JP3427967B2 - Metal-coated fine particles and conductive material containing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to conductive materials such as metal-coated fine particles and anisotropic conductive films, conductive paints, conductive inks, conductive adhesives, and electrical contact particles.

[0002]

2. Description of the Related Art Heretofore, as a conductive material such as a conductive paste or a conductive adhesive, a mixture of metal powder such as gold, silver or nickel with a resin paste or a curable resin liquid has been used. However, since the metal powder has a non-uniform particle diameter, it is necessary to mix a large amount of the metal powder, and there are drawbacks such that the metal powder is precipitated during storage and the conductivity is not stable.

In recent years, for example, JP-A-57-49632,
As disclosed in JP-A-60-12603 and JP-A-60-96548, instead of metal powder, glass beads, silica beads, glass fiber chips, synthetic resin fine particles, etc. having a relatively uniform particle diameter or diameter can be used. Fine particles to which electroconductivity has been developed by applying a coating of gold, silver, nickel or the like on the surface of the material have been developed and used.

Among these fine particles, particularly metal-coated synthetic resin fine particles having a uniform particle size are mixed and dispersed in a plastic synthetic resin film or a synthetic resin adhesive to form an anisotropic conductive material which conducts only in the pressure bonding direction. It is used in manufacturing. However, such fine particles have poor adhesion between the particle resin and the metal, and therefore it is necessary to make the synthetic resin fine particles porous or to generate irregularities on the synthetic resin surface by etching so as to have an anchor effect. It was

[0005]

The metal coating layer produced in this manner sometimes peels off due to shear stress or vibration when producing an anisotropically conductive material by kneading with a plastic resin. Further, the metal coating layer may be peeled off by the pressure applied during the conduction treatment.

Further, as described above, when the synthetic resin fine particles are made porous or subjected to an etching treatment which causes oxidative decomposition or hydrolysis, the strength of the synthetic resin fine particles is remarkably lowered,
Alternatively, the particle diameter becomes small, and there arise problems that the particles themselves are broken during the pressure-bonding treatment, or they are not compressed and deformed and then recovered. As a result, the metal coating layer is often peeled off from the synthetic resin particles, resulting in poor conduction.

An object of the present invention is to obtain metal-coated fine particles having high adhesion, which have improved heat resistance and further improved adhesion between the synthetic resin surface and the metal coating layer.

[0008]

SUMMARY OF THE INVENTION The present invention relates to metal-coated fine particles comprising synthetic resin fine particles and a metal layer formed on the surface thereof. In the present invention, at least the surface portion of the synthetic resin fine particles is substantially chain-transferred to a monomer mixture containing an amino group-containing monomer and a polyfunctional monomer.
It is composed of a copolymer obtained by adding an agent and polymerizing.

The present inventors have found that the inclusion of highly polar amino groups in the synthetic resin fine particles significantly improves the adhesion between the synthetic resin surface and the metal coating layer. The synthetic resin fine particles according to the present invention have sufficient adhesiveness to the metal coating layer even if the surface is not subjected to a chemical treatment such as oxidation or hydrolysis. Further, such synthetic resin fine particles are
If the chemical plating treatment is performed under normal conditions or mild conditions, even better adhesion is exhibited.

The metal-coated fine particles of the present invention have improved adhesion to the metal layer, and are excellent in ultrasonic resistance in the washing step after the coating treatment, kneading stability with a plastic resin, and conduction stability by pressure bonding treatment. Further, since the synthetic resin fine particles according to the present invention are less damaged by the chemical plating treatment, it is possible to maintain the compression recovery property in a state equal to or close to that before the plating treatment. Therefore, the metal-coated fine particles of the present invention,
Complete electrical continuity can be maintained semi-permanently without causing damage or permanent crushing deformation due to the crimping process.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The synthetic resin fine particles according to the present invention are a copolymer of a monomer mixture containing an amino group-containing monomer and a polyfunctional monomer. The synthetic resin fine particles can be produced by aqueous suspension polymerization.

The amino group-containing monomer means vinyl pyridine, methyl vinyl pyridine, N, N-dimethylaminostyrene, N, N-diethylaminostyrene, N, N-dibutylaminostyrene, other N, N-dialkylaminostyrene, N, N-dimethylaminoethyl (meth)
Acrylate, N, N-diethylaminoethyl (meth)
Acrylate, N, N-dibutylaminoethyl (meth)
Acrylate, N, N-dimethylaminobutyl (meth)
Acrylate, other N, N-dialkyl-aminoalkyl (meth) acrylate, N-vinylcarbazole, allylamine, N, N-dimethylallylamine,
A compound having an amino group such as N, N-diethylallylamine and a polymerizable unsaturated double bond.

In the present invention, one or more of these amino group-containing monomers are used in an amount of 1 to 30% by weight, preferably 3 to 15% by weight, based on the total monomer mixture. If the content is less than 1% by weight, the adhesion of the metal film will not be improved. on the other hand,
When the content is more than 30% by weight, most of the amino group-containing monomer is dissolved in water as a suspension medium to cause problems such as agglomeration during polymerization and bubbles in the particles, which is not preferable.

The polyfunctional monomer includes ethylene di (meth)
Acrylate, propylene di (meth) acrylate, butylene di (meth) acrylate, hexylene di (meth)
Acrylate, trimethylolethanedi (meth) acrylate, trimethylolethanetri (meth) acrylate, trimethylolpropane di (meth) acrylate,
Trimethylolpropane tri (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol di (meth) acrylate, dipentaerythritol tri (meth) acrylate , Dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, divinylbenzene, di (meth) allyl ether, di (meth) allyl phthalate, tri (meth) allyl Isocyanurate, ditrimethylolpropane tetra (meth) acrylate, tripentaerythritol octa (meth) acrylate, tetrapentaerythritol Ca (meth) acrylate and the like. In the present invention, one or more of these polyfunctional monomers are used in an amount of 5 to 99% by weight, preferably 10 to 97% by weight, based on the total monomer mixture.

Incidentally, these polyfunctional monomers are rarely marketed as pure products, and in most cases, impurities or similar monomers are contained. However, even such a commercially available product can be used in the present invention if it is 50% or more as a display component.

Since the amino group-containing monomer used in the present invention is hydrophilic, the polyfunctional monomer to be mixed is preferably strongly hydrophobic. This is because it is possible to prevent bubbles from being mixed into the particles when the particles are dispersed in an aqueous medium. Examples thereof include divinylbenzene, trimethylolpropane trimethacrylate and the like.

In the present invention, one or more monofunctional monomers may be used in combination with the above two kinds of essential monomers. Monofunctional monomers include methyl (meth) acrylate, (meth)
Ethyl acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, (meth) acrylic acid-t-
Butyl, isobutyl (meth) acrylate, amyl (meth) acrylate, hexyl (meth) acrylate, (meth)
Cyclohexyl acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth)
Stearyl acrylate, benzyl (meth) acrylate,
Cyclohexylmethyl (meth) acrylate, trifluoroethyl (meth) acrylate, pentafluoropropyl (meth) acrylate, styrene, α-methylstyrene, vinyltoluene, vinyl acetate, vinyl chloride, propyl acetate,
(Meth) acrylonitrile, dimethyl maleate, dimethyl fumarate, dimethyl itaconate and the like are included.

If a large amount of monofunctional monomer is contained, the compression recovery of the resulting synthetic resin fine particles will decrease. Therefore, the amount of the monofunctional monomer to be contained is preferably 70% by weight or less in the monomer mixture. In order to obtain even higher compression recovery, 40% by weight or less of a monofunctional monomer is preferable.

The monomer mixture can be polymerized by using a known oil-soluble radical initiator. As the oil-soluble radical initiator, a compound that does not undergo a redox reaction with an amino group, such as azobisisobutyronitrile or azobisvaleronitrile, is used. These oil-soluble radical initiators are added in an amount of 0.1 to 100 parts by weight of the monomer mixture.
~ 5 parts by weight are used.

A chain transfer agent is added to the monomer mixture. As the chain transfer agent, 1-mercaptooctane, 3-mercaptooctane, 1-mercaptodecane, 3-mercaptodecane, 1-mercaptododecane,
There are 3-mercaptododecane, dibutylamine, dioctylamine, N-methylaniline, N-ethylaniline and the like.

Generally, a polymer containing a large amount of polyfunctional monomer components becomes a three-dimensional polymer after polymerization. Particularly in suspension polymerization, it is considered that one molecule of such a polymer becomes one fine particle. Therefore, in general, if the particle size is adjusted, it is not necessary to adjust the molecular weight, and a chain transfer agent is not used. However, when the metal-coated fine particles are required to have heat resistance after the metal-coating treatment or after being incorporated into an electric component, it is preferable to react the polymerization end with a chain transfer agent to terminate the polymerization reaction. The chain transfer agent is used in an amount of 10 parts by weight or less, preferably 0.
05 to 3 parts by weight can be added.

When no chain transfer agent is used, the thermal decomposition starting temperature is around 200 ° C. On the other hand, when 0.1 part by weight of the chain transfer agent is added, the thermal decomposition starting temperature rises to 260 ° C or higher. However, when the chain transfer agent is added in an amount of 10 parts by weight or more, the polymer becomes a cross-linked polymer of a short branched polymer, which not only lowers the strength but also remains in the particles to lower the adhesion of metal plating.

Suspension stabilizers for carrying out aqueous suspension polymerization include gelatin, starch, hydroxyethyl cellulose,
Hydroxymethyl cellulose, carboxymethyl cellulose, polyvinyl pyrrolidone, fully or partially saponified polyvinyl alcohol, polyvinyl alkyl ether, styrene / maleate alternating copolymer, isobutylene / maleate alternating copolymer, poly (meth) acrylate, poly In addition to water-soluble polymers such as (meth) acrylamide, there are sparingly water-soluble inorganic salts such as barium sulfate, calcium sulfate, barium carbonate, calcium carbonate, calcium phosphate, and magnesium carbonate. The stabilizers can be used alone or in combination of two or more.

During the suspension polymerization operation, the pH of the polymerization system is set to 1 in order to prevent the amino group-containing monomer from being eluted in the aqueous medium.
It is desirable to keep the alkalinity at 0 or more. Therefore, the pH can be adjusted by adding a small amount of sodium hydroxide, potassium hydroxide, aqueous ammonia, or the like.

As the polymerization operation, known methods can be used. An aqueous solution in which a predetermined amount of suspension stabilizer is dissolved or dispersed is charged into a condenser and a heating can with a stirrer.
An auxiliary agent such as a polymerization initiator is added to the monomer mixture and dissolved. This solution was placed in a heating can and stirred vigorously.
Disperse into fine particles. Next, these fine particles are heated to polymerize, washed and dried to obtain synthetic resin fine particles.

The obtained synthetic resin fine particles can be directly metal-coated. However, when it is applied to an anisotropic conductive film or an anisotropic conductive adhesive, it is preferable to carry out a classification operation after polymerization to obtain synthetic resin fine particles having a uniform particle size distribution. In such fine particles, the coefficient of variation of particle size distribution, that is, the ratio of standard deviation to the average particle size is 20% or less, preferably 10% or less.

Further, if the particle size distribution of the synthetic resin fine particles as the base material is uniform, agglomerates are less likely to occur in the chemical plating process, and metal-coated particles having good dispersibility of only the primary particles tend to be obtained. is there.

Therefore, when uniform particles are required as described above, classification is carried out by a known means such as a sieving method, a wind method or a water sluice method. The classification may be carried out after the metal coating step, but the stage of the base material, that is, the synthetic resin fine particles is preferable because the apparent specific gravity of the particles does not vary.

The synthetic resin fine particles produced as described above are coated with a metal film by a known method. In the present invention, the group present on the particle surface among the amino groups covalently bonded to the synthetic resin fine particle polymer interacts with the metal, so that the adhesion of the metal is excellent.
Hydrophilization is sufficient. However, etching treatment with a strong alkali may be performed to further improve the adhesion. However, in the case where the polyfunctional (meth) acrylic acid ester is copolymerized, the hydrolysis may proceed so much that the surface may be dissolved and the particle size may be reduced, so that care should be taken.

The particle size of the synthetic resin fine particles used in the present invention is not limited to be uniform or non-uniform depending on the use after metal coating, but is 0.1 to 200.
It is preferably 0 μm. Fine particles of 0.1 μm or less are difficult to handle such as purification, and 2000 μm
Particles having a size larger than m are not preferable because it is difficult to prevent precipitation and particle adhesion by stirring in a wet process during the plating process.

In the present invention, the metal film can be coated using a physical metal vapor deposition method or a chemical electroless plating method. It suffices that the metal has conductivity, and gold, silver, copper, aluminum, chromium, etc. are used in the vapor deposition method, and gold, silver, copper, nickel, etc. are used in the electroless plating method. Two or more layers of these metal films may be coated.

For example, in the electroless plating method, an alkali such as aqueous ammonia is added to a metal salt solution of silver nitrate, silver cyanide, potassium gold cyanide, nickel sulfate or the like, and the synthetic resin fine particles according to the present invention are added thereto. , Sufficiently wet the surface, then add and disperse. Then formalin,
An aqueous solution of glucose, tartaric acid, sodium hypophosphite, borohydride, etc. is gradually added to reduce metal ions and deposit a metal film on the surface of the synthetic resin.

The thickness of the metal film must be 0.02 μm or more. This is to obtain sufficient conductivity as a conductive material. However, if the thickness exceeds 5 μm, the deformation of the synthetic resin particles due to compression cannot be followed and the metal film peels off from the surface, which is not preferable. In the case of flexible synthetic resin particles,
The thickness of the metal film is 0.5 μm so as to follow the compressive deformation.
m or less is preferable.

The metal-coated fine particles obtained in the present invention may be surface-treated with a silane coupling agent, a titanium coupling agent, a metal soap or the like. When a conductive material is produced by such surface treatment, single particles are satisfactorily dispersed in a thermoplastic synthetic resin, a thermosetting synthetic resin, or a photocurable resin that is a matrix, and it is particularly preferable as an anisotropic conductive material.

[0035]

According to the metal-coated fine particles of the present invention, the synthetic
The thermal decomposition temperature of the resin particles can be increased by the chain transfer agent.
And which, has the good adhesion between the synthetic resin particles and the metal film
Therefore , in kneading with a thermoplastic resin, rubber, paint, adhesive or the like, and when the particles are deformed by compression, the metal film is not peeled off and excellent conductivity is obtained. Further, since the synthetic resin fine particles according to the present invention are not subjected to a severe treatment such as etching, the original strength and compression recoverability are almost maintained. Therefore, the metal-coated fine particles of the present invention can exhibit stable electric conductivity.

In the present invention, for the synthetic resin fine particles and the metal-coated fine particles, the initial 10% compression elastic modulus at 20 ° C.,
Breaking strength, compression recovery rate, particle size distribution, metal film peeling degree, electric resistance value, and metal film thickness were measured as follows.

<Break strength at 20 ° C. and initial 10% compressive elastic modulus> As a hardness index of fine particles, Hiramatsu's formula [Nippon Journal 8
1, 1024 (1965)] was used. In the Hiramatsu ceremony,
The breaking strength S _{0 of the} fine particles converted into the tensile strength is shown by the following formula. S ₀ = 2.8Q / πd ² [kgf / mm ² ] (In the formula, Q is the breaking stress [kg when the particles are crushed]
f] and d is the diameter [mm] of the particles. )

FIG. 1 is a graph showing the relationship between the compressive stress applied to the fine particles and the compressive deformation when the fine particles were subjected to a compression tester. The breaking strength Q is the breaking stress when the particles are crushed. As shown in FIG. 1, the fine particles are deformed when pressure is applied, and finally destroyed. By measuring the breaking strength Q of the fine particles and substituting the value into the above equation, the breaking strength S _{0 of the} fine particles can be obtained.

However, the breaking strength S ₀ is not suitable as a hardness index of the fine particles according to the present invention. This is because the breaking strength Q of the fine particles does not accurately reflect the hardness of the fine particles in a normal state. Therefore, in the present invention, the initial 10% compression elastic modulus (hereinafter referred to as “G value”) of the fine particles is used as the hardness index. This G value is calculated based on the compressive stress shown when the fine particles are deformed by 10% of the diameter at 20 ° C.

In FIG. 1, the fine particles are 10% of the diameter (d / 1).
It is indicated by 0. ) Indicates the compressive stress P when deformed. In the present invention, this compressive stress P is detected and substituted into the following equation to be converted into a compressive elastic modulus corresponding to the stress at a deformation rate of 100%. G = 28P / πd ² [kgf / mm ² ] (In the formula, P is the compressive stress [k when the particles are deformed by 10%]
gf] and d is the diameter [mm] of the particle. )

A Shimadzu microcompression tester [MCTM-200 (manufactured by Shimadzu Corporation)] was used to apply a load toward the center of each sample particle scattered on the sample table, and the load as shown in FIG. -The compressive displacement was measured. This operation was repeated for 5 different particles that were observed to be most average in diameter and they were averaged. The measurement temperature is 20
A mode was used in which the temperature was ° C and the compression rate was 0.675 g / sec. The load when the particles were crushed was defined as the breaking strength of the particles.

From the obtained load-compressive displacement result, the load at the initial 10% displacement of the particle diameter was determined. This load was used as the compressive stress P and was substituted into the above formula to calculate the G value at 20 ° C.

<Compression recovery rate> The compression recovery rate is the above-mentioned Shimadzu
It measured using the small compression tester MCTM-200. Figure 2
Shows a displacement-load curve. The vertical axis is load and the horizontal axis is displacement
is there. For one sample particle scattered on the sample table,
After applying a load up to 1 grf in the center direction, the load is 0 gr
Unload up to f. The data during this period is recorded on the displacement-load curve.
Recorded and the displacement from the origin to 1 grf (L₁),
Recovery displacement when unloading to 0 grf (L ₂) Percentage of measured values
Is expressed as a percentage. The compression speed at this time is 0.029g
/ Sec mode was used.

<Measurement of Average Particle Size and Particle Size Distribution> The average particle size was measured using a Coulter Counter ZMC-256 type measuring device manufactured by Coulter Electronics Co., Ltd.
About 30,000 pieces were measured and averaged. At the time of use, it was calibrated using standard particles manufactured by the same company. However, the average particle size is 30
Particles exceeding μm were measured by an optical microscope.

<Peeling Degree of Metal Film> About 5 mg of metal-coated fine particles were put in a test tube, and a sample in a dry state for 0 minutes before treatment was used.
Ultrasonic water layer (Kagaku Kyoeisha, 100V, 70W, 42k
(Hz) for 30 minutes, and a part of each sample is observed with a transmission optical microscope at 600 times. 1,000 or more fine particles were observed in 5 or more visual fields and the number of fine particles in which the metal film was peeled by 50% or more was counted, and the ratio to the total number of observations was measured. Due to variations, ◎ <0.5%, 0.5 ≦ ○ <3%,
Symbols are expressed as 3 ≦ Δ <10% and 10% ≦ ×.

<Electrical resistance value> 1.5 g of metal-coated fine particles were placed in a polyethylene cylinder having an inner diameter of 10 mm, a stainless electrode rod in close contact with the cylinder was inserted, and a volume specific to the electrodes was applied under a load of 5 kg. The resistance value was measured.

<Thickness of Metal Film> In plating, the metal adheres to the 100% synthetic resin fine particles almost uniformly.
The thickness was calculated from the weight of the charged metal, the specific gravity of the metal, the weight of the synthetic resin fine particles, their average particle diameter, and the specific gravity. In the vapor deposition method, it was measured with an electron microscope.

[0048]

EXAMPLES < Reference Example 1> 5% by weight of polyvinyl alcohol [Nippon Gosei Kagaku Co., Ltd.]
GH-17, saponification degree 87%] While vigorously stirring 7 kg of an aqueous solution, divinylbenzene (manufactured by Wako Pure Chemical Industries) 500
g, a mixture containing 450 g of pentaerythritol tetraacrylate (manufactured by Osaka Organic), 50 g of N, N-dimethylaminoethyl methacrylate (manufactured by Mitsubishi Rayon Co., Ltd.) and 20 g of azobisisobutyronitrile was added under air, It was dispersed in fine particles, heated to 70 ° C. under nitrogen, and polymerized for 8 hours. The obtained polymer fine particles were sufficiently washed with water and then classified to obtain an average particle diameter of 6.7 μm.
Synthetic resin fine particles having a standard deviation of 0.30 μm were obtained. The physical properties of the particles were tested, and the results are shown in Table 1.

10 g of the 6.7 μm particles were put into a surfactant solution (“Clean Ace” 3-fold diluted water manufactured by Shoko Tsusho Co., Ltd.), sonicated for 5 minutes, and then filtered.
The mixture was sensitized in a 0.1 wt% stannous chloride aqueous solution, and filtered and washed. Then, in a 0.01% by volume aqueous hydrochloric acid solution to which 0.01% by weight of palladium chloride was added, the catalyst palladium ions were captured on the surface of the particles, and after filtration,
It was immersed in a 0.1 wt% sodium hypophosphite aqueous solution to deposit palladium on the particle surface. This particle is 1
Stir-dispersed in a weight% sodium malate aqueous solution at 65 ° C., and 80 ml of nickel sulfate 17.92 g is dispersed therein.
Aqueous solution dissolved in water and sodium hypophosphite 18.
An aqueous solution prepared by dissolving 1 g and 9.52 g of sodium hydroxide in 80 ml of water was gradually added simultaneously over about 90 minutes, and stirring was continued until generation of hydrogen gas was completed. afterwards,
After thorough filtration and washing with water, it was dried overnight at 80 ° C. to obtain nickel electroless plated particles. The nickel plated particles are
It had an average particle size of 6.9 μm and a standard deviation of 0.41 μm. The physical properties of the particles were measured. The results are summarized in Table 1.

After mixing 5% by weight of nickel-plated particles with an epoxy adhesive and thoroughly kneading, the degree of Ni film peeling was observed with a microscope. As a result, it was completely the same as immediately after plating and the adhesion to Ni particles was good. Met.

Reference Example 2 10 g of the nickel-plated fine particles obtained in Reference Example 1 contained 1% by weight of EDTA-4Na, 1% by weight of citrate-2Na and 0.3% by weight of potassium gold cyanide. Aqueous solution 1
After pouring into 50 ml with stirring and heating to 60 ° C., 50 ml of an aqueous solution containing 1 wt% EDTA-4Na and 1 wt% citrate-2Na and 3 wt% boron hydride were added to this solution. 50 ml of an aqueous solution containing potassium and 6% by weight of sodium hydroxide were gradually added simultaneously over about 30 minutes. The mixture was continuously stirred and heated until hydrogen gas was not generated, washed thoroughly with water, filtered, and dried at 80 ° C. overnight to obtain gold-plated particles. The gold-plated particles had an average particle size of 7.0 μm and a standard deviation of 0.43 μm. The results of measurement of physical properties are summarized in Table 1. The particles were also mixed with the adhesive as in Reference Example 1, but the metal film was not peeled off in the process.

Reference Example 3 In Reference Example 1, the monomers were 100 g of N, N-dimethylaminoethyl methacrylate and 4 of divinylbenzene.
50 g, 1,6-hexamethylene diacrylate (manufactured by Nippon Kayaku Co., Ltd.) were changed to 450 g, and the stirring speed of the polyvinyl alcohol aqueous solution was lowered, and polymerization was carried out in the same manner as in Reference Example 1,
Classified, average particle size 32.2 μm, standard deviation 1.6 μm
Synthetic resin fine particles of The physical properties of these particles were tested and the results are shown in Table 1. From 10 g of these particles, Reference Example 1 and
Gold plating particles were obtained in the same manner as in Reference Example 2. The gold-plated particles had an average particle size of 34.6 μm and a standard deviation of 1.7.
had a μm. The measurement results of various physical properties are summarized in Table 1. The gold-plated particles were mixed with the adhesive as in Reference Example 1, but no peeling was observed.

Reference Example 4 In Reference Example 1, the monomers were N, N-dimethylaminoethyl methacrylate 100 g, acrylate-n-butyl (manufactured by Toagosei) 700 g, and divinylbenzene 200 g.
Changed, except that the stirring speed was further reduced than in Reference Example 2, the participation
In the same manner as considered Example 1, subjected to suspension polymerization, sieved average 230 .mu.m, the synthetic resin particles of the standard deviation 36 .mu.m. The physical properties of these particles were tested and the results are shown in Table 1. Sputtering equipment JF manufactured by JEOL Ltd.
Gold was applied using C-1300 in the presence of argon. The sputtering process was repeated three times by a method of rolling and stirring the particles on the sample stage after 60 seconds of the sputtering process so that gold was attached to the entire surface of the spherical particles as much as possible, and further sputtered. The obtained gold-coated particles had an average particle size of 231 μm and a standard deviation of 36 μm. The metal film was forcibly peeled off by squeezing the gold-coated particles, and the thickness was measured with an electron microscope. The results are collectively shown in Table 1 together with the results of measurement of other physical properties.

Reference Example 5 The gold-plated particles produced in Reference Example 2 were treated with a silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd.), and then 2 parts by weight of epoxy resin (Super C manufactured by Cemedine Co., Ltd.) was added. %
The mixture was mixed, and the curing agent was mixed in the same amount as the main component to produce a thermosetting anisotropic conductive adhesive (conductive material). This conductive material is applied to the tip of a stainless steel plate of 10 mm x 50 mm x 1 mm in a size of about 10 mm x 10 mm x 1 mm, and a stainless steel plate of the same size is brought into contact with the space to make 0.8 mm or more between the stainless steel plates. After hardening by keeping at, the conductivity between the two stainless steel plates was measured with a tester.
No current flowed.

On the other hand, this conductive material was separately applied onto a stainless steel plate of the same type in a size of 10 mm × 10 mm × 0.05 mm, another stainless steel plate was overlaid and pressure-bonded so that the two stainless steel plates did not come into direct contact with each other. It was then cured and measured by a tester to show conductivity.

Comparative Example 1 In Reference Example 1, N, N-dimethylaminoethyl methacrylate and divinylbenzene were not used, but only dipentaerythritol hexaacrylate was used, and azobisisobutyronitrile was used as a polymerization initiator. Similar to Reference Example 1 except that 10 g of benzoyl peroxide was used,
Synthetic resin fine particles having an average particle diameter of 5.1 μm and a standard deviation of 0.22 μm were obtained. This was nickel-plated in the same manner as in Reference Example 1 and gold-plated in the same manner as in Reference Example 2 to obtain metal-coated fine particles. The gold-plated particles had an average particle size of 5.25 μm and a standard deviation of 0.30 μm. Table 1 shows the measurement results of various physical properties of the particles. This example is inferior in peeling resistance to the reference example 1.

Comparative Example 2 In Comparative Example 1, the monomer was divinylbenzene 40.
g, and 960 g of styrene (both manufactured by Wako Pure Chemical Industries, Ltd.), and synthetic resin fine particles having an average particle size of 7.5 μm and a standard deviation of 0.65 μm were obtained in the same manner as in Comparative Example 1. This was treated in the same manner as in Reference <br/> Example 1 and Reference Example 2, to obtain a gold-plated particles. The particles had an average particle size of 7.65 μm and a standard deviation of 0.70 μm, and their characteristic values are shown in Table 1. The fine particles have almost no compression recovery and poor peeling resistance.

[0058]

[Table 1]

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between compressive stress and compressive deformation.

FIG. 2 is a graph showing compression recovery.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-8-319467 (JP, A) JP-A-63-198206 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01B 1/00 H01B 1/22

Claims (8)

(57) [Claims] 1. A metal-coated fine particle comprising synthetic resin fine particles and a metal film formed on the surface thereof, wherein the synthetic resin fine particles are chain-transferred to a monomer mixture containing an amino group-containing monomer and a polyfunctional monomer. Add agent
Characterized in that it comprises a copolymer added and polymerized,
Metal-coated fine particles. 2. The monomer mixture is 1 to 30% by weight.
Of amino group-containing monomer, 5 to 99% by weight of polyfunctional monomer and 70% by weight or less of monofunctional monomer .
10 parts by weight based on 100 parts by weight of the monomer mixture
Parts or less of the chain transfer agent is characterized that you have been added, according to claim 1, wherein the metal-coated particles. 3. The amino group-containing monomer is vinyl pyridine, methyl vinyl pyridine, N, N-dialkyl-
The metal-coated fine particles according to claim 1 or 2, which is one or more kinds of monomers selected from the group consisting of aminoalkyl (meth) acrylate, N-vinylcarbazole, and N, N-dialkylaminostyrene. 4. The metal-coated fine particles according to claim 1, wherein one kind of the polyfunctional monomer is divinylbenzene. 5. The variation coefficient of the synthetic resin fine particles is 20%.
It has the following particle size distributions,
4. The metal-coated fine particles according to any one of 4 above. 6. The metal-coated fine particles are 0.1 to 2000.
2. Having an average particle size of μm.
6. The metal-coated fine particles according to any one of items 5 to 5. 7. The metal-coated fine particles are 0.02-0.5.
The metal-coated fine particles according to any one of claims 1 to 6, comprising the metal film having a thickness of µm. 8. A conductive material containing at least one matrix material selected from the group consisting of a thermoplastic resin, a thermosetting resin, a photocurable synthetic resin, a paint, an ink and an adhesive, and metal-coated fine particles, A conductive material, wherein the metal-coated fine particles are the metal-coated fine particles according to any one of claims 1 to 7.