Development of radio wave absorbing new material in a paper-form

Mar. 5, 2004

Development of radio wave absorbing new material in a paper-form

Toray Industries, Inc. developed a new paper-form material that can absorb high frequency radio waves used for wireless LAN and collision warning/avoidance radar systems, etc. using the resonance phenomenon of special conductive fibers, providing a leap in efficiency of 10 to 100 times over current radio wave absorbers (carbon powder dispersing material) for the first time in the world.

This new material can be developed for a broad range of applications to improve the radio wave environment. For example, it is expected to be used in the future to improve wireless LAN communications in the office, or as a material for floors, walls, or partitions that absorb and shield unwanted radio waves to prevent malfunction in precision instruments in aircraft, trains and medical facilities, and to improve electromagnetic compatibility in intelligent transfer systems (ITS) and all types of telecommunications devices and systems.

This material has the special characteristics of being thin and light, and can be processed in a variety of shapes, and has excellent processing characteristics in resin impregnation, embossing and cardboard. Furthermore it can be combined with other functional materials to provide added functions such as fire retardant, heat resistance, chemical resistance and weather resistance, and designs such as color and print can be added.

The first development stage is to apply it for use in a radio wave absorber for anechoic rooms and sales of that will start in April this year.

Application for a radio wave absorber


radio wave absorbing new material		cardboard

a radio wave absorber (wedge type)		cardboard sheets (for storage of transportation)

Toray observed the unique behavior of high frequency radio waves during micro dispersion of certain extra fine conductive fibers and has analyzed its characteristics. The result is that, for the thin paper-form material, by achieving optimum control of the dispersion, the company has discovered that the dielectric constant can be adjusted dynamically from a range of low frequency radio waves to a range of high frequency radio waves. This adjustment uses a mechanism that is completely different from existing products, the resonance phenomenon of special conductive fibers. For that reason the radio wave absorption efficiency does not decline even for the range of high frequency radio waves but is maintained at a high level.

The elucidation of the radio wave characteristics of this material and the application to radio wave absorption and shielding were a result of research and development through industry-university collaboration with Associate Professor Kenichi Hatakeyama of Himeji Institute of Technology (Graduate School of Engineering, Electrical, Electronic and Computer Engineering). This new material was born of the fusion of excellent advanced materials, manufacturing technology and academic research.

Currently based on advances towards a wireless ubiquitous network society, a variety of radio waves have started to be used in offices, medical facilities, and public transportation. However, the use of those radio waves has been a cause of malfunctions, and radio wave interference is a concern so that use is limited in aircraft, trains and medical facilities. On the other hand, radio waves used for telecommunications, along with high density of the information transfer volume, is widening greatly from the range of low frequency radio waves used by television and radio (VHF and UHF) to the range of high frequency radio waves (microwave and milliwave). However, in past products with high frequencies of 1GHz (10⁹ hertz) or more the radio wave absorption efficiency degraded (the radio wave absorption index, dielectric constant) and the range of application was limited. Therefore, a new material with excellent radio wave absorption efficiency in the high frequency radio wave range has been sought.

Toray will take advantage of this new paper-form radio wave absorber material to actively develop and create products and pioneer markets for all types of products that the meet increasing demand for measures to deal with the future radio wave flooded era.

The details of the radio wave absorber for anechoic rooms are described below.

1. Product specifications:

·	It is a hollow radio wave absorber using cardboard sheets with the core of the new material in a sphere of three-dimensional shaped pyramids or wedges.
·	It has a fireproof 1st grade classification and UL94 V-0 equivalent incombustibility (in the spherical portion)

2. Product characteristics:

·	- High radio wave absorption. It works with high frequencies. (It works from the range of low radio frequencies of radio and television radio waves to the range of high radio frequencies of cell phones and wireless networks. It can be used in combination with ferrite sintered bodies.)
·	Extremely light (Less than 1/4 of current materials; 150 grams for a 30cm tall wedge)
·	It can be folded into a compact shape for storage of transportation. (It can be folded to less than 1/25 its volume)
·	It can be easily assembled at the site of the anechoic room facility.

3. Sales: First fiscal year: 100 million yen, after 5 years: 1 billion yen

4. Sales channel and start up:
Sales will commence in April this year via Tohoku Chemical Industries, Ltd. (Head Office: Shinagawa-ku, Tokyo; President Yoshiyuki Miyatake), a manufacturer and distributor of radio wave absorbers.

5. Patents: Seven related patents have been applied for.

* Anechoic rooms and current radio wave absorbers:
Anechoic rooms are facilities to evaluate radio wave noise generated by various telecommunications devices. The radio wave absorbers are attached to the walls of the anechoic rooms to create a space where radio waves do not echo. Existing radio wave absorbers have heavy and bulky structures, and so have the problem of being expensive to transport, store and construct. Furthermore the base material of plastic foam has the potential to be flammable during high power irradiation tests and improvements in inflammability have been sought.

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