JP2003045230A - Synthetic resin particulate, conductive particulate and anisotropy conductive material composite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a synthetic resin particulate that does not bring about conduction failure and is superior in stability with the passage of time as a core material of a conductive particulate. SOLUTION: A synthetic resin particulate which is useful as a core material of a conductive particulate is provided. This synthetic resin particulate has an initial elasticity modulus (M10 ) of 0.1-10 kgf/mm<2> (0.98-98 N/mm<2> ) and a crushing strength degradation ratio of 25% or les (165 deg.C, before and after one hour heat treatment). When such synthetic resin particulate is used as a core material of the conductive particulate, a conductive particulate that does not bring about conduction failure and is superior in stability with the passage of time can be obtained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a synthetic resin fine particle,
The present invention relates to conductive fine particles in which a conductive layer is formed on the surface of such synthetic resin fine particles, and an anisotropic conductive material composition containing the conductive fine particles.

[0002]

2. Description of the Related Art An anisotropic conductive material composition which conducts only in the compression direction is known. More specifically, the anisotropic conductive material composition is a binder composition in the form of an adhesive or a film in which fine particles having a surface coated with a conductive material are kneaded and dispersed.

For such an anisotropic conductive material composition, synthetic resin fine particles coated with a conductive material are used. Such synthetic resin fine particles act as a core material of a conductive material.

Conductive pastes have been known for a long time. Such a conductive paste is a material in which a large amount of conductive powder such as carbon or silver is kneaded in a binder such as an oily substance or an adhesive. Such a conductive paste is often used in cases such as temporary provision of electrical continuity at electrode joints.

Apart from this, anisotropic conductive materials have also been used in recent years. In such an anisotropic conductive material, the particle size of the conductive powder is made uniform, and each particle is dispersed independently in the binder. The material is compressed by being sandwiched between a pair of minute electrodes, and only the compressed portion becomes a single particle layer and comes into contact with both electrodes to establish electrical conduction between them.

Such an anisotropic conductive material is used between a pair of electrode plates arranged in a large number of small strips. Therefore, a particle larger than the distance between other adjacent electrode pairs causes a short circuit. For this reason, the diameter of the fine particles to be used must be small to some extent, and the particle diameter must be uniform so that all the electrode pairs can be stably conducted.

The fine particles having a uniform particle size are used, for example, to keep the distance between transparent substrates of a liquid crystal panel constant. Such fine particles are uniform fine particles for spacers made of silica or synthetic resin.

Metal plating may be applied to the surfaces of various fine particles. Various techniques have been developed for such metal plating techniques. The metal-plated synthetic resin fine particles are used as an anisotropic conductive material.

Therefore, the core fine particles for anisotropically conductive materials that have been used conventionally use the in-plane spacers of the liquid crystal panel as they are for keeping the distance between the transparent substrates of the liquid crystal panel constant.

The liquid crystal panel spacer is a material that requires a certain degree of high hardness. For this reason, particularly when hard particles such as silica are plated with metal and used as they are as an anisotropic conductive material, the following problems occur. The electrode surface and the metal-plated fine particles are point contacts, and the contact area is small.In addition, there are uncertain factors such as uneven contact due to the unevenness of the electrode surface spacing, uneven pressure during compression, and uneven binder viscosity. Was often caused.

At present, spacers for liquid crystal panels made of a crosslinked divinylbenzene resin or a crosslinked benzoguanamine resin are used as they are as a raw material for surface plating. The anisotropic conductive fine particles have a mean diameter of 80 to 90 in order to ensure conduction.
The electrode pair is compressed / constricted up to about%.

From an electric circuit board assembler or a liquid crystal display panel maker using an anisotropic conductive material, there is a demand for softening the core material fine particles to increase the contact area of the conductive fine particles so as to prevent contact failure. It's been around for a long time.

The following are known in the art relating to metal-plated fine particles. (1) Japanese Patent Application Laid-Open No. 61-277105 describes conductive particles having poly (pentaerythritol tetraacrylate / divinylbenzene) -based synthetic resin particles as a core material and a surface coated with a conductive material.

(2) In order to soften the core fine particles,
Japanese Patent Publication No. 5-19241 proposes a thermoplastic resin or a styrene resin having a reduced degree of crosslinking.

(3) Japanese Patent Application Laid-Open No. 12-319309 proposes fine particles of synthetic resin containing polyalkylene glycol di (meth) acrylate as a main raw material as core particles of conductive fine particles.

[0016]

The present inventor has a problem that when the above-mentioned resin-based spacers are used as conductive fine particles, or when metal-plated synthetic resin fine particles are used, there is an unbearable problem in terms of conduction failure and stability over time. Found.

An object of the present invention is to obtain, as a core material of conductive fine particles, synthetic resin fine particles which do not cause conduction failure and are excellent in stability over time.

[0018]

The present invention relates to synthetic resin fine particles used as a core material for conductive fine particles, wherein the synthetic resin fine particles are 0.98 to 98 N / mm ² (0.1 to 10).
kgf / mm ² the conversion formula 1kgf ^/ mm 2 = 9.806
It was converted by 65 N / mm ² . same as below. ) Initial modulus (M ₁₀ ) and crushing strength decrease rate of 25% or less (16
The present invention relates to synthetic resin fine particles characterized by having a heat treatment at 5 ° C. for 1 hour). The present invention also relates to conductive fine particles in which a conductive layer is formed on the surface of the synthetic resin fine particles, and an anisotropic conductive material composition containing the conductive fine particles.

The inventors of the present invention made various fine particles as prototypes and studied in order to obtain conductive fine particles having no conduction failure.

As a result, the inventors of the present invention have found that when the resin-based spacer is used as the conductive fine particles, the resin-based spacer has a high hardness as a resin product, and the conductive fine particles after plating are hard and are not easily crushed. We have found problems such as frequent occurrence of conduction defects.

According to the research conducted by the present inventor, in order to avoid such poor conduction, theoretically, it is sufficient to mix 0.1 to 1% by weight of conductive fine particles in the binder, and sometimes 5 to 20. It was found that a large amount of conductive particles, such as weight%, needs to be mixed. However, the use of a large amount of conductive fine particles is likely to cause another problem such as a short circuit between particles.

The inventor of the present invention has disclosed in Japanese Patent Laid-Open No. 61-2771.
The technique described in Japanese Patent Publication No. 05 was additionally tested. As a result, when the initial elastic modulus M ₁₀ of the fine particles before plating obtained by this technique was measured, the hardness was as high as 23 kgf (230 N) / mm ^2, and when this was processed and used as an anisotropic conductive adhesive, a durability test was performed. There were many poor contacts.

According to the research conducted by the present inventor, the cause is that the core fine particles have a high hardness and the amount of compressive deformation is 10 of the average diameter.
There was no choice but to keep it below%. Conductive fine particles distributed on the smaller particle diameter side than the average particle diameter do not come into contact with each other, or
Contact stress is reduced. Therefore, in the durability test and the like, the conductive fine particles cannot follow the expansion and contraction deformation of the binder, resulting in poor contact.

In the technique described in Japanese Patent Publication No. 5-19241, a thermoplastic resin and a styrene resin having a reduced crosslink density have been proposed, but in this case also, the long-term reliability of conduction is remarkably inferior and is put to practical use. Was difficult.

The cause of this is that the fine particles are thermally melted or plastically deformed during the heat compression used for the heat curing of the binder adhesive and the melt curing of the film. After the temperature of the conductive fine particles is returned to room temperature, the contact between the electrode plate and the conductive fine particles becomes incomplete. That is, in this case, it was considered that the repulsive stress to the electrode due to the compression recovery of the fine particles was none or insufficient.

In the technique described in Japanese Patent Application Laid-Open No. 12-319309, the conductive fine particles are too soft to break through the binder film by applying pressure. Probably the conductivity is not improved when mixed with the adhesive. However, when hot-compressed under high pressure, problems such as breakage of core fine particles occurred.

Further, the ether bond of polyalkylene glycol was easily oxidized, and satisfactory results were not obtained in the reliability test.

Based on such knowledge, the present inventor further produced various fine particles in order to obtain optimum core fine particles capable of exhibiting stable conductivity for a long term without causing conduction failure. investigated.

As a result, the present inventor can compress and deform the conductive material-coated fine particles when sandwiched by a pair of electrodes so as to have a wide contact area. The average diameter is 1 to 100 μm.
The uniform synthetic resin fine particles in the range of m were found.

The present invention is based on the fact that synthetic resin fine particles having optimum physical property limit values as core material fine particles were obtained from an acrylic rubber type material. In the present invention, the synthetic resin fine particles have high physical and chemical heat resistance and stably exhibit rubber elastic compression recovery.

[0031] In the present invention, the synthetic resin particles initial modulus _{M 10} is, 0.98N / mm ² or more and 98 N / mm ² or less. Within such a range, the obtained conductive fine particles can be compressed and brought into stable contact with the upper and lower electrodes, and the problem of poor conduction can be solved.

That is, 10 kgf (98 N) / mm ²
Fine particles having a high elastic modulus of more than 5 are too hard to increase the degree of compression, resulting in poor conduction during the durability test. Also, 0.1k
Fine particles of less than gf (0.98 N) / mm ² are too soft, the compression pressure becomes small, the coating film of the binder existing between the electrode plate and the conductive particles is not easily broken, and conduction cannot be obtained from the beginning. .

In the present invention, the synthetic resin fine particles are 16
25% reduction in crushing strength before and after heat treatment at 5 ° C for 1 hour
It is the following. The core material fine particles having a small strength change have no problem due to thermal deterioration.

The large decrease in crushing strength after heat treatment means that the molecular chains of the crosslinked polymer are significantly cut. In this case, not only immediately after the binder curing treatment, but also the stability of the electrically connected product with time is deteriorated and the reliability is remarkably poor.

According to the present invention, the fine particles of synthetic resin are 0.1
-10 kgf (0.98-98N) / mm ² initial elastic modulus (M ₁₀ ) and 25% or less crushing strength decrease rate (165
By using such synthetic resin fine particles as the core material of the conductive fine particles, it is possible to obtain conductive fine particles which do not cause poor conduction and are excellent in stability over time. .

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described. (1) Each Parameter of Synthetic Resin Fine Particles Here, the definitions of the crushing strength, the initial elastic modulus M ₁₀ and the compression recovery rate in the present invention will be described in detail.

(1-1) Crushing strength First, the crushing strength was calculated according to Hiramatsu's formula [Nippon Journal 81, 1024,
(1965)]. According to Hiramatsu, the conversion from the compressive load of the granular material to the tensile strength S ₀ is: S ₀ = 2.8P ₀ / πd ² [wherein S ₀ : tensile strength (kgf / mm ² ),
P ₀ : load (kgf), d: particle diameter (mm)]. In the present invention, the crushing strength is given by S ₀ in the above formula. That is, the load P required for destruction per one fine particle
_It is determined by measuring ₀ (kgf) and substituting it in the above equation.

(1-2) Initial Elastic Modulus Next, the initial elastic modulus M ₁₀ is obtained. In the tensile strength S ₀ of the above formula, the stress when 10% of the particle size is displaced at 25 ° C. is S, and the load (compressive stress) when 10% of the particle size is displaced at the load P ₀ of the above formula. Let P be P, the above equation becomes S = 2.8P / πd ² .

1 of the particle size at 25 ° C. according to the present invention
Since the elastic modulus M _{10 at} 0% initial displacement is converted to 100% displacement, the above formula is multiplied by 10 and is therefore represented by the following formula. M ₁₀ = 10S That is, M ₁₀ = 28P / πd ² [wherein, P: stress at initial 10% compression displacement at 25 ° C. (kgf), d: particle diameter (mm)].

(1-3) Compression recovery rate The compression recovery rate is from 0 gf to 1 per particle at a constant speed.
It is compressed to gf, 1 g displacement is measured, and it is returned to 0 gf again to obtain the residual strain, which is taken as the ratio of the difference between the 1 gf displacement and the residual strain to the 1 gf displacement.

(2) Initial Modulus of Elasticity Conventionally, the elastic modulus has been used as an index of the hardness of a material. Generally, in the case of soft material fine particles, there is some variation in the measuring method, but the softness can be measured also by the elastic modulus which is a mechanical property. In the present invention, the range of softness of the synthetic resin fine particles can be specified also by the elastic modulus.

The synthetic resin fine particles of the present invention have an initial elastic modulus M.
₁₀ is 0.1 kgf (0.
98 N) / mm ² or more, 10 kgf (98 N) / mm ²
The range must be maintained. The change rate of the initial elastic modulus before and after the heat treatment may be practically used as long as it is within the range of about 0.3 to 2 times before the heat treatment. It is more preferable that the change in the initial elastic modulus before and after the heat treatment is in the range of 0.5 to 1.5 times.

The initial elastic modulus was measured at an initial stress of 0 kgf.
Since the detection is started from (0N) / mm ² , the measurement error is large. In particular, in the case of a soft material having an elastic modulus of 10 kgf (98 N) / mm ² or less, the error is likely to be large, but if the rate of crushing strength change is taken as a representative of the change in physical properties, it is possible to obtain a substantial effect of thermal deterioration. The presence or absence can be detected.

(3) Reduction rate of crushing strength In anisotropic conductive adhesives and anisotropic conductive films, the binder component is mostly thermosetting resin or thermoplastic resin. Therefore, in most cases, the conductive fine particles pass through the heat compression process. Therefore, the core material of the conductive fine particles is required to have heat resistance and compression resistance.

The heat resistance of the synthetic resin fine particles as used herein means
The chemical stability of the core material in the heating and compression process is good, and it may be destroyed in the processes such as heat curing and heat softening of the binder,
That is, no oxidation or thermal decomposition occurs.

The conductive fine particles are often exposed to a high temperature depending on the kind of the binder resin. Since the conductive film is often made of metal, there is no problem. However, the resin fine particles of the core material need to withstand this temperature, and the effect thereof is remarkable in the crushing strength.

As a practical matter, it is difficult to measure the shape and the physical properties under pressure heat, and in the present invention, the heat treatment is performed in a free state, and the change in the mechanical physical properties before and after the heat treatment are measured.

Generally, when conductive fine particles are mixed in the peripheral sealer of the liquid crystal panel, an epoxy adhesive is used as the binder resin. Generally, the heat-curing conditions for the peripheral sealer are 150 to 180 ° C. and 1 to 4 hours.

Further, in the anisotropic conductive film, the thermosetting conditions are 150 to 160 ° C. and 20 seconds, 200 to 230 ° C. and 5 to 10 seconds, which is almost the same as that of the sealer or much higher, and extremely high. Short cure times are applied. The conductive particles need to withstand these thermal histories.

Among the binder curing conditions, the sealer has a slightly lower temperature, but is still much higher than room temperature.
The heating time is several hundred to several thousand times longer than that of the anisotropic conductive film. It is considered that the sealer has a larger influence on the fine particles, based on the damage mainly caused by the oxidative deterioration reaction.

Therefore, in the present invention, a more severe heat treatment condition is set at 165 ° C. for 1 hour in the case of a sealer. If the reduction in crushing strength before and after this heat treatment is at least 25% or less, preferably 20% or less, thermal deterioration of the core material fine particles during this time is not a practical problem.

(4) Compression Recovery Rate Next, it is desirable that the synthetic resin fine particles of the present invention have a compression recovery rate of at least 30% or more, preferably 40% or more. When the compression recovery rate is less than 30%, the crosslinking between the polymers is insufficient, and permanent deformation due to thermal compression tends to occur, which is not preferable.

However, in reality, it is not desired that even a crosslinked polymer is a completely elastic body, and since the relaxation time cannot follow the recovery time of the compression recovery measurement, even if it does not reach 100%, the above-mentioned degree is obtained. The compression recovery rate of is practically no problem.

In this sense, the retention property of the compression recovery rate by heat treatment is also an important physical property. After the conductive fine particles are fixed with a binder between the electrodes by pressure heat, the conductive fine particles should not be plastically deformed to reduce the repulsive stress, and the contact between the electrodes and the conductive fine particles should not be disturbed.

(5) Raw Material of Synthetic Resin Fine Particles In the present invention, the synthetic resin fine particles are 0.1 to 10 kgf.
(0.98 to 98 N) / mm ² initial elastic modulus (M ₁₀ ).
Also, as long as a crushing strength reduction rate of 25% or less (before and after heat treatment at 165 ° C. for 1 hour) can be realized, it can be formed from various raw materials.

(6) Acrylic rubber The synthetic resin fine particles of the present invention can essentially consist of acrylic rubber. However, such acrylic rubber
Different from general acrylic rubber. In a general acrylic rubber, after polymerizing an acrylic monomer into a linear polymer, it is cross-linked with a vulcanizing agent such as amine during or after molding. On the other hand, in the present invention, due to the presence of the bifunctional monomer raw material, the structure becomes a structure which is crosslinked simultaneously with the polymerization. Therefore, the chemical structures of the two crosslinking points are completely different, and the acrylic rubber according to the present invention belongs to the special acrylic rubber.

Particularly in the present invention, such fine particles can be obtained from a crosslinked alkyl acrylate polymer which is an acrylic rubber.

In the present invention, with respect to such a crosslinked acrylic acid ester polymer, the degree of softness has a high correlation with the density, and the density of the synthetic resin fine particles is 1.01 to 1.20.
The range up to g / mL is optimal.

That is, if the density exceeds 1.2 g / mL, it becomes too hard, and the reliability of the conductive fine particles using this is not so different from the conventional fine particles coated with a high hardness conductive material, which is not preferable. Further, when the density is less than 1.01 g / mL, it is not preferable because it is too soft and there is a problem that the water sieving classification method cannot be used in the particle size refining step after suspension polymerization.

Therefore, it is important to set the density of the combination of various raw material monomers in the range of 1.01 to 1.20 g / mL.

The acrylic acid ester crosslinked polymer according to the present invention gives a polymer having resistance to thermal oxidation, and when applied as an anisotropic conductive film or an anisotropic conductive adhesive after being coated with a conductor, it is pressed and heated. The core fine particles are sufficiently reliable and do not deteriorate in the process. That is, even if the fine particles are heated in air at 165 ° C. for 1 hour, the reduction in crushing strength can be maintained at 25% or less.

(6-1) Bifunctional Monomer To obtain such an acrylic acid ester crosslinked polymer, in order to obtain a special acrylic rubber having a lower degree of crosslinking than conventional in-plane spacers for liquid crystal panels, a bifunctional monomer is used. Most preferably, an alkylene diol diacrylate is used as the raw material monomer.

Examples of the alkylenediol diacrylate include 1,2-ethylene glycol diacrylate, 1,3-propylene glycol diacrylate and its isomers, 1,4-butanediol diacrylate and its isomers, 1,6-hexanediol diacrylate and its isomers, 1,7-heptanediol diacrylate and its isomers, 1,8-octanediol diacrylate and its isomers, 1,9-nonanediol diacrylate and its isomers Body, 1,10-decanediol diacrylate and its isomers, 1,11-undecanediol diacrylate and its isomers, 1,12
-Dodecanediol diacrylate and its isomers,
At least one monomer selected from 1,13-tridecanediol diacrylate and its isomers, 1,15-pentadecanediol diacrylate and its isomers, 1,16-hexadecanediol diacrylate and its isomers, and the like is used. be able to. The trifunctional or higher polyfunctional monomer may be used in combination with the following monofunctional monomers or alone, as long as the hardness does not increase excessively and the flexibility is lost.

Instead of the alkyl diacrylate, for example, JP-A-12-309715 and JP-A-12-3.
When polypropylene glycol diacrylate or polytetramethylene glycol diacrylate is used as disclosed in Japanese Patent Publication No. 19309, these ether bonds are easily oxidized and deteriorated, and the crush strength by heating in air at 165 ° C. for 1 hour is increased. The decrease is more than 30%, which is not preferable.

Styrene-based and divinylbenzene-based resins are
It is not preferable because it is easily air-oxidized by light or heat and may cause strength deterioration of 30% or more by heating in air at 165 ° C. for 1 hour. Further, since such a resin is originally a hard resin having a high glass transition point, the initial elastic modulus M ₁₀ at room temperature is ₁₀ kgf (98 N).
/ Mm ² It is difficult to soften below.

(6-2) Alkyl acrylate In the present invention, when 20 to 80% by weight of the bifunctional monomer alkylene diol diacrylate is used as the raw material monomer, alkyl acrylate can be used as the balance of the raw material monomer.

The advantage of using an alkyl acrylate is that the polymer obtained from this is a good raw material which is not air-oxidized by light or heat.

In addition, soft polymers generally have a low glass transition point, and alkyl acrylate polymers can achieve this.

The alkyl acrylate can be contained in an amount of 20 to 80% by weight of the raw material monomer. In the present invention, a crosslinked acrylic rubber material is preferred and for this reason,
The alkyl acrylate that gives the linear polymer should be less than 100% by weight of the raw material monomers.

Further, in order to keep the density at 1.01 g / mL or more, it becomes difficult if this exceeds 80%.

On the contrary, if the bifunctional monomer alone is used, the density of the fine particles of synthetic resin may exceed 1.20 g / mL. By adding alkyl acrylate in an amount of 20% by weight or more of the raw material monomer, the density of the fine particles becomes 1.20 g. /
It can be kept below mL.

Examples of the alkyl acrylate include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate and n-acrylate.
-Butyl, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate and its isomers, 2-ethylhexyl acrylate, n-octyl acrylate and its isomers, n-nonyl acrylate and its At least one alkyl acrylate selected from the group consisting of isomers, n-dodecyl acrylate and its isomers, tridecyl acrylate and its isomers, and the like can be used.

(6-3) Other Monomers In the present invention, a monomer copolymerizable with alkylenediol diacrylate and / or alkyl acrylate can be used as the rest of the alkylene diol diacrylate and alkyl acrylate in the raw material monomer. .
The copolymerizable monomer is naturally used within a range in which the M ₁₀ of the synthetic resin fine particles can maintain 0.1 to ₁₀ kgf / mm ² .

Alkylene diol diacrylate and /
Alternatively, the advantage of using the monomer copolymerizable with the alkyl acrylate is that the heat resistance and the oxidation resistance of the obtained synthetic resin fine particles can be improved.

The monomer copolymerizable with the alkylene diol diacrylate and / or the alkyl acrylate can be used in a proportion of 20% by weight or less of the raw material monomer. The reason for the amount of 20% by weight or less is that, in general, a monomer that imparts heat resistance or oxidation resistance often has a high glass transition point of a polymer composed of itself, and when the copolymerization exceeds 20% by weight of the raw material monomer, This is because the flexibility may be lost.

Alkylene diol diacrylate and /
Or, as the monomer copolymerizable with the alkyl acrylate, methyl methacrylate, ethyl methacrylate,
Propyl methacrylate and its isomers, n-butyl methacrylate and its isomers, amyl methacrylate and its isomers, n-hexyl methacrylate and its isomers, n-heptyl methacrylate and its isomers , N-octyl methacrylate and its isomers, n-nonyl methacrylate and its isomers, n-decane methacrylate and its isomers, n-undecane methacrylate and its isomers, n-methacrylate Dodecane and its isomers, n-tridecane methacrylic acid and its isomers,
At least one monomer selected from the group consisting of ethylene (polycaprolactone) diacrylate and the like can be used.

(6-4) Polar Monomer In the present invention, a polar monomer can be used as the alkylene diol diacrylate alone or as the monomer copolymerizable with the alkylene diol diacrylate and the alkyl acrylate. The advantage of such a polar monomer is that the adhesion between the fine particles of the present invention and the metal coating coating the surface thereof can be increased.

Examples of such polar monomers include (meth) acrylic acid, itaconic acid, maleic acid, fumaric acid, N, N
-Dimethylaminoethyl (meth) acrylate, N, N
-Diethylaminoethyl (meth) acrylate, N, N
-At least one selected from the group consisting of dimethyl (meth) acrylamide and the like can be used.

The polar monomer is one of the raw material monomers.
It can be used in a proportion of up to 20% by weight. 20% by weight
The reason for the following is not preferable because the polar monomer generally has a high glass transition point, and when it is copolymerized to exceed 20%, flexibility is lost. If it is less than 1% by weight, it is difficult to obtain the adhesion to the metal coating described above, which is not preferable.

The ratio is more preferably 2 to 10
It is the weight%, and the above-mentioned adhesion can be sufficiently imparted at such a ratio.

(6-5) Polymerization Initiator In the present invention, as a polymerization initiator for the raw material monomer,
Peroxides such as benzoyl peroxide, lauroyl peroxide and methyl ethyl ketone peroxide, azo compounds such as azobisisobutyronitrile and azobismethylvaleronitrile, and other known substances can be used.

Of these, the azo-based initiators are preferable because they do not bring oxides into the polymer and give a crosslinked acrylic acid ester polymer with little deterioration in physical properties due to heating.

(6-7) Other Additives In addition to these, as additives to the monomer, redox reducing agents for peroxide initiators, polymerization end stabilizers such as octyl mercaptan, lauryl mercaptan, and other known substances are used. be able to.

(6-8) Polymerization method The fine particles of the present invention can be produced by suspension polymerization. As the suspension stabilizer used here, other known substances such as poly (meth) acrylic acid, polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol, partially hydrolyzed polyvinyl alcohol and calcium phosphate can be used.

(7) Conductive Fine Particles In the present invention, a conductive layer can be formed on the surface of the synthetic resin fine particles by using a known conductive material for coating such as metal.

(7-1) Conductive Layer The conductive layer is not particularly limited and can be made of various conductive materials. Thickness is usually 0.001-0.1μ
Since it is very thin as m, it hardly affects the hardness of the conductive fine particles. As a result, the degree of softness of the synthetic resin fine particles has the greatest effect on the anisotropic conductive material processing step and usage environment.

Usually, such a conductive layer can be made of a metal such as nickel or gold. Such a conductive layer can be provided on the surface of the synthetic resin fine particles by various methods such as electrolytic plating, electroless plating and vapor deposition.

(8) Anisotropic Conductive Material Composition In the present invention, conductive fine particles are contained in a binder resin and dispersed to obtain an anisotropic conductive material composition.

(8-1) Binder Resin The binder resin according to the present invention is not particularly limited, and various resins can be used. For example, as the binder resin, an adhesive made of epoxy resin or the like can be used.

(9) Method of measuring physical property values of fine particles Next, the method of measuring various physical property values displayed in the present invention and the measurement conditions will be described. (9-1) A synthetic resin fine particle sample is dispersed in methanol water having a density of 50% by weight, and the dispersion is measured at 25 ° C. by the Wardung's specific gravity bottle method.

(9-2) Crushing strength Using a MCTM-200 type micro compression tester mode 1 manufactured by Shimadzu Corporation, the diameter and breaking strength at 25 ° C. are measured 5 times each and averaged. Compression speed is 0.27gf /
Seconds, surface detection is manually corrected.

In the case of a soft material, the displacement by the automatic surface detection method is manually corrected because an error of several μm occurs at such a high compression speed and the data varies. Since there is little variation in stress, this speed is used for strength measurement.

(9-3) Initial elastic modulus M _{10 In} the soft material test mode 3 of the MCTM-200 type micro compression tester manufactured by Shimadzu Corporation, the diameter and the compressive stress up to 2 gf were measured 5 times at 25 ° C., respectively. Average out. The compression rate is 0.0145 gf / sec, and surface detection can be automatically and stably measured. The calculation method of the initial elastic modulus M ₁₀ is as described above.

(9-4) Compression recovery rate Measured 5 times at 25 ° C. in the load / unload test mode 2 of the MCTM-200 type micro compression tester manufactured by Shimadzu Corporation, and averaged. The compression speed is 0.029 gf / sec and the surface detection is automatic. The ratio of the displacement restored to 0 gf of load with respect to the total displacement by unloading to 0 gf at the same velocity with respect to the displacement compressed from 0 gf to 1 gf at this speed, is expressed as a percentage.

(9-5) Heat treatment The sample was placed in a constant temperature dryer at 165 ° C. and kept in air for 1 hour.
Heat treatment for hours.

(9-6) Particle size About 30,000 fine particles of synthetic resin are measured using a Coulter Counter Multisizer II type measuring instrument manufactured by Beckman Coulter, Inc. and averaged. The measurement can be calibrated using standard particles manufactured by the same company.

(9-7) Thickness of Conductive Layer In electroless plating, 100% of the metal adheres to the synthetic resin fine particles almost uniformly, so the weight of the charged metal, the specific gravity of the metal, the weight of the synthetic resin fine particles, and the specific gravity The thickness can be calculated from the average particle size.

(9-8) Volume resistivity value Stainless steel was fixed tightly to the inner wall of the bottom of a polyethylene cylinder having an inner diameter of 10 mm, 1.5 g of metal-coated fine particles were put in the cylinder, and another portion was added from the top. The stainless steel wire is inserted, and the volume resistivity value between both stainless steel wires is measured with a load of 5 kgf being applied.

(9-9) Conductivity On a polyimide substrate having a thickness of 75 μm, a striped 25 μm thick tin-plated 50 μm wide copper pattern was formed.
The pattern is formed to have a distance of 50 μm. T obtained
On the AB type terminal board, the width of 5 mm on the end side of the stripe,
An anisotropic conductive material having a length of about 20 mm is installed.

Here, 50 transparent conductive materials (indium tin oxide = ITO) were provided with 50 stripe patterns each having a width of 50 μm and a distance of 50 μm, and a width of 30 mm and a length of 30 m.
One end of a glass plate having a size of m × 0.7 mm is superposed so that the patterns overlap each other, and the glass plates are bonded together at a predetermined temperature, pressure and time.

Next, the conductivity between one pattern on the TAB type terminal board and the corresponding pattern on the other glass substrate was measured by the resistance value indicated by the tester, and it was 5Ω or less and both sides of this pattern were measured. Check if there is any leakage and judge pass / fail. All stripes are tested and expressed as a percentage of those that pass.

(9-10) Reliability Test Using a constant temperature and humidity chamber manufactured by Tabai Espec Co., Ltd., 85
Conductivity is measured after 1000 hours of treatment at 85 ° C. and 85% relative humidity. Reliability is expressed as a percentage compared to before treatment.

[0103]

EXAMPLES Next, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. Example 1 5% by weight in a 10 liter separable tank equipped with a stirrer
Polyvinyl alcohol [Gosenol GH-17 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.] 7 kg of water was added, and a monomer: 1,9-
500 g of nonanediol diacrylate [Viscoat # 260 manufactured by Osaka Organic Chemical Industry Co., Ltd.] and 500 g of 2-ethylhexyl acrylate [manufactured by Toagosei Co., Ltd.]
And a polymerization initiator: azobisisobutyronitrile [manufactured by Wako Pure Chemical Industries, Ltd.] 20 g were added.

After vigorous stirring at room temperature in the presence of air, a reflux condenser was attached, the mixture was slowly stirred while introducing nitrogen gas, and the external temperature was kept constant at 65 ° C. to carry out polymerization for 16 hours. After that, it was washed with hot water, and then classified by water sieving to give an average particle size of
Fine particles having a size of 2 μm and a standard deviation of 0.27 μm were obtained.

10 g of the obtained fine particles were put into 50% by weight sulfuric acid at 30 ° C., and the mixture was subjected to etching treatment for 2 hours while stirring, filtered and washed, and sensitized in a 0.1% by weight stannous chloride aqueous solution. , Filtered and washed.

Next, the palladium ions of the catalyst were trapped on the surface of the particles in a 0.01% by volume aqueous hydrochloric acid solution containing 0.01% by weight of palladium chloride, filtered, and then filtered at 0.1%.
It was dipped in an aqueous solution of sodium hypophosphite at a weight percentage to deposit palladium on the surface of the fine particles.

The fine particles obtained were stirred and dispersed in a 1% by weight aqueous sodium malate solution at 65 ° C. Here, an aqueous solution obtained by dissolving 17.92 g of nickel sulfate in 80 mL of water and an aqueous solution obtained by dissolving 18.1 g of sodium hypophosphite and 9.52 g of sodium hydroxide in 80 mL of water,
At the same time, it was gradually added over 90 minutes, and stirring was continued until the generation of hydrogen gas was completed.

After that, it was thoroughly washed with water by filtration and dried overnight at 80 ° C. to obtain nickel electroless plated particles. The average particle diameter of the nickel-plated particles was calculated to be 6.35 μm from the weight of the deposited nickel. The physical property values of the fine particles were measured before and after electroless plating, and the results are summarized in Table 1.

The density of the obtained synthetic resin fine particles is 1.04.
2g / mL, crushing strength changes only 6 by heat treatment
%, M ₁₀ was 0.3 kgf (2.9 N) / mm ² , which is a preferable physical property, and was conductive fine particles having good heat resistance even after plating.

Example 2 10 g of the nickel-plated fine particles obtained in Example 1 was used as an aqueous solution containing 1% by weight of EDTA-4Na, 1% by weight of 2Na citrate and 0.3% by weight of potassium gold cyanide.
It was put into 0 mL with stirring and heated to 60 ° C.

Thereafter, 1% by weight of EDTA-was added to this solution.
Aqueous solution containing 4Na and 1% by weight of 2Na citrate 50
mL and 50 mL of an aqueous solution containing 3% by weight potassium borohydride and 6% by weight sodium hydroxide were gradually added simultaneously over about 30 minutes.

After continuing stirring and heating until hydrogen gas was not generated, it was thoroughly washed with water, filtered, and dried at 80 ° C. overnight.
Gold plated particles were obtained. The average particle size of the gold-plated particles was calculated to be 6.40 μm from the weight of the deposited gold.

The measurement results of the physical properties are summarized in Table 1. As can be seen from these results, the heat resistance after the gold plating process was also good.

Example 3 In the same manner as in Example 1, except that the amount of the monomer used in Example 1 was changed to 1000 g of 1,9-nonanediol diacrylate [Biscoat # 260, manufactured by Osaka Organic Chemical Industry Co., Ltd.]. Synthetic resin fine particles having an average particle diameter of 6.0 μm and a standard deviation of 0.25 μm were obtained.

Nickel plated particles were produced from 10 g of the particles in the same manner as in Example 1, and immediately in the same manner as in Example 2, gold plated particles having an average particle size of 6.2 μm were obtained. The measurement results of the physical property values are summarized in Table 1.

The present fine particles show high strength at the stage of the initial synthetic resin fine particles, only 3% by heat treatment, nickel and gold plating from the untreated synthetic resin fine particles before and after heat treatment at 16%, even after heat treatment. The crushing strength did not deteriorate even during the treatment, and extremely good conductive fine particles were obtained.

Example 4 In Example 1, 500 g of 1,9-nonanediol diacrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., Viscoat # 260) and 500 g of 2-ethylhexyl acrylate (manufactured by Toagosei Co., Ltd.) were used. Example 1 except that the amount of methacrylic acid (reagent manufactured by Wako Pure Chemical Industries, Ltd.) was changed to 50 g of methacrylic acid.
Similarly to the above, the average particle size is 6.0 μm, and the standard deviation is 0.26.
Micron particles were produced.

From 10 g of these particles, instead of etching with sulfuric acid in the nickel plating step of Example 1, 3 of surfactant "Clean Ace" (manufactured by Showa Tsusho Co., Ltd.) was used.
Except for performing the hydrophilic treatment with 100 mL of the double dilution,
Nickel plated particles were produced in the same manner as in Example 1,
Immediately, in the same manner as in Example 2, gold-plated particles having an average particle size of 6.2 μm were obtained.

The results of measurement of physical properties are summarized in Table 1. This fine particle did not undergo sulfuric acid etching by copolymerizing a carboxylic acid monomer (methacrylic acid) for the purpose of improving the adhesion between the resin fine particle surface and the metal layer. From the viewpoint of treated synthetic resin particles, only 5. After nickel and gold plating and before heat treatment.
The crushing strength was 6% and the conductive fine particles were good.

Example 5 In Example 1, 600 g of 1,6-hexanediol diacrylate and 4 g of n-butyl acrylate were used as monomers.
In the same manner as in Example 1 except that the amount was changed to 00 g, fine particles having an average particle size of 6.0 μm and a standard deviation of 0.24 μm were produced,
The same as in Example 1 and Example 2, with an average particle size of 6.2 μm.
m gold-plated particles were obtained.

The measurement results of the physical properties are summarized in Table 1. This fine particle is also only 5% by heat treatment, and after nickel and gold plating from the viewpoint of untreated synthetic resin fine particle, before heat treatment 20
% Deterioration of the strength and good conductive fine particles.

Example 6 In the same manner as in Example 1, except that the amount of the monomer used in Example 1 was changed to 1000 g of 1,6-hexanediol diacrylate [Biscoat # 230, manufactured by Osaka Organic Chemical Industry Co., Ltd.]. Average particle size 6.8 μm, standard deviation 0.28 μm
Of the microparticles of Example 1 were prepared in the same manner as in Example 1 and Example 2,
Gold-plated particles having an average particle size of 6.95 μm were obtained. The measurement results of the physical properties are summarized in Table 2.

Example 7 2% by weight of the gold-plated fine particles having an average of 6.2 μm obtained in Example 4 and 2% by weight of spherical silica having a diameter of 5.0 μm were mixed with an epoxy adhesive (Structbond XN manufactured by Mitsui Chemicals, Inc.). −
21-S) and mixed well and dispersed well to produce an anisotropic conductive adhesive. 165 ° C. of this anisotropic conductive adhesive, 1
The conductivity after curing at 0 kgf / cm ² and 1 hour was 100% before and after the reliability test.

Example 8 4 parts by weight of gold-plated fine particles having an average size of 6.2 μm obtained in Example 4 were mixed with 40 parts of a phenoxy resin (YP50 manufactured by Tohto Kasei Co., Ltd.).
Parts by weight, epoxy resin (made by Yuka Shell Epoxy Co., EP
828) 30 parts by weight, 30 parts by weight of an imidazole-based latent curing agent (HX3741 manufactured by Asahi Kasei Corp.), 30 parts by weight of toluene, and 30 parts by weight of ethyl acetate were mixed and kneaded.

This was coated on a release agent surface-treated polyester film so as to have a thickness of 20 μm after drying to prepare an anisotropic conductive film. 170 ℃ of this film, 32
The conductivity after curing at kgf / cm ² and 15 seconds was 100% before and after the reliability test.

Comparative Example 1 In Example 1, 250 g of 1,9-nonanediol diacrylate [Viscoat # 260] manufactured by Osaka Organic Chemical Industry Co., Ltd. and 1-dodecyl acrylate [Osaka Organic Chemical Industry Co., Ltd.] were used as raw material monomers. Made of lauryl acrylate)
A suspension of fine synthetic resin particles was obtained in the same manner as in Example 1 except that the suspension was changed to 750 g.

It was found that this did not sediment even when left at room temperature for several days, and the specific gravity was obviously 1 or less. The mechanical properties were measured using the fine particles obtained by air-drying on filter paper, and the results are shown in Table 2. However, since water sieving could not be performed, no further experiments were conducted.

Comparative Example 2 In Example 1, 500 g of pentaerythritol tetraacrylate [Viscoat # 400 manufactured by Osaka Organic Chemical Industry Co., Ltd.] and 500 g of 55% divinylbenzene (reagent for chemicals manufactured by Wako Pure Chemical Co., Ltd.) were used as raw material monomers. , The polymerization initiator was changed to 20 g of recrystallized benzoyl peroxide, and the polymerization temperature was changed to 8
Synthetic resin fine particles were obtained and classified in the same manner as in Example 1 except that the temperature was changed to 0 ° C., and the average particle diameter was 6.0 μm, standard deviation was 0.1 μm.
Fine particles with a uniform particle size of 28 μm were produced.

In the following plating process, nickel-gold-plated fine particles were produced in the same manner as in Examples 1 and 2. The thickness of the plating layer was 0.1 μm. Various physical properties were measured and are summarized in Table 2. Incidentally, this example is disclosed in JP-A-61-1
Corresponding to Example 1 of Japanese Patent No. 277105, the crushing strength was reduced by 50% from the initial stage of the synthetic resin fine particles only by heat treatment, and the crushing strength was reduced by 53% from the initial fine particles before the heat treatment after plating. It was Further, even after the plating, the crushing strength was decreased by 48% before and after the heat treatment.

[0130]

[Table 1]

[0131]

[Table 2]

From the above results, the synthetic resin fine particles of the present invention are excellent in flexibility and compression recovery property, that is, elasticity, and can endure a thermal process at high temperature, during which the physical properties are deteriorated. rare.

Therefore, the conductive fine particles obtained by coating the surface of the synthetic resin fine particles of the present invention with a conductive substance such as metal are
When applied as a touch panel contact, it exhibits excellent durability due to its flexibility.

The conductive fine particles of the present invention are a core material when kneaded in a binder, processed into an anisotropic conductive material composition, and constricted between a pair of electrodes and heat-bonded. Since the synthetic resin fine particles always maintain the repulsive force against the stenosis, the electrical connection can be maintained semipermanently, and the reliability is very high. This is not only for connecting to transparent conductors such as liquid crystal panels, but instead of lead pollution solder,
It can be applied to ICs and other electronic components mounted on a printed wiring board with high reliability.

[0135]

According to the present invention, the synthetic resin fine particles have a particle size of 0.
An initial elastic modulus (M ₁₀ ) of 1 to ₁₀ kgf (0.98 to 98 N) / mm ² and a crushing strength reduction rate of 25% or less (16
By using such synthetic resin fine particles as the core material of the conductive fine particles, it is possible to obtain conductive fine particles which do not cause poor conduction and are excellent in stability over time. it can.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01B 5/16 H01B 5/16 // C08L 33:06 C08L 33:06 F term (reference) 4F070 AA30 AC06 AE06 AE27 DB03 DC02 DC12 DC13 4J011 AA08 JB08 JB14 JB26 5G301 DA02 DA05 DA10 DA42 5G307 AA02 HA02 HB03 HC01

Claims (8)

[Claims] 1. A synthetic resin fine particle used as a core material for conductive fine particles, wherein the synthetic resin fine particle has an initial elastic modulus (M ₁₀ ) of 0.98 to 98 N / mm ² and a crushing strength reduction rate of 25% or less. (1
Synthetic resin fine particles having a heat treatment of 65 ° C. for 1 hour). 2. The synthetic resin fine particles are 1.01 to 1.
It has a density (25 ° C.) of 20 g / mL, and 1 to 10
The synthetic resin fine particles according to claim 1, which are spherical particles having an average particle diameter of 0 μm. 3. The synthetic resin fine particles according to claim 1, wherein the synthetic resin fine particles are obtained by aqueous radical suspension polymerization of a raw material monomer, and the raw material monomer is made of alkylene diol diacrylate. . 4. The synthetic resin fine particles are obtained by aqueous radical suspension polymerization of a raw material monomer, and the raw material monomer comprises an alkylene diol diacrylate and a polar monomer copolymerizable with the alkylene diol diacrylate. The synthetic resin fine particles according to claim 1 or 2, wherein the raw material monomer contains the polar monomer in an amount of 1 to 20% by weight. 5. The synthetic resin fine particles are obtained by aqueous radical suspension polymerization of a raw material monomer, and the raw material monomer is an alkylene diol diacrylate 80 to
20% by weight and the balance of 20 to 80% by weight of alkyl acrylate are contained.
The synthetic resin fine particles described. 6. The synthetic resin fine particles according to claim 5, wherein the raw material monomer contains 1 to 20% by weight of a polar monomer copolymerizable with alkylene diol diacrylate and alkyl acrylate. 7. A conductive fine particle having a conductive layer formed on the surface of the synthetic resin fine particle, wherein the synthetic resin fine particle is the synthetic resin fine particle according to any one of claims 1 to 6. Conductive fine particles to be. 8. An anisotropic conductive material composition comprising conductive fine particles in a binder resin, wherein the conductive fine particles are the conductive fine particles according to claim 7. Composition.