JP2009267230A - Electromagnetic wave shielding material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnetic wave shielding material that is light in weight and excellent in breathability and flexibility, and has a shielding effect to an electromagnetic wave from a wide incident angle. <P>SOLUTION: In an electromagnetic wave shielding material, a conductive metal layer 22 with high magnetic permeability is formed on the surface of one side or both sides of a fiber cloth comprising fiber 21 with a diameter of 10 μm or smaller to cover the surface of the fiber 21, so that the clearance between the fibers is not filled. Thus, the electromagnetic wave shielding material has breathability and is light in weight and excellent in flexibility. The conductive metal layer 22 is hardly broken even if bent, and excellent in durability. Moreover, a difference in shielding effects caused by the incident angle of the electromagnetic wave hardly appear due to the effect of the recessed and projected shape of the surface of the electromagnetic wave shielding material. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fiber cloth and an electromagnetic wave shielding material that has a conductive metal coating layer on the surface of the fiber cloth, is thin and lightweight, and has excellent air permeability and flexibility.

  As a conventional technique, there is a metal-coated fiber cloth for electromagnetic wave shielding disclosed in JP-A-2005-59580. In this method, the surface of the fiber cloth is coated with, for example, polyurethane so that the surface becomes smooth to form an interface layer, and the surface of the interface layer is coated with a metal layer.

Accordingly, the metal-coated fiber cloth for electromagnetic wave shielding has no air permeability and is inferior in flexibility because the interface layer fills the gap between the fiber cloths. For this reason, when the metal-coated fiber cloth for electromagnetic wave shielding is used for clothing or the like, it becomes extremely uncomfortable.
JP-A-2005-59580

In order to use the metal-coated fiber cloth for electromagnetic shielding in clothing, etc., it must be thin and lightweight, be breathable, have excellent flexibility, and have a shielding effect against electromagnetic waves from a wide incident angle. This is an important issue. The present invention has been made to solve these problems.

  An electromagnetic wave shielding material according to the present invention made to achieve the above object comprises a fiber cloth and a conductive metal layer formed on one or both surfaces of the fiber cloth, and the conductive metal layer is a fiber. The surface of the fiber near the surface of the cloth is covered, and the conductive metal layer does not fill the gap between the fibers, and has air permeability through the gap between the fibers.

  The fiber cloth is made of fibers having a diameter of 10 μm or less, and is a woven fabric, a knitted fabric, a nonwoven fabric, a composite of a woven fabric and a nonwoven fabric, a composite of a knitted fabric and a nonwoven fabric, a composite of a woven fabric and a knitted fabric, or a composite of a woven fabric, a knitted fabric and a nonwoven fabric. One of the body.

The conductive metal layer may be formed on one or both surfaces of the fiber cloth by at least one of a vacuum process, a spray method, and an electrodeposition method. The vacuum process is a process for forming a conductive metal layer under vacuum or reduced pressure, such as sputtering, vapor deposition, or ion plating.

Further, the material of the conductive metal layer preferably has a high magnetic permeability that is 100 times or more higher than the initial magnetic permeability.

As the fiber constituting the nonwoven fabric of the fiber cloth, polyacrylonitrile fiber produced by an electrospinning method is suitable.

The fiber cloth can be mechanically reinforced by laminating the fiber cloth with another reinforcing fiber cloth. Moreover, the said conductive metal layer can be protected by laminating | stacking another reinforcing fiber cloth on the surface side in which the conductive metal layer of the said fiber cloth was formed.

  The electromagnetic shielding fiber cloth of the present invention has a gap between fibers and has air permeability. Further, by using thin fibers having a diameter of 10 μm or less for the fiber cloth, the fiber cloth is thin and lightweight, and is excellent in flexibility and durability.

Furthermore, since the electromagnetic shielding fiber cloth of the present invention has a small shielding effect difference due to the incident angle of electromagnetic waves, it has a shielding effect against electromagnetic waves from a wide range of incident angles, and various uses requiring an electromagnetic shielding effect. Is available. In particular, it can be used for electromagnetic shielding clothing, information communication devices for electromagnetic wave countermeasures, and medical devices such as cardiac pacemakers.

The electromagnetic wave shielding material of the present invention comprises a fiber cloth and a conductive metal layer formed on one or both surfaces of the fiber cloth, and the conductive metal layer covers the surface of the fiber near the surface of the fiber cloth. The conductive metal layer does not fill the gap between the fibers, and has air permeability through the gap between the fibers.

The fiber cloth is made of fibers having a diameter of 10 μm or less, is thin and lightweight, and has excellent flexibility and durability. The diameter of the fiber is preferably 1 μm or less. When the fiber cloth is made of fibers having a diameter of 10 μm or less, the conductive metal layer formed on the surface of the fibers is not easily damaged even when bent to a small bending radius. For example, when a fiber having a diameter of 10 μm is bent to a bending radius of 1 mm, the difference in strain between the outer surface and the inner surface of the fiber is about 1%. In this case, the possibility that the conductive metal layer formed on the surface of the fiber is broken and dropped off is low. Furthermore, in the case of a fiber cloth made of fibers having a diameter of 1 μm or less, the strain difference when a fiber having a diameter of 1 μm is bent to a bending radius of 1 mm is further reduced to about 0.1%.

The fiber fabric is at least one of a woven fabric, a knitted fabric, a nonwoven fabric, a composite of a woven fabric and a nonwoven fabric, a composite of a knitted fabric and a nonwoven fabric, a composite of a woven fabric and a knitted fabric, or a composite of a woven fabric, a knitted fabric and a nonwoven fabric. . The composite is formed by laminating at least two types of woven fabric, knitted fabric and non-woven fabric into an integral cloth shape. Further, the fiber cloth is used in a shape suitable for the shape of an object to be shielded against electromagnetic waves, such as a sheet, a ribbon, a string, a cylinder, and a bag.

The conductive metal layer is formed on one or both surfaces of the fiber cloth by at least one of a vacuum process, a spray method, and an electrodeposition method. At this time, the conductive metal layer covers the surface of the fiber near the surface of the fiber cloth, does not fill the gap between the fibers, and is not formed inside the fiber cloth. For this reason, the fiber cloth has air permeability through the gaps between the fibers.

The vacuum process for forming the conductive metal layer means a film forming process in a vacuum or reduced pressure state such as a sputtering method, a vacuum deposition method, or an ion plating method.

The conductive metal layer is directly formed on the surface of the fiber constituting the surface of the fiber cloth, and there is no metal layer in the gap between the fibers. Therefore, the shape of the conductive metal layer is uneven, reflecting the uneven surface formed by the fiber group present on the surface of the fiber cloth. For this reason, the electromagnetic wave shielding material of the present invention has a portion of a conductive metal layer having an effective shielding effect with respect to the incident angle even when the incident angle of the electromagnetic wave varies, and is shielded by the incident angle of the electromagnetic wave. Difficulty in effect.

In the conventional technique, the surface of the fiber cloth is covered with an airtight interface layer in a planar shape, and the surface of the interface layer is covered with a metal layer. Therefore, the metal layer was a single metal thin film. In general, a metal thin film having a single planar shape has a difference in shielding effect depending on the incident angle of electromagnetic waves. On the other hand, the electromagnetic wave shielding material of the present invention has a shielding effect against electromagnetic waves from a wide incident angle as described above.

The conductive metal layer is made of a high permeability material having an initial permeability of 100 times or more of a vacuum permeability. Thus, when the conductive metal layer is made of a high permeability material, it can absorb not only electric field energy but also magnetic field energy from electromagnetic waves, and the electromagnetic wave shielding material of the present invention has a larger electromagnetic wave shielding effect. Can have.

Examples of the high magnetic permeability material for the conductive metal layer include iron, nickel, silicon steel, alpalm, permendur, sendust, permalloy, supermalloy, mu metal, and metaglass. A conductive metal layer made of at least one of these high magnetic permeability materials is formed on the surface of the fiber cloth.

The fibers constituting the nonwoven fabric used for the fiber cloth are preferably polyacrylonitrile fibers produced by an electrospinning method. Nonwoven fabric can be made of fibers with a smaller diameter than craft cloth, polyacrylonitrile fiber made by electrospinning method, and if thin fibers with a diameter of 10 μm or less are used, the fiber cloth is thin and lightweight, Excellent flexibility and durability. However, the nonwoven fabric fibers are not limited to polyacrylonitrile fibers produced by the electrospinning method, and other high molecular chemical fibers can be used as long as the diameter is 10 μm or less.

The fiber cloth is made of fine fibers having a diameter of 10 μm or less, and high mechanical strength may not be expected by itself. In order to ensure high mechanical strength, excellent air permeability and mechanical strength are obtained by laminating a high-strength fiber cloth as a reinforcing material on the fiber cloth having the conductive metal layer according to claim 3 on the surface. It becomes an electromagnetic shielding material. In addition, by covering the surface of the fiber cloth having the conductive metal layer with a high-strength fiber cloth, the conductive metal layer formed on the surface of the fiber cloth can be protected and wear can be suppressed.

  The structure of the electromagnetic wave shielding material in which the fiber cloth of the present invention is a nonwoven fabric is schematically shown in FIG. An enlarged view of the end 2 of the electromagnetic shielding material 1 is shown in FIG. The electromagnetic shielding material 1 includes a fiber fabric 11 having a nonwoven fabric structure using fibers 21 and a conductive metal layer 22 formed on the surface thereof. The thickness of the electromagnetic shielding material 1 can be adjusted according to the application.

  The fiber 21 constituting the fiber cloth 11 of FIG. 1 is polyacrylonitrile produced by an electrospinning method, and the fiber diameter is 10 μm or less, preferably 1 μm or less. In addition, although polyacrylonitrile is preferable as a fiber, it is not limited to this.

  When a permalloy of an alloy of nickel and iron is used as the conductive metal layer 22 and formed by sputtering, the conductive metal layer 22 effective for shielding electromagnetic waves can be obtained by sputtering for about 15 minutes as in the following example. . The magnetic permeability of permalloy is approximately 8000 times that of vacuum.

  As shown in FIG. 2, the conductive metal layer 22 is formed on the surface of the fiber 21 a constituting the surface of the fiber cloth 11, and hardly formed on the surface of the fiber 21 b existing inside the fiber cloth 11. Further, the conductive metal layer 22 does not exist in the gap between the fibers 21.

A non-woven fabric of polyacrylonitrile fiber having a diameter of 500 to 600 nm is used as a fiber fabric, and a conductive metal layer is formed on the surface of one side of the non-woven fabric using a nickel-iron alloy permalloy by a sputtering method for about 15 minutes. A 110 μm electromagnetic shielding material was produced. The electromagnetic wave shielding rate was measured for the electromagnetic wave shielding material. The electromagnetic wave shielding rate was measured with a network analyzer sandwiching an electromagnetic wave shielding material between the connection surfaces of the two waveguides. The results are shown in FIG.

The vertical axis represents the shielding rate%, and the horizontal axis represents the electromagnetic wave frequency 1 to 13 GHz. A curve 31 represents the electromagnetic wave shielding rate of the electromagnetic wave shielding material 1 of the present invention. Referring to the curve 31, the electromagnetic wave shielding material 1 of the present invention exhibits an electromagnetic wave shielding rate of 85% or more when the frequency of electromagnetic waves is in the range of 1 to 13 GHz, and exhibits an electromagnetic wave shielding rate of 90% or more in most of the range. ing.

  The electromagnetic wave shielding material 1 is a case where the conductive metal layer 22 is formed on one surface of the fiber cloth 11. When the conductive metal layer is formed on both sides of the fiber cloth, there are two conductive metal layers, so that the electromagnetic wave shielding rate is 98 to 99% or more in the frequency range of 1 to 13 GHz. Be expected. Moreover, it is possible to further improve the electromagnetic wave shielding rate by stacking such electromagnetic wave shielding materials in multiple layers. In addition, by laminating the electromagnetic shielding material with a fiber cloth having high mechanical strength, a breathable electromagnetic shielding material with enhanced mechanical strength is obtained.

It is a schematic diagram which shows the structure | tissue of the electromagnetic wave shielding material of this invention. It is the schematic diagram which expanded the edge part of the electromagnetic wave shielding material of this invention. It is a figure which shows the electromagnetic wave shielding rate of the electromagnetic wave shielding material of this invention.

Explanation of symbols

1: Electromagnetic wave shielding material 2: End part of electromagnetic wave shielding material 11: Fiber cloth 21, 21a, 21b: Fiber 22: Conductive metal layer 31: Curve showing the electromagnetic wave shielding rate of the electromagnetic wave shielding material of the present invention

Claims (8)

It comprises a fiber cloth and a conductive metal layer formed on one or both surfaces of the fiber cloth. The conductive metal layer covers the surface of the fiber near the surface of the fiber cloth, and the conductive metal layer is between the fibers. An electromagnetic wave shielding material characterized by having air permeability through the gap between fibers without filling the gap.   The electromagnetic shielding material according to claim 1, wherein the fiber cloth is made of fibers having a diameter of 10 μm or less. 2. The fiber cloth is any one of a woven fabric, a knitted fabric, a nonwoven fabric, a woven fabric / nonwoven fabric composite, a knitted fabric / nonwoven fabric composite, a woven fabric / knitted fabric composite, or a woven fabric / knitted fabric / nonwoven fabric composite. Or the electromagnetic wave shielding material of 2. The electromagnetic wave shielding material according to any one of claims 1 to 3, wherein the conductive metal layer is formed on one or both surfaces of the fiber cloth by at least one of a vacuum process, a spray method, and an electrodeposition method. . The electromagnetic wave shielding material according to claim 4, wherein the vacuum process for forming the conductive metal layer is a process for forming the conductive metal layer under a vacuum or a reduced pressure such as sputtering, vapor deposition, or ion plating. The electromagnetic shielding material according to claim 1, wherein the conductive metal layer is made of a high magnetic permeability material having an initial magnetic permeability of 100 times or more of a vacuum magnetic permeability. The electromagnetic wave shielding material according to any one of claims 1 to 6, wherein the fibers constituting the nonwoven fabric of the fiber cloth are polyacrylonitrile fibers produced by an electrospinning method. The electromagnetic wave shielding material according to claim 1, wherein the fiber cloth is laminated with another reinforcing fiber cloth.