JPH0389599A - Electromagnetic wave shield - Google Patents

Abstract

PURPOSE:To obtain an electromagnetic wave shield having fine effect in shielding not only electric field components but also magnetic field components by forming an amorphous metal or alloy coating layer of higher relative magnetic permeability than a specific value on, at least, one side of a nonwoven fabric including the specified synthetic fibers. CONSTITUTION:Synthetic fibers 2 composing the cores of fibers to be coated by metal or an alloy 3 are made of polyester, nylon, polypropylene, acrylic, or other materials and coated by metal or an alloy 3 by the plating method including electroless plating, the deposition method, or other methods. The resistivity is 2X10<-8>OMEGAm or lower and an upper layer is made of metal or an alloy such as a nonwoven mat 4 including 10 grammes or more of silvered fibers 1 per square meter. A lower layer is an amorphous metal or alloy coating layer 6 of 10<2> or higher relative magnetic permeability, obtaining an electromagnetic wave shield having a finer shielding effect than conventional electromagnetic wave shields.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to operating systems such as computers and word processors.
A-Device 1 relates to electromagnetic shielding materials used in communication devices, automotive electronic devices, electromagnetic interference measurement rooms (hereinafter referred to as electromagnetic shielding 11), and the like.

[Conventional technology]

Conventionally, paints, resins, etc. mixed with conductive fillers, metal foils such as iron, aluminum, copper, etc. have been used as electromagnetic shielding materials for advanced electronic devices such as OAR devices 1 communication devices.

In addition, in recent years, for example, JP-A-57-42196,
As shown in Japanese Unexamined Patent Publication No. 57-42197, etc., carbon fiber cloth or nonwoven fabric is used as a base material, and Japanese Unexamined Patent Application Publication No. 62-1
Non-woven fabric made of metal fibers such as stainless steel and copper as shown in No. 8799, or JP-A-63-26290
As shown in No. 0 and Utility Model Application Publication No. 63-157999, a nonwoven fabric made of metal-plated fibers and heat-fusible fibers has been proposed.

More recently, magnetic metals or alloys have been made into polyurethane,
Electromagnetic shielding materials made by impregnating foams such as polystyrene have also been developed.

[Problem to be solved by the invention]

By the way, among conventional electromagnetic shielding materials, paints and resins containing conductive fillers require (1) a step of coating on housings of electronic devices, etc., resulting in high costs.

(2) It is not possible to shield the cooling openings inside the device and the openings for connecting other parts such as switches, connectors, and keyboards.

There are other problems. In addition, foils and vapor deposited films made of iron, aluminum, copper, etc. (1) are hard and have poor flexibility, so they lack the ability to follow curved surfaces such as housings;

(2) Since it has no air permeability, it cannot be used as a cooling opening.

There are other problems. Furthermore, those using conductive fibers, such as carbon fibers and iron-based metal fibers such as stainless steel, have high resistivity. It is necessary to blend a large amount of the above-mentioned fibers, and metal fibers have poor formability and are expensive.

For products using metal-plated fibers, nickel or copper is generally selected as the plating metal due to cost considerations, but nickel alone has high resistivity and high electromagnetic shielding properties, especially for electric fields. The ingredients are not as expected. Also,
In the case of copper, although high effectiveness can be obtained, it has the disadvantage of being easily oxidized, and its resistance gradually increases, leading to a decrease in effectiveness. Furthermore, in order to prevent the oxidation of copper and improve the shielding properties of electromagnetic waves from magnetic fields, it has been proposed that nickel plating is applied on top of the copper plating. In other words, due to the skin effect of high-frequency current, the high resistivity of nickel cannot be ignored, and there is a limit to the shielding ability of electric field components in the high-frequency region.

Furthermore, when a foam such as polyurethane or polystyrene is impregnated with a magnetic metal, there is a problem in that the resistivity of the magnetic metal or alloy is high and the shielding properties of the electric field component of electromagnetic waves are insufficient.

[Means to solve the problem]

In order to solve the above problems, the present invention has electrical conductivity, can be processed into a non-woven fabric, and has a resistivity of 2XI.
Synthetic fibers coated with a metal or alloy of O-'Ω・m or less are used, and the metal-coated fibers are coated with at least 1Og/m.
A metal or alloy having a relative magnetic permeability of 102 or more, preferably a 7-magnetic material such as iron or nickel, or generally MO' This problem has been solved by providing a coating layer of a ferrimagnetic amorphous metal or alloy represented by exO, (M: divalent metal ion), and creating a structure that exhibits the ability to shield the magnetic field component of electromagnetic waves. .

[Effect]

By adopting the above structure, the amount of conductive fiber used can be reduced, manufacturing cost is low, and compared to electromagnetic shielding materials with the same level of conductivity, it is superior in terms of not only electric field components but also magnetic field components. An electromagnetic shielding material having a shielding effect can be provided. In addition, since it has a non-woven structure, it can be used for cooling openings etc. by utilizing its breathability, and can exhibit an electromagnetic wave shielding effect with excellent curved surface followability.

〔Example〕

Hereinafter, an example of implementation of the present invention will be described based on the drawings.

As shown in FIG. 1, (1) is a partially enlarged view of a fiber coated with a metal or alloy used in the present invention, and a synthetic edge constituting the core of the fiber coated with a metal or alloy (3). , Im (2) is selected from polyester, nylon, polypropylene, acrylic, etc., and is a metal or alloy (3).
) is selected from a plating method including an electric field, a vapor deposition method, etc., and the resistivity is 2XIO-'Ω·m or less, for example, silver.

Copper, silver-containing copper, etc. are selected, and silver is preferably used. The metal or alloy coated edge 1! The amount used in (1) can be set arbitrarily depending on the required shielding effect, but to obtain a shielding effect of about 50 dB, mixing at 10 g/% is far enough, and even when higher effects are required. A slight increase in quantity is sufficient.

FIG. 2 is a schematic cross-sectional view of the electromagnetic shielding material of the present invention, and the upper layer is a nonwoven fabric mat (4) containing metal or alloy, for example, silver-coated fibers (1) of 10g/m2 or more. This upper layer may be composed of other non-plated fibers, such as natural fibers such as cotton wool, recycled fibers such as rayon, or synthetic fibers such as nylon and polyester, either alone or in combination, as desired. The lower layer is a coating layer (6) of an amorphous metal or alloy with a relative magnetic permeability of 10" or more, and its thickness is preferably about 300 to 1000X, considering the shielding effect and the curved surface followability of the nonwoven mat. The metal or alloy is selected depending on the desired effect.

Furthermore, the amorphous metal or alloy coating layer (6) can be provided on both sides of the non-woven mat (4) as shown in FIG. 3 or in the middle layer of the non-woven mat (4) as shown in FIG. , the form of the electromagnetic shielding material can be arbitrarily selected depending on the application.

A more detailed explanation will be given below using specific examples.

〔Example〕

Silver (conductivity 1-62XIO4Ω) on acrylic fiber m1.5d
・rn) A nonwoven fabric with a total area weight of 45 g/m2, in which 15 g/m2 of binder resin is attached by dipping to a random or cross web formed by mixing 10 g/m2 of plated fibers and 20 y/rd of polyester fiber. I made mat A. The mat is made of MnFe with a relative magnetic permeability of 250.
, O, was formed on one side with an amorphous alloy coating layer having a thickness of 500× by a method such as ion vapor deposition or sputtering to serve as an electromagnetic shielding material.

[Comparative Example 1] An electromagnetic shielding material was formed in the same manner as in the example using a web formed from a mixed fiber of 5 g/rrr of the same plated fibers as in the example and 25 g/m2 of polyester fiber, and then compared. Example (1) was obtained.

[Comparative Example 2] MnFe0. Amorphous film thickness 50
A comparative example (2) was prepared by providing a coating layer on 0X.

[Comparative Example 3] Comparative Example (3) was prepared in which a coating layer of an amorphous metal of nickel (relative magnetic permeability: 40) with a thickness of 500 mm was provided on one side of the nonwoven fabric mat A obtained in the example.

[Comparative Example 4] Only the nonwoven fabric mat A obtained in the example was designated as Comparative Example (4).

The shielding properties of the electromagnetic wave shielding materials obtained in the above Examples and Comparative Examples for electric field components and magnetic field components were measured, respectively, and the electromagnetic wave shielding effects are shown in Figures 5 and 6. The results showed that the shielding effect was even higher than that in comparison.

[Effects of the Invention] Since the present invention is constructed as described above, an electromagnetic shielding material having a superior shielding effect compared to conventional electromagnetic shielding materials can be obtained, and is effective against both electric and magnetic fields, and is conductive. It also requires less use of synthetic fibers, making it possible to provide an inexpensive shielding material.

Furthermore, since it employs a non-woven structure, it has excellent effects such as being able to shield areas that are difficult to shield conventionally, such as ventilation holes.

[Brief explanation of drawings]

FIG. 1 is a partially enlarged perspective view of a metal- or alloy-coated synthetic fiber used in the present invention. FIG. 2 is a schematic sectional view showing an example of implementing the present invention. 3 and 4 are schematic sectional views showing other embodiments. FIG. 5 and FIG. 6 are graphs showing the shielding effects of Examples and Comparative Examples. (1)...- Metal or alloy coated fiber (2)...
...Synthetic fiber (3) ...Metal or alloy (4) ...Nonwoven fabric mat (5) ...Non-plated fiber (6> ...Amorphous Metal or alloy coating layer

Claims (1)

[Claims] (1) At least 10g/synthetic fiber coated with a single metal or alloy with a resistivity of 2×10^-^3Ω・m or less
1. An electromagnetic shielding material comprising: a nonwoven fabric containing m^2 or more; and a coating layer of an amorphous metal or alloy having a relative magnetic permeability of 10^2 or more on at least one side.