JP3022844B2 - Resistance film for radio wave absorption wall, method of manufacturing the same, and radio wave absorption wall using the resistance film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resistance film used for a radio wave absorbing wall , a method of manufacturing the same, and a radio wave absorber using the resistance film. More specifically, the present invention relates to a radio wave absorption structure wall useful as an outer wall material of a building.

[0002]

2. Description of the Related Art In recent years, radio interference caused by buildings such as buildings has become a major social problem. In order to solve this radio wave interference, a λ / 4 type radio wave absorption wall combining a radio wave reflector and a resistive film has been proposed (Japanese Patent Laid-Open No. Hei 8-3).
26193). This proposal proposes a resistive film having a predetermined resistance value at a position separated by λ / 4 (λ is the wavelength of an incident radio wave) from a front surface in the incident direction of the reflective layer in a structure including a radio wave reflective layer and a resistive film. Is based on the finding that a radio wave absorption wall having excellent radio wave absorption characteristics can be obtained by arranging.

Further, a radio wave absorber based on the same concept has been proposed (see Japanese Patent Application Laid-Open No. 9-260886).
This is because a plurality of long carbon fiber bundles formed by arranging a large number of carbon long fibers exhibiting a volume specific electric resistance of 10 ⁻⁴ to 10 ⁴ Ω · cm in the length direction and bonding them with a binder are used. This is a radio wave absorber having a resistive film layer arranged in parallel with an opening, a dielectric layer behind the resistive layer, and a reflective layer behind the dielectric layer.

In addition, when carbon fiber (CF) paper is used as the resistance film, its electrical basic properties and the λ / 4 type radio wave absorption wall using the carbon fiber paper as the resistance film are used. Experimental study on TV radio wave absorption capacity in the case has been reported (Otani et al .: Abstracts of Architectural Institute of Japan, June 1996, p1339-13)
40 "Development of TV Wave Absorbing Wall Using Carbon Fiber Resistive Film (Part 1 Electrical Characteristics and Radio Wave Absorbing Ability of CF Resistive Film)"). Here, the DC area resistance is 47 μm with a thickness of 350 μm.
A resistance film in which two 3 Ω / square CF papermaking papers are bonded together, and a resistance film in which a rectangular hole is formed in the resistance film to form a mesh structure, and a resistance value is adjusted by changing a porosity are used.

[0005]

However, carbon fiber papermaking has low strength. Therefore, in the case where a radio wave absorbing wall having a practical area is manufactured by being embedded in concrete or the like, for example, handling is not easy. This is particularly remarkable in a mesh-shaped resistive film having openings. The present invention has been made to solve the above-mentioned conventional problems, and is lightweight and has high strength, so that it is easy to handle at the time of manufacturing a resonance type radio wave absorption wall , and has excellent workability and a resistance film. It is intended to provide a manufacturing method. A further object of the present invention is to provide a radio wave absorbing wall using the resistive film and having excellent radio wave absorbing characteristics.

[0006]

SUMMARY OF THE INVENTION The object and advantages of the present invention are that a short carbon fiber having a fiber length of 0.1 to 150 mm is formed.
Has been one or both surfaces of the carbon fiber paper is coated with a resin, is achieved by the resistive film for radio wave absorption wall and a plurality of openings are formed. By coating the carbon fiber paper with the resin, the strength of the resistive film can be improved without increasing the weight of the resistive film. Therefore, in manufacturing a radio wave absorption wall having a structure in which the resistive film is embedded, the resistive film has excellent workability. Further, the resistance value of the resistance film can be adjusted by the resin to be coated. In addition, since the resistance film of the present invention is covered with a resin, there is also an advantage that the resistance film can be provided with a moisture-proof and waterproof function .

A plurality of openings are formed in the resistive film of the present invention.
You. The opening allows the resistance value of the resistive film to be adjusted. When buried in a dielectric such as concrete,
Since the resistance film has the opening, the structure such as concrete sandwiching both sides of the resistance film can be integrated through the opening. Therefore, the strength of the dielectric is not significantly impaired. Further, the operation of bonding the resistive film and the structure such as concrete with an adhesive or the like becomes unnecessary. The shape of the aperture can be any shape such as a rectangle, a triangle, other polygons, a circle, and an ellipse. However, a rectangular shape is preferable in terms of manufacturing and radio wave absorption characteristics. In addition, it is preferable that the plurality of openings of the resistive film have the same shape and are regularly arranged at regular intervals, from the viewpoint of adjusting the resistance value.
Furthermore, the resistance film of the present invention has a thickness of 0.2 to 0.4.
mm. Excellent strength and handling
It will be. In particular, in terms of the strength and rigidity of the resistive film,
Preferably, the resin is polyethylene terephthalate.
New

In the case where a wall of a resonance type radio wave absorption structure is formed by using a plurality of openings having the same shape and a resistive film regularly arranged at regular intervals, the openings are regularly formed. It is preferable that the direction in which the antenna is arranged and the direction of the electric field of the radio wave to be absorbed be parallel. Thereby, the radio wave absorption characteristics can be improved. The resistance film for a radio wave absorbing wall of the present invention has a fiber length of 0.1 to 150 mm.
A step of the short carbon fibers and papermaking obtain a carbon fiber paper with the, the step of coating a resin on both sides or one side of the carbon fiber paper, to form a plurality of opening portions in the carbon fiber paper
Manufacturing process .

The resistive film of the present invention can be used as a radio wave absorbing wall by combining a radio wave reflecting layer. For example, the radio wave absorption structure wall of the present invention includes a resistive film in which both or one surface of carbon fiber paper is coated with a resin, a conductive radio wave reflection layer, and a dielectric. In addition, between the resistance film and the radio wave reflection layer
In addition, concrete, which is a dielectric, may be present.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The radio wave absorbing wall resistance film of the present invention is formed by coating both sides or one side of a carbon fiber paper with a resin and forming the sheet into a sheet. The shape of the sheet includes those having substantially the same size in the vertical and horizontal directions, and also includes those in the form of a tape whose dimension in one direction is extremely larger than that in the other direction. The carbon fiber paper which is a component of the resistive film of the present invention can be manufactured by, for example, making short carbon fibers. Papermaking can be carried out by using a mixture of carbon fibers and a binder for papermaking as a raw material and using an ordinary papermaking machine comprising a netting unit using a circular net, a pressing unit, a drying unit, and the like. As the carbon fiber, for example, a fiber made of pitch, polyacrylonitrile, rayon, or the like is used. Of these, short carbon fibers made from pitch are preferred. Examples of the raw material pitch include coal-based coal tar, coal tar pitch, coal liquefaction, petroleum heavy oil, pitch, petroleum resin and its thermal polycondensation reaction product, and products produced by the catalytic reaction of naphthalene and anthracene. And the like.

As the carbon fibers used in the present invention, short carbon fibers having a fiber length of about 0.1 to 150 mm are preferably used. Carbon fibers have a volume resistance of 10 ^-3 to 10 ^-4.
Ω · cm and a fiber diameter of 5 to 30 μm are preferably used. As the carbon fiber, one kind or a mixture of two or more kinds of carbon fibers having different characteristics can be used. As the papermaking binder, organic fibers such as cellulose fiber, polypropylene fiber, polyvinyl alcohol fiber, and papermaking pulp are suitable, and a mixture of one or more binders can be used.

The resistance value of the carbon fiber paper is defined as the value of the volume resistivity of the carbon fiber, the length of the carbon fiber, the mixing ratio of the carbon fiber and the papermaking binder, and the basis weight (weight per unit area) of the carbon fiber paper. It can be adjusted to a desired value by appropriately combining the above. The resistance film of the present invention,
The carbon fiber paper manufactured as described above is manufactured by coating both sides or one side with a resin. It is preferable that both sides of the carbon fiber paper be coated in terms of handling properties and resistance value adjustment.

As the resin, thermosetting resin such as phenol resin, epoxy resin, polyester resin, polyethylene terephthalate resin (PET), polybutylene terephthalate resin (PBT), polycarbonate resin (P
C), thermoplastic resins such as polyethylene resin, polypropylene resin and polyvinyl chloride resin, and rubber-like substances such as natural rubber and synthetic rubber. Among them, the use of polyethylene terephthalate resin (PET) is preferable in terms of ease of lamination, strength and rigidity of the resistive film, and the like.

Various methods can be employed for coating both sides or one side of the carbon fiber paper with the resin. For example, when coating both sides of carbon fiber paper with resin,
There is a method of impregnating a carbon fiber paper with a thermosetting resin and curing the same. At this time, if a thermosetting resin diluted with a solvent is used, the impregnation of the carbon fiber paper can be facilitated. When a resin diluted with a solvent is used, it is preferable to dry and remove the solvent before curing the resin. Examples of the solvent include ethyl alcohol and the like.

Alternatively, both surfaces of the carbon fiber paper can be coated with the resin by impregnating the carbon fiber paper with a solution obtained by dissolving a thermoplastic resin in a solvent and then removing the solvent by drying. Alternatively, both sides or one side of the carbon fiber paper can be coated with a resin by a method of laminating a sheet or film made of a thermoplastic resin on both sides or one side of the carbon fiber paper. Lamination can be performed by pressing with a heating press or a heating roller.

The resistance film of the present invention can be easily controlled to have a desired resistance value by adjusting the resistance value of carbon fiber paper as a constituent element. The resistance value of the carbon fiber paper changes depending on the cross-sectional area of the carbon fiber paper. In addition, the resistance value of the entire resistive film can be further adjusted by forming an opening in the carbon fiber paper coated on both sides or one side with the resin manufactured as described above.

In the case where the openings are formed to adjust the resistance value of the resistive film, the plurality of openings have the same shape and are regularly arranged at regular intervals. Is preferred. When a plurality of apertures are of the same shape and a resonance type radio wave absorption structure wall is formed by using a resistive film that is regularly arranged at regular intervals, the apertures are regularly arranged. It is preferable that the direction of the electric field of the radio wave to be absorbed be parallel to the direction of the electric wave to be absorbed. With such a structure, the radio wave absorption characteristics can be improved.

As a method of forming the opening, there is a method of cutting and removing a part of carbon fiber paper coated on both sides or one side with a resin. Alternatively, the resistive film of the present invention having an opening can be formed by bonding or thermocompression bonding tape-like carbon fiber paper coated on both sides or one side with a resin in a grid pattern. In addition, it can also be obtained by coating both sides or one side of a carbon fiber paper having an opening portion with a resin. However, it is preferable to open the holes after being covered with the resin, since the holes are easily formed in the carbon fiber paper. The total thickness of the resistive film including the resin layer, including the resin layer, is preferably 0.05 to 1.0 mm, and more preferably 0.2 to 0.4 mm from the viewpoint of strength and handling properties.

By using the resistive film of the present invention, a resonance type radio wave absorbing wall having excellent radio wave absorbing characteristics can be obtained. In addition, since the resistance film has high strength, high rigidity, and is lightweight, workability is good. Therefore, the radio wave absorbing wall can be easily manufactured. In order to manufacture a resonance type radio wave absorption wall using the resistive film of the present invention, the resistive film and the radio wave reflective layer are arranged so as to be kept at an appropriate interval. A configuration in which only vacuum or air exists between the resistive film and the radio wave reflection layer may be employed, or a configuration in which a dielectric such as concrete, plastic, stone, brick, wood, or the like exists. Even if the resistance film is buried in the dielectric,
It is less affected by the properties of the dielectric and can maintain stable radio wave absorption characteristics. Therefore, the use of the resistive film of the present invention makes it easy to design a radio wave absorbing wall .

The radio wave reflection layer is formed by a continuous sheet or film conductor such as a metal plate or a metal foil, a conductive mesh such as a wire net, a conductive rod or wire such as a metal in one or two directions. Can be constituted by layers arranged at intervals so as to constitute almost one plane. The radio wave reflection layer is not limited to these as long as it reflects a radio wave to be absorbed by the radio wave absorption wall . When the radio wave absorbing wall is made of reinforced concrete, the radio wave reflecting layer can be made of reinforcing steel.

It is preferable that the resistive film and the radio wave reflecting layer are arranged so as to be substantially parallel to each other with a certain space therebetween. When a tape-shaped resistive film is used, it is preferable to arrange the tape-shaped resistive films at a desired interval so that the length direction is parallel to the electric field direction of the radio wave to be absorbed. The distance L between the resistive film and the radio wave reflecting layer is as follows: When the wavelength of the radio wave to be absorbed is λ and the dielectric constant of the dielectric existing between the resistive film and the radio wave reflecting layer is ε, L = (λ / 4) (Ε) ^-1/2 is advantageous for enhancing the radio wave absorption characteristics,
It is determined in consideration of the radio wave absorption characteristics, the thickness of the radio wave absorption wall , and the like. The resistive film of the present invention is suitably used for manufacturing a resonance type radio wave absorption wall by being embedded in a concrete outer wall of a building or the like.

[0022]

The present invention will be described in more detail with reference to the following examples. Example 1 Papermaking was performed using a mixture of 25% by weight of pitch-based carbon fibers (average fiber length: 3 mm, average fiber diameter: 14.5 μm) having a maximum heat treatment temperature of 1000 ° C. and 75% by weight of cellulose fibers as a papermaking binder. Then, a long carbon fiber paper having a basis weight of 40 g / m ² , a thickness of 0.20 mm, and a width of 650 mm was produced. This carbon fiber paper was impregnated with a liquid resol type phenol resin (diluted with ethyl alcohol), dried and cured to obtain a phenol resin impregnated carbon fiber paper having a basis weight of 60 g / m ² . . Thereafter, phenol Ichiru resin impregnating both surfaces of the carbon fiber Bae one path one by stacking port triethylene terephthalate resin sheet heat pressing to a thickness of 0.3mm
Was produced. In this sheet-like molding,
Using a die-cut roll, a rectangular opening of 40 mm in length and 12 mm in width is formed in a regular manner as shown in FIG. 1 and a resistive film (resistive film A) having a porosity of 50% and a high-frequency resistance of about 300Ω
Was manufactured.

Using this resistive film, the following 2 of 2100 mm × 2100 mm × 150 mm having a structure as shown in FIG.
Types of radio wave absorption walls (wave absorption wall- 1 and radio wave absorption wall-
2) was manufactured. (Electromagnetic wave absorption wall- 1) A lightweight type having a reflective layer 4a in which a 6 mm thick metal rod 4 is buried in a mesh shape so that the vertical and horizontal intervals are 150 mm and 33 mm, respectively, at a position about 25 mm from the surface. A resistive film 1 (resistive film A) was bonded to the surface of the concrete 5 by using a 3 mm-thick epoxy mortar 2 and the surface thereof was covered with a surface blocking material 3 made of porcelain 13 mm thick large tiles. . The resistance film 1 was made to be almost at the center of the epoxy mortar 2. (Electromagnetic wave absorbing wall- 2) Resistive film 1 (resistive film A) on the surface of a lightweight type 1 concrete
And except joined with a liquid epoxy resin having a thickness of 1mm instead of the epoxy mortar 2 was wave absorbing wall -l similar wave absorber wall. (Results) In the production of the radio wave absorbing wall , the resistive film A had appropriate strength and rigidity, and was excellent in handleability and workability.

The radio wave absorbing wall- 1 and the radio wave absorbing wall- 2 for one week after the placing of the epoxy mortar and the lightweight type 1 concrete were subjected to a frequency of 400 MHz to 1.1 MHz. 1G
A radio wave in the range of Hz was incident from the resistive film side at a radio wave incident angle of 50 °, and the reflection loss was measured. The result is shown in FIG. Return loss, the radio wave absorption wall -l, about 25dB at a peak frequency 590 MHz, the wave absorber wall -2, about the peak frequency 540 MHz 24 dB
Met.

Both the radio wave absorption wall- 1 and the radio wave absorption wall- 2 exhibited good radio wave absorption characteristics. [Comparative Example 1] Papermaking using a mixture of 25% by weight of pitch-based carbon fibers (average fiber length: 3 mm, average fiber diameter: 14.5 μm) having a maximum heat treatment temperature of 1000 ° C. and 75% by weight of cellulose fibers as a binder for papermaking Then, a long carbon fiber パ ー par with a basis weight of 40 g / m ² , a thickness of 0.25 mm, and a width of 650 mm was produced. A part of this carbon fiber paper is cut out with a cutter, and rectangular openings of 10 mm in length and 40 mm in width are regularly formed as shown in FIG. 1, and a resistance film having an opening ratio of 60% and a high-frequency resistance of about 540Ω is used. A resistive film B) was produced.

The following two types of radio wave absorbing wall (electromagnetic wave absorbing walls -3, and radio wave absorbing wall 1300 mm × 1300 mm × 62 mm having a structure as shown in FIG. 2 by using the resistive film -
4) was manufactured. (Wave absorption wall -3) vertical metal rod 4 of thickness 3mm at a position of about 25mm from the surface, the lateral spacing is 60mm respectively, bi-Nilon fiber reinforced concrete having a reflective layer that is embedded in a mesh form so as to 20mm On the surface of No. 5, a resistive film 1 (resistive film B) was bonded using a 5 mm thick epoxy mortar 2 and the surface was covered with a surface finishing material 3 made of a 7 mm thick tile made of porcelain. The resistance film 1 was made to be almost at the center of the epoxy mortar 2. The (radio wave absorbing wall -4) bicycloalkyl Nilon fiber reinforced concrete surfaces, except joined by resistance film 1 (resistance film B) a 1mm thick liquid epoxy resin was wave absorbing wall -l similar wave absorption wall . (Results) In the manufacture of the radio wave absorption wall, the resistive film B not covered with the resin has a low strength, so that careful attention must be paid so as not to damage the resistive film.

[0027] The epoxy mortar, and the radio wave absorption wall after casting of bi Nilon fiber reinforced concrete -3 and radio wave absorption wall -4 frequency 400MHz～l. 1 GHz
A radio wave in the range of 1 was incident from the resistive film side at a radio wave incident angle of 0 °, and the reflection loss was measured. FIG. 4 shows the results. The reflection loss indicates a peak frequency of 680 at the radio wave absorption wall- 3.
About 23 dB, the electromagnetic wave absorbing walls -4 in MHz,
It was about 9 dB at a peak frequency of 600 MHz.
The radio wave absorption wall- 3 exhibited good radio wave absorption characteristics, but the radio wave absorption wall- 4 had poor radio wave absorption characteristics. It is considered that this is because the epoxy resin having a small viscosity entered the voids of the carbon fibers and changed the electrical characteristics of the resistance film.

[0028]

As is clear from the comparison between Example 1 and Comparative Example 1, the resistance film of the present invention in which both surfaces of the carbon fiber paper are coated with the resin has an appropriate strength and rigidity despite its light weight. And has excellent handleability and workability when manufacturing a radio wave absorption wall . Further, since the resistive film is covered with the resin, the resistive film of the present invention hardly absorbs moisture and is less deteriorated. When the resistive film of the present invention is buried in a dielectric such as concrete or epoxy resin in a radio wave absorbing wall, stable electrical characteristics can be maintained without being affected by the properties of the dielectric. Therefore, the use of the resistive film of the present invention facilitates the design of the radio wave absorbing wall .

[Brief description of the drawings]

FIG. 1 is a partially enlarged view showing an example of an arrangement of openings in a resistive film having openings according to the present invention.

FIG. 2 is a perspective view showing a configuration of a radio wave absorbing wall manufactured in Example 1 and Comparative Example 1.

FIG. 3 is a graph showing a frequency and a reflection loss of an incident radio wave on the radio wave absorption wall manufactured in Example 1.

FIG. 4 is a graph showing the frequency and reflection loss of an incident radio wave on the radio wave absorption wall manufactured in Comparative Example 1.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Resistive film 2 Epoxy mortar or epoxy resin 3 Surface finishing material 4 Metal rod 5 Concrete

Continued on the front page (72) Inventor Yukihiro Shibuya 16 Nishimachi Ochiai, Iwaki City, Fukushima Prefecture Inside the Nishiki Plant of Kureha Chemical Industry Co., Ltd. (72) Inventor Yoshinori Kasashima 1-2-7 Moto-Akasaka, Minato-ku, Tokyo Kashima Construction Co., Ltd. (72) Inventor Hiroaki Nakagawa 2-9-1-1, Tobita-Ken, Chofu-shi, Tokyo Kashima Construction Co., Ltd. (72) Inventor Takahiro Kosugi 2-9-1-1, Tobita-shi, Chofu-shi, Tokyo Kashima Construction Co., Ltd. (72) Inventor Takuro Sato 1-3-8 Moto-Akasaka, Minato-ku, Tokyo Kashima Construction Co., Ltd. Tokyo Branch (56) References JP-A-63-184398 (JP, A) JP-A-9-283967 (JP, A) JP-A-8-236982 (JP, A) JP-A 63-184398 145340 (JP, A) JP-A-62-111500 (JP, A) JP-A-2-1533851 (JP, A) JP-A-10-107478 (JP A) Japanese Utility Model Hei 2 35493 (JP, U) Japanese Utility Model 62-34498 (JP, U) Japanese Utility Model 61-129842 (JP, U) Japanese Utility Model Utility Model 61-81198 (JP, U) Japanese Utility Model 3 -100423 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) H05K 9/00

Claims (7)

(57) [Claims] 1. A short carbon fiber having a fiber length of 0.1 to 150 mm.
Formed from the one or both surfaces of the carbon fiber paper is coated with a resin, the resistance film for radio wave absorption wall and a plurality of openings are formed. 2. A plurality of openings have the same shape, claim are regularly arranged and spaced a predetermined distance 1
The resistance film for the radio wave absorption wall as described. 3. The thickness is 0.2 to 0.4 mm.
3. The resistance film for a radio wave absorption wall according to 1 or 2. 4. The method according to claim 1, wherein the resin is polyethylene terephthalate.
The radio wave absorbing wall according to any one of claims 1 to 3,
Resistive film. Obtaining a carbon paper 5. Papermaking short carbon fibers having a fiber length 0.1～150Mm, a step of coating both sides or one side of the carbon paper with a resin, a plurality of apertures
The part that has a step of forming the carbon fiber paper
A method for manufacturing a resistive film for a radio wave absorbing wall , which is a feature of the present invention. 6. A radio wave absorbing wall comprising the resistive film according to claim 1 and a radio wave reflecting layer. 7. A concrete between the resistive film and the radio wave reflection layer.
7. The radio wave absorbing wall according to claim 6, wherein a heat shield is present.