JP2008144045A - Fibrous electrically conductive filler and electrically conductive resin composition and electrically conductive structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fibrous electrically conductive filler capable of forming a soft electrically conductive structure, to provide an electrically conductive resin composition containing the fibrous electrically conductive filler, to provide such an electrically conductive structure comprising the electrically conductive resin composition, and to provide an antenna and an electromagnetic shielding material each using the electrically conductive structure. <P>SOLUTION: The fibrous electrically conductive filler, with its length L falling within the range of 0.5-100 μm, comprises organic fibers and an electrically conductive substance coated on the surfaces thereof. The electrically conductive resin composition containing the fibrous electrically conductive filler, the electrically conductive structure comprising the electrically conductive resin composition, and the antenna and the electromagnetic shielding material each using the electrically conductive structure, are provided, respectively. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fibrous conductive filler used by blending in a conductive resin composition, a conductive resin composition blended with the fibrous conductive filler, and a conductive structure including the conductive resin composition About.

  Conventionally, as the conductive filler used by blending in the conductive resin composition, inorganic fibrous conductive fillers such as carbon fibers and metal whiskers, and conductive fillers composed of powders such as carbon fine particles have been proposed. (For example, refer to Patent Documents 1 to 4). However, when a conductive structure is obtained by applying a conductive resin composition containing an inorganic fibrous conductive filler to a base material, the rigidity of the inorganic fibrous conductive filler is so great that the resulting conductive structure is obtained. There was a problem that the body was hard. On the other hand, in a conductive filler made of powder, it was necessary to use a large amount of conductive filler in order to obtain good conductivity.

JP 2004-224829 A JP 2003-187638 A Japanese Patent Laid-Open No. 2003-187639 JP 2004-189938 A

  The present invention has been made in view of the above background, and the object thereof is a fibrous conductive filler capable of obtaining a soft conductive structure, and a conductive resin composition containing the fibrous conductive filler. And providing a conductive structure containing the conductive resin composition.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventor has found that a desired conductive filler can be obtained by metal coating on organic fibers, and the present invention is completed by further intensive studies. It came.

  Thus, according to the present invention, “a fibrous conductive filler having a length L in the range of 0.5 to 100 μm, and the fibrous conductive filler is formed on the surface of the organic fiber and the organic fiber. A fibrous conductive filler characterized in that it comprises a coated conductive material.

  In that case, it is preferable that the diameter D of a fibrous conductive filler exists in the range of 0.1-2 micrometers. Moreover, it is preferable that ratio L / D of the said length L and the diameter D is 5 or more. The organic fiber is preferably a polyester fiber. In particular, the polyester fiber is preferably a polyester fiber obtained by dissolving and removing a sea component of a sea-island composite fiber composed of a sea component and an island component.

  In the fibrous conductive filler of the present invention, the conductive material is preferably a metal or a metal oxide. Moreover, it is preferable that this metal coating is by plating.

  In addition, according to the present invention, there is provided “a conductive resin composition containing a resin binder, a conductive filler, and a solvent, the conductive resin composition containing the fibrous conductive filler as a conductive filler”. Is done. In that case, it is preferable that electroconductive fine powder is contained in the said conductive resin composition as another component.

  According to the present invention, “a conductive structure comprising a base material and a conductive resin composition applied to the base material, wherein the conductive resin composition is the conductive resin composition”. Is provided. At that time, the substrate is preferably a fabric or a film.

  Moreover, according to this invention, the antenna and electromagnetic wave shielding material which use the said electroconductive structure are provided.

  According to the present invention, a fibrous conductive filler capable of obtaining a soft conductive structure, a conductive resin composition including the fibrous conductive filler, and a conductive structure including the conductive resin composition And an antenna and an electromagnetic wave shielding material using the conductive structure.

Hereinafter, embodiments of the present invention will be described in detail.
First, in the fibrous conductive filler of the present invention, it is important that the length L is in the range of 0.5 to 100 μm (preferably 1 to 10 μm). When the length L is less than 0.5 μm, when the conductive structure is obtained using the fibrous conductivity, the conductivity of the conductive structure is impaired, which is not preferable. Conversely, when the length is greater than 100 μm, it is not preferable because the conductive structure becomes hard when the conductive structure is obtained using the fibrous conductivity. Further, if the length L is larger than the cell of the gravure printing plate, there is a possibility that it cannot be used as an ink for gravure printing. It is assumed that the length is randomly sampled with an n number of 10, and the average value is obtained.

  Moreover, it is preferable that the diameter D of a fibrous conductive filler exists in the range of 0.1-2 micrometers (more preferably 0.1-1 micrometer). When the diameter D is larger than 2 μm, the conductive structure may become hard when the conductive structure is obtained using the fibrous conductivity. Moreover, when the diameter D is larger than the cells of the gravure printing plate, there is a possibility that it cannot be used as an ink for gravure printing. When the cross-sectional shape of the fibrous conductive filler is not a perfect circle, the average value of the long diameter (longest diameter) and the short diameter (shortest diameter) is obtained as the diameter.

  In the present invention, the organic fiber is obtained by copolymerizing a fiber-forming polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polylactic acid, and a third component in order to obtain the above ultrafine fiber diameter. Polyester fibers made of polyester such as polyester are preferred. In the polymer, a fine pore forming agent, a cationic dye dyeing agent, an anti-coloring agent, a heat stabilizer, a fluorescent whitening agent, a matting agent, a coloring agent may be added as necessary within the range not impairing the object of the present invention. 1 type (s) or 2 or more types of an agent, a hygroscopic agent, and inorganic fine particles may be contained.

  In particular, the polyester fiber is preferably a polyester fiber obtained by dissolving and removing a sea component of a sea-island composite fiber composed of a sea component and an island component. Such a polyester fiber can be produced, for example, by the following method.

  First, the above polyester is used as the island component polymer. On the other hand, the sea component polymer may be any polymer as long as the dissolution rate ratio with respect to the island component is 200 or more, but polyester, polyamide, polystyrene, polyethylene, and the like having good fiber forming properties are particularly preferable. For example, as an easily soluble polymer in an alkaline aqueous solution, polylactic acid, an ultra-high molecular weight polyalkylene oxide condensation polymer, a polyethylene glycol compound copolymer polyester, a copolymer polyester of polyethylene glycol compound and 5-sodium sulfonic acid isophthalic acid may be used. Is preferred. Nylon 6 is soluble in formic acid, and polystyrene and polyethylene are very well soluble in organic solvents such as toluene. Among them, in order to achieve both easy alkali solubility and sea-island cross-section formability, the polyester-based polymer is 3 to 10% by weight of polyethylene glycol having 6 to 12 mol% of 5-sodium sulfoisophthalic acid and a molecular weight of 4000 to 12000. % Copolymerized polyethylene terephthalate copolymer polyester having an intrinsic viscosity of 0.4 to 0.6 is preferred. Here, 5-sodium isophthalic acid contributes to improving hydrophilicity and melt viscosity, and polyethylene glycol (PEG) improves hydrophilicity. PEG has a higher hydrophilicity effect, which is thought to be due to its higher order structure, as the molecular weight increases, but it is preferable from the viewpoints of heat resistance and spinning stability because the reactivity becomes poor and a blend system is formed. Disappear.

  Next, the larger the number of islands, the higher the productivity in producing ultrafine fibers by dissolving and removing sea components, and the fineness of the resulting ultrafine fibers can also be reduced to 100 or more (more preferably 300-1000). If the number of islands is too large, not only the production cost of the spinneret increases, but also the processing accuracy itself tends to decrease.

  Next, the diameter of the island component is preferably in the range of 50 to 1000 nm. In such sea-island type composite fibers, the sea-island composite weight ratio (sea: island) is preferably in the range of 40:60 to 5:95, particularly preferably in the range of 30:70 to 10:90. Within such a range, the thickness of the sea component between the islands can be reduced, the sea component can be easily dissolved and removed, and the conversion of the island component into ultrafine fibers is facilitated. Here, when the proportion of the sea component exceeds 40%, the thickness of the sea component becomes too thick. On the other hand, when the proportion is less than 5%, the amount of the sea component becomes too small, and joining between the islands easily occurs.

  As the spinneret used for melt spinning, any one such as a hollow pin group for forming an island component or a group having a fine hole group can be used. For example, any spinneret that can form a cross section of the sea island by joining the island component extruded from the hollow pin or the fine hole and the sea component flow that is designed to fill the gap between them is compressed. .

  The discharged sea-island type cross-section composite fiber is solidified by cooling air, and is preferably wound after being melt-spun at 400 to 6000 m / min. The obtained undrawn yarn is made into a composite fiber having desired strength, elongation, and heat shrinkage properties through a separate drawing process, or is taken up by a roller at a constant speed without being wound once, and subsequently drawn. Any of the methods of winding after passing through may be used. Specifically, it is immersed in a hot water bath in the range of 60 to 100 ° C., preferably 60 to 80 ° C., and uniformly heated, the draw ratio is 10 to 30 times, the supply speed is 1 to 10 m / min, and the winding speed is It is preferable to carry out in the range of 300 m / min or less, particularly 10 to 300 m / min.

  After the sea-island type composite fiber is cut to the above length with a ball mill or the like, the sea component may be dissolved and removed with an alkaline aqueous solution.

  The conductive filler of the present invention is obtained by coating the surface of the organic fiber with a conductive substance. Preferred examples of the metal to be coated include metals such as copper, nickel, silver, chromium, gold, tin, iron, and aluminum having good conductivity, and metal oxides of these metals. Two or more kinds of these metals or metal oxides may be used in combination, or an alloy thereof may be used. However, since gold is an expensive material, a large amount of use may increase the cost. Further, copper and aluminum are materials that are easily oxidized, and their use is limited because changes in conductivity over time are recognized. Silver, nickel, and alloys thereof are preferably used. In particular, nickel and its alloys can be preferably used because they are chemically stable and low in cost.

  As a method of coating the metal on the organic fiber, electroless plating, vacuum deposition, sputtering, ion plating, metal spraying or mechanochemical method, or a known method of forming a thin film into a powder can be used. At that time, the thickness of the conductive material to be coated is preferably 0.05 μm to 0.5 μm (more preferably 0.07 to 0.15 μm).

Next, the conductive resin composition of the present invention contains a resin binder, the fibrous conductive filler, and a solvent. The resin binder is not particularly limited, but various modified polyester resins such as epoxy resin, polyester resin, urethane-modified polyester resin, epoxy-modified polyester resin, and acrylic-modified polyester resin, polyether urethane resin, polycarbonate urethane resin, vinyl chloride / acetic acid Vinyl copolymers, phenol resins, acrylic resins, polyamideimide resins, polyimide resins, polyamide resins, nitrocellulose, modified celluloses such as cellulose acetate acetate butyrate (CAB), cellulose acetate acetate propionate (CAP), etc. Is mentioned.
The weight ratio of the resin binder to the fibrous conductive filler is preferably in the range of 10 to 60 parts by weight with respect to 100 parts by weight of the resin binder.

  The solvent may be a known solvent such as toluene, and the weight ratio of the resin binder to the solvent is preferably in the range of 50 to 300 parts by weight with respect to 100 parts by weight of the resin binder.

  In addition, the conductive resin composition includes flaky silver powder, spherical silver powder, three-dimensional higher order silver powder, dendritic silver powder, graphite powder, carbon powder, nickel powder, copper powder, gold powder, palladium powder, aluminum powder, and indium powder. When the conductive fine powder is contained as other components, the conductivity is preferably improved. At that time, the size of the conductive fine powder is preferably in the range of 0.1 μm to 10 μm in diameter. The weight ratio between the resin binder and the conductive fine powder is preferably in the range of 10 to 50 parts by weight with respect to 100 parts by weight of the resin binder. The conductive resin composition of the present invention may contain a normal additive such as a dispersant, but preferably does not contain an inorganic fibrous conductive filler.

Next, the conductive structure of the present invention includes a base material and a conductive resin composition applied to the base material. As the base material, fabrics such as woven fabrics, knitted fabrics, and nonwoven fabrics, polyester films, and the like made of synthetic fibers such as polyester fibers are suitable. By adopting such a base material, a soft conductive structure can be obtained.

  The method for applying the conductive resin composition to the substrate is not particularly limited, and a gravure printing machine or the like may be used. Moreover, it is preferable that it is in the range of 2-100 micrometers as application | coating thickness of a conductive resin composition. If the coating thickness is less than 2 μm, sufficient conductivity may not be obtained. Conversely, if the coating thickness is greater than 100 μm, the conductive structure may be hardened.

  Since the conductive resin composition is applied to the conductive structure of the present invention, the conductive structure coated with the conductive resin composition containing an inorganic fibrous conductive filler such as carbon fiber is applied to the conductive structure. Compared with softness.

  Moreover, according to this invention, the antenna and electromagnetic wave shielding material which use the said electroconductive structure are provided.

Next, although the Example and comparative example of this invention are explained in full detail, this invention is not limited by these. In addition, each measurement item in an Example was measured with the following method.
(1) Length L of fibrous conductive filler
After sampling at random with n number of 10 and observing with a transmission electron microscope TEM to measure the length, the average value was obtained.
(2) Diameter D of fibrous conductive filler
The sample was randomly sampled with an n number of 10 and observed with a transmission electron microscope TEM to measure the diameter, and then the average value was obtained.
(3) Measurement of thickness The cross section of the sample was observed with a transmission electron microscope TEM, and the thickness was measured.

[Example 1]
Using polyethylene terephthalate as the island component, polyethylene terephthalate copolymerized with 9 mol% of 5-sodium sulfoisophthalic acid and 3% by weight of polyethylene glycol having a number average molecular weight of 4000 as the sea component (dissolution rate ratio (sea / island) = 230), A sea-island type composite unstretched fiber having sea: island = 30: 70 and number of islands = 836 was melt-spun at a spinning temperature of 280 ° C. and a spinning speed of 1500 m / min, and wound up once. The obtained undrawn yarn was roller-drawn at a drawing temperature of 80 ° C. and a draw ratio of 2.5 times, and then heat-set at 150 ° C. and wound up. The obtained sea-island type composite drawn yarn was 56 dtex / 10 fil. When the fiber cross section was observed with a transmission electron microscope TEM, the shape of the island was round and the diameter of the island was 600 nm.

  Subsequently, the sea-island type composite stretched yarn was shortcut-cut to a length of 1 mm by a fiber cutting device and subjected to alkali weight reduction treatment. Then, this fiber was further cut with a ball mill to obtain a polyester short fiber having a fiber diameter of 0.6 μm and an average length of 5 μm.

  Next, the polyester short fiber was coated with silver on the fiber surface by an electroless plating method to obtain a fibrous conductive filler. In the fibrous conductive filler, the thickness of the metal plating layer was 0.1 μm, the diameter was 0.8 μm, and the length was 5 μm.

  Next, 15 parts by weight of the fibrous conductive filler (silver-coated polyester fiber) in a high-speed dissolver (Inoue Seisakusho, model DHV), polyester urethane resin (manufactured by Nippon Synthetic Chemicals, model UR-8200) 20 as a binder resin A conductive resin composition was obtained by mixing 5 parts by weight with a blend of parts by weight and 65 parts by weight of toluene.

  Next, a conductive resin structure was obtained by printing the entire surface of the above-described conductive resin composition (conductive paste) on a 125 μm-thickness-treated polyester film with a gravure printer (Iwase Kikai Co., Ltd.). The printing characteristics were good. The coating thickness after drying at this time was 2.5 μm.

  The surface resistance value was measured with a surface resistance meter (manufactured by Mitsubishi Yuka Co., Ltd., model number: MCP-TESTER, MODELHT-210). As a result, the surface resistance value was 11 mΩ / □. When such a conductive structure was used as an antenna, it had excellent antenna performance. Further, the conductive structure was soft.

[Example 2]
Using the same fibrous conductive filler as in Example 1, 15 parts by weight of fibrous conductive filler (silver-coated polyester fiber), 15 parts by weight of silver fine powder in a high-speed dissolver, polyester urethane resin (Nippon Synthetic Chemical) as binder resin A conductive resin composition was obtained by blending 25 parts by weight of model UR-8200) and 60 parts by weight of toluene and stirring and mixing at 1200 rpm for 5 minutes.

Next, the above conductive paste was printed on the entire surface of the annealed polyester film having a thickness of 125 μm with a gravure printer. The printing characteristics were good. The coating thickness after drying at this time was 2.5 μm.
The surface resistance value was measured with a surface resistance meter (manufactured by Mitsubishi Yuka Co., Ltd., model number: MCP-TESTER, MODELHT-210). As a result, the surface resistance value was 3.3 mΩ / □.

[Comparative Example 1]
A conductive resin composition prepared by mixing 35 parts by weight of fine silver powder, 25 parts by weight of a fibrous conductive filler (silver-coated polyester fiber), and 60 parts by weight of toluene into a high-speed dissolver and stirring and mixing at 1200 rpm for 5 minutes. Got.

Next, the entire surface of the above-mentioned conductive resin composition (conductive paste) was printed on a 125 μm-thickness-treated polyester film with a gravure printing machine. The printing characteristics were good. The coating thickness after drying at this time was 2.5 μm.
The surface resistance value was measured with a surface resistance meter (manufactured by Mitsubishi Yuka Co., Ltd., model number: MCP-TESTER, MODELHT-210). As a result, the surface resistance value was 42 mΩ / □.

[Comparative Example 2]
In Example 2, the length of the fibrous conductive filler was changed to 200 μm, and 35 parts by weight of silver fine powder into the high-speed dissolver, fibrous conductive filler (silver-coated polyester fiber) (average length of 200 μm), binder resin A conductive resin composition was obtained by blending 25 parts by weight of a polyester urethane resin (manufactured by Nippon Synthetic Chemical Co., Ltd., model UR-8200) and 60 parts by weight of toluene and stirring and mixing at 1200 rpm for 5 minutes.

Next, the entire surface of the above-mentioned conductive resin composition (conductive paste) was printed on a 125 μm-thickness-treated polyester film with a gravure printing machine. Since the conductive fiber did not enter the gravure cell, the resulting film had poor surface smoothness, and uneven printing was observed in some areas where the appearance was not applied.
The surface resistance value was measured with a surface resistance meter (manufactured by Mitsubishi Yuka Co., Ltd., model number: MCP-TESTER, MODELHT-210). As a result, the surface resistance value varied greatly depending on the measurement location, and the maximum value was 24Ω / □ and the minimum value was 2Ω / □.

[Comparative Example 3]
Into a high-speed dissolver, 15 parts by weight of fine silver powder, 15 parts by weight of Toho Tenax Co., Ltd. carbon fiber (diameter 7 μm, length 6 mm), 40 parts of binder resin, and 110 parts of toluene were mixed and stirred at 1200 rpm for 5 minutes. The conductive resin composition was obtained by mixing.

  Next, the entire surface of the conductive resin composition was printed on an annealed polyester film having a thickness of 125 μm using a gravure printer. Since the conductive fiber did not enter the gravure cell, the finished film had poor surface smoothness, and was unevenly printed in some places that could not be applied in appearance. It was measured with a surface resistance meter (manufactured by Mitsubishi Yuka Co., Ltd., model number: MCP-TESTER, MODELHT-210). As a result, the surface resistance value varied greatly depending on the measurement location, and the maximum value was 110Ω / □ and the minimum value was 21Ω / □.

  According to the present invention, a fibrous conductive filler capable of obtaining a soft conductive structure, a conductive resin composition including the fibrous conductive filler, and a conductive structure including the conductive resin composition And an antenna and an electromagnetic wave shielding material using the conductive structure, and the industrial value thereof is extremely large.

Claims (13)

  A fibrous conductive filler having a length L in the range of 0.5 to 100 μm, the fibrous conductive filler comprising an organic fiber and a conductive material coated on the surface of the organic fiber. A fibrous conductive filler characterized by comprising.   The fibrous conductive filler according to claim 1, wherein the diameter D of the fibrous conductive filler is in the range of 0.1 to 2 µm.   The fibrous conductive filler according to claim 1 or 2, wherein in the fibrous conductive filler, a ratio L / D between the length L and the diameter D is 5 or more.   The fibrous conductive filler according to any one of claims 1 to 3, wherein the organic fiber is a polyester fiber.   The fibrous conductive filler according to claim 4, wherein the polyester fiber is a polyester fiber obtained by dissolving and removing a sea component of a sea-island composite fiber composed of a sea component and an island component.   The fibrous conductive filler according to any one of claims 1 to 5, wherein the conductive substance is a metal or a metal oxide.   The fibrous conductive filler according to any one of claims 1 to 6, wherein the metal coating is formed by plating.   A conductive resin composition comprising a resin binder, a conductive filler, and a solvent, wherein the conductive resin composition comprises the fibrous conductive filler according to claim 1 as a conductive filler.   The conductive resin composition according to claim 8, wherein the conductive resin composition contains conductive fine powder as another component.   The conductive structure which is comprised with the base material and the conductive resin composition apply | coated to this base material, and a conductive resin composition is the conductive resin composition of Claim 8 or Claim 9.   The conductive structure according to claim 10, wherein the base material is a fabric or a film.   An antenna using the conductive structure according to claim 10 or 11.   The electromagnetic wave shielding material which uses the electroconductive structure of Claim 10 or Claim 11.