JP2000160052A - Composite particle and its preparation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a particle having a core/shell structure useful for powder coating for forming a conductive layer, by salting out or pH adjustment of a dispersion wherein resin particulates and flat metal core particles are dispersed thereby forming a composite particle comprising the flat metal core particles having the resin particulates adhered to the surface thereof, and washing and drying the obtained particle. SOLUTION: In the preparation of a dispersion, a resin particulate is employed in a preferable amount of 3-30 pts.wt., based on 100 pts.wt. of a flat metal core particle. The resin particulate has preferably a softening point of 70-200 deg.C and a volume average particle size of not more than 1.0 μm. A material for the resin particulate is not particularly limited. As materials for the flat metal core particle, there can be exemplified metals such as Al, Cu, Sn, Ti, Mo, Fe and the like and alloys thereof, and the average particle size is preferably 1-30 μm. The dispersion is prepared, for example, by dispersing the flat metal core particles in a dispersion of the resin particulate obtained by an emulsion polymerization reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to powder coating, printing,
Composite metal particles having a flat core / shell structure that can be applied to bonding and the like, and are mainly used for forming a conductive layer.

[0002]

2. Description of the Related Art Conventionally, for forming a conductive film, a solvent paint composed of metal particles, a resin and an organic solvent, or a sheet or film for forming a conductive film is generally used. Unlike the case of using a sheet or a film, the use of a solvent paint has the advantage that it can be easily applied to an object having a complicated shape. However, the solvent paint is not desirable for the human body or the environment because volatilization of the organic solvent at the time of painting is unavoidable by its nature. Therefore,
When using a solvent paint, it is necessary to take measures such as providing sufficient ventilation. In order to reduce the essential labor and the like of the solvent paint, coating with a powder paint containing metal particles has been proposed. This is because the use of a powder coating makes it possible to perform coating without using an organic solvent, and thus there is an advantage that the above-described labor is not essentially required.

In the case where a conductive film is formed by painting, it is necessary to adjust the properties of the conductive layer according to the purpose of use in any of the above-mentioned coating methods. For example, to form a conductive film for the purpose of preventing static electricity or shielding electromagnetic waves, the surface resistance of the conductive film is set to 104 to 5Ω.
/ □ Need to be smaller than about. For that purpose, it is necessary to add metal particles to the paint at a high ratio. Further, in order to further increase the conductivity of such a film, it is necessary that the metal particles in the film have more contacts after coating, and for this purpose, flat metal particles having a large specific surface area are used in the paint. It is believed that use is preferred. The above is required regardless of the type of paint, that is, whether it is a solvent paint, a sheet, a film, or a powder paint.

In order to achieve such an object, in the case of a conventional solvent paint using an organic solvent, it is sufficient to simply change the metal particles in the paint to one having a flat shape. In the case of the above powder coating which has been proposed to solve the problem peculiar to the solvent coating, it is difficult to achieve the above object. This is because the conventional powder coating manufacturing method itself is not suitable for using flat metal particles.

[0005] In a conventional powder coating production method, metal particles,
Raw materials such as resin are first supplied to a melt kneader by a material supply feeder, and all the raw materials are melt kneaded. Next, the produced melt-kneaded material is pulverized by a pulverizer to produce a powder for a powder coating. In such a conventional method, when flat metal particles are used as metal particles, the following problems occur. 1: The specific surface area of raw materials, especially flat metal particles, is large,
Due to the low fluidity, material bridging occurs in the material supply feeder. 2: Poor penetration of raw materials into the kneader for the same reason. Due to the reasons 3: 1 and 2, the kneader is overloaded during melt kneading, and the kneader stops.

Therefore, when flat metal particles are used as a raw material, the production itself is possible but the productivity is very low if the amount of addition is about 60 to 70% by weight of the total raw material. . In addition, in such a conventional method, the flat metal particles are added to the resin in a high ratio,
In the kneaded product obtained by melt-kneading, the surface of the flat metal particles is unevenly wet with the resin component. Alternatively, the flat metal particles in the kneaded material may be bent, broken, or torn due to the load of the kneader during kneading. Therefore, when powder is produced by a conventional method using a raw material composed of flat metal particles and a resin, resin-only particles containing no flat metal particles, flat metal-only particles, and flat metal particles and resin particles Of these, particles of three types are mixed.

Therefore, even if a film is formed using such a powder, a large number of metal particles that are not bound by a resin component exist on the surface of the obtained conductive layer. Easily detached from the layer. Further, sufficient contact between the metal particles cannot be obtained. Therefore, the function as a conductive layer cannot be sufficiently performed.

[0008]

As described above, the conventional method for producing powder by melt-kneading is not suitable for using flat metal particles. The paints used and the paintings using such paints have not been implemented. Accordingly, at present, the formation of a film such as a conductive layer is performed by a conventional solvent paint or the like.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a composite particle having a core / shell structure suitably used for a powder coating for forming a conductive layer, and a method for producing the same. I have.

[0010]

Means for Solving the Problems In order to solve the above problems and achieve the object, the present invention is configured as follows. That is, the production method of the composite particles of the present invention is a first step of preparing a dispersion in which resin fine particles and flat metal core particles are dispersed, and the dispersion obtained in the first step is subjected to salting-out or pH.
By adjusting, the second step of obtaining composite particles in which the resin fine particles adhere to the surface of the flat metal core particles,
A third step of washing and drying the composite particles.

In this production method, the resin fine particles to be dispersed in the first step are 3 parts by weight or more and 30 parts by weight or less based on 100 parts by weight of the flat metal core particles dispersed in the first step. Is preferred. Further, the softening point of the resin fine particles is preferably 70 ° C. or more and 200 ° C. or less, and the volume average particle diameter of the resin fine particles in the first step is preferably 1.0 μm or less.

[0012] The composite particles of the present invention are characterized by being produced by any of the above methods. Further, the composite particles of the present invention are characterized in that resin particles adhere to the surfaces of the flat metal core particles.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the method for producing composite particles and the composite particles of the present invention will be described in detail. The composite particle production method of the present invention is a first step of preparing a dispersion in which resin fine particles and flat metal core particles are dispersed, and by subjecting the dispersion obtained in the first step to salting out or pH adjustment,
The method is characterized by comprising a second step of obtaining composite particles in which the resin fine particles adhere to the surface of the flat metal core particles, and a third step of washing and drying the composite particles.

The fine resin particles in the first step are shells in the composite particles of the present invention, and are not particularly limited, but various resins such as styrene,
Known resins such as acryl, xylene, phenol, polyester, urethane, epoxy and the like and derivatives thereof are included. The softening point of these resins is 70 ° C.
The temperature is preferably 0 ° C. or less, and more preferably the volume average particle diameter is 1.0 μm or less so as to be uniformly dispersed in the dispersion and easily adhere to the flat metal core particles. If the above preferred conditions are satisfied, the composite particles of the present invention do not cause blocking during storage,
It is stable independently and can provide sufficient conductivity to the conductive layer when the conductive layer is formed using the composite particles.

On the other hand, when resin fine particles having a softening point of less than 70 ° C. are used for the shell of the composite particles of the present invention, it is not preferable because the composite particles are likely to cause blocking during storage. Further, when a resin having a softening point higher than 200 ° C. is used for the shell of the composite particles, the heat treatment for forming a conductive layer using the composite particles requires a treatment temperature of 200 ° C.
When the heat treatment is performed in an oxygen-containing atmosphere, the flat metal particles of the core of the composite particles are oxidized, and the conductive performance is reduced. Absent. Therefore,
The softening point of the resin is more preferably from 70 ° C to 160 ° C, most preferably from 70 ° C to 120 ° C.

The softening point in the present invention means a flow softening point, and is a flow tester (trade name: CF) manufactured by Shimadzu Corporation.
T-500), a plunger of 1.00 cm 2, a die of 0.99 mm in diameter and 1.00 mm in length was used, and the weight of 20 kgF and the heating rate of 6.0 ° C./min reduced the plunger to 1/2. The temperature when it drops. Furthermore, the volume average particle diameter of the resin fine particles is preferably 1.0 μm or less, and when the composite particles of the present invention are produced with resin fine particles satisfying this condition and used for forming a film, the metal core particles Desorption can be prevented, and the conductivity of the film can be maintained well.

On the other hand, in the case of resin fine particles having a volume average particle diameter larger than 1.0 μm, the specific surface area of the resin fine particles is reduced, so that a small amount of resin fine particles can uniformly coat the surface of the composite particle core. This is not preferable because the composite particles are easily removed from the coated surface when the composite particles are coated. That is, the smaller the volume average particle diameter of the resin fine particles is, the more preferable it is because it becomes possible to prevent the particles from being detached from the coated surface with a small amount of addition. Therefore, the volume average particle diameter of the resin fine particles is more preferably 0.8 μm or less, and most preferably 0.5 μm or less. In the present invention, the volume average particle diameter is measured by a laser diffraction particle size distribution analyzer (manufactured by Nikkiso Co., Ltd .:
Microtrack) is used.

Next, emulsion polymerization of a monomer by a radical reaction will be described as an example of a specific method of dispersing resin fine particles in the first step of the method for producing composite particles of the present invention. Specific examples of the monomer used for the emulsion polymerization include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, p-methoxystyrene,
-Phenylstyrene, 3,4-dichlorostyrene, p-
Ethylstyrene, 2,4-dimethylstyrene, pn-
Butylstyrene, p-tert-butylstyrene, p-
n-hexylstyrene, pn-octylstyrene, p
Styrene such as -n-nonylstyrene and pn-decylstyrene and derivatives thereof, ethylene, propylene,
Ethylenically unsaturated monoolefins such as butylene and isobutylene, vinyl chloride, vinylidene chloride, vinyl bromide,
And vinyl halides such as vinyl fluoride, organic acid vinyl esters such as vinyl acetate, vinyl propionate, and vinyl benzoate, methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, and n-butyl methacrylate. N-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate,
Methacrylic acid such as dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate, glycidyl methacrylic acid and derivatives thereof, acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, acrylic acid n-octyl, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-acrylic acid
Acrylic acid and its derivatives such as chloroethyl and phenyl acrylate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropenyl ketone; -Vinylpyrrole, N-vinylcarbazole, N
N such as vinylindole and N-vinylpyrrolidone
-Polymerizable monomers such as vinyl compounds, vinyl naphthalenes, acrylonitrile, methacrylonitrile, and acrylamide. These monomers can be used alone or as a mixture depending on the purpose.
Further, if necessary, acids such as maleic acid, itaconic acid and acrylic acid may be copolymerized.

If necessary, the above-mentioned monomers may include a curing agent such as dibasic acid or dibasic acid, a chromium complex salt, an azine compound, a quaternary ammonium salt, a zinc salt, a triphenylmethane compound, or the like. Charge control agent, silane type, titanate type,
Various additives such as an aluminum-based coupling agent may be added. As a polymerization initiator when performing a polymerization reaction using the above-mentioned monomer, a water-soluble polymerization initiator is preferable. Examples of such a polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate, and 2,2′-azobis (2-
An azo or diazo polymerization initiator such as methyl-N-phenylpropionamidine) dihydrochloride and 2,2′-azobis [N- (4-chlorophenyl) -2-methylphenylpropionamidine) dihydrochloride is included. These may be used alone, or two or more polymerization initiators may be used in combination. Further, in addition to the above polymerization initiator, an oil-soluble polymerization initiator such as 2,2′-azobisisobutylvaleronitrile and a peroxide-based polymerization initiator such as benzoyl peroxide may be used in combination.

The above polymerization reaction may be carried out by adding a surfactant. Examples thereof include anionic surfactants such as fatty acid soaps and alkylbenzene sulfonates, aliphatic amine salts, and aliphatic quaternary. Examples include cationic surfactants such as ammonium salts, amphoteric surfactants such as carboxymethain and aminocarboxylates, and nonionic surfactants such as polyoxyethylene alkyl ethers and polyethylene glycol fatty acid esters.

An emulsion polymerization reaction is carried out by mixing the above-mentioned monomers, a polymerization initiator, and those appropriately added with an additive and a surfactant. The conditions of this emulsion polymerization reaction can be appropriately determined by those skilled in the art according to the type of the monomer and the polymerization initiator to be used, and may be performed according to a method known in the art. By this emulsion polymerization reaction, a dispersion liquid in which resin fine particles are dispersed can be prepared. However, the method for preparing a dispersion in the first step of the present invention is not limited to the above-mentioned emulsion polymerization method. For example, a dispersion phase (oil phase) obtained by dissolving a resin in a solvent may be treated with a surfactant or a polymer. It is also possible to use a method in which the mixture is put into an aqueous solution (aqueous phase) to which a stabilizer or the like has been added and suspended by high-speed stirring.

Next, the step of dispersing the flat metal core particles in the above dispersion will be described. As the material of the flat metal core particles, aluminum, brass, titanium,
Metals such as silver, copper, platinum, palladium, nickel, tin, molybdenum, tungsten, and iron and alloys thereof and stainless steel may be used alone or in combination of two or more. As the particle diameter of the flat metal core particles, those having an average particle diameter of 1 μm or more and 100 μm or less can be used, but in order to prepare composite particles for a coating material that forms a conductive layer having uniform conductivity. It is preferable that the average particle diameter is 1 μm or more and 30 μm or less.

Here, the flat shape refers to a state in which the metal core particles are crushed between the surfaces, and a shape characterized by having a flat surface opposed by being crushed. . Furthermore, here, the plane may be sufficient as long as it is flat as compared with a sphere or an irregular shape, and may have a distortion, a warp, a bowl bending, an unevenness, or the like. Further, the above-mentioned facing surfaces do not necessarily have to be parallel. Dispersion of the flat metal core particles in the liquid can be performed, for example, by stirring the liquid containing the flat metal core particles with a stirring blade while applying ultrasonic waves. Here, the term “in liquid” may be a dispersion liquid in which resin fine particles are dispersed, or may be separate water or another solvent. Separately, when the flat metal core particles are dispersed in water or another solvent, the dispersion containing the metal core particles and the dispersion liquid in which the resin fine particles are dispersed are sufficiently mixed, What is necessary is just to provide to a 2nd process.

At this time, it is preferable that the amount of the resin fine particles is not less than 3 parts by weight and not more than 30 parts by weight based on 100 parts by weight of the flat metal core particles. When the weight ratio is within this range, when a film is formed using the obtained composite particles, the film is stable and maintains good conductivity. If the addition ratio of the resin fine particles is less than 3 parts by weight, it becomes difficult to uniformly coat the surfaces of the flat metal core particles with the resin fine particles. Therefore, in this case, the composite particles are likely to be detached from the coated object, which leads to a decrease in conductivity, which is not preferable. On the other hand, when the addition amount of the resin fine particles is more than 30 parts by weight, the frequency of contact between the flat metal core particles in the coating film decreases, and this case is also not preferable because the conductive performance also decreases.

As described above, in the first step, a dispersion in which the flat metal core particles and the resin fine particles are sufficiently dispersed at a fixed ratio can be obtained. Next, a description will be given of the second step of obtaining the composite particles in which the resin fine particles in the dispersion are adhered to the surface of the metal core particles as a shell by salting out or adjusting the pH of the dispersion obtained in the first step. I do.

When the composite particles are obtained by salting out, salts such as sodium chloride, magnesium chloride, potassium chloride, and calcium chloride are added to the dispersion obtained in the first step, and the resin particles are placed on the flat metal core particles. Let the fine particles adhere. It is necessary to appropriately adjust the amount of the salt to be added according to the type of the salt, the type of the resin fine particles, and the like, and this may be appropriately adjusted by those skilled in the art. On the other hand, in order to obtain the composite particles by adjusting the pH of the dispersion, the pH of the dispersion is controlled using an acid such as sulfuric acid or an alkali such as sodium hydroxide, so that the resin fine particles adhere to the flat metal core particles. Let me know. That is, it is preferable to control the pH to 1 to 4 when using an acid and to control the pH to 9 to 11 when using an alkali. Whether an acid or an alkali is used may be appropriately determined by those skilled in the art according to the type of the selected resin and the like.

Next, the third step of washing and drying the composite particles obtained in the second step will be described. The composite particles obtained in the second step are separated from the dispersion by filtration or the like, and washed with deionized water or a solvent such as alcohol. After the washing, the separated composite particles are sufficiently dried using, for example, a vacuum vibration dryer. The degree of washing and drying is appropriately adjusted depending on the required quality.

The composite particles having the core / shell structure of the present invention can be obtained by the production method comprising the above first to third steps. The composite particles having a core / shell structure of the present invention may have a primary particle of 0.5 μm or less on the surface of the composite particles for the purpose of improving fluidity, if necessary.
A fluidity imparting agent such as inorganic ultrafine particles such as silica, alumina and titanium oxide, or crosslinked resin ultrafine particles such as methyl methacrylate may be adhered. Here, in order to adhere the fluidity-imparting agent to the surface of the composite particles, the two may be dry-mixed with a high-speed mixer such as a Henschel mixer or a super mixer.

Since the composite particles of the present invention are produced by adhering fine resin particles to the surfaces of the flat metal core particles by the wet method as described above, the fine resin particles adhere to almost the entire surface of the flat metal core particles. And the resin fine particles are attached in a lump. Moreover, the state of adhesion of the resin fine particles on the surface of the flat metal core particles is not limited to a single layer, but may be a multilayer structure. The composite particles of the present invention can be applied to powder coating, printing, bonding, etc. for the purpose of forming a conductive layer, but they form a conductive layer having functions such as antistatic and electromagnetic wave shielding. It can be suitably used as a powder coating.

[0030]

EXAMPLES Specific examples of the present invention will be described below.

(Example 1) <Preparation of dispersion liquid of resin fine particles>
A dispersed phase was prepared by mixing 150 g of n-butyl acrylate. Next, 3000 g of deionized water, 30 g of potassium persulfate, and 6 g of sodium dodecyl sulfate were stirred and mixed to prepare a continuous phase. The above-mentioned dispersed phase and continuous phase were mixed and stirred with a high-speed stirrer at 5,000 rpm for 3 minutes to emulsify. Then, the emulsion was heated at 80 ° C. for 5 hours to perform a polymerization reaction. Then, the mixture was cooled to room temperature and provided to the following composite particle production step without purification. still,
The softening point of the resin fine particles was 140 ° C. when measured with a flow tester manufactured by Shimadzu Corporation. The volume average particle size measured by a laser diffraction type particle size distribution analyzer was 0.1 μm. <Preparation of Dispersion of Flat Metal Core Particles> Methanol 150
Silver particles having a flat shape with an average particle size of 7.0 μm in 0 g (manufactured by Tokurika Chemical Co., Ltd .: trade name Silvest TCG-7) 5
100 g, and with ultrasonic waves applied, 30
The mixture was stirred at 0 rpm for 30 minutes to disperse the silver particles. <Production of composite particles> Silver particles 100 in the above-mentioned dispersed state
The above resin fine particles were blended so as to be 20 parts by weight with respect to the parts by weight, and both the dispersions were mixed with a stirring blade for 15 parts.
The mixture was stirred and mixed at 0 rpm. Further, 100 g of sodium chloride was added to the dispersion, and the mixture was stirred at 150 rpm using a stirring blade.
For 5 minutes to carry out salting out. Next, after filtering the composite particles generated by salting out, the particles were washed 10 times with deionized water, and then dried at 30 ° C. for 12 hours using a vacuum vibration dryer to obtain composite particles having a core / shell structure. .
The composite particles after drying had soft caked to the extent that they collapsed when touched by hand, and were used after being crushed with a Henschel mixer.

(Example 2) Nickel particles (manufactured by INCO, trade name: Nickel Flake CHT) were used as flat metal core particles.
(Average particle size: 13.5 μm) Except for changing to 13.5 μm, composite particles were obtained in the same manner as in Example 1.

Example 3 A dispersion of fine resin particles and a dispersion of flat metal core particles were obtained in the same manner as in Example 1. Next, 100 parts by weight of silver particles dispersed in methanol were blended with the above resin fine particles so as to be 10 parts by weight, and this was stirred and mixed at 150 rpm using a stirring blade. Further, 50 g of nitric acid (reagent first grade) was added, and the mixture was stirred to adjust the pH to 2, and then heated at 55 ° C. for 4 hours. Next, after cooling to room temperature, the composite particles are filtered, washed with deionized water until the pH becomes 7, and then dried at 40 ° C. for 12 hours by a vacuum vibration dryer. Composite particles having a core / shell structure were obtained.

(Comparative Example 1) <Preparation of Powder Particles by Kneading and Pulverizing Method> The same silver particles as in Example 1 and a styrene / acrylic resin (C: Mitsui Chemicals, Inc .: C)
PR-100, softening point 110 ° C.) were weighed in a weight ratio of 100: 20 and sufficiently premixed using a Henschel mixer. The mixture was melt-kneaded in a kneader, and the kneaded material was pulverized with a pulverizer so that the volume average particle diameter became 9 μm,
A powder sample was obtained. Since the premix obtained by the premix had low fluidity, a bridge was chronically generated, and the productivity was extremely poor. In addition, the mixed material did not bite well into the kneader, and the resulting mixture was in an uneven state in which the surface of the silver particles was not sufficiently wet with the resin because the resin content was small. Observation of the preparation of this comparative example with a digital microscope (manufactured by KEYENCE CORPORATION) at a magnification of 2000 revealed that the preparation was composed of resin-only particles containing no flat metal particles, flat metal-only particles, and flat metal particles and resin fine particles. Three kinds of particles were mixed.

(Comparative Example 2) <Preparation of powder particles by dry blending> Styrene / acrylic resin (manufactured by Mitsui Chemicals: CPR-100, softening point 1)
10 ° C.) with a pulverizer to give a volume average particle size of 5.0.
μm resin fine particles were prepared. A powder sample was obtained by adding 20 parts by weight of the above-mentioned pulverized styrene / acrylic resin fine particles to 100 parts by weight of the same nickel particles as in Example 2, and sufficiently mixing using a mixer.

(Test Example: Formation of Conductive Layer) A glass plate (1.3 mm × 76 mm × 52 mm) with an iron plate adhered to the back surface
Are prepared by the number of the above Examples and Comparative Examples, and the powder particles of the above Examples and Comparative Examples are respectively supplied to the electrostatic spray gun of the corona charging system (trade name: G, manufactured by Chichibu Onoda Co., Ltd.).
X-108). The conditions at the time of painting were as follows. Applied voltage -60KV, pattern adjustment 1.0kgf
/ Cm 2, 1.5 kgf / cm 2 of empty space, discharge amount 2.
0 kgf / cm2, flowing air 2.0 kgf / cm2,
The distance between the glass plate and the tip of the gun is maintained at 20 cm, and the coating time is 3 seconds. Next, each glass plate was heated at 180 ° C for 10
Heat treatment was performed for a minute to form a conductive layer on the glass plate. After the coating was completely dried, the coating properties were evaluated for the conductive layers on each glass plate. <Surface Resistance Measurement> The surface resistance of the conductive layer formed on each glass plate was measured with a surface resistance measuring device (trade name: MCP-T350) manufactured by Yuka Electronics Corporation. <Tape peeling test> A clear tape (trade name: Scotch, manufactured by 3M) was applied to the surface of the conductive layer formed on the glass plate.
A clear tape (24 mm × 35 mm) was adhered and rubbed three times with an eraser to sufficiently adhere to each other, and then the clear tape was immediately peeled off from the coating film. The peeled clear tape was observed with an optical microscope having a magnification of 200 times to observe whether or not the flat metal core particles were detached from the conductive layer. still,
The observation area at this time was 1.0 cm 2.

Table 1 shows the results of the surface resistance and the tape peeling test.

[0038]

[Table 1]

The evaluation criteria for the tape peeling evaluation test are as follows. ：: No desorption, ×: Desorption occurred. Unmeasurable in the table indicates that the surface resistance is 106Ω / □ or more.

The surface resistance of the conductive layer using the powder particles of Examples 1 to 3 was 103 Ω / □ or less, and no detachment of the flat metal core particles from the conductive layer was observed. On the other hand, although the powder particles of Comparative Example 1 have a composition similar to that of Example 1, the powder particles have much lower conductivity than the conductive layer of Example 1, and the removal of the flat metal core particles from the conductive layer. Separation was also observed. In the powder particles of Comparative Example 2, both the conductive performance and the detachment of the flat metal core particles were poor.

Therefore, a film formed using the composite particles of Example 1 corresponding to the present invention gave the best properties as a conductive layer.

[0042]

According to the production method of the present invention, composite particles having a core / shell structure in which fine resin particles are uniformly adhered to the surfaces of the flat metal core particles can be obtained. Therefore, when a conductive layer is formed using the composite particles, the flat metal core particles in the conductive layer can be in sufficient contact with each other while maintaining the original shape, so that the conductive layer can have sufficient conductivity. Further, by using the composite particles of the present invention, it is possible to obtain a conductive layer in which the detachment of the flat metal core particles is extremely small.

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Claims (6)

[Claims] 1. A first step of preparing a dispersion in which resin fine particles and flat metal core particles are dispersed, and salting out or adjusting the pH of the dispersion obtained in the first step to obtain the resin fine particles. Comprises a second step of obtaining composite particles adhered to the surface of the flat metal core particles, and a third step of washing and drying the composite particles. 2. The resin fine particles to be dispersed in the first step are 3 parts by weight or more and 30 parts by weight or less based on 100 parts by weight of the flat metal core particles dispersed in the first step. Item 10. The production method according to Item 1. 3. The method according to claim 1, wherein the softening point of the resin fine particles is 70 ° C. or more and 200 ° C. or less. 4. The production method according to claim 1, wherein the volume average particle diameter of the resin fine particles in the first step is 1.0 μm or less. 5. Composite particles produced by the method according to any one of claims 1 to 4. 6. Composite particles wherein resin fine particles adhere to the surface of the flat metal core particles.