JPH1065384A - Office low reflection sheet and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-reflection sheet for offices using a broadband electromagnetic wave absorbing material which absorbs electromagnetic waves from a quasi-microwave band to a millimeter wave band, is thin, and can be easily mounted on a metal surface. And a method for producing the same. A low-reflection sheet for office use, comprising an electromagnetic wave absorbing layer and an adhesive layer made of a material capable of bonding the electromagnetic wave absorbing layer to a metal.

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.

[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 used for indoor wireless devices of a personal portable radio telephone system (PHS) and a medium-speed wireless LAN, and the quasi-millimeter wave band and the millimeter wave band are used for indoor wireless devices of a high-speed wireless LAN. As the demand in each frequency band increases, mutual interference of electromagnetic waves, interference due to delay dispersion,
There is a concern about malfunctions, eavesdropping, etc.

[0004] In order to improve the electromagnetic 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 resin is generally known, and when processing, a 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.

However, such an electromagnetic wave absorber cannot uniformly absorb any of widely separated frequency bands such as a quasi-microwave band, a quasi-millimeter wave band, and a millimeter wave band. With the expansion of the use of the quasi-microwave band and the quasi-millimeter wave band as described above, there has been a demand from related industries to develop an electromagnetic wave absorbing material that uniformly absorbs both the quasi-microwave band and the millimeter-wave band. In addition, in order to design such an electromagnetic wave absorber, it is necessary to consider the ferrite manufacturing conditions for each frequency of the electromagnetic wave to be absorbed, and to manufacture the ferrite. It has been difficult to achieve frequency characteristics.

Japanese Unexamined Patent Publication (Kokai) No. 3-36995 discloses a radio wave absorbing material in which the spin orientation of sintered ferrite is controlled by the magnetic strength of a lower hard ferrite layer to change the complex magnetic permeability so as to enable absorption in a wide band. 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.

Japanese Patent Application Laid-Open No. 8-83994 discloses 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
Electromagnetic wave absorption having a stable low reflection and absorption capability in a wide band of ６０60 GHz has become possible. The second layer is composed of a metal oxide magnetic powder and a binder, and the third layer is composed of a metal magnetic powder and a binder. Frequency characteristics can be realized. Surrounding intelligent office walls, ceilings and floors with such low-reflection materials,
Even if a communication system using radio waves up to the quasi-millimeter wave band and the millimeter wave band is performed in an office, it is considered that problems such as mutual interference of electromagnetic waves, interference due to delay dispersion, and malfunctions do not occur.

However, in the office, there are box-shaped fixtures such as a library and a storage, which are metal furniture, fixtures having doors, partitions, partitions, partitions, partitions, whiteboards and other flat plates, desks, storage wagons, and storage boxes. In addition, since steel furniture such as a locker and the like are installed, and these metal surfaces serve as electromagnetic wave reflectors, mutual interference of electromagnetic waves, interference due to delay dispersion, malfunction, and the like actually occur. Also,
A similar problem occurs when metal furniture and metal parts are brought into the office. In this case, it is not easy to take simple measures such as attaching the above-mentioned electromagnetic wave absorbing material to a metal surface. Therefore, the above-described electromagnetic wave absorbing material can be easily attached to a required portion of the electromagnetic wave reflecting metal surface only in a required amount, and it is necessary to attach / detach to / from various metal surfaces in order to easily find a metal surface that causes radio interference. There is a demand for an electromagnetic wave absorber that can be worn and has aesthetic appearance, and on which stationery and office tools, such as magnets and magnet sheets, using magnetic force can be mounted.

Japanese Patent Application Laid-Open No. 7-283577 discloses a narrow band having a structure in which an electromagnetic wave absorbing layer, a metal foil for reflecting electromagnetic waves, and a flexible magnet magnetized on at least one surface are sequentially superimposed as a measure for preventing radar false images. An effective electromagnetic wave absorber and a method of attaching the electromagnetic wave absorber are disclosed.
Also, a first layer made of hard ferrite and a binder, a second layer made of a conductive material, a third layer made of a metal oxide magnetic powder and a binder, and a fourth layer made of a metal magnetic powder and a binder An office low-reflection sheet comprising layers has also been proposed.

However, in each of these techniques, since a conductive reflective layer is essential, the structure is complicated and the weight becomes heavy. Therefore, a low-reflection sheet that has a simple structure, is lightweight as a whole, and has a higher electromagnetic wave absorption performance is desired.

[0012]

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.

[0013]

The gist of the present invention is that an office low-reflection sheet has an electromagnetic wave absorbing layer and an adhesive layer made of a material capable of bonding the electromagnetic wave absorbing layer to a metal. Exist. The gist of the present invention is:
A method for manufacturing a low-reflection sheet for offices, comprising forming a sheet of a material to be an adhesive layer, and then laminating an electromagnetic wave absorbing layer on the sheeted adhesive layer. Hereinafter, the present invention will be described in detail.

The low reflection sheet for an office of the present invention has an electromagnetic wave absorbing layer and an adhesive layer made of a material capable of bonding the electromagnetic wave absorbing layer to a metal. The electromagnetic wave absorbing layer is not particularly limited, and includes, for example, a binder resin and a magnetic powder having a magnetic loss term,
Alternatively, a binder resin, a magnetic powder having a magnetic loss term, and a conductor powder are preferable.

The binder resin is not particularly restricted but includes, for example, epoxy resin, polyvinyl chloride, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate block copolymer, ethylene-acrylate ester copolymer, ethylene- Thermoplastic and thermosetting of acrylate block copolymer, chlorinated polyethylene, acrylic resin, fluorine-containing polymer, polyamide, polyester, silicone resin, polyurethane resin, synthetic rubber, phosphadiene resin, 1,2-nylon, etc. Organic polymer materials: calcium sulfate, calcium silicate, water glass, Holtland cement, alumina cement, alkyl silicate,
Examples include inorganic ceramic materials such as calcium oxide and clay. Among them, epoxy resin, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate block copolymer, ethylene-acrylate block copolymer,
1,2-nylon and the like are preferred.

As the magnetic substance powder having the above-mentioned magnetic loss term, a metal oxide magnetic substance and a metal magnetic substance are used. In the present specification, the “metal oxide magnetic material” is a magnetic material containing a metal oxide (eg, iron oxide) as a main component, and is used as a term distinguished from the metal magnetic material. The metal oxide magnetic material is not particularly limited.
n-Zn ferrite, Ni-Zn ferrite, Mn-M
g-Zn ferrite, Li ferrite, Mn-Cu-Z
Examples thereof include n ferrite, Ba ferrite, and Sr ferrite. Among them, Mn-Zn ferrite,
Ni-Zn ferrite, Mn-Mg-Zn ferrite and the like are preferable. The average particle size 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 metal magnetic material is not particularly limited.
For example, simple magnetic metals such as Fe, Ni, and Co; silicon steel;
Sendust; Super Sendust; Permalloy; Amorphous metal; Si, Al, Co, Ni, V, Sn, Z
Magnetic metal alloys, such as iron magnetic alloys, including at least one selected from the group consisting of n, Pb, Mn, Mo, and Ag can be given. In addition to the above, high-purity Fe
Powders can also be used, and carbonyl iron powder or a magnetic alloy powder containing 80% by weight or more of iron produced by an atomizing method is preferably used. The metal magnetic material, if necessary,
The surface may be treated with a silane coupling agent, a titanium coupling agent, or the like. The particle size of the metal magnetic material is not particularly limited as long as it can be uniformly mixed with the binding material, but the average particle size is preferably 1 to 30 μm. More preferably, it is 2 to 20 μm.

The conductor powder is not particularly limited.
For example, carbon black, carbon fiber, graphite, metal fine powder, metal fiber and the like can be mentioned. Since the conductor powder has a large dielectric loss term, a layer that absorbs electromagnetic waves can be formed by combining the binder powder with the binder resin to form a film or a sheet.

In the present invention, the electromagnetic wave absorbing layer may be only one layer, or may be two or more layers. For example, (1) a layer made of a binder resin and a metal oxide magnetic material, (2) a layer made of a binder resin and a metal magnetic material, (3) a layer made of a binder resin, a metal oxide magnetic material and a conductor powder, 4) A layer composed of a binder resin, a metal magnetic substance, and a conductor powder is used alone or in combination of two or more. Among them, preferred as a material to be superimposed on the adhesive layer is a two-layer structure in which (2) is further superimposed on (1), and (1) is further superimposed on (1). Having a two-layer structure, the above (2)
A two-layer structure in which the above (1) is further laminated on the above, a two-layer structure in which the above (2) is further laminated on the above (2),
There are three or more layers by combining the above (1) to (4).

Hereinafter, the case where each of the above-mentioned layers (1) to (4) is used alone will be described in detail. The above (1)
It is composed of a binder resin and a metal oxide magnetic material. The amount of the metal oxide magnetic material is preferably 85 to 92% by weight. If it is less than 85% by weight, the electromagnetic wave absorbing ability is reduced,
When it exceeds 92% by weight, the electromagnetic wave absorbing ability becomes good,
Since the rigidity, weight, durability and the like are inferior, the practicability as an electromagnetic wave absorbing material is reduced. More preferably, it is 90% by weight.

When the binder resin and the metal oxide magnetic material are blended, a plasticizer and a viscosity reducing agent are added to facilitate the formation of a layer, and to improve the electromagnetic wave absorbing ability and workability. , A surfactant, a flame retardant, a lubricant, an antifoaming agent, a heat stabilizer, an antioxidant, and the like. When the obtained low reflection sheet is used as a building material, a flame retardant may be added.

In the formation of the above (1), when an organic polymer material is used as the binder resin, a commonly used method such as extrusion molding, pressure molding, or the like, an appropriate amount of a diluent is added to form a paint, and The layer can be formed by a method such as film coating. 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.

In order to obtain a practical low-reflection sheet exhibiting an electromagnetic wave absorptivity of more than 75% in the quasi-microwave band and the quasi-millimeter wave band, when the above (1) is used alone, ) Is preferably 0.5 to 5.0 mm. If it is less than 0.5 mm, the absorption capacity in the quasi-microwave band decreases, and if it exceeds 5.0 mm, not only is the material cost high, but also the weight is heavy, which is not practically preferable. More preferably, it is 1.8 to 3.6 mm.

The above (2) comprises a metal magnetic material and a binder resin. The mixing amount of the metal magnetic material is 80 to 90.
% By weight is preferred. 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.

When the above-mentioned metal magnetic material and the above-mentioned binder resin are blended, a plasticizer, a viscosity-reducing agent, a surface-reducing agent, and the like are added to facilitate the formation of a layer and to improve the electromagnetic wave absorbing ability and workability. Activators, 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.

When the above (2) is used alone, the thickness of the above (2) is preferably 0.5 to 5.0 mm. If it is less than 0.5 mm, the absorption capacity in the quasi-microwave band decreases, and if it exceeds 5.0 mm, not only is the material cost high, but also the weight increases, which is not practically preferable. More preferably, it is 1.5 to 3.5 mm.

The above (3) comprises a binder resin, a metal oxide magnetic substance and a conductive powder. The amount of the metal oxide magnetic material is preferably 85 to 92% by weight. When the amount is less than 85% by weight, the electromagnetic wave absorbing ability decreases. When the amount exceeds 92% by weight, the electromagnetic wave absorbing ability becomes good.
Since the durability and the like are inferior, the practicability as an electromagnetic wave absorbing material is reduced. More preferably, it is 90% by weight.

The amount of the conductive powder is preferably 0.01 to 10 parts by weight based on 100 parts by weight of the binder resin and the metal oxide magnetic material in total. If the amount is less than 0.01 part by weight, the effect of the addition of the conductive powder is not sufficient. If the amount exceeds 10 parts by weight, the reflection of the electromagnetic wave on the absorption layer surface becomes large, and the absorption performance is reduced.

When compounding the binder resin, the metal oxide magnetic material, and the conductor powder, plasticization is performed to facilitate the formation of a layer and to improve electromagnetic wave absorbing ability and workability. Agent, viscosity reducing agent, surfactant, flame retardant,
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.

When the above (3) is used alone, the thickness of the above (3) is preferably 0.5 to 5.0 mm. If it is less than 0.5 mm, the absorption capacity in the quasi-microwave band decreases, and if it exceeds 5.0 mm, not only is the material cost high, but also the weight increases, which is not practically preferable. More preferably, it is 1.8 to 3.6 mm.

The above (4) consists of a binder resin, a metal magnetic material and a conductive powder. 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 decreases.
Although the electromagnetic wave absorbing ability is good, the stiffness, weight, durability and the like are inferior, so that the practicability as an electromagnetic wave absorbing material is low.

The amount of the conductive powder is preferably 0.01 to 10 parts by weight based on 100 parts by weight of the total of the binder resin and the metal magnetic material. If the amount is less than 0.01 part by weight, the effect of adding the conductor powder is not sufficient, and
When the amount exceeds 0 parts by weight, the reflection of the electromagnetic wave on the absorption layer surface becomes large, and the absorption performance is reduced.

When compounding the binder resin, the metal magnetic material, and the conductor powder, a plasticizer is added to facilitate the formation of a layer, and further to improve electromagnetic wave absorbing ability and workability. Viscosity reducing agents, surfactants, 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.

When the above (4) is used alone, the thickness of the above (4) is preferably from 0.5 to 5.0 mm. If it is less than 0.5 mm, the absorption capacity in the quasi-microwave band decreases, and if it exceeds 5.0 mm, not only is the material cost high, but also the weight increases, which is not practically preferable. More preferably, it is 1.5 to 3.5 mm.

In the present invention, it is preferable that the electromagnetic wave absorbing layer has two or more layers. Hereinafter, as an electromagnetic wave absorbing layer having two or more layers, the above (1) is superimposed on the adhesive layer,
Further, a two-layer structure in which the above (2) is superposed thereon will be described as an example. When the above (1) is overlaid on the adhesive layer and the above (2) is further overlaid thereon, the thickness of the lower layer (1) is preferably 1.8 to 3.6 mm. 1.
If it is less than 8 mm or more than 3.6 mm, it is not possible to obtain a practical low-reflection sheet exhibiting an electromagnetic wave absorption capacity of more than 75% in the quasi-microwave band and the quasi-millimeter wave band. More preferably, it is 2.2 to 3.6 mm.

The thickness of the upper layer (2) is as follows:
0.2 to 1.1 mm is preferred. If it is less than 0.2 mm or more than 1.1 mm, the ability to absorb the quasi-millimeter wave band decreases. More preferably, 0.3 to 0.8 mm
It is. In order to provide a light and thin electromagnetic wave absorbing material, the total thickness of the lower layer and the upper layer is preferably 4 mm or less.

In the present invention, when the electromagnetic wave absorbing layer has three or more layers, it can be manufactured by laminating the above (1) to (4), similarly to the electromagnetic wave absorbing layer having the two-layer structure. it can. In order to provide a light and thin electromagnetic wave absorbing material, the total thickness of all the layers is preferably 4 mm or less.

The adhesive layer used in the present invention is made of a material capable of adhering the electromagnetic wave absorbing layer and a metal.
The adhesive layer is present between the electromagnetic wave absorbing layer and the metal surface of the office furniture to which the electromagnetic wave absorbing layer is attached, and has an adhesive function, and also has an electromagnetic wave absorbing surface and a reflecting surface. It also has a function of optimizing the electromagnetic wave absorbing ability of the electromagnetic wave absorbing layer by controlling the distance between the furniture and the metal surface.

The material capable of bonding the above-mentioned electromagnetic wave absorbing layer and metal is not particularly limited, and examples thereof include a magnet, a pressure-sensitive adhesive, and an adhesive. The adhesive layer,
At least one surface is preferably a flexible magnet layer or an adhesive layer formed by molding a polymer adhesive.

The flexible magnet is preferably made of hard ferrite and a binder resin, or a hard ferrite, a binder resin and a conductive powder. The hard ferrite is not particularly limited,
For example, an Al-Ni-Co magnet made of a metal-based permanent magnet material;
Rare earth magnets of Sm-Co type, Nd-Fe-B type, etc .; Ba
O · 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,
Examples include spinel-type magnets such as Fe ₄ O ₄ . Preferably, it is a magnet plumbite type ferrite.

As the binder resin, any of a thermosetting resin and a thermoplastic resin can be used.
Preferably, it is a thermoplastic resin. 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, and polymethyl methacrylate. , 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 (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, polyacrylate resin, polysulfone resin, polyimide resin, polyamideimide resin, polyphenylene sulfide resin, polyoxybenzoyl resin, polyetheretherketone resin, polyetherimide resin, silicone resin , Epoxy resins and the like; and modified resins thereof. These may be used alone or in combination of two or more.

The above binder resin takes into consideration wettability with hard ferrite powder, viscosity during kneading of the resin, temperature, physical properties of the film, chemical resistance, heat resistance, water resistance, adhesion to metals and plastics, and the like. And can be selected appropriately. 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.

The weight ratio of the hard ferrite to the binder resin is preferably (hard ferrite) / (binder resin) = 70/30 to 93/7. 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.

The conductive powder is not particularly limited.
For example, those exemplified as the conductor powder described for the electromagnetic wave absorbing layer and the like can be used. The amount of the conductive powder is preferably 0.01 to 10 parts by weight based on 100 parts by weight of the total of the hard ferrite and the binder resin. If the amount is less than 0.01 part by weight, the effect of adding the conductive powder is small, and if it exceeds 10 parts by weight, the reflection of the electromagnetic wave is likely to occur in the adhesive layer, and the electromagnetic wave absorbing ability is reduced.

When compounding the hard ferrite and the binder resin, or the hard ferrite and the binder resin and the conductive powder, if necessary, the surface activity may be improved in order to improve the wettability and fluidity of the hard ferrite. An agent, a wetting agent, a viscosity reducing agent and the like may be added, and a heat stabilizer and an antioxidant may be added for stability during production.

The above flexible magnet can be manufactured, for example, by the following method. The binder resin 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 calender roll, an extruder, or the like. The obtained sheet is magnetized by an external magnetic field, for example, as is generally performed, so that a flexible magnet having at least one surface magnetized can be obtained.

The adhesive strength of the flexible magnet to the metal surface was 3 g / cm when pulled in the lateral direction.
^Two or more are preferred. If it is less than 3 g / cm ² , the adhesive strength when mounted on a vertical surface will be weak.

The pressure-sensitive adhesive layer is formed by molding a polymer pressure-sensitive adhesive. The polymer adhesive is not particularly limited, and examples thereof include those commonly used as adhesives, adhesives, and the like, such as rubber-based, urethane-based, and acrylic-based adhesives.

The pressure-sensitive adhesive layer formed by molding the above-mentioned polymer pressure-sensitive adhesive may be composed of the polymer pressure-sensitive adhesive itself. Material and polymer adhesive, 0.2 ~
The spacer may be composed of a polymer film having a thickness of about 10 mm and a specific gravity of 0.02 to 0.8, a polymer sheet, a polymer foam, or the like.

In particular, in order to further enhance the function of optimizing the electromagnetic wave absorbing ability of the electromagnetic wave absorbing layer, a polymer adhesive and a specific gravity having a thickness of about 0.2 to 10 mm are required to be 0.0
Those comprising a spacer of 2 to 0.8 of a polymer film, a polymer sheet, a polymer foam or the like are preferable.

The material of the spacer is not particularly limited, and examples thereof include foamable plastic materials such as styrene foam and urethane foam; polyester-based, acrylic-based, and urethane-based foamable materials such as polyester film, PET film, and polymethyl methacrylate film. Plastic film material, etc.

The thickness of the adhesive layer is preferably from 0.1 to 10 mm. When the thickness is less than 0.1 mm, the adhesiveness to the metal surface as the surface to be bonded becomes weak. In particular, in the case of a flexible magnet in which the adhesive layer is magnetized, the coercive force becomes weak.
If it exceeds 0 mm, it is difficult to obtain a flat sheet, the sheet itself becomes heavy, or the handling workability is reduced.

The low-reflection sheet for offices of the present invention is manufactured by forming a material for an adhesive layer into a sheet, and then laminating an electromagnetic wave absorbing layer on the sheeted adhesive layer. For example, an office low-reflection sheet having an electromagnetic wave absorbing layer having a two-layer structure can be manufactured by the following method. First, a mixture of a hard ferrite and a binder resin is formed into a sheet as an adhesive layer. On this occasion,
For bonding to a metal surface, for example, it can be magnetized by an external magnetic field to form a magnet sheet, as is generally done. On the obtained sheet, a sheet made of a metal oxide magnetic material and a binder resin is formed. Then, a sheet made of a metal magnetic material and a binder resin is formed to obtain a low-reflection sheet for office use.

When a polymer adhesive is used as the adhesive layer, for example, a polymer film having a specific gravity of 0.02 to 1.2 is laminated with the polymer adhesive to form an adhesive layer.
Make a sheet. A sheet made of a metal oxide magnetic material and a binder resin is formed on the polymer film surface of the obtained sheet. Then, a sheet made of a metal magnetic material and a binder resin is formed to obtain a low-reflection sheet for office use.

In the present invention, the low-reflection sheet for office may be provided with a layer for imparting aesthetic appearance and / or mechanical strength on the electromagnetic wave absorbing layer. A film having a two-dimensional pattern such as a printed pattern, a three-dimensional pattern such as a concavo-convex pattern, or the like can be provided on the electromagnetic wave absorbing layer in order to impart beauty. Further, in order to impart mechanical strength, a polymer that is excellent in weather resistance, mechanical strength, etc., and is transparent to electromagnetic waves, for example, polycarbonate, acrylic resin, etc., is formed on the electromagnetic wave absorbing layer. For primary protection, decorative film; strippable film; paper wallpaper; textile wallpaper; vinyl wallpaper; chemical fiber wallpaper; inorganic wallpaper; strippable paint; It can be provided on the electromagnetic wave absorbing 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 electromagnetic wave absorbing ability.

The low-reflection sheet for office use according to the present invention can be easily attached to and detached from a required portion of the electromagnetic wave reflection metal surface, so that box-like fixtures such as a library and a storage, which are metal furniture in the office, Fixtures having flat plates such as doors, partitions, partitions, partitions, whiteboards, and the like, which can be suitably used for electromagnetic wave reflecting metal surfaces such as steel furniture such as desks, storage wagons, storage boxes, and lockers. Further, 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 disable the electromagnetic wave reflection surface.

By the way, according to the idea of the distributed constant circuit,
As the field impedance on the outermost surface of the electromagnetic wave absorber approaches the characteristic impedance of the space, the amount of electromagnetic wave absorption increases. The field impedance on the outermost surface of the electromagnetic wave absorber is determined by the electromagnetic characteristics and thickness of the layers constituting the electromagnetic wave absorber, and furthermore, by the frequency of the electromagnetic wave. In the present invention, by adjusting the thickness of the electromagnetic wave absorbing layer, the field impedance is converted into the characteristic impedance of the space for two frequency bands that are very far apart, such as a quasi-microwave band and a quasi-millimeter wave band. As a result, it is possible to manufacture an electromagnetic wave absorber that selectively absorbs a specific frequency, which is useful for maintenance of a communication infrastructure.

The low reflection sheet for office of the present invention is characterized in that a conductive electromagnetic wave reflection layer is not essential as compared with the conventional one. Compared with the conventional electromagnetic wave absorber having the electromagnetic wave reflection layer, the low reflection sheet for office of the present invention is advantageous in the following points. 1. The structure is simple, thin and lightweight. 2. The adhesive layer serves as a spacer or an air gap between the metal to be adhered and the electromagnetic wave absorbing layer to further enhance the electromagnetic wave absorbing ability, resulting in a higher performance and lighter electromagnetic wave absorber. Can be.

The electromagnetic characteristics of the office low-reflection sheet of the present invention can be obtained by processing the sheet, placing it in a coaxial tube, and using a network analyzer by the Nicholson-Loss method. The electromagnetic properties of the electromagnetic wave absorbing layer and the adhesive layer forming the sheet alone can be determined in the same manner. Therefore, the electromagnetic wave absorbing ability of the low reflection sheet for offices of the present invention can be freely designed by changing the thickness of the electromagnetic wave absorbing layer and the thickness of the adhesive layer as necessary, so that the electromagnetic wave absorbing layer and The features of the low reflection sheet for offices of the present invention comprising only the adhesive layer can be fully utilized for designing the electromagnetic wave absorbing ability.

[0061]

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
kneaded aO · 6Fe ₂ O ₃₎ powder 90 wt% chlorinated polyethylene resin (Erasuren 303A, manufactured by Showa Denko Co., Ltd.) and 10 wt% in a pressure kneader, extruded from a die, the thickness be to magnetized by an external magnetic field An adhesive layer having a thickness of 1.5 mm and a horizontal adhesive strength of 3 g / cm ² was obtained. On this adhesive layer, MnO and Zn in a molar ratio of 32:14:54
Melt and kneaded with a test roll using 90 parts by weight of ferrite fine particles containing O and Fe ₂ O ₃ and having an average particle diameter of 15 μm and 10 parts by weight of chlorinated polyethylene (Eraslen 303A, manufactured by Showa Denko KK). The kneaded body was further rolled by a hot press to form a 2.5 mm electromagnetic wave absorbing layer.

The obtained low-reflection sheet was attached to the surface of a cold-rolled steel sheet having a thickness of 0.4 mm and was 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 had a function as a good low reflection material. The results are shown in Table 2. Relationship between the thickness of the adhesive layer and the electromagnetic wave absorbing ability The obtained adhesive layer and the electromagnetic wave absorbing layer were processed so as to be incident on a TEM, put into a 7 mm hollow coaxial tube, and measured for the return loss by a network analyzer.
Electromagnetic characteristics were determined, and the relationship between the thickness of the adhesive layer and the absorptivity was calculated based on the values. The results are shown in FIG.

Example 2 The return loss at normal incidence and the return loss at oblique incidence were measured in the same manner as in Example 1 except that the thickness of the adhesive layer was 3.0 mm. The results are shown in Tables 1 and 2. COMPARATIVE EXAMPLE 1 Between the adhesive layer and the electromagnetic wave absorbing layer, the thickness of the reflective layer was set to 0.1.
The return loss at normal incidence and the return loss at oblique incidence were measured in the same manner as in Example 1 except that a 5-mm aluminum plate was sandwiched. The results are shown in Tables 1 and 2.

Example 3 Strontium ferrite (Sr) was used as the ferrite for the adhesive layer.
O.6H ₂ O) was used in the same manner as in Example 1 to obtain an adhesive layer having an adhesive strength of 4 g / cm ² and a thickness of 2.6 mm. 90 parts by weight of ferrite fine particles containing MnO, ZnO, and Fe ₂ O ₃ and having an average particle diameter of 8 μm in a molar ratio of 32:14:54 and a vinyl chloride resin (Zeon 121, manufactured by Zeon Corporation) 10 in a molar ratio of 32:14:54. Parts by weight, DO of plasticizer
P3 parts by weight and an appropriate amount of a heat stabilizer were melt-kneaded with a test roll set at 150 ° C., and the obtained kneaded body was further mixed with 1 part.
After being rolled by a hot press at 10 ° C., it was formed into a 2.5 mm sheet by a hot roll at 140 ° C. Further, the average particle size is 3.5.
μm carbonyl iron (HL grade, manufactured by BASF) 8
5 parts by weight and chlorinated polyethylene (Eraslen 303A,
Similarly, a sheet having a thickness of 0.5 mm was formed on the above-mentioned 2.5 mm sheet using 15 parts by weight (manufactured by Showa Denko KK) to form an electromagnetic wave absorbing layer. On top of this, a 150 μm vinyl chloride-based decorative film (Arterit, manufactured by Nippon Paint Co., Ltd.) was adhered to obtain an aesthetic appearance, thereby obtaining a low reflection sheet for office use. The obtained low-reflection sheet for office was attached to a partition made of a cold-rolled coated steel sheet, and when pulled downward, it was sufficiently adhered to 3.5 g / cm.
It moved down when a force of ² was applied to the seat. 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.

Comparative Example 2 Instead of the adhesive layer, an electromagnetic wave absorbing layer composed of two layers was fixed with a cellophane tape so as to be attached to a partition made of a cold-rolled steel sheet, and its return loss at normal incidence was measured. The measurement was performed, and the results are shown in Table 1. Example 4 1.5 m made of ferrite and chlorinated polyethylene resin
m instead of an adhesive layer having a thickness of 2.0 mm and a specific gravity of 0.1 mm.
2 and the thickness of the electromagnetic wave absorbing layer was 2.3 mm except that an adhesive layer formed by bonding a double-sided tape of 0.2 mm to both sides of the urethane foam sheet 2 was used. A reflection sheet was obtained. The reflection loss at normal incidence of the obtained low reflection sheet was measured, and the results are shown in Table 1. Example 5 3.5 mm from 5 parts by weight of 6 mm carbon fiber and 95 parts by weight of chlorinated polyethylene as an electromagnetic wave absorbing layer
A low reflection sheet was obtained in the same manner as in Example 1 except that the electromagnetic wave absorbing layer was formed. The reflection loss at normal incidence of the obtained low reflection sheet was measured, and the results are shown in Table 1.

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[Table 1]

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[Table 2]

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As described above, the low-reflection sheet for office use and the method of manufacturing the same according to the present invention absorb electromagnetic waves from the quasi-microwave band to the millimeter-wave band and are thin and mounted on a metal surface. It is possible to obtain a low-reflection sheet for offices that is easy to use, and it has metal furniture in the office, box-like fixtures such as archives and storages, doors, partitions, partitions, partitions, and flat-plate fixtures such as whiteboards. It can be suitably used for electromagnetic wave reflecting metal surfaces such as steel furniture such as desks, storage wagons, storage boxes and lockers.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the thickness of an adhesive layer and the absorptivity of the low reflection sheet for office use of Example 1. The vertical axis represents the return loss (dB), and the horizontal axis represents the thickness (mm) of the adhesive layer.
Represents The solid line represents 1.9 GHz and the thin dashed line represents 2.
It represents 45 GHz, and the dashed line represents 19 GHz.

Claims (6)

[Claims] 1. A low-reflection sheet for office use, comprising: an electromagnetic wave absorbing layer; and an adhesive layer made of a material capable of bonding the electromagnetic wave absorbing layer to a metal. 2. The low reflection office material according to claim 1, wherein at least one surface of the adhesive layer is formed of a magnetized flexible magnet layer or an adhesive layer formed by molding a polymer adhesive. Sheet. 3. The low reflection sheet for an office according to claim 1, wherein the adhesive layer is made of hard ferrite and a binder resin, or is made of hard ferrite, a binder resin and a conductive powder. 4. The electromagnetic wave absorbing layer comprises a binder resin and a magnetic powder having a magnetic loss term, or
4. The low-reflection sheet for offices according to claim 1, comprising a binder resin, a magnetic powder having a magnetic loss term, and a conductor powder. 5. The low reflection sheet for office according to claim 4, wherein the electromagnetic wave absorbing layer is formed by laminating two or more layers. 6. A method for manufacturing a low-reflection sheet for offices, comprising forming a sheet of a material to be an adhesive layer, and then laminating an electromagnetic wave absorbing layer on the sheeted adhesive layer.