JP2000068674A - Radio wave absorber - Google Patents

Abstract

(57) [Problem] To provide a glass curtain wall type radio wave absorber which can efficiently absorb radio waves, is excellent in various characteristics, is lightweight, and is easy to construct. A radio wave absorber including a glass layer, a resistance layer, a dielectric layer, and a reflection layer, wherein a glass layer is disposed on the radio wave incidence surface, and the resistance layer is closer to the radio wave incidence side than the reflection layer. Radio wave absorber placed close to

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a radio wave absorber. More specifically, the present invention relates to a radio wave absorber useful as an outer wall material of a high-rise building.

[0002]

2. Description of the Related Art In recent years, television reception problems caused by high-rise buildings have become a major social problem. High-rise buildings use a large amount of steel, and the outer wall is often composed of an assembly of concrete or glass layers and a fire-resistant panel. The received radio waves often cause reception problems.

As one method of preventing the reception failure, the outer wall may be constituted by a radio wave absorber. In a concrete type curtain wall, a ferrite tile, a carbon fiber bundle (JP-A-7-283578), Alternatively, a conductor is held in the conductor housing and a measuring object (Japanese Patent Application No.
No. 0-002172) has been proposed.

[0004]

As a curtain wall composed of an assembly of a glass layer and a refractory panel, only a curtain wall using a ferrite tile has been put to practical use.
Since the weight of the wall is large and the installation of the tile is complicated, there are very few construction examples. The problem to be solved by the present invention is to provide a glass curtain wall type radio wave absorber that is excellent in various characteristics, has small variations, is lightweight, and is easy to construct.

[0005]

The present inventors have conducted intensive studies on a radio wave absorber having a sanity problem, and as a result,
The radio wave absorber having a specific structure has been reached, and the present invention has been reached. That is, the present invention is a radio wave absorber including a glass layer, a resistance layer, a dielectric layer, and a reflection layer, wherein the glass layer is disposed on the radio wave incidence surface, and the resistance layer is more radio wave than the reflection layer. It exists in a radio wave absorber arranged close to the incident side.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail. The radio wave absorber according to the present invention basically comprises a glass layer, a resistance layer, a dielectric layer, and a reflection layer. (1) Glass layer As the glass layer, float glass, heat ray absorbing glass,
Any material such as heat ray reflective glass and high-performance heat ray reflective glass can be used, but float glass or heat ray absorbing glass is preferred from the viewpoint of radio wave absorption performance, and float glass is particularly preferred. The thickness of the glass layer is not particularly limited, but is preferably about 10 to 20 mm from the viewpoint of strength against wind pressure. In addition, the frequency at which the absorption performance is maximized changes depending on the thickness of the glass layer, so if you want to improve the absorption performance at a specific frequency, the thickness of the dielectric or air layer should be adjusted according to the thickness of the glass layer. It is desirable to adjust. Furthermore, when heat ray absorbing glass is used, it has its own resistance component, so it is desirable to adjust the sheet resistance of the resistance layer. (2) Resistance layer The resistance layer may be a layer having a predetermined sheet resistance. As a specific resistance layer, a long object having a predetermined line resistance value is laid out at a predetermined interval, a coating material in which a conductive material is dispersed in a binder is applied on a substrate, What cut | disconnected the base | substrate to arbitrary width | variety and laid at predetermined intervals is used. From the point of radio wave absorption performance, any of these may be used.However, in consideration of the workability when assembling as a curtain wall and the design, a coating material in which a conductive substance is dispersed in a binder can be used as a film or sheet. It is particularly preferable to use the one coated on the substrate.

Examples of the conductive substance include carbon-based materials and metals, but carbon-based materials are preferred in terms of resistance and lightness, and among them, carbon black is particularly preferred in terms of easy mixing. Metal particles such as copper and silver are liable to settle and unevenly disperse in the mixture, and carbon fibers and steel fibers are liable to deflect during coating, and it is difficult to form a uniform sheet resistance. On the other hand, as the binder, resin,
Various materials such as rubber, calcium silicate, cement, clay and the like can be used, but resins are preferred from the viewpoint of cost and ease of handling, and thermosetting resins are particularly preferred from the viewpoint of moldability. It is desirable that the above-mentioned conductive substance and the binder are mixed as uniformly as possible, and a known mixer, a paint shaker or the like is used as the means. Further, in order to improve the mixing uniformity, a solvent may be appropriately added at the time of mixing.

[0008] In order to form a desired resistive layer using the above-mentioned mixture of the conductive material and the binder, a coating method is important. The coating method is not particularly limited, and simple methods such as spray coating and brush coating are also possible.However, since the variation in the coating film thickness tends to be large, it is preferable to use a die coater or a roll coater. However, particularly preferred is a method of coating with a die coater. This die coater method has the advantage that coating can be performed in a closed system and there is no external contamination of the mixture to be coated. In addition, the die coater generally has a wide viscosity range of 1 to 70000 (cps) and can handle from a low viscosity to a high viscosity. Therefore, when changing the resistance value, the viscosity of the mixture can be reduced without worrying about the viscosity. There is an advantage that the composition can be arbitrarily changed and the degree of freedom in selecting the set film thickness is high. If the target value of the sheet resistance of the resistance layer is small, it is necessary to reduce the specific resistivity of the mixture or increase the coating film thickness. There is also a method of laminating substrates having a sheet resistance larger than the value to form a resistance layer. For example, the sheet resistance ZsO
The sheet resistance value Zs when the sheets are stacked is calculated by the following equation.

[0009]

Zs = Zs / n The substrates having sheet resistance values Zs1 and Zs2 are respectively n1
, N2 laminated surface resistance values Zs are calculated by the following equations.

[0010]

## EQU2 ## Zs = Zs1 × Zs2 / (n2 × Zs1 + n1)
× Zs2) As described above, by changing the specific resistivity of the mixture, the thickness of the coating film, and the number of laminated layers, a resistive layer having a desired sheet resistance value can be obtained. (3) Dielectric layer The dielectric layer has a function of adjusting the frequency of the radio wave at which the absorption performance is maximized to a desired value.
Although it can be made of various materials having fire resistance such as gypsum, calcium silicate, pottery, and porcelain, calcium silicate, gypsum, and calcium silicate are particularly preferable in terms of lightness. A reinforcing material such as carbon fiber, steel fiber, glass fiber, or synthetic fiber may be included in the dielectric layer. (4) Reflection Layer The reflection layer substantially totally reflects incident radio waves, and is preferably formed of a metal plate or sheet, a wire mesh, a metal rod, a punching metal, or the like. When the reflection layer is attached to the dielectric layer, the method is not particularly limited, and an adhesive,
Any material such as staples, strings, adhesive tapes and the like can be used, but using a commercially available metal sheet with an adhesive as the reflective layer is economical and convenient. (5) Layer Configuration of Radio Wave Absorber The radio wave absorber according to the present invention includes a glass layer, a resistance layer, a dielectric layer, and a reflection layer. Are arranged closer to the radio wave incident side than the reflection layer. And basically, a combination of a glass layer, a resistance layer, a dielectric layer and a reflection layer from the radio wave incident side,
A combination of a glass layer, a dielectric layer, a resistive layer and a reflective layer,
Although a four-layer structure is formed by a combination of a glass layer, a resistance layer, a reflection layer, and a dielectric layer, an additional layer may be further provided. For example, a predetermined thickness (for example, 10 to 50) is provided between each layer for reasons such as heat insulation, workability, and adjustment of radio wave absorption performance.
0 mm) air layer can also be provided.

The resistance layer can be adjusted anywhere as long as the resistance layer is on the side of the radio wave incident direction with respect to the reflection layer. However, in order to reduce the thickness of the entire curtain wall, it is necessary to arrange the resistance layer as close to the glass layer as possible. desirable. Therefore, the resistance layer
It is preferable to arrange between the glass layer and the dielectric layer or between the dielectric layer and the reflective layer. Note that the resistance layer may be attached to the back surface of the glass layer, but it is not preferable in design that the resistance layer can be seen from the surface of the glass layer, or when there is a reason such as protecting the resistance layer from ultraviolet rays or high temperatures. A second dielectric layer can be provided between the glass layer and the resistance layer. As the material of the second dielectric layer, the same material as that of the dielectric layer can be used, but the fireproof performance is not required, so that the thickness may be minimized.

Further, by arranging an air layer between any of the glass layer, the resistance layer, the dielectric layer and the reflection layer, the radio wave absorption performance can be further improved. For example, between the dielectric layer and the second dielectric layer, 10 to 30 to adjust the frequency of the radio wave at which the absorption performance is maximum to a desired value.
An air layer of about 0 mm is provided, or usually 10 to 200 mm, preferably 30 to 15 mm between the glass layer and the second dielectric layer.
A 0 mm air layer may be provided.

In order to determine the thickness of each layer, it is assumed that the frequency, incident angle, and dielectric constant of the material of each layer to be absorbed are known. Based on these data, first, the thickness of the glass layer or the dielectric layer is determined from the architectural aspects such as strength and fire resistance, and the thickness of the remaining air layer can be obtained by an electric engineering method.

[0014]

EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples. (Example 1) Carbon black (3250 manufactured by Mitsubishi Chemical Corporation)
B), 18 parts by weight of a mixture of a urethane resin and a curing agent (weight ratio: 73.8: 24.6: 1.6),
A coating liquid was prepared by kneading well with a mixer, and this was sent to a die coater by a pump, applied to one side of a polyester film, and dried with hot air to produce two types of 150 mm wide film rolls. One is that the coating thickness is later 6.5μ on average
m, the average sheet resistance was 1150 Ω, and the other was 8.3 μm in average in terms of the coating film thickness, and the average sheet resistance was 850 Ω.

Of these, six films having a sheet resistance of 850 Ω (total sheet resistance is 1) are cut and stacked, and stretched on a 600 × 900 mm, 55 mm-thick silicon plate in a stretching direction of 600 mm side (electric field). Direction). Then, an aluminum sheet with an adhesive was stuck on the entire surface of the calcium silicate plate opposite to the surface where the film was stuck. Further, a glass layer having a thickness of 15 mm is placed with a 24 mm air layer left above the film surface, and is composed of a glass layer-air layer-resistance layer-dielectric layer-reflection layer from the radio wave incident surface as shown in FIG. A measurement sample was used.

Using a large waveguide measurement system, the radio wave absorption performance of this measurement sample was measured by irradiating radio waves from the outside of the glass layer. As shown in FIG.
B was the absorption characteristic. Example 2 Four films having a sheet resistance of 850 Ω described in Example 1 and two sheets having a sheet resistance of 150 Ω (total sheet resistance is 157 Ω) were superposed and cut into 600 × 9 pieces.
It was placed parallel to a stretching direction electric field direction) on a calcium silicate plate having a thickness of 00 mm and a thickness of 25 mm. Then, a 26 mm air layer is opened from the opposite side of the calcium silicate plate where the film is attached, an aluminum plate having a thickness of 3 mm is placed, and a 20 mm air layer is further opened from the film surface, and a glass plate having a thickness of 15 mm is formed. To obtain a measurement sample composed of a glass layer, an air layer, a resistance layer, a dielectric layer, an air layer, and a reflection layer from the radio wave incident surface as shown in FIG. Using a large-sized waveguide measurement system, the radio wave absorption performance of this measurement sample was measured by irradiating radio waves from outside the glass layer. As shown in FIG. 5, the absorption characteristics were up to about 25 dB. . (Example 3) Four films having a sheet resistance value of 850 Ω (total surface resistance is 213 Ω) described in Example 1 were stacked and cut, and the stretching direction was 600 mm on a gypsum board having a size of 600 × 900 mm and a thickness of 10 mm. It was placed parallel to the side (electric field direction). And 20 from the opposite side of the film
A 25 mm thick layer of calcium silicate was placed in the air layer, and an aluminum sheet with an adhesive was stuck on the entire surface opposite to the side facing the gypsum board. Further, a 10 mm air layer is opened from the surface of the gypsum board on which the film is stuck, and the thickness is 15 mm.
mm glass layer, and the glass layer-air layer-second dielectric layer-resistance layer-air layer-
A measurement sample composed of a dielectric layer and a reflective layer was used.

Using a large waveguide measurement system, the radio wave absorption performance of this measurement sample was measured by irradiating radio waves from outside the glass layer. As shown in FIG.
B was the absorption characteristic.

[0018]

According to the present invention, it is possible to provide a glass curtain wall type radio wave absorber which can efficiently absorb radio waves and is excellent in various characteristics. Moreover, the radio wave absorber of the present invention is lightweight and easy to construct.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a configuration of a radio wave absorber according to a first embodiment.

FIG. 2 is a perspective view illustrating a configuration of a radio wave absorber according to a second embodiment.

FIG. 3 is a perspective view illustrating a configuration of a radio wave absorber according to a third embodiment.

FIG. 4 is a diagram illustrating characteristics of a radio wave absorber of the radio wave absorber of the first embodiment.

FIG. 5 is a view showing a radio wave absorber characteristic of the radio wave absorber of Example 2.

FIG. 6 is a view showing a radio wave absorber characteristic of the radio wave absorber of the third embodiment.

Claims (6)

[Claims] 1. A radio wave absorber comprising a glass layer, a resistive layer, a dielectric layer, and a reflective layer, wherein a glass layer is disposed on a radio wave incident surface, and the resistive layer receives a radio wave more than the reflective layer. A radio wave absorber placed close to the side. 2. The radio wave absorber according to claim 1, wherein a resistance layer is disposed between the glass layer and the dielectric layer. 3. The radio wave absorber according to claim 1, wherein a resistance layer is disposed between the dielectric layer and the reflection layer. 4. An air layer is disposed between any one of a glass layer, a resistance layer, a dielectric layer, and a reflection layer.
3. The radio wave absorber of any of 3. 5. The radio wave absorber according to claim 1, wherein the resistance layer contains a carbon-based material. 6. The radio wave absorber according to claim 5, wherein the carbon-based material is obtained by mixing a carbon-based powder with a binder.