Electromagnetic Interference Suppressor, Antenna Device and Electronic Information Transmitting Apparatus

• US 20070252771A1
• Filed: 12/05/2005
• Published: 11/01/2007
• Est. Priority Date: 12/03/2004
• Status: Active Grant

• Current Assignee: Nitta Corporation
• Original Assignee: Nitta Corporation
• Inventors: Yoshida, Takahiko, Sato, Shinichi, Kiyohara, Yoshiharu, Go, Haruhide, Maezawa, Makoto
• Granted Patent: US 7,561,114 B2
• Time in Patent Office: Days
• US Class Current: 343/841
• CPC Class Codes: G06K 19/07771 the record carrier comprising means for minimising adverse effects on the data communication capability of the record carrier, e.g. minimising Eddy currents induced in a proximate metal or otherwise electromagnetically interfering object
• CPC Class Codes: H01F 1/0027 Thick magnetic films forming thick magnetic films H01F41/16
• CPC Class Codes: H01F 1/28 dispersed or suspended in a bonding agent
• CPC Class Codes: H01F 17/0006 Printed inductances printed coils for dynamo-electric machines H02K3/26; printed circuits H05K
• CPC Class Codes: H01F 41/16 the magnetic material being applied in the form of particles, e.g. by serigraphy , to form thick magnetic films or precursors therefor H01F41/18 -H01F41/24 take precedence
• CPC Class Codes: H01Q 1/52 Means for reducing coupling between antennas; Means for reducing coupling between an antenna and another structure absorbing means H01Q17/00
• CPC Class Codes: H01Q 17/00 Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems
• CPC Class Codes: H05K 9/0083 comprising electro-conductive non-fibrous particles embedded in an electrically insulating supporting structure, e.g. powder, flakes, whiskers H05K9/0086 takes precedence
• CPC Class Codes: Y10T 428/31663 As siloxane, silicone or silane

Abstract

An electromagnetic interference suppressor of substantially unpressurized sheet form is obtained by applying and drying a magnetic paint, and comprises 30 to 80% by volume of soft magnetic powder and 20 to 70% by volume of a binder. The binder is an elastomer or a resin that a glass transition point and/or a softening point is 50° C. or more and a storage modulus (E′) is 10⁷ Pa (JIS K 7244-1) or more in a state containing neither solvent nor filler at room temperature. This electromagnetic interference suppressor exerts a superior electromagnetic interference suppressing effect.

Claims

1. An electromagnetic interference suppressor of substantially unpressurized sheet form, which is obtained by applying and drying a magnetic paint, comprising:

30 to 80% by volume of soft magnetic powder and 20 to 70% by volume of a binder,

wherein the binder is an elastomer or a resin having a glass transition point and/or a softening point of 50°

C. or more and having a storage modulus (E′

) of 10⁷ Pa (JIS K 7244-1) or more in a state containing neither solvent nor filler at room temperature.

2. An electromagnetic interference suppressor of substantially unpressurized sheet form, which is obtained by applying and drying a magnetic paint, comprising:

30 to 80% by volume of soft magnetic powder and 20 to 70% by volume of a binder,

wherein the binder is an elastomer or a resin having a glass transition point of room temperature or less, with the glass transition point and the softening point being allowed to satisfy the following equation (I), and having a storage modulus (E′

) of 10⁷ Pa (JIS K 7244-1) or more in a state containing neither solvent nor filler at room temperature.

Equation 4

Softening point−

Glass transition point≧

45°

C. 

 

(I)

3. An electromagnetic interference suppressor of substantially unpressurized sheet form, which is obtained by applying and drying a magnetic paint, comprising:

30 to 80% by volume of soft magnetic powder and 20 to 70% by volume of a binder,

wherein the binder comprises 30 to 80% by weight of an elastomer or a resin having a glass transition point of room temperature or more, and 20 to 70% by weight of an elastomer or a resin having a glass transition point of less than room temperature, the glass transition points being allowed to satisfy the following equation (II), and the elastomer or the resin has a storage modulus (E′

) of 10⁷ Pa (JIS K 7244-1) or more in a state containing neither solvent nor filler at room temperature.

Equation 5

Tg1−

Tg2≧

20°

C. 

 

(II)

Tg1;

glass transition point of room temperature or more

Tg2;

glass transition point of less than room temperature

4. An electromagnetic interference suppressor of substantially unpressurized sheet form, which is obtained by applying and drying a magnetic paint, comprising:

30 to 80% by volume of soft magnetic powder and 20 to 70% by volume of a binder,

wherein the magnetic paint contains a solvent having a boiling point of (room temperature +40°

C.) or more, and the binder is an elastomer or a resin having a glass transition point and/or a softening point of (room temperature +40°

C.) or more and having a storage modulus (E′

) of 10⁷ Pa (JIS K 7244-1) or more in a state containing neither solvent nor filler at room temperature.

5. The electromagnetic interference suppressor according to claim 4, wherein the drying process is a room temperature drying process.

6. The electromagnetic interference suppressor according to claim 4, wherein the drying process is a forceful drying process.

7. The electromagnetic interference suppressor according to claim 4, wherein a ratio of actual specific gravity/theoretical gravity is 0.5 or more.

8. The electromagnetic interference suppressor according to claim 4, wherein a higher fatty acid salt is contained.

9. The electromagnetic interference suppressor according to claim 8, wherein the higher fatty acid salt is zinc stearate.

10. The electromagnetic interference suppressor according to claim 4, wherein the surface of the soft magnetic powder is treated by a coupling agent, or is coated with a resin.

11. The electromagnetic interference suppressor according to claim 4, which has a real part (ε

′

) and an imaginary part (ε

″

) of a complex specific dielectric constant as well as a real part (μ

′

) and an imaginary part (μ

″

) of a complex specific magnetic permeability.

12. The electromagnetic interference suppressor according to claim 4, wherein in a frequency to be used in radio communications in an electromagnetic inductive system, as for the complex specific magnetic permeability, the real part (μ

′

) is set to 30 or more and the imaginary part (μ

″

) is set to 6 or less, and as for the complex specific dielectric constant, the real part (ε

′

) is set to 30 or more and the imaginary part (ε

″

) is set to 500 or less.

13. The electromagnetic interference suppressor according to claim 4, wherein in a frequency range of 50 MHz to 1 GHz, as for the complex specific magnetic permeability, the real part (μ

′

) is set to 7 or more or the imaginary part (μ

″

) is set to 5 or more.

14. The electromagnetic interference suppressor according to claim 4, wherein a flame retarder and/or a flame-retardant auxiliary are contained so as to impart a flame resistant property thereto.

15. The electromagnetic interference suppressor according to claim 4, wherein an adhesion agent layer or a bonding agent layer attached to at least one of the surfaces thereof.

16. The electromagnetic interference suppressor according to claim 4, which has a thermal conductive property.

17. A magnetic shield sheet comprising:

a conductive reflection layer; and

a magnetic layer comprising the electromagnetic interference suppressor according to claim 4, and provided on at least one surface of the conductive reflection layer,

wherein a magnetic shield property in a range of 10 MHz to 1 GHz, obtained by a KEC method or an Advantest method, is set to 20 dB or more.

18. An antenna device comprising:

an antenna element having a resonance frequency that is matched with a frequency to be used for radio communications; and

the electromagnetic interference suppressor according to claim 4, which is interposed between the antenna element and a communication disturbing member.

19. The antenna device according to claim 18, wherein the communication disturbing member is a metal member.

20. An electronic information transmitting apparatus equipped with the antenna device according to claim 18.