JP2003133785A - Fiber structural composition having electromagnetic absorbability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fiber structural composition having electromagnetic absorbability, the composition being flexible and light in weight and showing effective performance, and further having air permeability, acoustic insulation and damping performance. SOLUTION: The composition includes 30% to 500% of magnetic substance particles as a percentage of the weight of the fiber. It is preferred that an electromagnetic reflection layer and/or a protection layer be provided on the surface of the composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic wave absorbing fiber structure composite which has a high electromagnetic wave absorbing property and is flexible and has good workability.

[0002]

2. Description of the Related Art In recent years, the electromagnetic wave environment has deteriorated due to the widespread use of electromagnetic waves in many fields. Among them, as electromagnetic wave interference, there are communication interference in communication using radio waves, television electromagnetic interference due to buildings, and generation of jamming electromagnetic waves. There is a problem such as malfunction of the electronic circuit due to. In order to prevent such an obstacle, a measure has been taken to suppress the reflection or leakage of the electromagnetic wave that causes the obstacle by installing an electromagnetic wave absorber using a material that absorbs the electromagnetic wave in the vicinity of the reflecting surface or the electronic circuit.

The electromagnetic wave absorbing material is a material that converts electromagnetic wave energy into heat energy, and the electromagnetic wave loss can be broadly classified into three types: conduction loss, dielectric loss, and magnetic loss (Yasutaka Shimizu). Author "Absorption and shielding of electromagnetic waves", 1989 Nikkei technical book, etc.). The conductive loss is an action of absorbing an electromagnetic wave by a conductive current flowing through the resistor, and an electromagnetic wave absorbing material utilizing this action includes a woven fabric made of a conductive fiber. Dielectric loss is a process in which a dielectric is mixed with an insulator to form a circuit in which capacitors are connected, and high-frequency waves act on the circuit to absorb it. There are foams and the like in which carbon black particles and the like are mixed. The magnetic loss is an action in which absorption occurs when the state of magnetization is changed by a magnetic field, and an electromagnetic wave absorbing material utilizing this action includes a sheet body in which ferrite is kneaded into rubber.

When these electromagnetic wave absorbing materials are classified by another method, the far field material used at a place where the electromagnetic wave arrives as a plane wave away from the electromagnetic wave generation source and the near field material used near the electromagnetic wave generation source. It is divided into For the former, a conductive electromagnetic wave reflector is placed on the back surface of the electromagnetic wave absorbing material, and design is performed by using the cancellation of the reflection from the electromagnetic wave absorbing material and the reflection on the surface of the electromagnetic wave absorbing material. Known theory (Osamu Hashimoto "Electromagnetic wave absorption material"
, Etc.) and determine the composition of the dielectric or magnetic material,
Create by controlling the thickness. However, this theory cannot be applied to the inside of electronic devices such as mobile phones and high-performance personal computers, or to near-field materials that may be used as cable coating materials for high-speed communication, and a clear design principle has been established. I haven't.

Under these circumstances, it is known that materials for near-field use, such as those obtained by mainly kneading a magnetic material into a resin and molding or sheeting, have a certain effect. It is used by pasting it on the substrate (industrial materials, October 1998, P54, etc.). However, since such a material is a resin molded body and contains a magnetic material at a high rate, it is difficult to bend and is heavy. Therefore, there has been a demand for an electromagnetic wave absorbing material that is improved in terms of workability, workability, and weight reduction of equipment. Further, such a material has an electromagnetic wave absorption effect of at most 20 dB (decibel) and is less effective in a microwave region of 1 GHz or higher, and a material having a greater effect has been demanded. In addition, with the diversification of usage of electromagnetic wave absorbing materials, there has been a demand for air-permeable materials used for gaskets and ventilation holes and sound-absorbing / vibrating materials used for transportation such as automobiles.

On the other hand, there is an example (Japanese Patent Laid-Open No. 60-50902) in which the magnetic powder is applied to the surface of the fiber structure together with the resin, but there is a problem that the air permeability and the flexibility are lowered. Further, an example in which dielectric powder is combined with a fiber structure (Japanese Patent Laid-Open No. 8-1
81482), but it was difficult to obtain electromagnetic wave absorption in a wide frequency range by using a dielectric.

[0007]

In view of the above situation, the present invention is flexible and lightweight and highly effective, and further has breathability and sound absorption.
It is intended to provide a radio wave absorbing fiber structure composite which also has a vibration damping property. In particular, the present invention aims to provide a radio wave absorbing material for the near field.

[0008]

The present invention employs the following means in order to solve the above problems. That is, the electromagnetic wave absorbing fiber structure composite of the present invention contains magnetic fine particles in an amount of 30 to 500% by weight based on the weight of the fiber.
It is characterized by containing. The fiber structure composite of the present invention is preferably provided with an electromagnetic wave reflection layer and / or a protective layer on the surface.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The magnetic fine particles of the present invention include:
It is possible to use all particles made of a material that causes a loss by interacting with the magnetic field component of the electromagnetic wave. Examples include soft ferrite, M-type hexagonal ferrite, soft magnetic metal, amorphous metal, and carbonyl iron.

An example of soft ferrite is Ni-Z
n type ferrite, Mn-Zn type ferrite, Mn-Mg
-Zn type ferrite etc. can be mentioned. Examples of the soft magnetic metal are pure iron, Fe-Si alloy, Fe-Co alloy, Fe-Ni alloy, Fe-Al alloy, Fe-Cr alloy, Fe-Si-Al alloy, Fe-Cr-Si alloy, F.
Examples include materials selected from e-Cr-Al alloys. Further, in the texture system of BaFe ₁₂ O ₁₉ which is a magnet ferrite, M-type hexagonal ferrite in which iron is replaced by titanium, manganese or the like can also be suitably used.
Examples of the amorphous metal include the above soft magnetic alloys and other metals having an amorphous structure,
A desired elemental composition and shape may be obtained by using a technique which has been actively researched recently such as liquid rapid cooling and sputtering.

In the present invention, by selecting appropriate magnetic fine particles, it is possible to design the material according to the frequency band. In particular, in order to obtain a high effect in a high frequency band of 1 GHz or more, it is desirable to use soft magnetic metal, amorphous metal, carbonyl iron, or the like.

The average particle size of the magnetic fine particles used in the present invention is preferably 0.1 to 300 μm. If it is smaller than 0.1 μm, it becomes difficult to hold it in the inter-fiber voids in the nonwoven fabric, and if it is larger than 300 μm, it becomes difficult to enter the inter-fiber voids in the nonwoven fabric.
In the present invention, more preferable average particle diameter of fine particles is 1 to 20 μm.
Is. The reason why the average particle size is preferably 20 μm or less is that the smaller the particle size is, the smaller the voids between particles are and the larger the content of fine particles in the fibrous structure composite is. It is easy to increase flexibility. The reason why the average particle size is preferably 1 μm or more is that if the particle size is smaller than this, the particles are likely to be scattered by the air flow, and the handling during manufacturing becomes difficult.

The fine magnetic particles used in the present invention may be subjected to shape changes such as flattening, linearization, acicularization, and compounding in order to enhance the electromagnetic wave absorption effect. For example, in the present invention, flattened soft magnetic metal or amorphous fine particles can be preferably used.

As the fine particles of the present invention, magnetic fine particles are highly effective and desirable. However, it is more desirable to use the dielectric particles in combination with the magnetic particles because the effect can be enhanced synergistically. As the dielectric fine particles, it is possible to use all particles made of a material that causes a loss by interacting with an electric field component of electromagnetic waves. Typical examples are carbon-based materials such as carbon black and graphite, but other materials such as metal powder can also be used.

The fiber structure of the present invention includes natural fibers,
A filament, a spun yarn, a woven fabric, a knitted fabric, a non-woven fabric, or the like made of at least one of regenerated fiber, semi-synthetic fiber, and synthetic fiber can be used. Natural fibers such as cotton, animal hair fibers, silk and hemp, regenerated fibers such as cellulosic regenerated fibers rayon (viscose rayon) and cupra (copper ammonia rayon), etc., semi-synthetic fibers such as cellulosic semi-synthetic fibers Acetate (triacetate) and the like, and synthetic fibers include organic fibers and inorganic fibers, and as the organic fibers, various fibers such as polyester, nylon, acrylic, and aramid can be cited. Examples of the inorganic fibers include metal fibers, glass fibers, ceramic fibers, carbon fibers, composite inorganic fibers and the like. Further, the fiber structure of the present invention also includes those in which various organic substances or inorganic substances are provided on the surface or inside of the above fibers.

When synthetic fibers are used as the fiber structure of the present invention, examples of the polymer constituting the synthetic fibers include polyester type polymers, polyamide type polymers and polyolefin type polymers. Here, the polyester-based polymer includes a polyester having an aromatic polyester such as polyethylene terephthalate, polypropylene terephthalate, and polybutylene terephthalate, or an aliphatic polyester such as polylactic acid and polycaprolactone as a basic constituent unit. Among them, those having polyethylene terephthalate as a basic constituent unit are preferable in terms of strength and durability. Further, in the present invention, a polymer made of a copolymer obtained by copolymerizing the above polyester with some other component, or a fiber made of a mixture obtained by blending a small amount of another organic polymer compound therein is also included therein. As the polyamide-based polymer, nylon, aromatic polyamide,
Examples of the polyolefin-based polymer include polyethylene, polypropylene, polystyrene and the like. In addition, synthetic fibers composed of polyphenylene sulfide or a fluorine-based polymer can also be suitably used as other synthetic polymers.

As the material constituting the fibers in the fiber structure of the present invention, it is preferable to use a material having flame retardancy. This is because the electromagnetic wave absorbing fiber structure composite of the present invention is often used in the vicinity of electronic devices, and flame retardancy is required to prevent danger. Specific examples of the flame-retardant material include polyphenylene sulfide, a fluorine-based polymer, a phenol resin-based polymer, and an aromatic liquid crystal polyester as the organic polymer. Naturally, inorganic materials have high flame retardancy, and thus the materials forming the above-mentioned inorganic fibers can also be suitably used. Similarly, in order to impart flame retardancy to the fiber structure of the present invention, the fiber structure may contain a flame retardant.

The average value of the fiber diameters constituting the fiber structure of the present invention is preferably 0.1 to 1000 μm, particularly 1 to 50.
μm is preferred. A fiber structure having a fiber diameter within this range is suitable for holding the fine particles of the present invention. The basis weight of the nonwoven fabric is preferably ²⁰ to 1000 g / m ² and the thickness is preferably 0.1 to 20 mm. The reason for this is that if the basis weight or thickness is smaller than this, the strength is insufficient, and if it is larger than this, it is difficult to handle depending on the application. The apparent density of the fiber structure is preferably 0.01 to 0.30 g / cm ³ . The reason for this is that if the apparent density is smaller than this, strength and durability are insufficient, and if it is larger than this, there are few voids that can hold the fine particles of the present invention.

In the present invention, since a large amount of fine particles are contained in the fiber structure, it is desirable that the fiber structure is a non-woven fabric having a large amount of uniform voids inside as compared with a woven or knitted fabric. The non-woven fabric of the present invention can be selected and used from short fiber non-woven fabrics or long fiber non-woven fabrics produced by various methods such as dry, wet, spunlace, spunbond, and melt blow, as required. The non-woven fabric is preferably formed of a melt-spinnable synthetic polymer such as a polyester polymer, a polyamide polymer, or a polyolefin polymer. The reason for this is that a nonwoven fabric using such a synthetic polymer can easily be obtained as an inexpensive product in which the fineness, the amount of inter-fiber voids, the shape, etc. are controlled.

As the non-woven fabric, it is particularly preferable to use a non-woven fabric containing both a layer containing fibers having a fiber diameter of 10 to 50 μm and a layer containing fibers having a fiber diameter of 0.1 to 3 μm. The reason for this is that when such a laminated nonwoven fabric is used, the fine particles of the present invention cannot be selectively trapped in one layer and migrate to the other side, and it is easy to retain the fine particles inside the nonwoven fabric for a long period of time. . Examples of the non-woven fabric containing the above two layers include those obtained by laminating a spun bond non-woven fabric and a melt blown non-woven fabric.

The present invention is characterized in that the fine particles are contained in an amount of 30 to 500% by weight based on the weight of the fiber of the fiber structure. In the present invention, by combining the fine particles having electromagnetic wave absorbing property with the fiber structure in this manner, a flexible and lightweight electromagnetic wave absorbing material which has never been available has been made possible. The reason why it is preferable to contain the fine particles in an amount of 30% by weight or more based on the weight of the fiber is to increase the ratio of the electromagnetic wave absorbing component per the weight of the fiber to obtain a high electromagnetic wave absorbing effect. The reason why the content of the fine particles is preferably 500% by weight or less is that the appearance and handleability of the fiber structure are deteriorated when the content is larger than this. More preferably, the content of the fine particles is 80 to 200.
It is desirable that the content is wt%. The reason why the content ratio is preferably 80% or more is that such a large amount of radio wave absorbing component allows a high electromagnetic wave absorbing effect to be obtained even with a thin fiber structure composite. The reason why the content of the fine particles is preferably 200% by weight or less is that the production process of the fiber structure composite becomes difficult if the content is more than this range.

The present invention is characterized in that the fine particles are contained in inter-fiber voids inside the fiber structure. In the method of mixing fine particles with a polymer to form a fiber, it is difficult to obtain a high content of fine particles because the physical properties of the fiber are deteriorated. However, in the present invention, a nonwoven fabric is particularly used and 80 to 9 are contained inside the fiber structure.
By utilizing the inter-fiber voids that exist in a proportion of 0% or more, it was possible to compound a large amount of fine particles into the fiber structure as never before.

The fiber structure composite of the present invention preferably has an air permeability of 0.1 to 800 ml / cm ² / sec. This is because if the air flow rate is smaller than this, it will be difficult to obtain practicality because the air will not circulate inside when used for ventilation holes of electronic devices. If the air flow rate is higher than this, it will be difficult to handle for some applications. . In the present invention, the air permeability of the fiber structure composite is 10 to 100 ml / cm ² / se.
It is more preferably c. The reason for this is that if the air flow rate is less than this amount, the flow of air into the fiber structure composite tends to be insufficient when a large amount of water treatment is required. This is because strength and durability are insufficient when loosened. In the present invention, it is also preferable to use a non-woven fabric because the air permeability and the particle content can be more easily balanced.

In the present invention, it is desirable to provide an electromagnetic wave reflection layer and / or a protective layer on the surface of the fiber structure composite. The electromagnetic wave reflection layer is a layer having high conductivity and preventing electromagnetic waves from entering inside, and examples thereof include a metal foil and a conductive fiber cloth. The reason why it is desirable to provide the electromagnetic wave reflection layer is that this suppresses the propagation of the electromagnetic wave to the side opposite to the reflection, thereby obtaining the effect of suppressing the radiation of the electromagnetic wave from the electronic device. The protective layer is a layer that covers the surface of the electromagnetic wave absorption layer and protects it from contact with other objects, friction, harmful gas, etc., resin layer, porous film, paper, fiber sheet, breathable net, and other various fiber structures. You can list things. For the purpose of the present invention, it is desirable that these electromagnetic wave reflection layers and protective layers have air permeability. Similarly, an adhesive layer or a pressure-sensitive adhesive layer may be provided. The reason why it is desirable to provide a protective layer is to prevent the fine particles from falling out of the fiber structure composite of the present invention, to avoid adverse effects on the device, and to improve durability during long-term use. . The electromagnetic wave reflection layer may be provided on only one surface, and in that case, the protection layer is preferably provided on the opposite surface. By thus forming a product in which the electromagnetic wave reflection layer and the protective layer are integrated, the fiber structure composite of the present invention has good workability and is easy to use as an electronic device or a cable covering material.

Further, the fiber structure composite of the present invention preferably contains conductive fibers. The conductive fiber means a fiber having a resistance value of about 1 Ω · cm or less, for example, a metal fiber,
Examples thereof include carbon fibers and metal-plated polymer fibers. If such a fiber is contained in the electromagnetic wave reflecting layer, for example, an electromagnetic wave absorbing fiber structure composite body which is flexible, lightweight and has good air permeability can be obtained. Further, such a fiber may be contained in the fiber structure layer containing fine particles,
The electromagnetic wave absorption effect can be further improved by appropriately selecting the type and blending amount.

Among them, in the present invention, it is desirable to use carbon fiber as the conductive fiber. The reason for this is that the carbon fiber is lighter than the metal fiber, the resistance value can be controlled by the manufacturing method, and the dielectric loss is large.
For example, by including carbon fibers in the electromagnetic wave reflection layer, a lighter electromagnetic wave absorption fiber structure composite can be obtained,
If it is contained in the fiber structure layer containing fine particles, the dielectric loss can further improve the electromagnetic wave absorption effect.

In the present invention, as long as the characteristics of the fiber structure composite of the present invention can be obtained, there is no particular limitation on the method of applying fine particles to the fiber structure. Examples include a method in which an aqueous dispersion of fine particles is applied by dipping or spraying and drying, a method in which fine particles are sprayed and held on a fiber structure by an air flow, and a state in which fine particles and short fibers are mixed is air flow in a net. Examples thereof include a method of spraying to make a nonwoven fabric, a method of incorporating fine particles in the process of forming the nonwoven fabric by entanglement of short fibers by hydroentanglement, a method of incorporating fine particles into the air flow of a meltblown nonwoven fabric and incorporating them into the nonwoven fabric. If necessary, the above methods may be repeatedly used or combined.

In the fibrous structure composite of the present invention, since the fine particles are fixed to the fiber, it is possible to include a heat-sealing fiber in the fibrous structure or to apply an adhesive together with the fine particles to the fibrous structure. Is. The types and blending amounts of the heat-sealing fibers and the adhesive may be selected according to the application and required characteristics.

In the present invention, by including a large amount of the radio wave absorbing fine particles in the fiber structure as described above, it becomes possible to provide a component such as a gasket used especially inside the electronic equipment and around the ventilation hole, and a communication cable coating material. It was Specific examples of electronic device parts applications include gaskets for personal computers, sheets to be attached to substrates, and parts to be placed inside mobile phones. As a concrete example of the communication cable covering material,
Examples include coating materials for various cables for high-speed LAN, image transfer, high-frequency measuring equipment, and the like.

[0030]

EXAMPLES The present invention will be described in more detail below with reference to examples.

The measurements in Examples and Comparative Examples were carried out by the following methods. <Average particle size> The average particle size was measured according to the usual method by the Coulter counter method. <Return loss and peak frequency> 500MHz, 3GH
The amount of attenuation of the reflected wave with respect to the incident wave at z and 9 GHz was measured using a network analyzer, and the amount of attenuation (dB) at each frequency was obtained. [Example 1] Mn-Zn ferrite fine particles (average particle size 3.2 µm) were used, and a 20% by weight aqueous dispersion of these particles was squeezed with a polyester spunbond nonwoven fabric having a basis weight of 240 g / m ² and a thickness of 1.5 mm. Dipping at 95%, 130
The operation of drying at 0 ° C. was repeated twice to obtain a fiber structure composite in which 37% of the porous silica fine particles were added to the fiber weight.

The characteristics of the obtained composite are shown in Table 1. From this, according to the present invention, a flexible and lightweight fiber structure composite having high electromagnetic wave absorption was obtained. [Example 2] A ferrite spunbonded nonwoven fabric having a basis weight of 60 g / m ² and a thickness of 0.3 mm was mixed with the ferrite fine particles of Example 1 and a heat-sealable core-sheath polyester staple fiber having a low melting point polyester as a sheath. Then, they were spray-laminated by an air stream and hot-pressed. The mixing ratio of the fine particles to the heat-fusible short fibers was 1 to 2 parts by weight of fine particles. As a result, a nonwoven fabric composite in which 145% of ferrite fine particles were added to the fiber weight was obtained.

The characteristics of the obtained composite are shown in Table 1. From this, according to the present invention, a flexible and lightweight fiber structure composite having high electromagnetic wave absorption was obtained. [Example 3] Spunbonded nonwoven fabric (average fiber diameter 20μ
m), a melt-blown nonwoven fabric (average fiber thickness: ² μm) was laminated on the polypropylene nonwoven fabric having a basis weight of 80 g / m ² and a thickness of 0.5 mm, and the magnetic fine particles of Example 1 were flown from the spunbonded nonwoven fabric side. It was sprayed and compounded. As a result, a non-woven fabric composite was obtained in which 156% of the porous silica fine particles were added to the fiber weight.

The characteristics of the obtained composite are shown in Table 1. From this, according to the present invention, a flexible and lightweight fiber structure composite having high electromagnetic wave absorption was obtained. [Examples 4 to 6] A nickel-plated conductive cloth (thickness 0.8 mm, surface resistance 0.8 Ω / □) was used as an electromagnetic wave reflection layer on one surface of each of the fiber structure composites of Examples 1 to 3 using an acrylic adhesive. And bonded all over.

The properties of the obtained fiber structure composite are shown in Table 1. From this, according to the present invention, a flexible and lightweight fiber structure composite having high electromagnetic wave absorption was obtained. Example 7 A polyester spunbonded nonwoven fabric having a basis weight of 60 g / m ² and a thickness of 0.3 mm was used, and the ferrite fine particles of Example 1 and the low-melting point polyester were used as sheaths for heat-sealing core-sheath polyester short fibers, and further dielectrics. Carbon black was mixed as body particles, sprayed and laminated by an air stream, and hot pressed. The mixing ratio of each component was such that the weight of fine particles was 2 and the weight of short fibers was 1 and carbon black was 0.2. As a result, the ferrite fine particles are 124
%, And a carbon fiber composite containing 11% of carbon black was obtained.

The characteristics of the obtained fiber structure composite are shown in Table 1. From this, according to the present invention, a flexible and lightweight fiber structure composite having higher electromagnetic wave absorption was obtained. [Example 8] The same operation as in Example 7 was carried out by using nickel-plated acrylic fibers made into short fibers instead of the carbon black particles. Thus, a fiber structure composite containing 124% of ferrite fine particles and 12% of nickel-plated acrylic fiber based on the weight of polyester fiber was obtained.

The characteristics of the obtained fiber structure composite are shown in Table 1. From this, according to the present invention, a flexible and lightweight fiber structure composite having higher electromagnetic wave absorption was obtained. [Example 9] The same operation as in Example 7 was carried out by using short carbon fibers instead of the carbon black particles.
Thus, a fiber structure composite containing 122% of ferrite fine particles and 10% of carbon fibers based on the weight of polyester fibers was obtained.

The characteristics of the obtained fiber structure composite are shown in Table 1. From this, according to the present invention, a flexible and lightweight fiber structure composite having higher electromagnetic wave absorption was obtained. Comparative Example 1 The procedure of Example 1 was repeated, except that the operation of dipping and drying the polyester spunbonded nonwoven fabric was performed only once. As a result, the amount of the ferrite fine particles applied was 14%, and as shown in Table 1, a high electromagnetic wave absorbing effect was not obtained.

[0039]

[Table 1]

[0040]

EFFECT OF THE INVENTION The electromagnetic wave absorbing fiber structure composite of the present invention makes it possible to easily and easily take measures against noise in electronic devices and communication cables operating at high frequencies. Especially when it is used as a gasket for a ventilation hole of an electronic device, a high effect of preventing electromagnetic wave leakage can be obtained while maintaining high air permeability. Further, when used as a high-speed communication cable covering material, it can be easily wound even on a thin cable, and a high electromagnetic wave leakage prevention effect can be obtained. Further, since the electromagnetic wave absorbing material of the present invention is a fiber structure, it has an action of absorbing vibration energy inside,
It also has sound absorption and damping properties.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 4L031 AA27 BA05 BA20 DA00 DA15                 5E321 AA03 AA21 BB21 BB25 BB31                       BB51 CC16 GG05 GG09 GG11                       GH05

Claims (6)

[Claims] 1. Magnetic fine particles in an amount of 30 to 50 relative to the weight of fiber.
An electromagnetic wave absorbing fiber structure composite characterized by containing 0% by weight. 2. The content of the fine particles with respect to the fiber weight is 80.
% To 200% by weight, the electromagnetic wave absorbing fiber structure composite according to claim 1. 3. The electromagnetic wave absorbing fiber structure composite according to claim 1, wherein an electromagnetic wave reflecting layer and / or a protective layer is provided on the surface of the fiber structure composite. 4. The electromagnetic wave absorbing fiber structure composite according to claim 1, wherein the fiber structure composite contains conductive fibers. 5. The electromagnetic wave absorbing fiber structure composite according to claim 4, wherein the conductive fiber is a carbon fiber. 6. A ventilation rate of 0.1 to 800 ml / cm ² / s.
It is ec, The electromagnetic wave absorptive fiber structure composite body in any one of Claims 1-5 characterized by the above-mentioned.