JP2002348987A - Electromagnetic wave absorbing foaming body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic wave absorber having high efficiency in a high frequency band used for a radio transmission network of a cellular phone, a PHS, and a computer, and having performance as a building material. SOLUTION: Graphite and ferrite are mixed in a hard foaming resin body used for the building material such as phenol foam, isocyanurate foam, and urethane foam to obtain an electromagnetic wave absorbing foaming body having electromagnetic wave absorptivity, and having performance as the building material. When a mixing quantity of the graphite is set almost constant, a ferrite unmixed material has the highest frequency indicating a peak value of an absorption quantity. A material having high ferrite density, and having high finish density has a low frequency indicating the peak value of the absorption quantity. This electromagnetic wave absorbing foaming body is used by integrating a metalized film 11 into one surface of the electromagnetic wave absorbing foaming body A, integrating a metallic plate 12 into one surface of the electromagnetic wave absorbing foaming body A, and integrating cloth 13 into the other surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rigid foamed resin material having an electromagnetic wave absorbing property for preventing electromagnetic wave interference caused by a portable telephone, a PHS, a wireless network of a computer and the like, and also useful as a building material.

[0002]

2. Description of the Related Art In recent years, in-house computer networks have been accelerated.
N (Wireless-Local-Area-Net
work) has attracted attention because it can be freely set without restrictions on places and offices. Also, with the rapid spread of mobile phones, high-capacity high-speed data communication is becoming more widespread.

However, when wireless systems are introduced in buildings where large buildings such as large cities are in a forest, deterioration of the radio wave transmission environment due to intermixing of radio waves between the systems is inevitable, and the communication speed is reduced. In severe cases, communication is lost. For the purpose of improving it, we perform shielding to prevent invasion and leakage of radio waves from outside,
In addition, it has been proposed as an effective means to provide an electromagnetic wave absorbing material as a measure against internal reflected waves.

[0004]

The main electromagnetic wave absorbers include those obtained by molding and sintering magnetic oxide powders such as ferrite as they are, and those obtained by mixing them in rubber or concrete. Finally, most require special construction methods. Further, the electromagnetic wave absorption peak of a single ferrite is high in the band of 800 MHz or less, but the performance absorption is less than half in the band of 1 GHz or more, and almost any other special ferrite alone shows an absorption peak in the band of 1 GHz or more. Did not.
For example, some rubbers mixed with ferrite include 2
Some show absorption peaks at GHz, but have high density and are extremely expensive, making them impractical for use as building materials.

In other words, frequency bands (1 to 1) used for mobile telephones, PHS, wireless networks of computers, and the like.
9GHz), there are few electromagnetic wave absorbers with high efficiency,
The construction was expensive or restricted.

Further, when considered as a building material, the electromagnetic wave absorber has only its absorption characteristics, and its performance as a building material, such as lightness, heat insulation, sound insulation, sound absorption, fire protection, and design, is required. Since it does not have it, it is necessary to construct it in combination with other building materials.

[0007]

According to the present invention, graphite and ferrite are mixed in a hard foamed resin material mainly used for building materials, thereby having an electromagnetic wave absorbing property.
In particular, an electromagnetic wave absorbing foam having high efficiency at 1 GHz or higher, inexpensive, and having performance as a building material is obtained.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The rigid foam resin used in the present invention is:
It is a resin used as a building material typified by phenol foam, isocyanurate foam, urethane foam and the like.

The shapes of graphite and ferrite used in the present invention are powdery or granular, respectively.

Although the specific gravity of the electromagnetic wave absorbing foam can be variously set, it is generally preferable that the specific gravity be 0.1 to 3.0 in consideration of the performance required as a building material.

The electromagnetic wave absorbing foam can be integrated with various face materials. Examples of the face material include a metal plate, a metal foil, a metal-deposited film, a plywood, a decorative board, a gypsum board, and the like.
It is a material used for construction such as cloth. However, there is a point to be noted when using metal, because metal reflects electromagnetic waves and generates interference. Therefore, when using a metal plate, a metal foil, a metal vapor deposition film and the like, only one side, use the opposite side of the direction of incidence of electromagnetic waves,
This has the advantage that the electromagnetic waves are absorbed in the foam and the remaining electromagnetic waves are reflected by the metal and are absorbed in the foam, so that the efficiency is extremely high.

(Examples) Electromagnetic wave absorbing foam samples 1 to 6 in which graphite and ferrite were mixed in a phenol foam were prepared, and the amount of ferrite mixed, radio wave absorption and frequency were measured (Table 1, FIG. 1). ). The ferrite used is Kawairon Ferrite's MB3 (Mn-Zn) transformer core. Its μ-frequency characteristics are up to 1000 kHz. Graphite, particle size 80
A mesh of ≧ 80% is used, the mixing amount is substantially constant (approximately 50 g), and a phenol foam is a general phenol foam for a building material.
A 20 mm × 200 mm × 9 mm formwork was used.

[Table 1]

As a result, it can be seen that those without ferrite have the highest frequency at which the peak value of the amount of absorption is exhibited, and those with higher ferrite density and higher finished density have lower frequencies at which the peak value of absorption is lower. . In particular,
Those with a maximum absorption frequency of 2.11 GHz have a low ferrite density of 0.133 g / cm ³ and a sample density of 0.5
It is as light as 87 g / cm ³ .

This is presumably because the graphite particles and the ferrite particles are dispersed in the thickness direction in the hard foamed resin, so that the effects of absorption, reflection and absorption are repeated.

Further, since graphite forms an inorganic carbonized layer under high heat, the above-mentioned sample is described in JIS-A
1321 Flame retardancy test method for building interior materials and construction methods "
Table 2 shows the results of the tests based on the test results, and the standards for “quasi-noncombustible materials” were cleared with a margin.

[Table 2]

FIG. 2A shows an electromagnetic wave absorbing foam A in which a metal deposition film 11 is integrated on one side.
(B) a metal plate 12 on one surface of the electromagnetic wave absorbing foam A;
And the cloth 13 is integrated with the other surface. FIG. 3A shows an electromagnetic wave absorbing foam A in which a gypsum board 14 is integrated on one surface and a metal plate 12 is integrated on the other surface, and FIG. The gypsum board 14 is integrated on both sides of the plasterboard.

[0017]

According to the present invention, since graphite and ferrite are mixed in a hard foamed resin body, the efficiency in a high frequency band (1 to 19 GHz) used for a cellular phone or a wireless network of a computer is improved. Use of a mold or the like, which can provide a high electromagnetic wave absorber, a performance as a building material, for example, an electromagnetic wave absorbing foam excellent in lightness, heat insulation, sound insulation, sound absorption, fire resistance, design, etc. By changing the ferrite density, graphite density, and the finished density and thickness of the electromagnetic wave absorbing foam, it can be used as a material that satisfies the complex shape of the building. Compatible absorbing material can be set.Since graphite is mixed, it is possible to obtain an electromagnetic wave absorber with high efficiency in the high frequency band with a small amount of ferrite. Ability is obtained, characterized the like is very inexpensive as an electromagnetic wave absorber, the effect can be obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing the “relationship between reflection loss and frequency due to ferrite + graphite” in the above embodiment.

FIG. 2 is an explanatory view showing an application example in which a face material is integrated with the electromagnetic wave absorbing foam according to the present invention.

FIG. 3 is an explanatory view showing an application example in which a face material is integrated with the electromagnetic wave absorbing foam according to the present invention.

[Explanation of symbols]

 A electromagnetic wave absorbing foam 11 metallized film 12 metal plate 13 cloth 14 gypsum board

Claims (3)

[Claims] An electromagnetic wave absorbing foam comprising at least graphite and ferrite mixed in a hard foamed resin. 2. The electromagnetic wave absorbing foam according to claim 1, wherein a face material is integrated at least on one side. 3. The electromagnetic wave absorbing foam according to claim 2, wherein the one side material is a metal or a material containing a metal.