JPH0923087A - Low reflection sheet for office use and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low reflection sheet for office use which uses wideband electromagnetic wave absorbing thin material which absorbs electromagnetic waves in the region from the pseudo-microwave band to the millimetric wave band, and is easily installed on a metal surface. SOLUTION: This sheet has a first layer composed of hard ferrite and binder, a second layer composed of conductive material, a third layer composed of fine powder of metal oxide magnetic material and binder, and a fourth layer composed of fine powder of metal magnetic material and binder.

Description

Detailed Description of the Invention

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a low reflection sheet for office use and a method for manufacturing the same.

[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.

Frequency bands used in communication systems include quasi-microwave bands of 1.9 GHz band and 2.45 GHz band, quasi-millimeter wave band of 19 GHz band and 60 GHz.
Communication in the millimeter wave band is about to be put to practical use.
Furthermore, in other countries, 900MHz band and 5.7GH
The z band is also put to practical use for wireless LAN. The quasi-microwave band is a personal handyphone system (PHS).
In addition, the indoor wireless device of the medium speed wireless LAN and the quasi-millimeter wave band and the millimeter wave band are applied to the indoor wireless device of the 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, in such an electromagnetic wave absorber, it is not possible to equally absorb frequency bands that are widely separated, such as the quasi-microwave band, the quasi-millimeter wave band, and the millimeter wave band, and the quasi-microwave band as described above Along with the expansion of use of the quasi-millimeter wave band, related industries are required to develop an electromagnetic wave absorbing material that absorbs the quasi-microwave band and the millimeter wave band equally. 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 radio waves up to the quasi-microwave band, quasi-millimeter wave band and millimeter wave band is performed in the office, the mutual interference of the electromagnetic waves described above will occur. It is considered that interference, interference due to delay dispersion, malfunction, etc. do not occur.

However, in the office, box-shaped equipment such as a metal furniture storehouse, a storage room, doors, partitions, partitions, partitions, equipment having flat plates such as whiteboards, desks, storage wagons, storage boxes, Since steel furniture such as a locker is installed and these metal surfaces serve as a reflection plate of electromagnetic waves, mutual interference of electromagnetic waves, interference due to delay dispersion, malfunction, etc. actually occur. The same problem occurs when metal furniture or metal parts are brought into the office. Therefore, the above-mentioned electromagnetic wave absorbing material can be easily attached to an electromagnetic wave reflecting metal surface at a required amount in a necessary amount, and various metal surfaces can be attached / detached in order to easily find a metal surface that causes radio interference. What is more, there is a demand for an electromagnetic wave absorber that has good cosmetic properties and on which stationery and office equipment such as magnets and magnetic sheets that use magnetic force can be mounted.

[0009]

SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to provide a broadband electromagnetic wave absorbing material that absorbs electromagnetic waves from a quasi-microwave band to a millimeter wave band, is thin, and can be easily mounted on a metal surface. An object of the present invention is to provide a low-reflection sheet for office use and a method for manufacturing the same.

[0010]

SUMMARY OF THE INVENTION The gist of the present invention is to provide a low reflection sheet for office, which comprises a first layer made of hard ferrite and a binder, a second layer made of a conductive material, and a metal oxide magnetic material. It has a third layer made of powder and a binder, and a fourth layer made of fine metal magnetic powder and a binder. Further, the gist of the present invention is, in a method for manufacturing a low reflection sheet for office, after magnetizing a first layer made of hard ferrite and a binder by an external magnetic force to form a magnet sheet, a second layer made of a conductive material, The third layer composed of the metal oxide magnetic fine powder and the binder and the fourth layer composed of the metal magnetic fine powder and the binder are sequentially laminated. Further, the gist of the present invention resides in that the above-mentioned low reflection sheet for office is further provided with a fifth layer made of a polymer film for imparting aesthetic properties and / or mechanical strength. Hereinafter, the present invention will be described in detail.

The first layer of the office low reflection sheet of the present invention comprises a hard ferrite and a binder. The hard ferrite is not particularly limited, and examples thereof include Al—Ni—Co magnets of metal-based permanent magnet materials; Sm—Co-based, N.
Rare earth magnets such as d-Fe-B system; BaO.6Fe
₂ O _3, magnet type ferrites such as SrO · 6Fe ₂ O _3; W type ferrite _{Ba · Fe 18 O 27; γ} -Fe 2 O 3, Co-γ-Fe 2 O 3, Fe 4 O
Spinel magnets such as ₄ can be mentioned. Preferably, it is a magnet plumbite type ferrite.

As the binder, either a thermosetting resin or a thermoplastic resin can be used, but a thermoplastic resin is preferred. The thermoplastic resin is not particularly limited, for example, polyethylene, polypropylene, polymethylpentene, polybutene, polystyrene,
Non-polar resins such as polybutadiene, crystalline polybutadiene, styrene butadiene; polyvinyl chloride, polyvinyl acetate, polymethylmethacrylate, polyvinylidene chloride,
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, polyacrylate resin, polysulfone resin, polyimide Resins such as resins, polyamideimide resins, polyphenylene sulfide resins, polyoxybenzoyl resins, polyetheretherketone resins, polyetherimide resins, silicone resins and epoxy resins; modified resins thereof and the like can be mentioned. These may be used alone or in combination of two or more.

As the above-mentioned binder, wetting properties with hard ferrite powder, viscosity during kneading of resin, temperature, physical properties of film, chemical resistance, heat resistance, water resistance, adhesion to metal or plastic, etc. It can be appropriately selected in consideration. Among them, ethylene-vinyl acetate copolymer, modified ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-
Preference is given to vinyl chloride graft copolymer resins, chlorinated polyethylene resins, vinyl chloride resins, polyester resins, acrylic resins, amide resins, silicone resins, epoxy resins and their modified resins.

In the first layer, the weight ratio of the hard ferrite to the binder is (hard ferrite) /
(Binder) = 70/30 to 93/7 is preferable. If the content of hard ferrite is less than 70% by weight, the adhesive strength to a metal surface is weak, and if it exceeds 93% by weight, a uniform sheet cannot be obtained.

When blending the hard ferrite with the binder, a surfactant, a wetting agent, a viscosity reducing agent, etc. may be added, if necessary, in order to improve the wettability and fluidity of the hard ferrite. A heat stabilizer and an antioxidant may be added for stability during production.

In the present invention, the first layer composed of hard ferrite and a binder can be manufactured, for example, by the following method. The binder and, if necessary, the surface-treated hard ferrite powder and other additives are kneaded with a roll, a Banbury mixer, a pressure kneader or the like, and further formed into a sheet by a pressure press, a calendar roll, an extruder or the like.

The thickness of the first layer is preferably 0.2-5 mm. If it is less than 0.2 mm, the coercive force is weak and it is 5 m.
When it exceeds m, it is difficult to obtain a flat sheet. The adhesive strength of the first layer to the metal surface is preferably 3 g / cm ² or more when laterally pulled.
If it is less than 3 g / cm ² , the adhesive strength when mounted on a vertical surface will be weak.

The second layer of the low reflection sheet of the present invention is made of a conductive material. The conductive material is not particularly limited as long as it has a shielding property of 20 dB or more, preferably 30 dB or more, due to the conductivity. The conductive material can also serve as a support. The conductive material is not particularly limited, 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 and the like. be able to. Such a metal material may be a precoated steel sheet that has been subjected to a surface treatment or a primer treatment for improving interlayer adhesion.

As the second layer, a conductive coating film containing the conductive material and a binder, a liquid phase or vapor phase plating layer of the conductive material, or the like can be used. For example, a conductive coating film of the above metal is provided on a non-conductive material such as a plastic material, an electroless plating layer of copper or Ni is formed, a metallized material in which a vapor deposition layer of aluminum or the like is formed, etc. Can also be used.

The thickness of the second layer is preferably 50 μm to 3 mm. If the thickness is less than 5 μm, for example, a foil such as an aluminum foil can be used, but if the thickness exceeds 3 mm, the weight of the second layer becomes heavy and the mounting stability deteriorates. When the first layer and the third layer are bonded by magnetic force, the strength of the magnetic force is reduced and the overall mountability is reduced.

The third layer of the low reflection sheet of the present invention comprises a fine powder of metal oxide magnetic material and a binder. As used herein, the term “metal oxide magnetic material” refers to a metal oxide (for example,
It is a magnetic material mainly composed of iron oxide and the like, and is used as a term distinguished from a metal magnetic material described later. The metal oxide magnetic material is not particularly limited, and examples thereof include Mn-Zn ferrite, Ni-Zn ferrite, Mn-Mg-Zn ferrite, Li ferrite, Mn-Cu-Zn ferrite, Ba ferrite, and Sr ferrite. be able to. Among them, Mn-Zn ferrite and Ni-Zn
Ferrite, Mn-Mg-Zn ferrite and the like are preferable. The average particle diameter of the metal oxide magnetic material is 1 to 50 μm.
Is preferred. More preferably, it is 5 to 20 μm. The metal oxide magnetic material may be subjected to a surface treatment with a silane coupling agent, a titanium-based coupling agent, or the like, if necessary.

The compounding amount of the above metal oxide magnetic material is 85 to 9
2% by weight is preferred. If it is less than 85% by weight, the electromagnetic wave absorbing ability is lowered, and if it exceeds 92% by weight, the electromagnetic wave absorbing ability is good, but the rigidity, weight, durability and the like are poor, so that it is not practical as an electromagnetic wave absorbing material. Become. More preferably, it is 90% by weight.

The above-mentioned binder is not particularly limited, and examples thereof include epoxy resin, polyvinyl chloride, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate block copolymer, ethylene-acrylic acid ester copolymer, ethylene- Thermoplastic and thermosetting of acrylic ester block copolymer, chlorinated polyethylene, acrylic resin, fluorine-containing polymer, polyamide, polyester, silicone resin, polyurethane resin, synthetic rubber, phosphadiene resin, 1,2-nylon, etc. Organic polymeric materials; calcium sulfate, calcium silicate, water glass, Holtland cement, alumina cement, alkyl silicate, calcium oxide, inorganic ceramic materials such as clay, and the like. Among them, epoxy resin, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate block copolymer,
Ethylene-acrylic ester block copolymer, 1,
2-nylon and the like are preferable.

When the above metal oxide magnetic material and the above binder are blended, a plasticizer and a viscosity reducing agent are provided in order to facilitate layer formation and to improve electromagnetic wave absorbing ability and workability. , Surface active agents, flame retardants, lubricants, defoamers, heat stabilizers,
Antioxidants and the like may be added. When the obtained low reflection sheet is used as a building material, a flame retardant may be added.

In the formation of the third layer, when an organic polymer material is used as the above-mentioned binder, a commonly used method such as extrusion molding or pressure molding, a suitable amount of a diluent is added to prepare a thick film. The layer can be formed by a method such as painting. 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 third layer is 1.8 in order to obtain a practical low-reflection sheet having an electromagnetic wave absorption rate of more than 75% in the quasi-microwave band and the quasi-millimeter wave band, respectively.
˜3.6 mm is preferred. If it is less than 1.8 mm, the absorption capacity in the quasi-microwave band is lowered, and if it exceeds 3.6 mm, not only the material cost becomes expensive, but also the weight becomes heavy, which is not preferable in practice. More preferably 2.2-
3.2 mm. The third layer easily provides adhesion by the magnetic force of the hard ferrite of the first layer. Therefore, when the thickness of the second layer is 50 μm to 1 mm, good adhesiveness can be obtained by surface bonding without using an adhesive.

The fourth layer of the low reflection sheet of the present invention comprises fine metal magnetic powder and a binder. The metal magnetic material is not particularly limited, and examples thereof include magnetic metal simple substances such as Fe, Ni, and Co; silicon steel; sendust; super sendust;
Permalloy; Amorphous metal; Si, Al, Co, N
Examples thereof include magnetic metal alloys such as iron magnetic alloys containing at least one selected from the group consisting of i, V, Sn, Zn, Pb, Mn, Mo, and Ag. In addition to the above, high-purity Fe powder can also be used, and carbonyl iron powder or magnetic alloy powder containing 80% by weight or more of iron produced by the atomization method is preferably used. 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. More preferably 2 to 20
μm. The amount of the metal magnetic material is preferably 80 to 90% by weight. When the content is less than 80% by weight, the electromagnetic wave absorbing ability is reduced. When the content is more than 90% by weight, the electromagnetic wave absorbing ability is good, but the rigidity, weight, durability and the like are inferior. Become.

The above-mentioned binder is not particularly limited, and may be the third one.
The same binder as used in forming the layer can be used. The layer formation can be performed in the same manner as the third layer. When blending the metal magnetic material and the binder, in order to facilitate layer formation, further, in order to improve electromagnetic wave absorption ability, workability, etc., a plasticizer, a viscosity reducing agent, a surfactant, Flame retardant, lubricant, defoamer, heat stabilizer,
Antioxidants and the like may be added. When the obtained low reflection sheet is used as a building material, a flame retardant may be added.

The thickness of the fourth layer is 0.2 in order to obtain a practical low reflection sheet exhibiting an electromagnetic wave absorption rate of more than 75% in the quasi-microwave band and the quasi-millimeter wave band, respectively.
~ 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 is reduced. More preferably, it is 0.3 to 0.8 mm. In order to provide a lightweight and thin electromagnetic wave absorbing material, the total thickness of the third layer and the fourth layer is preferably 4 mm or less.

The low reflection sheet for offices of the present invention can be manufactured, for example, by the following method. The mixture of hard ferrite and binder is sheeted to obtain the first layer. A plate or the like made of a conductive material is stacked thereon to form a second layer. Further, a mixture composed of the metal oxide magnetic material and the binder is applied thereon to form the third layer. Then apply a mixture consisting of a magnetic metal and a binder,
By forming the fourth layer, the low reflection sheet for office of the present invention is obtained. In the present invention, since the low reflection sheet for office is adhered to the metal surface, for example, when the first layer is formed into a sheet, it can be magnetized by an external magnetic field to be a magnet sheet as is generally performed. .

In the process of manufacturing the low reflection sheet for offices of the present invention, after magnetizing only the first layer which is the adhesive surface,
By laminating the second layer, the third layer, and the fourth layer, the obtained low-reflection sheet for office can retain the magnetic force necessary for adhering to the metal surface. Further, if magnetized after the lamination, not only the first layer but also the second layer and the subsequent layers will be magnetized, and the electromagnetic wave absorbing ability will be deteriorated. Therefore, it is necessary to magnetize the first layer before laminating.

In the low reflection sheet for offices of the present invention, the second layer, the third layer and the fourth layer must be laminated in this order on the first layer. If this order is changed, the electromagnetic wave absorbing ability becomes insufficient.

In the present invention, the low reflection sheet for office is provided with aesthetic properties and / or mechanical strength,
A fifth layer can be further provided on the fourth layer. A film having a two-dimensional pattern such as a printed pattern or a three-dimensional pattern such as a concavo-convex pattern can be provided as the fifth layer in order to impart beauty. Surface protection for imparting mechanical strength includes semi-permanent protection and primary protection. For semi-permanent protection, a polymer that has excellent weather resistance and mechanical strength and is transparent to electromagnetic waves, for example, polycarbonate, acrylic resin, etc.
A decorative film provided as a layer and for primary protection;
Strippable film; Paper wallpaper; Textile wallpaper; Vinyl wallpaper; Chemical fiber wallpaper; Inorganic wallpaper; Strippable paint; Cloth made of fiber,
A cloth, cork board or the like can be provided as the fifth layer.

The low reflection sheet for offices of the present invention may have functions such as heat insulation, soundproofing, fireproofing, rustproofing and waterproofing, in addition to the ability to absorb electromagnetic waves.

The low reflection sheet for offices of the present invention can be easily attached to and detached from a required place on the electromagnetic wave reflecting metal surface, so that a box-shaped fixture such as a metal furniture storehouse or a storage cabinet in an office, a door. , A partition, a partition, a partition, an equipment having a flat plate such as a whiteboard, a desk, a storage wagon, a storage box, a steel steel furniture such as a locker, and the like can be suitably used for an electromagnetic wave reflecting metal surface. Also,
INDUSTRIAL APPLICABILITY The low reflection sheet for offices of the present invention can be easily attached to and detached from various metal surfaces to find a metal surface that causes radio interference and to easily neutralize the electromagnetic wave reflection surface. Further, by adjusting the thicknesses of the third layer and the fourth layer, it is possible to manufacture an absorber that selectively absorbs a specific frequency, which is useful for the maintenance of communication infrastructure.

According to the idea of the distributed constant circuit, the amount of absorption 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
It is a technique that brings the field impedance close to the characteristic impedance of space for two frequency bands that are very far apart, such as the quasi-microwave band and the quasi-millimeter wave band.

[0038]

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 Ferrite (B) whose surface was treated with a silane coupling agent
90% by weight of aO.6Fe ₂ O ₃ ) powder and 10% by weight of chlorinated polyethylene resin (Eraslen 303A, Showa Denko KK) are kneaded with a pressure kneader, extruded from a die and magnetized by an external magnetic field to obtain a thick film. A first layer having a thickness of ² mm and a horizontal adhesive force of 3 g / cm ² was obtained. Such first
A 1 mm thick second layer copper plate was laid on the layer, and MnO, ZnO, and F with a molar ratio of 32:14:54 were further stacked on the layer.
Ferrite fine particles containing e ₂ O ₃ and having an average particle diameter of 15 μm were mixed with a two-component curing type epoxy resin (main component: “Epiclon 8
No. 30 ", manufactured by Dainippon Ink and Chemicals, Inc., curing agent:" Epomate LX-2S "manufactured by Yuka Shell Epoxy Co., Ltd.), and ferrite fine particles were dispersed in a solid content of 90% by weight. A third layer was formed by coating the resulting mixture with a thickness of 2.5 mm.

Then, carbonyl iron having an average particle size of 3.5 μm (HL grade, manufactured by BASF) was dispersed in the above two-component curing type epoxy resin in an amount of 85% by weight in solid content. The obtained mixture was coated on the third layer to a thickness of 0.5 mm to form a fourth layer, and a low reflection sheet for office was obtained. In this example, the average particle size of the fine particles was measured using Microtrac.

The obtained low-reflection sheet was attached to the surface of a storage cabinet made of coated cold-rolled steel sheet having a thickness of 0.4 mm, and pulled from the lateral direction to confirm that the sheet was sufficiently adhered. Measurement of return loss at normal incidence In order to measure the return loss at normal incidence of the obtained sheet, it was processed so as to be incident on a TEM, put into a 7 mm hollow coaxial tube, and the return loss was measured by a network analyzer. It was measured. The results are shown in Table 1. Measurement of return loss at oblique incidence In order to see the performance as a low-reflection material against electromagnetic waves, the characteristics of electromagnetic waves at 45 ° oblique incidence were measured using a near-field electromagnetic antenna measurement device (NFAMS, manufactured by Icom). The attenuation was measured at 1.9 GHz, 2.45 GHz, and 19 GHz in the TE mode and the TM mode. As a result, it was confirmed that it has a good function as a low reflection material. The results are shown in Table 2.

Example 2 Strontium ferrite (Sr) was used as the first layer ferrite.
O.6H ₂ O) was used to obtain a first layer having an adhesive force of 4 g / cm ² in the same manner as in Example 1. Such first
An aluminum plate having a thickness of 1 mm was laid on the layer, and MnO, ZnO, and Fe ₂ O ₃ were further laminated on the layer with a molar ratio of 32:14:54.
90 parts by weight of ferrite fine particles having an average particle size of 8 μm containing and vinyl chloride resin (Zeon 121, manufactured by Zeon Corporation)
10 parts by weight, 3 parts by weight of plasticizer DOP, and an appropriate amount of heat stabilizer were melt-kneaded by a test roll installed at 150 ° C., and the kneaded body was further rolled by a hot press at 110 ° C., and then 1
A hot roll at 40 ° C. was used to form a 2.5 mm sheet. Then, this sheet was overlaid on the second layer and further laminated with heat to obtain a laminate. Further, using 85 parts by weight of carbonyl iron (HL grade, manufactured by BASF) having an average particle size of 3.5 μm and 15 parts by weight of chlorinated polyethylene (Eraslen 303A, manufactured by Showa Denko KK) in the same manner as above on the third layer. Was formed into a sheet having a thickness of 0.5 mm and covered to form a fourth layer. 150 μm vinyl chloride cosmetic film (Arterit manufactured by Nippon Paint Co., Ltd.) in order to add beauty to this
Was attached to obtain a low reflection sheet for office. The obtained low-reflection sheet for office was attached to a partition made of cold-rolled coated steel sheet, and when pulled downward, it was sufficiently adhered and when a force of 3.5 g / cm ² was applied to the sheet. Moved down. Further, the paper was mounted on the sheet by using a magnet bar to fix the document to the sheet, but the sheet was not dropped and had sufficient adhesiveness to the magnet product. The return loss of the obtained low reflection sheet for offices at normal incidence and oblique incidence was measured in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Example 3 The adhesive strength was 8 g / g in the same manner as in Example 1 except that Nd-Fe-B alloy powder was used as the ferrite of the first layer.
A cm ² first layer was obtained. An iron plate having a thickness of 1 mm to be a second layer is laid on the first layer, and MnO, MgO, ZnO and Fe with a molar ratio of 5: 12: 14: 69 are further stacked on the iron plate.
88 parts by weight of ferrite fine particles containing ₂ O ₃ and having an average particle size of 10 μm, 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 5 parts by weight of a heat stabilizer at 150 ° C. After melt-kneading with the test roll set to, the kneaded body is further rolled with a hot press at 110 ° C.,
It was formed into a 2.5 mm sheet with a 140 ° C. hot roll.
Furthermore, silicon steel powder having an average particle size of 10 μm (Fe: Si = 9
4: 6) 85 parts by weight and 15 parts by weight of chlorinated polyethylene (Eraslen 303A, manufactured by Showa Denko KK) were kneaded in the same manner, and formed into a sheet having a thickness of 0.5 mm and covered on the third layer. To be the fourth layer. 150 more on this fourth layer
A μm vinyl chloride-based decorative film (Arterit, manufactured by Nippon Paint Co., Ltd.) was attached to obtain a low reflection sheet for office. The obtained low reflection sheet for office was stuck on a steel furniture to test the adhesiveness, and it was 6.5 g / cm ^2.
It moved downward when the force was applied to the sheet, but had sufficient adhesiveness. The return loss of the obtained low reflection sheet for offices at normal incidence and oblique incidence was measured in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Example 4 The magnet sheet made of barium ferrite used in Example 1 was used as the first layer, and 0.27 was used as the second layer.
A mm-mm copper-plated steel plate was used. On the copper-plated surface of the second layer,
Molar ratio 32:14:54 MnO, ZnO and Fe ₂ O ₃
93 parts by weight of ferrite fine particles having an average particle size of 8 μm including and 7 parts by weight of chlorinated polyethylene (Eraslen 303A, manufactured by Showa Denko KK) were kneaded with a pressure kneader and formed into a sheet with an extruder to give a sheet of 2.5 mm. The thickness was thermocompression bonded onto the second layer to form a third layer. Furthermore, the average particle size is 10μ
m by using 85 parts by weight of silicon steel powder (Fe: Si = 94: 6), 15 parts by weight of a silicone resin (SH9551, Toray Dow Corning Silicone Co., Ltd.) and 5 parts by weight of antimony trioxide, and kneading at room temperature. A sheet having a thickness of 0.5 mm was formed into a fourth layer. A plain weave cloth cloth was laminated on this to form a fifth layer, and an office low reflection sheet was obtained. The return loss of the obtained low reflection sheet for offices at normal incidence and oblique incidence was measured in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Example 5 A magnet sheet made of the strontium ferrite used in Example 2 was used as the first layer, and 4 was used as the second layer.
A 007 mesh stainless steel wire mesh was used. On the second layer, 90 parts by weight of ferrite fine particles having an average particle size of 5 μm containing MnO, MgO, ZnO and Fe ₂ O ₃ in a molar ratio of 5: 12: 14: 69 and chlorinated polyethylene (Eraslen 303A, Showa era). (Manufactured by Denko Co., Ltd.) was kneaded with a pressure kneader using 10 parts by weight, formed into a sheet with an extruder to have a thickness of 2.5 mm, and thermocompression bonded onto the second layer to form a third layer.
Furthermore, 75 parts by weight of Sendust alloy powder having an average particle size of 18 μm (manufactured by Mitsubishi Materials) and 25 parts by weight of chlorinated polyethylene (Eraslen 303A, manufactured by Showa Denko KK) were kneaded in the same manner to form a third layer on top. A sheet having a thickness of 0.5 mm was formed into a sheet and covered to form a fourth layer. A 5 mm cork board was laminated on this to form a fifth layer, and an office low reflection sheet was obtained. The return loss of the obtained low reflection sheet for offices at normal incidence and oblique incidence was measured in the same manner as in Example 1. The results are shown in Tables 1 and 2.

[0046]

[Table 1]

[0047]

[Table 2]

[0048]

Since the low reflection sheet for offices and the method for manufacturing the same of the present invention are as described above, they absorb electromagnetic waves from the quasi-microwave band to the millimeter wave band, and are thin and mounted on a metal surface. It is easy to obtain a low-reflection sheet for offices, a metal furniture storehouse in the office,
Box-shaped equipment such as storage, equipment with flat plates such as doors, partitions, partitions, partitions, and whiteboards,
It can be suitably used for an electromagnetic wave reflecting metal surface such as a steel-made furniture such as a desk, a storage wagon, a storage box, a locker and the like.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuyuki Oda 19-17 Ikedanaka-cho, Neyagawa-shi, Osaka Japan Paint Co., Ltd.

Claims (3)

[Claims] 1. A first layer made of hard ferrite and a binder, a second layer made of a conductive material, a third layer made of metal oxide magnetic fine powder and a binder, a metal magnetic fine powder and A low reflection sheet for office, comprising a fourth layer made of a binder. 2. A first layer composed of hard ferrite and a binder is magnetized by an external magnetic force to form a magnet sheet, and then a second layer composed of a conductive material, a fine powder of a metal oxide magnetic material and a binder. A method for manufacturing a low reflection sheet for office, comprising laminating three layers and a fourth layer composed of a fine metal magnetic powder and a binder in order. 3. The office low-reflection sheet according to claim 1, further comprising a fifth layer made of a polymer film for imparting beauty and / or mechanical strength. Low reflection sheet for.