JP2000124658A - Electromagnetic wave shielding material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve both electromagnetic wave shielding effect and machining property by dispersing and arranging a coil-shaped carbon fiber in a resin or a wax particle as a particle containing a coil-shaped carbon fiber. SOLUTION: A coil-shaped carbon fiber 21 is dispersed and arranged in a resin or a wax 22, adjusting particles 11 containing a coil-shaped carbon fiber. In particular, by forming a monomer solution where the coil-shaped carbon fiber 21 is dispersed into emulsion and then manufacturing it using a method for polymerization, the particle 11 containing a coil-shaped carbon fiber where the coil-shaped carbon fiber 21 is arranged efficiently can be manufactured. An electromagnetic wave shielding material 1 is of a structure, where the particle 11 containing a coil-shaped carbon fiber is dispersed in a binder 12, thus performing machining without deforming a coil shape in use by dispersing into the resin solution and improving the electromagnetic wave shielding effect.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic wave shielding material which is regarded as important in the field of electronic devices such as personal computers, audio products, home electric appliances, and mobile phones. The present invention relates to an electromagnetic wave shielding material having excellent characteristics.

[0002]

2. Description of the Related Art Conventionally, as an electromagnetic wave shielding material, a low-resistance metal sheet or metal foil, a metal plating, a metal plating, a metal or a metal oxide, an electrostatic shield generally used for an electronic device main body, and a high frequency. There is a magnetic shield made of a magnetic material or the like having a high magnetic permeability, which is used depending on the application.

[0003] Specifically, indium oxide, gold,
There are known copper, silver, tin oxide, indium oxide, and the like formed into a thin film by vapor deposition. However, these have problems that the manufacturing process is complicated and the cost is high.

[0004] As another form, there is known a conductive powder, flake, or fiber such as silver, copper, nickel, aluminum, carbon, metal fiber, carbon fiber, or metal glass fiber mixed in a resin. ing. These are low-cost and the manufacturing process is simple, but the electromagnetic wave shielding effect is insufficient.

Further, as another form, for example,
-104927, JP-A-3-227412, JP-A-4-222228, JP-A-10-37
As described in Japanese Patent Application Publication No. 024, a coiled fiber is known instead of a linear fiber. In particular, the coiled carbon fibers generate an induced current and have a high effect of completely absorbing electromagnetic waves.

However, when this is processed as an electromagnetic wave shielding material, a method of mixing it into a resin is used. However, there is a disadvantage that the coil-shaped material is broken at the time of mixing.

[0007]

As described above, the conventional electromagnetic wave shielding material has a shielding effect but is poor in workability when a metal or metal oxide film is used, and has good workability when conductive particles are used. When conductive fibers having a low shielding effect and a high shielding effect were used, the workability was poor. Accordingly, an object of the present invention is to provide an electromagnetic wave shielding material having both an electromagnetic wave shielding effect and good workability.

[0008]

Means for Solving the Problems The present invention has been made to achieve the above object, and the invention according to claim 1 is an electromagnetic wave shielding material containing coiled carbon fibers, wherein the coiled carbon fiber An electromagnetic wave shielding material characterized in that fibers are dispersed and arranged in resin or wax particles to form coiled carbon fiber-containing particles.

According to a second aspect of the present invention, there is provided the electromagnetic wave shielding material according to the first aspect, wherein the carbon fiber-containing particles are dispersed in a binder.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail with reference to the drawings showing embodiments.

FIG. 1 is a cross-sectional view showing one embodiment of the electromagnetic wave shielding material 1 of the present invention, and shows a configuration in which a coil-like carbon fiber-containing particle 11 containing a coil-like carbon fiber or the like is dispersed in a binder 12. ing.

FIG. 2 is a cross-sectional view showing an embodiment of the coiled carbon fiber-containing particles used in the present invention.
Are dispersed in the resin or the wax 22.

As the coiled carbon fiber 21, various coiled carbide fibers such as carbon, silicon carbide (SiC) and titanium carbide (TiC) can be used.
With a fiber of 0.5 to 5 μm, the coil outer diameter is 2 to 1 of the fiber diameter.
0 times, the number of turns is 10 μm
Those having a range of 50 times are good. Here, in order to stably disperse the coiled carbon fibers 21 in the resin 22,
It is preferable to perform a fatty acid treatment, a higher ester treatment, a silane coupling treatment, and a coating treatment with various resins.

As the resin, for example, an organic material such as an acrylic resin, a methacrylic resin, a polystyrene, a polyester resin, a polyurethane resin, a polyurea resin, a polyamide resin, an epoxy resin, a natural resin, or an inorganic material, alone or in combination of two or more. It is also possible to use a mixture. In particular, a material having high conductivity is preferable. It is also possible to use a UV curable resin or an electron beam curable resin. UV-curable resins are compounds having an ethylenically unsaturated group capable of free radical addition polymerization or crosslinkable, and having at least one ethylenically unsaturated group, for example, a monomer having a vinyl group or an allyl group, An oligomer, a polymer having an ethylenically unsaturated group at a terminal or a side chain, or the like can be used. Further, a compound capable of radical polymerization, an epoxy compound capable of cationic polymerization,
An oxetane compound, a vinyl ether compound, or a generally known resin that can be crosslinked with a crosslinking agent can be used. As the compound capable of undergoing radical polymerization, a compound having at least one ethylenically unsaturated double bond in a molecule is preferable. Epoxy compounds include bisphenol A, bisphenol AD, bisphenol B,
Compounds formed by a condensation reaction between various phenol compounds such as bisphenol S and epichlorohydrin can be used. As the oxetane compound, xylylene oxetane, oxetane alcohol and the like can be used. As the vinyl ether compound, resins such as diglycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, polyethylene glycol diglycidyl ether, vinyl-n-butyl ether, and trimethylolethanetrivinyl ether can be used.

Natural waxes such as paraffin wax and carnauba wax which are solid at room temperature or synthetic waxes such as carboxylic acid wax, fatty acid wax and petrolatum can be used alone or in combination as appropriate.

The above-described coiled carbon fiber 21 is dispersed and arranged in a resin or wax 22 to prepare the coiled carbon fiber-containing particles 11.

The method for producing the above-described coiled carbon fiber-containing particles 11 includes a method in which the coiled carbon fiber 21 is dispersed in a resin solution and then the solvent is removed and pulverized, and a method in which the coiled carbon fiber 21 is dispersed in the resin solution. A liquid resin (including a monomer) or a wax, such as a method of curing in a liquid in which the solvent is removed after forming the emulsion into an emulsion, a method of forming an emulsion from a monomer solution in which the coiled carbon fiber 21 is dispersed, and the method of polymerizing the coiled carbon fiber. And then hardening.

In particular, by manufacturing using a method in which a monomer solution in which the coiled carbon fibers 21 are dispersed is converted into an emulsion and then polymerized, the coiled carbon fiber-containing particles 11 in which the coiled carbon fibers 21 are efficiently arranged are formed. Can be manufactured.

By using the coiled carbon fiber as the coiled carbon fiber-containing particles as described above, it becomes possible to work without breaking the shape of the coil when used by dispersing in a binder solution described later.

The average particle size of the coil-shaped carbon fiber-containing particles is not particularly limited, but is preferably 50 to 200 μm in consideration of dispersibility in a binder and appropriate printing and coating.
m is preferable.

Next, the electromagnetic wave shielding material 1 according to claim 2
Is a configuration in which the coiled carbon fiber-containing particles 11 having the above-described configuration are dispersed in a binder 12, as shown in FIG.

Examples of the binder 12 include polyvinyl alcohol, polyvinylpyrrolidone, sodium polyacrylate, polyacrylamide, polyethyleneimine,
Aqueous binders such as gelatin, gum arabic, cellulose derivatives, sodium alginate, melamine, and urea resins; solvent-based binders such as acrylic resins, urethane resins, polystyrene, polyvinyl chloride, and styrene-maleic acid resins; and styrene-maleic acid Emulsion binders such as a polymer, a latex such as a methyl methacrylate-to-butadiene copolymer, a latex of an acrylic polymer, and a latex of a vinyl polymer are appropriately used.

By dispersing the coil-shaped carbon fiber-containing particles in the binder solution and converting the electromagnetic wave shielding material into an ink, coating can be performed regardless of the shape of the adherend requiring the electromagnetic wave shielding material. It is possible to form a layer.

Examples of the method for forming the layer made of the electromagnetic wave shielding material include well-known printing methods such as a gravure printing method, an offset printing method, and a silk screen printing method; A method such as a coating method can be used, and the method can be appropriately selected from the above methods according to the shape, application, quantity, and the like of the adherend to be manufactured.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to specific embodiments.

Example 1 15 parts by weight of coiled carbon fibers subjected to a silane coupling treatment were uniformly dispersed in 100 parts by weight of a 20% styrene ethyl acetate solution. Parts by weight, and using a homogenizer, the number of revolutions was 2000 rpm.
For about 5 minutes so as to have an average particle size of 75 μm.
This dispersion was heated to 80 ° C., and ethyl acetate was removed by evaporation to produce coiled carbon fiber-containing particles.

A coating liquid in which the obtained coil-shaped carbon fiber-containing particles were uniformly dispersed in an aqueous polyvinyl alcohol solution was applied on a PET film to form a layer of an electromagnetic wave shielding material.

When the electromagnetic wave shielding effect of the formed electromagnetic wave shielding material was measured, it was found that the frequency was 30 MHz to 500 MHz.
, The electric field attenuation of -35 dB was exhibited.

Example 2 15 parts by weight of coiled carbon fibers subjected to higher ester treatment were uniformly dispersed in 60 parts by weight of a styrene monomer, and 0.6 parts by weight of an azo polymerization initiator was added. This dispersion was dispersed in 200 parts by weight of a 5% aqueous gelatin solution, and the number of revolutions was 3000 using a homogenizer.
The dispersion was performed for about 5 minutes so that the average particle size was 60 μm at rpm. Nitrogen was introduced into the dispersion, heated to 80 ° C., and polymerized for 12 hours to produce coiled carbon fiber-containing particles.

A coating liquid in which the obtained carbon fiber-containing particles were uniformly dispersed in an aqueous polyvinyl alcohol solution was applied on a PET film to form a layer of an electromagnetic wave shielding material.

When the electromagnetic wave shielding effect of the formed electromagnetic wave shielding material was measured, it was found that the frequency was 30 MHz to 500 MHz.
, The electric field attenuation of -35 dB was exhibited.

[0032]

According to the electromagnetic wave shielding material of the present invention, in the electromagnetic wave shielding material containing coiled carbon fiber,
By using the coil-shaped carbon fiber as the particle containing the coil-shaped carbon fiber, it is possible to perform processing without breaking the coil shape when used by dispersing in a resin solution, and the electromagnetic wave shielding effect is enhanced.

Further, by dispersing the coil-shaped carbon fiber-containing particles in the binder solution and converting the electromagnetic wave shielding material into ink, coating can be performed regardless of the shape of the adherend requiring the electromagnetic wave shielding material. It is possible to form a different layer.

[0034]

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of an electromagnetic wave shielding material of the present invention.

FIG. 2 is a cross-sectional view showing one example of the coiled carbon fiber-containing particles used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electromagnetic wave shielding material 11 Coiled carbon fiber-containing particles 12 Binder 21 Coiled carbon fiber 22 Resin or wax

Claims (2)

[Claims] 1. An electromagnetic wave shielding material containing coiled carbon fiber, wherein the coiled carbon fiber is dispersed and arranged in resin or wax particles to obtain coiled carbon fiber-containing particles. 2. The electromagnetic wave shielding material according to claim 1, wherein said coiled carbon fiber-containing particles are dispersed in a binder.