JP7408930B2 - Conductive particles, dispersion and manufacturing method thereof - Google Patents

Description

The present invention relates to conductive particles, a method for producing the same, and a dispersion containing the same.

In recent years, in the field of electronics, electronic devices have become thinner and lighter, and there is a need for multi-functionality for wearable applications. Compared to conventional inorganic materials such as ceramics, silver, and copper, the market for conductive polymers is expected to expand due to their lightness, flexibility, and transparency.

As mentioned above, conductive polymers are one of the materials that are highly demanded by the market, but the reality is that most of them are provided as dispersions. The reason for this is that the conductive polymer itself, which has had the dispersion medium removed from the dispersion liquid, is often difficult to dissolve or disperse in any solvent or dispersion medium. It is assumed that this is because they are getting a lot of things. In addition, conductive polymers are expected to be processed into films, sheets, etc., and it is advantageous to make them thicker in order to increase conductivity, but commercially available dispersion Most of the liquids have a conductive polymer concentration (content) as low as several percent by mass or less, making it difficult to easily obtain a thick film by coating.

Patent Document 1 discloses a conductive polymer dispersion containing a conductive composite containing a π-conjugated conductive polymer and a dispersion medium. However, the conductive composite disclosed in Patent Document 1 has a problem in that a highly concentrated dispersion cannot be obtained.

Japanese Patent Application Publication No. 2017-210501

The problem to be solved by the present invention is to provide conductive particles that can be dispersed at a high concentration, a dispersion thereof, and a method for manufacturing the conductive particles.

The present inventors have conducted intensive research to solve the above-mentioned problems, and as a result, have arrived at the present invention. That is, the present invention relates to conductive particles having a number-based median diameter D50 within a range of 0.5 to 4 μm, and a content ratio of particles having a particle diameter of 10 μm or more is less than 1%.

The present invention also provides the above-mentioned conductive material comprising a conductive polymer, wherein the conductive polymer is one or more selected from the group consisting of poly(3,4-ethylenedioxythiophene), polyaniline, and polypyrrole. Regarding particles.

Further, the present invention relates to the above conductive particles having an aspect ratio of 5 or less.

Further, the present invention relates to the above conductive particles that can be uniformly dissolved or dispersed when 5 parts by mass of the conductive particles and 95 parts by mass of water are mixed at 25°C.

The present invention also relates to a dispersion in which the conductive particles are dissolved or dispersed in a dispersion medium, and the concentration of the conductive particles in the dispersion is within a range of 2 to 30% by mass. .

The present invention also provides a method for producing conductive particles containing a conductive polymer, in which a solution or dispersion containing the conductive polymer is spray-dried, and the number-based median diameter D50 is 0.5. The present invention relates to a method for producing conductive particles in which the number of particles having a diameter of 10 μm or more is less than 1%.

The present invention has made it possible to provide conductive particles that can be dispersed at high concentrations. Furthermore, it has become possible to provide a dispersion containing conductive particles at a high concentration.

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this invention is demonstrated concretely.
<Conductive particles>
The conductive particles in the present invention are characterized by satisfying the following conditions.
(1) The number-based median diameter D50 is within the range of 0.5 to 4 μm.
(2) The content ratio of the number of particles having a particle diameter of 10 μm or more is less than 1%.

(Particle size, number-based median diameter D50)
In this specification, the particle diameter of a conductive particle is defined as the value of the long axis and the short axis of the conductive particle from an image obtained by observing the conductive particle using a scanning electron microscope (SEM). It is measured and means the value of (long axis value + short axis value)/2. In addition, the number-based median diameter D50 means the particle diameter at 50% cumulative distribution in the cumulative distribution calculated for 200 arbitrarily selected particles in descending order of particle diameter.
The number-based median diameter D50 of the conductive particles is in the range of 0.5 to 4 μm, more preferably in the range of 0.5 to 3 μm, in order to disperse at a high concentration. When the number-based median diameter D50 is equal to or larger than the above lower limit, the surface area is not too large and aggregation of particles is suppressed, which is preferable from the viewpoint of redispersibility and handling. On the other hand, below the above upper limit, the proportion of coarse particles decreases, which is preferable in that uniform redispersion can be achieved. Further, from the viewpoint of increasing the concentration, the conductive particles are preferably those that can be uniformly dissolved or dispersed when 5 parts by mass of the conductive particles and 95 parts by mass of water are mixed at 25°C.

(Particle content of 10 μm or more)
Among 200 arbitrary particles selected from images observed using SEM, the ratio of the number of particles having a particle diameter of 10 μm or more is defined as the content ratio (content rate). Particles larger than 10 μm are less than 1% for uniform redispersion. Particles with a diameter of 10 μm or more have a small surface area and the contact area with the dispersion medium is reduced, so it is difficult to obtain a starting point for redispersion and it is difficult to uniformly disperse the particles.

(aspect ratio)
Using the long axis value and short axis value of each particle used in the above particle diameter calculation method, calculate the long axis value/short axis value, and calculate the average value of the obtained values as the aspect ratio. It was compared. The aspect ratio is preferably 5 or less, more preferably 3 or less. Below the above upper limit, the conductive particles can be more densely packed when redispersing them, which is suitable for increasing the concentration.

<Conductive polymer>
The conductive particles of the present invention preferably contain a conductive polymer. The conductive polymer is preferably an organic polymer whose main chain is composed of a π-conjugated system. Furthermore, in this specification, materials containing the following dopants are also considered to be conductive polymers.

The conductive polymer is not particularly limited, and examples thereof include polyaniline conductive polymer, polypyrrole conductive polymer, polythiophene conductive polymer, polyacetylene conductive polymer, polyphenylene conductive polymer, and polyphenylene vinylene conductive polymer. Examples include conductive polymers, polyaniline conductive polymers, polyacene conductive polymers, polythiophene vinylene conductive polymers, and copolymers thereof. From the viewpoint of stability in air, polyaniline-based conductive polymers, polypyrrole-based conductive polymers, and polythiophene-based conductive polymers are preferred, and from the viewpoint of conductivity, polythiophene-based conductive polymers are more preferred. The conductive polymers can be used alone or in combination of two or more.

Examples of polyaniline-based conductive polymers include polyaniline, poly(2-methylaniline), poly(3-isobutylaniline), poly(2-anilinesulfonic acid), poly(3-anilinesulfonic acid), and the like.

Examples of polypyrrole-based conductive polymers include polypyrrole, poly(N-methylpyrrole), poly(3-methylpyrrole), poly(3-ethylpyrrole), poly(3-n-propylpyrrole), and poly(3-butylpyrrole). pyrrole), poly(3-octylpyrrole), poly(3-decylpyrrole), poly(3-dodecylpyrrole), poly(3,4-dimethylpyrrole), poly(3,4-dibutylpyrrole), poly(3-dibutylpyrrole) -carboxypyrrole), poly(3-methyl-4-carboxypyrrole), poly(3-methyl-4-carboxyethylpyrrole), poly(3-methyl-4-carboxybutylpyrrole), poly(3-hydroxypyrrole) , poly(3-methoxypyrrole), poly(3-ethoxypyrrole), poly(3-butoxypyrrole), poly(3-hexyloxypyrrole), poly(3-methyl-4-hexyloxypyrrole), etc. .

Polythiophene-based conductive polymers include polythiophene, poly(3-methylthiophene), poly(3-ethylthiophene), poly(3-propylthiophene), poly(3-butylthiophene), poly(3-hexylthiophene), Poly(3-heptylthiophene), poly(3-octylthiophene), poly(3-decylthiophene), poly(3-dodecylthiophene), poly(3-octadecylthiophene), poly(3-bromothiophene), poly( 3-chlorothiophene), poly(3-iodothiophene), poly(3-cyanothiophene), poly(3-phenylthiophene), poly(3,4-dimethylthiophene), poly(3,4-dibutylthiophene), Poly(3-hydroxythiophene), poly(3-methoxythiophene), poly(3-ethoxythiophene), poly(3-butoxythiophene), poly(3-hexyloxythiophene), poly(3-heptyloxythiophene), Poly(3-octyloxythiophene), poly(3-decyloxythiophene), poly(3-dodecyloxythiophene), poly(3-octadecyloxythiophene), poly(3,4-dihydroxythiophene), poly(3, 4-dimethoxythiophene), poly(3,4-diethoxythiophene), poly(3,4-dipropoxythiophene), poly(3,4-dibutoxythiophene), poly(3,4-dihexyloxythiophene), Poly(3,4-diheptyloxythiophene), poly(3,4-dioctyloxythiophene), poly(3,4-didecyloxythiophene), poly(3,4-didodecyloxythiophene), poly(3,4-didecyloxythiophene) ,4-ethylenedioxythiophene), poly(3,4-propylenedioxythiophene), poly(3,4-butylenedioxythiophene), poly(3-methyl-4-methoxythiophene), poly(3-methyl -4-ethoxythiophene), poly(3-carboxythiophene), poly(3-methyl-4-carboxythiophene), poly(3-methyl-4-carboxyethylthiophene), poly(3-methyl-4-carboxybutyl) thiophene), poly(2,3-dihydrothieno[3,4-b]-[1,4]dioxepin-3-yloxy]-1-propanesulfonic acid sodium), poly(3-[(2,3-dihydrothieno[ 3,4-b]-[1,4]dioxepin-3-yloxy]-1-potassium propanesulfonate), poly(3-[(2,3-dihydrothieno[3,4-b]-[1,4 ] dioxepin-3-yloxy]-1-methyl-1-propanesulfonate sodium), poly(3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxepin-3-yloxy] -1-ethyl-1-propanesulfonate), poly(3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxepin-3-yloxy]-1-propyl-1- poly(sodium propanesulfonate), poly(sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxepin-3-yloxy]-1-butyl-1-propanesulfonate)), (sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxepin-3-yloxy]-1-pentyl-1-propanesulfonate), poly(3-[(2, Sodium 3-dihydrothieno[3,4-b]-[1,4]dioxepin-3-yloxy]-1-hexyl-1-propanesulfonate), poly(3-[(2,3-dihydrothieno[3,4 -b]-[1,4]dioxepin-3-yloxy]-1-isopropyl-1-propanesulfonic acid sodium), poly(3-[(2,3-dihydrothieno[3,4-b]-[1, 4] Sodium dioxepin-3-yloxy]-1-isobutyl-1-propanesulfonate), poly(3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxepin-3-yloxy) ]-1-isopentyl-1-propanesulfonate), poly(3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxepin-3-yloxy]-1-fluoro-1 -sodium propanesulfonate), poly(3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxepin-yloxy]-1-methyl-1-potassium propanesulfonate), poly(potassium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxepin-3-yloxy]-1-methyl-1-propanesulfonic acid), poly(3-[(2,3- ammonium dihydrothieno[3,4-b]-[1,4]dioxepin-3-yloxy]-1-methyl-1-propanesulfonate), poly(3-[(2,3-dihydrothieno[3,4-b ]-[1,4]dioxepin-3-yloxy]-1-methyl-1-propanesulfonic acid triethylammonium), poly(4-[(2,3-dihydrothieno[3,4-b]-[1,4 ] dioxepin-3-yloxy]-1-butanesulfonate), poly(4-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxepin-3-yloxy]-1-butane potassium sulfonate), poly(4-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxepin-3-yloxy]-1-methyl-1-butanesulfonate sodium), poly( 4-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxepin-3-yloxy]-1-methyl-1-butanesulfonic acid potassium), poly(4-[(2,3 -dihydrothieno[3,4-b]-[1,4]dioxepin-3-yloxy]-1-fluoro-1-butanesulfonate), or poly(4-[(2,3-dihydrothieno[3,4 -b]-[1,4]dioxepin-3-yloxy]-1-fluoro-1-butanesulfonic acid potassium, and the like.

Among the above-mentioned conductive polymers, polythiophene-based conductive polymers are preferred from the viewpoint of conductivity, transparency, and heat resistance, and poly(3,4-ethylenedioxythiophene) is particularly preferred.
One type of conductive polymer may be used alone, or two or more types may be used in combination.

(dopant)
In this specification, the term "dopant" refers to a polymer having two or more monomer units having anionic groups in its molecule, and contributes to improving the conductivity of a conductive polymer. The anion group of the polyanion is preferably a sulfo group or a carboxy group. Specific examples of such polyanions include polystyrene sulfonic acid, polyvinyl sulfonic acid, polyallylsulfonic acid, polyacrylsulfonic acid, polymethacrylsulfonic acid, poly(2-acrylamido-2-methylpropanesulfonic acid), and polyisoprene sulfonic acid. acids, polymers with sulfonic acid groups such as polysulfoethyl methacrylate, poly(4-sulfobutyl methacrylate), polymethacryloxybenzenesulfonic acid, polyvinyl carboxylic acid, polystyrene carboxylic acid, polyallyl carboxylic acid, polyacrylic carboxylic acid , polymethacryliccarboxylic acid, poly(2-acrylamido-2-methylpropanecarboxylic acid), polyisoprenecarboxylic acid, polyacrylic acid, and other polymers having carboxylic acid groups. It may be a homopolymer of these or a copolymer of two or more thereof. Among these polyanions, polymers having sulfonic acid groups are preferred, and polystyrene sulfonic acid is more preferred, since it can further increase the conductivity. The polyanions may be used alone or in combination of two or more. The mass average molecular weight of the polyanion is preferably 20,000 or more and 1,000,000 or less, more preferably 100,000 or more and 500,000 or less. The mass average molecular weight in this specification is a value determined by gel permeation chromatography using polystyrene as a standard substance. The content of the dopant is preferably in the range of 1 to 90% by mass in the conductive polymer.

<Dispersion medium>
The dispersion medium herein refers to water or an organic solvent. Examples of the organic solvent include, but are not limited to, alcohol solvents, ketone solvents, ester solvents, aromatic hydrocarbon solvents, amide solvents, and the like. One type of dispersion medium may be used alone, or two or more types may be used in combination.
Examples of alcoholic solvents include methanol, ethanol, isopropanol, n-butanol, t-butanol, and allyl alcohol.
Examples of ketone solvents include diethyl ketone, methylpropyl ketone, methyl butyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, methyl amyl ketone,
Examples include diisopropyl ketone, methyl ethyl ketone, acetone, diacetone alcohol, and the like. Examples of the ester solvent include ethyl acetate, propyl acetate, butyl acetate, and the like. Examples of the aromatic hydrocarbon solvent include benzene, toluene, xylene, ethylbenzene, propylbenzene, and isopropylbenzene. Examples of the amide solvent include N-methylpyrrolidone, dimethylacetamide, dimethylformamide, and the like. Among dispersion media, water is particularly preferred since the conductive polymer has high dispersibility.

<Dispersion>
The dispersion in the present invention refers to conductive particles dissolved or dispersed in a dispersion medium. The concentration of conductive particles in the dispersion is preferably 2 to 30% by weight, more preferably 3 to 10% by weight. If it is above the above lower limit, a thick film can be easily obtained, and if it is below the above lower limit, it can be easily dispersed from the viewpoint of viscosity, which is preferable.

<Manufacturing process of conductive particles>
The manufacturing process of conductive particles is obtained by drying a conductive polymer dispersion and removing coarse particles with a particle size of 10 μm or more by classification. You can crush it. The drying method is not particularly limited as long as the conductive particles of the present invention can be obtained, and examples thereof include vacuum heating drying, freeze drying, and spray drying.

The conductive polymer dispersion can be obtained, for example, by chemical oxidation polymerization of a monomer forming the conductive polymer in a dopant dispersion medium. Moreover, a commercially available aqueous conductive polymer dispersion may be used.

In vacuum heating drying, the dispersion medium in the conductive polymer dispersion is vacuum dried while being heated. The temperature of vacuum heat drying is preferably 50°C or higher and 200°C or lower, and more preferably 80°C or higher and 120°C or lower for ease of temperature adjustment.

In freeze-drying, water in the conductive polymer aqueous dispersion is frozen and vacuum-dried.
The temperature during freeze-drying is preferably -60°C or higher and 60°C or lower, more preferably -40°C or higher and 40°C or lower. If the freeze-drying temperature is equal to or higher than the lower limit, the temperature can be easily adjusted, and if it is equal to or lower than the upper limit, the conductive polymer aqueous dispersion can be easily freeze-dried.

In spray drying, the aqueous conductive polymer dispersion is sprayed into a vacuum container to evaporate water and dry.
The temperature during spray drying is preferably 50°C or higher and 200°C or lower, more preferably 100°C or higher and 150°C or lower. If the spray drying temperature is at least the above lower limit, the aqueous conductive polymer dispersion can be easily dried, and if it is at or below the upper limit, thermal deterioration of the conductive polymer can be prevented.

As a drying method, freeze drying and spray drying are more preferable, and spray drying is particularly preferable. Conductive particles with a high aspect ratio can be obtained by vacuum heating drying or freeze drying.

The classification method is not particularly limited, but classification is performed using a classifier or a sieve. The particle diameter to be removed by classification is preferably 10 μm or more. Coarse particles of 10 μm or more have a small surface area and the contact area with the dispersion medium is reduced, so it is difficult to obtain a starting point for redispersion and to uniformly disperse the particles.

The method of crushing the conductive particles is not particularly limited, and stirring with a weak shearing force such as a stirrer may be used, but it is better to use a disperser with a high shearing force (homogenizer, etc.) because the particle diameter can be made uniform. preferable.

Hereinafter, the present invention will be explained in more detail with reference to Examples, but the following Examples do not limit the scope of the present invention in any way. In the examples, "parts" represent "parts by mass" unless otherwise specified.

<Number-based median diameter D50>
The number-based median diameter D50 of conductive particles was determined by the following method. The particle size of the particles was determined by measuring the values of the long axis and short axis of the particles from an image obtained by observation using a scanning electron microscope (SEM). The value of (long axis value + short axis value)/2 was regarded as the particle diameter of the particle. Particle diameters were similarly calculated for 200 randomly selected particles. In the cumulative distribution accumulated in descending order of particle size, the particle size at 50% of the cumulative size was defined as the number-based median diameter D50.

<Content ratio of the number of particles having a particle diameter of 10 μm or more (particle content rate of 10 μm or more)>
Among 200 arbitrary particles selected from images observed using SEM, the ratio of the number of particles having a particle diameter of 10 μm or more was defined as the content ratio (content rate).

<Aspect ratio>
Using the long axis value and short axis value of each particle used in the above particle diameter calculation method, the long axis value/short axis value was calculated. The average value of the obtained values was taken as the aspect ratio.

<Manufacture of conductive particles>
(Example 1)
A dispersion containing polyaniline (manufactured by Mitsubishi Chemical Corporation, aquaPASS-50P) was diluted with water to a solid content of 2% by mass, and freeze-dried. The obtained powder is pulverized at a rotational speed of 5000 rpm using a disper (Homomixer MARK II 2.5 type, manufactured by Primix), and classified using a filter with a pore size of 10 μm, so that the number-based median diameter D50: 3 μm, 10 μm or more Conductive particles 1 having a particle content of less than 1% and an aspect ratio of 2.4 were obtained.

(Example 2)
The 2% by mass polyaniline aqueous solution used in Example 1 was heated to 100°C with a high-speed mixer (manufactured by Earth Technica, LFS2) and stirred while drying in vacuum (agitator 1000 rpm, chopper 3000 rpm), and then classified using a 10 μm filter. By doing so, conductive particles 2 having a number-based median diameter D50 of 4 μm, a particle content of 10 μm or more of less than 1%, and an aspect ratio of 4.3 were obtained.

(Example 3)
The 2% by mass polyaniline aqueous solution used in Example 1 was spray-dried at 150°C with a spray dryer (manufactured by BUCHI, B-290) and classified with a 10 μm filter to obtain number-based median diameter D50: 1 μm, 10 μm. Conductive particles 3 having a particle content of less than 1% and an aspect ratio of 1.3 were obtained.

(Example 4)
The 2% by mass polyaniline aqueous solution used in Example 1 was spray-dried at 120°C with a spray dryer (manufactured by BUCHI, B-290) and classified with a 10 μm filter to obtain a number-based median diameter D50 of 2 μm, Conductive particles 4 with a particle content of 10 μm or more of less than 1% and an aspect ratio of 1.9 were obtained.

(Example 5)
The 2% by mass polyaniline aqueous solution used in Example 1 was spray-dried at 120°C with a spray dryer (manufactured by BUCHI, B-290) using an ultrasonic nozzle, and classified with a 10 μm filter to obtain a number-based median. Conductive particles 5 having a diameter D50 of 4 μm, a particle content of 10 μm or more of less than 1%, and an aspect ratio of 1.5 were obtained.

(Examples 6 to 16)
Hereinafter, conductive particles 6 to 16 were obtained in the same manner as in Examples 1 to 5 according to the materials and methods listed in Table 1, respectively. The materials used in Table 1 are as follows.
・aquaPASS-50P (aqueous dispersion containing polyaniline, manufactured by Mitsubishi Chemical Corporation)
・PPY-12 (aqueous dispersion containing polypyrrole, manufactured by Marubishi Yuka Kogyo Co., Ltd.)
・Clevios PH1000 (aqueous dispersion containing poly(3,4-ethylenedioxythiophene), manufactured by Heraeus)
・Clevios P (aqueous dispersion containing poly(3,4-ethylenedioxythiophene), manufactured by Heraeus)

(Comparative example 1)
The 2% by mass polyaniline aqueous solution used in Example 1 was heated to 100°C with a high-speed mixer (manufactured by Earth Technica, LFS2) and stirred (agitator 300 rpm, chopper 1000 rpm) while vacuum drying to obtain a number-based median diameter. Conductive particles 17 having a D50 of 8 μm, a particle content of 10 μm or more of 10%, and an aspect ratio of 3.7 were obtained.

(Examples 17 to 32, Comparative Example 2)
<Production of dispersions 1 to 17>
95 parts of water was added to 5 parts each of conductive particles 1 to 17, and dispersed at 25°C using a planetary stirrer (Awatori Rentaro AR-100, manufactured by Shinky Co., Ltd.) to obtain dispersions 1 to 17, respectively. .

<Dispersibility evaluation of dispersions 1 to 17>
Dispersions 1 to 17 were each visually confirmed and their dispersibility was evaluated based on the following evaluation criteria.

(Evaluation criteria)
◎: Conductive particles are not aggregated and no precipitation occurs even after 24 hours (very good)
○: Conductive particles are not aggregated, but precipitation occurs after 24 hours (good)
×: Aggregation of conductive particles occurs and a uniform dispersion cannot be obtained (defective)

(Examples 33 to 48, Comparative Example 3)
<Production of dispersions 18 to 34>
Water was added to each of conductive particles 1 to 17 to prepare a mixed solution with the above concentration so that the concentration of conductive particles was 2, 5, 7, 10, 15, 20, 25 and 30% by mass. did. These mixed liquids were dispersed using a planetary stirrer (Awatori Rentaro AR-100, manufactured by Shinky Co., Ltd.) for a stirring time of 1 minute and a defoaming time of 1 minute. The particle size distribution of each of the dispersed liquid mixtures was measured using Microtrac (manufactured by Microtrac Bel, MT3300II). Among the above concentrations, the maximum concentration in which the value of the peak particle size (particle size at the maximum frequency) in the particle size distribution did not exceed 100 μm was defined as the maximum filling rate. The dispersions in which each conductive particle had the maximum filling rate were designated as dispersions 18 to 34, respectively.

<Film formation of dispersions 18 to 34>
Dispersions 18 to 33 were each applied to a polyethylene terephthalate (PET) film (manufactured by Toray Industries, Inc., Lumirror (registered trademark) E20 #75, thickness 75 μm) using a 20 mil applicator, and heated at 80°C for 4 minutes and then at 120°C. After drying for 30 minutes, coating films 18 to 33 were prepared. Regarding Dispersion 34, an attempt was made to form a coating film using the same film forming method, but a uniform coating film could not be obtained due to the formation of aggregates, so the following evaluation was not performed.

<Film thickness evaluation of coating films 18 to 33>
For coating films 18 to 33, measure five arbitrary points using a dial gauge specified in Japanese Industrial Standard (JIS) B7503, and take the average value of the three points excluding the upper and lower limits as the film thickness. did.

<Homogeneity evaluation of coating films 18 to 33>
The presence or absence of leakage (leakage of light passing through the coating film) when coating films 18 to 33 are held up to the light of a fluorescent lamp, and the difference between the upper and lower limit values obtained in the film thickness evaluation are relative to the film thickness. The homogeneity of the coating film was evaluated based on whether it was 10% or more.

(Evaluation criteria)
◎: There is no cracking when held up to light, and the difference between the upper and lower limits of the film thickness is less than 10% of the film thickness (very good)
〇: There is no cracking when held up to light, but the difference between the upper and lower limits of the film thickness is 10% or more relative to the film thickness (good)
×: There are gaps when held up to light (defective)

As described above, the conductive particles of the present invention were able to obtain a uniform dispersion free of aggregates at a concentration of 5% by mass or more. Furthermore, it has become clear that the smaller the aspect ratio, the more uniform the coating film can be obtained. On the other hand, with the conductive particles of the comparative example, aggregation occurred and a uniform dispersion could not be obtained.

Claims (4)

Conductive particles having a number-based median diameter D50 within the range of 0.5 to 4 μm and containing less than 1% of particles having a particle diameter of 10 μm or more, 5 parts by mass of the conductive particles conductive particles that can be uniformly dissolved or dispersed when mixed with 95 parts by mass of water at 25°C. 2. The conductive polymer comprises a conductive polymer, and the conductive polymer is one or more selected from the group consisting of a polythiophene conductive polymer, a polyaniline conductive polymer, and a polypyrrole conductive polymer. conductive particles. The conductive particles according to claim 1 or 2, having an aspect ratio of 5 or less. A dispersion in which the conductive particles according to any one of claims 1 to 3 are dissolved or dispersed in a dispersion medium, wherein the concentration of the conductive particles in the dispersion is within the range of 2 to 30% by mass. body.