JP4409368B2 - Radio wave absorber - Google Patents

Description

  The present invention relates to a radio wave absorber.

In recent years, the use of information terminal devices such as mobile phones has been rapidly increasing.
In particular, two types of radio waves for wireless LAN, 2.45 GHz and 5.2 GHz, are allocated and information is transmitted using personal computers, mobile phones, and mobile terminals using radio waves of that frequency. Malfunctions of equipment due to unnecessary radio waves (radio waves generated by reflections, etc.) have become a problem, and various measures for improving the radio wave environment have been studied.
Therefore, a radio wave absorber for a wireless LAN is installed in the room, but it is also installed in a window in order to sufficiently absorb unnecessary radio waves. Therefore, in order to maintain the living environment without blocking the inflow of light from the outside, it is necessary to provide the radio wave absorber with translucency.
Therefore, a λ / 4 type radio wave absorber having a resistance layer (film), a dielectric layer (body), and a conductive layer (radio wave reflector) is known as a radio wave absorber for indoor wireless LAN having translucency. (For example, refer to Patent Documents 1 and 2) Indium tin oxide (ITO) or the like is used as the resistance layer, and transparent resin or glass is used as the dielectric layer.
JP-A-5-335832 Japanese Patent Laid-Open No. 6-120688

This conventional radio wave absorber exhibits sufficient absorption characteristics for one wave (one radio wave), but is not sufficient for two waves (such as frequencies of 2.45 GHz and 5.2 GHz). If this radio wave absorber is used to provide absorption characteristics for two waves of 2.45 GHz and 5.2 GHz, it is necessary to devise measures such as placing radio wave absorbers with different characteristics on windows or the like. Installation in a place where the size of the room is fixed is difficult.
Furthermore, when a resin is selected as the dielectric layer, a nonflammable effect cannot be expected.
In addition, when glass is selected as the dielectric layer, sufficient absorption characteristics are not exhibited for two waves of 2.45 GHz and 5.2 GHz.

  Therefore, the present invention has a radio wave absorption characteristic with a return loss of 20 dB or more with respect to radio waves of 2.45 GHz and 5.2 GHz for indoor wireless LAN, and has translucency and is installed in a window. However, an object of the present invention is to provide a radio wave absorber capable of entering light from the outside into the room and having nonflammability.

In order to achieve the above object, the radio wave absorber according to the present invention has a first glass layer, a first transparent resin layer, and a surface resistance value of 150 to 250 Ω / □ in order from the side on which the radio wave enters. a resistor layer, and a second transparent resin layer comprises a conductive layer, a second glass layer, the thickness dimension of the first transparent resin layer is set to 6mm to 9 mm, and the second transparent resin layer The thickness dimension of the first and second transparent resin layers is set to 4 or less, and the thickness dimension of the first and second transparent resin layers is set to 4 or less, so that two types of radio waves are absorbed.

The first and second transparent resin layers are made of polycarbonate or acrylic.
The first and second glass layers were set to have a thickness dimension of 1 to 2 mm and a dielectric constant of 5 to 8.
The surface resistance value of the conductive layer was set to 25Ω / □ or less.
It is also used to absorb radio waves for indoor wireless LAN.

The present invention has the following remarkable effects.
With respect to two types of radio waves for 2.45 GHz and 5.2 GHz for wireless LAN, it is surely effective return loss and has sufficient radio wave absorption characteristics.
Therefore, if it is used on indoor walls and ceilings, it can reliably absorb unwanted radio waves and suppress unwanted radio waves generated by reflections, etc. It is possible to efficiently absorb unnecessary reflected waves (unnecessary radio waves) for a wireless LAN such as a portable terminal and prevent malfunction of the device.
Thus, a great effect can be exhibited as a measure for improving the radio wave environment.
Furthermore, since it has sufficient translucency, even if it is installed in a window, light can enter the room from the outside. Moreover, since it is thin, there is no fear of getting in the way. Therefore, it can be installed everywhere in the room, and unnecessary radio waves can be sufficiently suppressed. Furthermore, since it has nonflammability defined as usable as an interior material by the Building Standard Law, it is suitable for indoor use.

Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments.
As shown in FIG. 1, the radio wave absorber 10 includes a first glass layer 21, a first transparent resin layer 11, a resistance layer 2, a second transparent resin layer 12, The conductive layer 3 and the second glass layer 22 are laminated.

Each component will be specifically described.
First, the first and second glass layers 21 and 22 are preferably made of a material such as soda lime.
The first and second glass layers 21 and 22 have thickness dimensions T ₂₁ and T ₂₂ set to 1 mm to 2 mm, more preferably 1.3 mm or more for the lower limit, and more preferably 1.7 mm or less for the upper limit. The dielectric constant is set to 5 to 8, and the lower limit is more preferably 6.8 or more, and the upper limit is more preferably 7.2 or less.
In particular, the first and second glass layers 21 and 22 are preferably set such that the thickness dimensions T ₂₁ and T ₂₂ are set to 1.5 mm and the dielectric constant is set to 7.
If the dielectric constant is less than 5 or more than 8, the return loss (of the radio wave absorber 10) with respect to two types of radio waves for indoor wireless LANs, 2.45 GHz and 5.2 GHz, is less than 20 dB, which is sufficient It becomes difficult to obtain radio wave absorption characteristics.
Also, if the thickness dimensions T ₂₁ and T ₂₂ are less than 1 mm, a sufficient non-combustible effect may not be obtained, or if it exceeds 2 mm, two types of 2.45 GHz and 5.2 GHz for indoor wireless LAN are used. The return loss of the radio wave (of the radio wave absorber 10) is less than 20 dB, making it difficult to obtain sufficient radio wave absorption characteristics.

Next, the resistance layer 2 will be described. The surface resistance value is set to 150 to 250Ω / □. The lower limit is more preferably 195Ω / □ or more, and the upper limit is more preferably 225Ω / □ or less, and in particular 200Ω / □.
If the surface resistance value is less than 150Ω / □ or more than 250Ω / □, the return loss (of the radio wave absorber 10) with respect to two types of radio waves of 2.45GHz and 5.2GHz for indoor wireless LAN is 20dB. It becomes difficult to obtain sufficient radio wave absorption characteristics.
The resistance layer 2 preferably has a material such as an indium tin oxide (ITO) film.

Next, the first transparent resin layer 11 and the second transparent resin layer 12 will be described. In both cases, the dielectric constant is set to 4 or less, and more preferably 3 or less. Moreover, what has materials, such as a polycarbonate or an acryl, is preferable.
Furthermore, the thickness dimension T ₁₁ of the first transparent resin layer 11 is set to 6 mm to 9 mm. The lower limit is more preferably 6.5 mm or more, and the upper limit is more preferably 8.5 mm or less. Or a thickness dimension T ₁₁ is 6mm less than or 9mm exceeded, and when the dielectric constant is 4 exceeded 2.45 GHz for indoor wireless LAN, and for two different radio wave 5.2 GHz (the wave absorber 10) reflected The attenuation is less than 20 dB, and it is difficult to obtain sufficient radio wave absorption characteristics. In particular, the first transparent resin layer 11 is preferably set to have a thickness dimension T ₁₁ of 7 mm and a dielectric constant of 2.73.
On the other hand, the thickness T ₁₂ of the second transparent resin layer 12 is set to 10mm to 13 mm. More preferably, the lower limit is 12 mm or more. Or a thickness dimension T ₁₂ is 10mm below and 13mm exceeded, and when the dielectric constant is 4 exceeded 2.45 GHz for indoor wireless LAN, and for two different radio wave 5.2 GHz (the wave absorber 10) reflected The attenuation is less than 20 dB, and it is difficult to obtain sufficient radio wave absorption characteristics. In particular, the second transparent resin layer 12 is set to thickness T ₁₂ is 13 mm, it is preferable dielectric constant is set to 2.73.

Next, the conductive layer 3 will be described. The surface resistance value is set to 25Ω / □ or less, the lower limit is more preferably 5Ω / □ or more in relation to the light transmittance, and the upper limit is more preferably 10Ω / □. □ Below. If the surface resistance exceeds 25Ω / □, the transmission attenuation (not shown) for the two types of radio waves for indoor wireless LAN, 2.45 GHz and 5.2 GHz (not shown) is less than 20 dB, and sufficient radio wave absorption It becomes difficult to obtain characteristics.
The material of the conductive layer 3 is preferably made of, for example, an Ag film.

Next, actual measurement results when radio waves are incident on the radio wave absorber 10 described above and the radio wave absorbers of Comparative Examples 1 to 3 described later will be described.
Here, it is a necessary condition that the radio wave absorber satisfies all of the following (a), (b) and (c).
(A) Radio wave absorption characteristics A return loss of 20 dB or more is shown for TM waves of 2.45 GHz and 5.2 GHz incident at an incident angle of 10 °.
(B) Translucency A test was conducted according to JIS K 7105 “Testing method for optical properties of plastic”, and the translucency was 50% or more.
(C) Nonflammability Satisfies the conditions that can be used as interior materials as defined by the Building Standards Law.

First, as Example 1, the radio wave absorber 10 described above with reference to FIG. 1 is set as follows.
That is, the first and second glass layers 21 and 22 are both made of soda lime, the dielectric constant is 7, and the thickness dimensions T ₂₁ and T ₂₂ are 1.5 mm. In addition, the resistance layer 2 is composed of an indium tin oxide (ITO) film, and the surface resistance value is 200Ω / □. The first and second transparent resin layers 11 and 12 are both made of polycarbonate and have a dielectric constant of 2.73. Further, the thickness dimension T ₁₁ of the first transparent resin layer 11 is set to 7 mm, and the thickness dimension T ₁₂ of the second transparent resin layer 12 is set to 13 mm. The conductive layer 3 is made of an Ag film and has a surface resistance value of 6.6Ω / □.
When a TM wave was incident on the radio wave absorber 10 of Example 1 at an incident angle of 10 °, the result shown in the graph of FIG. 2 was obtained. As shown in FIG. 2, since the return loss is 20 dB or more in the vicinity of frequencies of 2.45 GHz and 5.2 GHz, the radio wave absorption characteristic of the condition (a) is sufficiently satisfied. Furthermore, the radio wave absorber 10 of Example 1 also satisfies the conditions of (b) translucency and (c) nonflammability.

Next, as Comparative Example 1, a radio wave absorber is set as follows.
That is, the radio wave absorber includes a glass layer having a dielectric constant of 7 and a thickness dimension of 1.5 mm, a resistance layer having a surface resistance value of 377Ω / □ made of an ITO film, A glass layer having a ratio of 7 and a thickness of 10 mm, a conductive layer made of an Ag film and having a surface resistance of 6.6 Ω / □, a glass layer having a dielectric constant of 7 and a thickness of 1.5 mm, The three glass layers are made of soda lime.
The radio wave absorber of Comparative Example 1 satisfies the conditions of (b) translucency and (c) nonflammability.
However, when a TM wave is incident on this radio wave absorber at an incident angle of 10 °, the result shown in the graph of FIG. 3 is obtained, and the return loss becomes 20 dB or more near the frequency of 2.45 GHz. However, in the vicinity of 5.2 GHz, the return loss is almost zero. Therefore, since the condition (a) radio wave absorption characteristics are not satisfied, the radio wave absorber of Comparative Example 1 is inappropriate.

Next, as Comparative Example 2, a radio wave absorber is set as follows.
In other words, the radio wave absorber of Comparative Example 2 is a λ / 4 type radio wave absorber constructed by changing the thickness of the intermediate glass layer to 4.2 mm among the three glass layers of the radio wave absorber of Comparative Example 1. Yes, this radio wave absorber satisfies the conditions of (b) translucency and (c) nonflammability.
However, when a TM wave is incident on this radio wave absorber at an incident angle of 10 °, the result shown in the graph of FIG. 4 is obtained, and the return loss becomes 20 dB or more near the frequency of 5.2 GHz. However, in the vicinity of 2.45 GHz, the return loss is almost zero. Therefore, since the condition (a) the radio wave absorption characteristic is not satisfied, the radio wave absorber of Comparative Example 2 is inappropriate.

Next, as Comparative Example 3, a radio wave absorber is set as follows.
That is, the radio wave absorber is composed of a glass layer having a dielectric constant of 7 and a thickness of 1.5 mm, a resistance layer having a surface resistance value of 3000Ω / □ made of a SUS film, A glass layer having a ratio of 7 and a thickness of 5 mm, a resistance layer made of an ITO film and having a surface resistance value of 200Ω / □, a glass layer having a dielectric constant of 7 and a thickness of 8 mm, and an Ag film A conductive layer having a surface resistance value of 6.6Ω / □ and a glass layer having a dielectric constant of 7 and a thickness dimension of 1.5 mm are laminated, and the glass layer is entirely made of soda lime.
The radio wave absorber of Comparative Example 3 satisfies the conditions of (b) translucency and (c) nonflammability.
However, when a TM wave is incident on this radio wave absorber at an incident angle of 10 °, the result shown in the graph of FIG. 5 is obtained, and the return loss is 10 dB in the vicinity of frequencies of 2.45 GHz and 5.2 GHz. Before and after. Therefore, since the condition (a) radio wave absorption characteristics are not satisfied, the radio wave absorber of Comparative Example 3 is inappropriate.
Although a specific configuration is omitted, a radio wave absorber made of only a glass layer is not suitable because the return loss does not show a peak value in the vicinity of frequencies of 2.45 GHz and 5.2 GHz, and the amount is not sufficient.

From the above measurement results, the radio wave absorber 10 of Example 1 satisfies all the conditions (a), (b), and (c), but the radio wave absorbers of Comparative Examples 1, 2, and 3 Does not meet radio wave absorption characteristics.
Therefore, only the radio wave absorber of the present invention has sufficient translucency and nonflammability, and the return loss is 20 dB or more for two types of radio waves of 2.45 GHz and 5.2 GHz for indoor wireless LAN, It was confirmed that it is suitable as a radio wave absorber installed indoors.

As described above, the radio wave absorber according to the present invention includes the first glass layer 21, the first transparent resin layer 11, the resistance layer 2, the second transparent resin layer 12, Since the conductive layer 3 and the second glass layer 22 are provided, an effective return loss is ensured with respect to two types of radio waves of 2.45 GHz and 5.2 GHz for indoor wireless LAN, and sufficient radio wave absorption is achieved. Has characteristics. Therefore, it is possible to reliably absorb radio waves in the room and to suppress unnecessary reflected waves (unnecessary radio waves) generated by reflections and the like, thereby eliminating problems that cause malfunctions due to radio waves. .
Furthermore, since it has sufficient translucency, even if it installs in a window, light can fully enter the room. Therefore, it can be installed everywhere in the room, and unnecessary radio waves can be sufficiently suppressed. Furthermore, since it has nonflammability defined as usable as an interior material by the Building Standard Law, it is suitable for indoor use.

Further, in order from the side on which the radio wave enters, the first glass layer 21, the first transparent resin layer 11, the resistance layer 2 having a surface resistance value of 150 to 250Ω / □, the second transparent resin layer 12, and the conductive layer Since it has layer 3 and second glass layer 22, it is surely effective return loss for two types of radio waves of 2.45 GHz and 5.2 GHz for indoor wireless LAN, and sufficient radio wave absorption characteristics Have Therefore, it is possible to reliably absorb radio waves in the room and to suppress unnecessary reflected waves (unnecessary radio waves) generated by reflections and the like, thereby eliminating problems that cause malfunctions due to radio waves. .
Furthermore, since it has sufficient translucency, even if it installs in a window, light can fully enter the room. Therefore, it can be installed everywhere in the room, and unnecessary radio waves can be sufficiently suppressed. Furthermore, since it has nonflammability defined as usable as an interior material by the Building Standard Law, it is suitable for indoor use.

Further, the thickness T ₁₁ of the first transparent resin layer 11 is set to 6mm to 9 mm, and the thickness T ₁₂ of the second transparent resin layer 12 is set to 10mm to 13 mm, further, the first and second 2 Since the dielectric constants of the transparent resin layers 11 and 12 are set to 4 or less, the radio wave absorption performance with respect to two types of radio waves of 2.45 GHz and 5.2 GHz is not deteriorated.

  Further, since the first and second transparent resin layers 11 and 12 are made of polycarbonate or acrylic, it is possible to effectively absorb radio waves and to suppress unnecessary reflected waves (unnecessary radio waves) generated by reflection or the like. .

Further, the first and second glass layers 21 and 22 have thickness dimensions T ₂₁ and T ₂₂ set to 1 mm to 2 mm and a dielectric constant set to 5 to 8, so that they are for indoor wireless LAN. With respect to two types of radio waves of 2.45 GHz and 5.2 GHz, it is surely effective return loss and has sufficient radio wave absorption characteristics.
Moreover, it exhibits a sufficient nonflammability effect.

  In addition, since the surface resistance value of the conductive layer 3 is set to 25Ω / □ or less, it is surely an effective transmission attenuation amount for two types of radio waves of 2.45 GHz and 5.2 GHz for indoor wireless LAN, It has sufficient electromagnetic wave absorption characteristics.

Also, because it is used to absorb radio waves for indoor wireless LAN, it efficiently absorbs radio LAN radio waves for personal computers, mobile phones, portable terminals, etc., which have been increasingly used indoors. Can prevent malfunctioning equipment.
Thus, a great effect can be exhibited as a measure for improving the radio wave environment.

It is a section front view showing one embodiment of a wave absorber concerning the present invention. It is a graph which shows the relationship between the frequency of an electromagnetic wave, and a return loss. It is a graph which shows the relationship between the frequency of an electromagnetic wave, and a return loss. It is a graph which shows the relationship between the frequency of an electromagnetic wave, and a return loss. It is a graph which shows the relationship between the frequency of an electromagnetic wave, and a return loss.

2 Resistance layer 3 Conductive layer
10 Electromagnetic wave absorber
11 First transparent resin layer
12 Second transparent resin layer
21 First glass layer
22 Second glass layer T ₁₁ thickness dimension T ₁₂ thickness dimension T ₂₁ thickness dimension T ₂₂ thickness dimension

Claims (5)

In order from the side on which the radio wave enters, the first glass layer (21), the first transparent resin layer (11), the resistance layer (2) having a surface resistance value of 150 to 250Ω / □, and the second transparent resin layer (12), a conductive layer (3), and a second glass layer (22), the thickness dimension (T ₁₁ ) of the first transparent resin layer (11) is set to 6 mm to 9 mm, and The thickness dimension (T ₁₂ ) of the second transparent resin layer (12) is set to 10 mm to 13 mm, and the dielectric constant of the first and second transparent resin layers (11) and (12) is 4 or less. A radio wave absorber that is configured and configured to absorb two types of radio waves . The radio wave absorber according to claim 1, wherein the first and second transparent resin layers (11) and (12) are made of polycarbonate or acrylic . It said first and second glass layer (21) (22) has a thickness dimension (T ₂₁₎ (T ₂₂₎ is set to 1mm to 2 mm, and, according to claim 1 having a dielectric constant is set to 5 to 8 Or the electromagnetic wave absorber of 2. The radio wave absorber according to claim 1, 2 or 3 , wherein the surface resistance value of the conductive layer (3) is set to 25 Ω / □ or less . Telecommunications suction absorbent body according to claim 1, 2, 3 or 4 wherein is used to absorb radio waves for indoor wireless LAN.

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