JP4079031B2 - Radio wave absorbing interior materials - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a novel electromagnetic wave absorbing interior material. The radio wave absorbing interior material according to the present invention is excellent in mass productivity, workability, aesthetics, durability, etc., and installed on a wall or floor of a house or office where an electromagnetic wave transmitting device such as a wireless LAN is installed. Used to control
[0002]
[Prior art]
The radio wave absorber absorbs the incoming radio wave and attenuates it, and absorbs the acquired radio wave by using the electrical loss and magnetic loss of the material.
[0003]
As a conventional wave absorber, a carbon fiber mesh is put in a conductive rubber body to form a tile carpet base, and the tile carpet base is woven with bristle feet through a conductive rubber adhesive has been proposed. (For example, refer to Patent Document 1). In addition, an electromagnetic wave absorbing curtain made of a ceramic fiber containing a conductive element is disclosed (for example, see Patent Document 2). However, in a carpet composed of a carbon fiber mesh and a conductive rubber body, it is very troublesome to uniformly mix conductive powder with a resin base material such as rubber, and the carbon fiber and the conductive rubber substrate are in a conductive state. The work of confirming that the joints have been joined is essential for quality control, but it was an extremely time-consuming work. In addition, the method using conductive ceramic fibers has been a cause of difficulty in manufacturing the material and pressing the manufacturing cost.
[0004]
As described above, the conventional radio wave absorbing interior materials have problems such as much time and effort for manufacturing and quality control, and high manufacturing cost because it is difficult to manufacture the materials.
[0005]
[Patent Document 1]
JP-A-6-310891 [0006]
[Patent Document 2]
Japanese Patent Laid-Open No. 2001-135135
[Problems to be solved by the invention]
An object of the present invention is to provide a radio wave absorption interior material that can easily manufacture a radio wave absorption layer and is excellent in mass productivity, aesthetics after construction, and durability in view of the above-described problems of conventional radio wave absorbers. It is.
[0008]
[Means for Solving the Problems]
In order to achieve the above-described object, the present invention provides a mixed molded sheet containing conductive short fibers and non-conductive short fibers, and a non-conductive fiber sheet between the layers, with a resin interposed therebetween. Providing fixed electromagnetic wave absorbing interior materials.
[0009]
The mixed molded sheet is preferably a non-woven sheet containing conductive short fibers and non-conductive short fibers. Further, the mixed molded sheet is preferably composed of a plurality of layers, and has a non-conductive layer between the layers.
[0010]
The non-conductive fiber sheet is preferably an organic fiber woven fabric or an organic fiber knitted fabric because it is excellent in aesthetics and durability.
[0011]
The organic fiber woven fabric or the organic fiber knitted fabric desirably has a carpet-like raised shape from the viewpoint of durability.
[0012]
In addition, the mixed molded sheet and the non-conductive sheet described above are joined via a resin. At this time, a part of the fiber structure constituting the non-conductive fiber sheet enters the mixed molded sheet and is fixed with the resin. It is preferable that
[0013]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a reference example of the present invention. In FIG. 1, the radio wave absorbing interior material is composed of a non-conductive fiber sheet 1, a bonding resin layer 2, and a mixed molded sheet 3 including conductive short fibers and non-conductive short fibers in order from the radio wave arrival side. It has a layered configuration. In the mixed molded sheet 3, non-conductive short fibers 4 and conductive short fibers 5 are mixed. The mixed molded sheet 3 may be composed only of the non-conductive short fibers 4 and the conductive short fibers 5, and in order to increase the strength, the non-conductive short fibers 4 and the conductive short fibers 5 are made of a resin such as rubber. It may be mixed and fixed inside, but it is important that it is well mixed.
[0014]
As the short fibers having conductivity, carbon fibers, organic conductive fibers, metal fibers, metal plated fibers, and the like can be used. Moreover, the semiconductor fiber obtained by controlling the calcination temperature at the time of manufacturing carbon fiber or silicon carbide fiber may be used.
[0015]
The bonding resin layer for bonding the non-conductive fiber sheet 1 and the mixed molding sheet 3 including the conductive short fibers and the non-conductive short fibers is polyurethane, polyvinyl chloride, rubber, epoxy, vinyl acetate. It is possible to use an adhesive such as a system or a thermoplastic resin material.
[0016]
The non-conductive fiber sheet 1 may be a non-woven fabric, a woven fabric, or a knitted fabric made of non-conductive fibers, or may be a composite fiber sheet having a base fabric and napped portions like a tufted carpet. It can be selected as appropriate according to the conditions. When giving priority to aesthetics as an interior material, a fabric having good dyeing processability and excellent design is desirable, and when giving priority to durability, it is preferable to take a raised form, and a composite fiber sheet having a base fabric and a raised part Is particularly desirable. The durability of the surface is further improved by the organic fibers taking napped form. As a method for forming a carpet-like napped form, for example, a known tufted carpet manufacturing method can be used. In other words, for a tufted carpet base fabric such as a nonwoven fabric or a woven fabric, organic fibers are continuously sewn in a loop shape so as to penetrate the base fabric, and more than half of the organic fibers stand up from the base fabric. A carpet-like organic fiber sheet having a state can be obtained.
[0017]
It is preferable that a nonelectroconductive fiber sheet contains an organic fiber. The type of organic fiber is not particularly limited, but polyester fiber, nylon fiber, glass fiber, aramid fiber, acrylic fiber, polyphenylene sulfide fiber, polyether ether ketone fiber, polyparaphenylene benzobisoxazole fiber, polylactic acid fiber, etc. are used. be able to. Further, as the electrical resistance of the non-conductive fiber, it is preferable to select one having a volume resistivity that is two or more orders of magnitude greater than the volume resistivity of the conductive fiber used.
[0018]
The mixed molded sheet 3 absorbs radio waves that arrive due to electrical loss. Specifically, a minute current flows in the mixed molded sheet due to the action of the incoming radio wave, and finally it is converted into heat to attenuate and absorb radio wave energy.
[0019]
The mixed molded sheet can be manufactured by various methods, but in order to obtain ease of manufacture and uniform mixing of conductive short fibers and non-conductive short fibers, the mixing proceeds uniformly and is mass-productive. It is particularly preferable to use a dry nonwoven fabric obtained by passing an excellent wet paper-making mixed paper or a mixture of conductive short fibers and non-conductive short fibers through a card machine.
[0020]
The mixed paper is a wet paper making method in which at least one of these conductive short fibers and non-conductive short fibers is mixed with water to form a slurry, and these conductive short fibers and non-conductive fibers are mixed. It can be obtained by a dry papermaking method in which at least one kind of each short fiber is stirred and mixed in air and collected in a sheet form. As needed, you may add inorganic binders, such as aluminum hydroxide, and organic binders, such as starch, polyvinyl alcohol, polyethylene, paraffin, and an acrylic fiber. In the case of the wet papermaking method, it is preferable to use carbon fibers that are easy to be mixed because of their low specific gravity, and that use a small amount because the aspect ratio can be increased. In such a case, if the carbon fiber is too short, the fibers do not easily overlap each other and the number of contacts decreases, and if the amount used is increased to compensate for the decrease in the contacts, the manufacturing cost increases. In addition, when the average fiber length is increased, it seems that the amount of use of the fibers is increased due to an increase in the overlap between the fibers, but conversely, since it is easy to break, the average fiber length is 1 to 1. It is preferable to use one within the range of 60 mm. Further, the content of carbon fiber in the mixed paper affects the electrical loss of the radio wave absorption layer. If the amount is extremely small, the electric loss is reduced and the radio wave absorption performance is lowered. If the amount is extremely large, the electric loss is increased, but the reflected wave is also increased. % Is preferable.
[0021]
The mixed molded sheet is also a sheet obtained by mixing the above-mentioned mixed paper or mixed nonwoven fabric with a binder such as rubber or synthetic resin, or a paint containing conductive short fibers and non-conductive short fibers such as paper, film, fiber, etc. It can also be obtained by applying or impregnating the substrate. Further, in the mixed molded sheet or in the bonding resin layer, a material responsible for magnetic loss in order to increase radio wave absorption, that is, a material that converts radio wave energy into heat energy by spin resonance of the material may be mixed. . As the magnetic loss material, ferrite powder or the like can be used. Ferrite includes hexagonal, garnet, and spinel types depending on the crystal structure, and any of them may be used.
[0022]
When the electromagnetic wave absorbing interior material is formed in a tufted carpet shape, a mixed molded sheet may be used as the tufted carpet base fabric.
[0023]
You may arrange | position and use radio wave reflection layers, such as metal foil, on the back surface of the interior material of this invention. The radio wave reflection layer acts to reflect the radio wave that has passed through the radio wave absorption layer to the radio wave absorption layer, and to absorb again the radio wave that could not be absorbed in one pass. Such a radio wave reflection layer is made of, for example, a metal, such as aluminum, copper, silver, or a plate, sheet, thin film, or the like made of a composite material of carbon fiber and resin. The thickness may be arbitrary. However, this radio wave reflection layer is not essential when a so-called counterpart material to which a radio wave absorber is attached or attached, which has conductivity, functions as a radio wave reflection layer.
[0024]
As a configuration of the radio wave absorbing interior material of the present invention, as shown in FIG. 1, the non-conductive fiber sheet 1 and the mixed molded sheet 3 may be separated from each other via the bonding resin layer 2 .
[0025]
FIG. 3 shows an example of an embodiment of the present invention. The mixed molded sheet 3 may have a multilayer structure in which a nonconductive material is disposed between mixed molded sheet layers as shown in FIG . In the case where the mixed molded sheets are arranged in multiple layers, it is preferable to arrange the mixed molded sheets so that the volume resistance value decreases in order from the side from which the radio waves arrive, because the radio wave absorption is further improved.
[0026]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples. The performance values shown in the examples and comparative examples were measured by the following method.
[0027]
<Reflection loss>
After measuring the reflection level when a radio wave was vertically applied to an aluminum plate having a size of 30 cm × 30 cm and a thickness of 1 mm, the radio wave was applied to a sample of the same area, and the reflection loss (dB) was measured from the difference between the two. The reflection loss was measured with a network analyzer 8719ES type transmission (S21) manufactured by Agilent Technologies.
[0028]
< Reference Example 1>
This will be specifically described with reference to FIG.
[0029]
Cotton blended with organic conductive fiber "Sunderron (R)" manufactured by Nippon Kashiwa Dyeing Co., Ltd. with a fiber length of 38 mm and polyester short fiber with a fiber length of 76 mm at a ratio of 0.5% by weight and 99.5% by weight, respectively. The resulting product was passed through a card machine to obtain a mixed molded sheet 3 in the form of a short fiber nonwoven fabric having a thickness of 3 mm and a weight of 300 g / m ² . Next, nylon fiber was passed through a tufting machine as a pile yarn and polypropylene split plain weave fabric as a tufted base fabric to obtain a tufted carpet 1 having a pile length of 4 mm. A tufted carpet 1 was bonded to one side of the mixed molded sheet 3 via a polyurethane-based resin layer 2 to obtain a radio wave absorbing interior material having a total thickness of 7 mm.
[0030]
A tufted carpet side was used as the front surface, and a 1 mm thick aluminum plate was attached to the back surface as a reflective layer to obtain a radio wave absorber. When the reflection loss of the absorber was measured, an absorption characteristic of 5 to 8 dB was obtained at 2 to 10 GHz.
[0031]
In addition, with the tufted carpet side as the surface, it was laid on the floor for 6 months and the degree of damage due to walking was confirmed, but no damage was found.
[0032]
<Example 1 >
A short fiber of carbon fiber having a fiber length of 6 mm and a fiber diameter of 7 μm, a short polyester fiber having a fiber length of 20 mm, and a wood pulp having an average fiber length of 0.7 mm and a weight ratio of 3 Wet papermaking was performed so as to obtain a mixture of 0.5% by weight, 77% by weight and 20% by weight to obtain a short fiber non-woven sheet-like mixed molded sheet (A) having a thickness of 0.5 mm and a weight of 100 g / m ² .
[0033]
Next, nylon fibers were used as pile yarns, and the short fiber nonwoven sheet-like mixed molded sheet (A) was passed through a tufting machine as a tufted base fabric to obtain a tufted carpet having a pile length of 4 mm. The tufted carpet is a tufted carpet having conductive short fibers on a tufted base fabric.
[0034]
A polyvinyl chloride resin was applied to the carpet back so as to have a coating thickness of 1 mm, and was further joined to another short fiber nonwoven fabric sheet-like mixed molded sheet (A). Further, a polyvinyl chloride resin was applied to the back surface to a thickness of 1 mm to obtain a radio wave absorbing interior material having a total thickness of about 7 mm. The radio wave absorbing interior material has a mixed molded sheet layer composed of two layers of conductive fibers and non-conductive fibers.
[0035]
A tufted carpet side of the interior material was used as the front surface, and a 1 mm thick aluminum plate was attached to the back surface as a reflective layer to obtain a radio wave absorber. When the reflection loss of the absorber was measured, an absorption characteristic of 5 to 8 dB was obtained at 2 to 10 GHz.
[0036]
In addition, with the tufted carpet side as the surface, it was laid on the floor for 6 months and the degree of damage due to walking was confirmed, but no damage was found.
[0037]
<Comparative Example 1>
A tufted carpet having a pile length of 4 mm similar to that used in Example 1 was bonded to one side of a polyester 100% short fiber nonwoven fabric sheet having a thickness of 3 mm and a weight of 300 g / m ² via a polyurethane resin. An interior material with a thickness of 7 mm was obtained. A tufted carpet side was used as the front surface, and a 1 mm thick aluminum plate was attached to the back surface as a reflective layer to obtain a radio wave absorber. When the reflection loss was measured for the absorber, the absorption amount was 0 dB at 2 to 10 GHz, and no absorption effect was observed.
[0038]
<Comparative example 2>
Cotton blended with organic conductive fiber "Sunderron (R)" manufactured by Nippon Kashiwa Dyeing Co., Ltd. with a fiber length of 38 mm and polyester short fiber with a fiber length of 76 mm at a ratio of 0.5% by weight and 99.5% by weight, respectively. The resulting product was passed through a card machine to obtain a short-fiber non-woven sheet-like mixed molded sheet having a thickness of 3 mm and a weight of 300 g / m ² . Although this molded body has radio wave absorption performance, it has a poor appearance and is difficult to apply as an interior material. Further, the floor material was laid for 6 months and the degree of damage due to walking was confirmed, but after 6 months the material was severely damaged, such as part of the material being cut off.
[0039]
【The invention's effect】
The interior material having radio wave absorption performance of the present invention fixes a mixed molded sheet of short fibers having conductivity and short fibers having non-conductivity and a non-conductive fiber sheet to each other via a resin. Therefore, as apparent from the examples, the appearance and durability are excellent, and the radio wave absorption layer can be easily manufactured.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a radio wave absorbing interior material according to a reference example of the present invention.
FIG. 2 is a schematic cross-sectional view of a radio wave absorbing interior material according to an embodiment of the present invention.
[Explanation of symbols]
1: Non-conductive fiber sheet 2: Resin layer 3: Mixed molded sheet composed of conductive short fibers and non-conductive short fibers 4: Non-conductive short fibers 5: Conductive short fibers 6: Non-conductive material layer 7: Radio wave reflection layer

Claims (4)

A radio wave absorbing interior material in which a plurality of mixed molded sheets containing conductive short fibers and nonconductive short fibers and a nonconductive fiber sheet between the layers are fixed to each other via a resin. The radio wave absorbing interior material according to claim 1, wherein the mixed molded sheet is a nonwoven fabric sheet containing conductive short fibers and non-conductive short fibers . The electromagnetic wave absorbing interior material according to claim 1 or 2 , wherein the non-conductive fiber sheet is an organic fiber fabric or an organic fiber knitted fabric. The radio wave absorbing interior material according to claim 3 , wherein the organic fiber woven fabric or the organic fiber knitted fabric has a napped shape .

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