JPH0936587A - Flame-retardant low-reflectance material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flame-retardant low-reflectance material formed of thin wide-band electromagnetic wave absorbing material which is flame-retardant and capable of uniformly absorbing wide-band electromagnetic waves that range from quasi-microwave to millimeter wave. SOLUTION: A flame-retardant low-reflectance material is composed of a first layer of conductive material, a second layer of metal oxide magnetic fine powder and binder, a third layer of metal magnetic fine powder and binder, and a fourth layer of flame-retardant inner material.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a flame-retardant low-reflecting material.

[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.

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 resin is generally known, and during processing, along with the magnetic and dielectric characteristics of the composite, depending on the target frequency,
Achieves a large absorption by precisely controlling the thickness. However, such an electromagnetic wave absorber cannot uniformly absorb any of widely separated frequency bands such as the quasi-microwave band, the quasi-millimeter wave band, and the millimeter wave band. With the expansion of the use of the microwave band and the quasi-millimeter wave band, related industries are required to develop an electromagnetic wave absorbing material that uniformly absorbs all 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 Laid-Open No. 3-36795 discloses a radio wave absorbing material capable of absorbing in a wide band by controlling the spin orientation of the sintered ferrite by changing the magnetic strength of the lower hard ferrite layer to change the complex magnetic permeability. Is disclosed. However, in order to enable absorption of electromagnetic waves in a wide band by changing the complex magnetic permeability by a magnetic force, matching in which the thickness of ferrite is controlled is required, and a strong and heavy magnet is required. In addition, the effect of retaining the absorption capability of the electromagnetic wave absorbing material in a wide band is not actually large.

Therefore, as an electromagnetic wave absorbing material that can be used in a wide band, a first layer made of a conductive material, and a second layer made of a fine powder of a metal oxide magnetic material and a binder, which are sequentially laminated on the first layer. A multi-layer type electromagnetic wave absorbing material having a third layer composed of a metal magnetic fine powder and a binder has been proposed.

1 by the electromagnetic wave absorbing material having this structure
Electromagnetic wave absorption having a stable low reflection and absorption capability in a wide band of ６０60 GHz has become possible. This second layer is composed of a fine powder of metal oxide magnetic material and a binder, and is disclosed in JP-A-3-3
Unlike the sintered ferrite plate disclosed in Japanese Patent No. 6795, the absorption is generally small, but the degree of freedom for matching is high. Intelligent office wall,
If the ceiling and floor are surrounded by such a low-reflecting material, even if a communication system using broadband electromagnetic waves from the quasi-microwave band to the quasi-millimeter wave band and the millimeter wave band is operated in the office, There are no problems such as mutual interference of electromagnetic waves, interference due to delay dispersion, and malfunction.

However, since such an electromagnetic wave absorbing material is used as a wallpaper surrounding walls, ceilings and floors in an intelligent office, it must have flame retardancy or noncombustibility as a building material in case of fire. I have to.

[0009]

In view of the above, the present invention uniformly absorbs electromagnetic waves in a wide band from the quasi-microwave band to the millimeter wave band, and is thin and flame-retardant. An object of the present invention is to provide a flame-retardant low-reflecting material using.

[0010]

The gist of the present invention is that the flame-retardant low-reflecting material comprises a first layer made of a conductive material, and a second layer made of a metal oxide magnetic fine powder and a binder. It has a third layer composed of fine powder of a metal magnetic material and a binder, and a fourth layer which is a flame-retardant interior material. Hereinafter, the present invention will be described in detail.

The first layer of the flame-retardant low-reflection material of the present invention is made of a conductive material. The first layer can also serve as a support. The conductive material has a shielding ability of 20 dB or more, preferably 30 d, due to its conductivity.
There is no particular limitation as long as it is a material that provides B or more, and examples thereof include metal plates such as copper, aluminum, steel, iron, nickel, stainless steel and brass; metal plates plated with these metals; wire mesh; metal cloth; Aluminum on the iron plate,
Examples thereof include plated steel plates plated with zinc, copper, etc. by heat or electricity. Such a conductive material may be one that has been subjected to a surface treatment or a primer treatment for improving interlayer adhesion, such as a precoated steel sheet.

The first layer is a non-conductive material such as a plastic material provided with a conductive coating film containing a metal used as the conductive material and a binder; A material having an electrolytic plating layer formed thereon; a metallized material having a vapor deposition layer such as aluminum formed thereon may be used.

The thickness of the first layer is preferably 50 μm to 3 mm. When it is less than 50 μm, the mechanical strength of the first layer is reduced, and when it exceeds 3 mm, the weight of the first layer becomes heavy, which is not practical.

The second layer of the flame-retardant low-reflecting material of the present invention comprises a fine powder of metal oxide magnetic material and a binder. In the present specification, the "metal oxide magnetic fine powder" is a magnetic fine powder containing a metal oxide (for example, iron oxide etc.) as a main component, and the metallic magnetic fine powder described later is It is different. The metal oxide magnetic fine powder is not particularly limited, and examples thereof include Mn-Zn ferrite, Ni-Zn ferrite, Mn-Mg-Zn ferrite, Li ferrite,
Examples thereof include Mn-Cu-Zn ferrite, Ba ferrite, Sr ferrite and the like. Among them, Mn-Z
n ferrite, Ni-Zn ferrite, Mn-Mg-Z
N-ferrite and the like are preferable. Particularly preferred is a particle size of 1
It is a 0 to 20 μm Mn-Zn ferrite. The average particle diameter of the metal oxide magnetic fine powder is preferably 1 to 50 μm. If it is less than 1 μm, the electromagnetic wave absorbing ability is insufficient and the productivity is lowered. If it exceeds 50 μm, there is a problem that the electromagnetic wave absorbing ability is insufficient and the manufacturing equipment is worn. More preferably, it is 5 to 20 μm. The metal oxide magnetic fine powder may be surface-treated with a silane coupling agent, a titanium coupling agent, or the like, if necessary, in order to improve the productivity and the physical properties.

The compounding amount of the above-mentioned fine powder of metal oxide magnetic material is
In the second layer, 85 to 92% by weight is preferable. When it is less than 85% by weight, the electromagnetic wave absorbing ability and flame retardancy are lowered, and when it exceeds 92% by weight, the electromagnetic wave absorbing ability is good, but the rigidity, durability and the like are poor and the weight is heavy. Therefore, it becomes less practical as an electromagnetic wave absorbing material. More preferably,
90% by weight.

The binder constituting the second layer is not particularly limited, and examples thereof include organic polymer materials such as thermoplastic resins and thermosetting resins; inorganic ceramic materials such as cement-based, calcium-based and gypsum-based materials. Can be mentioned. A thermoplastic resin is preferable as the organic polymer material. The thermoplastic resin is not particularly limited, and examples thereof include non-polar resins such as polyethylene, polypropylene, polymethylpentene, polybutene, polystyrene, polybutadiene, crystalline polybutadiene, and styrene butadiene; polyvinyl chloride, polyvinyl acetate, polymethyl methacrylate. , Polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride,
Polytetrachloroethylene, ethylene-vinyl acetate copolymer, 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-acrylonitrile copolymer resin (AS
A 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,
Resins such as polyetheretherketone resin and polyetherimide resin; modified resins thereof and the like can be mentioned. These may be used alone or in combination of two or more.

The oxygen index of the organic polymer material is preferably 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 above organic polymer materials, as the resin having a high oxygen index, 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, modified chlorinated polyethylene, and silicone resin are preferable.

The inorganic ceramic material is not particularly limited, and examples thereof include calcium sulfate, calcium silicate, water glass, Portland cement, alumina cement, alumina silicate, calcium oxide, clay and the like. Of these, calcium sulfate, calcium silicate, Portland cement, and alumina cement are preferable.

As the above-mentioned binder, the wettability with the metal oxide magnetic fine powder, the viscosity at the time of kneading the resin, the temperature, the physical properties of the film, the chemical resistance, the heat resistance, the water resistance, the compatibility with the metal and the plastic. It can be appropriately selected in consideration of adhesiveness and the like.

When the fine powder of metal oxide magnetic material and the binder are blended, a plasticizer, a viscosity modifier, and a plasticizer may be added, if necessary, in order to improve layer formation, coatability, electromagnetic wave absorption ability and the like. Surface active agents, flame retardants, lubricants, defoamers, heat stabilizers, antioxidants and the like may be added.

In the formation of the second layer, when an organic polymer material is used as a binder, a commonly used method such as extrusion molding or pressure molding, a suitable amount of diluent is added to form a paint, and a thick film coating is performed. The layer can be formed by a method such as When an inorganic ceramic material is used, a layer can be formed by a papermaking method, a molding method, an extrusion molding method, or the like.

The thickness of the second layer is 1.8 to obtain a practical low reflection sheet showing an electromagnetic wave absorption rate of more than 75% in the quasi-microwave band to the quasi-millimeter wave band.
3.6 mm is preferred. If it is less than 1.8 mm, the absorption capacity in the quasi-microwave band is reduced, and if it exceeds 3.6 mm, not only the material becomes expensive, but also the weight becomes heavy, which is not preferable in practice. More preferably 2.2-
3.2 mm.

The third layer of the flame-retardant low-reflecting material of the present invention comprises fine metal magnetic powder and a binder. The metal magnetic material forming the fine powder of metal magnetic material is not particularly limited, and examples thereof include a magnetic metal simple substance material and a magnetic metal alloy. The magnetic metal simple substance material is not particularly limited, and examples thereof include Fe, Ni, and Co. The magnetic metal alloy is not particularly limited and includes, for example, silicon steel; sendust; super sendust; permalloy; amorphous metal; Si, Al, Co, Ni,
Examples thereof include an iron magnetic alloy containing at least one metal element selected from the group consisting of V, Sn, Zn, Pb, Mn, Mo and Ag.

In addition to the above, Fe powder having an Fe purity of 85 to 98% by weight can also be used. When the purity of Fe is less than 85% by weight, the electromagnetic wave absorbing ability is low, and when it exceeds 98% by weight, the flammability is high. Preferably, it is a carbonyl iron powder or a magnetic alloy powder containing 80% by weight or more of iron produced by the atomizing method. Considering flame retardancy and nonflammability, high-purity Fe powder is not preferable. The metal magnetic fine powder may be surface-treated with a silane coupling agent, a titanium coupling agent, or the like, if necessary.

The particle size of the fine metal magnetic powder is not particularly limited as long as it can be uniformly mixed with the binder, but the average particle size is preferably 1 to 30 μm. If it is less than 1 μm, the flame retardancy is lowered, and if it exceeds 30 μm, sufficient electromagnetic wave absorbing ability is not exhibited. More preferably, it is 2 to 20 μm.

The compounding amount of the above-mentioned fine powder of metal magnetic material is 70-
90% by weight is preferred. When it is less than 70% by weight, the electromagnetic wave absorbing ability and flame retardancy are lowered, and when it exceeds 90% by weight, the electromagnetic wave absorbing ability is good, but the rigidity, durability and the like are poor and the weight is heavy. Therefore, it becomes less practical as an electromagnetic wave absorbing material. More preferably, it is 75 to 90% by weight.

The binder forming the third layer is not particularly limited, and the same binder as used in forming the second layer can be used. Also, the second layer formation
It can be performed in the same manner as the layer. When blending the metal magnetic fine powder and the binder, in order to improve layer formation, coatability, electromagnetic wave absorption, etc., a plasticizer, if necessary,
Viscosity modifiers, surface active agents, flame retardants, lubricants, defoamers, heat stabilizers, antioxidants and the like may be added.

The thickness of the third layer is 0.2 to obtain a practical low reflection sheet showing an electromagnetic wave absorption rate of more than 75% in the quasi-microwave band to the quasi-millimeter wave band.
1.1 mm is preferable. Even if it is less than 0.2 mm,
Even if it exceeds 1.1 mm, the ability to absorb the quasi-millimeter wave band and the millimeter wave band is lowered. More preferably, 0.3-
0.8 mm. In order to provide a light and thin electromagnetic wave absorbing material, the total thickness of the second layer and the third layer should be 4
It is preferable to set it to mm or less.

The flame retardancy of the second layer and the third layer can be designed by selecting a binder or a flame retardant, and the metal oxide magnetic fine powder or the metal magnetic fine powder and the binder or It is required as the performance in the state of being formed into a film or sheet by blending other additives. The second layer and the third layer preferably have an oxygen index of 30 or more in the film itself or the sheet itself. When it is less than 30, the flammability is high and sufficient flame retardancy is not exhibited even when combined with the fourth layer. More preferably, it is 35 or more.

The fourth layer of the flame-retardant low-reflection material of the present invention is a flame-retardant interior material. The flame-retardant interior material is preferably a fireproof board or fireproof sheet made of at least one of an inorganic binder and an organic binder. The inorganic binder is not particularly limited, and examples thereof include calcium sulfate, calcium silicate, water glass, Portland cement, alumina cement, alumina silicate, calcium oxide, and clay. The organic binder is not particularly limited, and examples thereof include vinyl chloride resin, silicone resin, chlorinated polyethylene resin and the like.

The fireproof board made of the above-mentioned inorganic binder is not particularly limited, and examples thereof include asbestos slate board, asbestos cement perlite board, gypsum board, rock wool sealing board, light cal board, cement board, asbestos cement calcium silicate board, Asbestos cement siding, wood wool cement board, pulp cement board, wood chip cement board, interior plastic decorative boards, makeup hard fiber board, soft fiber board, medium fiber board, hard fiber board, particle board, makeup particle board, makeup Examples include gypsum board, sheathing gypsum board, reinforced gypsum board and the like. The fireproof board may contain an inorganic flame retardant. The thickness of the fireproof board made of the inorganic binder is preferably 3 to 25 mm from the viewpoint of flame retardancy and electromagnetic wave absorption.
If it is less than 3 mm, the effect on flame retardancy and electromagnetic wave absorption is small, and if it exceeds 25 mm, the board may be broken or cracked during mounting or transportation. More preferably, it is 9 to 25 mm.

The fireproof board or fireproof sheet made of the above organic binder is formed by combining the above organic binder with a plasticizer, an inorganic filler, glass fiber, a flame retardant and the like. The fireproof board or fireproof sheet made of the above organic binder is not particularly limited, and examples thereof include flame-retardant plywood and F
An RP plate etc. can be mentioned. The fireproof board or fireproof sheet made of the above organic binder has a thickness of 50 μm to
5 mm is preferable. When it is less than 50 μm, the effect on flame retardancy and electromagnetic wave absorption is small, and when it exceeds 5 mm,
Problems occur in terms of workability in mounting, weight, and warpage.

The flame-retardant interior material may be a fire wall material. The fire wall material is not particularly limited,
For example, a paper wallpaper, a woven wallpaper, a vinyl wallpaper, a chemical fiber wallpaper, an inorganic wallpaper, a specific wallpaper, etc., which are certified as wall covering materials can be mentioned. The material for forming these is not particularly limited, and examples thereof include organic polymer materials such as vinyl chloride resin, silicone resin, and chlorinated polyethylene resin used as a binder for the second layer, paper, cellulose paper, and a plasticizer, In combination with an inorganic filler, glass fiber, flame retardant, etc .; and in combination with an inorganic ceramic material used as a binder for the second layer and an inorganic filler, glass fiber, flame retardant, etc. You can The thickness of the above fire wall material is preferably 50 μm to 2 mm. 5
When it is less than 0 μm, the effect on flame retardancy and electromagnetic wave absorption is small, and when it exceeds 2 mm, flame retardation becomes difficult and mounting workability is deteriorated.

The above fire wall material is not only used as it is laminated on the third layer, but also used as a flame-retardant interior material is a fire board or sheet made of at least one of an inorganic binder and an organic binder. In the fourth layer,
It may be further stacked and used as the fifth layer. When the above fire wall material is used as the fifth layer, the electromagnetic wave absorbing ability in the TE mode or the TM mode can be improved by combining with the fourth layer. In particular, it is more effective if the fourth layer is a fireproof board made of an inorganic binder.

In the flame-retardant low-reflection material of the present invention, at least one of the binder forming the second layer and the binder forming the third layer is preferably an inorganic ceramic material.
When an inorganic ceramic material is used as the binder, the flame retardancy of the obtained low reflection material can be increased.

In the flame-retardant low-reflection material of the present invention, at least one of the binder forming the second layer and the binder forming the third layer is preferably an organic polymer material. When an organic polymer material is used as the binder, it is possible to enhance the flame retardancy of the obtained low reflective material. When the organic polymer material having an oxygen index of 30 or more is used, the flame retardancy can be further enhanced.

In the present invention, the second flame-retardant low-reflecting material layer is used.
A flame retardant may be further added to at least one of the layer and the third layer in order to impart flame retardancy and nonflammability. The flame retardant is not particularly limited, and for example, (1) amines that stop the chain reaction of oxidative combustion,
Phenols, chlorine compounds, bromine compounds; (2) phosphorus compounds and boron compounds that block air and prevent contact between oxygen and combustible gas; (3) water, carbon dioxide, which dilutes the combustible gas to reduce heat generation. Inert gas generator such as ammonia;
(4) Hydroxides, hydrates, silica, alumina, etc. that lower the temperature of combustibles to prevent decomposition and ignition can be mentioned. More specifically, as the flame retardant, for example, hexabromobenzene, decabromobenzyl phenyl ether, decabromobenzyl phenyl oxide,
Tetrabromobisphenol, tetrabromophthalic anhydride, tetrabromobisphenol A, tricresyl phosphate, triphenyl phosphate, triallyl phosphate, trichloroethyl phosphate, halogen-containing condensed phosphate ester, chlorinated paraffin, perchloropentacyclodecane, aluminum hydroxide , Magnesium hydroxide, antimony trioxide, antimony pentoxide, zinc borate, ammonium bromide, titanium phosphate and the like. The blending amount of the flame retardant is preferably 0.01 to 15% by weight in the second layer and the third layer. 0.01% by weight
If it is less than 1, the flame retardancy of the resulting low-reflecting material is not sufficient, and if it exceeds 15% by weight, the amount of the binder decreases and the physical properties of the sheet deteriorate, and if the amount of the binder is supplemented, the magnetic substance becomes The electromagnetic wave absorption capacity decreases.

In the present invention, the flame-retardant low-reflecting material is made flame-retardant by (a) the flame-retardant interior material which constitutes the fourth layer, and (b) the binder which constitutes the second layer. And at least one of the binders forming the third layer is a polymer having an oxygen index of 30 or more, and (c) the metal oxide magnetic fine powder forming the second layer and the third layer are formed. Depending on the type, particle size, particle size distribution and amount of fine metal magnetic powder, or (d) at least one of the second and third layers
When the flame-retardant low-reflection material of the present invention is installed on a wall, ceiling, floor, etc. of an office, etc., the fourth layer is a surface layer. ) The selection of the flame-retardant interior material forming the fourth layer is particularly important.

The flame-retardant low-reflection material of the present invention can be manufactured, for example, by the following method. A mixture of fine powder of metal oxide magnetic material and a binder is kneaded, rolled by a hot press, and then formed into a sheet by a hot roll. A plate or the like of the first layer made of a conductive material is brought into close contact with the obtained sheet to obtain a laminate of the first layer and the second layer. Next, a mixture of the fine magnetic powder of metal and the binder is formed into a sheet on the second layer and coated to form the third layer. The flame-retardant low-reflecting material of the present invention is obtained by further stacking a fireproof board or the like on it.

In the flame-retardant low-reflection material of the present invention, the second
The layer, the third layer, and the fourth layer must be laminated on the first layer in this order. If this order is changed, the electromagnetic wave absorbing ability becomes insufficient.

Since the flame-retardant low-reflecting material of the present invention has functions of heat insulation, soundproofing, fireproofing, rustproofing, waterproofing, designability, etc. in addition to electromagnetic wave absorbing ability and flame retardancy, it is, for example, intelligent. It can be suitably used as an indoor building material with extremely high added value for offices and the like and as an outer wall building material. Further, the flame-retardant low-reflecting material of the present invention can manufacture an absorber that selectively absorbs a specific frequency by adjusting the thicknesses of the second layer and the third layer. Useful for maintenance.

According to the idea of the distributed constant circuit, the absorption amount increases as the field impedance of the outermost surface of the absorber becomes closer to the characteristic impedance of space. The field impedance of the outermost surface of the absorber is determined by the electromagnetic characteristics and thickness of the layer forming the absorber, and further by the frequency of electromagnetic waves. The present invention
This is a technique for making the field impedance close to the characteristic impedance of space in a very distant frequency band such as quasi-microwave band, quasi-millimeter wave band, and millimeter wave band.

[0043]

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 MnO, ZnO and Fe ₂ O _{3 in a} molar ratio of 32:14:54
90 parts by weight of ferrite fine particles having an average particle size of 15 μm including and ethylene-vinyl acetate copolymer EVA (SUMI
10 parts by weight of TATE RB-11, manufactured by Sumitomo Chemical Co., Ltd.) is kneaded by a test roll set at 110 ° C., and the kneaded body is further rolled by a hot press at 110 ° C., and then 2.5 mm by a hot roll at 140 ° C. Was formed into a sheet. The obtained sheet was adhered to an aluminum foil to obtain a laminate of the first layer and the second layer. Then, 85 parts by weight of carbonyl iron having an average particle diameter of 3.5 μm (HL grade, manufactured by BASF) and ethylene-vinyl acetate copolymer EVA (SUMITATE RB
-11, manufactured by Sumitomo Chemical Co., Ltd.) in a similar manner to form a sheet having a thickness of 0.5 mm on the second layer to form a third layer. A gypsum board with a thickness of 11 mm was selected as the fourth layer and was laminated on the third layer to obtain a flame-retardant low-reflection material.

Radio wave absorptivity test at normal incidence In order to measure the absorptivity when electromagnetic waves are vertically incident on a low-reflecting material, the panel was processed so that it could be measured by TEM and put in a 7 mm hollow coaxial tube. Then, the return loss was measured by a network analyzer. The results are shown in Table 1. Radio wave absorption test at oblique incidence The return loss at 45 ° oblique incidence of electromagnetic waves was measured at a frequency of 1.9 GHz, 2.45 GHz and 19 GHz using a near electromagnetic field antenna measuring device (NFAMS, manufactured by Icom Co., Ltd.).
Measurements were made in TE mode and TM mode, and the results are shown in Table 2. As a result, it was confirmed that it has a function as a good low reflection material. A Gunn diode is used as a radio wave absorption test oscillator at 60 GHz, and the flame-retardant low-reflection panel obtained is installed in a waveguide so that TEM is incident on the laminated surface, and a mixer is used. When the return loss was measured at 60 GHz with a spectrum analyzer, it was 12.5 dB.

Flame Retardancy Test The flame retardancy test of the low reflection material was carried out using a surface test apparatus specified by Ministry of Construction Notification No. 3415, and the combustion resistance of the surface of the low reflection material was observed. After heating for 10 minutes according to the standard heating curve, the surface of the low-reflecting material did not burn or melt after heating, and showed good combustion resistance.

Comparative Example 1 A low reflection material was prepared in the same manner as in Example 1 except that the fourth layer gypsum board was not used, and an electromagnetic wave absorption test and a flame retardancy test were conducted. The electromagnetic wave absorbing ability is shown in Tables 1 and 2. The electromagnetic wave absorption ability was inferior to that of Example 1.
Also, in the flame retardancy test, the surface was burned after the test.

Example 2 MnO, ZnO and Fe ₂ O _{3 in a} molar ratio of 32:14:54.
90 parts by weight of ferrite fine particles having an average particle diameter of 13 μm containing, 10 parts by weight of vinyl chloride resin (Zeon 121, manufactured by Nippon Zeon Co., Ltd.), 3 parts by weight of DOP as a plasticizer, and an appropriate amount of heat stabilizer were set at 150 ° C. After melt-kneading with a test roll and rolling the kneaded body with a hot press at 110 ° C., 1
A hot roll at 40 ° C. was used to form a 2.5 mm sheet. The oxygen index of the obtained sheet was 42. Then, this sheet was adhered to an aluminum foil to obtain a laminate of the first layer and the second layer. Furthermore, 85 parts by weight of carbonyl iron (HL grade, manufactured by BASF) having an average particle diameter of 3.5 μm and chlorinated polyethylene (Eraslen 303A, manufactured by Showa Denko KK) 1
0.5 mm on the second layer in the same manner with 5 parts by weight
Was formed into a sheet having a thickness of 3 and was coated to form a third layer. This third
The oxygen index of the layered sheet was 32. Asbestos barlite having a thickness of 9.5 mm was selected as the fourth layer and was laminated on the third layer to obtain a flame-retardant low-reflecting material. The electromagnetic wave absorbing ability is shown in Tables 1 and 2. The flame retardancy test had good flame retardancy.

Example 3 Molar ratio 5:12: surface-treated with silane coupling agent
At 14:69, 88 parts by weight of ferrite fine particles containing MnO, MgO, ZnO and Fe ₂ O ₃ and having an average particle diameter of 10 μm and vinyl chloride resin (Zeon 121, manufactured by Nippon Zeon Co., Ltd.) 1
0 parts by weight, 3 parts by weight of plasticizer, 5 parts by weight of antimony trioxide, and 5 parts by weight of heat stabilizer were melt-kneaded with a test roll set at 150 ° C., and the kneaded body was further heated to 110 parts.
Rolled with a hot press at 140 ° C and then with a hot roll at 140 ° C.
It was formed into a 5 mm sheet. The oxygen index of the obtained sheet was 44. Then, this sheet was adhered to an aluminum foil to obtain a laminate of the first layer and the second layer. Furthermore, silicon steel powder (Fe: Si = 94: 6) 85 having an average particle size of 10 μm is used.
Kneading was performed in the same manner by using 15 parts by weight, 15 parts by weight of chlorinated polyethylene (Eraslen 303A, manufactured by Showa Denko KK), and 5 parts by weight of tetrabromobisphenol, to a thickness of 0.5 mm on the second layer. It was made into a sheet and covered to form a third layer. The oxygen index of the third layer sheet was 40.
Asbestos slate with a thickness of 9.5 mm is selected as the fourth layer,
A flame-retardant low-reflecting material was obtained by stacking on the third layer. The electromagnetic wave absorbing ability is shown in Tables 1 and 2. The flame retardancy test had good flame retardancy.

Example 4 After obtaining a laminate of the first layer and the second layer in the same manner as in Example 3, the binder for the third layer was changed from chlorinated polyethylene to silicone resin (SH9551, Toray Dow Corning Silicone Co., Ltd.). Manufactured), and the third layer mixture was kneaded and formed into a sheet having a thickness of 0.5 mm at room temperature to form a third layer. The oxygen index of this sheet was 38. 9.5mm as the 4th layer
Asbestos cement with a thickness of 1 was selected and laminated on the third layer to obtain a flame retardant low reflection material. The electromagnetic wave absorbing ability is shown in Tables 1 and 2. The flame retardancy test had good flame retardancy.

[0051]

[Table 1]

[0052]

[Table 2]

Example 5 In Example 2, asbestos perlite was further coated with vinyl wallpaper that passed the certification test of wall covering material No. 0003 consisting of vinyl chloride resin, plasticizer, heat stabilizer, and flame retardant. Attached to obtain a flame-retardant low-reflecting material. This material also had good flame retardancy.

Example 6 In Example 2, a vinyl which passed the certification test of wall covering material No. 0003 consisting of a vinyl chloride resin, a plasticizer, a heat stabilizer and a flame retardant in place of the asbestos perlite of the fourth layer. A flame-retardant low-reflecting material was obtained using wallpaper. This material also had good flame retardancy.

[0055]

Since the flame-retardant low-reflecting material of the present invention has the above-mentioned structure, it can uniformly absorb electromagnetic waves in a wide band from the quasi-microwave band to the millimeter wave band, and it is thin and difficult It is flammable and can be suitably used as an indoor building material such as a wallpaper attached to a wall or the like and an external wall building material.

Claims (6)

[Claims] 1. A first layer made of a conductive material, a second layer made of a metal oxide magnetic fine powder and a binder, a third layer made of a metal magnetic fine powder and a binder, and flame retardant. A flame-retardant low-reflection material having a fourth layer as an interior material. 2. The flame-retardant low-reflection material according to claim 1, wherein the flame-retardant interior material is a fire-proof board or fire-proof sheet made of at least one of an inorganic binder and an organic binder. 3. The flame-retardant low-reflection material according to claim 1, wherein the flame-retardant interior material is a fire wall material. 4. The flame-retardant low-reflection material according to claim 1, 2 or 3, wherein at least one of the binder forming the second layer and the binder forming the third layer is an inorganic ceramic material. 5. The flame-retardant low-reflecting material according to claim 1, wherein at least one of the binder forming the second layer and the binder forming the third layer is an organic polymer material. 6. The method according to claim 1, wherein at least one of the second layer and the third layer further contains a flame retardant.
The flame-retardant low-reflecting material according to 2, 3, 4 or 5.