Radio wave absorbing composition and radio wave absorber

Patent metadata

Field	Value
Publication number	US-12308523-B2
Application number	US-202217666984-A
Country	US
Kind code	B2
Filing date	Feb 8, 2022
Priority date	Aug 9, 2019
Publication date	May 20, 2025
Grant date	May 20, 2025

Abstract

There is provided a radio wave absorbing composition containing a magnetic powder and a binder. There is also provided a radio wave absorber containing a magnetic powder and a binder. The magnetic powder is a powder of a substitution-type hexagonal ferrite subjected to surface treatment with a surface treatment agent, the surface treatment agent is a silicon-based compound, and the binder is an olefin-based resin.

First claim

What is claimed is:

1. A radio wave absorber,
which comprises a radio wave absorber layer comprising:
a magnetic powder; and
a binder,
wherein the magnetic powder is a powder of a substitution-type hexagonal ferrite subjected to surface treatment with a surface treatment agent,
the surface treatment agent is a silicon-based compound, and
the binder is an olefin-based resin, said olefin-based resin being one or more resins selected from the group consisting of polymethylpentene, a cycloolefin resin, and an olefin-based resin containing a maleic acid anhydride unit, and
which comprises the magnetic powder in an amount of 50% by mass or more and 75% by mass or less, with respect to the total mass (100% by mass) of the magnetic powder and the resin, and
which does not comprise a metal layer, the metal layer being a layer containing a metal and substantially reflecting radio waves, wherein “substantially reflecting radio waves” means reflecting 90% or more of incident radio waves in a case where the radio waves are incident on the radio wave absorber layer in a state where the metal layer is laminated on the back surface of the radio wave absorber layer.

2. The radio wave absorber according to claim 1 ,
wherein the substitution-type hexagonal ferrite has a constitution represented by General Formula 1,
AFe (12-x) Al x O 19   General Formula 1

in General Formula 1, A represents one or more kinds of atoms selected from the group consisting of Sr, Ba, Ca, and Pb, and x satisfies 1.50≤x≤8.00.

3. The radio wave absorber according to claim 1 ,
wherein the substitution-type hexagonal ferrite is a substitution-type hexagonal strontium ferrite.

4. The radio wave absorber according to claim 1 ,
wherein the surface treatment agent is a silicon-based compound represented by General Formula 2,
2:(X-L) m —Si—Z 4-m   General Formula 2

in General Formula 2,
X represents a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, an alicyclic group, a heterocyclic group, a hydroxy group, an acrylamide group, a sulfanyl group, an isocyanate group, a thiocyanate group, a ureido group, a cyano group, an acid anhydride group, an azide group, a carboxy group, an acyl group, a thiocarbamoyl group, a phosphate group, a phosphanyl group, a sulfonic acid group, or a sulfamoyl group,
L represents one divalent group or one bond, selected from the group consisting of a single bond, an alkylene group, an alkenylene group, an alkynylene group, an arylene group,—O—, —S—, —NR a —, an ester bond, a thioester bond, an amide bond, a thioamide bond, and a sulfonyl group, or a divalent group or a bond, obtained by combining two or more of these,
R a represents a hydrogen atom or a substituent,
Z represents a hydroxy group, an alkoxy group, or an alkyl group, and
m is an integer in a range of 1 to 3.

5. The radio wave absorber according to claim 4 ,
wherein in General Formula 2, m is 1, and X represents an alkenyl group or a heterocyclic group, or
m is 2 or 3, and a plurality of X's included in General Formula 2 each independently represent an alkenyl group or a heterocyclic group.

6. The radio wave absorber according to claim 4 ,
wherein in General Formula 2, m is 1, and X represents an acyl group, an acrylamide group, or a heterocyclic group, or
m is 2 or 3, and a plurality of X's included in General Formula 2 each independently represent an acyl group, an acrylamide group, or a heterocyclic group,
where the acyl group is a (meth)acryloyl group, and the heterocyclic group is an epoxy group.

7. The radio wave absorber according to claim 4 ,
wherein in General Formula 2, X represents a heterocyclic group, and the heterocyclic group is an epoxy group.

8. The radio wave absorber according to claim 7 ,
wherein in General Formula 2, L includes an alkylene group having 4 to 12 carbon atoms.

Assignees

• Fujifilm Corp

Inventors

• Nakai Yoshihiro
• Hashimoto Hirokazu

Classifications

• H05K9/0083 Primary

  comprising electro-conductive non-fibrous particles embedded in an electrically insulating supporting structure, e.g. powder, flakes, whiskers (H05K9/0086 takes precedence) · CPC title

• H05K9/0075

  Magnetic shielding materials · CPC title

• C08K9/06

  with silicon-containing compounds · CPC title

• C01G49/009

  Compounds containing iron, with or without oxygen or hydrogen, and containing two or more other elements · CPC title

• C01G49/0036

  containing one alkaline earth metal, magnesium or lead · CPC title