JP4050086B2 - Conductive particles, conductive materials, and anisotropic conductive films - Google Patents

Description

【００６８】
この結果から、本発明の導電性粒子は、絶縁樹脂層の溶出がほとんど無く、被覆樹脂層が芯材粒子に結合していることが確認された。粒子Ｉは、溶剤に可溶な樹脂を粒子に被覆しただけであり、溶剤により容易に溶出されることが確認された。
【００６９】
（ＩＴＯ付ガラス基板に対する導電性粒子の固着性能）
得られた粒子Ｃ，Ｅ，Ｇ，Ｈ，I を、それぞれイソプロピルアルコールに分散させ、ＩＴＯ付ガラス基板上に粒子を散布する。イソプロピルアルコールを室温にて蒸発させた後、この基板を絶縁樹脂層のガラス転移温度Ｔｇ以上の温度（１２０℃）に加熱し、１２０℃で６０秒静置する。この基板を室温まで冷却後、この基板上の粒子の確認を行い、基板上部６ｍｍの所から窒素ガスを１ｋｇ／ｃｍ^２にて１０秒間ブローさせる。窒素ブロー後に基板上に残っている粒子数をパーセンテージであらわす。
【００７０】
【表２】

【００７１】
（導通信頼性試験）
得られた各例の導電性粒子5 ｇを、エポキシ樹脂( 三井化学製、「ストラクトボンドXN-5Ａ」）100 ｇに混ぜ合わせ、ペーストを作成した。 該ペースト0.1 ｍｇを、ＩＴＯ膜が内面に形成された幅１０ｍｍの２枚のガラス基盤上を交差するように挟み、プレス機にて35ｋｇ／ｃｍ^２の圧力において80℃、30分仮圧着を行なった。この試験片を顕微鏡で観察し、粒子濃度の測定を行った後、この試験片に対し、粒子1 個あたり1gf の荷重となる様圧力を加え、1 ５０℃、４５分間熱圧着した。この試験片を顕微鏡で観察し、凝集粒子( 多重粒子) の有無を観察し、更に電気抵抗値を測定した。この試験片を高温側が８０℃、２時間、低温側が−２０℃、２時間を１サイクルとし、２００サイクル行なった後、再度この試験片の電気抵抗値の測定を行った。このときの電気抵抗値の変化を表２に示す。
【００７２】
本発明の導電性粒子Ｅ、Ｇ、Ｈは、粒子残存率が高く、基板に対する固着性の高いものであった。また、導通試験後の抵抗値の上昇が少なかった。
【００７３】
粒子Ｃは、導電性粒子の表面に金属被覆層が露出しているものであるが、基板に対する固着性が低く、かつ多重粒子が見られた。また、導通試験後に抵抗値が上昇した。比較例の粒子Ｉは、溶剤に可溶な樹脂を粒子に被覆しただけであり、粒子の基板への固着性は高かった。しかし、多重粒子が見られた。また、導通試験後に抵抗値が著しく上昇した。
【００７４】
【発明の効果】
以上述べたように、本発明によれば、導電性粒子を用いて端子間の電気的接続を行った場合に、端子間の間隙寸法の変化に追従でき、かつ粒子を混練したときに粒子からの樹脂の剥離や溶出の少ない導電性粒子を提供できる。
【図面の簡単な説明】
【図１】（ａ）は、芯材粒子４および金属被覆層２を模式的に示す正面図であり、（ｂ）は、芯材粒子４および金属被覆層２を模式的に示す断面図である。
【図２】（ａ）は、導電性粒子５を模式的に示す正面図であり、（ｂ）は、導電性粒子５を模式的に示す断面図である。
【図３】（ａ）は、芯材粒子４の表面４ａに水酸基が付着している状態を模式的に示し、（ｂ）は、モノマーＨＢ−Ｄと水酸基との反応を示し、（ｃ）は、モノマーと水酸基との反応後の状態を模式的に示す。
【図４】比較例の異方性導電構造１１を模式的に示す断面図である。
【図５】本発明例の異方性導電構造１１Ａを模式的に示す断面図である。
【図６】図５の構造１１Ａの要部拡大図である。
【符号の説明】
１ 金属被覆粒子 ２ 金属被覆層 ３ 隙間
４ 芯材粒子 ４ａ 芯材粒子４の表面 ５ 導電性粒子
６ 絶縁樹脂層 ７ 絶縁樹脂層６と芯材粒子４との反応界面
１１ 比較例の異方性導電構造 １１Ａ 本発明例の異方性導電構造
１２Ａ、１２Ｂ 基板 １３Ａ，１３Ｂ 端子 １４ 結着材 １５ 比較例の導電性粒子 １９ 比較例の異方性導電膜
１９Ａ 本発明例の異方性導電膜[0001]
BACKGROUND OF THE INVENTION
The present invention relates to conductive particles, a conductive material, and an anisotropic conductive film.
[0002]
[Prior art]
Conductive particles based on resin suitable for anisotropic conductive members are known. The patent documents are listed below.
In Japanese Patent Application Laid-Open Nos. 62-115679 and 62-188184, it is disclosed that a crosslinked polymer resin particle is coated with a metal to obtain conductive particles and applied to an anisotropic conductive connection structure. ing.
JP-A-9-115335 discloses an anisotropic conductive adhesive film in which conductive particles obtained by applying nickel / gold plating to crosslinked polystyrene particles are dispersed in an epoxy resin.
Japanese Patent Application Laid-Open No. 63-18096 discloses a technique for coating metal particles around a resin particle by an electroless plating method.
In the inventions described in Japanese Patent Application Laid-Open Nos. 1-224282 and 8-311655, a method of performing metal coating on resin particles by an electroless plating method is disclosed.
[0003]
In such conductive particles in which a metal film is formed on the resin particles, when the content of the conductive particles in the adhesive resin increases, multiple particles of the conductive particles are likely to be generated. There is a problem that leakage is likely to occur between adjacent terminals. For this reason, the technique which coat | covers the surface of electroconductive particle with resin as follows is known.
[0004]
(1) In Japanese Patent Application Laid-Open No. 62-176139, a conductive intermediate layer is formed on the surface of base particles made of resin, and this conductive film is covered with a thermoplastic resin. And the thermoplastic resin layer of the surface is torn at the time of thermocompression bonding, the conductive intermediate layer is exposed, and electrical connection is ensured.
(2) In Japanese Patent Application Laid-Open No. 7-105716, an insulating resin layer is formed by forming a conductive layer on an insulating core and covering 0.1 to 99.9% of the conductive layer on the conductive layer. Is forming.
(3) In Japanese Patent Application Laid-Open No. 2001-252553, a resin is dissolved in a solvent, conductive particles are introduced into the solvent, and the resin is coated on the conductive particles while volatilizing the solvent.
[0005]
[Problems to be solved by the invention]
(1) Since the insulating coating layer of the particles used in the anisotropic conductive connection material described in JP-A-62-176139 is a thermoplastic resin, the resin flows under high temperature and high humidity, and the connection terminals It enters and causes poor connection. Further, when the anisotropic conductive connecting material is molded, elution from the thermoplastic resin on the particle surface to the adhesive resin may occur, which may cause poor adhesion. Furthermore, the insulating resin is peeled off from the particles, and contact between the conductive particles occurs.
(2) The particles disclosed in Japanese Patent Application Laid-Open No. 7-105716 also have the same problem as described above when there are many insulating coating resin layers, and the insulating resin is fundamentally easily separated from the conductive particles. It includes the problem.
(3) In the invention described in Japanese Patent Application Laid-Open No. 2001-252553, in order to prevent the conductive particles from overlapping each other, the insulating resin is dissolved in a solvent and the conductive particles are coated with the resin. However, in the conductive connecting member, when the particles are kneaded with the adhesive resin, the non-crosslinked resin that dissolves in the solvent dissolves and mixes in the adhesive resin, and inhibits the curing of the adhesive resin, thereby ensuring the reliability of the conductive connection. Drop sex.
In the inventions described in JP-A-1-2422782 and JP-A-8-31655, there is no means for improving physical adhesion between the resin particles and the metal layer. For this reason, there has been a problem that the metal layer is peeled off from the particles when a shearing force is applied to the particles when the agglomeration generated during plating is crushed. If it is a normal resin layer, etching can be performed to improve adhesion, and the adhesion between the metal layer and the resin layer can be enhanced by the anchor effect. However, etching is difficult for fine particles, and the etching of the resin particles is difficult. Impairs physical properties.
[0006]
Furthermore, in connection reliability tests by heat cycle, in order to prevent conductive connection failure due to the change in the gap between the connection terminals, generally use conductive particles with metal coating on resin particles with resilience, and as adhesive resin Uses a curing shrinkable adhesive. However, even in such a combination, the resin particles have a compression history, so there is a limit in the amount of restoration, and in long-term reliability tests, the conductive particles cannot follow the change in the gap, resulting in poor connection. There was a case.
[0007]
The problem of the present invention is that when conducting electrical connection between terminals using conductive particles, it is possible to follow the change in the gap size between the terminals, and when the particles are kneaded, the resin is peeled off or eluted. It is an object of the present invention to provide conductive particles having a low content.
[0008]
[Means for Solving the Problems]
The present invention includes a core material particle, a metal coating layer formed on the core material particle, and an insulating resin layer formed on the metal coating layer. The insulating resin layer is made of a graft resin. In addition, the present invention relates to conductive particles characterized by being chemically bonded to core particles.
[0009]
In a preferred embodiment, It has a core particle, a metal coating layer formed on the core particle, and an insulating resin layer formed on the metal coating layer, and the insulating resin constituting the insulating resin layer can be dissolved. In an elution test using a simple solvent, the elution amount is 2.0% or less.
[0010]
The present invention also relates to a conductive material comprising the conductive particles and a binder that binds the conductive particles. The conductive material is a different material made of the conductive material. This relates to the isotropic conductive film.
[0011]
The present inventor has formed an insulating resin having an adhesive ability to an external material, for example, a connection terminal, after forming a metal coating layer on the core resin particles and then grafting the core coating resin particles on the metal coating layer. It was conceived to form on a coating layer.
[0012]
In the conductive particles of the present invention, since the insulating resin is formed on the metal coating layer, the insulating resin can be easily mixed with the adhesive resin, and can be easily mixed with the adhesive resin. it can. Therefore, the conductive particles can be uniformly dispersed in the adhesive resin, and a conductive material without multiple particles can be produced. In particular, when the particles of the present invention are used in an anisotropic conductive structure, current leakage between adjacent connection terminals can be prevented.
[0013]
In addition, since the metal coating layer is covered with the insulating resin, the insulating resin easily adheres to the terminals, and the insulating resin is chemically bonded to the core particles. It is easy to follow changes in the gap size. Therefore, the conductive material of the present invention is excellent in connection stability.
[0014]
And the electroconductive particle of this invention is excellent in the adhesiveness of a core material particle and a metal coating layer. This is because the metal coating layer is sandwiched between the core material particles and the insulating resin and fixed by the insulating resin bonded to the core material particles. In addition, the insulating resin layer is not only attached to the metal coating layer but also chemically bonded to the core material particles that are the base of the metal coating layer. Therefore, even if it uses at the temperature more than the glass transition point of an insulating resin layer, it does not peel.
[0015]
In the present invention, it is possible to provide conductive particles having an elution amount of 2.0% or less in an elution test using a solvent capable of dissolving the insulating resin constituting the insulating resin layer. When used, even when a shearing force is applied, the graft resin is hardly peeled off from the particles, and the adhesive strength to the terminal can be kept high.
[0016]
The solvent in which the insulating resin can be dissolved varies depending on the type of the insulating resin. However, the insulating resin is soluble in at least one of toluene, tetrahydrofuran, ethyl acetate, dimethylformamide, and methanol. Therefore, when any of toluene, tetrahydrofuran, ethyl acetate, dimethylformamide, and methanol is used, if the elution amount is 2.0% or less, the requirement of the present invention is satisfied. However, when the insulating resin is insoluble in some solvents among toluene, tetrahydrofuran, ethyl acetate, dimethylformamide, and methanol, the insulating resin is not likely to elute above 2% for the solvent. There is no need for measurement.
[0017]
From the viewpoint of the present invention, the elution amount is more preferably 1.5% or less. The measurement conditions for the elution amount will be described in detail in the items of the examples.
[0018]
In addition, the type of chemical bond between the graft resin and the core particle is not limited, but a covalent bond is preferable, a covalent bond by hydrogen abstraction in a radical reaction, an amide bond by a reaction between a carboxylic acid and an amino group, an imino group, Examples include ester bonds resulting from the reaction between carboxylic acids and alcoholic hydroxyl groups, urethane bonds resulting from reactions between isocyanates and hydroxyl groups, urea bonds resulting from reactions between isocyanates and amino groups, and imino groups, and siloxane bonds resulting from silane coupling agents. .
[0019]
DETAILED DESCRIPTION OF THE INVENTION
In order to manufacture the electroconductive particle of this invention, Preferably, it is based on the following method. As shown in FIGS. 1A and 1B, core material particles 4 are prepared. Functional groups are introduced into the surface 4 a of the core material particles 4, and then the metal coating layer 2 is formed on the core material particles 4. At this time, gaps 3 are generated in the metal coating layer 2 to obtain metal-coated particles 1. At this stage, functional groups remain on the surfaces 4 a of the core material particles 4 in the gaps 3 of the metal coating layer 2.
[0020]
Next, a graft resin is generated on the metal coating layer 2 using a reactive molecule capable of reacting with a functional group on the surface 4 a of the core particle 4 as a starting point. Thereby, the electroconductive particle 5 shown to Fig.2 (a), (b) is obtained. In the particles 5, an insulating resin layer 6 made of a graft resin is generated starting from the gap 3.
[0021]
The material of the core particle 4 is not particularly limited, but a polymer and an organic / inorganic hybrid material are preferable. Examples of polymers include linear polymers such as polystyrene, polymethyl methacrylate, polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polysulfone, polycarbonate, and polyamide; divinylbenzene, hexatriene, divinyl ether, divinylsulfone, diallylcarbinol, Alkylene diacrylate, oligo or polyalkylene glycol diacrylate, oligo or polyalkylene glycol dimethacrylate, alkylene triacrylate, alkylene tetraacrylate, alkylene trimethacrylate, alkylene tetramethacrylate, alkylene bisacrylamide, alkylene bismethacrylamide, both end acrylic modified polybutadiene Oligomer alone or other polymerizable Reticulated polymer obtained by polymerizing a Nomar; phenol-formaldehyde resins, melamine formaldehyde resins, benzoguanamine-formaldehyde resins, and thermosetting resins such as urea-formaldehyde resins.
[0022]
The polymerization method of the polymer is not limited, and may be a suspension polymerization method, a seed polymerization method, a dispersion polymerization method, or an emulsion polymerization method.
[0023]
Organic / inorganic hybrid materials include a copolymer of (meth) acrylate having a silyl group in the side chain and a vinyl monomer such as styrene or methyl methacrylate, and then condensation reaction of the silyl group; A sol-gel reaction of tetraethoxysilane, triethoxysilane, diethoxysilane, etc. in the presence of coalescence; a sol-gel reaction of tetraethoxysilane, triethoxysilane, diethoxysilane, etc., followed by firing at a low temperature What left the organic component by performing is mentioned.
[0024]
The shape of the core particle 4 is not limited, and may be a true spherical shape, a spheroid, a polyhedron, a needle shape, a fiber shape, a whisker, a columnar shape, a cylindrical shape, or an indefinite shape.
[0025]
The average particle diameter of the core particle 4 is preferably 1 to 1000 μm, and more preferably 2 to 500 μm. The average particle diameter of the core material particles 4 is a diameter when the core material particles are spherical, and a long diameter when the core material particles are spheroidal. The average particle diameter is a value obtained by observing and measuring 300 arbitrary core material particles with an electron microscope.
[0026]
The coefficient of variation (CV value) in the particle size distribution of the core particles is preferably 5% or less, and more preferably 3% or less. When the CV value exceeds 5%, the particle diameters of the core material particles are not uniform. Therefore, when the electrical connection is made by the conductive particles produced using the core material particles, conductive fine particles that are not involved in the connection are generated. In addition, a leak phenomenon may occur between adjacent electrodes.
[0027]
The CV value is the following formula (1);
CV value (%) = (σ / Dn) × 100 (1)
(In the formula, σ represents a standard deviation of the particle diameter, and Dn represents a number average particle diameter). The standard deviation and the number average particle diameter are values obtained by observing and measuring 300 arbitrary resin base particles with an electron microscope.
[0028]
The means for forming the metal coating layer is not particularly limited. However, a method in which the metal crystal grows in a granular form is preferable, and an electroless plating method and an electroplating method are particularly preferable.
[0029]
The thickness of the metal coating layer 2 is preferably 0.025 μm or more, more preferably 0.05 μm or more, from the viewpoint of reducing the resistance value of the conductive particles. Further, from the viewpoint of production cost, it is preferably 10 μm or less, and more preferably 1 μm or less.
[0030]
The metal coating layer 2 may have a single layer structure or a laminated structure of two or more layers.
[0031]
As a metal which comprises the metal coating layer 2, the metal which belongs to IB group, VIII group, IIB group, IIIB group, IVB group, VB group etc. in a periodic table is mentioned. As the group IB, copper, silver, gold and alloys thereof are preferable. As the group VIII, nickel, palladium, platinum and alloys thereof are preferable. As group IIB, zinc and zinc alloys are preferred. As the group IIIB, gallium, aluminum, indium and alloys thereof are preferable. As the IVB group, tin, lead and alloys thereof are preferable. As the group VB, bismuth and bismuth alloys are preferable.
[0032]
Below, nickel-gold plating which is an example of a metal coating layer is demonstrated. In nickel-gold plating, after electroless nickel plating is performed on the surface of the core material particles, a gold plating layer is formed on the surface portion by substitution plating. The electroless nickel plating includes a catalyst application step and a nickel reduction plating step.
[0033]
In the catalyst application step, a catalyst serving as a nucleus of plating is deposited or adsorbed on the surface of the core material particles. In this case, it is preferable to use a platinum group metal compound. Specifically, after the core particles are immersed in a hydrochloric acid solution of stannous chloride, they are further immersed and heated in a hydrochloric acid solution of palladium chloride and washed with water. In the particles thus obtained, palladium is precipitated as fine particles having a particle size of 50 nm or less.
[0034]
Alternatively, the core particles may be immersed in a mixed solution of tin chloride and palladium chloride, and then tin may be eluted and removed using hydrochloric acid or a sulfuric acid aqueous solution. Also in this case, palladium fine particles are deposited on the particle surfaces as described above.
[0035]
Furthermore, core particles having a graft polymerization layer may be immersed in a mixed aqueous solution of palladium chloride, a water-soluble monomer such as polyvinyl pyrrolidone, polyacrylamide, and polyvinyl pyridine, and ascorbic acid (Japanese Patent Laid-Open No. 61-166777). See the official gazette). Also in this case, palladium fine particles are deposited on the particle surfaces as described above.
[0036]
Next, nickel reduction plating is performed using the core material particles provided with the catalyst by the above method. As a method for performing the nickel reduction plating, a known method (“Latest Electroless Plating Technology” issued; General Technology Center, 1986, page 43, etc.) can be used, and both acidic plating and alkaline plating are used. be able to. When acidic plating is used as the nickel reduction plating, the nickel reduction is performed while immersing the catalyst-treated particles in a nickel chloride or nickel sulfate solution and dropping the sodium hypophosphite solution under pH 4-6 conditions. By performing the above, a nickel plating layer can be formed on the particle surface.
[0037]
When alkaline plating is used, a nickel plating layer can be formed on the particle surface by reducing nickel while dropping boric acid or a borax solution under conditions of pH 8-10. The nickel reduction reaction in the nickel reduction plating proceeds on the ultrafine palladium particles existing on the surface of the core material particles, thereby forming a nickel plating layer.
[0038]
Next, a gold plating layer is formed on the particles on which the nickel plating layer is formed by displacement plating. The gold plating is performed by partially eluting nickel and depositing gold on the surface of the nickel plating layer. Specifically, it is performed by putting particles having a nickel plating layer into a solution composed of potassium cyanide alloy, EDTA and ammonium chloride and heating them.
[0039]
The metal coating layer 2 has a gap 3 through which a monomer as a raw material for the graft resin can enter. The size of the gap 3 is preferably 1 nm or more, and more preferably 2 nm or more, from the viewpoint of promoting the entry of monomer molecules. On the other hand, if the gap 2 is too large, defects are likely to occur in the metal coating layer when a load is applied to the metal coating layer during the compression deformation of the particles. Therefore, from this viewpoint, the size of the gap 3 is preferably 1 μm or less, and more preferably 0.5 μm or less.
[0040]
Further, the area of the gap 3 preferably accounts for 0.10% or more of the surface area of the core particles from the viewpoint of covering the entire metal coating with the insulating resin layer, and accounts for 0.12% or more. More preferably. Moreover, when the area of the gap 3 becomes too large, defects are likely to occur in the metal coating layer when a load is applied to the metal coating layer during particle compression deformation. From this viewpoint, it is preferably 5.0% or less, and more preferably 1.0% or less.
[0041]
The thickness of the insulating resin layer 6 made of the graft resin is preferably 0.002 μm or more, and more preferably 0.01 μm or more, from the viewpoint of adhesion to an external member. However, if the insulating resin layer 6 is thick, the resin tends to remain between the particles and the terminals at the time of conductive connection, which may cause a connection failure. Therefore, the thickness of the insulating resin layer 6 is preferably 1 μm or less. 5 μm or less is more preferable.
[0042]
Examples of the graft polymerization on the particle surface include the methods described in the following documents.
"The latest powder material design" (Techno System Co., Ltd.), page 203
“Graft Polymerization and its Applications”, Fumio Ide, Polymer Publishing Society, 1984
Japanese Patent Laid-Open No. 9-244034
[0043]
Moreover, the following method can be illustrated.
Unsaturated bonds such as double bonds existing on the surface of the core particles are cleaved using a radical polymerization initiator, and a vinyl monomer is graft polymerized.
A radical is generated on the surface of the core material particle having a reducing group such as an alcoholic hydroxyl group on the surface by an oxidizing agent such as cerium salt (IV) or periodate, and the vinyl monomer is graft-polymerized starting from the radical.
Graft polymerization using redox catalysts such as persulfate-lithium halide, persulfate-acid sulfite, persulfate-Ag, persulfate-hydroxyl, hydrogen peroxide-metal salt .
Graft polymerization is performed starting from a functional group such as a perester group, a mercapto group, or a diazo group.
The surface of the core material particles is activated by physical means such as low-temperature plasma, electron beam, or gamma ray irradiation, and then the polymerizable monomer is graft polymerized.
The graft polymer is bonded to a reactive group such as an amino group or a hydroxyl group present on the surface of the core particle by a polymer reaction.
[0044]
In a particularly preferred embodiment, the graft polymer is produced by monomer graft polymerization, and the monomer graft polymerization proceeds from a vinyl group or a polymerization initiator present on the surface of the particle body. To do. The present applicant has developed a method for introducing a vinyl group on the particle surface and a method for introducing a radical active site, and disclosed a method for forming a graft chain based on a vinyl group or a radical active site (Japanese Patent Laid-Open No. 5-232480). No. 7, JP-A-7-300587, JP-A-7-301810, JP-A-7-300586). The methods described in these documents can be used in the present invention.
[0045]
A method for introducing a vinyl group or a radical active site on the surface of the core particle is not limited, and the methods described in the above-mentioned publications can be used. For example, as shown in FIG. 3A, a hydroxyl group is introduced into the surface of the core material particle 4 and then the metal coating layer 2 is provided. Next, as shown in FIG. 3B, a monomer XB-D having a functional group X having a reactive activity with a hydroxyl group is reacted with the hydroxyl group. Here, B is a main body part of the monomer, and D is a vinyl group or a radical active point. By reaction between the active hydrogen of the monomer and the hydroxyl group, the D group is introduced to the particle surface as shown in FIG.
[0046]
When introducing a hydroxyl group into the particle surface, the core material particles are preferably impregnated with a compound capable of forming an interpenetrating polymer network and reacted. By performing such treatment, the bonding of the insulating resin layer to the core material particles can be further strengthened, and the resistance to the shearing force of the particles can be further improved.
[0047]
The “compound capable of forming an interpenetrating polymer network” is a compound that can be impregnated into particles and can form an interpenetrating polymer network by heating inside the particles. , Not limited. In a preferred embodiment, the compound has a plurality of functional groups that can cross-link with each other. As described above, the compound has a plurality of functional groups, and a cross-linking reaction proceeds in each functional group, thereby generating an interpenetrating polymer network structure. Examples of such functional groups include the following. One type or two or more types of these functional groups are included in one compound.
Epoxy group, hydrolyzable silyl group, carboxyl group, hydroxyl group, amino group, imino group
[0048]
Examples of the compound having an epoxy group include the following.
Ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerin diglycidyl Ether, trimethylolpropane triglycidyl ether, triglycidyl tris (2-hydroxyethyl) isocyanurate, sorbitol polyglycidyl ether, sorbitan polyglycidyl ether, pentaerythritol polyglycidyl ether, 3-glycididoxypropyltrimethoxysilane, 3, 4 -Epoxybutyltrimethoxysilane, 2- (3,4-epoxy Cyclohexyl) ethyltrimethoxysilane
[0049]
Examples of the compound having a hydrolyzable silyl group include the following.
Tetraethoxysilane, 2-trimethoxysilylethyltrimethoxysilane, 6-trimethoxysilylhexamethylenetrimethoxysilane, p-dimethoxysilylethylbenzene, di-3-trimethoxysilylpropyl terephthalate, di-3-trimethoxy adipate Silylpropyl, tri-3-methyldimethoxysilylpropyl isocyanurate
[0050]
Examples of the bond forming the interpenetrating polymer network structure include an ether bond, a siloxane bond, and a combination of an ether bond and a siloxane bond.
[0051]
Examples of the monomer used for producing the graft resin include styrene, α-methylstyrene, methyl acrylate, methyl methacrylate, isobutyl methacrylate, acrylonitrile, vinyl pyrrolidone, glycidyl methacrylate, lauryl methacrylate, stearyl methacrylate, and acetic acid. Examples thereof include polymerizable vinyl monomers such as vinyl, vinyl chloride, ethylene, propylene, butadiene, isoprene, allyl phthalate, methacryloxymethyltrimethoxysilane, and methacryloxypropyltriethoxysilane. Furthermore, the following can be illustrated.
Dimethylacrylamide, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, dimethylaminopropyl acrylamide, dimethylaminopropyl methacrylamide, acryloylmorpholine, N-isopropylacrylamide, diethylacrylamide, methacryloyloxyethyltrimethylammonium chloride, methacryloyloxyethylbenzyldimethylammonium Nitrogen-containing cationic monomers such as chloride, acryloyloxyethyltrimethylammonium chloride, acryloyloxyethylbenzyldimethylammonium chloride, acrylamidopropyltrimethylammonium chloride; ammonium α-sulfonate-ω-1- (allyloxymethyl) alkyloxypoly Oxyeth Sulfonic acid anionic vinyl monomers such as sodium, sodium p-styrene sulfonate, sodium vinyl sulfonate, sodium 2-methacryloyl ethyl sulfonate, sodium acrylamido-2-methylpropane sulfonate; 2-acryloyloxyethyl acid Phosphoric acid-based anionic vinyl monomers such as phosphate, 2-methacryloyloxyethyl acid phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate; click acid, methacrylate acid, methacrylic acid dimer Carboxylic acid type anionic vinyl monomers such as
[0052]
Furthermore, the vinyl monomer which has the following hydrophilic functional groups can be illustrated, for example. Hydroxyl group-containing monomers such as 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, glycerol monomethacrylate; polyethylene glycol monomethacrylate, polyethylene glycol monoacrylate, polypropylene glycol monomethacrylate, methoxypolyethylene glycol monomethacrylate, Polyether-containing monomers such as methoxypolyethylene glycol monoacrylate; Epoxy-containing monomers such as glycidyl methacrylate and glycidyl acrylate.
The above examples of the monomers do not limit the present invention. Two or more types of monomers may be mixed.
[0053]
Since the electroconductive particle by this invention has the outstanding electroconductivity, the electroconductive material which has the outstanding electroconductivity is obtained by mixing in binders, such as resin. Such a conductive material can be suitably used as a film-like antistatic film or an anisotropic conductive film that can be used in a portion where electrical bonding is performed in an electronic circuit.
[0054]
Binders (adhesives) constituting such conductive materials include polyethylene, polypropylene, polystyrene, polycarbonate, polyurethane, polyester, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyamide, polyimide, acrylic resin, and methacrylic resin. And epoxy resin, phenol resin, silicon resin, fluorine resin, nylon resin, ethylene / vinyl acetate resin, styrene / acrylonitrile resin, acrylonitrile / butadiene / styrene resin.
[0055]
Moreover, a conductive material can be produced by mixing the conductive particles of the present invention with insulating particles and press-molding them. Examples of such insulating particles include the particles listed in the above-mentioned item of core material particles, and plastic particles, and further, thermoplastic plastic particles are particularly preferable.
[0056]
The case where the conductive particles of the present invention are applied to an anisotropic conductive film will be further described. When the anisotropic conductive structure is manufactured, as shown in FIG. 4, a pair of substrates 12A and 12B provided with terminals 13A and 13B having a predetermined pattern are prepared. Then, an anisotropic conductive film 19 is sandwiched between a pair of substrates, and pressure is applied under heat to perform pressure bonding. The anisotropic conductive film 19 includes a binder 14 and conductive particles 15 dispersed in the binder 14. Here, when the surface of the conductive particles 15 is made of a metal coating layer, if the distance between the substrates 12A and 12B varies, a gap 16 is generated between the particles 15 and the terminals 13A and 13B. Defects occur.
[0057]
On the other hand, as shown in FIGS. 5 and 6, in the case of the anisotropic conductive structure 11A using the conductive particles 5 of the present invention, the surface of the conductive particles 5 is coated with the graft resin 6. The conductive particles 5 adhere to the terminals 13A and 13B. Thus, when the distance between the substrates 12A and 12B varies, the gap 16 is unlikely to occur between the particles 15 and the terminals 13A and 13B.
[0058]
【Example】
Hereinafter, although a specific experimental result is illustrated, this invention is not limited to this Example.
[0059]
(Production of crosslinked polymer particle B)
A 2 L separable flask is charged with 400 g of a 3.5% polyvinylpyrrolidone methanol solution, 42 g of styrene, and 63 g of p-trimethoxysilylstyrene, and heated to 60 ° C. with gentle stirring under a nitrogen stream. Add 4 g of azobisisobutyronitrile and allow to react for 12 hours. After cooling to room temperature after completion of the reaction, 200 g of a 5% aqueous solution of potassium hydroxide was added, followed by stirring at 60 ° C. for 2 hours for hydrolysis and crosslinking reaction. The obtained particles were washed to obtain particles A. To 20 g of particles A, 20 g of a toluene solution in which 10 g of an interpenetrating polymer network forming compound (2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane) was dissolved was added and impregnated with epoxy. Next, the epoxy-impregnated particles were heated at 200 ° C. for 16 hours and then washed to obtain crosslinked polymer particles B having a hydroxyl group derived from an epoxy group on the particle surface 4a. The average particle size of the particles B was 5.20 μm, and the coefficient of variation was 3%.
[0060]
(Production of metal-coated particles C)
The particles B were electrolessly copper-plated by a known method to obtain metal-coated particles C having an average particle size of 5.40 μm and a plating film thickness of 0.10 μm. The particle C corresponds to the stage of FIG. By SEM, countless 1-100 nm holes were confirmed on the surface of the metal-coated particles C, and the area of the gap was 0.13%.
[0061]
(Preparation of metal-coated particles D with vinyl groups introduced on the surface)
3 g of a 30% toluene solution of methacryloyl isocyanate (HB-D in FIG. 3 (b)) and 20 g of methyl ethyl ketone are charged all at once to 10 g of the metal-coated particle C, and reacted at room temperature for 30 minutes to form a core material for the hole in the metal layer Metal-coated particles D having vinyl groups introduced on the particle surfaces were obtained. The particle D corresponds to FIG.
[0062]
(Example of the present invention: Production of resin-coated conductive particles E)
100 g of methyl ethyl ketone, 1 g of polymerization initiator benzoyl peroxide, 30 g of methyl methacrylate, 10 g of lauryl methacrylate, 10 g of 2-hydroxyethyl methacrylate (Tg of copolymer polymer is 44 ° C.) are collectively charged into 10 g of metal-coated particles D, and a nitrogen stream The mixture was reacted at 80 ° C. for 2 hours, washed with methyl ethyl ketone, and dried to obtain particles E in which a graft polymerization chain was formed starting from the vinyl group. It was confirmed that the average particle diameter of the obtained particles E was 5.44 μm, and the thickness of the resin layer 6 on the metal coating layer 2 was 0.02 μm. The obtained particles E were uniformly coated, and multiple particles were not observed.
[0063]
(Example of the present invention: Production of resin-coated conductive particles G)
3 g of a 30% toluene solution of methacryloyl isocyanate and 20 g of methyl ethyl ketone are added all at once to the obtained particle E10 g and reacted at room temperature for 30 minutes to obtain particles F in which the primary side chain vinyl group of the graft polymerization chain is introduced. It was. 100 g of methyl ethyl ketone, 1 g of polymerization initiator benzoyl peroxide, 30 g of methyl methacrylate, 10 g of lauryl methacrylate, and 10 g of 2-hydroxyethyl methacrylate (Tg of the copolymerized polymer is 44 ° C.) are charged all at once to the particle F10 g. When the reaction was carried out at 2 ° C. for 2 hours, particles G in which the graft polymer chain was formed starting from the vinyl group were obtained. It was confirmed that the average particle diameter of the obtained particles G was 5.52 μm, and the thickness of the resin layer on the metal coating layer was 0.06 μm. The obtained particles G were uniformly coated, and multiple particles were not observed.
[0064]
(Example of the present invention: Production of resin-coated conductive particles H)
100 g of methyl ethyl ketone, 1 g of polymerization initiator benzoyl peroxide, 25 g of methyl methacrylate, 10 g of lauryl methacrylate, 10 g of 2-hydroxyethyl methacrylate, 5 g of glycidyl methacrylate (copolymer polymer Tg is 38 ° C.) per 10 g of the metal-coated particles D After charging and reacting at 80 ° C. for 2 hours under a nitrogen stream, particles H in which a graft polymerization chain was formed starting from the vinyl group were obtained by washing with methyl ethyl ketone and drying. The average particle diameter of the obtained particles H was 5.44 μm, and the thickness of the resin layer on the metal coating layer was confirmed to be 0.02 μm. The obtained particles H were uniformly coated, and multiple particles were not observed.
[0065]
(Comparative Example: Production of resin-coated conductive particles I)
After adding 5 g of butyl acetate solution of 0.25 g of methacrylic acid ester copolymer (weight average molecular weight 10,000) having the same composition as the coating layer of particle H to the metal-coated particles C10 g, and dispersing the particles, Butyl acetate was gradually evaporated to obtain coated conductive particles I. When the particles I were observed with an optical microscope and SEM, the particles were uniformly coated, but some of the particles were observed.
[0066]
(Elution test of insulating resin layer)
Each particle E, G, H, I was dispersed in each solvent shown in Table 1. After applying ultrasonic waves for 30 minutes, the particles were removed from the solvent, filtered and dried. The difference between the initial weight of the particles and the weight after the test was measured, and the amount of change in weight was taken as the elution amount of insulating resin. The results are shown in Table 1.
[0067]
[Table 1]

[0068]
From this result, it was confirmed that the conductive particles of the present invention hardly had the elution of the insulating resin layer, and the coating resin layer was bonded to the core material particles. It was confirmed that the particles I were simply coated with a resin soluble in a solvent and were easily eluted by the solvent.
[0069]
(Fixing performance of conductive particles to glass substrate with ITO)
The obtained particles C, E, G, H, I are each dispersed in isopropyl alcohol, and the particles are dispersed on a glass substrate with ITO. After evaporating isopropyl alcohol at room temperature, the substrate is heated to a temperature (120 ° C.) equal to or higher than the glass transition temperature Tg of the insulating resin layer, and left at 120 ° C. for 60 seconds. After cooling the substrate to room temperature, the particles on the substrate are confirmed, and nitrogen gas is supplied at 1 kg / cm from the upper 6 mm of the substrate. ² For 10 seconds. The number of particles remaining on the substrate after nitrogen blowing is expressed as a percentage.
[0070]
[Table 2]

[0071]
(Continuity reliability test)
5 g of the conductive particles obtained in each example were mixed with 100 g of an epoxy resin (manufactured by Mitsui Chemicals, “Struct Bond XN-5A”) to prepare a paste. The paste 0.1 mg was sandwiched between two glass substrates 10 mm wide with an ITO film formed on the inner surface, and 35 kg / cm by a press. ² Temporary pressure bonding was carried out at 80 ° C. for 30 minutes at the pressure of After observing the test piece with a microscope and measuring the particle concentration, a pressure was applied to the test piece so that a load of 1 gf per particle was applied, and thermocompression bonding was performed at 150 ° C. for 45 minutes. This test piece was observed with a microscope, the presence or absence of aggregated particles (multiple particles) was observed, and the electrical resistance value was further measured. The test piece was subjected to 200 cycles with the high temperature side at 80 ° C. for 2 hours and the low temperature side at −20 ° C. for 2 hours for 200 cycles, and then the electrical resistance value of the test piece was measured again. Table 2 shows changes in the electric resistance value at this time.
[0072]
The conductive particles E, G, and H of the present invention had a high particle residual rate and high adhesion to the substrate. Moreover, there was little increase in the resistance value after the continuity test.
[0073]
The particles C were those in which the metal coating layer was exposed on the surfaces of the conductive particles, but the adhesion to the substrate was low, and multiple particles were observed. Further, the resistance value increased after the continuity test. The particles I of the comparative example were only coated with a resin soluble in a solvent, and the adhesion of the particles to the substrate was high. However, multiple particles were seen. Further, the resistance value significantly increased after the continuity test.
[0074]
【The invention's effect】
As described above, according to the present invention, when electrical connection between terminals is performed using conductive particles, it is possible to follow the change in the gap dimension between the terminals, and from the particles when the particles are kneaded. It is possible to provide conductive particles with less peeling and elution of the resin.
[Brief description of the drawings]
1A is a front view schematically showing core material particles 4 and a metal coating layer 2, and FIG. 1B is a cross-sectional view schematically showing core material particles 4 and the metal coating layer 2; is there.
2A is a front view schematically showing conductive particles 5, and FIG. 2B is a cross-sectional view schematically showing conductive particles 5. FIG.
3A schematically shows a state in which a hydroxyl group is attached to the surface 4a of the core particle 4, FIG. 3B shows a reaction between the monomer HB-D and the hydroxyl group, and FIG. Schematically shows the state after the reaction between the monomer and the hydroxyl group.
FIG. 4 is a cross-sectional view schematically showing an anisotropic conductive structure 11 of a comparative example.
FIG. 5 is a cross-sectional view schematically showing an anisotropic conductive structure 11A of an example of the present invention.
6 is an enlarged view of a main part of the structure 11A in FIG. 5;
[Explanation of symbols]
1 Metal-coated particle 2 Metal-coated layer 3 Gap
4 Core particle 4a Surface of core particle 4 5 Conductive particle
6 Insulating resin layer 7 Reaction interface between insulating resin layer 6 and core particle 4
11 Anisotropic Conductive Structure of Comparative Example 11A Anisotropic Conductive Structure of Inventive Example
12A, 12B Substrate 13A, 13B Terminal 14 Binder 15 Comparative Example Conductive Particles 19 Comparative Example Anisotropic Conductive Film
19A Anisotropic conductive film of inventive example

Claims (6)

  Core material particles, a metal coating layer formed on the core material particles, and an insulating resin layer formed on the metal coating layer, the insulating resin layer is made of a graft resin, and Conductive particles characterized by being chemically bonded to core particles.   The electroconductive particle according to claim 1, wherein an elution amount is 2.0% or less in an elution test using a solvent in which the graft resin can be dissolved. 2. The gap between the surface of the core material particles that is not covered with the metal coating layer is 0.1% or more and 5.0% or less of the total area of the core material particles. Or the electroconductive particle of 2. Introducing a vinyl group into the core material particles, wherein the insulating resin layer is formed of the vinyl group by graft polymerizing a polymerizable vinyl monomer as a starting point, according to claim 1 to 3 The electroconductive particle as described in any one claim. A conductive material comprising the conductive particles according to any one of claims 1 to 4 and a binder for binding the conductive particles. An anisotropic conductive film comprising the conductive material according to claim 5 .

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