Electromagnetic wave absorber and film forming paste

Patent metadata

Field	Value
Publication number	US-9806427-B2
Application number	US-201514957235-A
Country	US
Kind code	B2
Filing date	Dec 2, 2015
Priority date	Dec 3, 2014
Publication date	Oct 31, 2017
Grant date	Oct 31, 2017

Abstract

A radio wave absorber provided with a radio wave absorbing film formed on a substrate, the radio wave absorber being capable of absorbing radio waves over a broad frequency band and exhibiting superior radio wave absorbing properties even with a radio wave absorbing film thinner than 1 mm. A film forming paste suitable for forming a radio wave absorbing film that is provided in the radio wave absorber. In a radio wave absorber provided with a radio wave absorbing film formed on a substrate, a particular epsilon-type iron oxide is employed in the radio wave absorbing film and relative permittivity of the radio wave absorbing film is set to 6.5 to 65.

First claim

What is claimed is:

1. A radio wave absorber comprising a radio wave absorbing film formed on a substrate, wherein:
the radio wave absorber has a peak radio wave absorption in a frequency selected from a band of 60-270 GHz;
the radio wave absorbing film comprises an epsilon-type iron oxide and a carbon nanotube;
the epsilon-type iron oxide is at least one selected from the group consisting of an ε-Fe 2 O 3 crystal and a crystal in which a crystalline structure and space group are the same as those of the ε-Fe 2 O 3 crystal, wherein a portion of Fe sites in the ε-Fe 2 O 3 crystal is substituted by an element M other than Fe, wherein the crystal is represented by a formula ε-M x Fe 2-x O 3 wherein x is greater than 0 and less than 2;
a relative permittivity of the radio wave absorbing film is 6.5 to 65; and
the content of the epsilon-type iron oxide relative to total amount of the radio wave absorbing film is at least 30 mass %,
wherein an amount of the carbon nanotube relative to the total amount of the radio wave absorbing film is in a range from 1 to 10% by mass.

2. The radio wave absorber according to claim 1 , wherein the substrate comprises a conductor.

3. The radio wave absorber according to claim 1 , wherein the substrate is planar.

4. A film forming paste comprising an epsilon-type iron oxide and a carbon nanotube, wherein the epsilon-type iron oxide is at least one selected from the group consisting of an ε-Fe 2 O 3 crystal and a crystal in which a crystalline structure and space group are the same as those of the ε-Fe 2 O 3 crystal, wherein a portion of Fe sites in the ε-Fe 2 O 3 crystal is substituted by an element M other than Fe, wherein the crystal is represented by a formula ε-M x Fe 2-x O 3 wherein x is greater than 0 and less than 2,
wherein the film forming paste is capable of forming a film having a relative permittivity of 6.5 to 65, and
wherein the content of the epsilon-type iron oxide relative to total amount of the radio wave absorbing film is at least 30 mass %,
wherein an amount of the carbon nanotube relative to the total amount of the radio wave absorbing film is in a range from 1 to 10% by mass.

5. A film formed using the film forming paste according to claim 4 .

6. The radio wave absorber according to claim 1 , wherein the radio wave absorbing film further comprises a cellulose resin.

7. The radio wave absorber according to claim 1 , wherein the radio wave film comprises dielectric powder having an average particle size of 1 to 100 nm.

8. The film forming paste according to claim 4 , further comprising a cellulose resin.

9. The film forming paste according to claim 4 , comprising dielectric powder having an average particle size of 1 to 100 nm.

Assignees

• Univ Tokyo
• Tokyo Ohka Kogyo Co Ltd

Inventors

• Ohkoshi Shin-Ichi
• Namai Asuka
• YOSHIKIYO Marie
• Ono Takashi

Classifications

• H05K9/0075

  Magnetic shielding materials · CPC title

• C09D5/32

  Radiation-absorbing paints {(protection against X-, gamma- or corpuscular radiation G21F)} · CPC title

• C09C1/24

  Oxides of iron · CPC title

• H01Q17/007 Primary

  with means for controlling the absorption · CPC title

• C01P2004/62

  Submicrometer sized, i.e. from 0.1-1 micrometer · CPC title