JP4902853B2 - Resin fine particles and conductive fine particles - Google Patents

Description

  The present invention relates to conductive fine particles that can be used in anisotropic conductive adhesives for mounting microelements, and particularly to resin fine particles as a base material thereof.

  An anisotropic conductive adhesive is a conductive fine particle in which conductive fine particles are monodispersed in a base adhesive resin and sandwiched between electrode terminals and pressed in the thickness direction. Realizes an electrical connection between the terminals. That is, the anisotropic conductive adhesive performs physical connection between the terminal surfaces and at the same time makes electrical connection between corresponding terminals.

  Anisotropic conductive adhesive is generally supplied in the form of a film or paste, that is, as an anisotropic conductive film (ACF), anisotropic conductive paste (ACP), or anisotropic conductive ink (ACI), etc. Has been. A thermosetting resin such as an epoxy resin is used as the base adhesive.

  Anisotropic conductive adhesive is used in flat display devices such as liquid crystal display devices (LCD) and plasma display devices (PDP) and drive circuit boards. Used for mounting IC chips on panel surfaces or substrate surfaces. Using anisotropic conductive adhesive, surface mounting (COG; Chip On Glass) on the panel surface of IC chip, surface mounting (COB; Chip On Board, COF; Chip On Flexibleboard) on the substrate surface, and semiconductor Surface mount packages and the like are realized. For example, when used for connection between a liquid crystal display panel body and a flexible connection substrate (FPC) or TCP (also called Tape Carrier Package: TAB), the terminal portion of the flexible substrate is made of a tape-like anisotropic conductive adhesive. To the terminal portion around the panel body. At the time of this pasting, precise positioning is performed so that the corresponding terminals are connected to each other, and heating and pressure bonding are performed over the entire place where the conductive adhesive is disposed.

  Spherical particles made of only metal are used as conductive fine particles for anisotropic conductive adhesives, but resin fine particles coated with a metal layer are widely used for connection between fine terminals. . The resin fine particles coated with the metal layer are generally crimped at a temperature of about 15 to 20 kgf (converted as about 147.10 to 196.133 N, 1 kgf = about 9.80665 N) / cm2 at a high temperature of 150 ° C. or higher. . The fine particles sandwiched between the electrode terminals under pressure and pressed in the thickness direction must be appropriately deformed and always in contact with the terminals in as wide an area as possible. Connection with reduced resistance value and improved conduction reliability is possible.

Conductive fine particles that define the load required to strain 40% in the compression test (see, for example, Patent Document 1), and conductive fine particles that define the K value when deformed by 10% (for example, patents) Reference 2) is known.
JP 2001-216840 Japanese Patent Laid-Open No. 2001-216841

  However, according to the research of the present inventor, the conventional resin fine particles are too hard to obtain a sufficient connection area, scratch the electrodes, or are simply soft, so that the initial connection area can be obtained. However, there is no elastic deformation that can follow changes in the connection part (expansion and shrinkage due to temperature, etc.) caused by changes in the external environment, and the conduction state between the two electrodes gradually increases and breaks, such as disconnection. I found it unstable.

  Further, the load and K value required for the 40% strain described above define the strength of the initial particles, and are for making a product. It cannot be used as a guideline for maintaining reliability when it is incorporated as a product and continues to be used.

  In view of the above, the present invention obtains a new type of resin fine particles, covers the resin fine particles with a conductive layer, and obtains conductive fine particles that have moderate flexibility and can maintain stable conduction in micro device mounting. An object of the present invention is to provide an anisotropic conductive adhesive using the same.

Resin fine particles for conductive fine particles disposed between two electrodes,
The resin fine particles are obtained by copolymerizing a monofunctional monomer and a bifunctional monomer. In the load unloading test, 0.145 gf / sec × 9.80665 N / 1000 gf (N / sec) (about 1.42196) mN / sec), the fine particles are compressed at a load rate of the following formula (1):
P = 7/96 × d2 × 9.80665 (N) / 1000 (gf) (1)
[Wherein d is the number average particle diameter (μm) of the fine particles, and P (N) (gf × 9.80665N / 1000 gf) is a value obtained by rounding off the second decimal place. ]
50% or more, preferably 50% or more and 80% or less compression ratio when the load value P (N) represented by the following formula is satisfied, and the ratio of the compression ratio when the fine particles are repeatedly compressed 20 times first compression ratio of 80% or higher, preferably Ri der 100% or less than 80% by using a resin fine particles having the following Cv value of 10% can solve the above problems in the conductive fine particles The present invention has been reached.

  According to the present invention, the resin fine particles are appropriately deformed even when compressed, and recover moderately when the pressure is removed. For this reason, in the conductive fine particles based on this, when the conductive fine particles are placed between two electrodes and pressed, even if the distance between the electrodes and the applied pressure fluctuate due to changes in ambient temperature, etc. Since the conductive particles follow and sufficiently deform, stable conduction between the two electrodes can be maintained.

  The present invention is described in detail below.

  The present invention aims to maintain stable continuity in micro-element mounting, and for conductive fine particles, to provide appropriate flexibility while sufficiently securing the connection area, and to change the connection portion caused by environmental changes. By enabling elastic deformation that can follow, it was realized without damaging the electrode.

In the load unloading test, the resin fine particles are compressed at a load load speed of 0.145 gf / sec, and the following formula (1):
P = 7/96 * d2 (1)
[In the formula, * is a multiplication symbol (×), d is the particle size (μm) of fine particles, and P (gf) is a value obtained by rounding off the second decimal place. ]
The compression ratio when the load value P (gf) represented by is reached is 50% or more, and the ratio of the compression ratio when the same particle is repeatedly compressed 20 times is 80% or more of the first compression ratio It is. The physical properties of the resin fine particles described above are maintained even when the surface of the resin fine particles is coated with a normal conductive layer to form conductive fine particles.

  In a preferred example, the resin fine particles, preferably the conductive fine particles fall within the range of the number average particle diameter of 1 to 10 μm. Here, the number average particle diameter is a particle diameter in which the ratio of the number of particles having a smaller particle diameter is equal to the number of particles having a larger particle diameter than the average particle diameter obtained. In the particle distribution, the deviation coefficient, that is, the Cv value is 10% or less.

  The fine resin particles can be coated with a conductive layer by known means to obtain conductive fine particles. By using these conductive fine particles, sufficient contact area and conductivity can be obtained at the time of pressure curing, without damaging the electrodes, and stable and reliable continuity even with changes in the external environment. It is done. Such conductive fine particles are provided as a conductive adhesive, an anisotropic conductive adhesive, or the like.

  The test method for resin fine particles, particularly the load unloading test method, is shown below.

  For example, resin fine particles are dispersed on a steel plate having a smooth surface, and this is placed on a sample stage of a micro compression tester (manufactured by Shimadzu Corporation, MCTM-200), and one particle having an appropriate particle size is observed with a microscope. Select. Next, at a room temperature of 20 ° C., the diameter of the diamond made under the condition that the load value (also referred to as load application speed) 0.145 gf / sec and the load value (also referred to as maximum test load) P (gf) is reached. The resin fine particles are compressed on the smooth end surface of a 50 μm cylinder, and when the load value reaches P (gf), the load is removed at the same speed.

  Here, the load value P (gf) is a value obtained by the following equation (1).

P = 7/96 * d2 (1)
[Wherein, d is the particle diameter of the fine particles, preferably the number average particle diameter (μm), and P is a value obtained by rounding off the second decimal place. ]
The origin load value used in this test is 0 (gf). By repeating this unloading test 20 times and measuring the initial compression rate and the 20th compression rate, the following conditions are obtained.

  Resin fine particles have a compression rate of 50% or more when the load value reaches P (gf) by compressing at a load load rate of 0.145 gf / sec in the load unloading test, and the same particles are repeated 20 times. The ratio of the compression ratio when compressed is 80% or more of the first compression ratio.

  For the connection between the electrode terminals, the connection is usually performed under the condition that a high pressure bonding force (usually 15 to 20 kg / cm 2) is applied between the electrode terminals. In general, a temperature of 150 ° C. or higher is applied during pressure bonding. However, if the crimping force is too strong under such temperature conditions, the conventional metal plating resin particles may be plastically deformed or broken between the electrode terminals with a narrow gap, and a restoring force is generated. Otherwise, connection failure may occur. Of course, if the crimping force is too weak, the binder resin concentrates and flows out between the electrode terminals with a wide gap, and the binder resin between the metal plating resin particles and the electrode terminals is not excluded, resulting in poor connection. There is a risk.

The conductive fine particles need to have a sufficient contact area with the upper and lower terminals in order to obtain conduction performance, and are usually used in a compressed state of 40% (preferably 50%) or more. The relationship between the load value P (gf) and the particle size for obtaining an appropriate deformation for this purpose was obtained empirically. That is, in the load unloading test, it is compressed at a load load speed of 0.145 gf / sec, and the following formula (1):
P = 7/96 * d2 (1)
[Wherein d is the particle diameter (μm) of the fine particles, and P (gf) is a value obtained by rounding off the second decimal place. ]
When the load value represented by P reaches P (gf), the compression ratio needs to be 50% or more.

  Also, in order to reduce the connection resistance value and improve the conductivity reliability, the substrate fine particles are resin fine particles and have an appropriate flexibility and elastically deform as conductive fine particles when the electrodes are crimped. Things are necessary and the particles are less likely to break. When the conductive fine particles are hard, if the compressibility at a constant load is less than 50%, the electrode terminals are not easily deformed by the applied pressure, and as a result, a sufficient contact area with the terminals can be obtained. The connection resistance value may increase. Moreover, since it was hard, there was a possibility that the electrode might be destroyed by the pressure during pressure bonding. This initial compression rate is generally 90% or less, and a certain amount of compression is necessary. Moreover, since it is too hard at less than 50%, it is difficult to function as conductive fine particles such as anisotropic conductive adhesive. Therefore, it is preferably 50% or more and 90% or less, more preferably 55% or more and 70% or less.

  Further, the resin fine particles have a compression ratio of 50% or more when the load value reaches P (gf), and at the same time, the ratio of the compression ratio when repeatedly compressed is 80% or more of the first compression ratio. As a ratio (%) of the compression rate when the same particles are repeatedly compressed 20 times with respect to the compression rate of the first time (%), for example, when the first compression rate is 50% and the same particles are repeatedly compressed 20 times When the convergence value of the compression ratio is 40%, it is calculated as follows.

  The compression ratio when the same particles are repeatedly compressed 20 times (%) with respect to the compression ratio of the first time (%) = Convergence value of the compression ratio when the same particles are repeatedly compressed 20 times / 1 compression ratio × 100 = 40/50 × 100 = 80 (%).

  The initial compression ratio is determined by measuring the predetermined particle diameter d with an optical microscope attached to a micro compression tester and applying the load value P (gf) to one of these particles. Divided by the diameter d and multiplied by 100% can be obtained. Next, the compression ratio for the second and subsequent times is defined as the initial particle diameter d, and the amount of deformation of the particle diameter for the number of tests when the load value P (gf) is applied to the same initially compressed particle It can be obtained by dividing by the particle diameter d and multiplying by 100%.

  In the load unloading test, constant load compression is performed, the particles are distorted, and the recoverability when unloading is examined. When this is repeated, most of the plastically deformed portion of the deformation generated by the first constant load compression cannot be instantaneously recovered, and only the elastically deformed portion recovers. The plastic deformation part that cannot be recovered instantaneously remains after the second time, but the ratio decreases greatly, approaches the elastic deformation part (change process), and converges to a constant value at the 20th time (after the 10th time). Also, at this time, those having a low elastic modulus and unable to follow the deformation will be crushed. In order to stabilize the measured value, the interval between the compression test and the next compression test is preferably between 5 seconds and 10 seconds.

  As described above, the change rate of the compression rate is 80% or more of the first compression rate, but is generally 80% or more and 100% or less, preferably 80% or more and 90% or less.

  The resin fine particles or the conductive fine particles are elastic bodies that satisfy the above-described conditions, and even when compressed, the resin fine particles or the conductive fine particles are appropriately deformed, and are appropriately recovered when the pressure is removed. For this reason, when this conductive fine particle is placed between two electrodes and pressurized, the conductive particle follows and deforms even if there are fluctuations in the electrode spacing and pressure due to changes in ambient temperature, etc. Stable conduction can be maintained between the two electrodes.

  The conductive fine particles are generally spherical, have a particle diameter in the range of 1 μm to 10 μm, and have a coefficient of variation (Cv value) of 10% or less. Here, as the average particle diameter (μm) and the deviation coefficient, that is, the Cv value (= standard deviation / average particle diameter * 100, unit%), values obtained by observing 300 fine particles can be used. .

  In recent years, the pitch of electrodes has increased, and the gap between the electrodes tends to become even narrower. For this reason, if the particle diameter of the conductive fine particles is too large with respect to the gap between the electrodes, connection within the same electrode is likely to occur, thereby causing a leak phenomenon and failure. Therefore, the particle diameter of the conductive fine particles is in the range of 1 to 10 μm, more preferably 1 to 5 μm, and particularly preferably 2 to 4 μm. In recent years, the tendency to make fine particles of 4 μm or less is even stronger.

  Next, the Cv value as the conductive fine particles is 10% or less, preferably 6% or less, particularly preferably 2 to 5%. When the Cv value of the conductive fine particles exceeds 10%, the contact area between the obtained conductive fine particles and the electrode is likely to vary, and the gap between the electrodes is likely to be dominated by the particles having a large particle diameter. The absolute number of particles not involved in the increase. On the other hand, if the conductive fine particles have a Cv value of 10% or less, the number of particles involved in conduction can be increased, and conduction resistance can be reduced. In addition, since the connection between the two electrodes can be ensured with a large number of particles, the connection reliability can be increased.

  The method for obtaining the resin fine particles is not particularly limited, and examples thereof include a method using a polymerization method such as emulsion polymerization, suspension polymerization, seed polymerization, dispersion polymerization, and dispersion seed polymerization.

  The type of resin fine particles is not particularly limited as long as the above-mentioned various conditions are satisfied. For example, olefinic resins such as polyethylene, polypropylene, polyisobutylene; styrene resins such as polystyrene; polyvinyl chloride, poly Vinyl chloride resins such as vinylidene chloride; Acrylic resins such as polymethyl (meth) acrylate; Conjugated diene resins such as polybutadiene and polyisoprene; Condensation systems such as phenol formaldehyde resin, melamine formaldehyde resin, benzoguanamine formaldehyde resin, urea formaldehyde resin Resin; Resin fine particles composed of polyalkylene terephthalate, polysulfone, polycarbonate, polyamide, etc. are mentioned. Among them, resin fine particles having physical properties such as arbitrary mechanical strength and elastic recovery required as fine particles Since it easier to obtain, and the one or two or more kinds of polymerizable monomer having an ethylenically unsaturated group (co) resin fine particles comprising resins obtained by polymerizing is preferably used. These resin fine particles may be used alone or in combination of two or more. The above (meth) acrylate means acrylate or methacrylate, and the above (co) polymerization means homopolymerization or copolymerization.

  When polymerizing a polymerizable monomer having an ethylenically unsaturated group to obtain resin fine particles, resin fine particles can be obtained by copolymerizing a non-crosslinkable monomer and a crosslinkable monomer together. Is preferred. By using a crosslinkable monomer in combination, the gel fraction of the resin fine particles obtained is improved, and the mechanical strength, elastic recovery rate, heat resistance, etc. of the resin fine particles and thus the conductive fine particles are further improved. .

  The non-crosslinkable monomer is not particularly limited. For example, styrene, α-methylstyrene, β-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, 2, 4-dimethylstyrene, 2,5-dimethylstyrene, 3,4-dimethylstyrene, 3,5-dimethylstyrene, 2,4,5-trimethylstyrene, 2,4,6-trimethylstyrene, p- (n-butyl ) Styrene, p- (t-butyl) styrene, p- (n-hexyl) styrene, p- (n-octyl) styrene, p- (n-dodecyl) styrene, p-methoxystyrene, p-phenylstyrene, p -Styrene monomers such as chlorostyrene, chloromethylstyrene, 3,4-dichlorostyrene; Carboxylic monomers such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride; methyl (meth) Acrylate, ethyl (meth) acrylate, propyl (meth) Alkyl (such as acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, etc. (Meth) acrylate monomers; 2-hydroxyethyl (meth) acrylate, glycerol (meth) acrylate, polyoxyethylene (meth) acrylate, glycidyl (meth) acrylate, and other oxygen atom-containing (meth) acrylate monomers ; Unsaturated nitrile monomers such as acrylonitrile and methacrylonitrile; Vinyl ether monomers such as methyl vinyl ether, ethyl vinyl ether, and propyl vinyl ether; Vinyl acetate, vinyl butyrate, vinyl laurate, vinyl stearate, etc. Bi Unsaturated hydrocarbon monomers such as ethylene, propylene, isoprene and butadiene; vinyl chloride, vinyl fluoride, trifluoromethyl (meth) acrylate, pentafluoroethyl (meth) acrylate, etc. And halogen group-containing monomers. These non-crosslinkable monomers may be used alone or in combination of two or more.

  In addition, the crosslinkable monomer is not particularly limited. For example, polyfunctional vinyl monomers such as divinylbenzene and divinyltoluene; tetramethylene di (meth) acrylate, ethylene glycol di (meth) acrylate, polyethylene Glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, ethylene oxide di (meth) acrylate, tetraethylene oxide (meth) acrylate, 1,6-hexane di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1, 9-nonanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane di (meth) acrylate, tetramethylolmethanetri (meth) acrylate, tetramethylolmethanetetra (meth) acrylate, tetramethylo Polyfunctional (meth) acrylates such as propanetetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, glycerol di (meth) acrylate, glycerol tridi (meth) acrylate; vinyltrimethoxysilane, trimethoxysilylstyrene, γ -(Meth) acryloxypropyltrimethoxysilane and other silane-containing monomers; triallyl isocyanurate, diallyl phthalate, diallyl acrylamide, diallyl ether and other allyl group-containing monomers, 1,3-butadiene, Examples thereof include conjugated diene monomers such as isoprene.

  These crosslinkable monomers may be used alone or in combination of two or more. The amount of the crosslinkable monomer used when the non-crosslinkable monomer and the crosslinkable monomer are used in combination is not particularly limited, but should contain 5% by weight or more of the crosslinkable monomer. More preferably, it contains 20% by weight or more of the crosslinkable monomer, and particularly preferably 60 to 98% by weight. If the amount of the crosslinkable monomer used is less than 5% by weight, the gel fraction of the resulting resin fine particles is not sufficiently improved, and there is a tendency that stickiness appears or the thermoplastic properties become strong. .

  In producing the resin fine particles, if necessary, a polymerization initiator, a polymer protective agent (protective colloid), a dispersion stabilizer, a swelling aid, a chain transfer agent, a viscosity modifier, a colorant (dye or pigment), One kind or two or more kinds of various additives such as an antifoaming agent may be used.

  The polymerization initiator is not particularly limited. For example, azo compounds such as azobisisobutyronitrile, azobiscyclohexacarbonitrile, azobis (2,4-dimethylvaleronitrile); benzoyl peroxide, peroxide Organic peroxides such as lauroyl, orthochlorobenzoyl peroxide, orthomethoxybenzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, t-butylperoxy 2-ethylhexanoate, di-t-butyl peroxide Thing, etc. are mentioned. These polymerization initiators may be used alone or in combination of two or more. As such a polymerization initiator, among the polymerization initiators, an azo compound having a range of 60% by weight or more, preferably 70% by weight or more, more preferably 80 to 100% by weight is used. Such curing facilitates obtaining fine particles with desired performance.

  The amount of the polymerization initiator used is not particularly limited, but is preferably 0.1 to 10 parts by weight of the polymerization initiator with respect to 100 parts by weight of the total amount of the polymerizable monomers. When the amount of the polymerization initiator used is less than 0.1 parts by weight relative to 100 parts by weight of the total amount of polymerizable monomers, the polymerization reaction may not proceed smoothly. When the amount of the polymerization initiator used relative to 10 parts exceeds 10 parts by weight, the degree of polymerization (molecular weight) of the resin fine particles obtained becomes too low, and the mechanical strength and heat resistance of the resin fine particles and thus the conductive fine particles become insufficient. There is a thing. Particularly preferred is 0.5 to 5 parts by weight.

  A polymer protective agent can be used. The polymer protective agent (protective colloid) is not particularly limited, and examples thereof include water-soluble polymers such as polyvinyl alcohol, polyvinyl pyrrolidone, and hydroxyethyl cellulose. These polymer protective agents (protective colloids) may be used alone or in combination of two or more.

  A dispersion stabilizer can be used. The dispersion stabilizer is not particularly limited, but examples thereof include anionic surfactants such as carboxylate, sulfonate, sulfate ester salt, phosphate ester salt, etc .: aliphatic amine salt, aliphatic quaternary ammonium salt Cationic surfactants such as: Amphoteric surfactants such as carboxybetaine, sulfobetaine, aminocarboxylate and imidazoline derivatives; Nonionic surfactants such as ether type, ether ester type, ester type and nitrogen-containing type Etc. These dispersion stabilizers may be used alone or in combination of two or more.

  A swelling aid can be used. The swelling auxiliary agent is not particularly limited as long as it can promote the adsorption or absorption to the seed particles (seed particles) in the seed polymerization method or the dispersion seed polymerization method, and examples thereof include alcohols such as ethanol. And isoamyl. These swelling aids may be used alone or in combination of two or more.

  Chain transfer agents can be used. The chain transfer agent is not particularly limited, and examples thereof include mercaptan compounds such as alkyl mercaptans. These chain transfer agents may be used alone or in combination of two or more.

  Next, the conductive layer formed on the surface of the resin fine particles is made of a conductive material. As the conductive material, metals such as Ni, Cu, Au, Ag, Pd, and In can be used. The thickness of the conductive layer is preferably 50 to 10,000 mm, more preferably 500 to 2000 mm.

  The method of forming the conductive layer on the surface of the resin fine particles is not particularly limited, and for example, electroless plating, vapor deposition, sputtering, ion plating, physical dry or wet coating, etc. can be used, and a known method It can be done with. In a preferred example, a Ni layer and an Au layer were formed on the resin particles by a known electroless plating technique to obtain conductive particles.

  Conductive fine particles are used as conductive materials in conductive adhesives, preferably anisotropic conductive adhesives, and epoxy and adhesive substrates that are cured by changes in environmental temperature when using continually processed products Even if expansion and contraction are repeated, the reliability of conduction can be maintained even with repeated changes.

  The conductive fine particles are used as a conductive substance in a conductive adhesive, preferably an anisotropic conductive adhesive. The adhesive component in the conductive adhesive is not particularly limited, but may include various known adhesive components, thermosetting resins such as epoxy resins, and the like.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

(Example 1)
In advance, 20 parts by weight of 1,6-hexanediol, 1 part by weight of n-lauryl acrylate and 0.2 parts by weight of azobisisobutyronitrile as a polymerization initiator are placed in a beaker as monomers, and mixed uniformly. Prepare a meter solution.

  Separately, in a separable flask reactor, put 20 parts by weight of a 5% aqueous solution of polyvinyl alcohol (manufactured by Nippon Synthetic Chemical), add the monomer solution to this, and after stirring well, 120 parts by weight of ion-exchanged water Add.

  Next, while stirring this solution, the reaction is carried out at 80 ° C. for 18 hours under a nitrogen stream. The obtained fine particles are washed with hot water, and then classified to obtain resin particles having an average particle diameter of 3.8 μm and a Cv value of 4.8%.

  The resin particles are plated to obtain conductive fine particles having a nickel layer of 750 mm and a gold layer of 300 mm. About arbitrary 300 particles from the obtained electroconductive fine particles, a particle diameter is measured with an electron microscope, and an average particle diameter and particle diameter distribution are calculated | required. The values obtained are shown in Table 1.

(Example 2)
A polymerization reaction or the like is performed in the same manner as in Example 1, and classification is performed to obtain resin particles having an average particle size of 6.1 μm and a Cv value of 4.2%. The resin particles are plated to obtain conductive fine particles having a nickel layer of 800 mm and a gold layer of 350 mm. About arbitrary 300 particles from the obtained electroconductive fine particles, a particle diameter is measured with an electron microscope, and an average particle diameter and particle diameter distribution are calculated | required. The values obtained are shown in Table 1.

(Example 3)
A polymerization reaction and the like are performed in the same manner as in Example 1, and resin particles having an average particle diameter of 10 μm and a Cv value of 4.1% are obtained by classification. The resin particles are plated to obtain conductive fine particles having a nickel layer of 900 mm and a gold layer of 400 mm. About arbitrary 300 particles from the obtained electroconductive fine particles, a particle diameter is measured with an electron microscope, and an average particle diameter and particle diameter distribution are calculated | required. The values obtained are shown in Table 1.

(Example 4)
In advance, put 20 parts by weight of 1,6-hexanediol as a monomer, 0.2 parts by weight of n-lauryl acrylate and 0.2 parts by weight of azobisisobutyronitrile as a polymerization initiator in a beaker, and mix uniformly. Prepare body solution. Separately, in a separable flask reactor, put 20 parts by weight of a 5% aqueous solution of polyvinyl alcohol (manufactured by Nippon Synthetic Chemical), add the monomer solution to this, and after stirring well, 120 parts by weight of ion-exchanged water Add. Next, while stirring this solution, the reaction is carried out at 80 ° C. for 18 hours under a nitrogen stream. The obtained fine particles are washed with hot water, and then classified to obtain resin particles having an average particle diameter of 4.0 μm and a Cv value of 4.6%. The resin particles are plated to obtain conductive fine particles having a nickel layer of 750 mm and a gold layer of 300 mm. About arbitrary 300 particles from the obtained electroconductive fine particles, a particle diameter is measured with an electron microscope, and an average particle diameter and particle diameter distribution are calculated | required. The values obtained are shown in Table 1.

(Example 5)
A polymerization reaction or the like is carried out in the same manner as in Example 4, and resin particles having an average particle diameter of 5.9 μm and a Cv value of 4.5% are obtained by classification. The resin particles are plated to obtain conductive fine particles having a nickel layer of 780 mm and a gold layer of 320 mm. About arbitrary 300 particles from the obtained electroconductive fine particles, a particle diameter is measured with an electron microscope, and an average particle diameter and particle diameter distribution are calculated | required. The values obtained are shown in Table 1.

(Example 6)
In Example 1, as a monomer, 20 parts by weight of polyethylene glycol 200 diacrylate instead of 1,6-hexanediol, and 5 parts by weight of butyl acrylate instead of 1 part by weight of n-lauryl acrylate, As a polymerization initiator, using 0.12 parts by weight of azobisisobutyronitrile and 0.08 parts by weight of peroxyester, preparing a monomer solution in the same manner as in Example 1, similarly performing reaction with polyvinyl alcohol, etc. By classification, resin particles having an average particle size of 5.0 μm and a Cv value of 3.6% are obtained. The resin particles are plated to obtain conductive fine particles having a nickel layer of 800 mm and a gold layer of 200 mm. About arbitrary 300 particles from the obtained electroconductive fine particles, a particle diameter is measured with an electron microscope, and an average particle diameter and particle diameter distribution are calculated | required. The values obtained are shown in Table 1.

(Example 7)
In Example 6, as monomers, 20 parts by weight of 1,9-nonanediol diacrylate instead of polyethylene glycol 200 diacrylate and 0.6 parts by weight of 2-ethylhexyl acrylate instead of 5 parts by weight of butyl acrylate In the same manner as in Example 6, a monomer solution is prepared, similarly reacted with polyvinyl alcohol, and the like, and resin particles having an average particle size of 4.0 μm and a Cv value of 4.2% are obtained by classification. The resin particles are plated to obtain conductive fine particles having a nickel layer of 750 mm and a gold layer of 200 mm. About arbitrary 300 particles from the obtained electroconductive fine particles, a particle diameter is measured with an electron microscope, and an average particle diameter and particle diameter distribution are calculated | required. The values obtained are shown in Table 1.

(Comparative Example 1)
In advance, 20 parts by weight of trimethylolpropane triacrylate as a monomer and 0.2 parts by weight of benzoyl peroxide as a polymerization initiator are placed in a beaker and mixed uniformly to prepare a monomer solution. Separately, in a separable flask reactor, 20 parts by weight of a 5% aqueous solution of polyvinyl alcohol (manufactured by Nippon Synthetic Chemical) is added, and after adding the above monomer solution and stirring well, 120 parts by weight of ion exchange water is added. . Next, while stirring this solution, the reaction is carried out at 80 ° C. for 18 hours under a nitrogen stream. The obtained fine particles are washed with hot water, and then classified to obtain resin particles having an average particle diameter of 4 μm and a Cv value of 4.5%. The resin particles are plated to obtain conductive fine particles having a nickel layer of 800 mm and a gold layer of 300 mm. About arbitrary 300 particles from the obtained electroconductive fine particles, a particle diameter is measured with an electron microscope, and an average particle diameter and particle diameter distribution are calculated | required. The values obtained are shown in Table 1.

(Comparative Example 2)
The polymerization reaction is carried out in the same manner as in Comparative Example 1 except that isobornyl acrylate is used as the monomer. The obtained fine particles are washed with hot water, and then subjected to a classification operation to obtain resin particles having an average particle diameter of 4 μm and a Cv value of 4.8%. The resin particles are plated to obtain conductive fine particles of a nickel layer 760 mm and a gold layer 320 mm. About arbitrary 300 particles from the obtained electroconductive fine particles, a particle diameter is measured with an electron microscope, and an average particle diameter and particle diameter distribution are calculated | required. The values obtained are shown in Table 1.

(Comparative Example 3)
In advance, in a beaker, 7 parts by weight of urethane acrylate oligomer with a number average molecular weight of 2000, purple light 2000B (manufactured by Nippon Gosei Kagaku), 14 parts by weight of 1,6-hexanediol diacrylate as a monomer, and benzoyl peroxide 0.2 as a polymerization initiator A weight part is put and mixed uniformly to prepare a monomer solution. Separately, in a separable flask reactor, put 20 parts by weight of a 5% aqueous solution of polyvinyl alcohol (manufactured by Nippon Synthetic Chemical), add the monomer solution to this, and after stirring well, 120 parts by weight of ion-exchanged water Add. Next, while stirring this solution, the reaction is carried out at 80 ° C. for 18 hours under a nitrogen stream. The obtained fine particles are washed with hot water, and then subjected to a classification operation to obtain resin particles having an average particle size of 9.6 μm and a Cv value of 4.6%. The resin particles are plated to obtain conductive fine particles having a nickel layer of 800 mm and a gold layer of 300 mm. About arbitrary 300 particles from the obtained electroconductive fine particles, a particle diameter is measured with an electron microscope, and an average particle diameter and particle diameter distribution are calculated | required. The values obtained are shown in Table 1.

(Comparative Example 4)
The polymerization reaction is carried out in the same manner as in Example 1. The obtained fine particles are washed with hot water, and then subjected to a classification operation to obtain resin particles having an average particle diameter of 4.0 μm and a Cv value of 11.2%. The resin particles are plated to obtain conductive fine particles having a nickel layer of 750 mm and a gold layer of 300 mm. About arbitrary 300 particles from the obtained electroconductive fine particles, a particle diameter is measured with an electron microscope, and an average particle diameter and particle diameter distribution are calculated | required. The values obtained are shown in Table 1.

(Evaluation)
The following evaluation is performed on the conductive fine particles obtained in Examples 1 to 7 and Comparative Examples 1 to 4.

[1] (Load unloading repeated test)
Using a small compression tester (PCTM200) manufactured by Shimadzu Corporation, a load unloading test and its repeated test were performed, and the compression rate (%) and the compression rate when the same particles were compressed 20 times were the first The ratio (%) to the compression rate is obtained.

  The test results are shown in Table 1. In the table, the ratio (%) of the compression ratio when the same particle was repeatedly compressed 20 times to the first compression ratio was abbreviated as “ratio (%) to the first compression ratio”.

[2] (Continuity reliability test)
70 parts by weight of epoxy resin and 30 parts by weight of toluene are mixed uniformly, and 7 parts by weight of the resulting conductive fine particles are mixed and dispersed. Next, the conductive fine particle dispersion is applied on a PET single-sided release film with a constant thickness using an applicator, and toluene is evaporated to prepare an anisotropic conductive film. The film thickness is 30 μm.

  The obtained anisotropic conductive film is attached to the ITO electrodes (0.2 mm pitch) formed on the glass substrate. On top of this, ITO electrodes (0.2 mm pitch between electrodes) on another glass substrate are superposed, and a test piece is obtained by thermocompression bonding at 15 ° C. for 30 minutes while applying a pressure of 15 kgf / cm 2 with a press.

  This test piece was subjected to a 30-cycle temperature cycle test with a high temperature side of 150 ° C * 2 hours and a low temperature side of -20 ° C * 2 hours held in one cycle, and the electrical resistance value between the ITO electrodes before and after the treatment. Measure (Ω).

  The test results are shown in Table 1.

  As shown in Table 1, in Examples 1 to 7, the fine particles have predetermined physical properties even when a metal layer is plated on the surface, and extremely good conduction stability as conductive fine particles in the anisotropic conductive film. Indicates.

  The fine particles of the present invention are appropriately deformed even when compressed, and recover moderately when the pressure is removed. Therefore, when such fine particles are placed between two electrodes as conductive fine particles and pressed, the conductive particles follow and deform even if there are fluctuations in the distance between electrodes and the applied pressure due to changes in ambient temperature, etc. Therefore, stable conduction between the two electrodes can be maintained, which is very useful as a conductive substance such as a conductive adhesive.

Claims (4)

Resin fine particles for conductive fine particles disposed between two electrodes,
The resin fine particles are obtained by copolymerization of a monofunctional monomer and a bifunctional monomer. In the load unloading test, the fine particles are compressed at a load load rate of 1.42196 mN / sec. (1):
P = 7/96 × d2 × 9.80665 / 1000 (1)
[Wherein, d is the number average particle diameter (μm) of fine particles, and P (N) is a value obtained by rounding off the second digit after the decimal point. ]
It has a compression ratio of 50% or more when the load value P (N) represented by is reached, and the ratio of the compression ratio when the fine particles are repeatedly compressed 20 times is 80% or more of the first compression ratio. der is,
Resin fine particles, wherein the fine particles have a Cv value of 10% or less .   2. The resin fine particles according to claim 1, wherein 60% by weight or more of an azo compound is used as a polymerization initiator.   3. The resin fine particles according to claim 1 or 2, wherein the fine particles have a number average particle diameter in a range of 1 μm to 10 μm. A conductive fine particle comprising resin fine particles as a substrate and a conductive layer on the surface of the resin fine particles, and used for an anisotropic conductive adhesive, wherein the resin fine particles are any one of claims 1 to 3. Conductive fine particles which are resin fine particles.