JP2006203233A - Electric wave absorber - Google Patents

Electric wave absorber Download PDF

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JP2006203233A
JP2006203233A JP2006056291A JP2006056291A JP2006203233A JP 2006203233 A JP2006203233 A JP 2006203233A JP 2006056291 A JP2006056291 A JP 2006056291A JP 2006056291 A JP2006056291 A JP 2006056291A JP 2006203233 A JP2006203233 A JP 2006203233A
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soft magnetic
wave absorber
particles
complex
organic polymer
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Morihiko Matsumoto
守彦 松本
Shigemori Miyata
恵守 宮田
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Nippon Telegraph and Telephone Corp
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Nippon Telegraph and Telephone Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin electric absorber where metal soft magnetic particles are dispersed into an organic polymer in a high concentration uniformly, a high complex permeability and a high complex dielectric constant are obtained, the electric resistance of surface of the metal soft magnetic particle is increased, and matches in an UHF band. <P>SOLUTION: In the soft magnetic complex body, the metal soft magnetic particle 12, where an electric insulating layer 11 composed of a molecular having an organic group is formed on the surface, is filled into the organic polymer 13 in a high concentration. The soft magnetic complex body is backed with a reflective substance. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、例えばＵＨＦ帯において２０ｄＢ以上の反射減衰量を有する電波吸収体で、厚さを従来のものより薄くすることが可能な電波吸収体に関する。
The present invention relates to a radio wave absorber that has a return loss of, for example, 20 dB or more in the UHF band and can be made thinner than a conventional one.

現在、ＵＨＦ帯で実現されている電波吸収体は、立方晶フェライトの焼結体やその粉砕粒子を樹脂中に分散した複合体である。
これら焼結体や複合体の厚さは６〜８ｍｍと厚く、重いためその適用箇所は電波暗室などに限られていた。またカルボニル鉄粒子を有機高分子中に分散した複合体は、厚さが２ｍｍ程度と上記の立方晶フェライト系に比べ薄いが、この厚さで適用できる周波数範囲が４ＧＨｚ以上の高周波数域に限られていた。ところで、平面波が自由空間から導電体に裏打ちされた物体へ垂直入射した時の反射減衰量Гは下記の[数１]により表現できる。 Currently, the radio wave absorber realized in the UHF band is a composite in which a sintered body of cubic ferrite and pulverized particles thereof are dispersed in a resin.
Since the thickness of these sintered bodies and composites is as thick as 6 to 8 mm and is heavy, its application location is limited to an anechoic chamber. The composite in which carbonyl iron particles are dispersed in an organic polymer has a thickness of about 2 mm, which is thinner than the above cubic ferrite system, but the frequency range applicable at this thickness is limited to a high frequency range of 4 GHz or more. It was done. By the way, the return loss Γ when a plane wave is perpendicularly incident on an object backed by a conductor from free space can be expressed by the following [Equation 1].

[数１]


また、[数１]中の伝搬定数γは以下の通り表わされる。 [Equation 1]


Further, the propagation constant γ in [Equation 1] is expressed as follows.

[数２]

[Equation 2]

つまり、物体の複素透磁率と複素誘電率との比を１に近づけるのが望ましい。さらに、吸収体を薄く設計するためには物体内における電波の減衰を大きくする必要がある。これには物体の伝搬定数の実数部（減衰定数）を大きくすること、すなわち所望の周波数において、物体の複素透磁率、複素誘電率を大きくする必要がある。  That is, it is desirable to make the ratio of the complex permeability and complex permittivity of an object close to 1. Furthermore, in order to design the absorber thin, it is necessary to increase the attenuation of radio waves in the object. For this purpose, it is necessary to increase the real part (attenuation constant) of the propagation constant of the object, that is, to increase the complex permeability and complex permittivity of the object at a desired frequency.

現状ではＵＨＦ帯用の電波吸収体に立方晶フェライトが用いられている。この物質の複素透磁率は、図７に示すように、スネーク（Ｓｎｏｅｋ）の限界に従い、周波数の増加とともに減少する（強磁性体の物理、近角聡信、掌華房、１９９１）。また複素誘電率は周波数に依存せず一定値を示す。
従って、この系を吸収体に用いたときの整合厚さは６〜８ｍｍとほぼ一定である。
一方、カルボニル鉄など金属軟磁性体の複素透磁率のＵＨＦ帯における周波数存在性は、図７に示すように、スネーク（Ｓｎｏｅｋ）の限界には従わず、主に表皮効果に基づく挙動を示す。したがって、サイズの小さい粒子（３〜４μｍ）を用いることで、立方晶フェライトよりも複素透磁率の限界線を高周波数側に伸ばすことができ、吸収体の整合厚さも２ｍｍ程度となっている。 At present, cubic ferrite is used as a radio wave absorber for the UHF band. As shown in FIG. 7, the complex permeability of this material decreases with increasing frequency according to the limit of Snoke (physics of ferromagnet, near-angle shinnobu, palm flower chamber, 1991). Further, the complex dielectric constant shows a constant value without depending on the frequency.
Therefore, when this system is used for the absorber, the matching thickness is almost constant at 6 to 8 mm.
On the other hand, the frequency existence in the UHF band of the complex magnetic permeability of a metal soft magnetic material such as carbonyl iron does not follow the limit of Snake, and exhibits a behavior mainly based on the skin effect as shown in FIG. Therefore, by using small-sized particles (3 to 4 μm), it is possible to extend the limit line of the complex permeability to the higher frequency side than the cubic ferrite, and the matching thickness of the absorber is about 2 mm.

カルボニル鉄は金属であるため、粒子の集合体がバルク内まで磁化させるには、粒子を有機高分子中へ分散させ、粒子間を流れる渦電流を防ぐ構造にするのが普通である。完全球形粒子が有機高分子中に均一分散した軟磁性複合体の複素透磁率を検討してみる。  Since carbonyl iron is a metal, in order for the aggregate of particles to be magnetized into the bulk, it is usual to disperse the particles in an organic polymer and prevent the eddy current flowing between the particles. Let us examine the complex permeability of a soft magnetic composite in which perfect spherical particles are uniformly dispersed in an organic polymer.

図８に示すような磁性粒子１，２間に有機高分子相が介在する構造を単位構造とする時、図中の点線で囲まれた円筒形の領域の磁気抵抗Ｒｍは[数３]で近似的に表現される。  When the structure in which the organic polymer phase is interposed between the magnetic particles 1 and 2 as shown in FIG. 8 is used as a unit structure, the magnetoresistance Rm of the cylindrical region surrounded by the dotted line in the figure is [Equation 3] Expressed approximately.

[数３]

[Equation 3]

ここでＲは粒子の半径、ｄは粒子間平均距離、μA は粒子自身の複素透磁率、μB は有機高分子の複素透磁率である。（式中のμをεにすれば磁気抵抗の逆数Ｒｍ-1は電気容量Ｃになる。）この式から磁気抵抗を小さくする（複素透磁率を大きくする）には、粒子間平均距離ｄを小さくすること、すなわち粒子充填率を大きくすることと、粒子や有機高分子の複素透磁率を大きくすることが有効であるといえる。電気容量を大きくする（複素誘電率を大きくする）のも同様で、粒子充填率を大きくすることと、粒子や有機高分子の複素誘電率を大きくすることが有効である。軟磁性複合体の複素透磁率μは以下の[数４]で表わせる。 Here, R is the particle radius, d is the average distance between particles, μ A is the complex permeability of the particle itself, and μ B is the complex permeability of the organic polymer. (If μ in the equation is set to ε, the reciprocal Rm −1 of the magnetic resistance becomes the electric capacity C.) To reduce the magnetic resistance (increase the complex permeability) from this equation, the average interparticle distance d is set to It can be said that it is effective to reduce the size, that is, to increase the particle filling rate and to increase the complex permeability of particles and organic polymers. Similarly, increasing the electric capacity (increasing the complex dielectric constant) is effective in increasing the particle packing ratio and increasing the complex dielectric constant of the particles and the organic polymer. The complex permeability μ of the soft magnetic composite can be expressed by the following [Equation 4].

[数４]

[Equation 4]

[数４]中の１／ＲｍをＣにすれば複合体の複素誘電率εについての式となる。ところで、現状のカルボニル鉄系吸収体は粒子の充填率が小さいため、その軟磁性複合体の複素透磁率、複素誘電率は小さく、１ＧＨｚの値が比透磁率値で約５．５以下、比誘電率値で約２２以下である。よって吸収体として整合する周波数は４ＧＨｚ以上の高周波数に限られている。そこでカルボニル鉄粒子の充填率を増大させようとすると、有機高分子中における粒子の均一分散がすすまず、強度ある複合体の成形はむずかしい。また仮に成形できても、金属粒子同士の接触により大きく誘電性を生じてしまう。これにより物体の複素誘電率、特に虚数部が必要以上に大きくなり、上述したとおり物体のインピーダンス値と自由空間のそれとの間に大きなずれを生じ、いずれの厚さにおいても入射電波はほとんど反射し、吸収体の設計は不可能になる。  If 1 / Rm in [Equation 4] is C, the complex dielectric constant ε of the composite is obtained. By the way, since the current carbonyl iron-based absorber has a small particle filling rate, the soft magnetic composite has a low complex permeability and complex permittivity, and a value of 1 GHz is about 5.5 or less in terms of relative permeability. The dielectric constant value is about 22 or less. Therefore, the frequency matched as the absorber is limited to a high frequency of 4 GHz or more. Therefore, if an attempt is made to increase the packing rate of carbonyl iron particles, uniform dispersion of the particles in the organic polymer does not proceed, and it is difficult to form a strong composite. Moreover, even if it can be formed, a large dielectric property is generated by contact between metal particles. As a result, the complex permittivity of the object, especially the imaginary part, becomes larger than necessary, causing a large deviation between the impedance value of the object and that in free space, and almost no incident radio waves are reflected at any thickness. The design of the absorber becomes impossible.

図９にカルボニル鉄粒子を５７．５ｖｏｌ％充填させた複合体（粒子に表面処理をしていない系としては最高の充填率）のさまざまな厚さにおける吸収体の反射減衰量を周波数の関数で表わす。いずれの厚さにおいても吸収ピークが認められない。そこでこの系の複素透磁率値（実験値）を[数１]に入力し、２ＧＨｚにおいて２ｍｍで整合する吸収体の複素誘電率値の範囲を図１０に示す。これによると、反射減衰量を例えば２０ｄＢ以上にするには比誘電率虚数部の値を少なくとも７程度以下にする必要がある。この系の２ＧＨｚにおける比透電率虚数部の実験値は２０で（図３参照）２０ｄＢ以上の反射減衰量を得ることはできないことがわかる。
Fig. 9 shows the return loss of the absorber as a function of frequency at various thicknesses of a composite filled with 57.5 vol% of carbonyl iron particles (the highest packing ratio for a system in which the particles are not surface-treated). Represent. No absorption peak is observed at any thickness. Therefore, the complex permeability value (experimental value) of this system is input to [Equation 1], and the range of the complex permittivity value of the absorber that matches at 2 mm at 2 GHz is shown in FIG. According to this, in order to make the return loss 20 dB or more, for example, the value of the relative dielectric constant imaginary part needs to be at least about 7 or less. It can be seen that the experimental value of the imaginary part of relative permeability at 2 GHz of this system is 20 (see FIG. 3), and it is not possible to obtain a return loss of 20 dB or more.

本発明はこのような現状に鑑みてなされたものであり、その目的はカルボニル鉄などの金属軟磁性体粒子表面に有機基を含む電気的に絶縁性の分子からなる層を設けることで、この粒子を有機高分子中に高密度に均一分散させ、高複素透磁率、高複素誘電率を得ると同時に、金属軟磁性体粒子表面の電気抵抗を大きくし、ＵＨＦ帯域において整合する従来よりも薄い電波吸収体を提供することにある。
The present invention has been made in view of such a situation, and the object thereof is to provide a layer made of electrically insulating molecules containing an organic group on the surface of a metal soft magnetic particle such as carbonyl iron. Particles are uniformly dispersed in an organic polymer at high density to obtain high complex permeability and high complex permittivity, and at the same time, increase the electric resistance of the metal soft magnetic particle surface, making it thinner than the conventional matching in UHF band The object is to provide a radio wave absorber.

上記目的を達成するために本発明の電波吸収体は、有機基を有する分子からなる電気的絶縁層を表面に形成した金属軟磁性体粒子が、有機高分子中に高密度に充填された軟磁性複合体を、反射体で裏打ちして構成することを特徴とするものである。  In order to achieve the above object, the radio wave absorber of the present invention is a soft absorber in which metal soft magnetic particles having an electrically insulating layer made of molecules having an organic group formed on the surface thereof are packed in an organic polymer at a high density. The magnetic composite is constituted by being backed with a reflector.

また本発明の電波吸収体は、有機基を有する分子からなる電気的絶縁層を表面に形成した金属軟磁性体粒子が、有機高分子中に粒子の体積分率で５５ｖｏｌ％以上充填された軟磁性複合体を、反射体で裏打ちして構成することを特徴とするものである。  In the radio wave absorber of the present invention, a soft soft magnetic particle in which an electrically insulating layer made of a molecule having an organic group is formed on the surface is filled in an organic polymer with a volume fraction of 55 vol% or more. The magnetic composite is constituted by being backed with a reflector.

また本発明の電波吸収体は、前記金属軟磁性体粒子がカルボニル鉄粒子であることを特徴とするものである。
また本発明の電波吸収体は、前記有機基を有する分子がカップリング剤の分子であることを特徴とするものである。また本発明の電波吸収体は、前記カップリング剤がシラン系カップリング剤であることを特徴とするものである。
The radio wave absorber according to the present invention is characterized in that the metal soft magnetic particles are carbonyl iron particles.
The radio wave absorber of the present invention is characterized in that the molecule having an organic group is a molecule of a coupling agent. The radio wave absorber of the present invention is characterized in that the coupling agent is a silane coupling agent.

本発明によれば、カルボニル鉄などの金属軟磁性体粒子表面にカップリング剤分子など有機基を有する分子からなる電気的絶縁層を形成することで、この粒子を有機高分子中に高密度に充填し、高複素透磁率、高複素誘電率の軟磁性複合体を実現でき、同時にカップリング剤分子等の被覆による金属軟磁性体粒子の表面絶縁化により、高充填しても電気抵抗が大きく、特性インピーダンスが整合したＵＨＦ帯域で薄型の電波吸収体を実現できる。
According to the present invention, by forming an electrically insulating layer made of a molecule having an organic group such as a coupling agent molecule on the surface of a metal soft magnetic material particle such as carbonyl iron, the particle is densely incorporated in an organic polymer. Filling can realize a soft magnetic composite with high complex permeability and high complex permittivity, and at the same time, the insulation of the surface of the metal soft magnetic particles by coating with coupling agent molecules, etc. makes the electric resistance large even when filled high A thin wave absorber can be realized in the UHF band in which the characteristic impedance is matched.

以下図面を参照して本発明の実施の形態例を詳細に説明する。図１は本発明の電波吸収体中の軟磁性複合体の内部構造を摸式的に示す。すなわち、本発明の電波吸収体は、カップリング剤の分子等の有機基を有する分子からなる電気的絶縁層１１を表面に形成した金属軟磁性体粒子１２が、有機高分子１３中に高密度に充填された軟磁性複合体を、反射体で裏打ちして構成される。ここで金属軟磁性体粒子１２として、鉄、ニッケル、コバルトなどの磁性を有する金属単体やこれらの元素を少なくとも一種含む合金が適用可能である。また、金属軟磁性体粒子１２の粒径については、金属軟磁性体粒子１２自身の透磁率が立方晶フェライトのそれを上回るような条件を選べば現状の電波吸収体を上回る特性が期待できる。  Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 schematically shows the internal structure of the soft magnetic composite in the radio wave absorber of the present invention. That is, in the radio wave absorber of the present invention, the metal soft magnetic particles 12 on the surface of which the electrically insulating layer 11 made of molecules having an organic group such as a coupling agent molecule is formed in the organic polymer 13 with a high density. The soft magnetic composite filled in is backed with a reflector. Here, as the metal soft magnetic particles 12, a single metal having magnetism such as iron, nickel, cobalt, or an alloy containing at least one of these elements can be applied. Further, regarding the particle diameter of the metal soft magnetic particles 12, characteristics that exceed the current radio wave absorber can be expected if conditions are selected such that the magnetic permeability of the metal soft magnetic particles 12 themselves exceeds that of cubic ferrite.

ここで、図２のモデル図に示すように、金属軟磁性体粒子１２の透磁率値が表皮効果だけで決まると仮定し、半径Ｒの球形粒子１２が表面から表皮深さδまで磁化された時に、球形粒子１２中で磁化された体積Ｖは以下の[数５]で表わされる。  Here, as shown in the model diagram of FIG. 2, assuming that the permeability value of the metal soft magnetic particles 12 is determined only by the skin effect, the spherical particles 12 having a radius R were magnetized from the surface to the skin depth δ. Sometimes, the volume V magnetized in the spherical particle 12 is expressed by the following [Equation 5].




[数５]


なお、表皮深さδは粒子の比抵抗ρ、透磁率μならびに周波数ｆから下式で表わされる（強磁性体の物理、近角聡信、掌華房、１９９１）。


[Equation 5]


The skin depth δ is expressed by the following equation from the specific resistance ρ of the particles, the magnetic permeability μ and the frequency f (physical properties of ferromagnet, near-angle shinnobu, palm flower bun, 1991).

[数６]

[Equation 6]

[数７]

[Equation 7]

１ＧＨｚにおける立方晶フェライトの比透磁率値は約６である（磁性体ハンドブック、朝倉書店、１９９３）。この値を金属軟磁性体、たとえば鉄（比抵抗１×１０-7Ωｍ、比透磁率５００；磁性体ハンドブック、朝倉書店、１９９３）が上回るための条件は、上述の[数５]〜[数７]から粒子半径Ｒ＜３０μｍと算出される。本実施形態例で用いる金属軟磁性体粒子はカルボニル鉄粒子で、この種類の鉄粒子は通常、半径５μｍ以下である。したがって算出された条件を十分満足する。 The relative permeability value of cubic ferrite at 1 GHz is about 6 (Magnetic Handbook, Asakura Shoten, 1993). Conditions for the metal soft magnetic material, for example, iron (specific resistance 1 × 10 −7 Ωm, relative magnetic permeability 500; magnetic material handbook, Asakura Shoten, 1993) to exceed this value are the above [Equation 5] to [Equation 5] 7], the particle radius R <30 μm is calculated. The metal soft magnetic particles used in this embodiment are carbonyl iron particles, and this type of iron particles usually has a radius of 5 μm or less. Therefore, the calculated condition is sufficiently satisfied.

さて本発明の吸収体で用いる軟磁性複合体の特徴は、金属軟磁性体粒子１２の表面へ例えばカップリング剤の分子からなる電気的絶縁層１１を形成したことにある。これにより金属軟磁性体粒子１２を高充填しても導電性は小さく、誘電率虚数部が必要以上に大きくならない軟磁性複合体を実現できる。またカップリング剤の分子を用いた場合、軟磁性体粒子１２表面へは無機系の疎水基が、一方有機高分子１３へは有機系の親水基がそれぞれ配位した構造となるため、金属粒子と有機高分子との親和性を高めることができる。これにより、金属粒子１２と有機高分子１３との濡れ性は向上し、大量の粒子を充填できる。よって比複素誘電率は従来よりも大きく、充填率５９．０ｖｏｌ％の系で体積１ＧＨｚの比透磁率値が約９、比誘電率値が約４５であった。（従来は［従来の技術］で言及したとおり１ＧＨｚの値が比透磁率値で約５．５以下、比誘電率値で約２２以下）なお電気的絶縁層に用いるカップリング剤は、シラン系カップリング剤、チタネート系カップリング剤、アルミニウム系カップリング剤、リン酸エステル系カップリング剤などが好適に用いられる。  The feature of the soft magnetic composite used in the absorber of the present invention is that an electrically insulating layer 11 made of, for example, a coupling agent molecule is formed on the surface of the metal soft magnetic particles 12. As a result, even if the metal soft magnetic particles 12 are highly filled, a soft magnetic composite can be realized in which the conductivity is small and the imaginary part of the dielectric constant does not become larger than necessary. In addition, when a coupling agent molecule is used, the structure is such that an inorganic hydrophobic group is coordinated to the surface of the soft magnetic particle 12 and an organic hydrophilic group is coordinated to the organic polymer 13. And the affinity of the organic polymer can be increased. Thereby, the wettability of the metal particles 12 and the organic polymer 13 is improved, and a large amount of particles can be filled. Therefore, the relative complex permittivity was larger than before, and the relative permeability value at a volume of 1 GHz was about 9 and the relative permittivity value was about 45 in a system with a filling rate of 59.0 vol%. (In the past, as mentioned in [Prior Art], the value of 1 GHz is about 5.5 or less in terms of relative permeability and about 22 or less in terms of relative permittivity.) A coupling agent, a titanate coupling agent, an aluminum coupling agent, a phosphate ester coupling agent and the like are preferably used.

図３は例えばシラン系カップリング剤で表面処理したカルボニル鉄粒子を、シリコーン中へ分散して得た軟磁性複合体（充填率５７．５ｖｏｌ％）の複素誘電率である。比較として、表面処理していない系もあわせて示す。特に誘電率虚数部に関して、カップリング剤で処理した本発明の系は未処理の系と比較して値が小さく、図１０で示した複素誘電率の条件範囲を満たすことになる。  FIG. 3 shows the complex dielectric constant of a soft magnetic composite (filling rate: 57.5 vol%) obtained by dispersing carbonyl iron particles surface-treated with, for example, a silane coupling agent in silicone. For comparison, a system that has not been surface-treated is also shown. In particular, regarding the imaginary part of dielectric constant, the system of the present invention treated with the coupling agent has a smaller value than the untreated system, and satisfies the condition range of the complex dielectric constant shown in FIG.

図４はカップリング剤により表面処理していないカルボニル鉄粒子を充填した軟磁性複合体（厚さ２ｍｍ）からなる電波吸収体の反射減衰量である。
成形可能な最大の充填量は５７．５ｖｏｌ％であった。充填量５５．０ｖｏｌ％では２０ｄＢ以上の反射減衰量を示すが、さらに充填量を増加すると複素透磁率、複素誘電率が向上し、ピークは低周波数へシフトするが、導電性も増加するため特性インピーダンスに不整合が生じ、体積分率５６．０ｖｏｌ％ではすでにピーク強度が２０ｄＢ以下になる。したがって、表面処理を施さない通常の系ではＵＨＦ帯である３ＧＨｚ以下で整合する吸収体は実現できない。
一方、カップリング剤により表面処理した本発明の電波吸収体は金属軟磁性体粒子１２と有機高分子１３との親和性が向上し５９．０ｖｏｌ％まで充填することができる。 FIG. 4 shows the return loss of a radio wave absorber made of a soft magnetic composite (thickness 2 mm) filled with carbonyl iron particles not surface-treated with a coupling agent.
The maximum filling amount that can be molded was 57.5 vol%. When the filling amount is 55.0 vol%, the reflection attenuation amount is 20 dB or more. However, when the filling amount is further increased, the complex permeability and the complex permittivity are improved and the peak is shifted to a low frequency, but the conductivity is also increased. Impedance mismatch occurs, and the peak intensity is already 20 dB or less at a volume fraction of 56.0 vol%. Therefore, in a normal system not subjected to surface treatment, an absorber that matches at 3 GHz or less which is the UHF band cannot be realized.
On the other hand, the radio wave absorber of the present invention surface-treated with a coupling agent improves the affinity between the metal soft magnetic particles 12 and the organic polymer 13 and can be filled up to 59.0 vol%.

図５はカップリング剤により表面処理したカルボニル鉄粒子を充填した複合体（厚さ２ｍｍ）からなる電波吸収体の反射減衰量である。充填量を増加しても２０ｄＢ以上の吸収強度を維持し、充填量５５．４ｖｏｌ％では２．８ＧＨｚ、充填量５７．８ｖｏｌ％では２．２ＧＨｚ、充填量５９ｖｏｌ％では１．８ＧＨｚまで吸収ピークを低周波数側へシフトする。すなわち、本発明のカップリング剤による処理効果は体積分率約５５．０ｖｏｌ％以上の高充填系で効果を発揮する。  FIG. 5 shows the return loss of a radio wave absorber made of a composite (thickness 2 mm) filled with carbonyl iron particles surface-treated with a coupling agent. Even if the filling amount is increased, the absorption intensity of 20 dB or more is maintained, and the absorption peak reaches 2.8 GHz at the filling amount of 55.4 vol%, 2.2 GHz at the filling amount of 57.8 vol%, and 1.8 GHz at the filling amount of 59 vol%. Shift to the low frequency side. That is, the treatment effect of the coupling agent of the present invention is effective in a high filling system having a volume fraction of about 55.0 vol% or more.

図６は本実施形態例で最大充填量（５９．０ｖｏｌ％）の軟磁性複合体からなる電波吸収体の、さまざまな厚さにおける反射減衰量である。厚さ１．５ｍｍで２．１ＧＨｚ、厚さ２．０ｍｍで１．８ＧＨｚ、厚さ２．５ｍｍで１．５ＧＨｚ、厚さ３．０ｍｍで１．１ＧＨｚにそれぞれ２０ｄＢ以上の吸収ピークを有する。これらの整合厚さは立方晶フェライト系の６〜８ｍｍと比較して十分薄い。  FIG. 6 shows the return loss at various thicknesses of the radio wave absorber made of the soft magnetic composite with the maximum filling amount (59.0 vol%) in this embodiment. It has an absorption peak of 20 dB or more at 2.1 GHz at a thickness of 1.5 mm, 1.8 GHz at a thickness of 2.0 mm, 1.5 GHz at a thickness of 2.5 mm, and 1.1 GHz at a thickness of 3.0 mm. These matching thicknesses are sufficiently thin compared with 6-8 mm of cubic ferrite system.


本発明の一実施形態例に係る電波吸収体中の軟磁性複合体の内部構造を摸式的に示す説明図である。It is explanatory drawing which shows typically the internal structure of the soft-magnetic composite body in the electromagnetic wave absorber which concerns on the example of 1 embodiment of this invention. 本発明の電波吸収体に用いる粒子径の適用条件を算出する際に用いるモデルの一例を示す説明図である。It is explanatory drawing which shows an example of the model used when calculating the application conditions of the particle diameter used for the electromagnetic wave absorber of this invention. 本発明の電波吸収体中の充填粒子がカップリング剤により処理された軟磁性複合体と処理がなされていない軟磁性複合体との複素誘電率を比較した例を示す特性図である。It is a characteristic view which shows the example which compared the complex dielectric constant of the soft-magnetic composite body by which the filling particle in the electromagnetic wave absorber of this invention was processed with the coupling agent, and the soft magnetic composite body which is not processed. 充填粒子がカップリング剤により処理されていない軟磁性複合体からなる電波吸収体のさまざまな充填量における反射減衰量を示す特性図である。It is a characteristic view which shows the return loss amount in various filling amount of the electromagnetic wave absorber which consists of a soft-magnetic composite body by which the filling particle is not processed with the coupling agent. 本発明の充填粒子がカップリング剤により処理された軟磁性複合体からなる電波吸収体のさまざまな充填量における反射減衰量の一例を示す特性図である。It is a characteristic view which shows an example of the return loss amount in the various filling amount of the electromagnetic wave absorber which consists of a soft-magnetic composite material by which the filling particle | grains of this invention were processed with the coupling agent. 本発明の電波吸収体（複合体の粒子充填量５９．０ｖｏｌ％）のさまざまな厚さにおける反射減衰量の一例を示す特性図である。It is a characteristic view which shows an example of the return loss amount in various thickness of the electromagnetic wave absorber (particle filling amount of a composite_body | complex 59.0 vol%) of this invention. スネーク（Ｓｎｏｅｋ）の限界、ならびにカルボニル鉄粒子が有機高分子中に分散した材料の複素透磁率の周波数特性を示す特性図である。It is a characteristic figure which shows the frequency characteristic of the limit of a snake (Snoek) and the complex permeability of the material which the carbonyl iron particle disperse | distributed in the organic polymer. 軟磁性粒子が有機高分子中に分散した複合体の磁気抵抗を算出する際に用いるモデル図である。It is a model figure used when calculating the magnetic resistance of the composite_body | complex in which the soft magnetic particle disperse | distributed in the organic polymer. 充填粒子がカップリング剤により処理されていない軟磁性複合体（粒子充填量５７．５ｖｏｌ％）のさまざまな厚さにおける吸収体の反射減衰量を示す特性図である。It is a characteristic view which shows the return loss amount of the absorber in various thickness of the soft-magnetic composite body (particle filling amount 57.5 vol%) by which the filling particle is not processed with the coupling agent. 図９の軟磁性複合体が２ＧＨｚにおいて吸収体が整合するための複素誘電率の範囲を示す特性図である。FIG. 10 is a characteristic diagram illustrating a range of a complex dielectric constant for the soft magnetic composite of FIG. 9 to match an absorber at 2 GHz.

符号の説明Explanation of symbols

１ 磁性粒子
２ 磁性粒子
１１ 電気的絶縁層
１２ 金属軟磁性体粒子
１３ 有機高分子























1 Magnetic Particle 2 Magnetic Particle 11 Electrical Insulating Layer 12 Metal Soft Magnetic Particle 13 Organic Polymer























Claims (3)

カップリング剤の分子からなる電気的絶縁層を表面に形成した金属軟磁性体粒子が、有機高分子中に粒子の体積分率で５５ｖｏｌ％以上充填された軟磁性複合体を、反射体で裏打ちして構成され、
前記軟磁性複合体は、複素誘電率の虚数部値が７以下となる程度に、前記カップリング剤によって前記金属軟磁性体粒子にカップリング処理を施した後に有機高分子中に充填して生成されることを特徴とする電波吸収体。 A soft magnetic composite in which an electric insulating layer made of a coupling agent molecule is formed on the surface and a volume fraction of the particle filled in an organic polymer is 55 vol% or more is backed with a reflector. Configured,
The soft magnetic composite is formed by coupling the metal soft magnetic particles with the coupling agent to the extent that the imaginary part value of the complex dielectric constant is 7 or less, and then filling the organic soft polymer into the organic polymer. An electromagnetic wave absorber characterized by being made. 前記吸収体の厚さが１．５ｍｍ〜３．０ｍｍであることを特徴とする請求項１記載の電波吸収体。   The radio wave absorber according to claim 1, wherein the absorber has a thickness of 1.5 mm to 3.0 mm. ＵＨＦ帯域で２０ｄＢ以上の反射減衰量を有することを特徴とする請求項１又は２記載の電波吸収体。

3. The radio wave absorber according to claim 1, wherein the electromagnetic wave absorber has a return loss of 20 dB or more in the UHF band.

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102627946A (en) * 2012-03-20 2012-08-08 天津大学 SnO2 coated carbonyl iron powder composite material, preparation method thereof and application thereof
JP2015050360A (en) * 2013-09-03 2015-03-16 山陽特殊製鋼株式会社 Insulative coated powder for magnetic member

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102627946A (en) * 2012-03-20 2012-08-08 天津大学 SnO2 coated carbonyl iron powder composite material, preparation method thereof and application thereof
JP2015050360A (en) * 2013-09-03 2015-03-16 山陽特殊製鋼株式会社 Insulative coated powder for magnetic member

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