KR20140138136A - Conductive fine particles, method for manufacturing same, conductive resin composition, conductive sheet, and electromagnetic shielding sheet - Google Patents

Abstract

Provided is a conductive fine particle which can be reduced in cost and excellent in conduction characteristics, and which can be made thin, for example, when a composition blended with a resin is formed into a sheet. The conductive fine particles of the present invention comprise a core including a conductive material and a covering layer covering at least a part of the conductive layer and covering at least a part of the covering layer and being obtained from the following formula A coefficient of losing a circle diameter is 0.15 or more and 0.4 or less, and a plurality of grooves and branch leaves are formed in an outer peripheral shape.
[Equation 1]
Coefficient of circle diameter = (area × 4π) / (circumference) ²

Description

TECHNICAL FIELD [0001] The present invention relates to a conductive fine particle, a conductive fine particle, a conductive resin composition, a conductive sheet, and an electromagnetic wave shielding sheet. BACKGROUND ART [0002]

The present invention relates to conductive fine particles and a manufacturing method thereof. The present invention also relates to a conductive resin composition containing the conductive fine particles. The present invention also relates to a conductive sheet and an electromagnetic wave shielding sheet having a conductive layer formed of the conductive resin composition.

BACKGROUND ART [0002] Printed wiring boards are becoming thinner as electronic apparatuses such as cellular phones and digital cameras are made smaller, and flexible printed wiring boards are in widespread use. A conductive sheet, an electromagnetic wave shielding sheet or the like (hereinafter also referred to as "conductive sheet or the like") is generally used for the printed wiring board. Conductive sheets and the like are required to have excellent conductive properties including stability over time, and the properties of the conductive filler contained in the sheet are important.

As the conductive filler, silver is excellent in conductive characteristics, and a conductive sheet containing silver in the meantime has been practically used. However, the price of silver is expensive and expensive compared with resins and other materials used for conductive sheets. In addition, prices are rising nowadays, and the price rise of conductive sheets using silver powder is a serious problem. In order to attain a reduction in the cost of electronic devices, it is necessary to reduce the use proportion of the conductive filler. However, there is a problem that the required conductivity can not be maintained if the use proportion of the conductive filler is reduced.

Thus, various proposals have been made in order to realize the cost while satisfying the conduction characteristics. For example, in Patent Document 1, there has been proposed a method of improving adhesion to an adherend while reducing the amount of the conductive filler by using the flake-like (scaly) silver powder as shown in Fig. In Patent Document 2, silver coated copper powder obtained by plating silver on the copper surface is disclosed as the conductive particles used for such a sheet. In Patent Document 3, a conductive paste in which a silver-coated silver-coated copper powder and scaly flakes are mixed as conductive particles is disclosed.

Japanese Patent Application Laid-Open No. 11-86930 Japanese Patent Application Laid-Open No. 2002-75057 Japanese Patent Application Laid-Open No. 2009-230952

In the market of conductive sheets and the like, development of a sheet excellent in conduction characteristics is desired, while reducing the amount of expensive silver used to realize excellent conduction characteristics and low cost. In addition, there is a demand for a technique of thinning a conductive sheet or the like in order to respond to a demand for lightweight shortening. In the case where the conductive paste of Patent Document 3 is used as the conductive sheet, there is a problem that it is difficult to make the sheet thin because the silver-coated copper powder of the branch shape is mixed. This is because a part of the silver-coated silver-coated copper powder may protrude from the conductive layer and may penetrate the other layer or damage the other layer. In the above example, silver is used as the conductive particles, but the same problem may be caused when other conductive particles are used. Furthermore, although the conductive sheet or the like to be applied to the printed wiring board is mentioned, the same problem may occur with respect to the entire conductive sheet.

An object of the present invention is to provide a conductive fine particle which can be reduced in thickness and which can be made thin when a composition blended with a resin is formed in a sheet form.

As a result of intensive investigations by the present inventors, the inventors of the present invention have completed the present invention by finding what can solve the problems of the present invention in the following state. That is, the conductive fine particles according to the present invention comprise a core including a conductive material, and a coating layer covering the core and made of a conductive material different from the core, at least a part of which constitutes an outermost layer, ) Is 0.15 or more and 0.4 or less, and at least one of grooves and branch leaves is formed in the outer shape.

[Equation 1]

Coefficient of circle diameter = (area × 4π) / (circumference) ²

According to the present invention, it is possible to provide conductive fine particles which can be reduced in thickness and which are excellent in conduction characteristics and can be made thin, for example, when a composition blended with a resin is formed into a sheet.

As a result of intensive investigations by the present inventors, it has been surprisingly found that when the average value of the coefficient of circle diameter is within the above-mentioned range, the conductive fine particles are formed into leaf-like conductive fine particles containing at least one of grooves and branching leaves in the outer shape. In addition, there has been a problem that it is difficult to form thin films when tree-shaped conductive fine particles such as Patent Document 3 are mixed. However, according to the conductive fine particles of the present invention, the average value of the coefficient of circle diameter is within the above range, , It has been found that it can be thinned when it is kneaded into a composition to form a layer. Further, by using a conductive material different from the core and the covering layer, it is possible to increase the material selection and achieve cost reduction.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an electron micrograph showing an example of conductive fine particles having a groove or a branch of the present invention. FIG.
Fig. 2 is an electron micrograph of a flake-shaped silver powder.
Fig. 3 is an electron micrograph of a silver-coated silver-coated copper powder.
4 is a schematic view of a test sample for measuring a connection resistance value.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will now be described. It is needless to say that other embodiments are included in the scope of the present invention as long as they are consistent with the purpose of the present invention. In the present specification, numerical ranges specified by using "~ " include numerical values written before and after" ~ "in the range of lower limit and upper limit. In addition, the matters necessary for the practice of the present invention other than those specifically mentioned in this specification can be understood as design matters of a person skilled in the art based on the prior art in the field. The embodiments described below can be combined with each other preferably.

(Conductive Fine Particles) The conductive fine particles of the present invention are so-called core-shell type particles and include a core containing a conductive material and a coating layer covering at least a core and at least a part constituting the outermost layer, do. The covering layer should cover at least a part of the core, but it is preferable that the covering ratio is high in order to obtain better conduction characteristics. From the viewpoint of maintaining good conductivity characteristics, it is preferable that the average covering ratio by the covering layer is 60% or more, more preferably 70% or more, and more preferably 80% or more. The average coverage rate in the present specification refers to a value obtained by the same method as the following embodiment.

The conductive fine particles may be composed of only the core and the covering layer, but may include other layers. For example, a layer including an intermediate layer, a bonding layer, or the like for enhancing bonding between the core and the covering layer may be formed. The core, the coating layer, and the other layers may be independently composed of a single kind or may be composed of various kinds. In addition, other materials other than the conductive material may be kneaded in the core and the covering layer within a range not deviating from the object of the present invention.

In the conductive fine particles of the present invention, the average value of the coefficients of circle diameter obtained in the following formula (1) is 0.15 or more and 0.4 or less, and at least one of grooves and branch leaves is formed in the outer shape.

[Equation 1]

Coefficient of circle diameter = (area × 4π) / (circumference) ²

The unevenness degree (undulation degree) of the outer edge of the conductive fine particles can be grasped by the coefficient of circle diameter of the formula (1). A complete circle has a coefficient of 1 of the circle diameter, and the coefficient of the circle diameter is lowered as the shape of the concave and convex increases. That is, the coefficient of circle diameter is larger than 0 and smaller than 1. The circle diameter coefficient of the present specification was obtained by reading an electron microscope photograph (about 1,000 to 10,000 times) of the conductive fine particles using the analysis software of Mac-View Ver.4 (Mountaineck) I chose dogs. When selecting a leaf or flake-like particle, an entire particle shape not overlapping with each other can be identified, and an angle at which the plane plate becomes perpendicular from the observation point was extracted and selected. In the particle reference data, the average of the projected area circle diameter and the distribution of the volume distribution were set, and the average of 20 pieces of the circle diameter coefficient and the circular coefficient was calculated. In the equation (1), the area of the line forming the outer periphery when projected in two dimensions is the flat surface, and the outer periphery of the conductive fine particles when the flat surface is projected in two dimensions is the length of the peripheral length do.

By using the core-shell type conductive fine particles using the core having an average value of the coefficients of circle diameter obtained in the above-mentioned formula (1) of not less than 0.15 and not more than 0.4 and using at least one of grooves and branch foliage in the outer shape, Can be reduced, excellent in conductive characteristics, and can be made thinner. The lower limit value of the coefficient of circle diameter coefficient is more preferably 0.15 or more and more preferably 0.20 or more from the viewpoint of prevention of the occurrence of the breakage of the conductive filler with respect to the insulating layer. Further, the upper limit value of the coefficient of circle diameter is more preferably 0.4 or less from the viewpoint of the sheet resistance of the conductive layer, and more preferably 0.3 or less. It is preferable that the average value of the circle diameter coefficient and the average value of the circular coefficient exist in about 10 or more particles defined per 1 cm 2.

The coefficient of circle diameter of the branch-shaped conductive fine particles as shown in Fig. 3 is generally 0.11 or less, and the coefficient of circle diameter of the flaky conductive fine particles is more than 0.4 and less than 0.5.

In the conductive fine particles of the present invention, it is preferable that the average value of the circular coefficient indicating the degree of circle obtained from the following formula (2) is 2 or more and 5 or less.

&Quot; (2) "

Circular coefficient = (maximum diameter x maximum diameter x pi) / (4 x area)

Where the maximum diameter is the length of the maximum length of the selected particles. When the circular coefficient is in the above range, the effect that the conductivity is further improved is obtained. From the viewpoint of preventing breakage of the conductive filler with respect to the insulating layer, the more preferable upper limit value of the circular coefficient is 4.5 or less, and more preferably 4.0 or less. Further, the lower limit value of the circular coefficient is more preferably 2 or more, more preferably 2.4 or more, from the viewpoint of the sheet resistance of the conductive layer. It is possible to know whether the shape of the entire fine particles by the circular coefficient is close to a circle (the smaller the value, the closer the circle is). Also, the roundness coefficient is the shape coefficient 3 using the analysis software (Mac-View Ver.4) used in the circle diameter coefficient.

The conductive fine particles of the present invention are, in other words, leaf-like conductive fine particles having at least one of grooves and branches. Fig. 1 shows an electron microscope image showing an example of the conductive fine particles according to the present invention. In this drawing, copper is used as a nucleus and silver is used as a covering layer. As shown in this figure, the conductive fine particles have at least one of a groove and a branch leaf formed in an outer peripheral shape thereof. In other words, a plurality of grooves, branches, or similar shapes are formed. Hereinafter, the conductive fine particles of the present invention are also referred to as "leaf-shaped conductive fine particles ".

The thickness of the conductive fine particles is preferably 0.1 to 2 占 퐉, more preferably 0.2 to 1 占 퐉. And the thickness is in the range of 0.1 to 2 占 퐉 so that it can be made thinner while maintaining the conductivity of the conductive sheet. In addition, the thickness is obtained based on an image enlarged to about 50 to 50,000 times by an electron microscope, and the term "thickness" used herein means that about 10 to 20 different particles are measured in an electron microscope image 10,000 times, did.

The average particle diameter (D50) of the conductive fine particles is preferably 1 to 100 mu m. The average particle diameter (D50) is in the range of 1 to 100 mu m, which further improves the conductivity and further improves the solution stability when the conductive resin composition is blended with, for example, a resin. The average particle diameter (D50) of the conductive fine particles is more preferably 3 m or more and more preferably 50 m or less. The average particle size (D50) was obtained by measuring each conductive fine particle in a tornado dry powder sample module using a laser diffraction scattering method particle size distribution measuring device LS 13 320 (manufactured by Beckman Coulter Co.). The particle size was 50% The average particle size of the particle diameter. The refractive index was set at 1.6.

The average particle diameter (D50) when the conductive fine particles were in the form of a conductive sheet was measured by SEM observation of the conductive fine particles under the same conditions as the method of measuring the coefficient of circle diameter, and the image analysis software Mac-View Ver. 4 (manufactured by MOUNTAX CORPORATION), and the average particle size (D50) is determined by setting the diameter of the projected area circle corresponding to the particle reference data and the volume distribution of the distribution.

The core serves as the core portion of the conductive fine particles. The core is preferably composed of only a conductive material from the viewpoint of improving conduction characteristics, but it may contain a non-conductive material. The raw material for the core is not particularly limited as long as it satisfies these requirements, but examples thereof include a conductive metal, a conductive carbon, and a conductive resin. The conductive metal is, for example, gold, platinum, copper nickel, aluminum, iron or an alloy thereof, or ITO. Copper is preferable in terms of price and conductivity. Examples of the conductive carbon include acetylene black, ketjen black, furnace black, carbon nanotube, carbon nanofiber, graphite, and graphene. In the case of the conductive resin, poly (3,4-ethylenedioxythiophene), polyacetylene and polythiophene are preferable. It is preferable that the core itself has conductivity.

The covering layer is made of a conductive material different from the core. Conductive materials usable for the coating layer can be exemplified by substances listed in the core. Among them, the use of a material having a high conduction characteristic is in accordance with the object of the present invention. Specifically, gold, platinum or silver is preferable, and silver is particularly preferable. Conductive materials other than metals, such as conductive resins, are low in conductivity in the present technology, but conductive resins and the like are also preferable as the covering layer as the technology advances and the conductivity is improved. It is preferable to use a conductive material having excellent conduction characteristics for the coating layer and a conductive material having a cost advantageous to the nucleation layer from the viewpoint of achieving both cost reduction and improvement in conduction characteristics. Further, a conductive intermediate layer can be provided between the core and the covering layer.

The coating layer is preferably coated at a ratio of 1 to 40 parts by weight with respect to 100 parts by weight of the core, more preferably 5 to 30 parts by weight, still more preferably 5 to 20 parts by weight. By using the covering layer in the range of 1 to 40 parts by weight, it is possible to draw the conductive characteristic while reducing the amount of the conductive material used as the covering layer. For example, when copper is used as the core and silver is used as the covering layer, the cost of the conductive fine particles can be effectively reduced while maintaining the conductive property.

According to the conductive fine particles of the present invention, when the average value of the coefficient of circle diameter is within the above-mentioned range, the conductive fine particles are formed into a leaf-like conductive fine particle containing at least one of grooves and branch leaves in the outer shape. This makes it possible to increase the contact points of the conductive fine particles in the layered state by increasing the irregularities of the particles and by forming the outline shape of the particles in the shape of a leaf including at least one of grooves and branching leaves, I think that it was possible to do. Further, according to the conductive fine particles having a branch shape, there is a problem that it is difficult to form a thin film. However, according to the conductive fine particles of the present invention, it is possible to easily make a thin film. This is because it is more flattened than the branches. It is also possible to increase material choice and achieve cost savings by using different conductive materials between the core and the coating layer.

Further, the conductive fine particles of the present invention are core shell type, but excellent conductivity and thinning can be achieved even when particles having a coefficient of circle diameter and outer shape are produced from a single conductive material. Therefore, when the price of silver or the like is lowered, solving the problem of cost reduction is useful in a single conductive material. The use of copper also has the problem of degradation of conductivity due to oxidation, but it is also useful in a single conductive material if the conductivity characteristics of the development of antioxidant technology remain good.

(Method for Producing Conductive Fine Particles) The method for producing conductive fine particles of the present invention is a method for producing conductive fine particles comprising a core containing a conductive material and a coating layer formed of a conductive material which covers the core and is different from the core, And a method for producing the conductive fine particles. The method comprising the steps of preparing a solid medium for deforming the twig shaped fine particles by colliding with the twig shaped fine particles having more electric conductivity and collision with the twig shaped fine particles and a step of colliding the twig shaped fine particles and the solid medium in a hermetically sealed container And a step of deforming the branch-like fine particles so that a plurality of the grooves and the branching leaves are formed in the outer shape with a coefficient of circle diameter obtained by the following formula (1) is 0.15 or more and 0.4 or less.

[Equation 1]

Coefficient of circle diameter = (area × 4π) / (circumference) ²

Hereinafter, preferred examples for implementing the method for producing conductive fine particles of the present invention will be described. However, the present invention is not limited to the following production methods, but various production methods are possible.

The method for producing conductive fine particles according to the present invention comprises a step of preparing a solid medium for deforming the branch-like fine particles by colliding the branch-like fine particles having conductivity with the branch-like fine particles (Step 1) And a step of deforming the branch-shaped fine particles by colliding the solid medium with each other in the closed vessel (step 2).

In step 1, the twig shaped particles prepare particles having a so-called twig shape (dendritic shape) as shown in FIG. The branch-like fine particles may be preferably non-leaf-shaped conductive fine particles which are precursors of leaf-shaped conductive fine particles comprising a core and a coating layer, and may also be twig shaped fine particles composed only of nuclei. In this case, a step of providing a coating layer on the core is performed in step 3 after the treatment in step 2.

The solid medium of step 1 is a solid medium having a coefficient of diameter of 0.15 or more and 0.4 or less as determined by the formula (1) by colliding the twig shaped microparticles with the twig shaped microparticles, wherein at least one of the groove and the branched leaf So long as the formed conductive fine particles can be obtained.

The solid medium is preferably made of metal such as iron, glass, zirconia, alumina, plastic, titania and ceramic. The closed container may be a well-known dispersing device such as a ball mill or a sand mill, or a pulverizer. The solid medium preferably has a spherical shape, an elliptical shape, and other shapes with less irregularities. The size of the solid medium is, for example, about 0.1 to 3 mm. The specific gravity of the solid medium is, for example, about 1.0 to 10.0.

In Step 2, the twig shaped fine particles and the solid medium are put into a closed container to collide the twig shaped fine particles with the solid medium. The solid particles collide with the branch-like fine particles, so that the branch-shaped fine particles are deformed to obtain, for example, leaf-like conductive fine particles as shown in Fig. During the production of the conductive particles, the solid medium may be impinged in the presence of the resin. Thus, the conductive resin composition described later can be produced simultaneously with the production of the conductive fine particles. The dispersion time and the collision condition for collision of step 2 are not particularly limited as long as the condition that the conductive fine particles of the characteristic can be obtained. For example, the dispersion time can be 10 minutes to 60 minutes.

When the conductive fine particles are produced, a thickener, a dispersant, a heavy metal deactivator and the like may be used as additives to the conductive fine particles. By using a thickener, excessive sedimentation of the fine particles can be suppressed. Examples of the thickening agent include silica-based compounds, polycarboxylic acid-based compounds, polyurethane-based compounds, urea-based compounds and polyamide-based ones. By using a dispersant, the dispersibility of the conductive fine particles is further improved. As the dispersing agent, for example, an acidic dispersing agent composed of a carboxylic acid and a phosphoric acid group, a basic dispersing agent containing an amine group, and a dispersing agent of a salt type neutralized with an acid base are mentioned.

By using a heavy metal deactivator, even when a metal ion is contained as an impurity, the conductivity is hardly inhibited. Examples of heavy metal deactivators include acetylacetone, carboxybenzotriazole compounds, hindered phenol compounds, hydrazine compounds, thiocarbazole compounds, salicylic acid imidazole compounds and thiadiazole compounds. A compound having a unit represented by the formula (1) (hereinafter referred to as "compound A") is a preferred example.

[Chemical Formula 1]

The amount of the compound A to be added is not limited to the range not deviating from the object of the present invention. However, the stability of the conductive resin composition, From the viewpoint of stability, it is preferable that the amount is not less than 0.1 parts by weight and not more than 30 parts by weight based on 100 parts by weight of the conductive fine particles. More preferably 0.5 part by weight or more from the viewpoint of improving the stability with time. From the viewpoint of cost reduction, 15 parts by weight or less is more preferable.

Compound A includes various compounds and is not particularly limited, and examples thereof include N-salicyloyl-N'-aldehydrazine, N, N-dibenzal (oxalhydrazide), isophoric acid bis (2- Amino-1,2,4-hydroxyphenyl) propionyl] hydrazine, a compound represented by the formula (2) (decamethylenecarboxylic acid disalicyloylhydrazine), 3- (N-salicyloyl) (N, N'-2 [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine) represented by the formula (3). Among them, the compounds of the formulas (2) and (3) are more preferable. By including them, a highly reliable conductive resin composition can be provided. The addition timing is not limited to the production of the conductive particles, and the conductive resin composition may be added after the conductive resin composition is mixed with the conductive particles after the production of the conductive particles.

(2)

(3)

An example of the production of silver coated copper powder as an example of the conductive fine particles will be described below.

[Preparation Example 1] First, a silver-coated silver-coated copper powder coated with silver is prepared on a copper powder. The silver coated copper powder is put into a sealed container together with the solid medium and the solid medium is collided with the silver coated copper powder in the closed container to transform the silver coated copper powder of the branch shape into the conductive fine particles of the present invention. The solid medium can collide with the branches of the silver-coated copper powder to obtain the conductive fine particles having the grooves or branches of the present invention, and at the time of applying the silver-coated copper powder, additives such as heavy metal deactivators and / A resin used for the conductive resin composition may be added. A conductive resin composition or an additive may be added to produce a conductive resin composition described later simultaneously with the production of the conductive fine particles.

[Preparation Example 2] First, a branch-shaped copper powder is prepared. This copper powder is put into a sealed container together with a solid medium, and the solid medium is impinged on the copper powder in the closed container to transform the branch-shaped copper powder into the conductive fine particles of the present invention. The solid medium collides with the branches of the copper powder to obtain a copper powder having grooves or branches. Then, silver is coated on the obtained copper powder having grooves or branching lines by a plating treatment to obtain the conductive fine particles having grooves or branches of the present invention.

(Conductive resin composition) Next, the conductive resin composition of the present invention will be described. The conductive resin composition of the present invention comprises the conductive particles and the resin of the present invention. The conductive resin composition of the present invention may contain conductive fine particles other than the conductive fine particles of the present invention within the range not deviating from the object of the present invention. However, from the viewpoint of improving the reliability, it is preferable that the conductive fine particles other than the conductive fine particles of the present invention are, for example, about 3 parts by weight or less based on 100 parts by weight of the resin.

As the resin used for the conductive resin composition, a thermoplastic resin or a curable resin can be used. The curable resin is preferably a thermosetting resin or a photocurable resin.

Examples of the thermoplastic resin include polyolefin resins, vinyl resins, styrene / acrylic resins, diene resins, terpene resins, petroleum resins, cellulose resins, polyamide resins, polyurethane resins, polyester resins, polycarbonate resins, , Fluororesin, and the like.

As the polyolefin-based resin, homopolymers or copolymers such as ethylene, propylene, and -olefin compounds are preferable. Specific examples thereof include polyethylene, ethylene propylene rubber, olefin thermoplastic elastomer and? -Olefin polymer.

The vinyl resin is preferably a copolymer obtained by polymerization of a vinyl ester such as vinyl acetate or a copolymer of a vinyl ester and an olefin compound such as ethylene. Specific examples thereof include ethylene-vinyl acetate copolymer, partially-blocked polyvinyl alcohol, and the like.

The styrene / acrylic resin is preferably a homopolymer or a copolymer composed of styrene, (meth) acrylonitrile, acrylamides, (meth) acrylic acid esters, maleimides and the like. Specific examples thereof include syndiotactic polystyrene, polyacrylonitrile, acrylic copolymer, ethylene-methyl methacrylate copolymer, and the like.

As the diene resin, homopolymers or copolymers of conjugated diene compounds such as butadiene and isoprene, and hydrogenated products thereof are preferable. Specific examples thereof include styrene-butadiene styrene-isoprene block copolymer and the like.

The terpene resin is preferably a polymer composed of terpenes or a hydrogenated product thereof. Specifically, for example, a terpene resin and a hydrogenated terpene resin are listed.

The petroleum resin is preferably a dicyclopentadiene type petroleum resin or a hydrogenated petroleum resin.

The cellulose-based resin is preferably a cellulose acetate butyrate resin.

The polycarbonate resin is preferably a bisphenol A polycarbonate.

The polyimide-based resin is preferably a thermoplastic polyimide, a polyamide-imide resin, or a polyamic acid-type polyimide resin.

The thermosetting resin is a functional group which can be used for a crosslinking reaction upon heating such as a hydroxyl group, a phenolic hydroxyl group, a methoxymethyl group, a carboxyl group, an amino group, an epoxy group, an oxetanyl group, an oxazoline group, an oxazine group, an aziridine group, , An isocyanate group, a blocked isocyanate group, a blocked carboxyl group, a silanol group and the like in one molecule, and examples thereof include acrylic resin, maleic acid resin, polybutadiene resin, polyester resin, polyurethane resin, epoxy Examples of the resin include resins, oxetane resins, phenoxy resins, polyimide resins, polyamide resins, phenol resins, alkyd resins, amino resins, poly lactic acid resins, oxazoline resins, benzoxazine resins, silicone resins, have. The thermosetting resin of the present invention may contain a so-called "curing agent" such as a resin or a low-molecular compound that reacts with the above-mentioned functional group to form a chemical crosslink in addition to the above-mentioned resin.

The photocurable resin may be a resin having at least one unsaturated bond which causes a crosslinking reaction by light, and examples thereof include acrylic resin, maleic resin, polybutadiene resin, polyester resin, polyurethane resin, epoxy Examples of the resin include resins, oxetane resins, phenoxy resins, polyimide resins, polyamide resins, phenol resins, alkyd resins, amino resins, poly lactic acid resins, oxazoline resins, benzoxazine resins, silicone resins, have.

The conductive resin composition is preferably blended with 50 to 500 parts by weight of conductive fine particles per 100 parts by weight of the resin, more preferably 100 to 400 parts by weight. By mixing the conductive fine particles in an amount of 50 to 500 parts by weight, the conductivity is further improved, and the conductive layer can be further formed.

The conductive resin composition may contain, in addition to the conductive particles and the resin, the metal deactivating agent, the thickening agent and the like, as well as the dispersant, the silane coupling agent, the rust inhibitor, the antifouling agent, the reducing agent, the antioxidant, An ultraviolet absorber, an extinguishing agent, a leveling agent, a filler, and a flame retardant.

The conductive resin composition can be obtained by putting the silver-coated silver powder and the resin simultaneously before the conductive fine particles are produced as described above, and colliding the solid medium. It can also be obtained by mixing conductive fine particles with a resin after the production thereof. When the resin is mixed into the dispersion, a method of adding the resin while mixing the dispersion in the dispersion mat may be exemplified.

(Conductive Sheet) The conductive sheet of the present invention is provided with a conductive layer formed of the conductive resin composition of the present invention. The method for producing the conductive sheet is not particularly limited, and for example, a method of coating the conductive resin composition on the releasable sheet to form the conductive layer can be exemplified. The conductive sheet may be a single layer of a conductive layer, but may also be a laminate of other functional layers and supporting layers. The functional layer is a layer having insulating properties, thermal conductivity, electromagnetic wave absorptivity, hard coat property, water vapor barrier property, oxygen barrier property, low dielectric constant, high dielectric constant, low dielectric tangent . When the conductive sheet of the present invention is used in the field of printed wiring boards, it is preferable to include a thermosetting resin in view of heat resistance.

The conductive sheet of the present invention can be used in various applications without limitation, but suitable examples include anisotropically conductive sheets, electrostatic elimination sheets, sheets for gland connection, membrane circuits, conductive adhesive sheets, heat conductive sheets, conductive sheets for jumper circuits, .

The coating method can be applied to various coating methods such as gravure coating method, kiss coating method, die coating method, lip coating method, comma coating method, blade method, roll coating method, knife coating method, spray coating method, bar coating method, A dip coating method or the like can be used.

The thickness of the conductive layer in the conductive sheet is preferably 1 to 100 mu m, more preferably 3 to 50 mu m. Since the thickness is in the range of 1 to 100 mu m, conductivity and other physical properties are easily compatible.

(Electromagnetic wave shielding sheet) The electromagnetic wave shielding sheet of the present invention is provided with a conductive layer formed of the conductive resin composition of the present invention and an insulating layer, and can be used for shielding electromagnetic waves generated in a circuit. The method for producing the electromagnetic wave shielding sheet is not particularly limited, but as an example, a method of aligning the conductive layer and the insulating layer manufactured by the above method can be exemplified. As the insulating layer, a previously made insulating film may be used. Alternatively, an insulating layer may be formed by coating an exfoliating sheet with an insulating resin composition, and the conductive layer having the releasable sheet adhered thereto. Alternatively, the insulating layer may be formed by directly coating the insulating resin composition on the conductive layer.

The thickness of the insulating layer may vary depending on the application and the necessity. For example, when used for a flexible printed wiring board, the thickness of the insulating layer is preferably 2 to 10 mu m from the viewpoint of enhancing the shielding effect of the electromagnetic shielding sheet while maintaining flexibility. The thickness of the insulating layer is preferably 50 to 200 when the thickness of the conductive layer is 100. As a result, the balance of various physical properties becomes easy to obtain.

The insulating film material is not particularly limited, but a plastic film such as polyester, polycarbonate, polyimide, and polyphenylene sulfide may be used. Alternatively, a film formed by molding an insulating resin composition may be used.

Although the insulating resin composition contains a resin as an essential component, it is preferable to use a resin that can be used for the conductive layer. In addition, a silane coupling agent, an antioxidant, a pigment, a dye, a dispersant, a tackifier resin, a plasticizer, an ultraviolet absorber, an extinguishing agent, a leveling regulator, a filler and a flame retardant may be mixed with the insulating resin composition.

The electromagnetic wave shielding sheet of the present invention may have other layers besides the conductive layer and the insulating layer. The other layer is, for example, a layer having hard coat property, thermal conductivity, heat insulating property, electromagnetic wave absorptivity, water vapor barrier property, oxygen barrier property, low permittivity, high dielectric constant, low dielectric loss tangent, When the electromagnetic wave shielding sheet of the present invention is used in the field of printed wiring boards, it is preferable to include a thermosetting resin from the viewpoint of heat resistance.

The electromagnetic wave shielding sheet of the present invention can be used as an electromagnetic wave shielding layer by adhering to a flexible printed substrate, a rigid printed substrate, a rigid flexible substrate or the like by heating and pressing, or can be directly attached to an electronic component. The printed wiring board into which the electromagnetic wave shielding sheet of the present invention is put can be used for various applications such as a mobile phone such as a smart phone, a computer, a tablet terminal, an LED light, an organic EL light, a liquid crystal TV, an organic EL TV, a digital camera, It can be used for vehicle parts.

≪ Embodiment >

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. In the following, "part" and "%" are values based on "parts by weight"

Table 1 shows non-leaf conductive fine particles used as a raw material. Silver-coated silver powder of conductive fine particles 1 to 7 was made by Mitsui Kikuko Kogyo Co., Further, the branch-shaped copper powder of the conductive fine particles 8, the spherical silver-coated copper powder of the conductive fine particles 9, and the flaky silver powder of the conductive fine particles 11 were manufactured by Fukuda Metal & The silver coated copper powder in the form of flakes of the conductive fine particles 10 was a product of Mitsui Kikuko Kogyo Co., Ltd. The average particle size (D50) of the conductive fine particles as raw materials was calculated by a laser diffraction / scattering method particle size distribution measuring device LS 13 320 (manufactured by Beckman Coulter, Inc.).

Non-leaf-shaped
Conductive fine particles Nucleus
Coating layer shape Average particle diameter
(D50) (占 퐉) Kinds Weight portion Coverage% One

Copper

silver



5 95.2

Twig shape



9.3 2 10 100 9.6 3 20 100 9.9 4 30 100 10.3 5 40 100 10.0 6 10 100 2.9 7 10 100 21.3 8 (Comparative Example?)
Copper
none - Twig shape 9.9 9 (Comparative Example?) silver
10 100 Sphere shape 20.5 10 (Comparative Example?) 10 100 Flake shape 18.5 11 (Reference Example I) silver none - Flake shape 10.6

Weight of coating layer: Value for 100 parts by weight of nucleus

≪ Example A (Production of conductive fine particles) >

100 parts of the non-leaf shaped conductive fine particles 1 shown in Table 1, 400.0 parts of toluene, 10.0 parts of a thickener (AEROSIL R972 manufactured by Aero Chemical Company, Japan) and 10.0 parts of a heavy metal deactivator (decamethylcarboxylic acid disalityl) Hydrazide) in an amount of 1.0 part, and the mixture was homogeneously mixed and stirred. Subsequently, this was added to Eiger Mill (product of Eiger Japan Co., Ltd., "Mini Model M-250 MKII") together with zirconia beads having a diameter of 0.5 mm and dispersed for 10 minutes. The obtained fine particles were decanted 5 times with methyl ethyl ketone. Further, by drying in an oven at 100 캜, leaf-shaped conductive fine particles of Example A were obtained. The average particle diameter (D50), thickness, circle diameter coefficient and circularity coefficient of the leaf-shaped conductive fine particles relating to Example A were measured. The average particle diameter (D50) and the thickness were obtained by the above method. In addition, the raw diameter coefficient and the circular coefficient were calculated by the above-described method by preparing a sample in the following manner. The thickness average particle diameter (D50), the circle diameter coefficient, the circular coefficient, and the coverage ratio of the conductive fine particles of the obtained leaves are shown in Table 2.

≪ Round Diameter Coefficient and Circular Coefficient > As a sample to be measured, a sample using the corresponding conductive fine particles was prepared by a manufacturing method of an electromagnetic wave shielding sheet to be described later. Then, a sample of 1 cm 2 was fixed to a columnar sample bed for SEM through a conductive adhesive. Specifically, the separator on the conductive layer side of the electromagnetic wave shielding sheet was peeled off, and the conductive layer was fixed to the sample table so that the upper layer and the insulating layer were the lower layer. Then, a conductive paste was applied on the conductive layer of the electromagnetic wave shielding sheet to perform platinum deposition. After the deposition, SEM images of the conductive particles were obtained under the conditions of 1000 times and an acceleration voltage of 15 kV and analyzed by the above method.

<Coverage> A double-sided adhesive tape was attached to a special pedestal, each metal particle powder was dropped on a double-sided adhesive tape, and then extra powder was blown off with air. And five different points were measured by an X-ray photoelectron spectrometer (ESCA AXIS-HS, manufactured by Shimadzu Corporation). The average value of the mass concentration% of the coating layer (silver) calculated from the peak area of the coating layer (silver) and the core (copper) by the analysis software (manufactured by Kratos) was regarded as the covering ratio of silver.

&Lt; Examples B to K, Comparative Example? (Production of conductive fine particles)

Conductive fine particles were produced in the same manner as in Example A except that the dispersion treatment time using the raw material of the non-leaf shaped conductive fine particles and the Eiger mill was changed as described in Table 2. [

Leaf-shaped conductive fine particles Conductive fine particles Non-leaf shaped conductive fine particles Dispersion
time
(minute) thickness
(탆) Average particle diameter
(D50)
(탆) won
Diameter coefficient Circular coefficient silver
Coverage rate
% Example
Example
Example
Example
Example
Example
Example
Example
Example
Example
Example
Comparative Example A One 10 0.43 19.7 0.19 2.85 78.5 B 2 10 0.54 20.5 0.21 3.18 95.6 C 3 10 0.42 21.2 0.19 2.86 99.8 D 4 10 0.45 20.1 0.24 3.06 100 E 5 10 0.66 20.0 0.17 3.15 100 F
2

120 0.05 19.0 0.37 2.58 72.2 G 60 0.10 19.6 0.25 2.66 81.9 H 5 1.90 20.0 0.18 2.61 98.1 I One 2.59 18.3 0.12 3.02 100 J 6 10 0.64 5.9 0.27 3.10 92.2 K 7 10 0.43 54.3 0.22 2.99 96.3 δ 8 10 0.44 20.0 0.22 2.82 -

&Lt; Examples 1 to 20, Comparative Examples 1 to 4 and Reference Example 1 (Production of conductive resin composition)

The raw materials shown in Table 3 were placed in a container and stirred in a disperser for 5 minutes to obtain conductive resin compositions of Examples 1 to 20, Comparative Examples 1 to 4, and Reference Example 1.

Polyamideimide resin (Toyochem), polyester (condensation type polyester) (Toyo Kensha Co., Ltd.) and addition type polyester (Toyochem Co., Ltd.) are used as the urethane of the base resin, polyurethane resin Respectively. 10 parts of a curing agent (aziridine compound) was used per 100 parts by weight of the base resin.

Conductivity
Composition Conductivity
Particulate Base resin Epoxy
Hardener
Amount of blending Toluene / IPA =
8/2
Amount of blending Conductivity
Particulate
Amount of blending additive
A additive
B Kinds Amount of blending









Example







One









Example





A









urethane







22








6.80









41.20









300














none
















none







2 B 3 C 4 D 5 E 6 F 7 G 8 H 9 I 10 J 11 K 12



B



70 21.72  0  25 13 59 18.13  9.86  50 14 15  4.53 47.46 500 15 11  3.89 51.05 600 16 amides


22



6.80



41.20



300
17 Condensation type
Polyester 18 Additive type
Polyester 19 urethane
10 20 none 10
Comparative Example

One
Comparative Example

alpha
urethane


22


6.80


41.20


300


none


none

2 beta 3 gamma 4 δ Reference example One Reference example I urethane 22  6.80 41.20 300 none none

Additive A: decamethylenecarboxylic acid disalicyloyl hydrazide

Additive B: N, N'-2 [3- (3,5-diacetyl-4-hydroxyphenyl) propionyl] hydrazine

Formulation amount: parts by weight

<Preparation of Conductive Sheet of Example 1>

The conductive resin composition of Example 1 was coated on a peelable sheet of polyethylene terephthalate using a bar coater to a dry thickness of 5 탆 and dried in an electric oven at 100 캜 for 2 minutes to obtain a conductive sheet C1 having a conductive layer .

<Manufacture of Electromagnetic Wave Shielding Sheet of Example 1>

A thermosetting urethane resin (manufactured by Toyochem Co., Ltd.) was applied to a peelable sheet of polyethylene terephthalate using a bar coater so as to have a dry thickness of 5 탆 and dried in an electric oven at 100 캜 for 2 minutes to obtain an insulating layer. The conductive layer of the conductive sheet C1 and the electric insulating layer were superposed and thermally bonded to each other at 80 DEG C under a pressure of 2 MPa to obtain an electromagnetic wave shielding sheet E1.

<Preparation of Conductive Sheet of Examples 2 to 20, Comparative Examples 1 to 4 and Reference Example 1>

Conductive sheets C2 to C20 were obtained in the same manner as in Example 1, except that the conductive resin compositions of Examples 2 to 20 were used instead of the conductive resin compositions of Example 1. Conductive sheets C21 to C25 were obtained in the same manner as in Example 1 except that the conductive resin compositions of Comparative Examples 1 to 4 and Reference Example 1 were used instead of the conductive resin composition of Example 1.

<Preparation of Electromagnetic Wave Shielding Sheet of Examples 2 to 20, Comparative Examples 1 to 4 and Reference Example 1>

Electromagnetic wave shielding sheets E2 to E25 were obtained in the same manner as in Example 1 except that the conductive sheet described in Table 4 was used in place of the conductive sheet 1.

Electromagnetic wave shielding sheets E2 to E20 were obtained in the same manner as in Example 1 except that the conductive resin compositions of Examples 2 to 20 were used instead of the conductive resin composition of Example 1. Electromagnetic shielding sheets E21 to E25 were obtained in the same manner as in Example 1, except that the conductive resin composition of Comparative Example 1 to 4 and Reference Example 1 was used instead of the conductive resin composition of Example 1.

Conductive sheet Electromagnetic wave shielding sheet









Example







One C1 E1 2 C2 E2 3 C3 E3 4 C4 E4 5 C5 E5 6 C6 E6 7 C7 E7 8 C8 E8 9 C9 E9 10 C10 E10 11 C11 E11 12 C12 E12 13 C13 E13 14 C14 E14 15 C15 E15 16 C16 E16 17 C17 E17 18 C18 E18 19 C19 E19 20 C20 E20
Comparative Example

One C21 E21 2 C22 E22 3 C23 E23 4 C24 E24 Reference example One C25 E25

&Lt; Measurement of connection resistance value >

The conductive sheet 10 was cut to a length of 25 mm and a width of 25 mm and was fixed to the end of a stainless steel plate 11 having a width of 25 mm, a length of 100 mm and a thickness of 0.5 mm and temporarily bonded by thermocompression bonding at 80 캜 and 2 MPa. Thereafter, the peelable sheet was peeled off, and the stainless steel plates 12 of the same size were superimposed in the same manner as above, and temporarily adhered by thermocompression bonding at 80 DEG C and 2 MPa. The specimens for measuring the connection resistance shown in FIG. 4 were obtained by thermocompression bonding at 150 DEG C and 2 MPa for 30 minutes. The connection resistance value was measured by using this specimen and bringing the BSP probe of "Loresta GP" manufactured by Mitsubishi Kagaku Analytec Co., Ltd. into contact with the B side of the stainless steel plate 11 and the A side of the stainless steel plate 12 as shown in Fig. The evaluation criteria are as follows.

A: less than 1.0 x 10 ^-3

B: 1.0 x 10 ^-3 or more and less than 1.0 x 10 ^-2

C: 1.0 × 10 ^-2 or more than 1.0 × 10 ^-1

D: 1.0 x 10 &lt; ^-1 &gt;

&Lt; Measurement of surface resistance value &

The surface resistance value of the conductive layer of the obtained electromagnetic wave shielding sheet was measured by using a 4-probe probe "Loresta GP" manufactured by Mitsubishi Kagaku Analytec. The evaluation criteria are as follows.

A: less than 1.0

B: 1.0 to less than 10.0

C: 10.0 or more and less than 50.0

D: 50.0 or higher

On the other hand, the surface resistance value of the insulating layer of the electromagnetic shielding sheet was measured using a ring probe URS of "Hirestor UP" manufactured by Mitsubishi Kagaku Analytec. The evaluation criteria are as follows.

A: 1 x 10 ⁷ or more

B: less than 1 占⁰⁷ , more than 1 占⁰⁶

C: less than 1 x 10 ^{6, not} less than 1 x 10 ⁴

D: less than 1 x 10 ⁴

<Measurement of Adhesive Force>

An electromagnetic wave shielding sheet having a width of 25 mm and a length of 70 mm was prepared. The peelable film in contact with the conductive layer was peeled off and a polyimide film ("Kaff Tong 200 EN" manufactured by Toray DuPont) having a thickness of 50 m was pressed on the exposed conductive layer under the conditions of 150 ° C and 1.0 MPa for 30 minutes, The insulating layer was cured. For the purpose of reinforcing the electromagnetic shielding sheet for measurement, a peelable film in contact with an insulating layer having a thickness of 50 mu m was removed and an adhesive sheet using a polyurethane polyurea adhesive was applied to the exposed insulating layer. A polyimide film Quot; CAP Tong 200EN ") was pressed at 150 DEG C under 1 MPa for 30 minutes. Through these processes, specimens of "polyimide film / electromagnetic shielding sheet / adhesive sheet / polyimide film" were obtained. The adhesive force was measured by peeling the interface between the conductive layer and the polyimide film at an annealing temperature of 23 ° C and a relative humidity of 50% at a tensile rate of 50 mm / min and a peeling angle of 90 °.

A: 8N / 25mm or more

B: Less than 8N / 25mm, 6N / 25mm or more

C: Less than 6N / 25mm, 3N / 25mm or more

D: Less than 3N / 25mm

Conductive sheet Electromagnetic wave shielding sheet Connection resistance
[Ω / 25 mm] Sheet resistance [Ω / □] Adhesion [N / 25 mm] Conductive layer Insulating layer Early depreciation









Example







One 6.7 x 10 ^-3 B    1.10 B 5.4 × 10 ⁷ A 8.95 A 7.12 B 2 7.3 × 10 ^-4 A    0.53 A 5.7 x 10 ⁸ A 7.68 B 6.21 B 3 7.9 × 10 ^-4 A    0.42 A 7.3 × 10 ⁸ A 8.42 A 6.83 B 4 5.1 x 10 ^-4 A    0.16 A 7.2 x 10 ⁸ A 8.67 A 6.01 B 5 5.5 × 10 ^-4 A    0.29 A 6.5 × 10 ⁸ A 9.45 A 6.89 B 6 4.0 x 10 ^-2 C   11.25 C 3.6 × 10 ⁷ A 9.17 A 6.45 B 7 7.3 × 10 ^-3 B    1.89 B 3.5 × 10 ⁸ A 8.47 A 7.00 B 8 1.4 x 10 ^-4 A    0.15 A 1.9 × 10 ⁶ B 8.25 A 6.54 B 9 6.5 × 10 ^-4 A    0.84 A 8.4 × 10 ⁴ C 7.55 B 6.53 B 10 1.3 x 10 ^-3 B    0.14 A 5.5 × 10 ⁸ A 6.08 B 6.08 B 11 1.1 × 10 ^-4 A    0.35 A 6.0 × 10 ⁸ A 6.39 B 5.08 C 12 2.1 x 10 ^-2 C   22.58 C 3.7 × 10 ⁸ A 9.35 A 6.83 B 13 2.0 x 10 ^-3 B    8.55 B 2.7 × 10 ⁸ A 9.73 A 6.93 B 14 3.1 × 10 ^-4 A    0.14 A 4.7 × 10 ⁶ B 6.93 B 5.28 C 15 3.7 × 10 ^-4 A    0.23 A 9.6 × 10 ⁵ C 3.52 C 3.10 C 16 3.9 × 10 ^-4 A    0.76 A 6.5 × 10 ⁶ B 3.90 C 3.33 C 17 2.4 × 10 ^-4 A    0.60 A 7.0 × 10 ⁶ B 5.89 C 4.89 C 18 6.7 × 10 ^-4 A    0.81 A 5.1 × 10 ⁶ B 5.27 C 4.39 C 19 6.3 × 10 ^-4 A    0.53 A 5.7 x 10 ⁸ A 8.90 A 8.80 A 20 5.6 × 10 ^-4 A    0.53 A 5.7 x 10 ⁸ A 9.00 A 8.90 A
Comparative Example

One 1.2 D  189.00 D 5.0 × 10 ² D 6.60 B 5.64 C 2 2.0 x 10 D  210.00 D 4.1 x 10 ² D 1.13 D - - 3 2.0 x 10 ³ D 2356.0 D 8.7 x 10 ⁸ A 9.45 A 6.97 B 4 5.1 x 10 ² D  571.0 D 6.3 × 10 ⁸ A 9.17 A 5.28 C Reference example One 4.9 × 10 ^-4 A    0.48 A 6.7 x 10 ⁸ A 8.07 A 6.97 B

[Note] This specification also discloses the inventions of technical ideas described below that are grasped in the above embodiments.

(Annex 1)

A conductive fine particle in the form of a leaf having a conductive nucleus coated with a conductive material different from the nucleus and having a plurality of grooves or branches.

(Annex 2)

Characterized in that the solid medium comprises a step of obtaining fine particles of leaves having a plurality of grooves or branching leaves by deforming the branchlike conductive fine particles by colliding with conductive fine particles coated with silver on the conductive fine particles, A method for producing conductive fine particles.

(Annex 3)

A conductive fine particle having a coefficient of circle diameter obtained by the following formula (1) is 0.15 or more and 0.4 or less, and at least one of grooves and branch foliage is formed in an outline shape.

[Equation 1]

Coefficient of circle diameter = (area × 4π) / (circumference) ²

This application claims priority based on Japanese Patent Application No. 2012-49680, filed on March 6, 2012, including all disclosures therein.

Industrial availability

The conductive fine particles of the present invention can be used for various purposes as a filler requiring conductivity characteristics. Preferably, the conductive particles of the present invention and the conductive resin composition containing the resin can be used for various purposes. For example, a conductive layer can be formed of a conductive resin composition and used as a conductive sheet and an electromagnetic wave shielding sheet. The conductive sheet can be used, for example, for electrical connection between circuits. The conductive sheet or the electromagnetic shielding sheet of the present invention is suitable, for example, for a flexible printed wiring board, a rigid printed wiring board, a metal plate and a flexible connector which are subjected to repeated bending.

10: Sample
11, 12: Stainless steel plate

Claims (12)

A core including a conductive material,
A coating layer covering the core and made of a conductive material different from the core, at least a part of which forms the outermost layer,
A conductive fine particle having a coefficient of circle diameter determined by the following formula (1) of not less than 0.15 and not more than 0.4 and having at least one of grooves and branch foliage in an outer shape:
[Equation 1]
Coefficient of circle diameter = (area × 4π) / (circumference) ² The conductive fine particle according to claim 1, wherein the covering layer is 1 part by weight or more and 40 parts by weight or less based on 100 parts by weight of the core. 3. The conductive fine particle according to claim 1 or 2, wherein the thickness is 0.1 mu m or more and 2 mu m or less. 3. The conductive fine particle according to claim 1 or 2, wherein the coating layer is silver. A conductive resin composition comprising the conductive particles according to any one of claims 1 to 4 and a resin. 6. The method of claim 5,
A conductive resin composition comprising a compound having a unit represented by the following formula (1)
[Chemical Formula 1]

The method according to claim 6,
Wherein the formula (1) comprises at least one of the following formula (2) and the following formula (3):
(2)

(3)

A conductive sheet having a conductive layer formed of the conductive resin composition of claim 5 or 6. An electromagnetic wave shielding sheet comprising a conductive layer formed from the conductive resin composition of claim 5 or 6, and an insulating layer. A core including a conductive material,
In a method for producing conductive fine particles which are formed of a conductive material which is different from the core material and covers at least part of the core material and which has a covering layer constituting the outermost layer,
Preparing a solid medium for deforming the branch-shaped fine particles by colliding the branch-shaped fine particles having conductivity with the branch-shaped fine particles;
Wherein the knife-like fine particles and the solid medium are collided in a hermetically sealed container so that the knife-like fine particles have a circle diameter coefficient of not less than 0.15 and not more than 0.4 obtained by the following formula (1) And a step of deforming at least one of the plurality of conductive fine particles so as to form a plurality of conductive fine particles.
[Equation 1]
Coefficient of circle diameter = (area × 4π) / (circumference) ² 11. The method for producing conductive fine particles according to claim 10, wherein the branch-shaped fine particles are coated with the covering layer on the branch-shaped core. 11. The method for producing conductive fine particles according to claim 10, wherein the branch-like fine particles have the branch-shaped core, and the branch-shaped fine particles are deformed, and then the coated layer is covered with the branch-shaped fine particles.

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