JPH06209180A - Inner wall material for absorbing electromagnetic wave - Google Patents

Abstract

PURPOSE:To enable suitable electromagnetic wave shielding conformable to electromagnetic waves of each frequency which is used in a building, by containing electromagnetic wave attenuating material in inner wall material for absorbing electromagnetic waves. CONSTITUTION:Main material of the inner wall material for absorbing electromagnetic waves is gypsum or asbestos cement or calcium silicate, an the following electromagnetic wave attenuating material is contained; carbon, ferrite, metal powder or metal compound powder or mixture of them. The thickness of the inner wall material plate is set smaller than or equal to 50mm. The weight percentage of the electromagnetic wave attenuating material is set in a range of 1-20%, in order to obtain a reflectivity of 0.65 or smaller and the transmittance of 0.65 or smaller for electromagnetic waves having desired frequencies contained in the frequency region of 70MHz-3GHz. By using the inner wall material conformable to each frequency band, the electromagnetic wave control conformable to frequency of electromagnetic waves used in a building is enabled, and tempest shield and zone management can be effective.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a building inner wall material, and more particularly to an inner wall material absorbing electromagnetic waves.

[0002]

2. Description of the Related Art In recent years, it has become common sense to use radio waves as information transmission means, and radio waves in all frequency bands are flying around in space. Also, due to the high-rise buildings that are scattered,
These buildings themselves act as reflectors of radio waves, and the radio waves are diffusely reflected, and radio interference is a major social problem. This radio interference is VH used for FM broadcasting and TV broadcasting.
The so-called ghost, which is conspicuous in the F and UHF frequency bands and appears on a television screen or the like, is mainly.

Conventionally, concrete,
There is provided an electromagnetic wave absorbing outer wall material in which ferrite powder is mixed with an outer wall material such as mortar (Japanese Patent Publication No. 52-2735).
5). This electromagnetic wave absorbing outer wall material absorbs irregularly reflected electric waves by using the electromagnetic wave loss characteristic of ferrite, and prevents the electric wave interference such as the ghost. Therefore, the larger the absorption rate of radio waves, the more preferable.

On the other hand, gypsum board, asbestos cement board, calcium silicate board or the like is generally used as the inner wall material of the building, and these inner wall materials have the property of completely transmitting electromagnetic waves. FIG. 3 shows the electromagnetic wave energy reflection / transmission characteristics of the gypsum board. As is clear from FIG. 3, the gypsum board exhibits perfect transmission (T = 1) and zero reflection (R = 0) characteristics.

Recently, however, cordless telephones, car telephones and the like have come to be used due to the progress of the advanced information society, and in addition to radio waves in the VHF and UHF frequency bands, 1.
Radio waves in the 5 GHz radio band have also come to be used.
In addition, since multiple channels are used in one office building for cordless phones, a new problem in the building is a new problem of radio wave interference, that is, communication failure due to interference and leakage of confidential information to the outside. Is happening.

This new problem cannot be solved by simply suppressing the reflection of radio waves by using the outer wall material for the inner wall of the building. This is because it is necessary to prevent the confidential information from leaking to the outside of other floors and buildings, and to effectively perform wireless communication between the same floors. In addition, if shield processing is performed so that radio waves are diffusely reflected, the diffused radio waves may adversely affect electronic devices and human bodies, and this point must be taken into consideration. In response to such problems, recently, a tempest shield for optimal control of radio waves (an electromagnetic wave shield constructed to prevent information from leaking outside in the form of electromagnetic waves) and wireless communication in buildings There is an increasing need for zone management (setting a predetermined area in the building so that the electromagnetic waves used for information transmission can be used without obstruction) in order to effectively use such information. .

Conventionally, as an electromagnetic wave shield in a building, a metal plate, a metal foil, or a metal mesh having electromagnetic wave perfect reflection characteristics is attached to a ceiling, a wall, a floor, etc. of a room or an area where the electromagnetic wave shield is required, or a metal-containing material is contained. The electromagnetic wave shield construction method of applying paint is adopted. FIG. 4 shows electromagnetic wave energy reflection / transmission characteristics of a metal plate which is a conventional electromagnetic wave shield material. As is clear from FIG. 4, the metal plate exhibits perfect reflection (T = 1) and zero transmission (R = 0) characteristics.

However, when adopting the electromagnetic wave shield construction method using the metal plate or the like, a general building is
There are windows, internal wiring, air-conditioning ports, etc. It is very difficult to shield all of these, considering the habitability, and it is not easy to realize from the cost aspect. In addition, if the shield treatment of the air conditioning port is incomplete, the metal plate or the like completely reflects the electromagnetic wave, so that the incomplete shielded portion may become a propagation path of the electromagnetic wave. In some cases, the situation may be worse than before the shield treatment.

In order to prevent information from leaking to the outside in the form of electromagnetic waves, it is not necessary to completely shield the electromagnetic waves, and it is sufficient to prevent the electromagnetic waves from leaking as effective information. . Further, regarding the fear of the electronic equipment being damaged by radio waves, it is not necessary to completely block the electromagnetic waves that irradiate the electronic equipment, and it is sufficient to absorb and attenuate the electromagnetic wave energy to the extent that the electronic equipment is not damaged. .

Therefore, an object of the present invention is to achieve an appropriate electromagnetic wave shield adapted to the electromagnetic waves of each frequency used in a building, and to have an electromagnetic wave absorption characteristic in order to make the tempest shield and zone management effective. It is to provide an inner wall material.

[0011]

The electromagnetic wave absorbing inner wall material according to claim 1 is mainly composed of gypsum, asbestos cement or calcium silicate and is an electromagnetic wave loss material such as carbon, ferrite, metal powder or metal compound powder or these. It is characterized by containing a mixture of.

An electromagnetic wave absorbing inner wall material according to a second aspect is the electromagnetic wave absorbing inner wall material according to the first aspect, wherein the inner wall material is formed into a plate material having a thickness of 50 mm or less and a frequency in a band of 70 MHz to 3 GHz. The weight ratio of the electromagnetic wave loss material is set in the range of 1% to 20% so that the reflectance is 0.65 or less and the transmittance is 0.65 or less for the electromagnetic wave of the desired frequency contained. It is characterized by being.

[0013]

According to the electromagnetic wave absorbing inner wall material of the first aspect, by containing an electromagnetic wave loss material such as carbon in the inner wall material, the inner wall material appropriately attenuates and absorbs the energy of the irradiated electromagnetic wave. can do. Further, since the main material of the inner wall material is gypsum or the like which has been conventionally used, the inner wall material can be manufactured simply by mixing an electromagnetic wave loss material such as carbon into the conventional inner wall material.

According to the electromagnetic wave absorbing inner wall material of the second aspect, it is possible to construct an electromagnetic wave absorbing inner wall material having compatibility with the inner wall material which has been generally used in the past. In addition, by incorporating a predetermined amount of an electromagnetic wave loss material such as carbon into the inner wall material within a weight ratio of 1% to 20% with respect to electromagnetic waves in a desired frequency band of 70 MHz to 3 GHz, the desired frequency can be reduced. It is possible to provide an inner wall material having a reflectance of 0.65 or less and a transmittance of 0.65 or less in the band.

[0015]

EXAMPLES Examples will be described below. In this example, an inner wall material (hereinafter referred to as "sample") having a thickness of 50 mm in which only plaster contained carbon was prepared, and the reflection and transmission characteristics of electromagnetic waves were examined for two kinds of content rates. The results are shown below.

Example 1 When the weight ratio is 1 gypsum 16 to carbon (content rate 5.9%) FIG. 1 shows the reflection and transmission characteristics of electromagnetic waves. From FIG. 1, the measurement frequency band is 100 MHz to 900 MHz, and in this range, both reflectance and transmittance are in the range of 0.25 ± 0.06. For example, when a sample is irradiated with a radio wave of 500 MHz, the reflectance is R = 0.19 and the transmittance T = 0.31, so the absorptance is 0.5.

Example 2 When the weight ratio of carbon to gypsum 12 was 1 (content rate: 7.7%) The reflection and transmission characteristics of electromagnetic waves are shown in FIG. From FIG. 2, the measurement frequency band is 100 MHz to 900 MHz, and in this range, the reflectance is 0.35 to 0.55 and the transmittance is 0.05 to 0.25. For example, 50
When the sample is irradiated with a radio wave of 0 MHz, the reflectance R =
Since the transmittance is 0.35 and T = 0.13, the absorptance is 0.
52.

From the first embodiment, the frequency band from 100 MHz
At 900MHz, if the carbon content is set to 5.9%, the reflectance and transmittance of the radio wave radiated to the sample becomes 0.25 ± 0.06, and about half the energy of the radio wave radiated is absorbed. I understand that it will be done. Further, from the second embodiment, the frequency band 100 MHz to 90 is the same as the first embodiment.
If the carbon content is set to 7.7% at 0 MHz, the frequency of the radio wave irradiated to the sample is 100 MHz.
Although the electromagnetic wave energy has a transmittance of 0.25, the transmittance is about 0.1 over almost the entire frequency band. On the other hand, the reflectance shows a value of 0.35 to 0.55, which shows that about 40% to 60% of the energy of the irradiated radio wave is absorbed.

If both the reflectance and the transmittance of the irradiated radio wave are 0.65 or less, the attenuation is about 2 dB, and it is considered that there is no possibility of leaking to outside as effective information. Therefore, the samples of Examples 1 and 2 above have a frequency band 1
At 00 MHz to 900 MHz, it has electromagnetic wave absorption characteristics necessary and sufficient to prevent leakage as effective information.

The difference in the electromagnetic wave absorption characteristics is due to the difference in the amount of carbon to be contained. By incorporating ferrite or metal powder in addition to carbon, the electromagnetic wave absorption characteristics satisfy various needs. An inner wall material can be provided. That is, carbon has a remarkable reflection characteristic when the content is too large, but mainly has an action of converting electromagnetic wave energy into heat and attenuating the energy, and ferrite has a function of shifting the phase of the irradiated electromagnetic wave to cause electromagnetic waves. There is an action of attenuating energy by mutual interference of.
In addition, when it is desired to positively reflect electromagnetic waves, a predetermined amount of metal powder may be contained. Therefore, by containing a predetermined amount of each of these alone or in combination, the inner wall material can have desired electromagnetic wave reflection, transmission and absorption characteristics. However, regarding the above content, when it is contained in a weight ratio of less than 1%, it has almost no characteristics as an electromagnetic wave absorber, and it is not possible to manufacture an inner wall material in a content of more than 20% by weight. Have difficulty. Also, 20
Even if it is possible to manufacture an inner wall material containing a weight ratio exceeding 100%, the inner wall material has almost perfect reflection characteristics and does not have characteristics as an electromagnetic wave absorber. In the first and second embodiments, the measurement frequency band is 100 MHz to 900M.
Although it was measured only in Hz, it is possible to provide an inner wall material having a desired electromagnetic wave shielding property in a desired frequency band by changing the content ratio of carbon, ferrite, etc. to be contained and setting a predetermined content ratio. .

Therefore, in addition to the above two examples, by setting a predetermined weight ratio within the above range of content, 2d
It is possible to provide an inner wall material having a damping characteristic of about B. For example, 70 MHz to 400 MHz inner wall material, 400 MH
Inner wall material for z to 900 MHz, 900 MHz to 1.5
It is possible to manufacture an inner wall material for a desired frequency band such as an inner wall material for GHz and an inner wall material for 1.5 GHz to 3 GHz. As a result, it is possible to selectively use the inner wall material having a desired electromagnetic wave absorption characteristic in the frequency band of the radio waves mainly used in the building. Specifically, for example, if the inner wall material for the 1.5 GHz radio wave band is used, it is possible to prevent leakage of confidential information when using a cordless telephone in a building, and to perform good wireless communication in a predetermined area. I can do it.

Further, radio waves other than the radio wave band for which the shield is required are not disturbed. That is, for example, 1.
Even if the radio waves when using a cordless telephone are controlled by using the inner wall material for the 5 GHz radio band, the radio waves of TV broadcasting can be received in a normal state. As described above, according to the electromagnetic wave absorbing inner wall material of the present invention, it is possible to achieve an electromagnetic wave shield that is suitable for each frequency of the electromagnetic wave that is mainly used in the building, and it is possible to make the tempest shield and zone management effective. In addition, since an electromagnetic wave loss material such as carbon is simply mixed into a conventional gypsum board or the like, it is possible to provide an inexpensive and compatible inner wall material.

Next, with reference to FIG. 5, the measurement of the reflectance or transmittance of the irradiated electromagnetic wave will be described. The sample 1 is sandwiched and the sample 1 is irradiated with the radio wave Po from the radio wave source on one side. A reflected wave Pr from the sample 1 is detected by a reflected wave detection device (not shown) installed on the same side as the radio wave source. Also,
The transmitted wave Pt transmitted through the sample 1 is detected by a transmitted wave detecting device (not shown) placed on the other side of the sample 1. Then, the reflectance and the transmittance are measured by the ratio of Po to Pr and Pt, respectively.

If the reflectance and the transmittance can be measured, it is considered that all but the reflected or transmitted radio waves have been absorbed, and the absorptance is calculated. In this embodiment, gypsum contains only carbon, but the main material of the inner wall material may be asbestos cement, calcium silicate or the like in addition to gypsum. In addition, the thickness of the inner wall material that is usually used is 3 mm to 35 mm, and the thickness exceeding 50 mm is practically unusable. In this embodiment, the thickness of the inner wall material was limited to 50 mm, but the same effect as described above can be obtained even when the thickness is 50 mm or less.

In addition, various design changes can be made without changing the gist of the present invention.

[0026]

According to the electromagnetic wave absorbing inner wall material of the first aspect, it is possible to impart desired electromagnetic wave absorbing characteristics in a desired frequency band by the effect of the electromagnetic wave loss material contained in the inner wall material. An inner wall material can be provided. Moreover, an inner wall material having compatibility can be manufactured at a low cost simply by including an electromagnetic wave loss material such as carbon with a main material such as gypsum which has been generally used conventionally.

The electromagnetic wave absorbing inner wall material according to the second aspect of the present invention is used in the building from the VHF and UHF radio wave bands to the 1.5 GHz radio wave band for mobile phones, car phones, etc., whose usage rate has recently increased. With respect to the radio waves in the range up to, the energy of the applied electromagnetic wave is attenuated every time the electromagnetic wave is reflected and transmitted. Therefore, it is possible to prevent confidential information from leaking as effective information even when a predetermined area is partitioned in the building by the inner wall material and wireless communication using a cordless telephone or the like is performed.
Good wireless communication is possible in the area. In addition, it is possible to prevent the electronic devices existing outside the area from being adversely affected.

As described above, by selectively using the inner wall material adapted to each frequency band, the electromagnetic wave adapted to the frequency of the electromagnetic wave used in the building can be controlled.
Enable Tempest Shield and zone management.

[Brief description of drawings]

FIG. 1 is a diagram showing electromagnetic wave reflection / transmission characteristics of an electromagnetic wave absorbing inner wall material according to a first embodiment of the present invention.

FIG. 2 is a diagram showing electromagnetic wave reflection / transmission characteristics of an electromagnetic wave absorbing inner wall material according to a second embodiment of the present invention.

FIG. 3 is a diagram showing reflection and transmission characteristics of electromagnetic waves in a gypsum board.

FIG. 4 is a diagram showing an electromagnetic wave reflection / transmission characteristic of a metal plate.

FIG. 5 is a schematic diagram of a method for measuring the reflection and transmittance of electromagnetic waves.

[Explanation of symbols]

 1 Sample Po Radio wave energy emitted from radio wave source Pr Reflected radio wave energy Pt Transmitted radio wave energy T Transmittance R Reflectance

Claims (2)

[Claims] 1. An electromagnetic wave absorbing inner wall containing gypsum, asbestos cement or calcium silicate as a main material and containing carbon, ferrite, metal powder or metal compound powder, which is an electromagnetic wave loss material, or a mixture thereof. Material. 2. The electromagnetic wave absorbing inner wall material according to claim 1, wherein the inner wall material is formed of a plate material having a thickness of 50 mm or less, and an electromagnetic wave of a desired frequency contained in a band of 70 MHz to 3 GHz, With a reflectance of 0.65 or less,
The electromagnetic wave absorbing inner wall material is characterized in that the weight ratio of the electromagnetic wave loss material is set in the range of 1% to 20% so that the transmittance is 0.65 or less.