JP2014080484A - Crosslinked polymer particle, conductive particle, anisotropic conductive material and connection structure for circuit member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crosslinked polymer particle which has excellent compression recovery under a heating environment while having low elasticity and has high breaking strength, and to provide a conductive particle using the same, an anisotropic conductive material and a connection structure for a circuit member.SOLUTION: There is provided a crosslinked polymer particle obtained by swelling seed particles containing poly methyl methacrylate in an emulsion containing a monomer including a specific di(meth)acrylate compound and then seed polymerizing the monomer, wherein an increasing rate of compression recovery represented by the expression of [(the compression recovery rate at 180°C)-(the compression recovery rate at room temperature)]/(the compression recovery rate at room temperature)×100 is -5% or more.

Description

  The present invention relates to a connection structure of crosslinked polymer particles, conductive particles, anisotropic conductive material, and circuit members.

  The method of mounting the liquid crystal driving IC on the glass panel for liquid crystal display can be roughly classified into two types, COG (Chip on Glass) mounting and COF (Chip on Flex) mounting. In COG mounting, an IC for liquid crystal is directly bonded onto a glass panel using an anisotropic conductive material containing conductive particles. On the other hand, in COF mounting, a liquid crystal driving IC is bonded to a flexible tape having metal wiring, and these are bonded to a glass panel using an anisotropic conductive material containing conductive particles. Note that the anisotropic conductive material here means a material that has conductivity in the pressurizing direction and maintains insulation in the non-pressurizing direction.

  When bonding using an anisotropic conductive material, the conductive particles are sufficiently deformed by the pressure at the time of bonding, and the conductive particles after deformation are deformed to maintain electrical connectivity. It needs to recover to the previous shape to some extent.

  Therefore, when the conductive particles are composed of polymer particles and a metal layer covering the polymer particles, the polymer particles have a reduced compression elastic modulus and are compressed so that the conductive particles can be easily recovered after deformation. It is required to have excellent recoverability.

  Patent Document 1 discloses that resin particles mainly composed of an acrylic resin composed of a monomer polymer containing a urethane compound and an acrylic monomer are largely deformed with a small load. Patent Document 2 reports the use of resin particles obtained by suspension polymerization of raw material monomers containing alkylene diol diacrylate in order to reduce the elastic modulus of the resin particles.

  However, in the suspension polymerization, the resin particles obtained are polydispersed and thus have a wide particle size distribution, and in order to be used for conductive particles, it is necessary to classify the resin particles before use, resulting in poor productivity. On the other hand, when seed polymerization is used, it is known that monodisperse resin particles are easily obtained. For example, Patent Documents 3 to 5 disclose resin particles using polystyrene as seed particles.

  Various resin particles using a (meth) acrylic resin as a seed resin have been studied. For example, Patent Document 6 discloses highly elastic regular particles formed by polymerization using methyl (meth) acrylate-based seed particles and a trifunctional polymerizable monomer. Patent Document 7 discloses that monodispersed particles are obtained by polymerizing seed particles made of (meth) acrylic acid ester containing an alkyl group having 6 or more carbon atoms or the like in an aqueous emulsion containing a polymerizable monomer. Has been. Patent Document 8 describes a method for producing resin particles having a step of swelling seed particles obtained by emulsion polymerization of an ethylenically unsaturated monomer such as butyl acrylate with a polyfunctional acrylate monomer.

International Publication No. 03/104285 Japanese Patent No. 4642286 JP 2005-327509 A Japanese Patent No. 3739232 JP 2010-159328 A Japanese Patent No. 3991093 JP 2001-2716 A Japanese Patent No. 4218848

  However, with conventional resin particles, it is difficult to achieve a sufficient level of compression characteristics such as compression recovery rate and compression fracture strength while maintaining low elasticity. In addition, since the conductive particles used for the anisotropic conductive material are heated at the time of mounting, the compression characteristics at the time of heating are also important. Therefore, the resin particles are required to have excellent compressive recoverability in a heating environment and have high breaking strength.

  Therefore, an object of the present invention is to provide a crosslinked polymer particle that has low elasticity but is excellent in compression recovery under a heating environment and has high breaking strength. Another object of the present invention is to provide a conductive particle produced from the crosslinked polymer particle, an anisotropic conductive material containing the conductive particle, and a connection structure for a circuit member.

［式（１）中、Ｒ^１及びＲ^２はそれぞれ独立に水素原子又はメチル基を示し、Ｌ^１は炭素数４〜１２のアルキレン基を示す。］
圧縮回復増加率（％）＝［（１８０℃での圧縮回復率）−（室温での圧縮回復率）］／（室温での圧縮回復率）×１００ （２） In the present invention, after seed particles containing polymethyl methacrylate are swollen in an emulsion containing a monomer containing a di (meth) acrylate compound represented by the following formula (1), the monomer is seed-polymerized. Provided is a crosslinked polymer particle, which is a crosslinked polymer particle and has an increase in compression recovery represented by the following formula (2) of -5% or more.

[In Formula (1), R ¹ and R ² each independently represent a hydrogen atom or a methyl group, and L ¹ represents an alkylene group having 4 to 12 carbon atoms. ]
Compression recovery increase rate (%) = [(compression recovery rate at 180 ° C.) − (Compression recovery rate at room temperature)] / (compression recovery rate at room temperature) × 100 (2)

  When the weight average molecular weight of the seed particles is 3000 to 50000, the monomer is easily absorbed when the seed particles swell.

  When the ratio of the remaining double bond is 0 to 15 mol%, the crosslinked polymer fine particles are more excellent in compression recovery under a heating environment.

  From the viewpoint of further improving the compression characteristics of the crosslinked polymer particles, the mass ratio of the di (meth) acrylate compound represented by the above formula (1) to the seed particles is preferably 20 to 300 times.

  When the compression recovery rate at 180 ° C. of the crosslinked polymer particles is 40% or more, it becomes easy to improve the conductive reliability when the circuit connection is made using the conductive particles produced from the crosslinked polymer particles.

  When the average particle diameter of the crosslinked polymer particles is 1 to 10 μm and the Cv value of the particle diameter is 15% or less, it becomes easy to produce conductive particles having good conductive reliability.

  The present invention also provides conductive particles having the crosslinked polymer particles and a metal film formed on the surface of the crosslinked polymer particles.

  The present invention further provides an anisotropic conductive material containing the conductive particles and a binder resin.

  According to the present invention, a first circuit member having a first circuit electrode formed on the main surface of the first circuit board, a second circuit electrode formed on the main surface of the second circuit board, A second circuit member disposed so that the two circuit electrodes face the first circuit electrode, and a connection portion interposed between the first circuit member and the second circuit member, and connected. A part provides the connection structure of a circuit member containing the electroconductive particle of the said invention.

  According to the present invention, it is possible to provide crosslinked polymer particles that are low in elasticity but excellent in compression recovery under a heating environment and have high breaking strength. Moreover, according to this invention, the connection structure of the electroconductive particle produced from this crosslinked polymer particle, the anisotropic conductive material containing this electroconductive particle, and a circuit member can be provided.

It is a schematic cross section which shows the electroconductive particle which concerns on this embodiment. It is a schematic cross section which shows the anisotropic conductive material which concerns on this embodiment. It is a schematic cross section which shows the preparation methods of the connection structure of the circuit member which concerns on this embodiment.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings as the case may be. However, the present invention is not limited to the following embodiments. In the drawings, the same or equivalent elements are denoted by the same reference numerals, and redundant description is omitted. In the present specification, “(meth) acryl” means acryl and methacryl corresponding to it, “(meth) acrylate” means acrylate and methacrylate corresponding to it, and “(meth) acryloyl” "Means acryloyl and the corresponding methacryloyl.

[Crosslinked polymer particles]
The crosslinked polymer particles of the present embodiment are obtained by swelling seed particles containing polymethyl methacrylate in an emulsion containing a monomer containing a specific di (meth) acrylate compound, and then seed polymerizing the monomer. The crosslinked polymer particles are characterized in that the compression recovery increase rate is -5% or more. Hereinafter, preferred embodiments of the crosslinked polymer particles satisfying the above-described configuration will be described.

(Seed particles)
The seed particles are particles obtained by polymerization of methyl methacrylate. As seed particles, particles made of polymethyl methacrylate, which is a homopolymer of methyl methacrylate, can be used, but from an acrylic resin obtained by copolymerization of methyl methacrylate with other (meth) acrylic acid esters. May be a particle. The acrylic resin may contain 90 mol% or more of methyl methacrylate as a monomer unit.

  The seed particles can be synthesized by a known method such as an emulsion polymerization method, a soap-free emulsion polymerization method, or a dispersion polymerization method.

  The seed particles containing polymethyl methacrylate can suppress the formation of large particles because the resin particles are aggregated and hardly fused. By using polymethyl methacrylate as seed particles, the interaction between the monomer and the di (meth) acrylate compound increases, so the breaking strength of the crosslinked polymer particles can be reduced by using polystyrene seed particles. In comparison, it is possible to improve. As a result, the conductive particles produced from the crosslinked polymer particles according to this embodiment can exhibit good compression characteristics. Here, the large particle means a particle having a particle size larger than the main peak when the particle size distribution of the crosslinked polymer particle is measured.

  When the weight average molecular weight (Mw) of the seed particles is increased, the absorption capacity of the monomer is decreased or the mechanical strength is easily decreased due to phase separation from the monomer, and when the seed particles are decreased, the particle size is not easily uniformed. Therefore, the Mw of the seed particles is preferably 3000 to 50000, more preferably 3000 to 40000, and still more preferably 3000 to 30000. In addition, Mw prescribed | regulated by this specification is the value measured using the analytical curve by a standard polystyrene by the gel permeation chromatography method (GPC).

  The average particle size of the seed particles can be adjusted according to the design particle size of the obtained crosslinked polymer particles. When the average particle size of the seed particles increases, it takes time to absorb the monomer, and when the average particle size decreases, the particle size becomes non-uniform and the sphericity tends to decrease. The average particle size of the seed particles is preferably 0.1 to 2.0 μm, more preferably 0.5 to 2.0 μm, and still more preferably 0.5 to 1.5 μm.

  The Cv value, which is the coefficient of variation of the particle size (diameter) of the seed particles, is preferably 10% or less, more preferably 7% or less, since the uniformity of the resulting crosslinked polymer particles tends to decrease as the seed particle size (diameter) increases. 5% or less is more preferable.

  The average particle size of the seed particles and the Cv value of the particle size can be calculated by observing 100 target particle particles with a scanning electron microscope (SEM) and measuring the particle size. It is also possible to calculate from the particle size measured using a particle size measuring device such as

(Method for producing crosslinked polymer particles)
Crosslinked polymer particles are obtained by swelling the seed particles in an emulsion containing a monomer containing a specific di (meth) acrylate compound and then seed-polymerizing the monomer. The seed polymerization method can be performed with reference to a known method. A general method of the seed polymerization method will be described below, but is not limited to this method.

  First, seed particles are added to an emulsion containing a monomer and an aqueous medium. The seed particles may be added directly to the emulsion or may be added in a form in which the seed particles are dispersed in an aqueous dispersion.

  The emulsion can be prepared by a known method. For example, an emulsion can be obtained by adding a monomer to an aqueous medium and dispersing the monomer in an aqueous medium using a fine emulsifier such as a homogenizer, an ultrasonic processor, or a nanomizer. The emulsion may contain a polymerization initiator as necessary. The polymerization initiator may be mixed in advance with the monomer and then dispersed in an aqueous medium, or a mixture of a polymerization initiator and a monomer separately dispersed in an aqueous medium may be mixed. When the particle size of the monomer droplets in the obtained emulsion is smaller than the particle size of the seed particles, the monomer is more easily absorbed into the seed particles.

  After the seed particles are added to the emulsion, the seed particles are swollen to absorb the monomer. This absorption can be normally performed by stirring the emulsion after adding the seed particles at room temperature for 1 to 24 hours. Moreover, absorption of a monomer can be accelerated | stimulated by heating an emulsion to about 30-50 degreeC.

  The seed particles swell upon absorption of the monomer. When the mixing ratio of the monomer to the seed particle is reduced, the increase in the particle size of the crosslinked polymer particle produced by the seed polymerization of the monomer is reduced, and the productivity of the crosslinked polymer particle tends to be lowered. On the other hand, when the mixing ratio of the monomer is increased, the monomer may not be absorbed by the seed particles, and the monomer may be uniquely suspension-polymerized in the aqueous medium, and particles other than the target particle size may be generated. The completion of monomer absorption can be determined by observing seed particles using an optical microscope and confirming the increase in particle size.

  From the viewpoint of suppressing generation of child particles and large particles, the mass ratio of the di (meth) acrylate compound represented by the formula (1), which is a monomer, is 20 to 300 times the mass of the seed particles. Preferably, 50 to 250 times is more preferable, and 70 to 200 times is more preferable. Here, the child particle means a particle having a particle size smaller than the main peak when the particle size distribution of the crosslinked polymer particle is measured.

  The monomer absorbed by the seed particles contains the di (meth) acrylate compound represented by the following formula (1), so that the crosslinked polymer particles can have excellent compression recovery characteristics while maintaining low elasticity. . The content of the di (meth) acrylate compound represented by the formula (1) is preferably 80 mol% or more, more preferably 85 mol% or more, and more preferably 90 mol% or more based on the total amount of monomers. Is more preferable.

式中、Ｒ^１及びＲ^２はそれぞれ独立に水素原子又はメチル基を示し、Ｌ^１は炭素数４〜１２のアルキレン基を示し、該アルキレン基は、直鎖状でも分岐状でも環状でもよい。

In the formula, R ¹ and R ² each independently represent a hydrogen atom or a methyl group, L ¹ represents an alkylene group having 4 to 12 carbon atoms, and the alkylene group may be linear, branched or cyclic.

  Examples of the di (meth) acrylate compound represented by the formula (1) include 1,3-butanediol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, and 1,5-pentanediol diester. (Meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,7-heptanediol di (meth) acrylate, 1,8-octanediol di (meth) acrylate, 3-methyl-1,5-pentane Examples include alkanediol di (meth) acrylates such as diol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 1,10-decanediol di (meth) acrylate, and neopentyl glycol di (meth) acrylate. It is done.

  As a monomer, other polyfunctional monomers and / or monofunctional monomers can be used in combination with the di (meth) acrylate compound represented by the formula (1).

  Examples of multifunctional monomers include divinyl compounds such as divinylbenzene, divinylbiphenyl, divinylnaphthalene; (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, and (poly) tetramethylene glycol. (Poly) alkylene glycol-based di (meth) acrylates such as di (meth) acrylate; trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, tetramethylolpropane tetra (meth) acrylate, pentaerythritol tri ( (Meth) trifunctional or higher (meth) such as (meth) acrylate, 1,1,1-trishydroxymethylethane tri (meth) acrylate, 1,1,1-trishydroxymethylpropane triacrylate Acrylate; ethoxylated bisphenol A di (meth) acrylate, propoxylated ethoxylated bisphenol A di (meth) acrylate, tricyclodecane dimethanol di (meth) acrylate, 1,1,1-trishydroxymethylethanedi (meta ) Acrylates, di (meth) acrylates such as ethoxylated cyclohexanedimethanol di (meth) acrylate; diallyl phthalate and isomers thereof; triallyl isocyanurate and derivatives thereof. Among these monomers, NK ester (A-TMPT-6P0, A-TMPT-3E0, A-TMM-3LMN, A-GLY series, A-9300, AD-TMP, AD-manufactured by Shin-Nakamura Chemical Co., Ltd. TMP-4CL, ATM-4E, A-DPH) and the like are commercially available. These polyfunctional monomers may be used alone or in combination of two or more.

  Examples of the monofunctional monomer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, o-ethylstyrene, m-ethylstyrene, p-ethylstyrene, 2,4- Dimethyl styrene, pn-butyl styrene, pt-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl Styrene such as styrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene or derivatives thereof; methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, acrylic acid Isobutyl, hexyl acrylate, 2-ethylhexyl acrylate, acrylic acid n-o Chill, dodecyl acrylate, lauryl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, methacryl (Meth) acrylic acid esters such as isobutyl acid, hexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, lauryl methacrylate, stearyl methacrylate; vinyl acetate, vinyl propionate, vinyl benzoate, Vinyl esters such as vinyl butyrate; N-vinyl compounds such as N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidone; vinyl fluoride, vinylidene fluoride, tetrafluoroe Ren, hexafluoropropylene, trifluoroethyl acrylate, fluorine-containing monomers such as acrylic acid tetrafluoropropyl; butadiene include conjugated dienes such as isoprene. These can be used alone or in combination of two or more.

  Examples of the aqueous medium include water or a mixed medium of water and a water-soluble solvent (for example, lower alcohol). The aqueous medium contains a surfactant. As the surfactant, any of anionic, cationic, nonionic and zwitterionic surfactants can be used.

  Examples of the anionic surfactant include fatty acid oils such as sodium oleate and castor oil potassium, alkyl sulfate salts such as sodium lauryl sulfate and ammonium lauryl sulfate, alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, and alkylnaphthalene sulfone. Acid salts, alkane sulfonates, dialkyl sulfosuccinates such as sodium dioctyl sulfosuccinate, alkenyl succinates (dipotassium salts), alkyl phosphate esters, naphthalene sulfonate formalin condensates, polyoxyethylene alkylphenyl ether sulfates Salt, polyoxyethylene alkyl ether sulfate such as sodium polyoxyethylene lauryl ether sulfate, and polyoxyethylene alkyl sulfate ester salts.

  Examples of the cationic surfactant include alkylamine salts such as laurylamine acetate and stearylamine acetate, and quaternary ammonium salts such as lauryltrimethylammonium chloride.

  Nonionic surfactants include, for example, hydrocarbon nonionic surfactants such as polyethylene glycol alkyl ethers, polyethylene glycol alkyl aryl ethers, polyethylene glycol esters, polyethylene glycol sorbitan esters, polyalkylene glycol alkylamines, or amides. Agents, polyether-modified silicon-based nonionic surfactants such as polyethylene oxide adducts of silicon and polypropylene oxide adducts, and fluorine-based nonionic surfactants such as perfluoroalkyl glycols.

  Examples of zwitterionic surfactants include hydrocarbon surfactants such as lauryl dimethylamine oxide, phosphate ester surfactants, and phosphite ester surfactants.

  One surfactant may be used alone, or two or more surfactants may be used in combination. Among the above surfactants, an anionic surfactant is preferable from the viewpoint of dispersion stability during polymerization of the monomer.

  Examples of the polymerization initiator to be added as needed include benzoyl peroxide, lauroyl peroxide, orthochlorobenzoyl peroxide, orthomethoxybenzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, and t-butyl peroxide. Organic peroxides such as oxy-2-ethylhexanoate and di-t-butyl peroxide; 2,2′-azobisisobutyronitrile, 1,1′-azobiscyclohexanecarbonitrile, 2,2 ′ -Azo compounds such as azobis (2,4-dimethylvaleronitrile). The polymerization initiator may be used in the range of 0.1 to 7.0 parts by mass with respect to 100 parts by mass of the monomer.

  Next, the polymer absorbed by the seed particles is used to obtain crosslinked polymer particles.

  The polymerization temperature can be appropriately selected according to the types of the monomer and the polymerization initiator. The polymerization temperature is preferably 25 to 110 ° C, more preferably 50 to 100 ° C. The polymerization reaction is preferably carried out at an elevated temperature after the seed particles are sufficiently swollen and the monomer and optionally the polymerization initiator are completely absorbed. After the seed polymerization is completed, the aqueous polymer is removed from the polymerization solution by centrifugation as necessary, washed with water and a solvent, and then dried to isolate the crosslinked polymer particles.

  In the polymerization step, a polymer dispersion stabilizer may be added in order to improve the dispersion stability of the seed particles.

  Examples of the polymer dispersion stabilizer include polyvinyl alcohol, polycarboxylic acid, celluloses (hydroxyethyl cellulose, carboxymethyl cellulose, etc.) and polyvinyl pyrrolidone, and an inorganic water-soluble polymer compound such as sodium tripolyphosphate is also used in combination. Can do. Of these, polyvinyl alcohol and polyvinyl pyrrolidone are preferable. The addition amount of the polymer dispersion stabilizer is preferably 1 to 10 parts by mass with respect to 100 parts by mass of the monomer.

  In order to suppress the generation of particles in which the monomer is emulsion-polymerized alone in water, water-soluble polymerization inhibitors such as nitrites, sulfites, hydroquinones, ascorbic acids, water-soluble vitamin Bs, citric acid, and polyphenols are used. It may be used.

From the viewpoint of further improving the compression recovery property in a heating environment, the ratio of double bonds remaining in the crosslinked polymer particles (double bond residual ratio) is 0 to 15 mol% or less based on the total amount of monomers that swell the seed particles. It is good to be. The residual rate of double bonds remaining in the crosslinked polymer particles is determined by measuring the infrared absorption spectrum of the powder of crosslinked polymer particles isolated from the prepared dispersion of crosslinked polymer particles, and determining the peak intensity around 815 cm ⁻¹ from the above monomer. It can be calculated by comparing with the intensity at the same peak.

  The average particle diameter of the crosslinked polymer particles is preferably 10 μm or less, more preferably 7 μm or less, and still more preferably 5 μm or less. The lower limit of the average particle size of the crosslinked polymer particles is preferably 1 μm or more, more preferably 1.75 μm or more, and further preferably 2 μm or more. If the average particle size is small, the crosslinked polymer particles may easily aggregate.

  The Cv value of the particle diameter (diameter) of the crosslinked polymer particles is preferably 15% or less. When the Cv value exceeds 15%, the performance of the crosslinked polymer particles in various uses tends to be lowered. For example, the connection reliability when the crosslinked polymer particles are used as conductive particles constituting an anisotropic conductive agent is reduced, or the quantitativeness when the crosslinked polymer particles are used in a biopsy element is reduced. There are things to do. From the same viewpoint, the Cv value of the particle diameter of the crosslinked polymer is more preferably 10% or less, still more preferably 5% or less, and still more preferably 4% or less.

The average particle diameter and the Cv value of the particle diameter of the crosslinked polymer particles can be determined by the following measurement method.
1) Disperse particles in water using an ultrasonic dispersion device to prepare a dispersion containing 1% by mass of particles.
2) Using a particle size distribution meter (Sysmex Flow, manufactured by Sysmex), observe an image of about 100,000 particles in the dispersion with a scanning electron microscope (SEM), and determine the average particle size and the Cv value of the particle size. calculate.

  The compression recovery rate representing the compression characteristics of the crosslinked polymer particles can be measured by the following method.

  The compression recovery rate is crosslinked by a smooth end face (50 μm × 50 μm) of a square column at a load load rate of 0.33 mN / sec at room temperature or heating (180 ° C.) using a micro compression tester (manufactured by Fisher). It is obtained by measuring the relationship between the load value and the compression displacement when the load is decreased at a speed of 0.33 mN / sec after the polymer particles are compressed from the center to 5 mN. The ratio (L1 / L2) of the displacement (L1) from the point of reversing the load to the final unloading value and the displacement (L2) from the point of reversal to the initial unloading value is expressed in% as a compression recovery rate. It is. In this embodiment, an average value measured five times is used. In this embodiment, “room temperature” is 25 ° C.

  The compression recovery rate at room temperature and 180 ° C. of the crosslinked polymer particles is preferably 40% or more, more preferably 50% or more, and further preferably 60% or more.

The compression recovery increase rate of the crosslinked polymer particles is calculated by the following formula (2). The compression recovery increase rate is −5% or more, preferably 0% or more, and more preferably 3% or more. The upper limit of the compression recovery increase rate of the crosslinked polymer particles is, for example, about 20%.
Compression recovery increase rate (%) = [(compression recovery rate at 180 ° C.) − (Compression recovery rate at room temperature)] / (compression recovery rate at room temperature) × 100 (2)

  The compression modulus and compressive fracture strength when the crosslinked polymer particles are compressed can be measured by the following methods.

  Using a micro compression tester (manufactured by Fisher), the cross-linked polymer particles are compressed to 50 mN with a smooth end face (50 μm × 50 μm) of a square column at a load rate of 1 mN / sec at room temperature or with heating (180 ° C.). Measure the load and compression displacement. From the measured values obtained, the compression modulus (30% K value) when the crosslinked polymer particles are 30% compressively deformed can be determined by the following formula. Further, the load at the point at which the displacement during the measurement changes most greatly is defined as the breaking strength (mN).

30% K value (kgf / mm ² = 9.81 × 10 ⁶ N / m ² ) = (3/2 ^1/2 ) · F · S ⁻³ / ² · R ^−1/2
F: Load (mN) when the crosslinked polymer particles are compressed and deformed by 30%
S: Compression displacement (mm) when the crosslinked polymer particles are 30% compressively deformed
R: radius of cross-linked polymer particles (mm)

The crosslinked polymer particles preferably have a compression modulus of 50 to 400 kgf / mm ² (4.90 × 10 ^{8 to} 3.92 × 10 ⁹ N / m ² ) when compressed and deformed by 30%, More preferably, it is 300 kgf / mm ² (9.81 × 10 ^{8 to} 2.94 × 10 ⁹ N / m ² ).

  If the 30% K value is too small, the flexibility of the crosslinked polymer particles becomes too high, and an anisotropic conductive material including a conductive particle having a conductive layer formed on the surface of the crosslinked polymer particle and a binder resin is used. When connecting the electrodes, it becomes difficult to sufficiently eliminate the binder resin between the conductive particles and the electrodes. If the 30% K value is too large, the flexibility of the crosslinked polymer particles may be too low, and the electrode may be damaged by the conductive particles.

The cross-linked polymer particles of the present embodiment described above, when the average particle diameter D and the compressive fracture strength B at 180 ° C. satisfy the relationship represented by the following formula (3), are produced using the cross-linked polymer particles. The conduction reliability of the conductive particles can be further improved. In Formula (3), the average particle diameter D is 2-10 micrometers. The compressive fracture strength B is not particularly limited, but is about 100 mN.
B (mN) ≧ [8.38998 × D (μm) −15.17 (mN)] (3)

[Conductive particles]
The electroconductive particle of this embodiment has the said crosslinked polymer particle and the metal film formed on the surface of this crosslinked polymer particle. FIG. 1 is a schematic cross-sectional view showing conductive particles according to this embodiment. As shown in FIG. 1, the conductive particle 10 includes a crosslinked polymer particle 1 and a metal coating (metal layer) 2 that covers the surface of the crosslinked polymer particle 1.

  Although the metal which comprises the metal layer 2 is not specifically limited, For example, gold, silver, copper, platinum, zinc, iron, lead, tin, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, germanium, Cadmium, tin-lead alloy, tin-copper alloy, tin-silver alloy, and tin-lead-silver alloy. Especially, it is preferable that the metal layer 2 contains nickel, copper, gold | metal | money, or a tin-silver alloy.

  The method for forming the metal layer 2 on the surface of the crosslinked polymer particle 1 is not particularly limited. Examples of the method for forming the metal layer 2 include an electroless plating method, an electroplating method, a physical vapor deposition method, and a method of applying a paste containing metal powder to the surface of the crosslinked polymer particle 1. As physical vapor deposition, vacuum vapor deposition, ion plating, or ion sputtering can be used. As a method for forming the metal layer 2, an electroless plating method is preferable.

  The metal layer 2 may be a single layer or a plurality of metal layers in which two or more layers are laminated. From the viewpoint of reducing the connection resistance between the electrodes, the surface of the conductive particles 10 (the outermost layer of the metal layer 2) is preferably a gold layer, a palladium layer, or a tin-silver alloy layer.

  The thickness of the metal layer 2 is preferably 0.02 to 1 μm, and more preferably 0.02 to 0.5 μm. If the thickness of the metal layer 2 is 0.02 μm or more, good conductivity is easily developed, and if it is 1 μm or less, the conductive particles are easily deformed during connection. The thickness of the metal layer 2 can be calculated | required by observing the cross section of electroconductive particle, for example using a transmission electron microscope (TEM).

  The average particle size of the conductive particles 10 is preferably 1.02 to 11 μm, more preferably 1.5 to 10 μm, still more preferably 2 to 7 μm, and even more preferably 2.5 to 5 μm.

  The CV value of the particle size of the conductive particles 10 is preferably 10% or less, more preferably 7% or less, and still more preferably 5% or less. When the CV value of the conductive particles 10 is 10% or less, the electrical connection reliability can be further increased.

  The average particle diameter and the CV value of the particle diameter of the conductive particles 10 can be measured by the same method as that for the crosslinked polymer particles 1.

[Anisotropic conductive material]
The anisotropic conductive material of the present embodiment includes the conductive particles and a binder resin. FIG. 2 is a schematic cross-sectional view showing the anisotropic conductive material according to the present embodiment. The anisotropic conductive material 40 includes an insulating binder resin 20 and conductive particles 10 dispersed in the binder resin 20.

  As the binder resin 20, a thermosetting resin composition containing a thermosetting resin, a curing agent, a film-forming polymer, or the like can be used.

  Although it does not specifically limit as a thermosetting resin, It is preferable to use an epoxy resin from a heat resistant viewpoint. As the epoxy resin, various epoxy compounds having two or more glycidyl groups in the molecule can be used. For example, bisphenol type epoxy resin, novolac type epoxy resin, naphthalene type epoxy resin, biphenyl type epoxy resin, alicyclic ring Formula type epoxy resins, glycidyl amine compounds, glycidyl ether compounds, and glycidyl ester compounds may be mentioned.

When a high-purity product in which impurity ions (Na ⁺ , Cl ^−, etc.), hydrolyzable chlorine, etc. are reduced to 300 ppm or less is used as the epoxy resin, it becomes easy to prevent electromigration.

  Although it does not specifically limit as a hardening | curing agent, A latent hardening | curing agent can be used. Examples of the latent curing agent include imidazole compounds, hydrazide compounds, boron trifluoride-amine complexes, sulfonium salts, amine imides, polyamine salts, and dicyandiamide.

  The film-forming polymer is not particularly limited as long as the anisotropic conductive material can be formed into a film shape. Examples of the film-forming polymer include thermoplastic resins such as phenoxy resin, polyester resin, and polyamide resin.

  The binder resin 20 can be mixed with butadiene rubber, acrylic rubber, styrene-butadiene rubber, silicone rubber, or the like in order to reduce stress after adhesion or to improve adhesion.

  The binder resin 20 can also contain an inorganic filler. As the inorganic filler, for example, a filler made of silica, magnesia, bentonite, smectite, alumina, or boron nitride can be used.

  The binder resin 20 may be a photocurable resin composition containing a photopolymerization initiator such as a radical polymerizable resin and an organic peroxide instead of the thermosetting resin and the curing agent.

  The anisotropic conductive material 40 can be manufactured as follows, for example. First, a binder resin 20 is prepared by dissolving or dispersing a thermosetting resin composition containing an epoxy resin, an acrylic rubber, a latent curing agent, and a film-forming polymer in an organic solvent as necessary. Subsequently, the liquid anisotropic conductive material 40 is produced by dispersing the conductive particles 10 in the binder resin 20. The organic solvent is preferably one that can dissolve the resin component and has a boiling point of 50 to 150 ° C. at normal pressure.

  The liquid anisotropic conductive material 40 can be used as it is for connecting circuit members, but can be used after being formed into a film. The film-like anisotropic conductive material 40 is peeled from the release film after the liquid anisotropic conductive material 40 is applied onto the release film, the organic solvent is removed below the activation temperature of the curing agent. Can be produced. As the releasable film, a resin film such as a fluororesin film, a polyethylene terephthalate film, and a polyolefin film is preferably used. When the anisotropic conductive material 40 is used in the form of a film, it is convenient from the viewpoint of handleability.

  The thickness of the film-like anisotropic conductive material 40 is relatively determined in consideration of the particle size of the conductive particles 10 and the characteristics of the anisotropic conductive material 40, and is preferably 1 to 100 μm. It is more preferable that it is 3-50 micrometers. If the thickness of the anisotropic conductive material 40 is less than 1 μm, it is difficult to obtain sufficient adhesion, and if it exceeds 100 μm, a large amount of the conductive particles 10 is required to obtain conductivity, which is not realistic.

[Connection structure]
The circuit member connection structure according to the present embodiment includes a first circuit member in which a first circuit electrode is formed on the main surface of the first circuit board, and a first circuit member on the main surface of the second circuit board. A second circuit member on which two circuit electrodes are formed, and a connection portion interposed between the first circuit member and the second circuit member. The second circuit member is disposed so that the second circuit electrode faces the first circuit electrode, and the connection portion includes the conductive particles according to the present embodiment.

  FIG. 3 is a schematic cross-sectional view showing a method for producing a circuit member connection structure using the anisotropic conductive material according to the present embodiment.

  First, as shown in FIG. 3A, a first circuit board 4 on which a first circuit electrode 5 is formed and a second circuit board 6 on which a second circuit electrode 7 is formed are prepared. Then, the anisotropic conductive material 40 is disposed therebetween. At this time, the position is adjusted so that the first circuit electrode 5 and the second circuit electrode 7 face each other. After that, the first circuit board 4 and the second circuit board 6 are laminated while being pressurized and heated in the direction in which the first circuit electrode 5 and the second circuit electrode 7 face each other, as shown in FIG. A conductive connection structure 42 shown in b) is obtained. The connection structure 42 is electrically connected by a cured product of the anisotropic conductive material 40.

  Examples of the first circuit board 4 and the second circuit board 6 include a glass substrate, a tape substrate such as polyimide, a bare chip such as a driver IC, and a rigid package substrate.

  Since the crosslinked polymer particles according to the present embodiment have low elasticity and excellent compression recovery in a heating environment and have high fracture strength, stable connection when used as resin particles constituting conductive particles. Reliability can be demonstrated. The crosslinked polymer particles according to the present embodiment are useful not only in the field of electronic materials but also in a wide range of fields such as paints, coating agents, light diffusing agents, cosmetics, pharmaceuticals or biopsy elements, agricultural chemicals, building materials, and the like. .

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

<Synthesis of seed particles>
Synthesis example 1
A 500 mL three-necked flask is charged with 70 g of methyl methacrylate (MMA), 2.1 g of octanethiol (OCT), 0.7 g of potassium peroxodisulfate (KPS) and 400 g of water, and heated in a 70 ° C. water bath. Then, stirring was performed for about 8 hours using a stirrer to form seed particles.

Synthesis example 2
Seed particles were formed in the same manner as in Synthesis Example 1 except that 30 g of styrene (ST), 3 g of octanethiol (OCT), 0.5 g of potassium peroxodisulfate (KPS) and 400 g of water were used.

Synthesis example 3
Seed particles were formed in the same manner as in Synthesis Example 1 except that butyl acrylate (BA) was used instead of MMA.

Synthesis example 4
Seed particles were formed in the same manner as in Synthesis Example 1 except that hexyl acrylate (HA) was used instead of MMA.

Synthesis example 5
Seed particles were formed in the same manner as in Synthesis Example 1 except that the amount of OCT was changed to 1.4 g.

Synthesis Example 6
Seed particles were formed in the same manner as in Synthesis Example 1 except that the amount of OCT was changed to 0.7 g.

  The particle size of the seed particles obtained in each synthesis example was measured with a microtrack, and the average particle size was calculated. Further, the molecular weight of the obtained seed particles was measured using GPC. The results are shown in Table 1.

(Dispersibility evaluation after centrifugation)
Centrifugation of the aqueous solution of the seed particles obtained in each synthesis example was performed, the supernatant was removed, ion-exchanged water for the removed supernatant was added, and then redispersed. After performing the above operation twice, the particle size of the seed particles after centrifugation was measured by the microtrack method. The dispersibility of the particles was evaluated as “A” when the particle size change before and after centrifugation was less than 20 nm, “B” when 20 to 50 nm, and “C” when exceeding 50 nm.

[Production of crosslinked polymer particles]
Example 1
A monomer in which 4 g of benzoyl peroxide is dissolved in 400 g of butanediol diacrylate (BDDA) is mixed with 6800 g of ion-exchanged water in which 20.4 g of triethanol dodecyl sulfate is dissolved, and the mixture is treated with an ultrasonic homogenizer for 10 minutes to prepare an emulsion. did.

  To this emulsion, 300 g of the seed particle dispersion of Synthesis Example 1 (solid content 2.52 g) was added and stirred at room temperature for 12 hours, and then polyvinyl alcohol (Nippon Synthetic Chemical Co., Ltd., trade name “GH-17”) 6 1000 g of an aqueous solution containing mass% was added and polymerization was carried out at 80 ° C. for 8 hours to synthesize crosslinked polymer particles.

(Example 2)
Crosslinked polymer particles were synthesized in the same manner as in Example 1 except that the polymerization was performed at 80 ° C. for 8 hours.

(Example 3)
Crosslinked polymer particles were synthesized in the same manner as in Example 1 except that the polymerization was performed at 75 ° C. for 8 hours.

(Example 4)
Crosslinked polymer particles were synthesized in the same manner as in Example 1 except that the polymerization was performed at 70 ° C. for 8 hours.

(Example 5)
Crosslinked polymer particles were synthesized in the same manner as in Example 1 except that hexanediol diacrylate (HDDA) was used instead of BDDA.

(Example 6)
Crosslinked polymer particles were synthesized in the same manner as in Example 1 except that methylpentanediol diacrylate (MPDA) was used instead of BDDA.

(Example 7)
Crosslinked polymer particles were synthesized in the same manner as in Example 1 except that nonanediol diacrylate (NDDA) was used instead of BDDA.

(Example 8)
Crosslinked polymer particles were synthesized in the same manner as in Example 1 except that decanediol diacrylate (DDDA) was used instead of BDDA.

Example 9
Instead of the seed particle dispersion of Synthesis Example 1, crosslinked polymer particles were synthesized in the same manner as in Example 1 except that 300 g of the seed particle dispersion of Synthesis Example 5 (solid content 1.69 g) was used.

(Example 10)
Crosslinked polymer particles were synthesized in the same manner as in Example 1 except that 300 g of the seed particle dispersion of Synthesis Example 6 (solid content 1.78 g) was used instead of the seed particle dispersion of Synthesis Example 1.

(Example 11)
Instead of the seed particle dispersion of Synthesis Example 1, crosslinked polymer particles were synthesized in the same manner as in Example 1 except that 300 g of the seed particle dispersion of Synthesis Example 8 (solid content 1.34 g) was used.

(Example 12)
Crosslinked polymer particles were synthesized in the same manner as in Example 1 except that the seed particle dispersion of Synthesis Example 1 was changed to 300 g (solid content: 4 g).

(Example 13)
Crosslinked polymer particles were synthesized in the same manner as in Example 1 except that the seed particle dispersion of Synthesis Example 1 was changed to 300 g (solid content: 5.714 g).

(Comparative Example 1)
Instead of the seed particle dispersion of Synthesis Example 1, crosslinked polymer particles were synthesized in the same manner as Example 1 except that 300 g of the seed particle dispersion of Synthesis Example 2 (solid content 2.46 g) was used.

(Comparative Example 2)
Crosslinking was carried out in the same manner as in Comparative Example 1 except that 200 g of polytetramethylene glycol diacrylate (manufactured by Hitachi Chemical Co., Ltd., trade name “FA-PTG9A”) and 200 g of divinylbenzene (DBV, purity 96%) were used instead of BDDA. Polymer particles were synthesized.

(Comparative Example 3)
Crosslinked polymer particles were synthesized in the same manner as in Example 1 except that 400 g of glycerin propoxytriacrylate (manufactured by Daicel Cytec Co., Ltd., trade name “OTA480”) was used instead of BDDA.

  The seed particles of Synthesis Examples 3 and 4 could not be used for the synthesis of crosslinked polymer particles because of poor dispersibility.

The particle diameters of the crosslinked polymer particles obtained in each Example and Comparative Example were measured with a flow-type particle diameter measuring apparatus, and the average particle diameter and the Cv value of the particle diameter were calculated. The large particle content was calculated as a large particle having a particle size of 1 μm or more from the mode diameter (maximum value of particle size distribution). Furthermore, the double bond residual ratio in the crosslinked polymer particles was calculated by measuring an infrared absorption spectrum. Specifically, the obtained dispersion of the crosslinked polymer particles was repeatedly washed with water three times by centrifugation and then dried, and then the infrared absorption spectrum of the powder of the crosslinked polymer particles obtained was dried by an infrared spectrophotometer. (Made by HRIBA) was measured, and the double bond residual ratio was calculated by comparing the peak intensity around 815 cm ⁻¹ of the powder with the peak intensity of the monomer before polymerization. The results are shown in Tables 2 and 3. In the table, the swelling ratio is the mass ratio of the monomer used for seed polymerization to the mass of the seed particles.

  Moreover, the compression recovery rate at room temperature and 180 ° C, and the compression at 180 ° C are measured by measuring the load and compression displacement when the crosslinked polymer particles are compressed using a micro compression tester (Fisher) under the above-mentioned conditions. The breaking strength and 30% K value were calculated. The compression recovery increase rate was calculated from the compression recovery rate at room temperature and the compression recovery rate at 180 ° C. The results are shown in Tables 2 and 3.

  From Table 2, it can be confirmed that the crosslinked polymer particles of Examples 1 to 9 satisfy the relationship of the formula (2) between the average particle diameter and the compressive fracture strength at 180 ° C.

[Preparation of conductive particles]
A nickel layer having a thickness of 0.2 μm was formed on each of the crosslinked polymer particle surfaces obtained in Examples 1 and 5 to 8 and Comparative Examples 1 to 3 by an electroless plating method. A 04 μm palladium layer was formed to prepare conductive particles 1 to 8, respectively.

[Production of anisotropic conductive material]
An anisotropic conductive material was produced using the conductive particles.

  5 parts by mass of phenoxy resin (trade name “PKHC” manufactured by Union Carbide), acrylic rubber (copolymer of butyl acrylate, ethyl acrylate, acrylonitrile and glycidyl methacrylate, copolymerization ratio (mass) 40/30/30/3, Mw 850,000) 18 parts by mass, epoxy resin (trade name “YL-983U” manufactured by Japan Epoxy Resin Co., Ltd.) 15 parts by mass in a solution of 10 parts by mass of ethyl acetate, a cationic curing agent (Sanshin Chemical Industry Co., Ltd.) 2 parts by mass of a product name “SI-60”) was added to prepare a thermosetting resin composition. Next, after adding 30 parts by mass of an ethyl acetate dispersion of 10 parts by mass of a silica filler (trade name “Aerosil R805”, manufactured by Nippon Aerosil Co., Ltd.) to the thermosetting resin composition, 20 parts by mass of conductive particles and Ultrasonic dispersion was performed by adding 10 parts by mass of ethyl acetate to prepare a liquid anisotropic conductive material.

  A liquid anisotropic conductive material is applied onto a silicone-treated polyethylene terephthalate film (thickness 40 μm, hereinafter referred to as “PET film”) with a roll coater and dried at 80 ° C. for 5 minutes to form a film having a thickness of 23 μm. An anisotropic conductive material was prepared.

[Production of connection structure]
Using the produced film-like anisotropic conductive material, a chip (1.7 mm × 17 mm, thickness: 0.5 mm) with gold bumps (area: 30 μm × 90 μm, space 10 μm, height: 15 μm, number of bumps: 362) ) And a glass substrate with an ITO circuit (Geomatec, thickness: 0.7 mm) were connected as follows to produce a connection structure.

The surface opposite to the surface on which the PET film of the film-like anisotropic conductive material cut into a predetermined size (2 mm × 19 mm) is provided on the surface on which the ITO circuit of the glass substrate with the ITO circuit is formed, ^{80 ℃, 0.98MPa (10kgf / cm} 2), was affixed by five seconds and. Then, the PET film is peeled off, and the gold bumps of the chip and the glass substrate with the ITO circuit are aligned through an anisotropic conductive material, and heated and pressed under conditions of 170 ° C., 70 MPa for 5 seconds. This connection was made to obtain a mounting sample (connection structure).

(Conduction resistance test)
The conduction resistance test of the produced mounting sample (connection structure) was performed as follows. The evaluation results are summarized in Table 4.

  Regarding the conduction resistance between the chip electrode / glass electrode of each mounting sample, an average value was obtained when 14 locations were measured. In addition, the conduction resistance measured the initial value and the value after the reliability test (moisture absorption heat test) left to stand for 500 hours on conditions of temperature 85 degreeC and humidity 85%. It is important that the anisotropic conductive material has a high insulation resistance between the chip electrodes and a low conduction resistance between the chip electrode and the glass electrode. The case where the conduction resistance after the reliability test is less than 5Ω is “A”, the case where it is 5 to 10Ω is “B”, and the case where it exceeds 10Ω is “C”.

(Confirmation of indentation)
Using an Olympus BH3-MJL liquid crystal panel inspection microscope, the state of indentation was observed from the glass substrate side by Nomarski differential interference observation. The case where the outline could be clearly confirmed was good, and the others were unclear.

  It was confirmed that the crosslinked polymer particles having the configuration of the present invention have a high fracture strength and an excellent compression recovery property in a heating environment while having a low elasticity. Moreover, it was confirmed that the connection structure of the circuit member which is excellent in electroconductive reliability can be produced by using the electroconductive particle formed using this crosslinked polymer particle.

  According to the present invention, it is possible to provide crosslinked polymer particles that are low in elasticity but excellent in compression recovery under a heating environment and have high breaking strength. Moreover, according to this invention, the connection structure of the electroconductive particle produced from this crosslinked polymer particle, the anisotropic conductive material containing this electroconductive particle, and a circuit member can be provided.

  DESCRIPTION OF SYMBOLS 1 ... Crosslinked polymer particle, 2 ... Metal layer, 4 ... 1st circuit board, 5 ... 1st circuit electrode, 6 ... 2nd circuit board, 7 ... 2nd circuit electrode, 10 ... Conductive particle, 20 ... Binder resin, 40 ... Anisotropic conductive material, 42 ... Conductive connection structure.

Claims (9)

After swelling the seed particles containing polymethyl methacrylate in an emulsion containing a monomer containing a di (meth) acrylate compound represented by the following formula (1), the monomer is obtained by seed polymerization. Crosslinked polymer particles,
Crosslinked polymer particles having a compression recovery increase rate represented by the following formula (2) of -5% or more.

[In Formula (1), R ¹ and R ² each independently represent a hydrogen atom or a methyl group, and L ¹ represents an alkylene group having 4 to 12 carbon atoms. ]
Compression recovery increase rate (%) = [(compression recovery rate at 180 ° C.) − (Compression recovery rate at room temperature)] / (compression recovery rate at room temperature) × 100 (2)   The crosslinked polymer particles according to claim 1, wherein the seed particles have a weight average molecular weight of 3000 to 50000.   The crosslinked polymer particle according to claim 1 or 2, wherein the ratio of the remaining double bond is 0 to 15 mol%.   The crosslinked polymer particle according to any one of claims 1 to 3, wherein a mass ratio of the di (meth) acrylate compound represented by the formula (1) to a mass of the seed particle is 20 to 300 times.   The crosslinked polymer particle according to any one of claims 1 to 4, wherein a compression recovery rate at 180 ° C is 40% or more.   The crosslinked polymer particle according to any one of claims 1 to 5, wherein the average particle size is 1 to 10 µm, and the Cv value of the particle size is 15% or less.   The electroconductive particle which has the crosslinked polymer particle as described in any one of Claims 1-6, and the metal film formed in the surface of this crosslinked polymer particle.   An anisotropic conductive material comprising the conductive particles according to claim 7 and a binder resin. A first circuit member having a first circuit electrode formed on the main surface of the first circuit board;
A second circuit member in which a second circuit electrode is formed on a main surface of the second circuit board, and the second circuit electrode is disposed so as to face the first circuit electrode;
A connecting portion interposed between the first circuit member and the second circuit member;
With
A connection structure for a circuit member, wherein the connection portion includes the conductive particles according to claim 7.

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