JP5466022B2 - Conductive fine particles, anisotropic conductive adhesive composition, and anisotropic conductive molded body - Google Patents

Description

  The present invention relates to conductive fine particles. The present invention also relates to an anisotropic conductive adhesive composition containing such conductive fine particles. Furthermore, this invention relates to the anisotropic conductive molded object obtained from such an anisotropic conductive adhesive composition.

  In an electronic product typified by a liquid crystal display (LCD), a so-called anisotropic conductive material is used to electrically connect various electronic components to the substrates or to electrically connect the substrates to each other. . Among these, anisotropic conductive adhesive compositions (or anisotropic conductive films) in which conductive fine particles are dispersed in a binder resin are widely used. Examples of the conductive fine particles used in the anisotropic conductive adhesive composition (or anisotropic conductive film) include those obtained by subjecting the surface of organic base particles and inorganic base particles to metal plating, metal particles, and the like. (Patent Document 1).

  In recent years, in particular, electronic devices and electronic parts have been downsized, and conductive fine particles with high connection reliability have been demanded. In particular, in the case of connecting between wiring boards patterned with aluminum wiring, since an oxide film exists, conductive fine particles having a function of breaking the oxide film and capable of obtaining good conductivity are formed on the surface. Conductive fine particles having a protruding structure have been proposed. As a method for producing conductive fine particles having a protrusion structure on the surface, for example, when a nickel conductive film is formed on the surface of the base particle by electroless plating, the nickel film and nickel fine particles that become the core of the protrusion A method is disclosed in which conductive protrusions are formed on the surface of the substrate particles by simultaneously depositing and forming a nickel coating while taking in nickel fine particles. However, with this method, it is extremely difficult to control the amount and size of the nickel fine particles to be deposited, so that it is difficult to control the number and size of the obtained protrusions (Patent Document 2). ). In addition, a method for producing protruding particles that polymerizes the polymerizable droplets after attaching the child particles to the surface of the polymerizable droplets, and a metal layer was formed on the surface of the protruding particles obtained by such a manufacturing method. Although the projecting conductive particles are disclosed, there is a problem that the projecting portions are dropped or missing because the adhesion between the projecting particles and the base particles is not sufficient (Patent Document 3).

Japanese Patent Publication No. 6-96771 JP 2000-243132 A JP 2005-171096 A

  The problem of the present invention is that the adhesion between the surface of the substrate particles and the fine particles is sufficiently strong, and the adhesion between the fine particles and the conductive metal layer on the outermost surface is also sufficiently strong. The object is to provide conductive fine particles having a protrusion structure on the surface, which are compatible with each other. Another object of the present invention is to provide an anisotropic conductive adhesive composition containing such conductive fine particles. Furthermore, it is providing the anisotropic conductive molded object obtained from such an anisotropic conductive adhesive composition.

  The conductive fine particles of the present invention are formed by coating fine particle-coated base particles in which amino resin fine particles are present on at least a part of the surface of the base particles with a conductive metal layer.

  The anisotropic conductive adhesive composition of the present invention comprises the conductive fine particles of the present invention dispersed in a binder resin.

  The anisotropic conductive molded body of the present invention is obtained from the anisotropic conductive adhesive composition of the present invention.

  According to the present invention, the adhesion between the surface of the substrate particles and the fine particles is sufficiently strong, and the adhesion between the fine particles and the conductive metal layer on the outermost surface is also sufficiently strong. It is possible to provide conductive fine particles having a protrusion structure on the surface that are compatible with the properties. Moreover, the anisotropic conductive adhesive composition containing such conductive fine particles can be provided. Furthermore, the anisotropic conductive molded object obtained from such an anisotropic conductive adhesive composition can be provided.

≪A. Conductive fine particles >>
The conductive fine particles of the present invention are formed by coating fine particle-coated base particles in which amino resin fine particles are present on at least a part of the surface of the base particles with a conductive metal layer.

<A-1. Fine Particle Coated Base Particle>
The fine particle-coated base particle has amino resin fine particles present on at least a part of the surface of the base particle. “At least part of the surface” means that part or all of the surface may be used. Specifically, any 10 orthographic projections of the fine particle-coated substrate particles may be used. On the surface, the amino resin particles are present at least at one location / one or more particles-coated substrate particles, more preferably at least five sites / one particle-coated substrate particles.

<A-1-1. Base Particle>
Any appropriate base particle may be adopted as the base particle as long as it can be used as the base particle of the conductive fine particles. Examples of the material for the base particles include inorganic materials such as silica; silicone resins (polymethylsilsesquioxane, phenylsilsesquioxane), polyolefin resins (polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride). , Polytetrafluoroethylene, polybutadiene, etc.), vinyl polymer resin ((meth) acrylic resin, styrene resin, (meth) acrylic-styrene resin etc.), polysulfone, polycarbonate, phenolic resin, amino resin (melamine resin, melamine-benzoguanamine) Resin, benzoguanamine resin, etc.), organic materials such as urea resin; organic-inorganic composite materials; and the like. Among these, vinyl polymer resin ((meth) acrylic resin, styrene resin, (meth) acrylic-styrene resin, etc.), amino resin (melamine resin, melamine-benzoguanamine resin) in terms of having an appropriate elastic modulus and recovery characteristics. Benzoguanamine resin, etc.) and organic-inorganic composite materials are preferred. Any appropriate organic-inorganic composite material can be adopted as the organic-inorganic composite material. Preferably, those having the same form as the forms a) to e) of the organic-inorganic composite fine particles in the form 3 of the amino resin fine particles present on the surface of the substrate particles, which will be described later, can be preferably used. As the organic-inorganic composite material, those described in JP-A No. 2003-183337 and JP-A No. 8-81561 can be preferably employed.

  The average particle diameter of the substrate particles is preferably 1 μm or more, more preferably 1 to 100 μm, still more preferably 1 to 50 μm, particularly preferably 1 to 20 μm, and most preferably 1 to 10 μm. When the average particle diameter of the substrate particles is less than 1 μm, when the conductive metal layer is coated by electroless plating or the like, the particles are likely to aggregate and there is a possibility that a uniform conductive metal layer cannot be formed. When the average particle diameter of the substrate particles exceeds 100 μm, the use of conductive fine particles is limited, and there is a risk that the industrial application field may be reduced. The method for evaluating the average particle size will be described later.

<A-1-2. Amino resin fine particles>
The amino resin fine particles in the present invention mean fine particles having an amino resin on the surface. That is, the amino resin fine particles in the present invention may be amino resin fine particles having a uniform composition (amino resin fine particles composed of a uniform amino resin composition) (also referred to as form 1 amino resin fine particles). Alternatively, amino resin fine particles having a non-uniform composition having amino resin components on the surface of the fine particles (for example, including amino resin fine particles of modes 2 and 3 described later) may be used. “Amino resin composition with uniform fine particles” means that the composition of the amino compound used is substantially the same, and the ratio of the amino compound to formaldehyde is slightly different, the core The degree of cross-linking between the surface layer portion and the surface layer portion is included in the form of amino resin fine particles having a uniform composition.

  The average particle diameter of the amino resin fine particles is preferably 1 μm or less, more preferably 0.01 to 1 μm, still more preferably 0.02 to 0.8 μm, and particularly preferably 0.03 to 0.5 μm. When the average particle diameter of the amino resin fine particles falls within the above range, the amino resin fine particles are present on the surface of the base material particles to form the fine particle-coated base material particles so that the insulating fine particles are on the surface of the conductive fine particles. It can be difficult to drop off. The method for evaluating the average particle size will be described later.

  The sharpness of the particle size distribution of the amino resin fine particles can be represented by a variation coefficient (CV value) of the particle diameter. Specifically, the coefficient of variation (CV value) of the amino resin fine particles is preferably 50% or less, more preferably 40% or less, still more preferably 30% or less, and particularly preferably 20% or less. When the variation coefficient (CV value) of the particle diameter of the amino resin fine particles exceeds 50%, the variation in the size of the protrusions in the conductive fine particles of the present invention becomes large, and the conductivity or connection reliability becomes insufficient. There is a fear. A method for evaluating the coefficient of variation (CV value) will be described later.

  Any appropriate amino resin can be adopted as the amino resin as long as it is a polycondensate of an amino compound and formaldehyde. Any appropriate amino compound can be adopted as the amino compound as long as it is a compound having an amino group. The amino compound is preferably a polyfunctional amino compound, and more preferably a polyfunctional amino compound having a triazine ring structure. The amino compound may be used alone or in combination of two or more.

  Examples of the polyfunctional amino compound having a triazine ring structure include melamine; an amino compound represented by general formula (1); a diaminotriazine compound represented by general formula (2) and general formula (3); and benzoguanamine. , Guanamine compounds such as cyclohexanecarboguanamine, cyclohexenecarboguanamine, acetoguanamine, norbornenecarboguanamine, spiroguanamine, and the like. Among these, melamine and benzoguanamine are preferable.

Formula (1), R ^1, identical or different, represent an alkyl group which may if there is a hydrogen atom or a substituent, at least one of R ¹ is an alkyl group which may have a substituent. In general formula (1), R ¹ is preferably a hydrogen atom or a hydroxyalkyl group.

In General Formula (2), R ² is the same or different, and is a hydrocarbon group having 1 to 2 carbon atoms (—CH ₂ —, —CH ₂ CH ₂ —, —, which is a linear structure or a structure having a side chain. CH _(CH 3) -) is.

In general formula (3), R ³ is any one of a linear structure, a structure having a side chain, a structure having an aromatic ring which may have a substituent, and a structure having an alicyclic ring which may have a substituent. It is a C1-C8 hydrocarbon group which is. The structure having an aromatic ring or the structure having an alicyclic ring may be a structure having a side chain.

  As the amino resin fine particles having a uniform composition, which is one of the preferred forms of the amino resin fine particles, conventionally known amino resin fine particles can be adopted as long as the average particle diameter is 1 μm or less. Examples of such amino resin fine particles having a uniform composition and a method for producing the same include, for example, JP 2000-256432 A, JP 2002-293854 A, JP 2002-293855 A, JP 2002-293856 A, JP 2002-293857, JP 2003-55422, JP 2003-82049, JP 2003-138823, JP 2003-147039, JP 2003-171432, JP Examples thereof include amino resin fine particles described in JP-A No. 2003-176330, JP-A No. 2005-97575, JP-A No. 2007-186716, and JP-A No. 2008-101040, and the production method thereof. That is, the amino resin fine particles having a uniform composition are produced by, for example, reacting the polyfunctional amino compound with formaldehyde, preferably in a basic aqueous medium (addition condensation reaction) to form a condensate oligomer. By mixing and curing an acid catalyst such as dodecylbenzenesulfonic acid or sulfuric acid in an aqueous medium in which is dissolved or dispersed, crosslinked amino resin fine particles can be produced. It is preferable that both the step of generating the condensate oligomer and the step of forming the amino resin fine particles having a crosslinked structure are performed in a state of being heated at a temperature of 50 to 100 ° C. In order to control the particle diameter of the crosslinked amino resin fine particles, it is preferable that the step of forming crosslinked amino resin fine particles is performed in the presence of a surfactant. Moreover, as the amino resin fine particles having a uniform composition, commercially available amino resin fine particles (for example, “Eposter” series manufactured by Nippon Shokubai Co., Ltd.) may be employed.

  As amino resin fine particles having a heterogeneous composition having amino resin components on the surface of fine particles, which is another preferred form of the above-mentioned amino resin fine particles, for example, different amino compounds are used for the core portion and the surface layer portion, respectively. And the resulting amino resin fine particles (also referred to as form 2 amino resin fine particles). More preferably, they are two different types selected from polyfunctional amino compounds having a triazine ring structure. Specifically, for example, melamine; an amino compound represented by the above general formula (1); and the above general formula (2) And diaminotriazine compounds represented by the above general formula (3) and the like; guanamine compounds such as benzoguanamine, cyclohexanecarboguanamine, cyclohexenecarboguanamine, acetoguanamine, norbornenecarboguanamine, and spiroguanamine; More preferably, melamine or a combination of the amino compound represented by the above general formula (1) and the above guanamine compound, that is, the melamine or the amino compound represented by the above general formula (1) is used in the core portion to form a surface layer. The case where the guanamine compound is used for the part, or the case where the guanamine compound is used for the core part and the melamine or the amino compound represented by the general formula (1) is used for the surface layer part. Particularly preferred is the case where melamine or the amino compound represented by the above general formula (1) is used for the core part and the guanamine compound is used for the surface part, most preferably melamine is used for the core part. This is a case where benzoguanamine is used for the surface layer. In the case of the above particularly preferred form, the content of the melamine in the amino compound used for the core part or the amino compound represented by the general formula (1) is preferably 1 to 100% by mass, more preferably 80 to 100%. % By mass, more preferably 90-100% by mass, particularly preferably 95-100% by mass, and most preferably 100% by mass. In the case of the above particularly preferred form, the content ratio of the guanamine compound in the amino compound used for the surface layer is preferably 10 to 100% by mass, more preferably 60 to 100% by mass, and still more preferably 80 to 100% by mass. More preferably, it is 85-100 mass%, More preferably, it is 90-100 mass%, Most preferably, it is 95-100 mass%, Most preferably, it is 100 mass%. The amino resin fine particles having a heterogeneous composition having amino resin components on the surface of such fine particles are obtained by the same method as described in the publicly known literature in which the amino resin fine particles having the uniform composition and the production method thereof are described. It is obtained by performing in the presence of fine particles as a core. That is, a surface layer made of an amino resin is formed by reacting an amino compound with formaldehyde (addition condensation reaction) in a state where the core fine particles are dispersed in an aqueous medium. Usually, this reaction is performed under heating (50 to 100 ° C.), and is performed in the presence of an acid catalyst such as dodecylbenzenesulfonic acid or sulfuric acid in order to increase the degree of crosslinking. When the core is amino resin fine particles, the core is produced according to the above-mentioned method for producing amino resin fine particles, and then the reaction for forming the amino resin layer on the surface layer is performed using an aqueous medium in which the obtained amino resin fine particles are dispersed and contained. Should be applied.

  In the fine particles having an amino resin component on the surface, which is another preferred form of the amino resin fine particles, any appropriate particles can be adopted as the particle portion other than the amino resin component. Such fine particles are also referred to as form 3 amino resin fine particles. About the manufacturing method of the said particle | grain, arbitrary appropriate manufacturing methods can be employ | adopted if it is a method of manufacturing particles, such as an inorganic particle, an organic particle, and an organic inorganic composite particle. A similar method can be adopted except that the fine particles serving as the core are replaced with particles other than the amino resin component in the production method of the amino resin fine particles of Form 2. Examples of the material of the particles include vinyl polymer fine particles, silica fine particles, and organic / inorganic composite fine particles. Arbitrary appropriate thickness can be employ | adopted for the thickness of the amino resin layer of the surface layer part in the form 2 and the form 3. The thickness of the amino resin layer of the surface layer part in the form 2 and form 3 is preferably 0.01 μm or more in order to ensure, for example, sufficient adhesion to the metal constituting the conductive layer and adhesion to the base particles. More preferably, it is 0.05 μm or more. The upper limit of the thickness of the amino resin layer of the surface layer part in Form 2 and Form 3 is preferably less than 1 μm, and more preferably 0.5 μm or less. The diameter of the core portion may be controlled in accordance with the thickness of the surface layer portion so as to be within a suitable particle diameter range of the amino resin fine particles described above.

  As said vinyl polymer microparticles | fine-particles, the polymer microparticles | fine-particles obtained using arbitrary appropriate polymerizable monomers and arbitrary appropriate crosslinkable monomers as needed can be employ | adopted.

  The polymerizable monomer may be a compound containing at least one ethylenically unsaturated group in the molecule. Specifically, for example, monomers having a hydroxyl group such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate; methoxypolyethylene glycol (meth) acrylate Monomers having a polyethylene glycol component such as, butyl (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, isoamyl acrylate, lauryl (meth) acrylate, benzyl methacrylate, methacryl Alkyl (meth) acrylates such as tetrahydrofurfuryl acid; trifluoroethyl (meth) acrylate, tetrafluoropropyl (meth) acrylate, pentanefluoropropyl (meth) acrylate, octafluoroamyl (meth) acrylate, etc. Elemental atom-containing (meth) acrylates; aromatic vinyl compounds such as styrene, α-methylstyrene, vinyl tolman, α-chlorostyrene, 0-chlorostyrene, m-chlorostyrene, p-chlorostyrene, p-ethylstyrene; glycidyl (Meth) acrylate; (meth) acrylic acid; (meth) acrylamide; (meth) acrylonitrile; The said polymerizable monomer may be used independently and may use 2 or more types together.

  Examples of the crosslinkable monomer include divinylbenzene, (poly) ethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meta) ) Acrylate, tetramethylol methane tri (meth) acrylate, tetramethylolpropane tetra (meth) acrylate, dipentaerythritol hexaacrylate, diallyl phthalate and isomers thereof, triallyl isocyanurate and derivatives thereof, and the like. The said crosslinkable monomer may be used independently and may use 2 or more types together.

  Arbitrary appropriate silica fine particles can be adopted as the silica fine particles. Specific examples of the silica fine particles include fine particles of hydrolytic condensate of silicon alkoxide, fine particles of hydrolyzed condensate of sodium silicate, and the like.

  The organic-inorganic composite fine particles are composite fine particles which essentially comprise polysiloxane as an inorganic component and a vinyl polymer as an organic component. The polysiloxane as the inorganic component is preferably a polysiloxane skeleton obtained by hydrolysis / condensation of an inorganic compound raw material essentially containing a silicon compound having a (meth) acryloxy group.

As the form of the organic-inorganic composite fine particles, any suitable form can be adopted as long as it contains polysiloxane as an inorganic component and a vinyl polymer as an organic component. Specifically, for example,
a) A form in which polysiloxane, which is an inorganic component, is fine particles and dispersed in a vinyl polymer that is an organic component,
b) Form of core-shell structure in which polysiloxane as an inorganic component is a fine core particle, and a shell made of a vinyl polymer as an organic component is formed on the surface of the core particle;
c) a form of a core-shell structure in which a vinyl polymer as an organic component is a fine core particle, and a shell made of polysiloxane as an inorganic component is formed on the surface of the core particle;
d) A form in which polysiloxane as an inorganic component and vinyl polymer as an organic component are combined or mixed at a molecular level,
e) The form of the core-shell structure in which the fine particles in the state of d) become core particles, and a shell made of polysiloxane as an inorganic component is formed on the surface of the core particles.
Etc.

  As a preferable method for producing the organic-inorganic composite fine particles, for example, JP-A-9-197706, a method for producing organic-inorganic composite particles. Examples thereof include methods described in JP-A-8-81561 and JP-A-2003-183327.

  The shape of the organic-inorganic composite fine particles is not particularly limited, and specifically, for example, spherical, needle-like, plate-like, scale-like, crushed, uneven, eyebrows, candy sugar, etc. The shape can be mentioned.

<A-1-3. Method for producing fine particle-coated substrate particles>
Any appropriate coating method can be adopted as a method of coating the surface of the substrate particles with the amino resin fine particles. For example, a method of performing spray drying after dispersing the base particles and amino resin fine particles in a liquid such as an organic solvent or an aqueous medium, and the amino resin fine particles on the surface of the base particles in a liquid such as an organic solvent or an aqueous medium. A method of chemically bonding base particles and amino resin fine particles after adhering, a method of performing stirring or hybridization treatment with a high-speed stirrer in the coexistence of powder of base particles and amino resin fine particles, amino resin fine particles And a method of removing the dispersion medium with an evaporator and the like after adding the base particles to a dispersion liquid in which the liquid is dispersed in a liquid such as an organic solvent or an aqueous medium.

<A-2. Conductive metal layer>
Arbitrary appropriate metals can be employ | adopted as a metal which comprises an electroconductive metal layer. Examples of such metals include gold, silver, copper, platinum, iron, lead, aluminum, chromium, palladium, nickel, rhodium, ruthenium, antimony, bismuth, germanium, tin, cobalt, indium, nickel-phosphorus, nickel. -Metals and metal compounds such as boron, and alloys thereof. Among these, gold, silver, copper, and nickel are preferable because they are excellent in conductivity and industrially inexpensive.

  The thickness of the conductive metal layer is preferably 10 to 500 nm, more preferably 20 to 400 nm, and still more preferably 50 to 300 nm. When the conductive metal layer has a thickness of less than 10 nm, it may be difficult to maintain a stable electrical connection when used as an anisotropic conductive adhesive composition as conductive fine particles. When the thickness of the conductive metal layer exceeds 500 nm, the surface hardness when the conductive fine particles are formed becomes too high, and there is a possibility that the mechanical properties such as the recovery rate cannot be sufficiently exhibited.

  The conductive metal layer preferably has no substantial cracks or a surface on which no conductive metal layer is formed on the surface. Here, “substantially cracked or a surface on which the conductive metal layer is not formed” means that when the surface of any 10,000 conductive fine particles is observed using an electron microscope (magnification 1000 times), It means that the crack of the conductive metal layer and the exposure of the surface of the base particle and the amino resin fine particles are not substantially visually observed.

  Any appropriate method can be adopted as a method of coating the surface of the fine particle-coated substrate particles with the conductive metal layer. For example, plating method by electroless plating method, displacement plating method, etc .; method of coating fine particle-coated substrate particles with metal fine powder alone or mixed with binder; vacuum deposition, ion plating, ion sputtering, etc. Physical vapor deposition method; and the like. Among these, the electroless plating method is preferable because a conductive metal layer can be easily formed without requiring a large-scale apparatus.

  In general, the electroless plating method includes three steps: (1) a hydrophilization step (etching), (2) a catalyst step, and (3) an electroless plating step. The hydrophilization step (etching) can be omitted depending on the type of the fine particle-coated substrate particles.

  The hydrophilization step (etching) is performed to form minute irregularities on the surface of the fine particle-coated substrate particles and improve the adhesion of the conductive metal layer. The hydrophilization step (etching) includes, for example, an oxidizing agent such as chromic acid, sulfuric acid-chromic acid mixed solution, permanganic acid solution; strong acid such as hydrochloric acid and sulfuric acid; strong alkaline solution such as sodium hydroxide and potassium hydroxide; Is used to form minute irregularities on the surface of the fine particle-coated substrate particles.

  The catalyzing step is performed to form a catalyst layer that can serve as a starting point for the electroless plating step on the surface of the fine particle-coated substrate particles. Any appropriate method can be adopted as a method of forming the catalyst layer. For example, it can be carried out using a catalytic reagent etc. commercially available for electroless plating. Examples of such commercially available catalyzing reagents include pink summers (manufactured by Nippon Kanisen Co., Ltd.) and red summers (manufactured by Nippon Kanisen Co., Ltd.). As a method for forming the catalyst layer, specifically, for example, after immersing the fine particle-coated substrate particles in a solution composed of palladium chloride and tin chloride, a strong acid such as sulfuric acid or hydrochloric acid or a strong alkali such as sodium hydroxide is used. Method of activating with solution to deposit palladium on the surface of fine particle-coated substrate particles; after immersing the substrate particles in a palladium sulfate solution, activation with a solution containing a reducing agent such as dimethylamine borane to activate palladium with a fine particle-coated substrate And a method of precipitating on the particle surface.

  In the electroless plating step, preferably, the fine particle-coated base material particles are sufficiently dispersed in an aqueous medium to prepare an aqueous slurry. Here, it is preferable that the fine particle-coated substrate particles are sufficiently dispersed in an aqueous medium. If the conductive metal layer is formed in a state where the fine particle-coated substrate particles are aggregated, the untreated surface may be exposed. Any appropriate dispersion method can be adopted for the dispersion of the fine particle-coated substrate particles. For example, normal stirring, high speed stirring, dispersion using a shearing dispersion device such as a colloid mill or a homogenizer, and the like can be mentioned. When dispersing, ultrasonic irradiation may be used in combination. Moreover, you may use dispersing agents, such as surfactant, in the case of dispersion | distribution.

  Next, the dispersion-treated fine particle-coated substrate particle slurry is added to an electroless plating bath containing a metal salt, a reducing agent, a complexing agent, etc., and electroless plating is performed.

  As said metal salt, the salt of the metal mentioned above as a metal which comprises a conductive metal layer is mentioned, for example. For example, when nickel salt is used, nickel chloride, nickel sulfate, nickel acetate and the like can be mentioned. What is necessary is just to set the density | concentration of the said metal salt in an electroless-plating bath suitably according to the size (surface area) of microparticles | fine-particles covering base-material particle | grains so that the electroconductive metal layer of desired thickness may be formed.

  Examples of the reducing agent include sodium hypophosphite, dimethylamine borane, sodium borohydride, potassium borohydride, hydrazine and the like.

  Examples of the complexing agent include citric acid, hydroxyacetic acid, tartaric acid, malic acid, lactic acid, gluconic acid, carboxylates such as alkali metal salts and ammonium salts thereof, amino acids such as glycine, ethylenediamine, alkylamine, and the like. Aminic acid, ammonium compound, EDTA, pyrophosphoric acid (salt) and the like. Only 1 type may be used for the said complexing agent and it may use 2 or more types together.

  The pH of the electroless plating bath in the electroless plating method is preferably 4-14.

  In the electroless plating method, when a slurry of fine particle-coated substrate particles is added, the reaction starts quickly and is accompanied by generation of hydrogen gas. The end of the electroless plating process in the electroless plating method ends when the generation of hydrogen gas is no longer recognized. After completion of the reaction, the conductive fine particles are taken out from the reaction system, and washed and dried as necessary.

  The electroless plating process may be repeated a plurality of times. By doing in this way, the multi-layered conductive metal layer can be coated on the fine particle-coated substrate particles. For example, after nickel-coated particles are coated on the fine-particle-coated substrate particles to obtain nickel-coated particles, the nickel-coated particles are placed in an electroless gold plating bath and gold-plated to form a gold coating layer on the outermost layer. Conductive fine particles are obtained.

<A-3. Applications>
The conductive fine particles of the present invention are suitable as a constituent material of an anisotropic conductive material. The anisotropic conductive material is used to electrically connect opposing substrates and electrode terminals in various forms.

  Any appropriate method can be adopted as a method of electrically connecting the electrodes using the anisotropic conductive material. For example, a method for producing an anisotropic conductive adhesive composition by dispersing the conductive fine particles of the present invention in an insulating binder resin and then connecting the anisotropic conductive adhesive composition; And a method of connecting the binder resin and the conductive fine particles of the present invention separately.

≪B. Anisotropic conductive adhesive composition >>
The anisotropic conductive adhesive composition of the present invention comprises the conductive fine particles of the present invention dispersed in a binder resin.

  Any appropriate binder resin can be adopted as the binder resin. For example, thermoplastic resins such as acrylate resins, ethylene-vinyl acetate resins, styrene-butadiene block copolymers; curable resin compositions obtained by reaction with curing agents such as monomers and oligomers having glycidyl groups and isocyanate Examples thereof include curable resin compositions by light and heat.

  As said anisotropic conductive adhesive composition, it can apply to arbitrary appropriate uses. Examples thereof include anisotropic conductive paste, anisotropic conductive ink, anisotropic conductive adhesive, and conductive spacers contained in a liquid crystal display element (LCD) sealant.

  The anisotropic conductive paste is obtained, for example, by making an anisotropic conductive adhesive composition into a paste. The obtained anisotropic conductive paste is put in, for example, a suitable dispenser, applied to a desired thickness on the electrode to be connected, and the counter electrode is superimposed on the coated anisotropic conductive paste. It is used for connection between electrodes by heating and pressurizing to cure the resin.

  The anisotropic conductive ink is obtained, for example, by adding a solvent to the anisotropic conductive adhesive composition to obtain a viscosity suitable for printing. The obtained anisotropic conductive ink is, for example, screen-printed on the electrode to be bonded, the solvent is evaporated, the counter electrode is superimposed on the printed anisotropic conductive ink, and the resultant is heated and compressed. Therefore, it is used for the connection between the electrodes.

≪C. Anisotropic conductive compact >>
The anisotropic conductive molded body of the present invention is obtained from the anisotropic conductive adhesive composition of the present invention. Specific examples of the anisotropic conductive molded body of the present invention include an anisotropic conductive film, an anisotropic conductive film, and an anisotropic conductive sheet.

  The anisotropic conductive molded body of the present invention is prepared by, for example, adding a solvent to the anisotropic conductive adhesive composition of the present invention to form a solution, pouring the solution onto a release film, and then evaporating the solvent. It is obtained by forming an anisotropic conductive adhesive composition into a film.

  The anisotropic conductive molded body of the present invention is disposed, for example, on electrodes to be bonded, and is used for connection between electrodes by superposing a counter electrode on the disposed anisotropic conductive molded body and compressing by heating. Is done.

  The film thickness, coating film thickness and printed film thickness in the anisotropic conductive molded body are calculated from the average particle diameter of the conductive fine particles covered with the insulating fine particles and the specifications of the electrodes to be connected, and the electrodes to be connected It is preferable to set so that the gap between the bonding substrates on which the conductive fine particles are sandwiched and the electrodes to be connected are formed is sufficiently filled with the binder resin layer.

  The anisotropic conductive molded body using the conductive fine particles of the present invention not only shows high conductivity, but also the metal layer is not peeled or broken even when subjected to weight compression, and the electrical conductivity between the opposing electrode substrates is Secure connection. In addition, since it is excellent in stability over time, it is possible to maintain electrical connection between electrode substrates and improve reliability without causing deterioration in conductivity due to plating cracking or the like even during long-term use. .

  Hereinafter, the present invention will be described more specifically by way of examples. However, the present invention is not limited to these examples. Hereinafter, for convenience, “parts by mass” may be simply referred to as “parts”. In addition, “mass%” may be described as “wt%”. In this specification, “mass” may be read as “weight”. The average particle size and coefficient of variation (CV value) were evaluated as follows.

[Measurement of average particle size and coefficient of variation (CV value) by caliper method]
SEM photographs were taken so that the total number of particles was around 200, and the diameter of 100 particles randomly selected from the photograph (maximum length of photographed particles (cross section)) was measured with calipers. The arithmetic average diameter was defined as the average particle diameter D. Further, the coefficient of variation (CV value) of the average particle diameter D was calculated as a percentage (%) of the standard deviation of the particle diameter with respect to the average particle diameter D.

[Example 1]
(Synthesis of substrate particles)
Polyoxyethylene styrenated phenyl ether sulfate ammonium salt (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Hightenol (registered trademark) NF-08) as a surfactant in a four-necked flask equipped with a condenser, thermometer, and dropping port 150 parts of an aqueous solution prepared by dissolving 2 parts with ion-exchanged water was charged. There were prepared 50 parts of styrene, 50 parts of divinylbenzene 960 (manufactured by Nippon Steel Chemical Co., Ltd.), 2,2′-azobis (2,4-dimethylvaleronitrile) (Wako Pure Chemical Industries, Ltd.) as a polymerization initiator. A suspension was prepared by charging 2 parts of V-65 (manufactured by Kogyo Co., Ltd.) and emulsifying and dispersing at 5000 rpm for 5 minutes with a TK homomixer (manufactured by Tokushu Kika Kogyo). To this suspension, 250 parts of ion-exchanged water was added, the temperature was raised to 65 ° C. under a nitrogen atmosphere, and the mixture was held at 65 ° C. for 2 hours to perform radical polymerization. After radical polymerization, the produced emulsion was subjected to solid-liquid separation, and the resulting cake was washed with ion-exchanged water and then with methanol. Thereafter, classification was performed, and vacuum drying was performed at 40 ° C. for 2 hours in a nitrogen atmosphere to obtain base material particles (1). When the particle diameter of the substrate particles (1) was measured by Coulter Multisizer III type (manufactured by Beckman Coulter, Inc.), the average particle diameter was 3.5 μm and the coefficient of variation (CV) was 4.7%.
(Synthesis of fine particle-coated substrate particles)
Amino resin fine particles composed of a condensate of melamine and formaldehyde (Nippon Shokubai Co., Ltd., “Eposter S”, average particle size by caliper method = 0.20 μm, coefficient of variation (CV) = 8.0%) The solution was dispersed in methanol so that the amount was 5.0% by mass. After adding 50 parts of the base particle (1) obtained above to 100 parts of the obtained Eposter S dispersion and dispersing it uniformly, methanol is distilled off by an evaporator, and the surface of the base particle (1) A fine particle-coated substrate particle (1) in which amino resin fine particles were present was obtained. When 10 arbitrary particles of the fine particle-coated substrate particles (1) were observed with an electron microscope (SEM, magnification 10,000 times), the amino resin fine particles were found at 12 locations / fine particles on the orthographic projection surface of the fine particle-coated substrate particles (1). One coated substrate particle was present.
(Synthesis of conductive fine particles)
In a beaker, 10 parts of “Pink Summer” (manufactured by Nippon Kanisen Co., Ltd.) and 70 parts of ion-exchanged water were mixed to obtain a mixed solution. Separately, 10 parts of ion-exchanged water and 2 parts of fine particle-coated substrate particles (1) were added and subjected to ultrasonic dispersion, and the mixture was put into the above mixed solution and stirred for 10 minutes at 30 ° C. The suspension was subjected to solid-liquid separation, and the resulting cake was washed with ion-exchanged water and methanol in this order, and then vacuum-dried at 100 ° C. for 2 hours in a nitrogen atmosphere.
Next, 20 parts of “Red Schumer” (manufactured by Nippon Kanisen Co., Ltd.) and 70 parts of ion-exchanged water were mixed in a beaker to obtain a mixed solution. Separately, 2 parts of the dry particles obtained above were added to 10 parts of ion-exchanged water to prepare an ultrasonic dispersion, and the mixture was put into the above mixed solution and stirred at 30 ° C. for 10 minutes. Then, this suspension was subjected to solid-liquid separation, and the resulting cake was washed with ion-exchanged water and methanol in this order, and then vacuum-dried at 100 ° C. for 2 hours in a nitrogen atmosphere.
By the above operation, palladium activated polymer fine particles (1) having palladium adsorbed on the surface of the fine particle-coated base particles (1) were obtained.
In a beaker, 2 parts of palladium-activated polymer fine particles (1) and 80 parts of ion-exchanged water were suspended, and the temperature was adjusted to 70 ° C. Separately, 60 parts of electroless plating solution “Schuma S680” (manufactured by Nippon Kanisen Co., Ltd.) was placed in another beaker, and the temperature was adjusted to 70 ° C. The electroless plating solution adjusted to 70 ° C. was charged while stirring the suspension of the palladium active polymer fine particles (1) adjusted to 70 ° C. with a stirrer at 300 rpm. Ten seconds after the charging, hydrogen gas bubbling started and the color of the solution changed from green to blackish brown. The time point at which the generation of hydrogen gas was completed was judged as the reaction end point, and stirring was carried out at 70 ° C. for 30 minutes therefrom. After cooling to room temperature, this suspension was subjected to solid-liquid separation, and the resulting cake was washed with ion-exchanged water and methanol in this order, and then dried in a vacuum at 100 ° C. for 2 hours.
Conductive fine particles (1) were obtained by the above operation.
(Synthesis of anisotropic conductive adhesive composition (1))
65 parts of epoxy resin (YL980, manufactured by Japan Epoxy Resin Co., Ltd.), 35 parts of epoxy curing agent (Novacure HX3941HP, manufactured by Asahi Kasei Kogyo Co., Ltd.), 20 parts of conductive fine particles (1), and 200 parts of 1 mmφ zirconia beads are mixed for 30 minutes. Bead mill dispersion was performed to obtain an anisotropic conductive adhesive composition (1).
(Synthesis of anisotropic conductive molded body (1))
An anisotropic conductive molded body that is an anisotropic conductive sheet is formed by applying an anisotropic conductive adhesive composition (1) to a release-treated polyethylene terephthalate film to a dry thickness of 25 μm to form an adhesive layer. (1) was produced.
<Evaluation of conductivity and insulation>
The anisotropic conductive molded body (1) was sandwiched between two glass substrates with ITO having a 150 μm width pattern and heated and pressurized at 200 ° C. for 15 seconds to obtain a conductive connection structure. The obtained conductive connection structure was evaluated for conductivity and insulation according to the following criteria. The results are shown in Table 1.
(Evaluation of conductivity)
The conduction resistance between the electrodes facing each other was measured, and the case where the resistance value was 20Ω or less was evaluated as “◯”, and the case where the resistance value exceeded 20Ω was evaluated as “X”.
(Insulation evaluation)
The insulation resistance between the electrodes facing each other was measured, and the case where the resistance value was 100 MΩ or more was marked as “◯”, and the case where the resistance value was less than 100 MΩ was marked as “X”.
<Evaluation of coating state of conductive fine particles>
The anisotropic conductive adhesive composition was diluted with ethyl acetate and then filtered to take out conductive fine particles, and the coating state of the conductive metal layer was evaluated by SEM according to the following criteria. The results are shown in Table 1.
○: A uniform covering state is maintained.
X: Coating is not uniform.

[Example 2]
<Synthesis of amino resin fine particles (2)>
A four-necked flask equipped with a stirrer, a reflux condenser, and a thermometer was charged with 100 parts of melamine, 193 parts of 37% formalin, and 3.5 parts of 25% aqueous ammonia, and the temperature was raised to 70 ° C. while stirring. Hold for 30 minutes. By this operation, 296.5 parts of amino resin precursor containing liquid (2) was obtained.
Separately, in a flask equipped with a stirrer, a reflux condenser, and a thermometer, a solid content concentration of 65% by mass sodium dodecylbenzenesulfonate (manufactured by Kao Corporation, Neoperex G65) (65% by mass DBSNa) and pure 1400 parts of water was added with stirring and the temperature was raised to 90 ° C. to prepare a uniform aqueous surfactant solution.
296.5 parts of the amino resin precursor-containing liquid (1) is added to the above surfactant aqueous solution under stirring at 90 ° C., and held at 90 ° C. for 5 minutes, and then 10 mass% dodecylbenzenesulfonic acid aqueous solution. 50 parts were added. This state was maintained at 90 ° C. for 5 hours to obtain 1750 parts of liquid containing melamine resin particles (solid content: 10% by mass).
100 parts of benzoguanamine, 130 parts of 37% formalin, 6.2 parts of 65% DBSNa, 5.0 parts of dodecylbenzenesulfonic acid and 350 parts of ion-exchanged water were uniformly dispersed and mixed to obtain a benzoguanamine dispersion. The above benzoguanamine dispersion was dropped into 1752 parts of the melamine resin particle-containing liquid maintained at 90 ° C. over 2 hours. After dropping, the mixture is further maintained at 90 ° C. for 5 hours and then cooled to 30 ° C. to obtain a dispersion containing amino resin fine particles (2) in which the surface of the melamine resin particles is coated with a condensate of benzoguanamine and formaldehyde. It was.
The amino resin fine particle dispersion was subjected to solid-liquid separation using a centrifuge, and the resulting cake was washed with methanol and vacuum dried at 180 ° C. for 2 hours to obtain amino resin fine particle (2) powder.
When the average particle size of the resulting amino resin fine particles (2) was measured by a caliper method, the average particle size was 0.24 μm and the coefficient of variation was 8.2%.
<Synthesis of fine particle-coated substrate particles (2)>
In Example 1, fine particle-coated substrate particles (2) were obtained in the same manner as in Example 1, except that amino resin fine particles (2) were used in place of amino resin fine particles (Eposter S). Arbitrary 10 of the fine particle-coated substrate particles (2) were observed with an electron microscope (SEM, magnification: 10,000 times). One coated substrate particle was present.
<Synthesis of Conductive Fine Particle (2), Anisotropic Conductive Adhesive Composition (2), Anisotropic Conductive Molded Body (2)>
Furthermore, it carried out similarly to Example 1, and obtained the electroconductive fine particles (2), the anisotropic conductive adhesive composition (2), and the anisotropic conductive molded object (2).
The evaluation results are shown in Table 1.

Example 3
175 parts of amorphous silica fine particles (manufactured by Nippon Shokubai Co., Ltd., “Seahoster KE-P30”, average particle diameter 0.28 μm) are placed in a beaker, and 1575 parts of ion-exchanged water are added and ultrasonically dispersed therein. The mixture was transferred to a four-necked flask equipped with a condenser and a thermometer, and the temperature was raised to 90 ° C. Separately, 100 parts of benzoguanamine, 130 parts of 37% formalin, 6.2 parts of 65% DBSNa, 5.0 parts of dodecylbenzenesulfonic acid and 350 parts of ion-exchanged water were uniformly dispersed and mixed to obtain a benzoguanamine dispersion. The above benzoguanamine dispersion was dropped into 1750 parts of the above-mentioned amorphous silica fine particle-containing liquid maintained at 90 ° C. over 2 hours. After the dropping, the mixture was further maintained at 90 ° C. for 5 hours, and then cooled to 30 ° C., and the amino resin fine particles (3) (average particle size 0.36 μm) whose amorphous silica fine particles were coated with the condensation product of benzoguanamine and formaldehyde. ), And then a powder of amino resin fine particles (3) was obtained.
Using the obtained powder of amino resin fine particles (3), after obtaining fine particle-coated substrate particles (3) in the same manner as in Example 2, conductive fine particles (3), anisotropic conductive adhesive A composition (3) and an anisotropic conductive molded body (3) were obtained. When any 10 of the fine particle-coated substrate particles (3) were observed with an electron microscope (SEM, magnification 10,000 times), the amino resin fine particles were found at 10 locations / fine particles on the orthographic projection surface of the fine particle-coated substrate particles (3). One coated substrate particle was present.
The evaluation results are shown in Table 1.

Example 4
The synthesis of the amino resin fine particles (3) in Example 3 was carried out except that polymethyl methacrylate cross-linked product (manufactured by Nippon Shokubai Co., Ltd., “Eposter MX100W”, average particle size 0.20 μm) was used instead of amorphous silica fine particles. In the same manner as in Example 3, after obtaining a dispersion containing amino resin fine particles (4) (average particle size 0.24 μm) whose polymethyl methacrylate cross-linked surface was coated with a condensate of benzoguanamine and formaldehyde, Amino resin fine particle (4) powder was obtained.
After using the obtained amino resin fine particle (4) powder to obtain fine particle-coated substrate particles (4) in the same manner as in Example 2, conductive fine particles (4), anisotropic conductive adhesive A composition (4) and an anisotropic conductive molded body (4) were obtained. When any 10 of the fine particle-coated substrate particles (4) were observed with an electron microscope (SEM, magnification 10,000 times), 15 amino resin particles / fine particles were observed on the orthographic surface of the fine particle-coated substrate particles (4). One coated substrate particle was present.
The evaluation results are shown in Table 1.

Example 5
27 parts of γ-methacryloxypropyltrimethoxysilane was mixed with 54 parts of a 0.15% aqueous dodecylbenzenesulfonic acid solution and heated to 50 ° C. to hydrolyze γ-methacryloxypropyltrimethoxysilane to produce a transparent solution. It was. After cooling, 10 parts of methanol and 0.14 part of azobis (2,4-dimethylvaleronitrile) were mixed with the solution to obtain a liquid B.
On the other hand, 141 parts of water and 9 parts of a 25 mass% ammonia solution were mixed to prepare liquid A separately.
While stirring the liquid A, the liquid B was added dropwise over 10 minutes to carry out a polycondensation reaction. One hour later, while continuing stirring, the temperature was raised to 70 ° C. in a nitrogen atmosphere, and the mixture was heated and held at 70 ° C. for 2 hours to carry out a radical polymerization reaction. Then, it cooled to room temperature and obtained the suspension. The obtained suspension was subjected to solid-liquid separation by filtration, and the obtained cake was repeatedly washed with water and filtered three times, and then vacuum-dried at 150 ° C. for 2 hours to obtain organic-inorganic composite particles ( 5) (average particle diameter 0.80 micrometer) was obtained.
In the synthesis of the amino resin fine particles (3) in Example 3, the surface of the organic / inorganic composite particles (5) is benzoguanamine in the same manner as in Example 2 except that the organic / inorganic composite particles (5) are used instead of the amorphous silica fine particles. After obtaining a dispersion containing amino resin fine particles (5) (average particle size 0.97 μm) coated with a condensate of aldehyde and formaldehyde, amino resin fine particles (5) were obtained.
Using the resulting powder of amino resin fine particles (5), fine particle-coated substrate particles (5) were obtained in the same manner as in Example 2, and then conductive fine particles (5), anisotropic conductive adhesive. A composition (5) and an anisotropic conductive molded body (5) were obtained. When any 10 of the fine particle-coated substrate particles (5) were observed with an electron microscope (SEM, magnification 10,000 times), 9 amino resin particles / fine particles were observed on the orthographic surface of the fine particle-coated substrate particles (5). One coated substrate particle was present.
The evaluation results are shown in Table 1.

[Comparative Example 1]
The same procedure as in Example 1 was carried out except that amorphous silica fine particles (manufactured by Nippon Shokubai Co., Ltd., “Seahoster KE-P30”, average particle size 0.28 μm) were used instead of “Eposter S”. (C1), conductive fine particles (C1), anisotropic conductive adhesive composition (C1), and anisotropic conductive molded body (C1) were obtained.
The evaluation results are shown in Table 1.

[Comparative Example 2]
The same procedure as in Example 1 was repeated except that polymethyl methacrylate cross-linked product (Nippon Shokubai Co., Ltd., “Eposter MX100W”, average particle size 0.20 μm) was used instead of “Eposter S”, and a fine particle-coated substrate Particles (C2), conductive fine particles (C2), anisotropic conductive adhesive composition (C2), and anisotropic conductive molded body (C2) were obtained.
The evaluation results are shown in Table 1.

  As shown in Table 1, in Examples 1 to 5 using the conductive fine particles of the present invention, it can be seen that the conductive connection structure is excellent in conductivity and insulation. Moreover, in Examples 1-5 using the electroconductive fine particles of this invention, it turns out that the coating state of electroconductive fine particles is favorable. On the other hand, in Comparative Example 1 and Comparative Example 2 using amorphous silica fine particles and polymethyl methacrylate cross-linked products instead of amino resin fine particles, the conductivity and insulating properties of the conductive connection structure are inferior. It can be seen that the covering condition is poor.

  The conductive fine particles of the present invention can be suitably used as an anisotropic conductive material for electrical connection.

Claims (3)

At least a portion of the surface of the base particle Ri name particulate coated substrate particles amino resin particles is present is coated with a conductive metal layer, that having a protrusion structure on the surface, the conductive fine particles.   An anisotropic conductive adhesive composition comprising the conductive fine particles according to claim 1 dispersed in a binder resin. An anisotropic conductive molding obtained from the anisotropic conductive adhesive composition according to claim 2.