and a curing agent (manufactured by Sanshin Chemical Co., Ltd., “Sun Aid (registered trademark) SI-” 150 ") 2 parts by mass and 100 parts by mass of toluene, and further 50 parts by mass of 1 mm zirconia beads were added, and dispersion was performed at 300 rpm for 10 minutes using two stainless steel stirring blades. The composition was coated on a release-treated PET film with a bar coater and dried to obtain an anisotropic conductive film.
The obtained anisotropic conductive film was sandwiched between a full-aluminum vapor-deposited glass substrate having resistance measurement lines and a polyimide film substrate having a copper pattern formed at a pitch of 30 μm, and thermocompression bonded under a pressure bonding condition of 5 MPa and 200 ° C. The resistance value between the electrodes was evaluated in three stages of A, B, and C. The case where the initial resistance value was less than 3Ω was “A”, 3Ω or more and less than 5Ω was “B”, and 5Ω or more was “C”. Further, the above resistance value measurement was performed 20 times, and the presence / absence of a short circuit and the number of short circuits were also confirmed.

1-4. Adhesiveness 100 parts of toluene was added to 10 parts of conductive fine particles, 50 parts of 1 mm zirconia beads were further added, and dispersion was performed at 400 rpm for 10 minutes using two stainless steel stirring blades. The particles after the dispersion treatment were taken out and dried, and then the surface of the conductive fine particles was observed with a digital scanning electron microscope (Hitachi Kyowa Engineering, “S-3500N”). 1000 particles are observed, the number of particles from which the conductive metal layer is peeled is counted, and the number of peeled particles is less than 5 “A”, 5 to less than 10 “B”, 10 or more Was “C”.

2. 2. Production of resin particles 2-1. Resin particle No. 1
In a four-necked flask equipped with a condenser, a thermometer, and a dropping port, 1800.0 parts of ion-exchanged water, 24.0 parts of 25% aqueous ammonia, and 555.0 parts of methanol are placed under stirring and 3 from the dropping port. -A polysiloxane particle having a methacryloyl group by adding a mixed liquid of 100.0 parts of methacryloxypropyltrimethoxysilane and 45.0 parts of methanol to hydrolyze and condense 3-methacryloxypropyltrimethoxysilane. An emulsion of (polymerizable polysiloxane particles) was prepared. The number average particle diameter of the polysiloxane particles was 1.28 μm.

  Next, 10.0 parts of 20% aqueous solution of polyoxyethylene styrenated phenyl ether sulfate ammonium salt (Daiichi Kogyo Seiyaku Co., Ltd .: “Hytenol (registered trademark) NF-08”) as an emulsifier was added to ion-exchanged water 400.0. 200.0 parts of styrene and 200.0 parts of divinylbenzene (DVB960 manufactured by Nippon Steel Chemical Co., Ltd.) and 2,2′-azobis (2,4-dimethylvaleronitrile) (Wako Pure Chemical Industries, Ltd.) A solution in which 4.8 parts were dissolved was added and emulsified and dispersed to prepare an emulsion of monomer components.

  Two hours after the start of the reaction, the obtained emulsion was added to an emulsion of polysiloxane particles (seed particles) and further stirred. One hour after the addition of the emulsified liquid, the mixed liquid was sampled and observed with a microscope. As a result, it was confirmed that the polysiloxane particles were enlarged by absorbing the monomer.

  Next, 96.0 parts of a 20% aqueous solution of polyoxyethylene styrenated phenyl ether sulfate ammonium salt and 500.0 parts of ion-exchanged water are added, and the reaction solution is heated to 65 ° C. in a nitrogen atmosphere. Holding for 2 hours, radical polymerization of the monomer component was performed. The emulsion after radical polymerization was subjected to solid-liquid separation, and the obtained cake was washed with ion-exchanged water and methanol, and then baked at 280 ° C. for 1 hour in a nitrogen atmosphere. 1 was obtained. This resin particle No. 1 had a number average particle size of 2.56 μm and a coefficient of variation (CV value) of 5.5%.

2-2. Resin particle No. 2-7
The number average particle size of the seed particles was changed as shown in Table 1 by changing the conditions for producing the polysiloxane particles. Next, in the same manner as in Production Example 1, mixing of the emulsified liquid, absorption of the monomer component with respect to the polysiloxane particles, and radical polymerization were performed to obtain resin particle No. 2-3 and 5-7 were obtained. Further, when the emulsion was prepared, mixing of the emulsion and polysiloxane particles were carried out in the same manner as in Production Example 1 except that 200.0 parts of styrene was changed to 200.0 parts of 1,6-hexanediol diacrylate. The resin component No. was absorbed by absorption of the monomer component and radical polymerization. 4 was obtained.

Production Example 1
Electroless plating process Resin particle no. 1 was etched with an aqueous sodium hydroxide solution, and then sensitized with a tin dichloride solution. Further, activation with a palladium dichloride solution was performed to form palladium nuclei. Next, 1 part of the catalyzed resin particles on which palladium nuclei were formed was put into 100 parts of an electroless silver plating bath, stirred at 50 ° C., and a silver plating layer was formed until the film thickness reached 0.05 μm. Then, after washing with ion exchange water, alcohol substitution was performed and vacuum drying was performed to obtain conductive fine particles.
Electroless silver plating solution composition: silver nitrate 1-30 g / L, ammonia water (concentration 25%) 10 ml / L, Rochelle salt (potassium sodium tartrate) 140 g / L,

Production Examples 2-9, 11, 12
The resin particles used were changed as shown in Table 2, and the silver nitrate concentration in the electroless silver plating solution in the electroless plating process was changed so that the film thickness of the silver-based metal layer was as shown in Table 2. Except for the above, etching treatment and catalytic treatment were performed in the same manner as in Production Example 1 to produce silver-coated particles.

Production Example 10
Resin particle No. 3, palladium nuclei were formed in the same manner as in Production Example 1. Next, the obtained catalyzed resin particles were put into an electroless nickel plating solution, stirred at 70 ° C., and a nickel plating layer was formed until the film thickness became 0.03 μm. Further, the obtained nickel-coated particles were put into the same electroless silver plating solution as in Production Example 1, stirred at 50 ° C., and a silver plating layer was formed until the film thickness became 0.04 μm. Then, after washing with ion exchange water, alcohol substitution was performed and vacuum drying was performed to obtain conductive fine particles.
Nickel plating solution composition: nickel sulfate hexahydrate (30 g / L), sodium hypophosphite (10 g / L), sodium citrate (10 g / L)

Production Example 13
Resin particle No. 3, palladium nuclei were formed in the same manner as in Production Example 1. Next, the obtained catalyzed resin particles were put into the same electroless nickel plating solution as in Production Example 10, stirred at 70 ° C., and a nickel plating layer was formed until the film thickness became 0.10 μm. Then, after washing with ion exchange water, alcohol substitution was performed and vacuum drying was performed to obtain conductive fine particles.

  Table 2 shows the types and evaluation results of the resin particles used for the conductive fine particles obtained in the respective production examples.

The conductive fine particles of Production Examples 1 to 10 have a number average particle diameter of 1.1 μm to 2.8 μm and have a silver-based metal layer as the conductive metal layer, but all have low initial resistance values.
Among these, the manufacture examples 1-8 whose thickness of a silver-type metal layer is 0.02 micrometer or more have a lower initial resistance value, and manufacture whose thickness of a silver-type metal layer is 0.10 micrometer or less In Examples 1 to 10, occurrence of a short circuit was not confirmed, and connection reliability was excellent.
In the conductive fine particles of Production Example 11, the number average particle diameter of the conductive fine particles themselves exceeded 2.8 μm, so the initial resistance value was high, and occurrence of short circuit was confirmed 3 times or more. Since the conductive fine particles of Production Example 12 had a number average particle diameter of less than 1.1 μm, the initial resistance value was high. The conductive fine particles of Production Example 13 had a high initial resistance value because the conductive metal layer was made of Ni.

  The conductive fine particles of the present invention are suitably used for anisotropic conductive materials such as anisotropic conductive films, anisotropic conductive pastes, anisotropic conductive adhesives, anisotropic conductive inks, and the like.

Claims (3)

Conductive fine particles having a base material composed of resin particles and at least one conductive metal layer formed on the surface of the base material,
The number average particle diameter of the conductive fine particles themselves is 1.1 μm to 2.8 μm,
At least one layer of the electrically conductive metal layer, have a silver-based metal layer formed of silver or a silver alloy,
The thickness of the silver-based metal layer is 0.02 μm to 0.10 μm, and the ratio of the number average particle diameter of the resin particles to the film thickness of the silver-based metal layer (film thickness of silver-based metal layer / resin particles conductive fine particles having a number average particle size) of used electrical connection, wherein 0.01 to 0.06 der Rukoto. The conductive fine particles used for electrical connection according to claim 1, wherein the number-based variation coefficient of the particle diameter of the resin particles is 10% or less. The conductive fine particles used for electrical connection according to claim 1 or 2, wherein the resin particles have a number average particle diameter of 1.0 µm to 2.5 µm.