JP2002151882A - Radio wave absorbing panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio wave absorbing panel, into which foreign substance such as water, dust or exhaust gas or the like is less likely to penetrate into, and which is lightweight and thin and has sufficient radio wave absorbing performance. SOLUTION: In the panel provided with a tabular radio wave absorbing body and a covering material, having a radio wave transmitting characteristics and covering a part intended to allow radio wave incidence, the material is provided so as to suppress penetration of foreign substances into the absorbing body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio wave absorbing panel in which a radio wave absorber is covered with a covering material.

[0002]

2. Description of the Related Art In recent years, with the remarkable spread of electronic information devices such as mobile phones and personal computers and the diversification of communication technologies,
The suppression of unnecessary radio waves has become an increasingly important problem in social life. In addition, the band of radio waves used is expanding, and the use of radio waves having extremely short wavelengths such as millimeter waves, which have been conventionally used only for special purposes, is expected to increase in the future. In particular, it is thought that this tendency will be remarkable due to the development of ITS (Intelligent Transport System), which is currently being planned.

[0003] In order to suppress unnecessary radio waves, for example, a pyramid-shaped one made of urethane foam containing carbon, a ferrite tile sintered type, a thin one made of rubber or paint containing ferrite powder or carbon powder, 2. Description of the Related Art Various radio wave absorbers such as a woven fabric or a nonwoven fabric using conductive fibers have been known.

In general, characteristics required of a radio wave absorber include excellent radio wave absorption capability and a wide absorbable frequency band. Further, from the viewpoint of practicality, it is required that the degree of freedom in selecting the shape and size is high, the workability is excellent, the cost is low, and the like. In addition, a radio wave absorber for outdoor installation may further have weather resistance. In recent years, lightweight and thin,
A radio wave absorber satisfying the above characteristics has been developed.

[0005]

However, when installed outdoors, especially in a radio wave absorber using a fiber assembly having conductivity, foreign substances such as water, dust, and exhaust gas discharged from a vehicle are affected by radio waves. There is a problem that it penetrates into the absorber and adversely affects the radio wave absorbing ability.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a radio wave absorbing panel which is hard to penetrate foreign matters such as water, dust and exhaust gas into a radio wave absorber, and is lightweight, thin and has a sufficient radio wave absorbing ability. Things.

[0007]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have completed the present invention. The present invention is as follows. (1) A radio wave absorption panel comprising a flat radio wave absorber and a covering material having radio wave permeability and covering at least a portion of the radio wave absorber intended to receive radio waves, wherein the covering material is a radio wave absorbing material. A radio wave absorption panel provided so as to suppress intrusion of foreign matter into the absorber. (2) The radio wave absorbing panel according to the above (1), wherein the covering material is a sheet-like body formed of an organic polymer material. (3) When the dielectric constant of the coating material is εr, the thickness is t, and the wavelength of the radio wave to be absorbed is λ, the value represented by (εr × t) / λ is 0.1 or less. The above (1)
The radio wave absorption panel described in. (4) The above-mentioned (1) to (3), further comprising a reinforcing plate-shaped body on the back surface side of the portion intended to receive radio waves.
The radio wave absorption panel according to any of the above. (5) A radio wave absorption panel comprising a flat radio wave absorber and a covering material having radio wave permeability and covering at least a portion of the radio wave absorber intended to receive radio waves, wherein the dielectric constant of the covering material is Is εr, the thickness is t, and the wavelength of the radio wave intended to be absorbed is λ, the value represented by (εr × t) / λ is 0.1.
An electromagnetic wave absorption panel, wherein the number is 1 or less. (6) The radio wave absorbing panel according to any one of the above (1) to (5), wherein the radio wave absorber is made of an aggregate of conductive fibers. (7) At a tollgate on a toll road provided with a transmitting / receiving antenna for transmitting / receiving information to / from a vehicle equipped with an on-board unit having an automatic toll collection function, the radio wave absorber faces the communication area of the transmitting / receiving antenna. The radio wave absorption panel according to any one of (1) to (6), which is provided and used as described above.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
FIG. 1 is a simplified perspective view showing a preferred example of a radio wave absorbing panel 1 of the present invention, and FIG. 2 is an exploded perspective view showing a simplified structure of the radio wave absorbing panel 1 of FIG. The radio wave absorption panel 1 of the present invention basically includes a flat radio wave absorber 2 and a coating material 3 that covers at least a portion of the radio wave absorber 2 intended to receive radio waves.

The radio wave absorber 2 is not particularly limited as long as it is a flat plate. The shape of the radio wave absorber 2 is not particularly limited, but is formed into a flat plate having a square cross section as shown in FIGS. Preferably. The radio wave absorber 2 according to the present invention preferably has weather resistance when it is intended for outdoor installation. The size of the radio wave absorber 2 is not particularly limited, either, and is appropriately selected according to the purpose. The radio wave absorber 2 is, for example, in the first width direction X
The length (first width) along the width (0.5m-2m), the length along the second width direction Y (second width) is 0.5m-4m, and the length along the thickness direction Z (thickness) Is 2 cm to 10 cm. The first width direction X refers to a direction substantially along one of the two sides perpendicular to each other in the rectangular cross section, and the second width direction Y is defined by the two sides. A direction roughly along one of the other sides. The first width direction X, the second width direction Y, and the thickness direction Z are directions along three axes that intersect perpendicularly.

The coating material 3 in the present invention is not particularly limited as long as it has radio wave permeability and can cover at least a portion of the radio wave absorber 2 where radio wave is intended to be incident. In this specification, the term "radio wave permeability" refers to a radio wave loss, that is, a radio wave transmission attenuation amount as small as possible. Preferably, the dielectric constant of the coating material 3 is εr, the thickness is t, and absorption is intended. When the wavelength of a radio wave to be transmitted is λ, (εr
× t) / λ means that the value is 0.1 or less. The coating material 3 is provided so as to suppress intrusion of foreign matter into the radio wave absorber 2 as described later. Further, in the radio wave absorption panel of the present invention, when the outdoor material is intended for outdoor installation, it is desirable that the covering material 3 has weather resistance.

In the radio wave absorbing panel 1 of the present invention, the covering material 3 can protect at least the portion of the radio wave absorber 2 intended to receive radio waves from the outside. Therefore, when the radio wave absorbing panel 1 is installed outdoors, unlike a conventional case where the surface is exposed and the radio wave absorber is installed, foreign substances such as water, dust, and exhaust gas discharged from the vehicle absorb the radio wave absorbing panel. It has an effect of suppressing intrusion into the body and suppressing deterioration of the radio wave absorbing ability. This effect is particularly remarkable when, for example, the radio wave absorber 2 is made of a fiber aggregate having conductivity as described later.

The coating material 3 in the present invention is preferably a sheet formed of an organic polymer as shown in FIGS. Examples of the organic polymer include acrylic resin, polyvinyl chloride resin, unsaturated polyester resin, polyethylene resin, polypropylene resin, polyvinylidene chloride, polycarbonate, and FRP (fiber reinforced plastic) reinforced with glass fibers. Can be

The sheet-like body in the present invention is shown in FIG.
And a casing-like form as shown in FIG. FIG. 3 is a simplified perspective view showing another preferred example of the radio wave absorbing panel 1 'of the present invention, and FIG. 4 is an exploded perspective view schematically showing the structure of the radio wave absorbing panel 1' of FIG. The covering material 3 ′ in the embodiment shown in FIGS. 3 and 4 is realized by a casing that is open on the one hand and that can cover the radio wave absorber 2 from the side intended to receive radio waves. In FIGS. 3 and 4, the covering material 3 ′ realized by such a casing covers the radio wave absorber 2 from the side where the radio wave is intended to be incident (one side in the thickness direction Z1). It shows an example of mounting in this manner.

The thickness t of the covering members 3, 3 'at least on the side of the radio wave absorber 2 where the radio wave is intended to be incident is 0.
About 5 mm to 2 mm is preferable. The thickness t can be increased as the dielectric constant εr of the organic polymer is smaller.

As the coating materials 3, 3 ', as described above,
When the dielectric constant is εr, the thickness is t, and the wavelength of the radio wave to be absorbed is λ, it is preferable that the value represented by (εr × t) / λ satisfies the condition of 0.1 or less. By providing the covering materials 3 and 3 'so as to cover the portions of the radio wave absorber 2 intended to receive radio waves, the radio wave absorption performance of the radio wave absorber 2 is also improved, as will be clarified in the examples described later. Thus, a radio wave absorbing panel having good oblique incidence characteristics can be realized. This effect is particularly remarkable when a radio wave absorber made of a fiber aggregate having conductivity as described later is used. By providing 3 ′, it is possible to suppress the entry of foreign matter into the radio wave absorber 2 and obtain a radio wave absorption panel with improved radio wave absorption.

When the radio wave absorption panel of the present invention is installed in an environment where entry of foreign matter into the radio wave absorber 2 does not matter much, the value represented by the above (εr × t) / λ is used. If the coating material satisfies the condition of 0.1 or less, the coating material does not have to have a function of suppressing intrusion of foreign matter into the radio wave absorber 2.

The radio wave absorbing panel of the present invention preferably comprises
A reinforcing plate is further provided on the back surface side of the portion intended to receive radio waves. The reinforcing plate is for further reinforcing the structure provided with the above-described radio wave absorber and the covering material, and is formed of, for example, an aluminum-plated steel plate or a zinc-plated steel plate. It is preferable to be formed of an aluminum-plated steel plate having the same. FIG. 1 and FIG. 2 show an example in which a flat reinforcing plate 4 is provided on the other Z2 side in the thickness direction of the radio wave absorber 2.

A light and thin radio wave absorber may be undesirably easily deformed such as being bent when it is realized with a relatively large size (for example, a size having an area exceeding 1 m ² ). . The bent radio wave absorber has poor workability at the time of installation and the like, and has a problem that it easily peels off when subjected to a wind pressure load. As described above, by further providing a reinforcing plate on the back side of the radio wave incident side, the radio wave absorber can be reinforced and undesired deformation of the radio wave absorber can be suppressed.

Further, as shown in FIGS. 3 and 4, the reinforcing plate-like body may be realized by a square wave plate having a cross section along any one of the width directions having regular irregularities. Good. In FIGS. 3 and 4, a reinforcing plate-shaped member 4 ′ is provided on the other Z2 side in the thickness direction of the radio wave absorber 2 so that the cross-sectional shape along the first width direction X has regular irregularities. An example is shown. When the rectangular wave plate is provided on the radio wave absorber 2 realized in a longitudinal direction, the rectangular wave plate is arranged so that the direction in which the cross section having the irregularities appears is substantially perpendicular to the longitudinal direction of the radio wave absorber 2. Is preferred. This makes it possible to reinforce the radio wave absorber along the longitudinal direction in which undesired deformation is likely to occur, and to increase the rigidity of the radio wave absorption panel in the above direction.

The radio wave absorbing panel of the present invention more preferably has a reinforcing frame member between the radio wave absorber and the reinforcing plate. As the reinforcing frame member, for example, longitudinal members realized by a hat-shaped steel plate are arranged in combination so as to be substantially perpendicular to each other. There is no particular limitation on the method of forming the reinforcing frame member. For example, an appropriate number of reinforcing frame members having a second width similar to that of the reinforcing plate-shaped member placed along the second width direction Y (see FIGS. 1 and 2) 3 and two in the example of FIGS. 3 and 4), a plurality of hat-shaped steel sheets (FIGS. 1 and 2) spaced at appropriate intervals along the first width direction X. 6 and four in the examples of FIGS. 3 and 4).

As described above, by further providing the reinforcing frame member, the radio wave absorber 2 is further reinforced in the first width direction X and the second width direction Y, and may be bent or twisted even at the time of mounting and installation. There is no undesired deformation. In the present invention, the formation of the frame member is not limited to the above-mentioned hat-type steel plate, and can be formed by using a conventionally known L-type angle steel plate, a U-shaped steel plate, or the like,
From the viewpoint of weight reduction, it is particularly preferable to use a hat-shaped steel plate.

The method of fixing between the members of the radio wave absorbing panel of the present invention, such as the radio wave absorber 2 and the covering members 3, 3 ', the reinforcing plate members 4, 4', and the reinforcing frame members, is particularly preferred. There is no limitation, and conventionally known fixing tools such as tapping screws and sleeves and conventionally known fixing agents such as epoxy-based, isocyanate-based, cyanoacrylate-based, hot-melt-based, and rubber-based adhesives and double-sided adhesive tapes are appropriately used. Just fix it.

There is no particular limitation on the manner in which the covering members 3 and 3 'are provided on the radio wave absorber 2. For example, the cover members 3 and 3' are joined to the radio wave absorber 2 by a double-sided adhesive tape, the above-mentioned adhesive, or a combination thereof, and And is fixed to the radio wave absorber 2 using a dedicated jig. From the viewpoint that the dent near the center can be suppressed, it is preferable to perform the fixing using a sleeve.

As described above, the radio wave absorber 2 of the present invention can be realized in various forms such as a fiber mat type, a single layer type, a multilayer type and a non-woven type. In the case of the single-layer type, as a material for forming the radio wave absorbing layer, for example, a foamed resin mixed with carbon or ferrite is exemplified. A particularly preferred radio wave absorber in the present invention is of a fiber mat type, and is formed of, for example, a conductive fiber assembly. As the fiber assembly, a fiber formed by entanglement of fibers of any length and thickness into a mat shape is used, but a fiber obtained by fusing the entanglement points of fibers, a fiber bonded by an adhesive material, or a fiber However, a material that exhibits a stable mat shape simply by entanglement can be used. The conductivity of the fiber aggregate is imparted by using, for example, fibers having a surface coated with a conductive paint.

The fibers forming the fiber aggregate include cotton,
Natural fibers such as hemp and organic polymer fibers such as organic synthetic fibers can be used. The type of the organic synthetic fiber is not particularly limited, and examples thereof include polyvinylidene chloride, nylon resin, polyester resin, and acrylic resin. Of these, polyvinylidene chloride is particularly preferable.

Examples of the conductive paint include a paint such as a mixture of an organic polymer latex and an aqueous conductive paint which contains a conductivity imparting agent capable of forming a lossy dielectric layer on the fiber surface by coating and drying. Can be used.

As the organic polymer latex, emulsions of various organic polymers can be used.
Among them, those showing a good adhesive action to organic polymer fibers are particularly preferred. When the organic polymer fiber is a polyvinylidene chloride fiber, for example, an emulsion of polyvinylidene chloride or an emulsion of a mixture of polyvinylidene chloride and polyvinyl chloride is exemplified.

As the aqueous conductive paint, an aqueous paint containing a binder and a conductivity-imparting agent is used. Examples of the binder include inorganic binders such as fine powder, especially colloidal clay, bentonite, mica, silicate, and diatomaceous earth, and organic binders such as polyvinyl alcohol and an acrylic resin mold part. Examples of the conductivity-imparting agent include graphite, carbon, and conductive metal powder.

The radio wave absorption panel of the present invention can be easily subjected to various processes for installation and mounting. Hereinafter, some examples of processing that are preferable for installing the present invention on, for example, a ceiling, a side wall, or under an elevated structure of a building will be described, but processing that can be performed on the present invention is not limited thereto.

FIG. 5 is a simplified sectional view showing an example of processing of the radio wave absorbing panel of the present invention. In the example shown in FIG. 5, a support member 8 having a U-shaped cross section is attached to the end portion in the first width direction X of the radio wave absorption panel 1 of the example shown in FIGS. 1 and 2 along the second width direction Y. Become. The support member 8 is preferably formed of, for example, a galvanized steel sheet.

The support members 8 as described above are attached to both ends of the radio wave absorbing panel 1 in the first width direction X, and are provided at appropriate places according to the size of the radio wave absorbing panel 1 at a place where the radio wave absorbing panel 1 is to be installed, for example, a ceiling of a building. A pair of rail members (not shown) provided substantially in parallel with a gap is provided in advance, and the radio wave absorbing panel 1 is fitted to the rail members by the support member 8. As a result, the radio wave absorbing panel 1 can be suitably installed at a target place.

The shapes of the support member 8 and the rail member are not particularly limited as long as they are selected to be a combination that can be fitted to each other and can be suitably installed at the installation location. For example, the rail member may be formed in an I-shape or an H-shape, and may be realized in a shape such that the support member 8 can fit therein.

FIG. 6 is a simplified sectional view showing another example of the processing of the radio wave absorbing panel of the present invention. The example shown in FIG. 6 is a process suitable for the case where the radio wave absorption panel 1 of the example shown in FIGS. 1 and 2 is to be suspended and installed below a ceiling or an overpass of a building. In the example of FIG. 6, support members 9 that support one Z1 side in the thickness direction of the panel 1 and extend outward in the second width direction Y are provided at both ends in the second width direction Y of the radio wave absorption panel 1. Attach. The support member 9 has an insertion hole in a portion 9a that spreads outward in the second width direction Y. The hanging member 10 is inserted through the insertion hole, and is fixed using the fastener 11 or the like. Such a hanging member 10 is inserted through a hole formed in advance in a place where the installation is desired, for example, a ceiling 12 of a building or the like, and is fixed using a fastener 13 or the like. As a result, the radio wave absorbing panel 1 can be suspended and suitably installed at a target place.

The support member 9 is also formed of, for example, a galvanized steel sheet, like the above-described support member 8, and is preferably formed of a galvanized steel sheet. Further, as shown in a simplified cross-sectional view of FIG. 7, a place where the support member 9 is to be installed by using the fastener 14 or the like with the insertion hole of the portion 9 a extending outward in the second width direction Y as shown in FIG. For example, it may be directly installed on the ceiling 15 of a building or the like.

The radio wave absorbing panel 1 of the embodiment shown in FIGS. 3 and 4 can be appropriately set in a place where unwanted unnecessary radio waves are to be removed by performing various processes similar to those described above.

The place where the radio wave absorption panel of the present invention is installed is not particularly limited, but it is preferably installed on the ceiling of a tollgate on a toll road where a non-stop automatic toll collection system (ETC system) which is a part of ITS is implemented. It is preferably installed. FIG. 8 is a simplified view showing an example in which the radio wave absorbing panel 1 of the example shown in FIG. 1 is installed on the ceiling 22 of the tollgate 21. The tollgate 21 is provided with a transmission / reception antenna 23 for exchanging information regarding toll collection with a vehicle 24 equipped with an in-vehicle device having the automatic toll collection function. The transmitting / receiving antenna 23 is connected to the vehicle 24 traveling on a road 25 connected to the tollgate 21 by the transmitting / receiving antenna 2.
3 communication area 26 (area surrounded by a virtual line in FIG. 8)
When the vehicle enters the vehicle, the information is exchanged with the vehicle 24. The radio wave absorbing panel 1 is installed so that the radio wave incident side (one side in the thickness direction Z1) of the radio wave absorber 2 faces the communication area 26 (the area surrounded by a virtual line in FIG. 8).

The communication equipment used in the ETC system has high reliability such as a communication error rate of 10 ^-6 or less, and is a communication between the transmitting / receiving antenna 23 and the vehicle 24. It is required to be able to cope with the vehicle traveling speed up to h.
By installing the radio wave absorbing panel of the present invention on the ceiling 22 of the tollgate 21 as described above, radio waves transmitted from the transmitting / receiving antenna 23 and reflected on the road surface 25a, the roof of the vehicle 24, and the like can be absorbed. As a result, overreach of radio waves and irregular reflection of radio waves in the communication area 26 can be prevented.
The reliability of the communication device in the TC system can be improved.

FIG. 8 shows an example in which the radio wave absorbing panel is installed on the ceiling 22 of the toll booth 21. However, the present invention is not limited to this, and may be installed on an elevated area near the toll booth or on the side wall of the toll booth. . However, it is assumed that the radio wave incident side of the radio wave absorber 2 faces the communication area 26 of the transmitting / receiving antenna 23, and the radio wave absorber 2 is appropriately installed so that the reflected radio wave is easily incident.

[0039]

The present invention will be described in detail with reference to the following examples, but the present invention is not limited to the following examples. Example 1 As a radio wave absorber 2, bulk density 50 kg / m ³ , thickness 2
A vinylidene chloride synthetic fiber having a thickness of 0 mm (thickness: 80 denier, 120 denier, 100 denier) was entangled and molded, and subjected to a conductive treatment with a graphite paint and latex. The size of the radio wave absorber 2 is such that the first width is 0.867.
m, the second width was 1.8 m, and the thickness was 2 cm. On one Z1 side in the thickness direction of such a radio wave absorber 2, an unsaturated polyester resin-based FRP resin (Suncoat Glasslight, Nitto Boseki) containing 20% of an acrylic resin as shown in FIGS. (Made by the company) (dielectric constant ε
r: 6.0, first width: 0.867 m, second width: 1.8
m, thickness t: 0.7 mm) as the coating material 3. The fixing of the coating material 3 was performed by bonding with a special silicone-modified polymer adhesive (PM100, manufactured by Cemedine). On the other Z2 side in the thickness direction of the radio wave absorber 2, a reinforcing frame member formed by combining a hat-type galvanized steel plate as described above is placed, and the radio wave absorber 2 is sandwiched between the sheet-shaped body and a sleeve. Fixed. The hat-type galvanized steel sheets were joined by welding. From the other Z2 side in the thickness direction, a flat plate (first width: 0.867 m, second width: 1.8 m, thickness: 0.5 mm) made of aluminum-plated steel is used as the reinforcing plate 4 and a tapping screw is attached. And fixed to a reinforcing frame member to obtain a radio wave absorbing panel 1 of the example shown in FIG.

Example 2 As shown in FIGS. 3 and 4, a coating material 3 '(dielectric constant) made of an acrylic resin (acrylic sand plate, manufactured by Acrylic Sunday Co., Ltd.) realized in a casing having an opening on one side. εr: 3.0, first width: 0.867 m, second width:
1.8 m, thickness t: 1 mm) is attached so as to cover from one Z1 side in the thickness direction of the radio wave absorber 2, and a square corrugated plate made of aluminized steel (first width:
0.867 m, second width: 1.8 m, thickness: 0.5 mm,
Except for using the angular wave pitch: 12.5 cm), the radio wave absorbing panel 1 ′ of the example shown in FIG.
I got

Example 3 As a covering material, a foamed polyvinyl chloride resin (FOREX,
(Acrylic Sunday) sheet (dielectric constant εr:
2.0, thickness t: 2 mm), except that a radio wave absorbing panel was obtained in the same manner as in Example 1.

Example 4 As a coating material, a foamed polyvinyl chloride resin (FOREX,
(Acrylic Sunday) sheet (dielectric constant εr:
2.0, thickness t: 1 mm), except that a radio wave absorbing panel was obtained in the same manner as in Example 1.

Comparative Example 1 A radio wave absorbing panel was prepared using the radio wave absorber of Example 1 as it was.

Comparative Example 2 As a coating material, a sheet-like body (dielectric constant εr: made of acrylic resin (acrylic sundae board, manufactured by Acrylic Sunday Co., Ltd.)
3.0, thickness t: 2 mm), except that a radio wave absorbing panel was obtained in the same manner as in Example 1.

Comparative Example 3 As a coating material, an unsaturated polyester resin-based FRP resin (manufactured by Sakai Sangyo Co., Ltd.) (a dielectric constant εr:
6.0, thickness t: 1 mm), to obtain a radio wave absorbing panel in the same manner as in Example 1.

In each of Examples 1 to 4 and Comparative Examples 1 to 3, the incident angle was set to 1 by the arch method (reflected power method).
The frequency is changed from 0 ° to 60 ° in steps of 10 ° at a frequency of 5.8.
The radio wave absorption performance of each of the TE wave and the TM wave of GHz (wavelength λ = 51.7 mm) was evaluated. Table 1 shows the results.

[0047]

[Table 1]

As shown in Table 1, the radio wave absorbing panels of Examples 1 to 4 generally have improved radio wave absorbing performance as compared with Comparative Example 1 in which no covering material is provided. It was confirmed that the absorption performance at an angle was improved. In addition, by using a coating material that satisfies the condition that the value represented by (εr × t) / λ is 0.1 or less, as is clear from comparison with Comparative Examples 2 and 3, radio wave absorption at a low incident angle Performance can be improved.

[0049]

As is apparent from the above description, according to the present invention, it is difficult for foreign substances such as water, dust and exhaust gas to penetrate into the inside of the radio wave absorber, and the radio wave absorber has a sufficient light-absorbing ability with light weight and thinness. And a radio wave absorbing panel having the same. In particular, if a coating material that satisfies the condition that the value represented by (εr × t) / λ is 0.1 or less is used, as described in the examples, the radio wave absorption performance is improved, and the oblique incidence characteristics are improved. A good radio wave absorption panel can be realized.

[Brief description of the drawings]

FIG. 1 is a simplified perspective view showing a preferred example of a radio wave absorbing panel 1 of the present invention;

FIG. 2 is an exploded perspective view showing a simplified structure of the radio wave absorbing panel 1 of FIG.

FIG. 3 is a radio wave absorbing panel 1 'according to another preferred embodiment of the present invention.
FIG.

FIG. 4 is an exploded perspective view showing a simplified structure of a radio wave absorbing panel 1 ′ of FIG. 3;

FIG. 5 is a simplified sectional view showing an example of processing of the radio wave absorbing panel 1 of the present invention.

FIG. 6 is a simplified cross-sectional view showing another example of processing the radio wave absorption panel 1 of the present invention.

FIG. 7 is a simplified sectional view showing still another example of processing of the radio wave absorption panel 1 of the present invention.

FIG. 8 is a simplified view showing an example in which the radio wave absorbing panel 1 of the present invention is installed on the ceiling 22 of the tollgate 21.

[Explanation of symbols]

 1,1 'radio wave absorbing panel 2 radio wave absorber 3,3' covering material 4,4 'reinforcing plate

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takayoshi Mitsui 663 Minoshima, Arita City, Wakayama Prefecture Mitsubishi Cable Industry Co., Ltd.Minoshima Works (72) Inventor Cho Hashimoto 1-23-9 Imaikecho, Anjo City, Aichi Prefecture (72) Inventor Yasuyuki Nishimura 663 Mishima, Arita City, Wakayama Prefecture F-term (reference) 2E001 DH01 GA03 GA06 GA12 GA24 GA28 GA29 GA42 GA53 GA55 GA58 GA76 HB02 HB04 HB07 HD01 HD11 HD12 HD13 HD14 JA00 JA06 JB01 JC06 JC07 JC08 JD04 LA01 LA04 LA12 2E162 BA02 BB02 BB03 BB06 CB01 CB02 CB03 CD01 CD04 CD05 CD06 FA00 5E321 AA44 BB23 BB32 CC16 CC16 CC16

Claims (7)

[Claims] 1. A radio wave absorption panel comprising: a flat-shaped radio wave absorber; and a covering material having radio wave permeability and covering at least a portion of the radio wave absorber intended to receive radio waves, wherein the covering material is A radio wave absorption panel provided so as to suppress intrusion of foreign matter into the radio wave absorber. 2. The radio wave absorbing panel according to claim 1, wherein the covering material is a sheet formed of an organic polymer material. 3. When the dielectric constant of the coating material is εr, the thickness is t, and the wavelength of the radio wave to be absorbed is λ, (εr × t) /
The radio wave absorption panel according to claim 1, wherein a value represented by λ is 0.1 or less. 4. The method according to claim 1, further comprising a reinforcing plate on the back side of a portion intended to receive radio waves.
3. The radio wave absorption panel according to any one of 3. 5. A radio wave absorbing panel comprising: a flat plate-shaped radio wave absorber; and a covering material having radio wave permeability and covering at least a part of the radio wave absorber intended to receive radio waves, A radio wave absorption panel wherein a value represented by (εr × t) / λ is 0.1 or less, where εr is a dielectric constant, t is a thickness, and λ is a wavelength of a radio wave intended to be absorbed. 6. The radio wave absorption panel according to claim 1, wherein the radio wave absorber comprises an aggregate of conductive fibers. 7. A tollgate on a toll road provided with a transmission / reception antenna for transmitting / receiving information to / from a vehicle equipped with an on-board unit having an automatic toll collection function, a radio wave absorber is provided in a communication area of the transmission / reception antenna. The radio wave absorption panel according to any one of claims 1 to 6, wherein the panel is used so as to face.