JPH10290094A - Electromagnetic-wave absorbing material and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electromagnetic-wave absorbing material by which electromagnetic waves in a wide band from a quasimicrowave band up to a millimeter wave band can be absorbed uniformly by a method wherein an electromagnetic-wave absorption layer is constituted of a binder and of a magnetic-substance powder and the magnetic-substance powder is unevenly distributed inside the electromagnetic-wave absorption layer. SOLUTION: An electromagnetic-wave absorption layer is constituted of an organic binder or of an inorganic binder and of a magnetic-substance powder 2 which uses a ferrite metal oxide magnetic substance combining MnO, ZnO, NiO, MgO, CuO, Li2 O or the like with Fe2 O3 or a metal magnetic substance such as an Fe-Si-Al alloy (Sendust), an Ni-Fe alloy (Permalloy), a Co-Fe alloy or an amorphous alloy comprising an Fe group or a Co group or the like. Then, the magnetic-substance powder 2 is unevenly distributed in the same pattern as a pattern formed on a magnetic sheet 3b composed of circular pattern units, and magnetic-substance unevenly distributed parts 2a are formed inside the electromagnetic-wave absorption layer 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light-weight electromagnetic wave absorbing material which can handle a wide range of frequencies.

[0002]

2. Description of the Related Art Technological innovation for a highly information-oriented society is steadily progressing. Information and communication technology has made tremendous progress, and personal information equipment represented by multimedia,
Similar to that system, the development of communication infrastructure is expected as the next big market.

[0003] As frequency bands used in communication systems, quasi-microwave bands of 1.9 GHz band and 2.45 GHz band, quasi-millimeter wave bands of 19 GHz band, and millimeter wave bands of 60 GHz band have been put into practical use. I am trying to do. Furthermore, in other countries, 900 MHz band and 5.7 GHz band
Bands are also practically used for wireless LAN. The quasi-microwave band is applied to indoor wireless devices of a personal simplified wireless telephone system (PHS) and a medium speed wireless LAN, and the quasi-millimeter wave band and the millimeter wave band are applied to indoor wireless devices of a high-speed wireless LAN. As the demand in each frequency band increases, there are concerns about problems such as mutual interference of electromagnetic waves, interference due to delay dispersion, malfunction, eavesdropping, and the like.

[0004] In particular, in intelligent offices and the like,
Since a large number of communication / information devices are installed, mutual interference of electromagnetic waves, interference due to delay dispersion, malfunction, and the like are likely to occur. Furniture such as metal furniture has a large number of metal surfaces that reflect electromagnetic waves, and thus the deterioration of the radio wave environment is a problem.

[0005] In order to improve the radio wave environment, an electromagnetic wave absorber made of an electromagnetic wave absorbing material has been conventionally used.
As an electromagnetic wave absorbing material, a composite of ferrite and a binder is generally known. In processing, the thickness is precisely controlled along with a magnetic property and a dielectric property of the composite according to a target frequency. This achieves a large absorption.

In particular, when an electromagnetic wave absorbing material is used as a building material, it must have durability, flame retardancy, workability in mounting, and the like. Therefore, inorganic materials are mainly used as binders rather than organic materials. Many electromagnetic wave absorbing materials have been proposed. Also, many building materials made of inorganic materials for electromagnetic wave shielding have been proposed.

[0007] Japanese Patent Application Laid-Open No. 4-310555 discloses that at least one of a magnetic material and a ferroelectric material is 0.1 to 0.1%.
A gypsum molded article is disclosed in which a hemihydrate gypsum or anhydrous gypsum containing 70% by weight is mixed with a water-absorbing polymer that encloses water in a structure and cured. Japanese Patent Application Laid-Open No. 4-74747 discloses a conductive elastic mortar composition containing cement, gypsum, alumina cement, carbon fiber and a polymer admixture as main components.

JP-A-6-209180 discloses an electromagnetic wave absorbing inner wall comprising gypsum, cement or calcium silicate as a main component and containing carbon, ferrite, metal powder, metal compound powder or a mixture thereof as an electromagnetic wave loss material. A material is disclosed. JP-A-6-122568 discloses an inorganic foam obtained by foaming and curing a water-curable inorganic composition comprising a water-curable inorganic substance, water and carbon fibers.

However, in these techniques, the thickness of the electromagnetic wave absorbing material is large, and the workability and the mounting workability are poor. In addition, when such an electromagnetic wave absorbing material is used as a building material for an intelligent office using information and communication equipment, the electromagnetic wave absorbing ability is insufficient.

Japanese Patent Application Laid-Open No. 7-202472 discloses an electromagnetic wave shielding material in which an electromagnetic wave reflector is integrally formed on one surface of an electromagnetic wave absorber. However, in this technology, since a metal such as a metal mesh material or a lattice-shaped metal member is used as an electromagnetic wave reflector to be used, the electromagnetic wave reflector and the electromagnetic wave absorber are integrally molded in order to form a shield material. When used for walls, ceilings and the like, the mounting workability is poor, which is not preferable.

Further, in such an electromagnetic wave shielding material,
Although the electromagnetic wave absorbing ability in a specific frequency band is excellent, it cannot be uniformly absorbed in any of frequency bands far apart such as a quasi-microwave band, a quasi-millimeter wave band, and a millimeter wave band. Therefore, with the expansion of the use of the quasi-microwave band and the quasi-millimeter wave band as described above,
Related industries have demanded the development of an electromagnetic wave absorbing material that uniformly absorbs any of the frequency bands from the quasi-microwave band to the millimeter wave band. In addition, in order to design such an electromagnetic wave absorber, it is necessary to study the ferrite manufacturing conditions for each frequency of the electromagnetic wave to be absorbed and to manufacture the ferrite, and it is not possible to realize any matching frequency characteristics. It was difficult.

Japanese Patent Application Laid-Open No. Hei 8-27449 discloses an electromagnetic wave shielding material in which a plurality of uneven portions are formed on the surface of an electromagnetic wave absorber. However, in this technique, the thickness of the electromagnetic wave absorber itself becomes large and the weight becomes heavy, and thus there is a problem in handling and workability as a building material.

JP-A-8-83994 discloses that as an electromagnetic wave absorbing material that can be used in a wide band, a first layer made of a conductive material, a metal oxide magnetic fine powder sequentially laminated thereon, A multilayer electromagnetic wave absorbing material having a second layer made of an agent and a third layer made of a metal magnetic fine powder and a binder is disclosed.

The electromagnetic wave absorbing material having this structure has made it possible to absorb electromagnetic waves having a stable low reflection and absorption capability over a wide band of 1 to 60 GHz. This second layer is composed of a metal oxide magnetic fine powder and a binder.
Unlike the sintered ferrite plate disclosed in US Pat. No. 3,679,955, it generally has a small absorption but a high degree of freedom for matching. Therefore, such a low reflective material can prevent mutual interference and delay dispersion of electromagnetic waves in a wide band from a quasi-microwave band to a quasi-millimeter wave band and a millimeter wave band. However, since two layers containing the metal magnetic material and the metal oxide magnetic material are also provided, there is a possibility that the weight becomes heavy.

[0015]

SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to uniformly absorb electromagnetic waves in a wide band from a quasi-microwave band to a millimeter wave band, to be lightweight, to be easy to handle as a building material, and to be capable of working. It is an object of the present invention to provide an electromagnetic wave absorbing material having excellent properties.

[0016]

According to the present invention, there is provided an electromagnetic wave absorbing material comprising an electromagnetic wave absorbing layer comprising a binder (a) and a magnetic powder (b), wherein the magnetic powder (b) comprises:
An electromagnetic wave absorbing material unevenly distributed in the electromagnetic wave absorbing layer. The present invention also provides an electromagnetic wave absorbing material comprising an electromagnetic wave absorbing layer comprising a binder (a) and a magnetic material powder (b), wherein the magnetic material powder (b) is unevenly distributed in the electromagnetic wave absorbing layer. A method for producing an absorbing material, wherein the magnetic powder (b) is used for forming the electromagnetic wave absorbing layer.
This is a method for producing an electromagnetic wave absorbing material that is made unevenly distributed by applying an external force to the material. Hereinafter, the present invention will be described in detail.

The electromagnetic wave absorbing material of the present invention comprises an electromagnetic wave absorbing layer. The electromagnetic wave absorbing layer comprises a binder (a) and a magnetic powder (b). The binder (a) may be an organic binder or an inorganic binder. The organic binder is not particularly limited, but is usually used by dissolving it in an organic solvent, depending on the method of use; plasticizer or a sol using a plasticizer and an organic solvent; They are classified into three types.

The above resin is not particularly restricted but includes, for example, alkyd resin, polyester resin, acrylic resin, silicone resin, polyurethane resin, amino resin,
Examples thereof include phenol resins, xylene resins, toluene resins, nitrocellulose resins, and modified resins thereof. These may be used alone or in combination of two or more. The above resin is not particularly limited, and examples thereof include a vinyl chloride resin, a fluororesin, and a modified vinyl chloride resin. These may be used alone or in combination of two or more.

The above resin is not particularly limited as long as it is a thermoplastic resin. For example, non-polar resins such as polyethylene, polypropylene, polymethylpentene, polybutene, polystyrene, polybutadiene, crystalline polybutadiene and styrene butadiene; , Polyvinyl acetate, polymethyl methacrylate, polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride, polytetrachloroethylene, ethylene-vinyl acetate copolymer resin, modified ethylene-vinyl acetate copolymer resin, ethylene-vinyl acetate-vinyl chloride Graft copolymer resin, chlorinated polyethylene resin, styrene-acrylonitrile copolymer resin (SAN resin), acrylonitrile-butadiene-styrene copolymer resin (ABS resin), acrylate-styrene-acryl Nitrile copolymer resin (ASA
Resin), chlorinated polyethylene-acrylonitrile-styrene copolymer resin (ACS resin), polyacetal resin, polyamide resin, polycarbonate resin, polyphenylene ether resin, polyethylene terephthalate resin, polybutylene terephthalate resin, silicone resin, silicone-modified acrylic resin, silicone Modified polyester resin, polyacrylate resin, polysulfone resin, polyimide resin, polyamideimide resin, polyphenylene sulfide resin, polyoxybenzoyl resin, polyester resin, epoxy resin, phosphazene resin,
Examples thereof include polyetheretherketone resins, polyetherimide resins, and modified resins thereof. These may be used alone or in combination of two or more.

The organic binder preferably has an oxygen index of 30 or more. If it is less than 30, the flame retardancy and the nonflammability decrease. More preferably, it is 40 or more. The oxygen index can be measured by the plastic flame resistance test method of JIS K7201. Among the organic binders, those having a high oxygen index include, for example,
Polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, polyvinyl fluoride, polytetrachloroethylene, ethylene-vinyl acetate-vinyl chloride graft copolymer resin, chlorinated polyethylene resin, modified chlorinated polyethylene resin, chlorinated polyethylene-acrylonitrile-styrene Copolymer resins, silicone resins, silicone-modified acrylic resins, silicone-modified polyester resins, phosphazene resins, and the like can be given. Among them, polyvinyl chloride, ethylene-vinyl acetate-vinyl chloride graft copolymer resin, chlorinated polyethylene resin, modified chlorinated polyethylene resin, and silicone resin are preferable.

The inorganic binder used in the present invention is not particularly limited, and examples thereof include gypsum, lime, calcium silicate, magnesia cement, portland cement, alumina cement, Roman cement, acid-resistant cement, fire-resistant cement, water glass cement and the like. Can be mentioned. From the point of strength and water resistance, Portland cement,
Alumina cement is preferred. Also, weight reduction, workability,
Gypsum is preferred from the viewpoint of electromagnetic wave absorption.

The magnetic powder (b) used in the present invention is preferably a soft magnetic powder, and is preferably a metal oxide magnetic substance or a metal magnetic substance. There are no particular restrictions regarding the metal oxide magnetic material, for example, MnO to Fe ₂ O _3, ZnO,
_{NiO, MgO, CuO, Li 2} O or the like combining a ferrite; NiO-MnO-ZnO-Fe 2 O 3, Mn
_{O-ZnO-Fe 2 O 3} , NiO-ZnO-Fe 2 O 3
Spinel-type ferrite; Garnet-type ferrite;
Spinel type (cubic) γ-Fe ₂ O ₃ , γ-Fe ₄ O
_{4 and the} like. The average particle diameter of the metal oxide magnetic material is preferably 1 to 30 μm. More preferably, it is 1 to 5 μm.

The metal magnetic material is not particularly limited.
For example, Fe-Si-Al alloy (Sendust), Ni-
Examples thereof include an Fe alloy (permalloy), a Co—Fe alloy, and an amorphous alloy having an Fe group or a Co group. The average particle diameter of the metal magnetic material is preferably 1 to 30 μm.

In the present invention, it is preferable to use a metal oxide magnetic material as the magnetic powder (b) in order to reduce the weight of the obtained electromagnetic wave low-reflecting material and enhance the electromagnetic wave absorbing ability. More preferably, Mn is added to Fe ₂ O ₃ .
It is a spinel-type ferrite magnetic powder combining O, ZnO, NiO, and MgO. More preferably, Mn-
They are Mg-Zn ferrite magnetic powder and Mn-Zn ferrite magnetic powder.

In the present invention, the magnetic powder (b)
Is a coupling agent such as a silane coupling agent, a titanate coupling agent, or an aluminate coupling agent, if necessary; a surfactant, a wetting agent for improving the wettability or fluidity of the magnetic powder; Additives such as a viscosity reducing agent and a stabilizer; and may be surface-treated with a resin or the like. By the surface treatment, a functional group that imparts reactivity to the magnetic powder (b) or a functional group that governs wettability can be introduced, so that the magnetic powder (b) has a wettability with the inorganic binder and an electromagnetic wave absorption layer. Dispersibility and dispersion stability can be improved.

The amount of the binder (a) and the magnetic powder (b) is 30 to 30 parts by weight based on 100 parts by weight of the total of the binder (a) and the magnetic powder (b). 90 parts by weight and magnetic powder (b) 70
-10 parts by weight is preferred. When the amount of the binder (a) is less than 30 parts by weight and the amount of the magnetic powder (b) exceeds 70 parts by weight, the productivity of the electromagnetic wave absorbing layer is poor, and the bending strength of the obtained electromagnetic wave absorbing layer is reduced to provide sufficient physical properties. And the amount of the magnetic powder increases, the weight of the electromagnetic wave absorbing layer increases, the binder (a) exceeds 90 parts by weight, and the magnetic powder (b) does not exceed 10 parts by weight. In addition, the electromagnetic wave absorbing layer has insufficient electromagnetic wave absorbing ability and is not practical.

When gypsum or calcium silicate is used as the binder (a), gypsum or calcium silicate is added to the total of 100 parts by weight of the gypsum or calcium silicate and the magnetic powder (b). 90 parts by weight,
In addition, the amount of the magnetic powder (b) may be 55 to 10 parts by weight, the amount of the magnetic powder (b) to be mixed can be reduced, and the weight of the obtained electromagnetic wave absorbing layer can be reduced. In particular, when the binder (a) is gypsum, even if the amount of the magnetic powder (b) is small, sufficient electromagnetic wave absorbing ability can be obtained within the above range. Gypsum or calcium silicate is less than 55 parts by weight, and magnetic powder (b)
Exceeds 45 parts by weight, the electromagnetic wave absorbing ability is sufficient, but the weight of the electromagnetic wave absorbing layer is increased and the cost is increased.
If the amount is more than 10 parts by weight and the amount of the magnetic powder (b) is less than 10 parts by weight, the electromagnetic wave absorbing ability in a few GHz band is low.

In the present specification, the amount of the inorganic binder such as gypsum or calcium silicate is calculated based on the weight of the inorganic binder in a state of being cured with water.
In general, among inorganic binders having water-curing properties, after mixing with an appropriate amount of water, at normal temperature or heated,
Further, it is cured by applying pressure as needed, and in the curing process, water that is unnecessary for the curing is evaporated and discharged out of the system. The amount is generally very small. Accordingly, the weight of the inorganic binder after curing is substantially equal to the weight of the inorganic binder containing water in an amount necessary for curing.

In the present invention, the magnetic powder (b)
Are unevenly distributed in the electromagnetic wave absorbing layer. In the present specification, uneven distribution means a state in which a portion where the dispersion amount of the magnetic powder (b) is large and a portion where the dispersion amount is small exist in one electromagnetic wave absorbing layer.

The uneven distribution includes, for example, (1) a state in which the concentration distribution in the depth direction of the electromagnetic wave absorbing layer of the magnetic powder (b) shows an uneven distribution, and (2) an electromagnetic wave absorption of the magnetic powder (b). A state in which the concentration distribution in the plane direction of the layer shows a biased distribution,
(3) A state in which the concentration distribution of the magnetic powder (b) in the depth direction and the plane direction of the electromagnetic wave absorbing layer shows a biased distribution, and the like. Hereinafter, these distributions will be described with reference to the drawings.

In the state (1), the magnetic powder (b) has a region in which the concentration distribution in the depth direction of the electromagnetic wave absorbing layer is not uniform, and there is a locally concentrated region near a certain depth. Is what you are doing. In this specification, the state (1) is also referred to as a vertical distribution uneven distribution type. In the vertical distribution uneven distribution type, for example, as shown in FIG. 1, a large amount of magnetic powder (b) 2 is present near one surface of the electromagnetic wave absorbing layer 1 and a small amount is present on the opposite surface. It is an uneven distribution state such as a state. Such uneven distribution of the magnetic powder (b) is formed by, for example, gravity, centrifugal force, magnetic force, artificially applied acceleration, and the like.

The uneven distribution of the magnetic powder (b) in the state (1) can be measured by analyzing the surface with a fluorescent X-ray, and the cross section in the depth direction is analyzed by an X-ray microanalyzer. Can also be measured. When the uneven distribution of the magnetic powder (b) is confirmed by the fluorescent X-ray in the electromagnetic wave absorbing layer using the inorganic binder as the binder (a), the magnetic powder (b) is often used by using the fluorescent X-ray. The measurement can be performed by measuring the Fe / Ca ratio of a part and a small part. In the fluorescent X-ray method,
Since the amount of the element present is obtained as the count cps per unit time, the Fe / Ca ratio of the portion where the magnetic powder (b) is unevenly distributed and the Fe / Ca ratio of the portion where the magnetic powder (b) is uniformly present are determined. / Ca ratio.

The ratio of uneven distribution of the magnetic powder (b) (hereinafter referred to as “uneven distribution ratio”) is expressed by: (uneven distribution ratio) = (Fe / Ca ratio of unevenly distributed portion) / (Fe / Ca ratio of uniform portion) In the case where the magnetic powder (b) is large, the uneven distribution ratio is preferably 1.02 to 3.5. When it is less than 1.02, the magnetic powder (b)
If the effect due to uneven distribution of the compound is small and exceeds 3.5, the physical properties of the surface of the electromagnetic wave absorbing layer are degraded, and the absorption wavelength is deviated, and good electromagnetic wave absorption cannot be obtained in a wide frequency range. Is generated.

In the state (2), a region where the magnetic powder (b) is locally concentrated in the electromagnetic wave absorbing layer exists in a plane. In this specification, the state (2) is also referred to as a planar distribution uneven distribution type.
In the state (2), for example, as shown in FIGS. 2 and 3, the abundance of the magnetic powder (b) 2 increases on and near at least one surface of the electromagnetic wave absorbing layer 1. Represents the state where the parts are scattered.

There is no particular limitation on the mode of scattering of the region where the amount of the magnetic powder (b) is large. For example, a mode in which circular regions are repeatedly scattered as shown in FIG. As shown in FIG. 3, streak-like regions are repeatedly scattered, and other regions having an arbitrary shape such as a square or an irregular shape are regularly or irregularly scattered. it can.

In the state (2), the magnetic powder (b) is unevenly distributed, for example, by forming a planar magnetic force pattern using a magnet sheet or an electromagnet and forming an electromagnetic wave absorbing layer along the surface. Method: A method of forming an electromagnetic wave absorbing layer by forming at least one magnetic force line, for example, by arranging at least one magnetic force line having a certain width; Two or more kinds having different composition ratios of the binder (a) and the magnetic powder (b) A method in which the magnetic powder (b) is unevenly distributed in a plane by alternately supplying the composition of (1); an electromagnetic wave produced by unevenly distributing the magnetic powder (b) as in the vertical distribution type or the like. The absorption layer is arranged and integrated so that the concentration distribution of the magnetic substance powder (b) is formed on a plane, and the magnetic substance powder (b) is unevenly distributed as a whole;

The uneven distribution of the magnetic powder (b) in the state (2) is usually caused by the fact that the magnetic powder (b) itself is
Since the powder is a brown or black colored powder, if the uneven distribution occurs on the surface, the surface of the electromagnetic wave absorbing layer can be easily checked with the naked eye after forming the electromagnetic wave absorbing layer. The degree of uneven distribution of the magnetic substance powder (b) on the surface is preferably such that it can be visually observed.

The state (3) shows a distribution in which the concentration distribution of the magnetic powder (b) in the depth direction and the plane direction of the electromagnetic wave absorbing layer is deviated. For example, as shown in FIG. Further, on at least one surface of the electromagnetic wave absorbing layer, regions where the magnetic substance powder (b) is locally concentrated are scattered in a plane, and the magnetic substance powder (b) is also dispersed in the depth direction. (B) is a region where the region is locally concentrated. In the present specification, the state (3) is also referred to as a mixed type.

In the mixed type, the state in which the concentration distribution in the depth direction and the plane direction of the magnetic powder (b) is deviated is, for example, a method used in the vertical distribution uneven distribution type or the plane distribution uneven distribution type; It is formed by a method combining these methods and the like. Specifically, the magnetic powder (b) is unevenly distributed in the depth direction of the electromagnetic wave absorbing layer using the difference in specific gravity between the binder (a) and the magnetic powder (b), and then the planar magnetic force is increased. A method in which a pattern is formed by a magnet sheet or an electromagnet and an electromagnetic wave absorbing layer is formed along the surface; after the magnetic powder (b) is unevenly distributed in the depth direction of the electromagnetic wave absorbing layer, a slit-shaped electromagnet is formed. The magnetic powder (b) is vertically distributed and the magnetic powder (b) is also scattered and distributed on the front surface or the back surface in a planar manner by a method of intermittently generating lines of magnetic force by passing over the magnetic powder. it can.

The uneven distribution of the magnetic powder (b) in the state (3) is confirmed, for example, by checking the uneven distribution of the magnetic powder (b) in the state (1) and the state (2). It can be confirmed by a method or the like.

In the state of (2) and the state of (3), when the magnetic powder (b) has a distribution in which the concentration distribution in the planar direction in the electromagnetic wave absorbing layer in the electromagnetic wave absorbing layer is biased by magnetic force, Preferably, the distribution is based on a specified pattern. The type of the specified pattern is not particularly limited. For example, a pattern formed by repeating an arbitrary pattern unit in the vertical direction and the horizontal direction, a pattern formed by repeating a linear pattern unit, and a pattern formed by repeating a plurality of planar pattern units. Examples include a pattern by repetition and a pattern in which arbitrary pattern units are randomly scattered.

The pattern of the magnetic powder (b) formed by repeating the arbitrary pattern unit in the vertical and horizontal directions can be obtained by, for example, a method of forming a surface by arranging electromagnets by magnets or coils, or repeating an arbitrary pattern. It is formed by a method using a magnet sheet having the formed planar magnetized pattern or the like. The shape of the arbitrary pattern unit may be a circle, a square, an irregular shape, or the like as a pattern of a portion where a large amount of the magnetic powder (b) is present. These may be used alone or in combination of two or more.

The pattern of the magnetic powder (b) by repeating the linear pattern unit is, for example, a method in which a linear magnet sheet having a certain width is repeatedly used, and the linear pattern unit is formed by an electromagnet. It is formed by a method using the patterned surface or the like. When the electromagnetic wave absorbing layer is continuously manufactured on a manufacturing line, such a linear pattern is repeatedly used in the direction of the manufacturing line of the electromagnetic wave absorbing layer to reduce the uneven distribution of the magnetic powder (b). It becomes possible. Further, the magnetic powder (b) can be unevenly distributed by intermittently generating lines of magnetic force having a certain width in the traveling direction of the production line of the electromagnetic wave absorbing layer.

The pattern obtained by repeating the plurality of planar pattern units of the magnetic powder (b) may be, for example, a plurality of pattern units arbitrarily selected from the arbitrary pattern unit, the linear pattern unit, and the like. It is formed by a method using a magnet sheet having a planar magnetized pattern formed by repetition or the like.

The pattern formed by randomly arranging the arbitrary pattern units of the magnetic powder (b) is formed by, for example, a method using a mechanism in which a magnetic force pattern is independently formed by combining a mechanism for generating magnetic force lines. Is done.

The uneven distribution pattern of the magnetic powder (b) is related to the frequency dependence of the electromagnetic wave absorbing ability. Although the reason is not clear, the interval between each pattern is 2 to 50.
In the case of mm, it is possible to enhance the electromagnetic wave absorbing ability in a wide band. In a pattern obtained by repeating the arbitrary pattern units in the vertical and horizontal directions, it is preferable that the distance between the pattern units is 2 to 50 mm. In the pattern obtained by repeating the linear pattern unit, the interval between the obtained stripe patterns is 2 to 50 m.
It is preferably within the range of m. In the pattern formed by repeating the plurality of planar pattern units, it is preferable that the distance between the pattern units is 2 to 50 mm. In a pattern in which the arbitrary pattern units are randomly scattered, the planar pattern unit used may itself be involved in the electromagnetic wave absorbing ability in a wide band, but as an interval between the patterns, It is preferably within a range of 2 to 50 mm.

In the present invention, when the electromagnetic wave absorbing layer is manufactured as a single layer, the influence of the volume, specific gravity, content, etc. of the magnetic powder (b) in the composition, and the problem of the manufacturing process, When the magnetic powder (b) is unevenly distributed, even if the treatment for forming only the state of (2) is performed, the concentration distribution in the depth direction may be unbalanced at the same time, and the mixture tends to be a mixed type. Therefore, it may be difficult to clearly distinguish the vertical distribution uneven distribution type, the plane distribution uneven distribution type, and the mixed type.

The electromagnetic wave absorbing layer may be mixed with various materials, for example, fibrous conductors, if necessary, in addition to the binder (a) and the magnetic powder (b). Examples of the fibrous conductor include simple metals such as stainless steel, brass, copper, aluminum, nickel, and lead;
Metal fibers produced from alloys; metal-coated fibers obtained by subjecting metals such as vegetable fibers, synthetic fibers, and inorganic fibers to vapor deposition, plating, and coating; polyacrylonitrile-based carbon fibers, pitch-based carbon fibers, rayon And carbon-based fiber materials such as carbon-based whiskers. Among them, metal-coated fibers and carbon-based fiber materials are preferable because of good dispersibility and electromagnetic wave absorbing ability during the production of the electromagnetic wave absorbing layer.

Since the fibrous conductor is used by mixing with the binder (a), when the binder (a) is an inorganic binder, the fibrous conductor is excellent in water wettability and dispersion stability. Are preferred. Even if the fibrous conductor has good wettability to water, if the fiber is curled, or if the fiber is inferior in rigidity or toughness, the fiber is easily entangled. When it is mixed with the body powder (b), it tends to form a lump, making uniform dispersion difficult, so that those having both excellent wettability to water and dispersion stability are preferred.

The fibrous conductor has a fiber diameter of 5-5.
It is preferably 0 μm. In addition, the length of the fiber is preferably 2 to 40 mm because if the length is too long, the fiber is likely to be entangled. More preferably, it is 3 to 10 mm.

The compounding amount of the fibrous conductor is preferably 0.005 to 2.0 parts by weight based on 100 parts by weight of the total of the binder (a) and the magnetic powder (b).
When the amount is less than 0.005 parts by weight, the effect of enhancing the electromagnetic wave absorbing ability is small, and when the amount exceeds 2.0 parts by weight, the electromagnetic waves are reflected on the surface of the electromagnetic wave absorbing layer, and sufficient electromagnetic wave absorbing ability cannot be obtained. .

In the present invention, other fibrous substances may be used. The other fibrous substances are not particularly limited, and include, for example, natural plant fibers such as cotton and hemp; fibers such as glass fiber and asbestos; synthetic fibers such as polyester, polyacrylonitrile, polyamide, and polypropylene; Needle-like reinforcing fibers and the like can be mentioned. The above-mentioned other fibrous substances may be used for reinforcing the electromagnetic wave absorbing layer.

In the present invention, in order to further reduce the weight of the electromagnetic wave absorbing layer, when an inorganic binder is used as the binder (a) in forming the electromagnetic wave absorbing layer, a foamable filler is further added. You may make it contain. In a conventional method of reducing the weight, for example, using a large amount of a foaming agent or foaming by strong stirring, the magnetic powder (b) loses stability at the gas-liquid interface of the generated foam. Agglomeration easily occurs, a uniform dispersion state cannot be obtained, and the electromagnetic wave absorbing ability also decreases.

When the above-mentioned foamable filler is contained in the above-mentioned electromagnetic wave absorbing layer, the above-mentioned magnetic powder (b) and the above-mentioned fibrous conductor can be sufficiently dispersed and compounded, and at the same time, the specific gravity of the electromagnetic wave absorbing layer is reduced. Therefore, the weight can be reduced without lowering the electromagnetic wave absorbing ability.

The foamable filler is not particularly limited, and examples thereof include an inorganic foamable filler and an organic foamable filler. The inorganic foamable filler is not particularly limited. For example, natural lightweight aggregates such as volcanic debris; expanded shale, expanded clay, expanded vermiculite, expanded perlite, expanded obsidian, coal gala, molten fly ash, silica balloon And artificial lightweight aggregates such as pearlite, shirasu balloon, glass balloon and the like. These may be used alone or in combination of two or more.

The organic foamable filler is not particularly restricted but includes, for example, styrofoam particles, urethane foam particles, acrylic resin hollow balloons, acrylic modified resin hollow balloons, melamine resin balloons, urethane modified resin hollow balloons and the like. Can be mentioned. These may be used alone or in combination of two or more.
Moreover, you may use together with the said inorganic type foamable filler.

As the foamable filler, any of the above-mentioned inorganic foamable filler and the above-mentioned organic foamable filler may be used, but it is light in weight, strong in strength, spherical, and has a smooth surface. What satisfy | fills conditions, such as having a small particle size distribution width, low water absorption, not containing a water-soluble component, and having no water swelling property, is preferable.

In other words, as the foamable filler, those which do not increase the amount of water to be kneaded when kneading the inorganic binder and water, and lower the fluidity of the slurry obtained by kneading the inorganic binder and water. What does not
Even when water is absorbed, it is preferable that the water absorbed in the drying step is volatilized.

Accordingly, as the foamable filler, those satisfying the above conditions are preferably expanded vermiculite, perlite, shirasu balloon, styrene foam particles, urethane foam particles, and acrylic resin hollow balloon.

The structure of the foamable filler is not particularly limited, and is, for example, a balloon structure in which the inside is empty and the outside has a shell; one filler is a particle, and the inside of the particle is closed cells or continuous cells. Spongy body structure in which a group of air bubbles exist; a structure in which these are combined; and the like.

The foamable filler having the balloon structure is as follows:
It can be easily obtained by baking at a high temperature and foaming. The foamable filler having the spongy structure can be easily obtained by a method of microfoaming with a gas generating agent, a method of removing a liquid substance from particles synthesized by incorporating a liquid substance, and the like.

The specific gravity of the foamable filler is not particularly limited, and usually, the apparent specific gravity is preferably 0.05 to 1.70, and the unit volume weight is 0.01 to 0.50.
kg / L is preferred.

The average particle size of the expandable filler is not particularly limited, and is generally preferably 0.05 μm to 5 mm.
The average particle size of the inorganic foamable filler among the foamable fillers is larger than the average particle size of the organic foamable filler, and is usually 0.1 to 5 mm. The average particle diameter of the organic foamable filler can be relatively freely adjusted by the synthesis conditions and the synthesis method.

The content of the expandable filler is preferably 0.01 to 20 parts by weight based on 100 parts by weight of the inorganic binder and the magnetic powder (b) in total. 0.0
If the amount is less than 1 part by weight, the effect of the addition of the foamable filler is small and the effect on weight reduction cannot be obtained. If the amount exceeds 20 parts by weight, the effect on weight reduction can be obtained, but the physical strength of the electromagnetic wave absorbing layer is obtained. Is undesirably reduced.

The thickness of the electromagnetic wave absorbing layer is 5 to 50 mm
Is preferred. If it is less than 5 mm, the physical strength of the electromagnetic wave absorbing layer is weak, and if it exceeds 50 mm, the weight becomes heavy.
Further, when the electromagnetic wave absorber is used as a building material, if it is out of the above range, the mounting workability and the fitting property are poor. Preferably, it is 7 to 25 mm.

The specific gravity of the electromagnetic wave absorbing layer is 0.50 to 0.50.
1.65 is preferred. If it is less than 0.50, the electromagnetic wave absorbing ability decreases, and if it exceeds 1.65, the weight of the electromagnetic wave absorbing layer increases, which is not preferable. In the present invention, from the viewpoint of mounting workability, the specific gravity is preferably 0.60 to 0.60.
The specific gravity is preferably from 0.60 to 1.00 in order to make it about the same as that of a conventionally used gypsum board.

Although the electromagnetic wave absorbing material of the present invention comprises the above-mentioned electromagnetic wave absorbing layer, it is preferable to further combine an electromagnetic wave reflecting layer. The electromagnetic wave reflection layer is not particularly limited, but is preferably made of a conductive material, a metal deposition film, a metal foil, or a metal powder. These may be used alone,
More than one species may be used in combination. The electromagnetic wave reflecting layer can also serve as a support.

The electromagnetic wave reflection layer has a shielding ability of 20
It is preferably at least dB. More preferably, 30
dB or more.

The above-mentioned conductive material is not particularly limited as long as it provides a shielding performance of at least 20 dB, preferably at least 30 dB, for example, copper, aluminum, steel, iron, nickel, stainless steel, and stainless steel. Metal plates such as brass; metal plates plated with these metals;
Metal cloth; a plated steel plate obtained by plating aluminum, zinc, copper, or the like on a steel plate by heat or electricity can be used. Such a conductive material may have been subjected to a surface treatment or a primer treatment for improving interlayer adhesion, such as a precoated steel sheet.

The metal deposition film is not particularly limited.
For example, a material in which a vapor-deposited layer of aluminum or the like is formed on a non-conductive material such as plastic material; paper; synthetic paper such as a PET film, or the like can be given. The metal foil is not particularly limited, and examples thereof include a metal foil used as the conductive material. The metal powder is not particularly limited, and examples thereof include metal powder used as the conductive material.
In the present invention, from the viewpoint of weight reduction as a building material, paper,
It is preferable to deposit aluminum or the like on a non-conductive material such as a PET film.

In addition to the above, a conductive coating film containing a metal used as the conductive material and a binder is provided on a non-conductive material such as a plastic material, paper, or synthetic paper. Or a metallized material having an electroless plating layer such as copper or nickel formed thereon.

The thickness of the electromagnetic wave reflection layer is 50 μm to 3 μm.
mm is preferred. If it is less than 50 μm, the mechanical strength of the electromagnetic wave reflecting layer is reduced, and if it exceeds 3 mm, the weight of the electromagnetic wave reflecting layer becomes heavy and is not practical.

The electromagnetic wave absorbing material of the present invention can be formed by forming the above-mentioned electromagnetic wave absorbing layer and, if necessary, providing the above-mentioned electromagnetic wave reflecting layer. The method for providing the electromagnetic wave reflecting layer is not particularly limited, and for example, a method of bonding the electromagnetic wave reflecting layer to one surface of the electromagnetic wave absorbing layer can be suitably employed. The bonding is performed by, for example, attaching a paper on which aluminum serving as the electromagnetic wave reflection layer is deposited, a paper to which an aluminum foil is bonded, an aluminum foil, or the like to one surface of the electromagnetic wave absorption layer using an adhesive or the like. Can be.

The electromagnetic wave absorbing material of the present invention utilizes an absorption effect as a transmission absorption loss of a passing electromagnetic wave, or
When it is installed on a metal surface, it utilizes the electromagnetic wave absorption effect as a reflection and absorption loss.However, when the electromagnetic wave reflection layer is provided, the reflection and absorption loss of the electromagnetic wave is similar to that when it is installed on a metal surface. The electromagnetic wave absorption effect can be used.

In the method for producing an electromagnetic wave absorbing material of the present invention, when the binder (a) is an organic binder, the organic binder may be used as it is in the form of a resin powder or by dissolving or dispersing the resin powder in a solvent. Is done. When the organic binder has a low molecular weight, the physical properties of the electromagnetic wave absorbing material can be satisfied by forming a polymer by performing a crosslinking reaction after forming the electromagnetic wave absorbing layer.

When the binder (a) is an organic binder, the electromagnetic wave absorbing material of the present invention is produced by, for example, the following method. Mix resin powder with solvent, or
The magnetic powder (b) is dispersed in a solution obtained by heating a resin powder, and the resin powder is dispersed in a layer by a coating method generally used in the paint industry, a die coater method, an extrusion method, or the like. After the composition is formed in a layered form by the method described above, uneven distribution treatment described in detail below is performed to remove the solvent or to cool the resin solution to obtain an electromagnetic wave absorbing layer.

When the binder (a) is an inorganic binder, as described above, many of them have water curability and are cured by reaction with water, so that they are mixed with water and used as a slurry. Is done. Since the slurry of the inorganic binder is rich in fluidity and low in viscosity, it is suitable for uneven distribution of the magnetic powder (b).

In the planar distribution uneven distribution type, it is usually preferable to use a magnetic force as an external force. For example, by laying a magnet sheet magnetized with an appropriate pattern under a mold and pouring a binder (a) and a magnetic powder (b) into the mold, for example, as shown in FIG. 5 and FIG. The magnetic powder (b) 2 is unevenly distributed on the lower surface of the electromagnetic wave absorbing layer 1 in the same pattern as the pattern formed on the magnet sheet 3a formed of a circular pattern unit or the magnet sheet 3b formed of a linear pattern unit. Can be done.

The uneven distribution of the magnetic powder (b) greatly depends on the viscosity of the composition at the time of manufacturing the electromagnetic wave absorbing layer, and the uneven distribution is more easily performed as the viscosity of the composition decreases. Can be.

In the method for producing an electromagnetic wave absorbing material of the present invention, the uneven distribution of the magnetic substance powder (b) is intentionally performed, and when the conventional electromagnetic wave absorbing material is produced, it is considered as a defective product. Distinguished from what occurs.

Hereinafter, the method for producing an electromagnetic wave absorbing material of the present invention will be described in detail, taking as an example the case where the electromagnetic wave absorbing layer is a gypsum board, a mortar or a cement board.

1. Gypsum board calcined gypsum, magnetic powder (b), water, and if necessary, fibrous conductor, foamable filler, organic binder, foaming agent, stabilizer, dispersant, water reducing agent, aggregate, etc. Then, after sufficiently mixing with a mixer to form a slurry, on a plate on which a magnet set in a striped manner with a gap of 7 mm was set,
On the gypsum board base paper, spread the slurry, adjust the thickness while performing uneven distribution treatment, further heat the gypsum board base paper, harden the slurry, coagulate and dry To obtain an electromagnetic wave absorbing layer. On one side of the obtained electromagnetic wave absorbing layer, if necessary, a paper on which aluminum serving as an electromagnetic wave reflecting layer is deposited, paper to which aluminum foil is adhered, aluminum foil or the like is coated with an adhesive or the like on one side of the electromagnetic wave absorbing layer. By using and attaching, an electromagnetic wave absorbing material is obtained.

In this case, the electromagnetic wave absorbing layer may be reinforced by using another fibrous substance in addition to the fibrous conductor.

When using the above-mentioned foamable filler,
The amount of each component is 55 to 90 parts by weight of calcined gypsum and 45 to 10 parts by weight of magnetic powder (b), based on 100 parts by weight of the total of calcined gypsum and magnetic powder (b). Preferably, the fibrous conductor is 0.01 to 0.8 parts by weight, and the foamable filler is 0.1 to 15 parts by weight.

In this case, if the amount of the foamable filler is less than 0.1 part by weight, the effect on the weight reduction is not sufficient, and if it exceeds 15 parts by weight, the effect on the weight reduction is obtained, but the base paper for the gypsum board is not used. It is not preferable because the adhesion to the material forming the electromagnetic wave absorbing layer is reduced and the physical strength of the obtained electromagnetic wave absorbing layer is reduced.

[0086] 2. As the mortar binder (a), cement, gypsum and alumina cement are used. The binder (a), the magnetic powder (b), water, and if necessary, other fibrous substances, foamable fillers, polymer admixtures, After adding a foaming agent, an inorganic filler, a water-soluble polymer, a water reducing agent, a curing accelerator, a curing retarder, etc., and thoroughly mixing with a mixer to form a slurry,
After pouring into the mold, a bar-shaped electromagnet is placed on the mold, the form is slowly scanned using the electromagnet to perform uneven distribution treatment, and then dried at room temperature of about 20 ° C. Thereby, an electromagnetic wave absorbing layer is obtained. On one side of the obtained electromagnetic wave absorbing layer of the obtained electromagnetic wave absorbing layer, if necessary,
An electromagnetic wave absorbing material is obtained by attaching the electromagnetic wave reflecting layer using an adhesive or the like.

In this case, when the weight is reduced, the amount of each of the above components is such that the binder (a) is added to the total of 100 parts by weight of the binder (a) and the magnetic powder (b). It is preferable that the magnetic material powder (b) is 35 to 15 parts by weight.

When the foaming filler (d) is used to further reduce the weight, the water-hardening inorganic binder (a) and the magnetic powder (b) are used in an amount of 100 parts by weight in total. It is preferable that the water-curable inorganic binder (a) is 55 to 90 parts by weight and the foamable filler is 0.01 to 20 parts by weight.

[0089] 3. Cement board Portland cement, magnetic powder (b), water, if necessary, fibrous conductor, other fibrous substances, foamable filler, polymer admixture, foaming agent, inorganic filler, water-soluble polymer, Add water reducing agent, curing accelerator, curing retarder, etc.
After sufficiently mixing with a mixer to form a slurry, the mixture is poured into a mold provided with a pattern surface for uneven distribution formed by arranging rod-shaped magnets, dehydrated under pressure, and cured by curing to obtain an electromagnetic wave absorbing layer. An electromagnetic wave absorbing material is obtained by attaching an electromagnetic wave reflecting layer to one side of the obtained electromagnetic wave absorbing layer using an adhesive or the like, if necessary.

In this case, the amount of each of the above components is such that the Portland cement is 5 parts per 100 parts by weight of the total of the Portland cement and the magnetic powder (b).
5 to 90 parts by weight, and 45 to 45 parts by weight of the magnetic powder (b)
10 parts by weight, the fibrous conductor is 0.01 to
Preferably it is 0.8 parts by weight.

When the above foamable filler is used,
The mixing amount of each component is 55 to 90 parts by weight of the Portland cement and 45 to 10 parts by weight of the Portland cement, based on 100 parts by weight of the total of the Portland cement and the magnetic substance powder (b). Parts by weight, the fibrous conductor is preferably 0.01 to 0.4 parts by weight, and the foamable filler is preferably 0.01 to 20 parts by weight.

The electromagnetic wave absorbing material according to the present invention is 1 to 20 GHz.
In a wideband such as that described above, it has an electromagnetic wave absorption capacity of about -3 to -10 dB, so that partition boards can be installed in an indoor space of an intelligent office or the like where there is concern about interference, malfunction due to mutual interference of electromagnetic waves and delay dispersion. , Partition, partition, movable partition, etc., and as an electromagnetic wave permeable wall material in the indoor space, one or two sheets are installed in a sandwich structure, when electromagnetic waves are transmitted The electromagnetic wave absorption effect as a transmission absorption loss can be used, and interference, malfunction, and the like due to mutual interference of electromagnetic waves and delay dispersion can be prevented.

Further, when the electromagnetic wave absorbing material of the present invention is installed on a metal surface such as a wall or ceiling of an intelligent office or the installed furniture or the like, the metal surface becomes a reflection surface of the electromagnetic wave, and when the electromagnetic wave is low-reflected. Since the electromagnetic wave absorption effect as the reflection absorption loss of the room can be used, unnecessary electromagnetic waves are gradually absorbed while the indoor electromagnetic waves are repeatedly reflected, and the radio wave environment is improved as a whole.

Further, in the electromagnetic wave absorbing material of the present invention, the magnetic powder (b) constituting the electromagnetic wave absorbing layer is unevenly distributed.
As compared with the case where the same amount of magnetic material powder is used to make the powder uniform, a larger electromagnetic wave absorbing performance can be obtained. In other words, with the same electromagnetic wave absorbing ability, the amount of the magnetic substance powder can be reduced, and therefore, the weight of the electromagnetic wave absorbing material can be reduced, and the electromagnetic wave absorbing material is excellent in handleability and workability as a building material. Become. Further, by unevenly distributing the magnetic substance powder (b), the mechanical properties of the electromagnetic wave absorbing material can be improved, and the strength as a building material can be provided.

As described above, the electromagnetic wave absorbing material of the present invention can be used for partition boards, partitions, screens, etc. installed in an indoor space of an intelligent office or the like where there is concern about interference, malfunction, etc. due to mutual interference of electromagnetic waves and delay dispersion. When it has an electromagnetic wave reflecting layer, it is also suitable for building materials such as walls and ceilings of intelligent offices.

[0096]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 A slurry was prepared by mixing 46.1 parts by weight of calcined gypsum, 40 parts by weight of water, and 53.9 parts by weight of Mn-Zn ferrite powder with a mixer, and had a striped magnetization pattern with a gap of 7 mm. After spreading on a gypsum board base paper on which a strong magnet sheet is laid and adjusting the film thickness, the gypsum board base paper is further laminated and heated and dried at 100 ° C. to disperse the ferrite powder in two dimensions. I got The obtained electromagnetic wave absorbing layer had a thickness of 9.5 mm and a specific gravity of 1.43. When the obtained electromagnetic wave absorbing layer was heated to measure the content of gypsum crystal water, the hydration rate of calcined gypsum was 17%. Further, when the electromagnetic wave absorbing layer was observed except for the gypsum board base paper, a stripe pattern with a gap of 7 mm, which was considered to be formed by ferrite, was observed on the surface in contact with the magnet sheet surface. Next, a 50 μm PET film on which aluminum having a shielding ability of 30 dB was deposited was attached to the back surface of the electromagnetic wave absorbing layer with an adhesive to obtain an electromagnetic wave absorbing material. The return loss of the obtained electromagnetic wave absorber at oblique incidence was measured.

Measurement of return loss at oblique incidence The return loss at 45 ° oblique incidence of the electromagnetic wave of the electromagnetic wave absorbing material was measured using a near electromagnetic field antenna measuring device (NFAM, manufactured by Icom Inc.).
1.9 GHz, 2.45 GHz, 1
At 9 GHz, in the TM mode, a measuring method in which the electric field is perpendicular to the stripe pattern and the magnetic field is parallel (H method), and a measuring method in which the electric field is parallel to the stripe pattern and the magnetic field is perpendicular (V method). And the results are shown in Table 1.

Example 2 66.6 parts by weight of calcined gypsum, 70 parts by weight of water, Mn-Mg-Z
33.4 parts by weight of n ferrite powder and 0.02 parts by weight of coal pitch-based carbon fiber (fiber diameter 10 μm × 6 mm) are mixed with a mixer to form a slurry, and a strong magnet having a stripe-like magnetization pattern in a gap of 5 mm. An electromagnetic wave absorbing layer in which ferrite powder was unevenly distributed was obtained in the same manner as in Example 1 except that a magnet sheet was used. The obtained electromagnetic wave absorbing layer had a thickness of 12.5 mm and a specific gravity of 1.30. Also, on the surface of the obtained electromagnetic wave absorbing layer in contact with the magnet sheet, a stripe pattern with a gap of 5 mm, which was considered to be formed by ferrite, could be observed. Next, an aluminum foil having a shielding ability of 30 dB and a thickness of 100 μm was attached to the back surface of the electromagnetic wave absorbing layer with an adhesive to obtain an electromagnetic wave absorbing material. The return loss at oblique incidence was measured in the same manner as in Example 1. The results are shown in Table 1.

Example 3 Portland cement 70 parts by weight, water 30 parts by weight, Mn
-A slurry obtained by mixing 20 parts by weight of Zn ferrite powder, 0.04 parts by weight of coal pitch-based carbon fiber (fiber diameter 10 µm x 6 mm), and 2 parts by weight of cellulose pulp and 0.2 parts by weight of methylcellulose as a reinforcing fiber using a mixer. And pour it into the formwork, width 2cm and length 40cm
The mold was scanned twice with a strong electromagnet rod to perform uneven distribution treatment, heated and dehydrated, and cured to obtain an electromagnetic wave absorbing layer in which ferrite powder was unevenly distributed. The obtained electromagnetic wave absorbing layer had a thickness of 45 mm. When the amount of ferrite on the front and back surfaces of the obtained electromagnetic wave absorbing layer was quantified by X-ray fluorescence, the uneven distribution ratio of the surface containing a large amount of ferrite based on the Fe / Ca ratio was 1.2. Next, the shielding ability is 35 dB and the thickness is 100 μm.
Was adhered to the back surface of the electromagnetic wave absorbing layer with an adhesive to obtain an electromagnetic wave absorbing material. Using the same device as in Example 1, the return loss in the TE mode was measured at oblique incidence. The results are shown in Table 2.

Comparative Example 1 An electromagnetic wave absorbing layer was obtained in the same manner as in Example 1 except that the uneven distribution treatment was not performed. The obtained electromagnetic wave absorbing layer had a thickness of 9.5 mm and a specific gravity of 1.42. Shielding ability is 30 dB and thickness is 50 μm as in the first embodiment.
Then, a PET film on which aluminum was vapor-deposited was adhered to the back surface of the electromagnetic wave absorbing layer with an adhesive to obtain an electromagnetic wave absorbing material.
The return loss at oblique incidence was measured in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 2 An electromagnetic wave absorbing layer was obtained in the same manner as in Example 2 except that the uneven distribution treatment was not performed. The obtained electromagnetic wave absorbing layer had a thickness of 12.5 mm and a specific gravity of 1.30. An electromagnetic wave reflecting layer was adhered to the back surface of the electromagnetic wave absorbing layer with an adhesive in the same manner as in Example 2 to obtain an electromagnetic wave absorbing material. The return loss at oblique incidence was measured in the same manner as in Example 1. The results are shown in Table 1.

Example 4 46.1 parts by weight of calcined gypsum, 40 parts by weight of water, Mn-Mg-Z
A slurry was prepared by mixing 53.9 parts by weight of n ferrite powder and 2.0 parts by weight of perlite with a mixer.
A gypsum board base paper is placed on a strong magnet sheet having a striped magnetized pattern with a gap of 5 mm, and the obtained slurry is spread on the gypsum board base paper to adjust the film thickness. The base paper was stacked and dried by heating at 100 ° C. to obtain an electromagnetic wave absorbing layer in which ferrite powder was unevenly distributed. The obtained electromagnetic wave absorbing layer had a thickness of 9.5 mm and a specific gravity of 1.10. Also, on the surface of the obtained electromagnetic wave absorbing layer in contact with the magnet sheet, a stripe pattern with a gap of 5 mm, which was considered to be formed by ferrite, could be observed. When the obtained electromagnetic wave absorbing layer was heated to measure the content of gypsum crystal water, the hydration rate of calcined gypsum was 17%. The transmission attenuation of the obtained electromagnetic wave absorbing material at normal incidence was measured.

Measurement of Transmission Attenuation at Normal Incident The electromagnetic wave absorbing ability as an electromagnetic wave absorbing material was measured as the transmission attenuation at normal incidence of electromagnetic waves. Network analyzer (Hewlett Packard 8510D)
And a double rigid antenna or a horn antenna, and a frequency of 1.9 GHz, 2.45 GHz, 19 GHz
Measurements were made by a measurement method (H method) in which the electric field was perpendicular to the stripe pattern and the magnetic field was parallel to z (H method), and a measurement method (V method) in which the electric field was parallel to the stripe pattern and the magnetic field was perpendicular to the stripe pattern. Are shown in Table 2.

Example 5 72.4 parts by weight of calcined gypsum, 65.1 parts by weight of water, Mn-Mg
27.0 parts by weight of Zn ferrite powder, 0.06 parts by weight of coal pitch-based carbon fiber (fiber diameter 10 μm × 6 mm), and 0.6 parts by weight of a styrene balloon having an average particle diameter of 3 mm are mixed by a mixer and slurry. And an electromagnetic wave absorbing layer in which ferrite powder was unevenly distributed was obtained in the same manner as in Example 1. The obtained electromagnetic wave absorbing layer has a thickness of 12.
5 mm, and the specific gravity was 1.00. In addition, the surface of the obtained electromagnetic wave absorbing layer in contact with the magnet sheet,
A stripe pattern of a 7 mm gap, which was considered to be formed by ferrite, was observed. The transmission attenuation at normal incidence was measured in the same manner as in Example 4. The results are shown in Table 2.

Comparative Example 3 An electromagnetic wave absorbing layer was obtained in the same manner as in Example 4 except that the uneven distribution treatment was not performed. The obtained electromagnetic wave absorbing layer had the same thickness and specific gravity as the electromagnetic wave absorbing layer of Example 4. The transmission attenuation at normal incidence was measured in the same manner as in Example 4. The results are shown in Table 2.

Comparative Example 4 An electromagnetic wave absorbing layer was obtained in the same manner as in Example 5 except that the uneven distribution treatment was not performed. The obtained electromagnetic wave absorbing layer had the same thickness and specific gravity as the electromagnetic wave absorbing layer of Example 5. The transmission attenuation at normal incidence was measured in the same manner as in Example 4. The results are shown in Table 2.

Example 6 Vinyl chloride resin (Zeon 121, manufactured by Zeon Corporation) 10
0 parts by weight, 40 parts by weight of DOP as a plasticizer, 40 parts by weight of volatile plasticizer TXIB (Texanol isobutyrate, manufactured by Eastman Chemical Company), 4 parts by weight of a heat stabilizer, Mn
-The thickness of the polyvinyl chloride sol paint consisting of 160 parts by weight of Mg-Zn ferrite powder is applied on a galvanized steel plate fixed on a device (electromagnetic chuck) that can fix the coated plate with an electromagnet so as not to move. It was painted so as to be 2 mm. On the painted plate, a two-dimensional uneven distribution pattern due to the distribution of the magnetic powder according to the magnetization pattern of the fixing electromagnet was formed. After coating, the coating was dried by heating at 200 ° C. to obtain an unevenly distributed electromagnetic wave absorbing material comprising an electromagnetic wave absorbing layer and an electromagnetic wave reflecting layer in which ferrite powder was unevenly distributed. The thickness of the obtained electromagnetic wave absorbing layer was 1.6 mm. The return loss was measured in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 5 Example 6 except that the fixing electromagnet was not operated.
An electromagnetic wave absorbing material was obtained in the same manner as described above. The obtained electromagnetic wave absorbing material had the same thickness and specific gravity as the electromagnetic wave absorbing material of Example 6. The return loss at oblique incidence was measured in the same manner as in Example 1. The results are shown in Table 1.

[0110]

[Table 1]

[0111]

[Table 2]

[0112]

Since the electromagnetic wave absorbing material of the present invention has the above-described structure, it can absorb electromagnetic waves in a wide frequency band, is lightweight, is excellent in workability for installation as a building material, and is easy to fit in, and is an intelligent office. It can be suitably used as an indoor building material used for ceilings and walls.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of a state in which a concentration distribution of a magnetic powder in a depth direction is unevenly distributed in an electromagnetic wave absorbing layer of an electromagnetic wave absorbing material of the present invention.

FIG. 2 is a schematic view showing an example of a state in which the concentration distribution in the planar direction of the magnetic powder in the electromagnetic wave absorbing layer of the electromagnetic wave absorbing material of the present invention is unevenly distributed.

FIG. 3 is a schematic diagram showing an example of a state in which a concentration distribution of a magnetic substance powder in a planar direction is unevenly distributed in an electromagnetic wave absorbing layer of the electromagnetic wave absorbing material of the present invention.

FIG. 4 is a schematic view showing an example of a state in which the concentration distribution of the magnetic powder in the depth direction and the plane direction is unevenly distributed in the electromagnetic wave absorbing layer of the electromagnetic wave absorbing material of the present invention.

FIG. 5 is a schematic view showing an electromagnetic wave absorbing layer in which magnetic powder is unevenly distributed using a magnet sheet composed of a circular pattern unit.

FIG. 6 is a schematic diagram showing an electromagnetic wave absorbing layer in which magnetic powder is unevenly distributed using a magnet sheet composed of linear pattern units.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electromagnetic wave absorption layer 2 Magnetic substance powder 2a Magnetic substance uneven distribution part 3a, 3b Magnet sheet

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Junichi Haneda 928 Takamatsu, Kawagoe-cho, Mie-gun, Mie Prefecture, Japan (72) Inventor Takumi 928 Takamatsu, Kawagoe-cho, Mie-gun, Mie Prefecture, Chiyodaute Corporation

Claims (11)

[Claims] 1. A binder (a) and a magnetic powder (b)
In an electromagnetic wave absorbing material comprising an electromagnetic wave absorbing layer consisting of
An electromagnetic wave absorbing material, wherein the magnetic powder (b) is unevenly distributed in the electromagnetic wave absorbing layer. 2. The electromagnetic wave absorbing material according to claim 1, wherein the magnetic powder (b) shows a distribution in which the concentration distribution in the depth direction of the electromagnetic wave absorbing layer is biased. 3. The electromagnetic wave absorbing material according to claim 1, wherein the magnetic powder (b) shows a distribution in which the concentration distribution in the planar direction is biased in the electromagnetic wave absorbing layer. 4. The electromagnetic wave absorbing material according to claim 1, wherein the magnetic powder (b) shows a distribution in which the concentration distribution in the depth direction and the concentration distribution in the plane direction of the electromagnetic wave absorbing layer are biased. 5. The electromagnetic wave absorbing material according to claim 3, wherein the magnetic substance powder (b) is unevenly distributed in the electromagnetic wave absorbing layer based on a specified pattern. 6. A binder (a) and a magnetic powder (b)
In the electromagnetic wave absorbing layer, the blending amount of the binder (a) is 45 to 90 parts by weight based on 100 parts by weight of the total of the binder (a) and the magnetic substance powder (b).
The blending amount of the magnetic powder (b) is 55 to 10 parts by weight based on 100 parts by weight of the total of the binder (a) and the magnetic powder (b).
Is gypsum or calcium silicate,
4. The electromagnetic wave absorbing material according to 4 or 5. 7. The electromagnetic wave absorbing material according to claim 1, further comprising an electromagnetic wave reflecting layer. 8. A binder (a) and a magnetic powder (b)
In an electromagnetic wave absorbing material comprising an electromagnetic wave absorbing layer consisting of
The magnetic powder (b) is a method for producing the electromagnetic wave absorbing material which is unevenly distributed in the electromagnetic wave absorbing layer. When forming the electromagnetic wave absorbing layer, an external force is applied to the magnetic powder (b). A method for producing an electromagnetic wave absorbing material, characterized in that the material is caused to act to be unevenly distributed. 9. The method for producing an electromagnetic wave absorbing material according to claim 8, wherein the magnetic substance powder (b) is settled by the action of gravity. 10. The method for producing an electromagnetic wave absorbing material according to claim 8, wherein the magnetic powder (b) is unevenly distributed by applying a magnetic force. 11. The method for producing an electromagnetic wave absorbing material according to claim 10, wherein a magnetic force acts by forming a planar magnetic force pattern.