Tdk Corporation

Tdk Electronics Company, Limited

Yasuo Hashimoto

Ken Ishino

Yoshikazu Narumiya

Tsutomu Chou

Hiroshi Kurihara

Hiroshi Yui

Taro Miura

Katsuhiko Wakayama

Toshifumi Saitoh

Katuhiko Hayashi

Masahiro Karatsu

Yoshihito Hirai

Nobutaka Misawa

Hiroshi Yamashita

Nobuyuki Ono

Kenichi Ichihara

Yoshiteru Kageyama

Takashi Watanabe

Ken Toyoda

Hiroaki Abe

The object of the present invention is to provide an electromagnetic wave absorbing sheet excellent in permeability in high frequencies and to provide a method for manufacturing the same. The electromagnetic wave absorbing sheet of the present invention comprises insulating layers on the both sides of a magnetic layer. The magnetic layer is formed by densely depositing a large amount of magnetic powder such that the powder undergoes plastic deformation. Each magnetic powder is made to be a composite magnetic material formed of the soft magnetic metal phase consisting of a flaky soft magnetic metal powder and the insulating phase consisting of an insulating film formed on the surface of the soft magnetic metal phase. Additionally, another configuration can be taken in which a conductive layer is arranged on one of the insulating layers arranged on both sides of the magnetic layer, and the conductive layer is covered with an insulating layer.

Composite magnetic material electromagnetic wave absorbing sheet method for manufacturing sheet-like product and method for manufacturing electromagnetic wave absorbing sheet

An electromagnetic wave absorber is provided with a first dielectric material layer (90, 200, 220) having two surfaces, a wave reflection layer (91, 201, 221) laminated on the one surface of the first dielectric material layer, a first resistive layer (92, 202, 222) laminated on the other, opposite, surface of the first dielectric material layer (90, 200, 220), and a second dielectric material layer (95, 205, 225) disposed proximate to the first resistive layer (92, 202, 222) leaving an air space, (94, 204, 224) having a thickness sufficient to determine adjust absorption characteristics for polarized waves, between the second dielectric material layer and the first resistive layer.

Electromagnetic wave absorber

An electromagnetic wave absorber has a pair of electromagnetic wave absorbing plates (10,11) made of ohmic resistance loss material with top portions (10a,11a) and bottom portions (10b,11b), and a common bottom support member (12) for supporting the bottom portions (10b,11b) of the plates (10,11). In assembled state, the top portions (10a,11a) of the plates (10,11) are fixed with each other and the bottom portions (10b,11b) of the plates (10,11) are fixed by the bottom support member (12) so that the plates (10,11) form an wedge shape.

Electromagnetic wave absorber and wave absorption structure

An electromagnetic shielding material comprising a composition consisting of Mn-Zn ferrite powders, conductive carbon powders and organic high molecular weight compounds. The Mn-Zn ferrite powders may be contained in the range between 30 and 70 vol %. The composition has 10.sup.2 to 10.sup.-1 ohm.cm of volume resistivity and exhibits excellent electromagnetic absorbing property. The electromagnetic shielding material can prevent transmission of electromagnetic waves and attenuate refleted waves by absorbing the waves.

Electromagnetic shielding material

A microwave absorber device for a microwave heater having a chamber for cooking with an opening, and a door for closing the opening with a small gap which is a leakage path between the door and the wall of the chamber. The door is provided with a choke cavity at the peripheral portions of the same, the choke cavity having an approximate 1/4 wavelength of length, and an entrance facing the leakage path. The choke cavity is provided with wave absorber which includes ferrite, and/or carbon, at an edge of the entrance or an edge of the cavity. The wave absorber closes also the leakage path. The entrance itself is sealed by dielectric material.

Absorber device for microwave leakage

An electromagnetic shielding material for absorbing electromagnetic energy has been found. The shielding material is flexible and has a thin conductive core with a composite ferrite material deposited around the core. The composite ferrite material is a mixture of ferrite powder and a binder for binding the powder. The conductive core may be formed in the shape of a flat sheet or an elongated textile shape. The binder may be a high molecular compound like plastic. When the core is in a textile shape, the textile covered with the composite ferrite material is woven into a cloth which is sufficiently flexible to form around any desired shape.

Electromagnetic shield

A microwave absorber device for a microwave heater having a main body with an opening and a door for closing said opening with a leakage path between the door and the main body. The absorber device has a choke cavity along a leakage path of the microwave energy between the main body and the door, said choke cavity having an approximate 1/4 wavelength of length, and an entrance facing said leakage path for accepting microwave energy. Said entrance of the choke cavity is closed by a cover plate made of ferro-magnetic material, which is a mixture of ferrite and gum. Preferably, an additional microwave absorber made of ferro-magnetic material which is integral with said cover plate is provided next to the choke cavity. Preferably, the dielectric constant of the material of the cover plate is less than 15. Still, preferably, the ratio of the imaginary part of the complex permeability to the real part of the same of the cover plate material is larger than 0.5.

A composite ferrite cloth having ferro-magnetic property weaved with composite ferrite textile has been found. The composite ferrite textile is the mixture of ferrite powder and the binder for coupling the same. The binder may be a high molecule compound like plastics, or glass with low melting point. The composite textile may be produced either by slicing a composite ferrite sheet attached on a plastics substrate, depositing composite ferrite paint around a core textile similar to the producing process of an electric wire, or just mixing ferrite powder with plastics or glass. The ferrite cloth which is weaved with composite ferrite textile is flexible and has many fields of application.

Composite ferrite textile

The present invention relates to an electromagnetic interference shielding material used for shielding radios and the like from electromagnetic waves emitted from a computer or the like. In the prior art, a zinc flame-sprayed shielding material is applied on the housing of a computer or the like to shield it from electromagnetic waves. The present invention provides an electromagnetic interference shielding material having an improved durability and shield effectiveness (SE) and comprising a ferromagnetic amorphous alloy having a conductivity of 10.sup.2 .OMEGA..sup.-1 .multidot.cm.sup.-1 or more and a permeability of 100 or more at 1 kHz.

Electromagnetic interference shielding material

A popped corn making apparatus used in a microwave oven comprises a bowl having an opening at the upper part and a narrow closed bottom and a substantially conical shape; and a resonator placed at the bottom of said bowl. The electric field resulted by resonance of said resonator under an application of microwave, is applied to grains of corn contained in said bowl to produce a popped corn. It is possible to use a lumped element resonator comprising a one turn coil having a ring shape having an opening which is placed at the bottom of said bowl and which is formed by an inductance provided by said coil and a capacitance provided by said bowl and said grains of corn.

Popped corn making apparatus used in a microwave oven

Electromagnetic wave-absorbing wall comprising ferrimagnetic plates arranged at some intervals in the direction of the electric field of the electromagnetic wave said ferrimagnetic plates being plates of ferrite having the following general formula:

Electromagnetic wave-absorbing wall

A microwave heating oven has a seal located in the path formed by a gap between the oven body and the oven door for preventing microwave leakage. The seal may comprise several seals, and includes a microwave absorber as one of the seals. The microwave absorber consists of a mixture of a powder of magnetic material and an organic high molecular weight compound. The length of the microwave absorber in the direction of propagation of microwave in the path of microwave leakage is an integral multiple of about 1/2.lambda., wherein .lambda. is a wavelength of the microwave in the microwave absorber. Absorption is improved by setting the absorber in a recess in the wall or door of the oven, or by surrounding the absorber by a metal layer except on the surface thereof parallel to the direction of propagation and facing the gap.

Microwave heating oven having seal means for preventing the leakage of

Microwave absorber comprising a mixture of ferrite powder having particle size of less than 1.65 mm and an organic high molecular weight compound.

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Chiba, Japan

Yasuo Hashimoto