JP5670133B2 - Resin particles, insulated conductive particles and anisotropic conductive materials using the same - Google Patents

Description

  The present invention has good connection reliability (such as suppression of lateral conduction) when used for electrical connection as an anisotropic conductive material such as anisotropic conductive film (ACF) or anisotropic conductive paste (ACP). The present invention relates to insulating resin particles that can provide insulated conductive particles that exhibit the above.

  Conventionally, an anisotropic conductive film (ACF) or anisotropic conductive paste (ACP) or the like is used when a mounting component is electrically connected to a glass substrate or printed wiring board such as a liquid crystal display or a plasma display. Conductive material is used. Such an anisotropic conductive material is generally obtained by dispersing conductive particles in a binder resin to form a film or a paste. Particles coated with a metal layer, metal particles, and the like have been widely used. However, in recent years, with the miniaturization of electronic devices and electronic components, the pattern of connection terminals to be connected has become finer so that adjacent patterns have a narrow pitch, and conduction (so-called lateral) between patterns that should originally be insulated. The problem of continuity) occurs.

  In order to avoid this problem, it has been proposed to provide an insulating layer on the surface of the conductive metal layer of the conductive particles used for the anisotropic conductive material. For example, Patent Document 1 describes insulating coated conductive particles (insulated conductive particles) in which the surface of conductive particles is coated with an insulating resin layer made of an insulating gel-like resin having a specific gel fraction. Has been. Further, Patent Document 2 discloses insulating coated conductive particles (insulated conductive particles) in which particles made of metal are coated with insulating particles, and a functional group having binding properties between the metal and the insulating particles. Particles that are chemically bonded to each other are described. Further, in Patent Document 3, insulating coated conductive particles (insulating) in which a coating layer made of an insulating resin having a specific thickness is formed on the surface of conductive fine particles whose average particle diameter, aspect ratio, and CV value are in a specific range. Electroconductive particles).

Japanese Patent Laid-Open No. 2001-195921 International Publication No. 2003/025955 Japanese Patent Laid-Open No. 2000-100239

  However, in the insulating coated conductive particles disclosed in Patent Documents 1 to 3, when dispersed in a binder resin to produce an anisotropic conductive material, the particles may easily aggregate. Thus, when the dispersibility in a binder resin is bad, when electrical connection was performed using the anisotropic conductive material obtained as a result, a lateral conduction might occur again.

  Therefore, the present invention is sufficient to suppress the aggregation of the insulated conductive particles in the binder resin when electrically connecting with the anisotropic conductive material in which the insulated conductive particles are dispersed in the binder resin. Insulation that can achieve this purpose with the aim of developing the dispersibility and reliably suppressing lateral conduction while maintaining good conduction between opposing electrodes when subjected to electrical connection as an anisotropic conductive material It is an object of the present invention to provide insulating resin particles capable of providing conductive particles. Another object of the present invention is to provide insulated conductive particles and anisotropic conductive material that can achieve the above-described object using such resin particles.

  The present inventors have intensively studied to solve the above problems. As a result, by adopting a combination of methyl (meth) acrylate and divinylbenzene as a monomer composition constituting the resin particles for insulating the conductive particles, the insulated conductive material insulated by the resin particles When the conductive particles are found to exhibit good dispersibility without agglomerating in the binder resin and are electrically connected with an anisotropic conductive material using such insulated conductive particles, they face each other. It was confirmed that lateral conduction could be reliably suppressed while maintaining good conduction between the electrodes, and the present invention was completed.

That is, the resin particles according to the present invention are resin particles that are present on the surfaces of the conductive particles to insulate the conductive particles, and are monomers containing methyl (meth) acrylate and divinylbenzene. It consists of a (meth) acrylic crosslinked particle polymer obtained by polymerizing the composition.
In the resin particles of the present invention, the content ratio of divinylbenzene in the monomer composition is preferably 4% by mass or more, and the average particle diameter is preferably 500 nm or less. Moreover, it is preferable to employ | adopt an emulsion polymerization method for superposition | polymerization at the time of obtaining the (meth) acrylic crosslinked particle polymer which is the resin particle of this invention, and also uses a redox type polymerization initiator for the emulsion polymerization. It is preferable to use an anionic emulsifier.

The insulated conductive particles according to the present invention are characterized in that the resin particles of the present invention are present on at least a part of the surface of the conductive particles.
The anisotropic conductive material according to the present invention is characterized in that the insulated conductive particles according to the present invention are dispersed in a binder resin.

  According to the present invention, since the conductive particles are insulated using resin particles obtained from a predetermined monomer, aggregation of the insulated conductive particles in the binder resin is suppressed and sufficient dispersibility is expressed. In addition, when subjected to electrical connection as an anisotropic conductive material, there is an effect that it is possible to reliably suppress lateral conduction while maintaining good conduction between opposing electrodes.

(Resin particles)
The resin particle of the present invention is used to insulate conductive particles, and is a (meth) acrylic cross-linkage obtained by polymerizing a monomer composition essentially comprising methyl (meth) acrylate and divinylbenzene. It consists of a particle polymer. In the present invention, “methyl (meth) acrylate” means methyl acrylate and / or methyl methacrylate. As methyl (meth) acrylate, methyl methacrylate is preferable.

  In the monomer composition constituting the (meth) acrylic crosslinked polymer, the ratio (mass ratio) of methyl (meth) acrylate to divinylbenzene is (methyl) methacrylate / divinylbenzene of 49 or less. More preferably, it is 12 or less, More preferably, it is 6 or less, It is preferable that it is 1.0 or more, More preferably, it is 1.5 or more, More preferably, it is 2.0 or more. If the value of (meth) methyl acrylate / divinylbenzene is larger than the above range, the effect of suppressing aggregation of the insulated conductive particles tends to be insufficient. If the value of (meth) methyl acrylate / divinylbenzene is smaller than the above range, the adhesion of the resin particles to the conductive particles may be reduced.

  The total amount of methyl (meth) acrylate and divinylbenzene, which are essential monomers in the monomer composition, is 70% by mass or more, preferably 80% by mass or more, more preferably 90%, based on the total monomer composition. % By mass or more, most preferably 100% by mass. When the total amount of methyl (meth) acrylate and divinylbenzene is less than the above range, the effect of suppressing aggregation of the insulated conductive particles tends to be insufficient.

  In addition to methyl (meth) acrylate and divinylbenzene, the monomer composition constituting the (meth) acrylic crosslinked particle polymer is composed of other polymerizable monomers having one or more polymerizable double bonds. It may contain a mer. Examples of other polymerizable monomers include the following.

  That is, as a polymerizable monomer having one polymerizable double bond, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate , Isobutyl (meth) acrylate, t-butyl (meth) acrylate, n-amyl (meth) acrylate, isoamyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, ( Alkyl groups such as decyl (meth) acrylate, lauryl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, 2-phenoxyethyl (meth) acrylate, 3-phenylpropyl (meth) acrylate (Meth) acrylic acid ester having 1 to 18 carbon atoms; hydroxyethyl (meth) acrylate; ) Acrylic acid hydroxypropyl, (meth) acrylic acid, glycidyl (meth) acrylate; (meth) acrylic monomers, and the like. Moreover, as a polymerizable monomer having one polymerizable double bond, styrenes such as styrene, α-methylstyrene, paramethylstyrene, isopropenylstyrene, chlorostyrene; acrylonitrile, methacrylonitrile, ethacrylonitrile, phenyl Examples thereof also include unsaturated nitriles such as acrylonitrile; itaconic acid, maleic acid, fumaric acid or half-ester compounds thereof; vinyl toluene; and epoxy group-containing monomers such as allyl glycidyl ether.

Examples of the polymerizable monomer having two or more polymerizable double bonds include ethylene glycol di (meth) acrylate, hexanediol di (meth) acrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, tetra Examples include tetramethylol acrylate, trimethylol propane trimethacrylate, diallyl phthalate, and triallyl cyanate. The other polymerizable monomer may be only one kind or two or more kinds.
In addition, when the monomer composition which comprises a (meth) acrylic crosslinked particle polymer also contains the other polymerizable monomer mentioned above, those total content is an essential monomer (meta ) The total amount of methyl acrylate and divinylbenzene should be within the above range.

  The content ratio of divinylbenzene in the monomer composition is preferably 4% by mass or more. More preferably, the content ratio of divinylbenzene in the monomer component is 8% by mass or more, and more preferably 14% by mass or more. The greater the proportion of divinylbenzene in the monomer composition, the easier it is to suppress the aggregation of insulated conductive particles. However, if the content ratio of divinylbenzene in the monomer composition is too large, there is a concern that the adhesion of the resin particles to the conductive particles may be reduced, so the content ratio of divinylbenzene is 50% by mass or less. Is preferable, 40 mass% or less is more preferable, and 35 mass% or less is further more preferable.

  The average particle size of the resin particles of the present invention is preferably 500 nm or less. More preferably, it is 350 nm or less, More preferably, it is 250 nm or less, Most preferably, it is 180 nm or less. The smaller the particle diameter of the conductive particles, the easier it is to agglomerate as it is, and therefore the need to suppress aggregation using the resin particles of the present invention increases. In order to make it exist on the surface of the electroconductive particle with a small particle diameter, it is preferable that the particle diameter of the resin particle is also small like the said range. On the other hand, if the average particle size of the resin particles is too small, there is a risk that the suppression of lateral conduction between adjacent electrodes when used as insulated conductive particles may be insufficient. 10 nm or more is preferable, 30 nm or more is more preferable, and 50 nm or more is more preferable.

  In addition, the average particle diameter of the resin particle in this invention means the volume average particle diameter measured by a dynamic light scattering method.

  The volume average particle diameter of the resin particles of the present invention is preferably 0.005 times or more, more preferably 0.01 times or more, and still more preferably 0.005 times or more the number average particle diameter of conductive particles to be insulated. It is preferably not less than 03 times and not more than 0.3 times the number average particle diameter of the conductive particles to be insulated, more preferably not more than 0.1 times, and further preferably not more than 0.08 times. When the size (average particle diameter) of the resin particles with respect to the conductive particles is within the above range, the aggregation suppressing effect can be exhibited efficiently.

The coefficient of variation (CV value) in the particle diameter of the resin particles of the present invention is preferably 50% or less, more preferably 40% or less, still more preferably 30% or less, and most preferably 20% or less. The variation coefficient of the particle diameter is a value obtained by applying the volume average particle diameter measured by the dynamic light scattering method and the standard deviation of the particle diameter to the following formula.
Variation coefficient of particle diameter (%) = 100 × (standard deviation of particle diameter / volume average particle diameter)

  It is preferable to employ an emulsion polymerization method for the polymerization for obtaining the (meth) acrylic crosslinked particle polymer because a particle having a small particle diameter (specifically, 1 μm or less) can be easily obtained. Hereinafter, a particularly preferable embodiment of emulsion polymerization will be described as a polymerization method for obtaining a (meth) acrylic crosslinked particle polymer.

  A preferred embodiment of the emulsion polymerization is a polymerization step in which the monomer composition is emulsion-polymerized in the presence of a polymerization initiator and a surfactant (emulsifier), and after the polymerization step, a surfactant is further added and ripened. Aging process. Emulsion polymerization is usually performed in an aqueous dispersion medium.

  As the polymerization initiator used in the emulsion polymerization, a redox polymerization initiator formed by combining a hydrogen peroxide solution and at least one reducing agent selected from the group consisting of ascorbic acid, tartaric acid and sorbic acid may be used. preferable. Thereby, a particle polymer having a small particle size and a narrow particle size distribution can be obtained. As a method for adding the polymerization initiator, the aqueous hydrogen peroxide solution and the reducing agent may be made into aqueous solutions, respectively, and then the aqueous solution may be continuously or intermittently added to the reaction vessel. The total amount may be added in advance to the reaction vessel and the reducing agent may be added continuously.

  As the surfactant used in the polymerization step, an anionic emulsifier is preferable. Thereby, a particle polymer having a small particle size and a narrow particle size distribution can be obtained. Examples of the anionic emulsifier include sodium lauryl sulfonate and sodium dodecyl benzene sulfonate. Among these, sodium dodecyl benzene sulfonate is particularly preferable. The amount of the surfactant used in the polymerization step is preferably 0.05 to 10 parts by mass and more preferably 0.1 to 7 parts by mass with respect to 100 parts by mass of the monomer composition.

  The emulsion polymerization in the polymerization step may be carried out by a known emulsion polymerization method. For example, a monomer dropping method, a pre-emulsion method, a batch charging polymerization method, etc. can be adopted, and a crosslinked particle polymer having a narrow particle size distribution is obtained. In addition, it is preferable to employ a monomer dropping method. There are no particular restrictions on the monomer composition, the polymerization initiator, the method of charging the surfactant, and the like, which may be set as appropriate. Preferably, the polymerization initiator is preliminarily 5% by mass or more of the total amount of the monomer composition. After the emulsion polymerization is started using a polymerization mixture composed of a part of the surfactant and a surfactant, the remaining monomer composition and the polymerization initiator are preferably added separately or mixed and added dropwise. The polymerization temperature in the polymerization step is preferably 30 to 90 ° C. The polymerization time may be appropriately set according to the reaction rate determined from the charged amount of the monomer composition and the remaining amount in the reaction solution, but is usually about 1 to 12 hours, preferably about 2 to 8 hours. .

  The aging step is performed after the polymerization step for the purpose of reducing the unreacted monomer composition or stabilizing the dispersion containing the particle polymer obtained by emulsion polymerization. At this time, by adding a surfactant, it is possible to prevent aggregation of the crosslinked particle polymer during aging. As the surfactant used in the aging step, the surfactant exemplified in the polymerization step (preferably an anionic emulsifier) can be used, and particularly preferably, the same surfactant as that used in the polymerization step is used. It is preferable to use a nonionic surfactant such as polyoxyethylene alkyl ether, for example. The amount of the surfactant used in the aging step is preferably 0.05 to 10 parts by mass and more preferably 0.1 to 7 parts by mass with respect to 100 parts by mass of the monomer composition used in the emulsion polymerization.

  The aging temperature in the aging step is preferably 50 to 90 ° C, more preferably 70 to 85 ° C. By setting the aging temperature within the above range, the amount of the unreacted monomer composition can be reduced while suppressing the aggregation of particles. The aging time may be appropriately set according to the reaction rate determined from the charged amount of the monomer composition and the remaining amount in the reaction solution, but is usually about 1 to 12 hours, preferably about 2 to 8 hours. .

(Insulated conductive particles)
The insulated conductive particles of the present invention are those in which the resin particles of the present invention are present on at least a part of the surface of the conductive particles. As a result, aggregation in the binder resin can be suppressed and sufficient dispersibility can be exhibited, and as a result, conduction between the opposing electrodes is good when subjected to electrical connection as an anisotropic conductive material. Lateral conduction can be reliably suppressed while maintaining.
First, the conductive particles will be described.
The conductive particles may be metal particles, or composite particles composed of base particles and a conductive metal layer covering at least a part of the surface of the base particles. The latter composite particles are preferred.

Examples of the metal particles include gold, silver, copper, platinum, iron, lead, aluminum, chromium, palladium, nickel, rhodium, ruthenium, antimony, bismuth, germanium, tin, cobalt, indium, nickel-phosphorus, nickel- Examples thereof include particles made of metals such as boron, metal compounds, and alloys thereof. Among these, metal particles selected from gold, silver, copper, and nickel are preferable in that they are excellent in conductivity and industrially inexpensive.
The shape of the metal particles is not particularly limited, and may be any of a spherical shape, a spheroid shape, a confetti shape, a thin plate shape, a needle shape, an eyebrow shape, etc., but a spherical shape is preferable, and a true spherical shape is particularly preferable. .

  There is no restriction | limiting in particular as base particle used for the said composite particle, What is used widely can be used. Examples of the material of the base particle include inorganic materials such as silica; silicone resin (polymethylsilsesquioxane, polyphenylsilsesquioxane), polyolefin resin (polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, poly Tetrafluoroethylene, 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, Organic materials such as benzoguanamine resins) and urea resins; polysiloxanes obtained by hydrolysis / condensation of inorganic compounds such as polysiloxanes (preferably (meth) acryloxy group-containing silicone compounds) ) And an organic component vinyl polymer in any appropriate form (for example, one is dispersed in the other, one is a core particle and the other is a shell layer, the other is a shell / shell form, both at the molecular level) Or a mixed or mixed form of the organic-inorganic composite material. 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. In particular, as the organic-inorganic composite material, those described in JP-A No. 2003-183337 and JP-A No. 8-81561 are preferably used.

The particle diameter of the base particles used for the composite particles is preferably 0.5 μm or more and 10.0 μm or less in number average particle diameter. If the average particle size is too small, the particles tend to aggregate when the conductive metal layer is coated by electroless plating or the like, and there is a possibility that a uniform conductive metal layer cannot be formed. On the other hand, if the average particle size is too large, the application uses are limited, such as difficulty in application when the interval between adjacent electrodes is narrow, and there is a tendency that the industrial application fields are reduced. The average particle diameter of the substrate particles is more preferably 1.0 μm or more and 5.0 μm or less, further preferably 1.2 μm or more and 3.0 μm or less, and most preferably 1.5 μm or more and 2.7 μm. It is as follows.
The number average particle diameter is specifically a number-based value measured by a precision particle size distribution measuring apparatus using the Coulter principle (for example, “Coulter Multisizer III type” manufactured by Beckman Coulter, Inc.). .

The coefficient of variation (CV value) in the particle diameter of the base particles used for the composite particles is preferably 10% or less, more preferably 7% or less, still more preferably 5% or less, and most preferably 4% or less. The coefficient of variation of the particle diameter is a value obtained by applying the following equation to the average particle diameter of the particles measured by a precision particle size distribution measuring apparatus using the Coulter principle and the standard deviation of the particle diameter of the particles. .
Coefficient of variation of particle diameter (%) = 100 × (standard deviation of particle diameter / number average particle diameter)

  The shape of the base particles used for the composite particles is not particularly limited, and may be any of, for example, a spherical shape, a spheroid shape, a confetti shape, a thin plate shape, a needle shape, an eyebrows shape, and a spherical shape is preferable. A true spherical shape is particularly preferable.

  The metal constituting the conductive metal layer is not particularly limited as long as it is a conductive compound. For example, metals and metals such as gold, silver, copper, platinum, iron, lead, aluminum, chromium, palladium, nickel, rhodium, ruthenium, antimony, bismuth, germanium, tin, cobalt, indium, nickel-phosphorus, nickel-boron Examples thereof include compounds and alloys thereof. Among these, gold, silver, copper, and nickel are preferable because they are excellent in conductivity and industrially inexpensive. Further, the conductive metal layer may be a single layer or multiple layers. In the case of multiple layers, for example, nickel-gold, nickel-palladium, nickel-palladium-gold, nickel-silver and the like are preferable. Can be mentioned.

  The thickness of the conductive metal layer is not particularly limited, but is preferably 10 to 500 nm, more preferably 20 to 400 nm, and still more preferably 50 to 300 nm. When the thickness of the conductive metal layer is less than 10 nm, there is a possibility that stable electrical connection is difficult to be obtained when insulating conductive particles are used. When the thickness of the conductive metal layer exceeds 500 nm, the surface hardness of the conductive particles becomes too high, and the mechanical properties such as the recovery rate may decrease.

  The conductive metal layer in the composite particles only needs to cover at least a part of the surface of the base particle, but the surface of the conductive metal layer has substantial cracks or a conductive metal layer formed. It is preferred that no surface is present. Here, “substantially cracked or a surface on which no conductive metal layer is formed” means that when the surface of any 10,000 conductive particles is observed using an electron microscope (magnification 2000 times), It means that the ratio at which cracking of the conductive metal layer or exposure of the surface of the base material particles is observed is 5% or less.

  The method of coating the surface of the substrate particles with the conductive metal layer is not particularly limited, and a conventionally known method, for example, a method of performing plating such as an electroless plating method or an electrolytic plating method; A method of coating the base particles with a paste mixed with a binder; a physical vapor deposition method such as vacuum deposition, ion plating, ion sputtering, etc. may be employed. 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.

  In the electroless plating method, first, a catalyst layer is formed on the surface of the base particle as a base point for the next electroless plating treatment. As a method for forming the catalyst layer, for example, a solution containing palladium dichloride and tin dichloride is used as a catalyst reagent, and the catalyst particles are adsorbed on the surface of the substrate particles by immersing the substrate particles in the solution. In addition, by reducing the palladium ions with an alkali solution such as sulfuric acid or hydrochloric acid or an alkali solution such as sodium hydroxide, a method of depositing palladium on the surface of the substrate particles (catalyst-acceleration method), A method (sensitizing-activation method) in which palladium is deposited on the surface of the substrate particles by adsorbing tin ions on the surface of the substrate particles by contacting with tin dichloride and then dipping in a palladium dichloride solution. Can be mentioned.

In the electroless plating method, subsequently, the surface of the substrate particles on which the catalyst layer is formed is subjected to an electroless plating treatment to form a conductive metal layer. The electroless plating treatment involves immersing the base material particles on which the catalyst layer is formed in a plating solution in which a reducing agent and a desired conductive metal salt are dissolved, thereby starting metal ions in the plating solution from the catalyst. And a desired metal is deposited on the surface of the substrate particles to form a conductive metal layer. Examples of the conductive metal salt contained in the electroless plating solution include chlorides, sulfates, acetates, and the like of the metals exemplified above as the metal constituting the conductive metal layer.
The electroless plating treatment may be repeated as necessary. For example, by repeating the electroless plating process using electroless plating solutions having different metal types, the surface of the substrate particles can be coated with several layers of different metals. Specifically, after nickel plating is performed on the substrate particles to obtain nickel-coated particles, the outermost layer is a gold layer by adding the nickel-coated particles to an electroless gold plating solution and performing gold displacement plating. The electroconductive particle which is covered with and has a nickel layer inside is obtained.

The average particle size of the conductive particles obtained as described above is preferably 11 μm or less, more preferably 6.0 μm or less, still more preferably 4.0 μm or less, and particularly preferably 2. 8 μm or less. As described above, the smaller the particle diameter of the conductive particles is in the above range, the easier it is to agglomerate as it is. Therefore, the necessity to suppress aggregation using the resin particles of the present invention increases. The average particle diameter of the conductive particles is preferably 1.1 μm or more, more preferably 1.3 μm or more, and further preferably 1.6 μm or more.
In addition, the average particle diameter of the electroconductive particle in this invention means the number average particle diameter measured by a flow type particle image analyzer (for example, "FPIA-3000" by Sysmex Corporation).

  As a method for fixing the above-described resin particles of the present invention on the surface of the conductive particles, a conventionally known coating method can be employed. For example, a method in which conductive particles after electroless plating treatment and the resin particles of the present invention are dispersed in a liquid such as an organic solvent or an aqueous medium and then spray-dried; in a liquid such as an organic solvent or an aqueous medium Method of attaching resin particles to the surface of conductive particles and then chemically bonding the conductive particles and resin particles; stirring and hybridization using a high-speed stirrer in the presence of conductive powder and resin particle powder And the like.

  The resin particles only need to be present on at least part of the surface of the conductive particles, and the abundance ratio of the resin particles in the entire surface of the conductive particles (in other words, the coverage of the conductive particles by the resin particles) is: Preferably they are 1% or more and 70% or less, More preferably, they are 5% or more and 60% or less, More preferably, they are 10% or more and 50% or less. When the coverage of the conductive particles by the resin particles is within the above range, it is possible to reliably insulate adjacent insulated conductive particles while ensuring sufficient electrical conductivity. In addition, the said coverage is the coating | cover of the resin particle in the orthographic projection surface of insulated conductive particles, when the surface of arbitrary 100 insulated conductive particles is observed using an electron microscope (5000 times magnification), for example It can be evaluated by measuring the area ratio of the portion that is not covered with the resin particles.

(Anisotropic conductive material)
The anisotropic conductive material of the present invention is obtained by dispersing the insulated conductive particles of the present invention in a binder resin. The form of the anisotropic conductive material is not particularly limited. For example, the anisotropic conductive film, the anisotropic conductive paste, the anisotropic conductive adhesive, the anisotropic conductive ink, or the like between the opposing substrates or The thing which enables an electrical connection by providing between electrode terminals is mentioned. The anisotropic conductive material of the present invention also includes a conductive material for liquid crystal display elements such as a conductive spacer and its composition.

  There is no restriction | limiting in particular as said binder resin, A conventionally well-known binder resin can be used. For example, thermoplastic resins such as (meth) 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 isocyanates Examples thereof include curable resin compositions by light and heat.

  For example, the anisotropic conductive film is made into a liquid by adding a solvent to the film-forming composition containing the insulated conductive particles of the present invention and a binder resin, and this liquid is applied on a film made of polyethylene terephthalate or the like. It can be obtained by evaporating the solvent. The obtained anisotropic conductive film is disposed on electrodes, for example, and is used for connection between the electrodes by superposing a counter electrode on the anisotropic conductive film and heating and compressing it.

  An anisotropic conductive paste is obtained by making the resin composition containing the insulated conductive particle of this invention, binder resin, etc. into paste form, for example. The obtained anisotropic conductive paste is placed in, for example, a suitable dispenser, applied on the electrode to be connected with a desired thickness, and the counter electrode is superimposed on the coated anisotropic conductive paste. It is used for connection between electrodes by curing the resin by applying pressure while heating.

  The anisotropic conductive adhesive is obtained, for example, by adjusting a resin composition containing the insulated conductive particles of the present invention and a binder resin to a desired viscosity. The obtained anisotropic conductive adhesive is used to connect between electrodes by coating the electrodes with a desired thickness, then overlaying the counter electrodes and bonding them together, as with the anisotropic conductive paste. Is done.

  The anisotropic conductive ink can be obtained, for example, by adding a solvent to the resin composition containing the insulated conductive particles of the present invention and a binder resin to adjust the viscosity to be suitable for printing. The obtained anisotropic conductive ink is obtained by, for example, screen-printing on the electrode to be bonded, evaporating the solvent, superimposing the counter electrode on the printing surface with the anisotropic conductive ink, and heating and compressing the electrode. Used for connection between.

  In the anisotropic conductive material of the present invention, the content of the insulated conductive particles of the present invention may be appropriately determined according to the application, for example, 2 to 70 volumes with respect to the total amount of the anisotropic conductive material. % Is preferred. More preferably, it is 5 volume% or more, More preferably, it is 10 volume% or more, More preferably, it is 50 volume% or less, More preferably, it is 40 volume% or less. If the content of insulated conductive particles is too small, it may be difficult to obtain sufficient electrical continuity. On the other hand, if the content of insulated conductive particles is too large, the particles may come into contact with each other, resulting in a difference. In some cases, the function as an anisotropic conductive material is difficult to be exhibited.

  About the film thickness in the anisotropic conductive material of the present invention, the coating thickness of the paste or adhesive, the printed film thickness, etc., the particle diameter of the insulated conductive particles of the present invention to be used and the electrode to be connected Considering the specifications, the insulating conductive particles are sandwiched between the electrodes to be connected, and appropriately set so that the gap between the bonding substrates on which the electrodes to be connected are formed is sufficiently filled with the binder resin layer It is preferable to do.

  There is no particular limitation on the connection method when the connection parts are electrically connected using the anisotropic conductive material of the present invention. For example, the temperature at the time of connection is preferably 190 ° C. or lower, more preferably 170 ° C. or lower, further preferably 150 ° C. or lower, preferably 80 ° C. or higher, more preferably 100 ° C. or higher, and further preferably 120 ° C. or higher. is there. The pressure at the time of connection is usually 1 to 100 MPa. The connection time (time for applying heat and pressure) may be appropriately set according to temperature and pressure, but is usually 10 seconds to 3600 seconds.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.
In the following description, “part” means “part by mass” unless otherwise specified.

Example 1
[Production of resin particles]
To a stainless steel reaction kettle equipped with a stirrer, a thermometer and a cooler, 820 parts of deionized water and 0.8 part of sodium dodecylbenzenesulfonate (active ingredient 60% by mass; hereinafter referred to as “DBSNa”) were added. The temperature was raised to 75 ° C. and kept at the same temperature.
On the other hand, in a container different from the reaction kettle, 140 parts of methyl methacrylate (hereinafter referred to as “MMA”) and 60 parts of divinylbenzene (81% by mass of active ingredient; hereinafter referred to as “DVB”) are mixed. 200 parts of the monomer composition was prepared.

After replacing the inside of the reaction kettle with nitrogen gas, 20 parts of the monomer composition (10% by mass of the total amount of the monomer composition), 50 parts of 0.4% by mass hydrogen peroxide, and 0.4% by mass An initial polymerization reaction was carried out by adding 50 parts of a% L-ascorbic acid aqueous solution to the reaction kettle.
Next, 180 parts of the remaining monomer composition (90% by mass of the total amount of the monomer composition), 450 parts by mass of 0.4% by mass hydrogen peroxide, and 450 parts by mass of 0.4% by mass L-ascorbic acid aqueous solution Were dripped uniformly into the reaction kettle over 6 hours from different inlets. Thereafter, the internal temperature was raised to 90 ° C. and held at the same temperature for 6 hours for aging, and then the reaction solution was cooled to obtain a resin particle dispersion (1) in which the resin particles (1) were dispersed. The particle size of the resin particles (1) in this dispersion was measured with a dynamic light scattering particle size distribution measuring device (“NICOMP380” manufactured by PS Japan). The volume average particle size was 158 nm, and the variation coefficient was 11%. Met.

[Preparation of conductive particles]
Polyoxyethylene styrenated phenyl ether sulfate ammonium salt (Daiichi Kogyo Seiyaku "Hitenol (registered trademark) NF-08") as a surfactant in a four-necked flask equipped with a condenser, thermometer, and dripping port ) 150 parts of an aqueous solution prepared by dissolving 2 parts in deionized water. Subsequently, a mixture of 45 parts of DVB prepared in advance, 50 parts of 1,6-hexanediol diacrylate and 5 parts of methacrylic acid, and 2,2′-azobis (2,4-dimethylvaleronitrile) as a polymerization initiator 2 parts (“V-65” manufactured by Wako Pure Chemical Industries, Ltd.) were added and emulsified and dispersed to prepare a suspension. To the obtained suspension, 250 parts of deionized water was further added, the temperature was raised to 65 ° C. under a nitrogen atmosphere, and the mixture was held at the same temperature for 2 hours to perform radical polymerization.

  Next, the emulsion obtained by radical polymerization is subjected to solid-liquid separation, and the obtained cake is washed with deionized water, subsequently washed with methanol, and further subjected to a classification operation, followed by 120 ° C. in a nitrogen atmosphere. And vacuum drying for 2 hours to obtain vinyl polymer particles. When the particle size of the polymer particles was measured with a particle size distribution analyzer (“Coulter Multisizer III type” manufactured by Beckman Coulter, Inc.), the number average particle size was 2.5 μm and the variation coefficient was 3.9%.

Using the polymer particles as base particles, the base particles are sensitized with a tin dichloride (SnCl ₂ ) solution and subsequently activated with a palladium dichloride (PdCl ₂ ) solution. Pd nuclei were formed. By soaking the particles in which the Pd nuclei are formed in an electroless nickel plating bath, Ni particles are applied to the surface of the particles, and then the nickel layer surface of the obtained particles is further subjected to gold plating by displacement plating, Conductive particles (1) having a metal layer thickness of 0.1 μm and a number average particle diameter of 2.7 μm were obtained.

In the examples of the present specification, the number average particle diameter of the conductive particles and the film thickness of the metal layer were measured and calculated as follows.
Number average particle diameter of conductive particles: measured by a flow type particle image analyzer (“FPIA-3000” manufactured by Sysmex Corporation), and the average particle diameter based on the number was defined as the number average particle diameter of the conductive particles.
Film thickness of the metal layer: The number average particle diameter of the polymer particles used for the base particles is measured by the above flow type particle image analyzer, and the obtained number average particle diameter and the conductive particles obtained by the above measurement 1/2 of the difference from the number average particle diameter was taken as the film thickness of the metal layer.

[Preparation of insulated conductive particles]
The resin particle dispersion (1) was diluted with deionized water so that the particle concentration was 5.0% by mass. After adding 50 parts of conductive particles (1) to 100 parts of the obtained resin particle dispersion and dispersing uniformly, water is distilled off with an evaporator, and the surface of the conductive particles is covered with resin particles. Conductive particles (1) were obtained.

[Production of anisotropic conductive material]
Insulating coating conductive fine particles (1) 20 parts, epoxy resin (“YL980” manufactured by Japan Epoxy Resin Co., Ltd.) 65 parts, epoxy curing agent (“NovaCure (registered trademark) HX3941HP” manufactured by Asahi Kasei Co., Ltd.) 35 parts, and 1 mmφ 200 parts of zirconia beads were mixed and subjected to bead mill dispersion for 30 minutes to obtain an anisotropic conductive adhesive (1) as an anisotropic conductive material.

A conductive connection structure was prepared using the obtained anisotropic conductive adhesive, and the following evaluation was performed. The results are shown in Table 1.
The production of the conductive connection structure is first anisotropic so that the release thickness of the release film (polyethylene terephthalate film that has been subjected to release treatment on one side with silicone resin or fluororesin) is 25 μm. The anisotropic conductive sheet which formed the contact bonding layer by apply | coating a conductive conductive adhesive, and was equipped with the adhesive bond layer on the single side | surface of the release film was produced.
Next, the release film is peeled from the obtained anisotropic conductive sheet, and only the adhesive layer is placed between two ITO-attached glass substrates on which an ITO transparent electrode film having a 150 μm wide pattern is formed on the inner surface. The conductive connection structure was obtained by heating and pressing at 1 MPa and 185 ° C. for 15 seconds.

<Dispersed state of insulated conductive particles>
The conductive connection structure was observed with a microscope from one side, and the dispersed state of the insulated conductive particles sandwiched between adjacent electrodes was observed with a microscope, and judged according to the following criteria.
A: Individual insulated conductive particles are uniformly dispersed, and an aggregate in which two or more insulated conductive particles are connected is not observed.
A: Aggregates in which 2 to 3 insulated conductive particles are connected are observed.
(Triangle | delta): The aggregate which the 4-9 insulated conductive particle connected was recognized.
X: Aggregates in which 10 or more insulated conductive particles are connected are observed.

<Conductivity>
Using the conductive connection structure as a measurement sample, the conduction resistance between the opposing electrodes was measured by the four-terminal method. Measurement was performed at n = 50, and the ratio (%) at which the resistance value was 20Ω or less was determined.

<Insulation>
Using the conductive connection structure as a measurement sample, the insulation resistance between adjacent electrodes was measured by the four-terminal method. Measurement was performed at n = 50, and the ratio (%) at which the resistance value was 100 MΩ or more was determined.

(Example 2)
In [Production of Resin Particles] in Example 1, resin particles (2) were dispersed in the same manner as in Example 1 except that 160 parts of MMA and 40 parts of DVB were mixed in preparing the monomer composition. A resin particle dispersion (2) was obtained. The particle diameter of the resin particles (2) in this dispersion was measured in the same manner as in Example 1. As a result, the volume average particle diameter was 140 nm and the coefficient of variation was 9%.
Next, in Example 1 [Production of insulated conductive particles], the insulated conductive film was used in the same manner as in Example 1 except that the resin particle dispersion liquid (2) was used instead of the resin particle dispersion liquid (1). Conductive particles (2) were obtained, and in Example 1 [Production of anisotropic conductive material], the insulated conductive particles (2) were used instead of the insulated conductive particles (1). In the same manner as in Example 1, an anisotropic conductive adhesive (2) was obtained.
Evaluation similar to Example 1 was performed about the obtained anisotropic conductive adhesive. The results are shown in Table 1.

( Reference Example 3)
In the preparation of the resin composition in Example 1, the resin particles (3) were dispersed in the same manner as in Example 1 except that 180 parts of MMA and 20 parts of DVB were mixed. A resin particle dispersion (3) was obtained. The particle diameter of the resin particles (3) in this dispersion was measured in the same manner as in Example 1. As a result, the volume average particle diameter was 130 nm and the coefficient of variation was 3%.
Next, in Example 1 [Production of insulated conductive particles], the insulated conductive film was used in the same manner as in Example 1 except that the resin particle dispersion liquid (3) was used instead of the resin particle dispersion liquid (1). Conductive particles (3) were obtained, and in Example 1 [Production of anisotropic conductive material], the insulated conductive particles (3) were used instead of the insulated conductive particles (1). An anisotropic conductive adhesive (3) was obtained in the same manner as in Example 1.
Evaluation similar to Example 1 was performed about the obtained anisotropic conductive adhesive. The results are shown in Table 1.

( Reference Example 4)
In [Production of resin particles] in Example 1, resin particles (4) were dispersed in the same manner as in Example 1 except that 190 parts of MMA and 10 parts of DVB were mixed in preparing the monomer composition. A resin particle dispersion (4) was obtained. The particle diameter of the resin particles (4) in this dispersion was measured in the same manner as in Example 1. As a result, the volume average particle diameter was 123 nm and the coefficient of variation was 9%.
Next, in Example 1 [Production of insulated conductive particles], the insulated conductive film was used in the same manner as in Example 1 except that the resin particle dispersion (4) was used instead of the resin particle dispersion (1). Conductive particles (4) were obtained, and in Example 1 [Production of anisotropic conductive material], the insulated conductive particles (4) were used instead of the insulated conductive particles (1). In the same manner as in Example 1, an anisotropic conductive adhesive (4) was obtained.
Evaluation similar to Example 1 was performed about the obtained anisotropic conductive adhesive. The results are shown in Table 1.

(Example 5)
The same as Example 1 except that the amount of polyoxyethylene styrenated phenyl ether sulfate ammonium salt used as the surfactant in [Production of conductive particles] in Example 1 was changed from 2 parts to 5 parts. Thus, polymer particles were obtained. When the particle size of the polymer particles was measured with a particle size distribution analyzer (“Coulter Multisizer III type” manufactured by Beckman Coulter, Inc.), the number average particle size was 1.8 μm and the coefficient of variation was 4.2%. Conductive particles (2) having a metal layer thickness of 0.1 μm and a number average particle diameter of 2.0 μm, as in Example 1, except that the polymer particles were used as base particles. Got.
Then, in [Production of insulated conductive particles] in Example 1, insulated conductive particles were obtained in the same manner as in Example 1 except that the conductive particles (2) were used instead of the conductive particles (1). Example 5 was obtained, except that the insulated conductive particles (5) were used in place of the insulated conductive particles (1) in Example 1 [Production of anisotropic conductive material]. In the same manner, an anisotropic conductive adhesive (5) was obtained.
Evaluation similar to Example 1 was performed about the obtained anisotropic conductive adhesive. The results are shown in Table 1.

(Comparative Example 1)
A resin for comparison was prepared in the same manner as in Example 1 except that 180 parts of MMA and 20 parts of ethylene glycol dimethacrylate were mixed in preparing the monomer composition in [Production of Resin Particles] in Example 1. A resin particle dispersion (C1) in which the particles (C1) were dispersed was obtained. The particle diameter of the resin particles (C1) in this dispersion was measured in the same manner as in Example 1. As a result, the volume average particle diameter was 150 nm and the coefficient of variation was 8%.
Next, in Example 1 [Production of insulated conductive particles], the insulated conductive film was used in the same manner as in Example 1 except that the resin particle dispersion liquid (C1) was used instead of the resin particle dispersion liquid (1). Conductive particles (C1) were obtained, and in Example 1 [Production of anisotropic conductive material], the insulated conductive particles (C1) were used in place of the insulated conductive particles (1). An anisotropic conductive adhesive (C1) was obtained in the same manner as in Example 1.
Evaluation similar to Example 1 was performed about the obtained anisotropic conductive adhesive. The results are shown in Table 1.

(Comparative Example 2)
Resin particles for comparison (C2) were prepared in the same manner as in Example 1 except that 180 parts of styrene and 20 parts of DVB were mixed in preparing the monomer composition in [Production of resin particles] in Example 1. A resin particle dispersion liquid (C2) in which is dispersed) was obtained. The particle diameter of the resin particles (C2) in this dispersion was measured in the same manner as in Example 1. As a result, the volume average particle diameter was 145 nm and the coefficient of variation was 10%.
Then, in [Production of insulated conductive particles] in Example 1, insulated conductive material was obtained in the same manner as in Example 1 except that the resin particle dispersion (C2) was used instead of the resin particle dispersion (1). Conductive particles (C2) were obtained, and in Example 1 [Production of anisotropic conductive material], the insulated conductive particles (C2) were used in place of the insulated conductive particles (1). In the same manner as in Example 1, an anisotropic conductive adhesive (C2) was obtained.
Evaluation similar to Example 1 was performed about the obtained anisotropic conductive adhesive. The results are shown in Table 1.

From Table 1, when the resin particles of the present invention comprising the MMA-DVB copolymer as in Examples 1 , 2 and 5, the surface of the conductive particles is coated to form insulated conductive particles. The insulated conductive particles are uniformly dispersed without agglomerating in the conductive connection structure. As a result, in the conductive connection structure, the conduction between the opposing electrodes is kept good, and the lateral conduction is suppressed. I understand that I can do it.

Claims (7)

(Meth) acrylic resin particles that are present on the surface of the conductive particles and insulate the conductive particles, and are obtained by polymerizing a monomer composition containing methyl (meth) acrylate and divinylbenzene Resin particles comprising a crosslinked particle polymer, wherein the content ratio of divinylbenzene in the monomer composition is 14% by mass or more, and the average particle size is 123 nm or more and 500 nm or less . The resin particles according to claim 1, wherein an emulsion polymerization method is adopted for the polymerization. The resin particles according to claim 2 , wherein a redox polymerization initiator is used for the emulsion polymerization. The resin particle according to claim 2 , wherein an anionic emulsifier is used for the emulsion polymerization. Insulated conductive particles, wherein the resin particles according to any one of claims 1 to 4 are present on at least a part of the surface of the conductive particles. The insulated conductive particles according to claim 5 , wherein the conductive particles have an average particle diameter of 11 μm or less. An anisotropic conductive material, wherein the insulated conductive particles according to claim 5 or 6 are dispersed in a binder resin.