JP2000017194A - Conductive powder and coating, coating film, resin composition and adhesive using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the conductive powder maintaining the original light weight of aluminum, capable of stably exhibiting excellent conductivity for a long period, further capable of expressing excellent heat dissipation and metal brightness, and useful for conductive resin moldings, etc., by using specific flat aluminum (alloy) powder. SOLUTION: This conductive powder (for example, the conductive powder having an average particle diameter of 0.1-500 μm and a flatness rate expressed by a longest diameter/shortest diameter ratio of 2/1 to 500/1 by a laser diffraction method) comprises flat aluminum (alloy) powder coated with a different kind of metal such as gold, silver, copper, nickel, platinum, palladium or tin by a PVD method, a mechanical method, etc., (for example, the metal is adhered to >=5% of the surface area of the flat powder). The conductive powder is obtained by coating 100 pts.wt. of aluminum (alloy) powder with 1-100 pts.wt. of the different metal and subsequently plastically processing the coated aluminum (alloy) powder into a flat shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an EMI shield,
The present invention relates to a conductive powder to be blended in a paint for antistatic use, an ink for electronic board wiring, and a resin, rubber, compound, adhesive or the like.

[0002]

2. Description of the Related Art Pigments used in conductive and antistatic paints include carbon, metals, metal oxides and the like. For metal oxides, or doped with a dissimilar metal to SnO _2, TiO _2, oxides such as ZnO _2, but a fine powder having conductivity in that surface treatment is utilized, the cost is high, conducting Due to its limited nature, it is used only in special fields that require transparency. In addition, paints using carbon black have been widely used because they are inexpensive and have better conductivity than metal oxides. However, there are problems that it is difficult to give a color other than black and that carbon is detached from the coating film or oxidized after a long-term use. It is conceivable to use metal,
Gold, silver and the like have good conductivity, but are unsuitable for large-scale use as industrial materials due to high cost. Copper is excellent in both cost and conductivity, but has problems of oxidation and discoloration, and has low commercial value. Nickel is an industrial material that has been put to practical use, but has poorer conductivity than noble metals. Each of these metals has a specific gravity of 8 or more and is extremely inconvenient to use, for example, settling in paints and coatings.

[0003] In the case of a resin molded product or compound having conductivity and antistatic properties, carbon black or metal fibers such as stainless steel and copper have been used in many cases. When carbon black is used, there is a problem of coloring and desorption like the paint. In addition, when metal fibers are used, the specific gravity of the molded body increases because a metal having a large specific gravity such as stainless steel or copper is highly blended. This is a major drawback when used in all applications such as building materials and OA equipment.

[0004]

Conventionally, studies have been made on the use of aluminum fibers (hereinafter, aluminum and aluminum alloys are simply referred to as aluminum) and aluminum powder for these purposes in order to reduce the specific gravity of the molded product and the coating film. Has been done. However, sufficient conductivity cannot be obtained due to the strong natural oxide film, and aluminum powder or aluminum fiber as a conductive material has not been put into practical use. Even if the aluminum powder is highly blended with the paint or the resin compound, the coating film or the molded product does not show sufficient conductivity. The conductivity can be improved by coating the surface with a metal with low volume resistivity, such as silver, but the aluminum oxide film remains intact, so the conductivity is not sufficient and a large conductivity is required. In this case, it is necessary to coat a large amount of silver or the like, which increases the weight of the composite powder, which not only makes it difficult to utilize the lightness of aluminum but also increases the cost.

On the other hand, when a metal is coated on a resin powder, mica, or glass powder as a metal-coated composite powder to exhibit conductivity, the particle size is small enough to be practically used in a conventional electroless plating method. In order to ensure uniformity and sufficient conductivity, the metal coating on the powder having the following must be thick. In addition, the larger the specific surface area and the smaller the true specific gravity of the powder, the greater the coating weight of the metal with the higher specific gravity. The greater the weight of the composite powder, the more its significance (light weight) is lost. In addition, the production cost such as the cost of the plating solution and its management is increased.

The present invention has been made to solve such a problem. The surface of an aluminum powder is coated with a metal having excellent conductivity by a PVD method or the like, and the aluminum powder is plastically (stretched). A powder having good conductivity is provided by forming into a flat shape together with the coated metal film by processing.

[0007]

Means for Solving the Problems The conductive powder of the present invention comprises:
Preferably, aluminum powder having an average particle size of 150 μm or less is PVD
100 parts by weight of aluminum is coated with 1 to 100 parts by weight of dissimilar metal by a method or a mechanical treatment, and the coated granular aluminum powder is further flattened (longest diameter / shortest diameter) 2/1 to 1
This powder is characterized by being plastically (stretched) processed into a 500/1 flat (flake) shape.

As the raw material aluminum powder used in the present invention, a known aluminum powder such as a commercially available aluminum powder can be used. For example,
Atomized powder, crushed powder, powder obtained by a rotating disk method, a rotating electrode method, a cavitation method, a melt spinning method, or the like can be used. Among these, atomized powder is preferred in terms of cost and properties. The shape is not necessarily limited, but is preferably spherical or nearly spherical. These are inert gases (A
r, He) can be easily obtained by a spraying method or a nitrogen gas spraying method. The particle size of the raw aluminum powder is preferably classified to an average particle size of 150 μm or less, and particularly preferably from 0.1 to 50 μm. When the average particle size exceeds 150 μm, it takes a long time for the subsequent plastic working (flattening process), and when the powder after the flattening process is blended with a resin or a paint, uneven dispersion or reduction in hiding power, etc. Problem may occur. On the other hand, when the thickness is less than 0.1 μm, the production cost is high, and there is a problem of agglomeration of particles, which is not suitable for practical use. The purity is not particularly limited, and may include unavoidable impurities and the like, and may be an alloy containing at least one of Si, Mg, and transition metal. However, the use of a high-concentration solid solution type alloy is not preferable because the electric conductivity is low.

The different metal used in the present invention, that is, the metal coated on the aluminum powder, is theoretically an alkali metal (1A).
All metals except group I) are possible, but preferably must be both ductile and conductive, so are preferably gold, silver, copper, nickel, platinum, palladium, beryllium, rhodium, tin, zinc and At least one selected from these alloys can be used. Particularly preferred are silver and nickel. As the coating method, a mechanical method such as a PVD method and a thermal spraying method, a mechanical alloying method, a complexing treatment with a mechanofusion (manufactured by Hosokawa Micron Corporation) and a hybridizer (manufactured by Nara Machinery Works) can be adopted. Although chemical means such as a CVD method, an electrolytic plating method, or an electroless plating method are possible, at present, there are problems of cost and equipment.

The PVD method includes a known sputtering method,
There are a vacuum deposition method, an ion plating method and the like, which can be adopted. As the sputtering method, a bipolar sputtering method, a magnetron sputtering method, a high-frequency sputtering method, or the like can be adopted. Usually, the atmosphere in the sputtering chamber is performed by introducing an argon gas as a plasma source under reduced pressure. As a mechanical method, a known method such as a mechanical alloying method can be used, and a dissimilar metal can be mechanically bonded to the surface of the aluminum powder. The coating thickness of the coating metal is required to be 10 Å or more. If the thickness is 10 Å, there is a high possibility that the effect of the present invention is not exhibited or the film is broken during the subsequent plastic working. The amount of the coating metal is preferably 1 to 100 parts by weight based on 100 parts by weight of aluminum, and more preferably 2 to 50 parts by weight based on 100 parts by weight of aluminum. If the amount is less than 1 part by weight, sufficient performance cannot be obtained, and the conductivity of the final product is not sufficient. Even if the amount exceeds 100 parts by weight, further improvement in the electrical conductivity cannot be expected, but merely an increase in weight and cost.

In the present invention, the kinds of dissimilar metals to be coated on the aluminum powder may be two or more, and may have two or more layers of dissimilar metal films.

[0012] Plastic working (flattening treatment) performed in the present invention
Is a known ball mill, stamp mill, attritor,
A vibration mill and other known pulverizers and the like can be used.
The flattening may be performed by either a wet process or a dry process, but is preferably performed by a wet process for safety. In addition, when a mechanical (solid-phase bonding) treatment such as a mechanical alloying method is employed, the above-described dissimilar metal coating treatment and flattening treatment can be performed together depending on conditions.

The plastic working is

[0014]

Embedded image

The following processing may be performed. (Example: When the shortest diameter of the powder before processing is 24 μm, the shortest diameter of the powder after processing may be 12 μm or less.) As for the shortest diameter and longest diameter, about 100 powder particles are observed by SEM observation or the like. Then, it may be obtained by actual measurement or by using a commercially available image analyzer. The plastic working also requires that the flatness of the powder particles after processing, that is, the longest diameter / shortest diameter is 2/1 or more. If it is less than this, the plastic working is not sufficient and the oxide film of the aluminum particles as the core is not sufficiently broken. The upper limit is not particularly specified because it varies depending on the type and application of the dissimilar metal to be coated.
It is about 00/1. If the flatness exceeds 500,
There is a risk of breakage during the process and when blended in paints and resins, and there is also a risk of protrusion from the surface of the coating film / molded product. By the flattening treatment, both the core aluminum and the coated metal are simultaneously stretched, and at this time, the oxide film of the aluminum is destroyed and the conduction with the coated metal is improved. This effect is finally at least 5%, preferably 30%, of the surface area of the aluminum particles.
If the dissimilar metal is attached as described above, a tentative effect can be exhibited. The deposition of a dissimilar metal by sputtering or the like does not always adhere uniformly to the surface of the aluminum particles, and sometimes adheres in stripes or spots. Nature is secured. The average particle size of the conductive powder of the present invention is usually 0.1 to 5 although it depends on the use and required characteristics.
It is preferably within a range of 00 μm, more preferably 5 to 2 μm.
It is within the range of 00 μm. If the average particle size is less than 0.1 μm, the problem of aggregation occurs, handling becomes difficult, and the color tone becomes dark, which is not preferable. 500
If it exceeds μm, there is a risk of breakage during handling and a risk of protrusion from the surface of the coating film or molded product.

The conductive powder of the present invention can be blended with known paints, inks, rubbers, compounds and the like. In the case of a coating composition or an ink, it can be obtained by blending a suitable amount of a solvent, a varnish, and the conductive powder of the present invention. Color pigments can be added to this as needed. As the solvent, known solvents can be used as they are or as a mixture, for example, mineral spirits, hexane, heptane, cyclohexane, aliphatic hydrocarbons such as octane, benzene, toluene, aromatic hydrocarbons such as xylene, Halogenated hydrocarbons such as chlorobenzene, trichlorobenzene, perchlorethylene, and trichloroethylene; alcohols such as methanol, ethanol, n-propyl alcohol, and n-butanol; ketones such as n-propanone and 2-butanone; and ethyl acetate. And esters such as propyl acetate and ethers such as tetrahydrofuran, diethyl ether and ethyl propyl ether. Examples of the varnish include an acrylic resin, a polyester resin, an alkyd resin, an epoxy resin, and a fluororesin. The varnish can also be used in combination with a crosslinking agent such as an amino resin or a blocked polyisocyanate resin. In addition to these, lacquers that cure by natural drying, two-pack polyurethane resins, silicone resins, and the like can also be used. Examples of coloring pigments include organic pigments such as quinacridone red, phthalocyanine blue, phthalocyanine green, isoindolinone yellow, carbon black, perylene, azo lake, iron oxide, titanium oxide, cobalt blue, zinc white, ultramarine, chromium oxide, mica, Inorganic pigments such as graphite; The color pigment and the varnish are not limited to one type, and two or more types may be mixed or added simultaneously. Other than these, ultraviolet absorbers, thickeners, static eliminators, dispersants, antioxidants, polishes, surfactants, synthetic preservatives, lubricants, plasticizers, curing agents, fillers (strengthening agents), etc. May be added as necessary. Known methods can be used as a method of forming the coating into a coating film, such as brushing, spraying, coating with a doctor blade, a roll coater, or a bar coater, or a printing method.

As the resin used in the resin composition, one or more of acrylic resin, alkyd resin, polyester, polyurethane, polyethylene, polypropylene, polybutadiene, polycarbonate, ABS resin, polyvinyl acetate, polyvinyl chloride, etc. are used. it can. If necessary, the above solvents, coloring pigments, ultraviolet absorbers, thickeners, static eliminators, dispersants, antioxidants, polishes, surfactants, synthetic preservatives, lubricants, plasticizers, curing agents , Fillers (reinforcing agents) and the like are added as necessary. As a molding method, a known method can be adopted, and examples thereof include an extrusion molding method, an injection molding method, an inflation method, and other melt molding methods.

The rubber used in the rubber composition includes:
Butadiene rubber, styrene butadiene rubber, ethylene propylene copolymer, nitrile butadiene rubber, urethane rubber, silicone rubber, fluorine rubber, acrylic rubber,
Natural rubber, thermoplastic elastomer and the like can be mentioned.

The adhesive may be a nitrile rubber-based, polyurethane-based, epoxy resin-based, vinyl acetate-based, cyanoacrylate-based, natural rubber-based adhesive, or an emulsion-based adhesive such as an ethylene-vinyl acetate copolymer or an acrylic resin. It can be applied to various water-based adhesives.

In addition, acrylics, rubbers and the like used for sealing agents and putties for construction and vehicles, and adhesive tapes (double-sided tapes or single-sided tapes may be used depending on the application). The same effect as in the case of the paint is exerted on the pressure-sensitive adhesive.

The amount of the conductive powder of the present invention to be added to paints, resin compositions, rubbers and compounds is appropriately selected depending on the application and the constituent materials.
It can be used in a state of being blended by about 70% by volume. When importance is placed on conductivity, the content is preferably 20% by volume or more.

[0022]

According to the present invention, the aluminum powder after the flattening process is not coated with the dissimilar metal, but is coated on the atomized aluminum powder or the like with the dissimilar metal, and then the flattening process is performed. This improves the adhesiveness with aluminum and breaks down and disperses the oxide film of the atomized aluminum powder and the like, thereby exhibiting the high conductivity of aluminum itself. Once broken, the oxide film is not easily regenerated because it is covered with a dissimilar metal. Therefore, stable conductivity is exhibited for a long time. In addition, due to the inherent lightness of aluminum, the weight is reduced to less than half that of conventional silver or nickel alone, and it is difficult to sediment or has a slow sedimentation speed when mixed with paints and inks. And when it is blended with resin or the like, it contributes to weight reduction of the molded article.

The conductive powder of the present invention can be compounded as a pigment or filler in compounds such as inks, paints, resins, and adhesives, rubbers, and polymer materials, and can impart conductivity and heat dissipation, and can be used as a metal. Excellent design can be brought out by its brilliancy. In particular, when gold is used for the metal to be coated, a stable golden color can be exhibited, and when silver is used, a metallic sensation of a white brilliant color tone can be exhibited. , A variety of unprecedented color tones can be exhibited. When blended in paints and inks, it can be used regardless of oil-based water, and can be applied to fields where aluminum alone could not be used.

Products to which the conductive powder of the present invention can be applied include resin molded products having EMI shielding / antistatic properties (OA equipment, mobile phones, electronic notebooks, AV equipment, other communication / measurement equipment, electronic equipment, etc.). ), Rubbers, compounds (adhesives) and paints / coatings, and wiring inks for electronic substrates. When gold, silver, palladium, or the like is used as the metal to be coated, these metals are safe for the human body as well as have a track record as medical materials.

Examples will be described below, but they merely show one embodiment of the present invention. The scope of the present invention is defined by the appended claims, and the meaning equivalent to the claims and all the equivalents within the scope are set forth. Changes are intended to be included.

[0026]

Example 1 (Coating step) Using a powder sputtering apparatus disclosed in JP-A-2-153068,
On the surface of pure aluminum (hereinafter, Al) powder (AB-1003, manufactured by Toyo Aluminum Co., Ltd., purity: 99.7% by weight, average particle diameter: 40 μm), 10 parts by weight of silver (provided that 100 parts by weight of Al ) Was coated. Inner diameter 2
Al in a rotating drum with a length of 200 mm and an axial length of 200 mm
After filling with 100 g of powder and reducing the pressure to 3.0 × 10 ⁻³ Pa, while introducing Ar gas at a flow rate of 15 cm ³ / min,
The atmosphere inside the drum was kept constant. Thereafter, magnetron type sputtering was performed using a silver target as a sputtering source under the conditions of an input power of 1.5 kW and a frequency of 13.56 MHz to coat the surface of the Al powder with silver. After the sputtering was continued for 90 minutes, the Al powder in the drum was collected. 10.2 parts by weight (excluding Al)
Of 100 parts by weight).

(Flattening process) The following materials were charged together with 50 kg of 3/8 inch steel balls into a ball mill having a diameter of 500 mm and a volume of 30 liters, and the rotation speed was 6
The flattening treatment was performed under the conditions of 0 rpm and a grinding time of 3.5 hours.

Before processing Average particle diameter 40 μm Longest diameter 65 μm Minimum diameter 24 μm (teardrop-shaped powder) After processing Average particle diameter 25 μm Longest diameter 54 μm Minimum diameter 1.8 μm (flat powder) Silver sputter-coated atomized aluminum powder prepared above 1.5 kg Oleic acid 100 g Mineral spirit 2 liters Silver-coated flat Al powder was washed out from a ball mill using 16 liters of mineral spirits, and washed with a wet classifier.
After passing through a 50-mesh screen, solid-liquid separation was performed to obtain a cake containing silver-coated flat Al powder as a main component.
After putting the cake into the mixer, mineral spirit was added with stirring, and the silver-coated flat Al with a metal content of 65% by weight was added.
A pigment composition containing the powder was produced.

A part of the above pigment composition was used as a sample, and a laser diffraction particle size distribution analyzer (SA manufactured by Shimadzu Corporation) was used.
The average particle diameter of the silver-coated flat Al powder was measured by LD-1100) and found to be 25 μm.

(Electrical Conductivity Evaluation Method) <Preparation of Coated Plate> The pigment of the above example was formed into a paint by the following formulation.

The following example is a blending example of 30% by volume of silver-coated flat Al powder.

Acridic A-165 (Acrylic paint resin) (Dai Nippon Ink Chemical Industry Co., Ltd., solid content 55% by weight) 100 parts by weight Pigment composition of Example (heating residue 65% by weight) 105. 2 parts by weight (equivalent to 30% by volume) Thinner (main component: toluene) 150 parts by weight This paint is applied to an ABS resin substrate by air spray,
It was dried at 80 ° C. for 20 minutes to prepare a coated plate having a thickness of about 15 μm.

The conductivity of this coating film was determined by Mitsubishi Chemical
estaMP ". Further, as a result of observing the surface and cross section of this coating film, the flattening ratio (longest diameter / shortest diameter) of the silver-coated flat Al powder particles was 30/1. (However,
Table 1 shows the average value of 100 particles. Volume content and surface resistance value of silver-coated flat Al powder of the coating film produced using the powder of Example 1 Volume content ratio (%) Surface resistance value (Ω / □) 25 4.2 × 10 ³ 30 5.6 × 10 ⁰ 45 6.0 × 10 ⁻¹

[0034]

Example 2 In the same process as in Example 1, 5 parts by weight of silver was coated on Al powder (Al is 100 parts by weight), and after flattening treatment, the non-volatile content was reduced to 65% by weight. To obtain a pigment composition. By the same evaluation method as in Example 1, the surface resistance at a volume content of 30% by volume and a film thickness of about 15 μ was measured.

(See Table 2)

[0036]

Embodiment 3 Copper is coated on Al powder by 10 parts by weight (Al is assumed to be 100 parts by weight) in the same process as in Example 1, and a flattening process is performed. To obtain a pigment composition. By the same evaluation method as in Example 1, the surface resistance at a volume content of 30% by volume and a film thickness of about 15 μ was measured.

[0037]

Example 4 Al powder was coated on Al powder by 10 parts by weight (however, Al was 100 parts by weight) in the same process as in Example 1 and flattened. To obtain a pigment composition. By the same evaluation method as in Example 1, the surface resistance at a volume content of 30% by volume and a film thickness of about 15 μ was measured.

[0038]

Embodiment 5 In the same process as in Embodiment 1, 10 parts by weight of an Ag-12% Pd alloy (10% by weight of Al
After coating and flattening, the nonvolatile content was adjusted to 65% by weight to obtain a pigment composition. By the same evaluation method as in Example 1, the surface resistance at a volume content of 30% by volume and a film thickness of about 15 μ was measured.

[0039]

Comparative Example 1 The same flattening treatment as in Example 1 was performed without coating the Al powder with silver, and then the nonvolatile content was adjusted to 65% to obtain a pigment composition. By the same evaluation method as in Example 1, the surface resistance at a volume content of 30% by volume and a film thickness of about 15 μ was measured.

Table 2 Evaluation Results of Each Surface Resistance Value Coated Metal Type Coated Metal Amount (parts by weight) Surface Resistance Value (Ω / □) Example 2 Silver 5 2.3 × 10 ² Example 3 Copper 10 6.4 × 10 ¹ Example 4 Gold 10 1.4 × 10 ¹ Example 5 Ag-Pd 10 1.9 × 10 ¹ Comparative Example 1 None> 10 ⁷

[0041]

Example 6 In the same process as in Example 1, silver was coated on Al powder in the amount shown in Table 3 and subjected to a flattening treatment. Then, the nonvolatile content was adjusted to 65% by weight to obtain a pigment composition. Was. By the same evaluation method as in Example 1, the surface resistance at a volume content of 30% by volume and a film thickness of about 15 μ was measured.

[0042]

[0043]

Embodiment 7 In the same process as in Embodiment 1, 20 parts by weight of silver (although 100 parts by weight of Al) was coated on Al powder, and after flattening treatment, non-volatile content was 90% by weight. To obtain a pigment composition. The pigment composition was blended with the ABS resin so as to have a volume content shown in Table 4, kneaded at about 220 ° C., and then, at the same temperature, an injection molding machine was used.
It was injection-molded into a shape of 50 mm wide x 3 mm thick.

The surface resistance of the injection molded article was measured in the same manner as in Example 1.

[0045]

[0046]

Comparative Example 2.3 A flattening treatment similar to that of Example 1 was performed without coating the Al powder and the Ni powder with silver, respectively.
The pigment composition was obtained by adjusting the nonvolatile content to 90%. In the same manner as in Example 7, ABS was adjusted so that the volume content became 30%.
Each was mixed with a resin, injection-molded, and the surface resistance of the molded product was measured.

Table 5 Measurement results of surface resistance Metal type Coated metal Surface resistance value (Ω / □) No Al> 10 ⁷ Ni None 6.6 × 10 ³

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // H05K 9/00 H05K 9/00 W (72) Inventor Takashi Yamamoto Hisaromachi, Chuo-ku, Chuo-ku, Osaka-shi, Osaka No. 6-8, Toyo Aluminum Co., Ltd. (72) Inventor Sharp Takeshima, Chichi Pref., Chichi Pref. DE146 FA026 FB076 FD116 FD117 GH01 GQ01 4J037 AA05 AA06 CA03 DD10 DD12 EE03 EE23 EE28 FF11 4J038 CD091 CG001 DA112 DB001 DD001 DD231 DG001 DG302 DL001 HA066 JA02 JA05 JA09 JA14 JA19 JA26 JA12 JA20 JA20 KA03 JA56 JA20 KA03 CA071 DE021 DE031 DF041 DF061 EC001 EF001 HA066 JB10 KA03 KA07 KA32 LA09 NA20 5E321 BB32 BB34 BB60 GG05

Claims (15)

[Claims] 1. A conductive powder comprising a flat aluminum powder or a flat aluminum alloy powder coated with a dissimilar metal. 2. The conductive powder according to claim 1, which is obtained by subjecting an aluminum powder or an aluminum alloy powder coated with a dissimilar metal to plastic working. 3. The conductive powder according to claim 1, wherein the dissimilar metal is coated in an amount of 1 to 100 parts by weight based on 100 parts by weight of aluminum or aluminum alloy. 4. The conductive powder according to claim 1, wherein the dissimilar metal is at least one selected from gold, silver, copper, nickel, platinum, palladium, beryllium, rhodium, tin, zinc and alloys thereof. . 5. The conductive powder according to claim 1, wherein the dissimilar metal is attached to a portion of 5% or more of the surface area of the flat aluminum powder or the flat aluminum alloy powder. 6. An aspect ratio (longest diameter / shortest diameter) of 2/1 to 5
The conductive powder according to claim 1, wherein the ratio is 00/1. 7. The conductive powder according to claim 1, which has an average particle size (by laser diffraction method) of 0.1 to 500 μm. 8. The conductive powder according to claim 1, wherein the coating is performed by a PVD method. 9. The conductive powder according to claim 1, wherein the coating is performed by a mechanical method. 10. A paint containing the conductive powder according to claim 1 as a pigment. 11. A coating film containing the conductive powder according to claim 1. 12. A resin composition containing the conductive powder according to claim 1. 13. A resin molded article containing the conductive powder according to claim 1. 14. An adhesive containing the conductive powder according to claim 1. 15. A method for producing a conductive powder, comprising subjecting an aluminum powder or an aluminum alloy powder coated with a dissimilar metal to plastic working.