Electromagnetic-wave absorber

• US 20050008845A1
• Filed: 01/31/2002
• Published: 01/13/2005
• Est. Priority Date: 01/31/2002
• Status: Abandoned Application

• Current Assignee: Nitto Boseki Company Limited
• Original Assignee: Nitto Boseki Company Limited
• Inventors: Hatanaka, Hideyuki, Ohtsubo, Masato, Arikawa, Sadaaki
• Application Number:
  US10/488,781
• Publication Number:
  US 20050008845A1
• Time in Patent Office: Days
• US Class Current: 428/313.300
• CPC Class Codes: B32B 2262/106 Carbon fibres, e.g. graphite fibres
• CPC Class Codes: B32B 2264/10 Inorganic particles
• CPC Class Codes: B32B 2307/20 having particular electrical or magnetic properties, e.g. piezoelectric
• CPC Class Codes: B32B 3/30 characterised by a layer formed with recesses or projections, e.g. hollows, grooves, protuberances, ribs apertured layer B32B3/266; layer with cavities or internal voids B32B3/26
• CPC Class Codes: B32B 5/00 Layered products characterised by the non- homogeneity or physical structure , i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
• CPC Class Codes: B32B 5/02 characterised by structural features of a fibrous or filamentary layer layer formed of metallic wires B32B15/02; layer formed of natural mineral fibres B32B19/02; layer formed of wood fibres B32B21/02
• CPC Class Codes: H01Q 17/002 using short elongated elements as dissipative material, e.g. metallic threads or flake-like particles
• CPC Class Codes: H01Q 17/008 with a particular shape H01Q17/007 takes precedence
• CPC Class Codes: H05K 9/009 comprising electro-conductive fibres, e.g. metal fibres, carbon fibres, metallised textile fibres, electro-conductive mesh, woven, non-woven mat, fleece, cross-linked
• CPC Class Codes: Y10T 428/24479 including variation in thickness
• CPC Class Codes: Y10T 428/249971 Preformed hollow element-containing
• CPC Class Codes: Y10T 428/249986 Void-containing component contains also a solid fiber or solid particle
• CPC Class Codes: Y10T 428/25 Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles

Abstract

An electromagnetic wave absorber characterized by comprising from 50 to 85% by weight of inorganic hollow material, from 0.01 to 35% by weight of conductive material, from 5 to 47.5% by weight of binder, and from 0.1 to 47.5% by weight of filler. It has a reduced angle dependence of electromagnetic wave absorption and has the property of absorbing electromagnetic waves over a wide range of angles. It further has satisfactory processability and workability.

Claims

1. An electromagnetic wave absorber comprising from 50 to 85% by weight of an inorganic hollow material, from 0.01 to 35% by weight of a conductive material, from 5 to 47.5% by weight of a binder, and from 0.1 to 47.5% by weight of a filler.

2. The electromagnetic wave absorber according to claim 1, wherein the inorganic hollow material comprises at least one member selected from perlite, shirasu balloons, silica balloons, glass beads, and alumina-silica balloons.

3. The electromagnetic wave absorber according to claim 1, wherein the conductive material comprises at least one member selected from a fibrous conductive material, carbon black, and graphite.

4. The electromagnetic wave absorber according to claim 3, wherein the fibrous conductive material comprises at least one member selected from carbon fibers and metal fibers.

5. The electromagnetic wave absorber according to claim 4, wherein a content of the fibrous conductive material is from 0.01 to 2% by weight.

6. The electromagnetic wave absorber according to claim 3, wherein the conductive material is a fibrous conductive material and the fibrous conductive material has a length not larger than five times a thickness of the electromagnetic wave absorber.

7. The electromagnetic wave absorber according to claim 1, wherein the binder comprises at least one member selected from a powder or emulsion of an organic polymeric compound and organic fibers.

8. The electromagnetic wave absorber according to claim 7, wherein a content of the binder is from 5 to 25% by weight.

9. The electromagnetic wave absorber according to claim 1, wherein the binder comprises at least one member selected from curable inorganic compounds or compositions.

10. The electromagnetic wave absorber according to claim 1, wherein the filler comprises at least one member selected from inorganic powders and inorganic fibers.

11. The electromagnetic wave absorber according to claim 1, which has a shape with recesses and protrusions.

12. The electromagnetic wave absorber according to claim 1, which has a side having electromagnetic wave reflecting properties and a side not having electromagnetic wave reflecting properties.

13. A multilayered electromagnetic wave absorber, which comprises a multilayer structure comprising two or more layers of the electromagnetic wave absorber according to claim 1, wherein an amount of the conductive material added to an upper layer is from 0 to 35% by weight and a content of the conductive material in a lower layer is higher than in the upper layer.