JP2011249233A - Method for producing conductive particle, and conductive particle produced by the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excellent conductive particle which holds an excellent compression characteristic belonging to a substrate polymer particle, has no deterioration in conductivity without any deterioration in the adhesion of a plated film even after being affected by compressive deformation, and has little load to environment and a human body, and a method for producing the conductive particle.SOLUTION: The method for producing the conductive particle includes: a primary dope step of doping iodine to a substrate polymer particle and adjusting a polymer/iodine compound; a secondary dope step of making metal species react on the polymer/iodine compound to adjust a metal iodide composite; a reduction step of reducing the metal iodide composite to a metal particle and scattering metal particles to be a core of a plating film on a substrate polymer surface; and an electroless deposition step of making the plating film grow with metals scattered on the substrate polymer particle surface obtained in the reduction step as a core.

Description

The present invention relates to a method for producing conductive particles and conductive particles obtained by the method for producing conductive particles.

In general, the conductive particles are used as conductive spacers for conducting vertical conduction of a glass substrate of a liquid crystal display. Also, mixed with binder resin, etc., for example, anisotropic conductive paste (ACP: Anisotropic Conductive Paste), anisotropic conductive ink, anisotropic conductive adhesive, anisotropic conductive film (ACF: Anisotropic Conductive Film) ), And is widely used as an anisotropic conductive material such as an anisotropic conductive sheet.

These conductive particles are used to electrically connect wired circuit boards and to wire small parts such as semiconductor elements in electronic devices such as liquid crystal televisions, plasma televisions, personal computers, mobile phones, and home appliances. In order to electrically connect to the road board, it is used by sandwiching it between the printed circuit board and electrode terminals, and the amount of use will continue to increase with the miniaturization, weight reduction, and flattening of equipment. It is expected to continue.

Conventionally, as conductive particles suitable for conductive spacers and anisotropic conductive materials, non-conductive fine particles such as resin fine particles and glass beads having a uniform particle diameter have been used as the base particle, Electroconductive fine particles in which a metal plating film such as nickel is formed by electroless plating have been reported (see Patent Documents 1 and 2).

As described in [0010] and [0011] of Patent Document 2, in the electroless plating, first, the surface of the substrate fine particles is degreased and then etched with chromic acid or the like. Thereafter, chromic acid is removed with hydrochloric acid or the like, and then a catalytic metal such as palladium is deposited on the surface of the substrate fine particles which have become uneven by etching, and a plating layer is formed by electroless plating using this catalyst as a nucleus.

Etching is indispensable for obtaining an anchoring effect by strongly adhering the plating film to the substrate fine particles. However, since chromic acid has a high environmental load and is harmful to the human body, a surface treatment method instead of etching has been demanded. In addition, the smoothness is impaired by the etching process, and further, the compression characteristics deteriorate due to the roughening of the surface by the etching process.

On the other hand, although the present inventors developed the electroconductive material of patent document 3 in the past, it was not necessarily satisfactory about electroconductive performance and a compression characteristic. Furthermore, the present inventors previously proposed a method for producing conductive particles by reacting and reducing metal species with a polymer / iodine complex (Japanese Patent Application No. 2009-083096). There was room for further improvement.

JP 09-306231 A JP 2003-064500 A Table 2007-086392

The present invention retains the good compressive properties of the base polymer particles, does not reduce the adhesion of the plating film even after being subjected to compressive deformation, does not lower the electrical conductivity, and has less load on the environment and the human body. An object is to provide excellent conductive particles and a method for producing the conductive particles.

The present invention relates to a primary dope process for adjusting a polymer / iodine complex by doping iodine with respect to base polymer particles, and a metal iodide composite by reacting a metal species with the polymer / iodine complex. A secondary dope process for adjusting the metal iodide composite, a reduction process for reducing the metal iodide composite to metal fine particles, and interspersing metal fine particles serving as the core of the plating film on the surface of the base polymer, and a group obtained by the reduction process The above-mentioned problems are solved by a method for producing conductive particles, characterized by comprising an electroless plating step in which a plating film is grown using the metal scattered on the surface of the polymer particles as a nucleus.

The present inventors have obtained the following knowledge in Patent Document 3 described above. That is, a polyiodine complex (polymer / iodine complex) obtained by immersing a polymer substrate (film) in a solution containing polyiodine ions (In ⁻ : n is 3 or 5) is an untreated polymer. Since the diffusibility and permeability of ions and molecules are higher than the base material, secondary-doped metal ions are easily diffused, and the metal ions and polyiodine ions react to cause the metal fine particles to become polymer groups. It is generated inside the material (described in [0008]), and is heated in the air, whereby metal fine particles are deposited on the surface of the polymer substrate.

The present invention is an applied invention developed based on the above findings. In the present invention, the polymer / iodine complex is first formed by immersing the base polymer particles in a solution containing polyiodine ions at a predetermined concentration (primary doping step). Next, the polymer / iodine complex is immersed in a solution (metal salt solution) containing a predetermined concentration of metal species to form a trace amount of metal iodide composite (secondary doping step). Then, by reducing the metal iodide composite, metal fine particles are interspersed on the surface of the polymer particles to make the surface of the polymer particles uneven (reduction process). Furthermore, a plating film is grown by electroless plating using the metal on the surface of the polymer particles as a nucleus (electroless plating step).

The greatest feature when the present invention is compared with Patent Document 3 and Japanese Patent Application No. 2009-083096 is that the amount of metal iodide composite formed on the surface of the polymer particles is made very small by making the amount of metal iodide composite formed very small. It is. In other words, the present invention reduces the amount of metal iodide composite produced by diluting the simple elemental iodine for primary doping more than before, or by diluting the metal species for secondary doping than before. is there. Since the absolute amount of the metal iodide composite is small, when it is reduced, metal fine particles are scattered on the surface of the polymer particles. As a result, the surface of the particles becomes uneven as if etching was performed. The present invention obtains a good anchoring effect by this uneven shape, and makes the fixing of the plating film stronger.

The primary doping step is a step of adjusting the polymer / iodine complex by doping iodine with respect to the base polymer particles. In the case of diluting simple iodine and precipitating a minute amount of metal particles on the surface of the polymer particles, the base polymer particles are immersed in a solution containing 5 × 10 ^{−6 to} 5 × 10 ⁻³ N simple iodine. Good. The concentration of simple iodine is more preferably 1 × 10 ^{−5 to} 5 × 10 ⁻³ N, and particularly preferably 1 × 10 ^{−4 to} 3 × 10 ⁻³ N. In a subsequent secondary doping step, a metal equivalent of a chemical equivalent amount or more (1 × 10 ⁻⁴ to 8 × 10 ⁻² N, more preferably 1 × 10 ^{−3 to} 5 × 10 ⁻² N) is doped. Thus, a trace amount of metal iodide composite can be formed. If the concentration of simple iodine exceeds the above range, when adding an excessive amount of metal species to the simple iodine in the secondary doping step, the amount of metal fine particles deposited on the base polymer particles becomes excessive. Thereby, unevenness of the surface of the base polymer particles becomes insufficient, and the anchoring effect cannot be obtained. Furthermore, the surface of the base polymer particles is distorted and cannot be made conductive particles having uniform conductivity. On the other hand, when the concentration of the simple iodine is below the above range, the unevenness of the surface of the base polymer particles becomes insufficient, and the anchoring effect cannot be obtained.

Since iodine is not very soluble in water, other components may be added as necessary when the solvent is water. There is no restriction | limiting in particular as another component, According to the objective, it can select suitably, For example, an iodine compound, an organic compound, etc. are mentioned.

The secondary doping step is a step of preparing a metal iodide composite by reacting a metal species with the polymer / iodine complex formed in the primary doping step. Here, the metal iodide composite refers to iodine ions separated from polyiodine, which is a constituent element of the polymer / iodine complex, and the metal species diffused in the polymer / iodine complex. To form a metal iodide.

When a small amount of metal species added in the secondary doping step is used to deposit a small amount of metal particles on the surface of the polymer particles, the polymer / iodine complex contains 5 × 10 ^{−6 to} 5 × 10 ⁻³ N metal species. What is necessary is just to carry out by immersing in a solution. The concentration of the metal species is more preferably 1 × 10 ^{−5 to} 5 × 10 ⁻³ N, and particularly preferably 1 × 10 ^{−4 to} 3 × 10 ⁻³ N. In this case, in the preceding primary dope process, a polymer equivalent of a chemical equivalent or more (1 × 10 ⁻⁴ to 8 × 10 ⁻² N, more preferably 1 × 10 ^{−3 to} 5 × 10 ⁻² N) / If an iodine complex is formed, a trace amount metal iodide composite can be formed. When the concentration of the metal species exceeds the above range, the amount of the metal fine particles deposited on the base polymer particles becomes excessive. Thereby, unevenness of the surface of the base polymer particles becomes insufficient, and the anchoring effect cannot be obtained. Furthermore, the surface of the base polymer particles is distorted and cannot be made conductive particles having uniform conductivity. On the other hand, if the concentration of the metal species is below the above range, the unevenness of the surface of the base polymer particles becomes insufficient, and the anchoring effect cannot be obtained.

According to the production method of the present invention, it is possible to produce conductive particles having a surface resistance value of 5 to 10 ² Ω, 5 to ²⁰ Ω, and the like having excellent conductivity. As described above, since high conductivity can be maintained even after pressure deformation, it can be preferably used for applications such as conductive spacers and anisotropic conductive paste under pressure.

The plating film formed by the method of the present invention has excellent compression characteristics, and the coating film layer of the plating is not easily cracked or peeled off. Therefore, electrical resistance does not increase even during compression, and conductive particles having high electrical conductivity can be obtained. Moreover, according to the manufacturing method of the present invention, it is possible to omit the etching process, which is a problem for both the human body and the environment, which is a problem. Furthermore, a small amount of fine metal particles deposited on the base polymer particles function as a catalyst, which brings about the effect of promoting the formation of a plating film.

Further, by omitting the etching step, it is possible to maintain good compression characteristics of the base polymer particles themselves. Furthermore, according to the production method of the present invention, it is possible to ensure the smoothness of the surface of the conductive particles and reduce the variation in conductivity among the particles.

According to the production method of the present invention, conductive particles having a surface resistance value of 5 to 10 ² Ω can be easily produced.

It is a conceptual diagram of the method of measuring the compression conductivity of electroconductive particle. It is the graph which showed the relationship between the compression displacement (micrometer) at the time of the compression displacement of the electroconductive particle which provided the plating film of Example 1, and test force (gf). It is the graph which showed the relationship between the compression displacement (micrometer) at the time of the compression displacement of the electroconductive particle which provided the plating film of Example 1, and resistance value (ohm). 3 is a TEM image of conductive particles of Example 2. The conductive particles are those after the reduction step, and are in a state before the plating film is applied. 4 is a SEM image of conductive particles of Example 2. The conductive particles are those after the reduction step, and are in a state before the plating film is applied. 6 is a TEM image of conductive particles of Example 5. The conductive particles are those after the reduction step, and are in a state before the plating film is applied. 6 is a SEM image of conductive particles of Example 5. The conductive particles are those after the reduction step, and are in a state before the plating film is applied.

(Method for producing conductive particles)
A primary dope step of adjusting the polymer / iodine complex by doping iodine with respect to the base polymer particles, and adjusting the metal iodide composite by reacting a metal species with the polymer / iodine complex 2 Subsequent doping step, reduction step of reducing the metal iodide composite to fine metal particles, and scattering of fine metal particles serving as the core of the plating film on the surface of the base polymer surface, and base material particle surface obtained in the reduction step At least an electroless plating process for growing a plating film using the metal scattered in the core as a nucleus, and further includes other processes as necessary.

<Primary dope process>
The primary dope step is a step of preparing a polymer / iodine complex by doping (adding) iodine to the base polymer particles. The polymer / iodine complex referred to in the present invention is a polymer in which polyiodine is dispersed and adsorbed. As described in Patent Document 3, for example, a structure in which polyiodine is included by hydrogen bonding between molecules of a polymer, or a structure in which polyiodine is coordinated with an amide group on a molecular chain or a side chain as a coordination site Coordination loci are formed between molecular chains due to aggregation of molecular chains such as crystals, and even in single molecular chains, coordination loci are formed by the arrangement of polar groups on the molecular chain and the pitch change of the helical structure. What is done.

―Base polymer particles―
The polymer material of the base polymer particles is not particularly limited as long as it is a polymer compound that can include iodine, and can be appropriately selected depending on the purpose. For example, thermoplastic resin, thermosetting resin Etc.

Examples of the thermoplastic resin include vinyl chloride resin, vinyl acetate resin, polystyrene resin, polyester resin, polyethylene resin, polypropylene resin, acrylic resin, polyamide resin, and acetal resin.

Examples of the thermosetting resin include phenol resin, melamine resin, benzoguanamine resin, alkyd resin, polyurethane resin, epoxy resin, cross-linked acrylic resin, unsaturated polyester resin, vinyl polymer, silicon resin, and the like.

Among these, a crosslinked acrylic resin, a vinyl polymer, and a benzoguanamine resin are preferable. The said polymeric material may be used individually by 1 type, and may be used in combination of 2 or more type.

There is no restriction | limiting in particular as said alkaline solution, According to the objective, it can select suitably. For example, sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, sodium carbonate aqueous solution, calcium hydroxide aqueous solution, ammonia water, sodium hydrogen carbonate aqueous solution, etc. are mentioned. In the present specification, the polymer material includes those partially hydrolyzed with the alkaline solution. The high molecular compound capable of including iodine means a high molecular compound capable of taking a structure in which the iodine component diffuses to the inside and is adsorbed or non-covalently associated in the molecule.

-Production method-
There is no restriction | limiting in particular as a manufacturing method of the said base polymer particle, According to the objective, it can select suitably. Examples thereof include suspension polymerization, seed polymerization, soap-free polymerization, dispersion polymerization, emulsion polymerization, electrostatic spraying method, ink jet method, and microchannel method. Commercial products can also be used.

The suspension polymerization is a method in which a monomer is dropped into an aqueous solution to which a protective colloid is added, stirred, droplets are formed by the surface tension of the monomer white matter, and heated to obtain the base polymer particles. .

With the seed polymerization, seeds such as polystyrene and PMMA (polymethylmethacrylate) are deposited in water to form uniform microparticles, and the microparticles absorb and enlarge the monomer, and then heat, This is a method for obtaining base polymer particles.

The soap-free polymerization is the formation of seed particles mainly using an anionic radical polymerization initiator such as persulfate under the condition that no surfactant is present, and the seed particles absorb and polymerize vinyl monomers. And obtaining the base polymer particles.

The dispersion polymerization is a method in which seed particles are formed in an organic solvent such as alcohol, and vinyl monomer is absorbed and polymerized in the seed particles to obtain the base polymer particles.

The emulsion polymerization is the formation of uniform monomer droplets from uniform pores, followed by heating to obtain particles, so-called membrane emulsification dispersion or SPG (shirasu porous glass) emulsification to form droplets and then heating It is a method of obtaining the base polymer particles by curing.

The electrostatic spraying method is a method in which a polymer solution is placed in a syringe and a high voltage and pressure are applied to form uniform droplets and the solvent is evaporated to obtain the base polymer particles.

The inkjet method is a method in which the polymer solution is uniformly formed into droplets with an inkjet and at the same time the solvent is evaporated to obtain the base polymer particles.

The microchannel method is a method of obtaining the base polymer particles by taking out a monomer from fine holes having a special shape, forming uniform droplets, and then curing by heating. Among these, seed polymerization and a method of further classifying particles obtained by other polymerization methods are preferable in that a uniform particle diameter can be obtained.

Among the methods for producing the base polymer particles, when a monomer is cured by applying heat, a polymerization initiator for polymerizing the monomer is necessary.

-monomer-
The monomer is not particularly limited and may be appropriately selected depending on the intended purpose. For example, styrene derivatives, vinyl esters, unsaturated nitriles, (meth) acrylic acid ester derivatives, conjugated dienes, polyfunctionality And monomers.

Examples of the styrene derivative include styrene, α-methylstyrene, p-methylstyrene, p-chlorostyrene, chloromethylstyrene, and the like. Examples of the vinyl esters include vinyl chloride, vinyl acetate, and vinyl propionate.

Examples of the unsaturated nitriles include acrylonitrile. Examples of the (meth) acrylic acid ester derivatives include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, and acrylic. Examples include stearyl acid, stearyl methacrylate, trifluoroethyl acrylate, and trifluoroethyl methacrylate.

Examples of the conjugated dienes include butadiene and isoprene. Examples of the polyfunctional monomer include bifunctional 1,4 butanediol diacrylate, 1,6 hexanediol diacrylate, 1,9 nonanediol diacrylate, butylene glycol diacrylate, and dicyclopentanyl diacrylate. Examples thereof include acrylate, diethylene glycol diacrylate, divinylbenzene, bifunctional or more trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, tetramethylolpropane tetraacrylate, and tetramethylolpropane tetramethacrylate. Among these, when a compressive strength such as a spacer is required, a bifunctional or higher functional monomer is preferable in that it has compressive elasticity and can suitably maintain the gap. On the other hand, when maintaining electrical conduction by compressing and deforming like an anisotropic conductive material, the bifunctional monomer alone, or the co-engagement of the bifunctional monomer and the monofunctional monomer, This is preferable in that the particles can be made flexible.

―Polymerization initiator―
There is no restriction | limiting in particular as said polymerization initiator, According to the objective, it can select suitably. Examples thereof include organic peroxides and azo compounds. Examples of the organic peroxide include benzoyl peroxide, lauroyl peroxide, orthochlorobenzoyl peroxide, orthomethoxybenzoyl peroxide, 8,5,5-trimethylhexanoyl peroxide, and t-butylperoxy-2-ethyl. Examples include hexanoate and di-t-butyl peroxide. Examples of the azo compound include azobisisobutyronitrile, azobiscyclohexacarbonitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), and the like.

―Polymerization temperature―
There is no restriction | limiting in particular as temperature of the said polymerization, Although it can select suitably according to the kind of monomer to be used, a polymerization initiator, etc., 25 to 100 degreeC is preferable and 50 to 90 degreeC is more preferable.

-Adjustment of particle size distribution-
When the desired Cv value, that is, the variation coefficient of the particle size distribution cannot be obtained as in the case of the suspension polymerization, or when the desired particle size cannot be obtained, the particle size distribution is adjusted by classification operation. is required. There is no restriction | limiting in particular as the method of the said classification operation, According to the objective, it can select suitably. Examples thereof include a dry classification method and a wet classification method. Examples of the dry classification method include a method of performing classification using a dry cyclone or wind power. Examples of the wet classification method include methods performed in water such as water classification, wet cyclone, electrostatic classification and the like. Whether or not the base polymer particles obtained by the production method are suitable as the base polymer particles used for the production of the conductive soot particles of the present invention depends on the particle diameter of the obtained base polymer particles and the coefficient of variation of the particle diameter. , Surface resistance value, strength, compression recovery rate, etc.

-Particle size-
There is no restriction | limiting in particular as a particle diameter of the said base polymer particle, Although it can select suitably according to the objective, 0.5 micrometer-500 micrometers are preferable, and 1 micrometer-100 micrometers are more preferable. When the number average particle size is less than 0.5 μm, in the electroless plating step to be described later, the base polymer particles are likely to be aggregated, and the conductive particles obtained from the base polymer particles that have undergone aggregation are It becomes a large particle of particle monster and causes a short circuit between adjacent electrodes. Further, the variation in the accuracy of the electrode is relatively greater than the accuracy of the particle diameter, and the conduction reliability is significantly reduced. When the number average particle diameter exceeds 500 μm, its use is very limited. When the conductive particles obtained by the method for producing conductive particles of the present invention are used as spacers, the particle diameter of the base polymer particles depends on the gap of the liquid crystal cell and is used as an anisotropic conductive material. When used, it depends on the distance between adjacent electrodes. In general, the anisotropic conductive material has been miniaturized and the distance between adjacent electrodes has been reduced, and the particle diameter tends to be smaller than 3 μm. However, when used as a spacer other than the liquid crystal, large particles of about 20 μm to 50 μm may be used.

-Measuring method-
There is no restriction | limiting in particular as a method of calculating | requiring the said particle diameter, According to the objective, it can select suitably. Examples include a method of measuring with an optical microscope, a method of measuring with an electron microscope, a method of measuring with a light scattering particle size distribution meter, and a method of measuring with a Coulter counter. The number average particle size can be obtained by statistically processing the particle size measured by these methods.

―Cv value (coefficient of variation) ―
The Cv value (coefficient of variation) of the particle diameter of the base polymer particles is such that the lower the value, the smaller the variation of the particle diameter, so that pressure is uniformly applied to all particles, and the conductive particles The conductive particles obtained by the production method have significantly improved conduction reliability. There is no restriction | limiting in particular as said Cv value, Although it can select suitably according to the objective, 10% or less is preferable, 5% or less is more preferable, and 3% or less is especially preferable. When the Cv value exceeds 10%, it becomes difficult for the conductive fine particles to arbitrarily control the distance between the electrodes facing each other. The CV value (variation coefficient) can be obtained by the following calculation formula.
Cv value (%) = (σ / Dn) x 100%
In the above formula, “σ” represents the standard deviation (μm) of the particle diameter, and “Dn” represents the number average particle diameter (μm).

―Surface resistance value―
There is no restriction | limiting in particular as surface resistance value of the said base polymer particle, According to the objective, it can select suitably. The method for measuring the surface resistance value is not particularly limited and can be appropriately selected depending on the purpose. For example, the microcompression tester (for example, MCT-W200J: manufactured by Shimadzu Corp.) A smooth indenter consisting of a metal cone with a diameter of 50 μm, a metal sample table, and a resistance meter (digital multimeter) are attached so that the surface resistance value of the base polymer particles can be measured, and the compression speed is 2.2 mN / sec. , One base polymer particle is compressed under the condition of a maximum test load of 10 g, and the minimum value among the resistance values obtained until the particle is compressed and displaced and the value of the base polymer particle is reduced. It can be a surface resistance value.

-Strength-
There is no restriction | limiting in particular as a method to measure the intensity | strength of the said base polymer particle, According to the objective, it can select suitably. For example, a method of measuring the compressive deformation strength, a method of measuring a compressive fracture load value, and the like can be mentioned.

―Compressive deformation strength―
The compressive deformation of the base polymer particles refers to deformation of the material under a compressive load. When a load of 10 g is applied to one particle of the base polymer particles, the particle diameter is deformed by 10% (hereinafter, “ The load value when it is sometimes referred to as “10% compression deformation” is referred to as S10 strength (10% compression strength). The method for measuring the S10 intensity is not particularly limited and may be appropriately selected depending on the purpose. For example, using a micro-compression tester (for example, MCT-W200J: manufactured by Shimadzu Corporation), the particle is a smooth indenter end face made of a diamond cone having a diameter of 50 μm, a compression speed of 2.6 mN / sec, and a maximum test load of 10 g The compression displacement (mm) when compressed under the above conditions can be measured and determined by the following Hiramatsu equation.
S10 = 2.8 × l0 ³ P × 1 / πd ²
In the Hiramatsu equation, “S10” is a load value (N) at 10% compression deformation of the base polymer particles, “P” is a compression displacement (mm) at 10% compression deformation of the base polymer particles, “d "" Represents a half phantom (mm) of the base polymer particle.

―Compressive fracture load value―
The compressive fracture load value of the base polymer particles refers to a load value when the base polymer particles begin to break under a compressive load. The compressive fracture load value is preferably 300 MPa to 3,000 MPa, more preferably 400 MPa to 1,500 MPa. When the compressive breaking load value is below the above range, the base polymer particles are broken when compressed and deformed, and the function as a conductive material is not achieved. When the compressive breaking load value exceeds the above range, when used as a spacer, it is not preferable because the color filter is broken or so-called low-temperature foaming is easily generated in the LCD at a low temperature.

The method for measuring the compression fracture load value is not particularly limited and can be appropriately selected depending on the purpose. For example, a micro compression tester (for example, MCT-W200J: manufactured by Shimadzu Corporation) is used, One base polymer particle is compressed on a smooth compression end face made of a diamond cone having a diameter of 50 μm under the conditions of a compression rate of 2.2 mN / sec and a maximum test load of 10 g. For example, a method of measuring a load value at the time when the rupture breaks.

―Compression recovery rate―
The compression recovery rate of the base polymer particles refers to the relationship between the load value and compression deformation when the load is reduced after the base polymer particles are compressed. There is no restriction | limiting in particular as a compression recovery rate of the said base polymer particle, Although it can select suitably according to the objective, 20% or more is preferable and 40% or more is more preferable. When the compression recovery rate is less than 20%, when conductive particles obtained by the method for producing conductive particles are compressed, they do not return to their original shape even when deformed. Failure to follow expansion and contraction of the binder and the like may cause a connection failure.

-Measuring method-
There is no restriction | limiting in particular as a measuring method of the said compression recovery rate, According to the objective, it can select suitably. For example, it can be measured by a micro compression tester (for example, MCT-W200J: manufactured by Shimadzu Corporation). Specifically, after the base polymer particles are compressed to a reverse load value of 9.8 mN, the end point when removing the load is set to an origin weight value of 0.98 mN, and the contraction speed in load and load removal is 0.284 mN. When measured as / sec, the amount of restoration (L1-L2), which is the difference between the displacement (L1) to the reversal point (L1) and the displacement (L2) from the reversal point to the point where the origin load value is taken, and reversal A value expressed by multiplying the ratio (L1−L2) / (L1) to the compression amount (L1), which is the displacement up to the point, by 100, can be used as the recovery rate (%). That is, it can be obtained by the following formula.
Compression recovery rate (%) = Restoration rate / Compression rate × 100 = 100 × (L1-L2) / L1
In the above formula, “L1” represents the displacement (μm) until inversion, and “L2” represents the displacement (μm) up to the origin load value.

-Iodine-
The iodine contains at least elemental iodine, and further contains other components as necessary. There is no restriction | limiting in particular as a state of the said iodine, Although it can select suitably according to the objective, The state of a solution is preferable. The iodine is in a solution state (hereinafter sometimes referred to as “iodine solution”. The other components are not particularly limited and may be appropriately selected depending on the intended purpose. For example, iodine compounds, organic compounds, etc. As described above, it is preferable that the iodine concentration is dilute as compared to the conventional case, and by forming the iodine concentration dilute, the formation of the metal iodide composite is moderately suppressed and deposited on the surface of the base polymer particles. The amount of metal fine particles to be reduced can be reduced, and the metal fine particles can be scattered.

―Iodine compounds―
When the iodine compound is added to the iodine solution, the solubility of the simple iodine in the iodine solution can be adjusted, and the amount and state of the iodine component doped into the base polymer particles can be controlled. preferable. There is no restriction | limiting in particular as said iodine compound, According to the objective, it can select suitably. For example, a metal iodide, an inorganic iodide, etc. are mentioned. Examples of the metal iodide include potassium iodide, sodium iodide, lithium iodide, rubidium iodide, cesium iodide, nickel iodide and the like. Examples of the inorganic iodine compound include ammonium iodide. The said iodine compound may be used individually by 1 type, and may be used in combination of 2 or more type. The concentration of the iodine compound in the iodine solution is not particularly limited and can be appropriately selected depending on the amount of the simple iodine, etc., but a molar ratio of 30 times or less of iodine is preferable, A concentration of 20 times or less that of iodine is more preferable. When the iodine compound has a molar ratio of 2 times or less, it is difficult to adjust the solubility of the simple iodine, and when the molar ratio exceeds 30 times the iodine concentration, iodine in the aqueous solution Although dissolution becomes easy, the diffusion performance of iodine into the resin is extremely lowered, and a metal iodide composite is hardly formed inside the resin.

―Organic compounds―
When the iodine is a solution, it is preferable in that the wettability of the base polymer particles with respect to the iodine solution can be mainly controlled by adding the organic compound to the iodine solution. The organic compound is not particularly limited and may be appropriately selected depending on the intended purpose.For example, monohydric alcohol, polyhydric alcohol, acetone, dimethyl sulfoxide, N, N-dimethylformamide, etc. Examples include organic solvents to be mixed. Examples of the monohydric alcohol include methanol, ethanol, isopropanol and the like. Examples of the polyhydric alcohol include ethylene glycol and glycerin. The said organic compound may be used individually by 1 type, and may be used in combination of 2 or more type. There is no restriction | limiting in particular as a state of the said organic compound, Although it can select suitably according to the objective, The state of aqueous solution is preferable. There is no restriction | limiting in particular as addition amount with respect to the water of the said organic compound, Although it can select suitably according to the objective, 5 mass%-90 mass% are preferable, and 20 mass%-80 mass% are more preferable. When the organic compound is less than 5% by mass, the diffusion performance of iodine with respect to the base polymer particles cannot be improved, and when it exceeds 90% by mass, the solubility of the iodine compound decreases.

―Iodine doping method―
In the primary doping step, a method for doping iodine is not particularly limited as long as the base polymer particles can form a polymer / iodine complex, and can be appropriately selected according to the purpose. . For example, a method of immersing the base polymer particles in an iodine solution, a method of spraying an iodine solution, a method of exposing to iodine vapor for a long time, a method of mixing and melting and molding iodine alone, etc. Among these, a method of immersing the base polymer particles in an iodine solution is preferable.

The doping temperature is not particularly limited and can be appropriately selected depending on the purpose. The doping can be performed at room temperature, but heating is preferable because the doping time can be shortened. There is no restriction | limiting in particular as the temperature of the said heating, Although it can select suitably according to the objective, 0 to 90 degreeC is preferable and 5 to 30 degreeC is more preferable. There is no restriction | limiting in particular as time to dope, According to the objective, it can select suitably. In addition, the conditions for doping iodine are not particularly limited and may be appropriately selected depending on the purpose. However, it is possible to uniformly dope iodine into the polymer fine particles under the ultrasonic irradiation treatment conditions. It is preferable at the point which can do.

―Metal species―
The metal species is preferably a metal that deposits on the surface of the base polymer particles and serves as a nucleus for forming a plating film by electroless plating. Here, “nucleus” means a nucleus that promotes adhesion of the plating film. Specifically, by setting the surface of the base polymer particles to be scattered with metal fine particles, it is possible to obtain a plating film that is firmly fixed to the particle surface without etching, with the surface being uneven. The metal to be doped is not particularly limited as long as it is a metal that can be electrolessly plated using the electrolessly plated metal fine particle doped particles as a nucleus, and can be appropriately selected according to the purpose. For example, gold, silver, copper, iron, nickel, cobalt, palladium, a platinum group element, etc. are mentioned. The metal species may be in a metal ion state.

When the metal species is reacted with the polymer / iodine complex, the metal species is preferably in a solution state, and the solution containing the metal species is preferably a metal salt solution. The metal salt is not particularly limited as long as it is a water-soluble metal salt, and can be appropriately selected according to the purpose. However, those that do not cause precipitation are preferable, for example, metal nitrate, metal sulfate, metal acetate Metal carbonates, metal chloride salts, metal bromide salts, metal iodides, and coordination compounds thereof. The solution may contain an organic solvent optionally mixed with water. The organic solvent is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include methanol, ethanol, isopropanol, ethylene glycol, glycerin, acetone, dimethyl sulfoxide, N, N-dimethylformamide and the like. .

Conversely, instead of diluting the concentration of simple iodine, the concentration of the metal iodide solution may be suppressed by diluting the concentration of the metal salt solution, or the concentration of both simple iodine and the metal salt solution. It is good also as a method of restraining formation amount and suppressing the formation amount of a metal iodide composite.

―Doping method of metal species―
The method of reacting the metal species in the secondary doping step is not particularly limited as long as the polymer / iodine complex is a method capable of forming a metal iodide composite, and is appropriately selected according to the purpose. can do. For example, a method of immersing the polymer / iodine complex in a solution containing a metal species, a method of spraying a solution containing a metal species, and the like can be mentioned. Among these, the polymer / iodine complex is changed to a metal species. The method of immersing in the solution to contain is preferable.

There is no restriction | limiting in particular as said doping temperature, According to the objective, it can select suitably. Although it can be carried out at room temperature, it is preferable to carry out the heating because the dope time can be shortened. There is no restriction | limiting in particular as the temperature of the said heating, Although it can select suitably according to the objective, 0 to 90 degreeC is preferable and 30 to 60 degreeC is more preferable. There is no restriction | limiting in particular as time to dope, According to the objective, it can select suitably. Further, the method of reacting the metal species is not particularly limited and may be appropriately selected depending on the purpose. However, the metal iodide can be formed more uniformly by performing the treatment under ultrasonic irradiation treatment conditions. It is preferable at the point which can be made.

In the secondary doping step, the polymer / iodine complex is immersed in a solution containing a metal species, or the polymer / iodine complex is sprayed with a solution containing the metal species, and then the metal iodide composite is formed. It can be stopped by washing with a solution containing no iodine or metal species.

Depending on the concentration, temperature, and treatment time of the iodine doping in the primary doping process, the reaction of the metal species in the secondary doping process, and the reagent solution at the time of the cleaning, the polymer / iodine complex may be contained inside the polymer / iodine complex. It is possible to re-elute the deposited metal salt and to perform optimum precipitation according to the penetration depth. Thereby, the concentration of the metal species on the surface of the metal iodide composite may be reduced.

The unreacted iodine component remaining inside the polymer particles may affect the metal layer after the reduction step or the electroless plating step, which will be described later, but the unreacted iodine component used an organic solvent such as acetone. It can be removed from the interior of the polymer particles by washing or high temperature heat treatment. In heat treatment, it is more effective to perform under reduced pressure because iodine can be efficiently volatilized at a lower temperature.

<Reduction process>
The reduction step is a step of preparing the metal fine particle dope particles by reducing the metal iodide composite to metal fine particles. In the present invention, since the absolute amount of the metal iodide composite is small, the absolute amount of the metal fine particles deposited on the surface is also small. The reduction of the metal on the surface of the base polymer particle is performed in the metal iodide composite by reducing the metal ion to the metal by electron donation by the reducing agent, and accompanying this, the iodine ion diffuses into the aqueous solution. It proceeds by being released from the polymer phase. There is no restriction | limiting in particular as a method to perform the said reduction | restoration, According to the objective, it can select suitably. Metal iodide usually has a very low ionic conductivity at room temperature, and ionic conduction is not induced under high temperature conditions (for example, about 150 ° C. or lower in the case of silver iodide). When a compound composite is formed, ion conduction and diffusion occur relatively easily even at room temperature without raising the temperature to the transition point. For this reason, the metal iodide composite is reduced to the metal fine particles because, for example, the metal ions easily move when left at a temperature close to room temperature (for example, 5 ° C. to 30 ° C.). . The time for performing the reduction is not particularly limited as long as the metal can be reduced, and can be appropriately selected according to the purpose.

The reduction can promote reduction to fine metal particles by a method such as reducing agent, complex ion formation, and heating. There is no restriction | limiting in particular as said reducing agent, According to the objective, it can select suitably, For example, acidic hydrogen peroxide solution, sodium borohydride, sodium thiosulfate etc. are mentioned. There is no restriction | limiting in particular as the temperature of the said heating, Although it can select suitably according to the objective, 80 to 200 degreeC is preferable and 20 to 80 degreeC is more preferable. There is no restriction | limiting in particular as a method to form the said complex ion, According to the objective, it can select suitably. For example, the method of immersing in the aqueous solution which added complexing agents, such as an ammoniacal compound and amines, etc. are mentioned. The metal iodide composite is preferably reacted with an appropriate amount of metal species as a catalyst.

<Electroless plating process>
The electroless plating process is a process in which electroless plating is performed using metal fine particles deposited and scattered on the surface of the polymer substrate particles as nuclei. Conductive conductive particles having a very low electrical resistance, in which the plating film is firmly adhered, are formed by the anchoring effect of the scattered metal fine particles. In the electroless plating step, a second plating film may be formed on the first plating film. By plating with a different type of metal from the first layer plating film, the second layer plating film has functions that cannot be achieved by the first layer plating, such as an antioxidant effect and long-term conduction. It is possible to provide a so-called migration preventing effect in which metal ions move and contaminate even a portion where insulation is necessary to cause insulation failure.

<Other processes>
There is no restriction | limiting in particular as said other process, According to the objective, it can select suitably. For example, second layer electroless plating process, molding process, crystallinity control, molecular weight control, isomerization by blending, viscosity control by crosslinking reaction, thermal treatment, environmental atmosphere during heat treatment, swelling by solvent, etc. For example, disposal.

―Plating agent―
The metal of the plating agent used in the electroless plating step is not particularly limited as long as it is deposited and scattered on the surface of the polymer particle base material to enhance the anchoring effect. For example, gold, silver, copper, platinum, nickel, palladium, tin, aluminum, iron, or the like can be used. There is no restriction | limiting in particular as a state of the said plating agent, Although it can select suitably according to the objective, The state of a solution is preferable. There is no restriction | limiting in particular as said solution, Although it can select suitably according to the objective, The mixed solution of water and ethanol is preferable. The mixing ratio of water and ethanol is not particularly limited and may be appropriately selected depending on the intended purpose. Water: ethanol is preferably 1: 4 to 4: 1 (V / V). There is no restriction | limiting in particular as a density | concentration of the said plating agent in the said aqueous solution, According to the objective, it can select suitably.

―Electroless plating method―
A method for plating with the metal fine particle doped particles as nuclei by the plating agent is not particularly limited and can be appropriately selected according to the purpose. For example, the metal fine particle doped particles are mixed with the plating agent. Examples include a method of immersing in a solution and a method of spraying a mixed solution containing the plating agent. Among these, a method of immersing the metal fine particle dope particles in a mixed solution containing the plating agent is preferable.

There is no restriction | limiting in particular as temperature which performs the said plating, Although it can select suitably according to the objective, 5 to 80 degreeC is preferable and 20 to 60 degreeC is more preferable. There is no restriction | limiting in particular as time to perform the said plating, Although it can select suitably according to the objective, 0.1 hours-120 hours are preferable, and it considers the uniformity and productivity of plating, and 1 hour- More preferred is 24 hours.

―Structure of electroless plating film layer―
As the structure of the electroless plating film layer, the first plating layer is not particularly limited as long as the first plating layer grows on the surface of the base polymer particles deposited and scattered metal fine particles. Not. It can be appropriately selected according to the purpose, and may be a single layer structure (for example, a single metal structure) composed of a single layer selected from the above materials, or a plurality of materials (for example, a plurality of materials) A laminated structure composed of a metal layer) may be used.

The thickness of the coating layer is not particularly limited and may be appropriately selected according to the purpose, but is preferably 1 nm or more, more preferably 2 nm to 1,000 nm, and particularly preferably 3 nm to 200 nm. When the thickness of the coating layer is less than 1 nm, there is a possibility that a portion lacking the plating coating layer may be generated, so that there is a risk of lowering the conduction reliability. Even if the thickness of the coating layer exceeds 100 nm, it is not preferable because it has no effect in improving the conductivity and the compression characteristics of the base polymer are lowered.

<Metal doped particles with plating layer>
There is no restriction | limiting in particular as a surface resistance value of the said electroconductive particle with a plating layer, Although it can select suitably according to the objective, 10 ² ohms or less are preferable and 10 ohms or less are more preferable. There is no restriction | limiting in particular as a method of measuring the said surface resistance value, According to the objective, it can select suitably, For example, the method etc. which confirm by a conductive compression test are mentioned.

<Conductive compression test>
An outline of the conductive compression test will be described with reference to FIG. A smooth indenter 1 made of a metal cone of 50 μm straight, made of metal, so that the surface resistance value of the conductive particles can be measured on a micro compression tester (for example, MCT-W200J: manufactured by Shimadzu Corporation) A sample stage 3 and a resistance measuring instrument 4 (RS-232C) are installed, and one conductive particle 2 is compressed under the conditions of a compression speed of 2.2 mN / sec and a maximum test load of 10 g. Then, the minimum value among the resistance values obtained before the breakage can be used as the conductivity evaluation.

<Application>
The metal-doped particles with a plating layer are a combination of the base polymer particles, the metal species used for the preparation of the metal iodide composite, the metal used for the electroless plating of the second layer, and the base material. It can be used as various functional materials according to the particle diameter of the polymer particles. For example, it can be used for conductive spacers, conductive materials for ACF, conductive materials for ACP, conductive materials for electronic paper, solder balls, and the like.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated more concretely, this invention is not restrict | limited to these Examples at all.

[Example 1: Conductive particles for conductive spacer]
<Primary dope process>
―Base polymer particles―
Haya beads L-11 (manufactured by Hayakawa Rubber Co., Ltd.) (particle shape: spherical) was used as the base polymer particles of the conductive spacer.

―Particle Monster―
After measuring 30,000 particles of acrylic resin spheres with Coulter Multisizer III (manufactured by Beckman Coulter, Inc.), the number average particle size was obtained by statistically embedding with a computer using the attached software. It was 6.60 μm. The calculated number average particle diameter (μm) was “Dn”, the standard deviation (μm) of the particle diameter was “σ”, and the Cv value (variation coefficient) of the particles was determined from the above formula.
Cv value (%) = (σ / Dn) x 100%
The Cv value (coefficient of variation) of the acrylic resin sphere particles was 4.5%.

―Surface resistance value―
A smooth indenter made of a metal cone with a diameter of 50 μm, a metal sample stage, and a resistance so that the surface resistance value of the acrylic resin can be measured on a micro compression tester (MCT-W200J: manufactured by Shimadzu Corporation) Attach a measuring instrument (digital multimeter 7351E made by ADC Corporation), compress one acrylic resin under the conditions of compression speed of 2.2 mN / sec and test load of 10 g. When the minimum value among the resistance values obtained in the meantime was measured, the surface resistance value of the acrylic resin was 4.8 × 10 ¹⁵ Ω.

―Compressive fracture load value―
Using a micro compression tester (MCT-W200J: manufactured by Shimadzu Corporation), the particles are smooth compression end faces made of a diamond cone having a diameter of 50 μm, under conditions of a compression speed of 2.2 mN / sec and a maximum test load of 10 g. When one acrylic resin sphere was compressed and the load value when the acrylic resin sphere was broken was measured, the compression failure load value of the acrylic resin sphere was 1,100 MPa.

―10% compressive strength―
The 10% compressive strength of the acrylic resin sphere was measured using a micro-compression tester (MCT-W200J: manufactured by Shimadzu Corporation). The acrylic resin sphere had a smooth indenter end face made of a diamond cone having a straight diameter of 50 μm and a compression speed of 2 The compression displacement (mm) when compressed under the conditions of 0.6 mN / sec and a maximum test load of 10 g was measured and determined by the following Hiramatsu equation.
10 = 2.8 × 10 ³ P × 1 / πd ²
The 10% compressive strength of the acrylic resin sphere was 680 MPa.
―Compression recovery rate―
The compression recovery rate of the acrylic resin sphere is determined by compressing the acrylic resin sphere to a reverse load value of 9.8 mN using a micro compression tester (MCT-W200J: manufactured by Shimadzu Corporation), then removing the load and determining its end point. The origin load value was 0.98 mN, and the compression rate at load and load removal was 0.284 mN / sec. The displacement from the reversal point to the point where the origin load value was obtained was defined as “L2”, and the displacement from the reversal point to “L1” was obtained by the following formula.
Compression recovery rate (%) = Restoration rate / Compression rate x l00 = 100 x (L1-L2) / L1
The compression recovery rate of the acrylic resin sphere was 90%.

―Iodine doping―
3 g of the acrylic resin sphere was charged into 20 mL of a 50% by mass ethanol aqueous solution (hereinafter sometimes referred to as “iodine-ammonium iodide solution”) in which 0.01 mM iodine and 0.2 mM ammonium iodide were dissolved. . At this time, the aggregates of the large resin fine particles were previously crushed. It was immersed in the iodine-ammonium iodide solution kept at 10 ° C. for 10 to 20 minutes to obtain an acrylic resin ball iodine complex.

<Secondary dope process>
The acrylic resin spherical iodine complex obtained in the primary dope process was washed with a 50% by mass aqueous ethanol solution while filtering. The iodine complex formed inside or on the surface of the acrylic resin sphere was immersed in a 50 mM silver nitrate-50 mass% ethanol aqueous solution for 4 days to react with the metal species to obtain a silver iodide composite.

<Reduction process>
After the silver iodide composite obtained in the secondary doping step is washed with 50% by mass ethanol, it is further reduced to metallic silver by heating in air at 180 ° C. for 72 hours to 150 hours. Then, silver fine particles were deposited on the surface of the base polymer particles.

<Electroless plating process>
The particles obtained by precipitating silver fine particles obtained in the reduction step were put into a mixed solution of water / ethanol (water: ethanol = 1: 1 (V / V)) in which 0.05 M silver nitrate was dissolved, A silver plating film layer was formed under reaction conditions of 60 ° C. and 24 hours to 120 hours. By observing from these particles under a high-magnification optical microscope using transmitted light, the particles appearing black were selected as fine particles that had been plated, and conductive particles for conductive spacers were obtained.

<Conductive compression test>
-Method-
The surface resistance value of the conductive particles for the conductive spacer was measured by a conductive compression test shown in FIG. That is, a smooth indenter 1 made of a metal cone having a diameter of 50 μm is used to measure the surface resistance value of the conductive particles for the conductive spacer on a micro compression tester (MCT-W200J: manufactured by Shimadzu Corporation). A sample stage 3 and a resistance measuring instrument 4 (digital multimeter 7351E manufactured by ADC Corporation) are attached, and one conductive particle 2 for a conductive spacer under the condition of a compression speed of 2.2 mN / sec and a maximum test load of 10 g. The minimum value among the resistance values obtained until the conductive particles for the conductive spacer were compressed and displaced and destroyed was used as the evaluation of conductivity.

-result-
FIG. 3 shows the minimum resistance value measured by the above method. As is clear from FIG. 3, it was 15.0Ω in the conductive particles provided with the plating film of Example 1. Further, as shown in FIG. 2, the load when the conductive particles of Example 1 were broken was 5.0 gf. From this result, the conductive particles for conductive spacers obtained in Example 1 retain the good compression characteristics of the acrylic resin which is the base polymer particle, and the silver plating film formed on the particle surface. It was observed that it has excellent conductivity.

Furthermore, when the conductive particles obtained in Example 1 were observed with an electron microscope, a very smooth surface could be observed. The measurement of the minimum resistance value and the measurement of the breakdown point were performed by preparing 10 conductive particles according to Example 1. However, all the conductive particles showed variations in the minimum resistance value and the numerical value of the breakdown point. I couldn't.

When the electroconductive particle of Example 1 was used as an electroconductive spacer, it maintained favorable electroconductivity over a long period of time, and exhibited high compression reliability.

[Example 2: ACF conductive particles]
<Primary dope process>
―Base polymer particles―
Acrylic resin spherical powder produced by the following method was used as the base polymer particles of the conductive particles for ACF. That is, in dispersion polymerization, 9 g of PVP (polyvinylpyrrolidone) K-30 (manufactured by Nippon Shokubai Co., Ltd.) was dissolved in 180 g of ethanol, and then azobisisobutyronitrile (Japanese A solution obtained by dissolving 0.05 g (manufactured by Koyo Pharmaceutical Co., Ltd.) was added and reacted by stirring at 50 rpm and 80 ° C. for 16 hours while blowing nitrogen, and a uniform particle dispersion (polystyrene dispersion) of polystyrene 400 nm was obtained. Obtained.

Next, 10 g of 1-chlorododecane was added to 50 g of water in which 1% by mass SDS (sodium dodecyl sulfate) was dissolved, and dispersion treatment 1 was obtained by dispersing with an ultrasonic homogenizer for 1 hour. The dispersion 1 was added to the polystyrene dispersion and stirred at room temperature for 16 hours at 50 rpm to absorb 1-chlorododecane into polystyrene particles to obtain a 1-chlorododecane-absorbing polystyrene particle dispersion.

BPO: 1.5 g of benzoyl peroxide (manufactured by NOF Corporation) is dissolved in 100 g of polyethylene glycol dimethacrylate (manufactured by Hitachi Chemical Co., Ltd.) and added to 2,000 g of water in which 1% by mass SDS is dissolved. Dispersion 2 was obtained by dispersing for 30 minutes with a high-speed homogenizer.

The 1-chlorododecane-absorbing polystyrene particle dispersion was added to the dispersion 2, and the mixture was stirred for 16 hours at 50 rpm and room temperature to obtain a dispersion 3 in which polyethylene glycol dimethacrylate was absorbed into the polystyrene particles.

The dispersion 3 was reacted by stirring at 50 rpm and 80 ° C. for 24 hours to prepare an acrylic resin sphere dispersion having a uniform particle size. The acrylic resin sphere dispersion was filtered, washed with pure water, further filtered, and dried to obtain an acrylic resin sphere powder.

-Particle size-
When the number average particle size of the acrylic resin spheres was determined in the same manner as in Example 1, it was 3.2 μm. The CV value (variation coefficient) of the particles was 2.6%.

―Compressive fracture load value―
When the compression failure load value of the acrylic resin sphere was measured in the same manner as in Example 1, it was not broken by compression of 1 g.

―10% compressive strength―
The 10% compressive deformation strength of the acrylic resin sphere was 600 MPa when measured by the same method as in Example 1 with a test load of 10 g.

―Compression recovery rate―
When the compression recovery rate of the acrylic resin spheres was measured in the same manner as in Example 1, the compression recovery rate of the acrylic resin spheres was 45%.

―Iodine doping―
2 g of the acrylic resin spheres were charged into a 50 ml water / ethanol (water: ethanol = 1: 1 (V / V)) mixed solution in which 2 mM iodine and 4 mM potassium iodide were dissolved. At this time, the aggregates of the large resin fine particles were previously crushed. While the solution kept at 50 ° C. was irradiated with ultrasonic waves for 1 hour, iodine was introduced into the fine particles to obtain an acrylic resin spherical iodine complex.

<Secondary dope process>
The acrylic resin spherical iodine complex obtained in the primary dope process was washed with a 0.2% by mass aqueous sodium thiosulfate solution. The iodine solution adhering to the surface of the acrylic resin sphere iodine complex is put into 100 mL of 0.15 mass% ammonium chloride aqueous solution containing 1 mM palladium chloride, and the iodine and palladium ions are reacted at 80 ° C. for 1 hour. To obtain a palladium iodide composite.

<Reduction process>
The palladium iodide composite obtained in the secondary doping step was reduced to metallic palladium with a 0.025% by mass aqueous sodium borohydride solution to obtain acrylic acid resin spheres with palladium deposited on the surface.

<Electroless plating process>
Acrylic resin spheres with palladium deposited on the surface obtained in the reduction step were dissolved in 0.05 mol / L nickel nitrate in water / ethanol (water: ethanol = 1: 1 (V / V)). The nickel plating film layer was formed under the reaction conditions of 60 ° C. and 24 hours to 120 hours. By observing from these particles under a high-magnification optical microscope using transmitted light, the particles appearing black were selected as fine particles that had been plated, and conductive particles for ACF were obtained.

<Compressive conductivity test>
-Method-
With respect to the conductive particles for ACF, the surface resistance value was measured by the compression conductivity test shown in FIG.

-result-
The electroconductive particles after electroless plating obtained in Example 2 did not break the plating film layer even at a deformation rate of 70%. Since the base polymer particles also have good compression characteristics, and the plating film layer also has good compression characteristics, it is possible to maintain a low electric resistance value of 15Ω even at a deformation rate of 70%. I understood. This is considered to be because the nickel plating film was firmly fixed to the base polymer particles by improving the anchoring effect by interspersing the metal fine particles (palladium) on the surface of the base polymer particles.

This particle was subjected to a 10-point conductive compression test, but all the particles maintained a low resistance value until they were broken. A conductive compression test was conducted on 10 conductive particles after electroless plating obtained in Example 2. It was confirmed that a low resistance value of 15Ω was maintained until any particle was destroyed. It was also confirmed that the compressive load when the conductive particles were destroyed was 5.0 gf. When each particle was observed with an electron microscope, it was confirmed that a very smooth plating film was formed. This smooth plating film seems to have allowed the resistance value to be 15Ω without any fluctuation in any particle.

The conductive particles with plating layer of Example 2 were added to an epoxy resin and a curing agent and formed into a film by extrusion molding to obtain an anisotropic conductive film. This anisotropic conductive film maintained good conductivity over a long period of time and exhibited high compression reliability. As is apparent from the above, the etching process is not performed in the production of the conductive particles for the conductive spacer, but the compressive properties of the conductive particles are not impaired.

[Example 3: conductive particles for conductive paste]
The following treatment was performed using commercially available crosslinked high-density polyethylene particles, flow beads HE3040 (average particle diameter 11 μm) manufactured by Sumitomo Seika Co., Ltd.
―Iodine doping―
3 g of the polyethylene resin spheres were charged into 20 mL of a 50% by mass ethanol aqueous solution (iodine-ammonium iodide solution) in which 1 mM iodine and 10 mM ammonium iodide were dissolved.The iodine-ammonium iodide solution maintained at 10 ° C. And immersed for 20 minutes to obtain a polyethylene resin spherical iodine composite.

<Secondary dope process>
The polyethylene resin spherical iodine complex obtained in the primary dope process was washed with a 50% by mass aqueous ethanol solution while filtering. The iodine complex formed inside or on the surface of the polyethylene resin sphere was immersed in a 10 mM chloroauric acid-50 mass% ethanol aqueous solution for 2 days to react with the metal species to obtain a gold iodide composite.

<Reduction process>
The gold iodide composite obtained in the secondary doping step is washed with 50% by mass ethanol, and further heated to 160 ° C. in the atmosphere for 72 hours to be reduced to metal, thereby doping gold fine particles. Fine particles were obtained.

<Electroless plating process>
The gold fine particle dope particles obtained in the reduction step were put into a mixed solution of water / ethanol (water: ethanol = 1: 1 (V / V)) in which 0.05M silver nitrate was dissolved, A silver plating film layer was formed under reaction conditions for 24 hours.

The particles for anisotropic conductive paste obtained in the above steps were subjected to a compression test under the same conditions as in Example 2.

Even when the deformation rate was 70% compression, the plated film layer was not destroyed, and the polymer particles showed good compression properties. In a ten-point conductive compression test, all particles maintained a low resistance value of 15Ω.

The conductive particles provided with the plating layer of the present invention were added to and mixed with a styrene ethylene butylene elastomer (Tuftec M-1913 manufactured by Asahi Kasei Chemicals Co., Ltd.) dissolved in xylene, then screen-printed and dried to conduct conductive connection. This conductive paste maintained good conductivity over a long period of time and exhibited high compression reliability.

[Example 4: conductive particles for conductive spacer]
Conductive particles for conductive spacers were produced under the same conditions as in Example 1, except that iodine in the primary doping step was 100 mM, potassium iodide was 200 mM, and palladium chloride in the secondary doping step was changed to 1 mM nickel nitrate.

The conductive particles for the conductive spacer obtained in Example 4 retain the good compression characteristics of the acrylic resin that is the base polymer particle, and also have excellent conductivity due to the silver plating film formed on the particle surface. It was found to have sex.

Furthermore, when the conductive particles obtained in Example 4 were observed with an electron microscope, a very smooth surface could be observed. The measurement of the minimum resistance value and the measurement of the breakdown point were performed by preparing 10 conductive particles according to Example 1. However, all the conductive particles showed variations in the minimum resistance value and the numerical value of the breakdown point. I couldn't.

When the electroconductive particle of Example 1 was used as an electroconductive spacer, it maintained favorable electroconductivity over a long period of time, and exhibited high compression reliability.

[Example 5]
In the primary dope step of the method for producing conductive particles of Example 2, the composition of “iodine-ammonium iodide solution” was 50 ml water / ethanol (water: ethanol) in which 0.5 M iodine and 2 M potassium iodide were dissolved. = 1: 1 (V / V)) A mixed solution was prepared, and a palladium iodide composite was produced under the same conditions as in Example 2 except that the palladium chloride solution was changed to 6 mM.

About the palladium iodide composite which finished the reduction process of Example 2, and the palladium iodide composite which finished the reduction process of Example 5, it reduced by the method similar to Example 2, and the metal fine particle on the surface of a base polymer particle Was precipitated. About the base polymer particle of Example 2 and Example 5, the base polymer particle was observed with the transmission electron microscope (TEM) and the scanning electron microscope (SEM). Photographs taken are shown in FIGS.

As apparent from FIGS. 4 and 5, according to the production method of Example 2, it can be seen that very few palladium metal fine particles are deposited and scattered on the surface of the base polymer particles. As described above (Example 2), the compression property and conductivity of the conductive particles provided with a plating film on the base polymer particles on which a small amount of palladium metal fine particles are deposited are superior to those of the conventional example. This seems to be due to the fact that very few palladium metal fine particles are deposited on the surface of the base polymer particles. That is, in the present invention, it is presumed that metal fine particles are scattered on the surface of the base polymer particles, thereby forming an uneven shape and enhancing the anchoring effect.

On the other hand, as apparent from FIGS. 3 and 4, in the production method of Example 5, a large amount of palladium metal fine particles are deposited on the surface of the base polymer particles. Surface shape distortion is also observed. A plating film was applied to the polymer substrate particles on which a large amount of palladium metal fine particles were deposited in the same manner as in Example 2. When the surface resistance value was measured, it was 2.0 × 10 ² Ω on average. Due to the distorted surface shape, the resistance value of each particle varied. As for compression characteristics, the same test method as described above was performed. As a result, the plating film layer was destroyed at a deformation rate of 55%.

DESCRIPTION OF SYMBOLS 1 Indenter 2 Conductive particle 3 Metal sample stand 4 Resistance measuring device

Claims (4)

A primary doping step of adjusting the polymer / iodine complex by doping iodine with respect to the base polymer particles;
A secondary doping step of preparing a metal iodide composite by reacting a metal species with the polymer / iodine composite;
A reduction step of reducing the metal iodide composite to metal fine particles, and interspersing metal fine particles serving as nuclei of the plating film on the surface of the base polymer;
A method for producing conductive particles, comprising: an electroless plating step in which a plating film is grown using the metal scattered on the surface of the base polymer particles obtained in the reduction step as a nucleus. The method for producing conductive particles according to claim 1, wherein the primary doping step is a step of immersing the base polymer particles in a solution containing 5 × 10 ^{−6 to} 5 × 10 ⁻³ N simple iodine. The method for producing conductive particles according to claim 1, wherein the secondary doping step is a step of immersing the polymer / iodine complex in a solution containing a metal species of 5 × 10 ^{−6 to} 5 × 10 ⁻³ N. The electroconductive particle which is manufactured by the method in any one of Claims 1-3 and whose surface resistance value is 5-10 < ² > (omega | ohm).