JP2007012378A - Conductive particulate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide conductive particulates in which individual particles develop sufficient conductivity and in which unevenness in liquid crystal images is not generated when used in the connection between electrodes. <P>SOLUTION: This is the conductive particulates of which a conductive layer is formed at the surface of resin particulates, of which K value defined by a formula (1) is 500 kgf/mm<SP>2</SP>or less at 20°C and of which a recovery rate after compression deformation is 5-25% at 20°C. Here, in the formula (1), F and S are load value (kgf) in 10% compression deformation of the conductive particulates and compression displacement (mm) respectively, and R is the radius (mm) of the conductive particulates. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to conductive fine particles suitably used for connection between fine electrodes in a liquid crystal display element.

In the liquid crystal display element, conductive fine particles in which a metal layer is formed on the surface of resin particles or glass particles are used in order to electrically connect the paired electrodes. As such conductive fine particles, for example, Patent Document 1 discloses one in which the K value, which is a value representing the hardness of a sphere, is in a specific range, and the recovery rate after compression deformation is in a specific range. Has been.
Japanese Examined Patent Publication No. 7-95165

However, in the conventional liquid crystal display element using the conductive fine particles disclosed in Patent Document 1, since the electric resistance of each conductive fine particle is large, in order to achieve a certain level of conductivity, a large number of conductive fine particles Had to be used. The use of such a large number of conductive fine particles is not advantageous in terms of cost, and since the arrangement density of the conductive fine particles is increased, the particles are likely to aggregate to easily cause an electrical short, resulting in a manufacturing yield of the liquid crystal display element. There was also a risk of lowering.
Furthermore, the liquid crystal display element using the conductive fine particles disclosed in Patent Document 1 has a problem that unevenness is likely to occur in the liquid crystal image.

  The present invention has been made in view of the above circumstances, and provides conductive fine particles in which individual particles exhibit sufficient conductivity when used for connection between electrodes and also do not cause unevenness in a liquid crystal image. The task is to do.

  As a result of intensive studies, the present inventor has found that individual conductive fine particles exhibit very high conductivity when sandwiched between electrodes in a state of being deformed at a compression deformation rate of about 30%. In addition, when the conductive fine particles are arranged between the electrodes in such a deformed state in order to develop high conductivity, the recovery rate after compression deformation of the conductive fine particles can be controlled to be low. It has also been found to be important for reducing the unevenness of the present invention, and the present invention has been completed.

（式（１）中、Ｆ、Ｓはそれぞれ導電性微粒子の１０％圧縮変形における荷重値（ｋｇｆ）、圧縮変位（ｍｍ）であり、Ｒは導電性微粒子の半径（ｍｍ）である。）
前記Ｋ値が２０℃において１００〜４５０ｋｇｆ／ｍｍ^２であって、かつ、前記回復率が２０℃において５〜２０％であることが好ましい。
粒径は２．５〜７．５μｍであることが好ましい。
サンプル数３００以上の場合における粒径の標準偏差Ｓと粒径の平均値Ｄ_ａｖとが下記式（２）を満たすことが好ましい。
Ｓ≦Ｄ_ａｖ×０．０５・・・（２）
前記樹脂微粒子は、ビニル系単量体を乳化重合して得られたシード粒子に、さらにビニル系単量体をラジカル重合させたものであることが好ましい。 In the conductive fine particles of the present invention, a conductive layer is formed on the surface of the resin fine particles, the K value defined by the following formula (1) is 500 kgf / mm ² or less at 20 ° C., and recovery after compression deformation The rate is 5 to 25% at 20 ° C.

(In Formula (1), F and S are respectively the load value (kgf) and compression displacement (mm) in 10% compression deformation of conductive fine particles, and R is the radius (mm) of conductive fine particles.)
The K value is preferably 100 to 450 kgf / mm ² at 20 ° C., and the recovery rate is preferably 5 to 20% at 20 ° C.
The particle size is preferably 2.5 to 7.5 μm.
It is preferable that the standard deviation S of particle diameters and the average value D _av of particle diameters satisfy the following formula (2) when the number of samples is 300 or more.
S ≦ D _av × 0.05 (2)
It is preferable that the resin fine particles are obtained by radical polymerization of a vinyl monomer to seed particles obtained by emulsion polymerization of a vinyl monomer.

  ADVANTAGE OF THE INVENTION According to this invention, when using for the connection between electrodes, the electroconductive fine particles which individual particle | grains express sufficient electroconductivity and do not produce a nonuniformity in a liquid crystal image can be provided.

式（１）中、Ｆ、Ｓはそれぞれ導電性微粒子の１０％圧縮変形における荷重値（ｋｇｆ）、圧縮変位（ｍｍ）であり、Ｒは導電性微粒子の半径（ｍｍ）である。 Hereinafter, the present invention will be described in detail.
The conductive fine particles of the present invention have a K value defined by the following formula (1) of 500 kgf / mm ² or less at 20 ° C. and a recovery rate after compression deformation of 5 to 25% at 20 ° C. It is.

In Formula (1), F and S are the load value (kgf) and compression displacement (mm) in 10% compressive deformation of conductive fine particles, respectively, and R is the radius (mm) of conductive fine particles.

Here, the K value is a value representing the hardness of a sphere, as described in, for example, the Landauri-Fuchsitz theory physics course “elasticity theory” (published in Tokyo Book 1972). Large value.
When conductive fine particles having a K value of 500 kgf / mm ² or less at 20 ° C. are used for connection between electrodes of a liquid crystal display element, each conductive fine particle exhibits sufficient conductivity. Therefore, a certain level of conductivity can be ensured without using a large number of conductive fine particles, which is advantageous in terms of cost. In addition, since the arrangement density of the conductive fine particles can be lowered, the aggregation of the particles is suppressed, electrical short-circuiting hardly occurs, and the manufacturing yield of the liquid crystal display element does not decrease. The more preferable K value of the conductive fine particles at 20 ° C. is 100 to 450 kgf / mm ² .

The reason why the conductive fine particles having a K value at 20 ° C. of 500 kgf / mm ² or less exhibits sufficient conductivity is considered as follows.
That is, the present inventors change the electric resistance of each conductive fine particle sandwiched between the electrodes as shown in FIG. 1 along with the compressive deformation rate of the conductive fine particle, and the compressive deformation rate is around 30%. It has been found that the electrical resistance is minimized. Therefore, it has become clear from the viewpoint of conductivity that the conductive fine particles are preferably disposed between the electrodes in a state of being compressed and deformed so that the compression deformation rate is about 30%. Conductive fine particles having a K value of 500 kgf / mm ² or less at 20 ° C. can be easily compressed and deformed to about 30% and can exhibit high conductivity.
The electrical resistance of the conductive fine particles is minimized when the compressive deformation rate is about 30%, because the contact area between the conductive fine particles and the electrode increases as the compressive deformation rate is about 30%. The electrical conductivity is improved and the electrical resistance is lowered. However, when the compressive deformation rate is larger than that, the conductive layer on the particle surface is cracked, and as a result, the electrical resistance starts to increase.

Here, if it is attempted to compressively deform conductive fine particles having a K value at 20 ° C. exceeding 500 kgf / mm ² to a compression deformation rate of about 30%, a very high press pressure is required, which increases the productivity of the liquid crystal display element. In addition, the electrodes sandwiching the conductive fine particles may be damaged. Further, the distance (gap) between the electrodes becomes non-uniform, and the liquid crystal display tends to be uneven.

The K value of the conductive fine particles is obtained as follows.
First, a compressive load is applied to one conductive fine particle using a micro-compression tester, and a compressive displacement at that time is detected to create a compressive load-compressive displacement curve. Next, a load value F and a compression displacement S in 10% compression deformation are obtained from this curve. And K value is calculated | required by substituting these values and the radius R of electroconductive fine particles for Formula (1).
In a micro compression tester, a compression load can be electrically detected as a displacement by an operating transformer, with a compression load as an electromagnetic force. An example of such a micro-compression tester is a PCT-200 model manufactured by Shimadzu Corporation. This tester includes a diamond cylinder having a diameter of 50 μm as means for compressing an object. The compression was performed by a constant load speed compression method, the rate of increasing the load was 0.27 gf per second, and the test load was 10 gf at the maximum.

The conductive fine particles of the present invention have a recovery rate after compression deformation of 5 to 25% at 20 ° C.
Here, the recovery rate after compression deformation is the recovery rate when the conductive fine particles are compressed and deformed by applying a compression load of up to 1 gf and then the compression load is reduced to 0.1 gf. Recovery rate when the base point (origin load value) is 0.1 gf and the maximum load (reverse load value) is 1 gf.
As a specific measurement method, a compressive load is applied to one conductive fine particle up to 1 gf using a micro compression tester as in the case of obtaining the K value, and then the load is reduced to 0.1 gf. Reduce. By detecting the compression displacement at that time, a compression load-compression displacement curve as shown in FIG. 2 is produced. In FIG. 2, (a) is a curve when the compression load is increased, and (b) is a curve when the compression load is decreased. The ratio (L ₂ / L ₁ ) between the displacement L ₁ up to the maximum load when the compressive load is increased and the displacement L ₂ up to the base point of the load when the compressive load is reduced is expressed in%. Things are the recovery rate.

When conductive fine particles having a recovery rate after compression deformation of 5 to 25% at 20 ° C. are used for the connection between the electrodes, a high-quality liquid crystal display element free from unevenness of liquid crystal images and poor contact can be produced. Further, there is no possibility that the electrode is damaged by the deformation and recovery of the conductive fine particles.
Here, in the case of conductive fine particles having a recovery rate of more than 25% after compressive deformation, the distance (gap) between the electrodes becomes non-uniform due to the deformation recovery of the conductive fine particles, and liquid crystal image unevenness is likely to occur. Fine particles can damage the electrode. On the other hand, if it is less than 5%, a gap is likely to occur between the conductive fine particles and the electrode, which may cause a contact failure. That is, the conductive fine particles are usually filled between electrodes in a paste state dispersed in a thermosetting resin, and then the electrodes are connected by curing the thermosetting resin. At this time, the thermosetting resin expands by heating at the time of curing and contracts by cooling to room temperature, so that the volume fluctuates. On the other hand, in the meantime, the conductive fine particles having a recovery rate of less than 5% hardly recover from deformation. Therefore, a gap is generated between the conductive fine particles and the electrode, and contact failure tends to occur. A more preferable recovery rate of the conductive fine particles is 5 to 20%.

The conductive fine particles are not limited as long as the conductive fine particles have both the above-described K value and the recovery rate after compression deformation, and a conductive layer is formed on the surface of the resin fine particles. It is preferable that the seed particles obtained by emulsion polymerization of a vinyl monomer are further obtained by radical polymerization of a vinyl monomer. The material of the resin fine particles is preferably a copolymer of divinylbenzene and styrene. As a method for producing resin fine particles made of such a copolymer, first, a vinyl monomer containing styrene as a main component is emulsion-polymerized to obtain seed particles, and then the seed particles are mixed with divinylbenzene. A method of radical polymerization of a vinyl monomer composed of styrene is preferable.
The molar ratio of divinylbenzene and styrene in producing the copolymer is preferably 8 mol or less, more preferably 0.5 to 4.0 mol, relative to 1 mol of divinylbenzene. Within such a range, it is easy to obtain conductive fine particles having the above-described K value and recovery rate.

Although there is no restriction | limiting in particular as a conductive layer formed in the surface of resin fine particle, If comprised from the inner layer which consists of nickel plating, and the outer layer which consists of gold plating, more stable electroconductivity can be expressed. Such a conductive layer can be formed by performing a gold substitution reaction after performing electroless nickel plating.
Examples of other conductive layers include nickel, gold, silver, copper, cobalt tin, indium, and those formed from alloys containing these as the main components. Examples of the formation method include electroless plating methods. Examples thereof include a method of coating a paste containing metal fine powder on resin fine particles, a physical vapor deposition method such as a vacuum vapor deposition method, an ion plating method, and an ion sputtering method.

The particle size of the conductive fine particles is not particularly limited and can be appropriately set according to the use. However, when it is in the range of 2.5 to 7.5 μm, it is suitably used for connection between electrodes in a thin liquid crystal display element. it can.
In addition, when the number of samples is 300 or more and the standard deviation S of particle diameters and the average value D _av of particle diameter satisfy the following formula (2), the particle diameter uniformity as a powder is excellent. The liquid crystal display element can be suitably used for connection between the electrodes. In addition, the value measured from the electron micrograph is employ | adopted as a particle size of each electroconductive fine particle.
S ≦ D _av × 0.05 (2)
Moreover, although there is no restriction | limiting in the ratio of the resin fine particle and conductive layer in electroconductive fine particles, the content rate of the conductive layer in electroconductive fine particles is the range of 30-80 mass% normally.

When such conductive fine particles are used for connection between electrodes, for example, the following may be performed.
First, conductive fine particles are added to an insulating binder made of a thermosetting resin so as to have a concentration of about several mass% and dispersed uniformly. This dispersion is applied to one surface of a pair of electrodes. The application may be performed by a printing method such as a screen printing method or a method using a dispenser. Next, the other electrode is superimposed on the surface coated with the dispersion, and these are pressed. It is preferable from the viewpoint of conductivity that the pressurization is performed so that the conductive fine particles are compressed and deformed to a compression deformation rate of about 30%. Next, the binder is cured by heating while maintaining the compression deformation state of the conductive fine particles. By such a method, the electrodes can be electrically connected with conductive fine particles.

There are no particular restrictions on the type of electrodes connected in this way, electrodes obtained by forming an ITO thin film or aluminum thin film on a glass plate, or etching after a copper sheet is attached on a plastic film. And an electrode obtained by printing a silver paste or carbon black on a plastic film.
The conductive fine particles described above have sufficient conductivity when used for connection between electrodes, and do not cause unevenness in the liquid crystal image. It can be suitably used for connection between electrodes in a component.

Hereinafter, the present invention will be specifically described with reference to examples. Hereinafter, “parts” and “%” are based on mass.
[Production example]
(Manufacture of seed particles)
In a four-necked flask equipped with a stirrer, a thermometer, a nitrogen inlet tube, and a reflux condenser, 19.5 parts of styrene, 0.5 part of acrylic acid, 80 parts of pure water, and 0.2 part of potassium persulfate are placed. Polymerization was carried out at 80 ° C. for 6 hours under an air stream.
The obtained polymerization mixture was neutralized with ammonium hydroxide and then filtered through a 200 mesh filter cloth to obtain an emulsion as a filtrate.
On the other hand, 5 parts of lauryl methacrylate, 5 parts of sodium lauryl sulfate, and 250 parts of pure water were dispersed with a high-pressure homogenizer manufactured by IKA, and then 25 parts of the previously obtained emulsion was added and stirred all day and night to contain seed particles. A mixture was obtained.

[Example 1]
(Manufacture of conductive fine particles)
In a four-necked flask equipped with a stirrer, thermometer, nitrogen inlet tube and reflux condenser, 420 parts of divinylbenzene, 580 parts of styrene, 3.3 parts of 75% benzoyl peroxide, 3 parts of azobisisovaleronitrile, water 2300 Part, 20 parts of sodium lauryl sulfate, and 67 parts of a mixed solution containing seed particles were stirred for a whole day and night.
Next, 4 parts of sodium sulfite, 10 parts of sodium sulfate, 500 parts of 5% polyvinyl alcohol aqueous solution and 500 parts of water were added, and polymerization was performed at 65 ° C. for 3 hours, 80 ° C. for 1 hour, and 90 ° C. for 1 hour in a nitrogen stream. went.
Thereafter, this was washed, dried and classified to obtain resin fine particles having an average particle size of 7.03 μm and a standard deviation of 0.29 μm.
Then, after electroless nickel plating was performed on the resin fine particles, a gold substitution reaction was performed to obtain conductive fine particles in which a nickel plating layer and a gold plating layer were sequentially formed on the surface.
An electron micrograph was taken of the conductive fine particles, and the average value D _av and standard deviation S of the particle diameters were determined for 300 samples. D _av = 7.21 μm and S = 0.29 μm.

(Analysis of conductive fine particles)
When the conductive fine particles were analyzed, the gold content was 25.0% by mass, the nickel content was 20.0% by mass, and the content of the conductive layer in the conductive fine particles was 45.0% by mass. .
In addition, using a PCT-200 model manufactured by Shimadzu Corporation as a micro-compression tester, a compressive load is applied to one conductive fine particle randomly selected from the obtained conductive fine particles, and compression is performed at that time. The displacement is detected, and a compression load-compression displacement curve is prepared. Then, a load value F: 2.35 × 10 ⁻⁴ kgf and a compression displacement S: 7.21 × 10 ^{−4 at} 10% compression deformation from the curve. By obtaining mm and substituting these values and the radius R of the conductive fine particles into the formula (1), K value = 429 kgf / mm ² was obtained. The compression was performed by a constant load speed compression method, the rate of increasing the load was 0.27 gf per second, and the test load was 10 gf at the maximum.
Also, using the same micro-compression tester, a compressive load is similarly applied to one conductive fine particle up to 1 gf, and then the compression displacement is detected when the load is reduced to 0.1 gf. Thus, a compression load-compression displacement curve as shown in FIG. 2 was prepared, and the displacement L ₁ up to the maximum load when the compression load was increased: 3.10 μm, and the load when the compression load was decreased The ratio (L ₂ / L ₁ ) with the displacement L ₂ to the base point: 0.56 μm was determined and expressed in%, and a recovery rate of 18% was obtained.

(Relationship between electrical resistance of conductive fine particles and compressive deformation rate)
With respect to the conductive fine particles obtained in this way, the electrical resistance per one conductive fine particle when compressed and deformed at various compression deformation rates was determined. Table 1 shows the compression deformation rate and electrical resistance.
Specifically, first, 0.001 g of conductive fine particles, 1 g of epoxy resin, 0.2 g of glass rod spacer, and 0.64 g of a curing agent were mixed well to produce a paste. Next, two glass plates with a gold wire having a width W of 0.5 mm and a thickness T of 0.5 μm formed on one side are prepared, and the surfaces on which the gold wires are formed face each other. And it arrange | positioned so that a gold wire might orthogonally cross. And the above-mentioned paste was filled between the gold wires, applied with a load of 500 g, and cured on a hot plate under the conditions of 200 ° C. and 120 seconds to prepare a test piece.

At this time, the compression deformation rate of the conductive fine particles was adjusted by changing the diameter of the glass rod spacer to be used. That is, since the glass rod spacer is not compressed and deformed by a load of 500 g, if a glass rod spacer having a diameter of d _g is used, a test piece with a gold wire interval of d _g can be produced. The compressive deformation rate of the conductive fine particles sandwiched between them is obtained by the following formula (3). In the preparation of this test piece, the concentration of the conductive fine particles in the paste is set to a very small value of 0.05%. Therefore, after the paste is cured, the shape of the conductive fine particles recovers and the interval between the gold wires is reduced. It can be regarded as not spreading.
Compression deformation rate [%] = (2R−d _g ) × 100 / 2R (3)

Then, an electric current was passed through the test piece to determine the electrical resistance A as the entire cured paste.
On the other hand, a reference piece was obtained by the same process as the production of the test piece except that a glass plate on which no gold wire was formed was used, and the arrangement density B per unit area of the conductive fine particles in this paste was measured.
Then, as the arrangement density of the conductive fine particles in the paste in the test piece, the arrangement density B of the conductive fine particles in the paste in the reference piece is adopted, and the bonding area C of the paste in the test piece is measured, and the following formula ( The number N of conductive fine particles involved in conduction was obtained by 4), and the electrical resistance A ₁ per conductive fine particle was calculated from the following formula (5).
N = C × B (4)
A ₁ = N × A (5)

As shown in Table 1, it became clear that the electric resistance A ₁ per one conductive fine particle depends on the diameter d _g of the glass rod spacer, and is minimized particularly when d _g = 5 μm. When d _g = 5 μm, the compression deformation rate of the conductive fine particles = 30.7 [%].
Therefore, the electrical resistance A ₁ per one conductive particles varies according to the pressure change rate, the compression deformation ratio is shown to be minimized in the order of 30%.

[Examples 2-3 and Comparative Examples 1-2]
Resin fine particles were prepared in the same manner as in Example 1 except that the amounts of divinylbenzene and styrene used were changed as shown in Table 2, and classified so that the standard deviation of the particle size was 5% or less of the average particle size. Further, a conductive layer was formed in the same manner to obtain conductive fine particles as shown in Table 2.
Subsequently, a test piece was produced in the same manner as in Example 1 using the obtained conductive fine particles. However, here, only one type of test piece using a glass rod spacer with d _g = 5 μm was produced.

The following evaluations were performed on the conductive fine particles and test pieces obtained in the above examples.
[Reliability evaluation]
In each example, the following reliability evaluations (humidity resistance test and heat resistance test) were performed on the test pieces obtained by using glass lot spacers with d _g = 5 μm.
Humidity resistance test: The test piece was stored in an environment of 65 ° C. and a relative humidity of 90% for 500 hours, and the electrical resistance per one conductive fine particle before and after the test piece was measured. The measured values are shown in Table 3. When the electrical resistance after the test was 1.2 times or less that before the test, it was determined that the moisture resistance reliability was good, and the result was shown by ○ in Table 4. When it exceeded 1.2 times, it was set as x.
Heat resistance test: The test piece was stored in an environment of 110 ° C. for 500 hours, and the electric resistance per one conductive fine particle before and after the test piece was measured. The measured values are shown in Table 3. When the electrical resistance after the test was 1.2 times or less that before the test, it was determined that the heat resistance reliability was good, and the result was shown by ○ in Table 4. When it exceeded 1.2 times, it was set as x.

[Press productivity evaluation]
Conductive fine particles 0.055 g obtained in each example, epoxy resin 1 g, d _g = 5 μm glass rod spacer 0.2 g, and curing agent 0.64 g were mixed well to produce a paste, and between two glass plates It was sandwiched and cured under conditions of a press pressure of 1 kg / cm ² and 150 ° C. for 30 minutes.
After cooling, the distance between the two glass plates was measured, and when the value was 5.05 μm or less, it was determined that the press productivity was good, and indicated by ○ in Table 4. On the other hand, when the value exceeds 5.05 μm, it can be determined that a higher press pressure is necessary for compressive deformation to a compression deformation rate of about 30%. In this case, it is determined that the press productivity is poor. It showed in.

[Unevenness of LCD image]
Conductive fine particles 0.055 parts obtained in each example, epoxy resin 1 part, d _g = 5 μm glass rod spacer 0.2 part, curing agent 0.64 part are mixed well to produce a paste, and a liquid crystal display It used for the connection between the electrodes in an element. And the presence or absence of the image nonuniformity in the obtained liquid crystal display element was determined visually. The results are shown in Table 4. At that time, an electrode made of an ITO thin film-glass plate with an alignment film formed thereon was used. In addition, liquid crystal sealing, polarizing filter arrangement, and backlight mounting were carried out by conventional methods.

As described above, the conductive fine particles obtained in each Example had a high electrical conductivity per one (initial electrical resistance) before the moisture resistance test and before the heat resistance test, which was smaller than that of the comparative example. . In addition, the moisture resistance reliability and the heat resistance reliability are excellent because the contact area between the conductive fine particles and the electrode is maintained large. Furthermore, since the conductive fine particles obtained in each example were compressed and deformed even at a low pressing pressure, the press productivity was good, and even when used in a liquid crystal display element, no unevenness in the liquid crystal image was observed.
On the other hand, in the case of Comparative Example 1, since the recovery rate after compressive deformation is small, it is considered that a gap was generated between the conductive fine particles and the electrode, resulting in poor contact, initial electrical resistance was poor, and heat resistance Sex was very bad.
Moreover, in the thing of the comparative example 2, since K value was large, when trying to compress-deform, a high press pressure was needed and it was suggested that it is inferior to press productivity. In the press productivity evaluation, the distance between the glass plates after the paste was cured was 5.08 μm. Further, the initial electrical resistance was high, and the moisture resistance reliability and heat resistance reliability were also poor. This can be presumed to be a result of the conductive fine particles gradually deforming and recovering because the recovery rate after compression deformation is large. Furthermore, the liquid crystal display was uneven, which is considered to be because the distance between the electrodes became non-uniform because both the K value and the recovery rate after compression deformation were large.

It is a graph which shows the relationship between the electrical resistance of electroconductive fine particles, and a compressive deformation rate. It is a graph which shows the relationship between the compressive load and conductive displacement of electroconductive fine particles.

Claims (5)

A conductive layer is formed on the surface of the resin fine particles, the K value defined by the following formula (1) is 500 kgf / mm ² or less at 20 ° C., and the recovery rate after compression deformation is 5 to 25 at 20 ° C. % Conductive fine particles, characterized by

(In Formula (1), F and S are respectively the load value (kgf) and compression displacement (mm) in 10% compression deformation of conductive fine particles, and R is the radius (mm) of conductive fine particles.) ^2. The conductive fine particle according to claim 1, wherein the K value is 100 to 450 kgf / mm ² at 20 ° C., and the recovery rate is 5 to 20% at 20 ° C. 3.   3. The conductive fine particles according to claim 1, wherein the particle diameter is 2.5 to 7.5 μm. _4. The conductive fine particle according to claim 1, wherein the standard deviation S of the particle diameter and the average value D _av of the particle diameter satisfy the following formula (2) when the number of samples is 300 or more.
S ≦ D _av × 0.05 (2) 5. The resin fine particles according to any one of claims 1 to 4, wherein the resin particles are obtained by radical polymerization of vinyl monomers on seed particles obtained by emulsion polymerization of vinyl monomers. The electroconductive fine particles as described.

Images