GB2451389A

GB2451389A - Radio wave shielding body and method of producing the same

Info

Publication number: GB2451389A
Application number: GB0820928A
Authority: GB
Inventors: Kazuyuki Kashihara; Toshio Kudo; Satoshi Sakai
Original assignee: Mitsubishi Cable Industries Ltd
Current assignee: Mitsubishi Cable Industries Ltd
Priority date: 2006-04-18
Filing date: 2007-04-12
Publication date: 2009-01-28
Anticipated expiration: 2027-04-12
Also published as: KR101050026B1; JP4171500B2; JP2007285026A; GB2451389B; GB0820928D0; WO2007119798A1; KR20080111541A

Abstract

A radio wave shielding body easily produceable and having desired radio wave shielding ability. The radio wave shielding body has a base (10) having on its surface at least either pores or projections/recesses, a coating film (11) formed on the surface of the base (10), and antennas (13) formed on the coating film (11) from a radio wave reflecting material.

Description

1 2451389

DESCRIPTION

RADIO SHIELDiNG MEMBER AND METHOD FOR MANUFACTURING THE

SAME

Technical Field

[0001] The present invention relates to a radio shielding member and a method for manufacturing it.

Background Art

[0002} In recent wide-spreading use of radio equipment typified by an intra-business PHS, a wireless LAN, and the like, it becomes essential to improve radio environment in an office for preventing information leakage and preventing malfunction and noise caused by radio penetration from outside. There have been proposed various types of members for maintenance of the radio environment in an office and the like (Patent Documents 1,2, and the like, for example).

[0003] For example, Patent Document I discloses an electromagnetically shielded intelligent building capable of infonnation communication using radio waves at arbitrary frequencies in a wide-ranged frequency band by adding an electromagnetic shielding member of metal, ferrite, or the like to a framework of a building. As the radio shielding member, radio wave reflectors, such as an iron plate, a metal net, a metal mesh, a metal foil, and the like, and radio wave absorbers, such as a ferrite are disclosed.

[0004] However, the radio wave reflectors and the radio wave absorbers have no frequency selectivity. For this reason, the electromagnetic shielding intelligent building disclosed in Patent Document 1 cannot selectively shield a radio wave at a specified frequency, thereby shielding also radio waves other than the radio waves to be shielded.

[0005] While, Patent Document 2 discloses an electromagnetic shielding building which secures an electromagnetically shielded space in a building by forming an electromagnetic shielding face in which Y-shaped linear antennas are arranged periodically. Each of the Y-shaped linear antennas is composed of three linear element parts having substantially the same length and extending radially from the antenna centre. Patent Document 2 discloses that the electromagnetic shielding building disclosed in Patent Document 2 can shield electromagnetically and selectively a to-be-shielded radio wave.

Patent Document 1: Japanese Examined Patent Application Publication No. 6-99972 Patent Document 2: Japanese Unexamined Patent Application Publication No. 10-169039

Summary of the Invention

Problems that the Invention is to Solve [0006] For arranging an interior radio environment, it is preferable to provide radio shielding property for shielding only a radio wave at a desired frequency to a curtain, cloth attached to a wall, a ceiling, or the like, a concrete wall, and the like. In such a case, it is necessary to form radio wave reflecting antennas on a base material having a surface in which numerous pores are formed, such as fabric of a curtain, cloth attached to a wall, a ceiling, or the like, a concrete wall, and the like.

[0007] For fonning such antennas, a general method is that a radio wave reflecting material is liquefied, applied thereto, and dried, namely, a wet method. The dry method employing sputtering or deposition, which increases the cost and the size of the equipment and takes comparatively much labor, is not suitable for antenna formation.

[0008] When the antennas of the radio wave reflecting material as disclosed in Patent Document 2 are formed on the base material (for example, a sheet) having a surface in which pores are formed, the liquid material penetrates over the base material by capillarity of the pores (in the case of woven fabric, for example, the liquid is liable to penetrate in a direction in which fiber is arranged). This invites difficulty in formation of antennas having desired dimension and shape to attain no desirable radio shielding characteristics.

[0009] Even when the antennas made of a radio wave reflecting material are formed, as disclosed in Patent Document 2, on a base material of which surface is rough, the dimension of the thus formed antennas becomes inaccurate to invite difficulty in attaining desired radio shielding characteristics.

[00101 Formation of antennas by a dry method, such as spultering or the like without using a liquid material involves no problem of penetration of the liquid material over the base material but invites problems of increasing the size of the equipment, and the manufacturing cost, and requires bothersome manufacturing processing steps.

[0011] The present invention has been made in view of the foregoing, and its objective is to provide a radio shielding member which can be manufactured easily and which has desired radio shielding characteristics.

Means for Solving the Problems [0012] To attain the above object, the present invention provides a radio shielding member including: a base material having a surface in which at least one of a plurality of pores and a plurality of projections and depressions are formed; a coating film formed on the surface of the base material; and a plurality of radio wave reflecting antennas formed with a radio wave reflecting material as a use material on the coating film. Namely, the plurality of radio wave reflecting antennas are not in direct contact with the surface of the base material and are disposed on the coating film.

[0013] In the above arrangement, the coating film on the surface of the base material blocks the pores (specifically, the opening parts of the pores) formed in the surface of the base material or flattens the projections and the depressions formed therein. Accordingly, penetration (impregnation, specifically, impregnation in the direction of the surface of the base material) cased by invasion of the pores by the radio wave reflecting material can be suppressed, and variation and inaccuracy in dimension of the radio wave reflecting antennas (deviation from desired dimension of the radio wave reflecting antennas) made of the radio wave reflecting material, which are caused due to the roughness of the surface of the base material, can be reduced.

[0014] In other words, the coating film is provided for substantially canceling the pores and the roughness formed in the surface of the base material to flatten the surface thereof.

Formation of the radio wave reflecting antenna on the coating film attains desired radio shielding characteristics.

[0015] In the above radio shielding member, the base material has the surface in which one of a plurality of pores and a plurality of projections and depressions, namely, has the non-flat surface. The base material includes, for example, fabric, such as woven fabric, non-woven fabric, knit, lace, felt, paper, and the like, a porous body, such as a foam, and the like.

[00 16] In the case where the base material has a plurality of pores, the coating film can suppress penetration of the radio wave reflecting material toward the base material (specifically, the coating film flattens the surface of the base material, more specifically, it blocks the open ends of the pores formed in the surface of the base material which cause penetration). In the case where the base material has a plurality of projections and depressions, the coating film is not limited specifically as long as it can flatten the surface of the base material and can equalize the thickness of the entirety (the total thickness of the base material and the coating film). Wherein, a material having insulating property not influencing the radio shielding characteristics is suitable. Specifically, the material of the coating film includes inorganic materials, such as resin, glass, and the like, rubber, and the like.

[00171 The radio wave reflecting material is preferably a liquid material, for example, in an ink state: in the present description, the liquid material is a concept including a solution of a medium and a solute, or a dispersion obtained by dispersing and mixing particles or a colloidal substance in and with a liquid (only a medium or a medium and a solute); namely, the liquid material means all material at least containing a liquid. Specifically, the liquid material may be a solution (ink) in which a radio wave reflecting material is fused, a solution (ink) containing a colloidal radio wave reflecting material, a particle-dispersed liquid (ink) in and with which particles substantially made of a radio wave reflecting material are dispersed and mixed, or the like. The radio wave reflecting material herein may be a conductive material, for example. Specifically, the conductive material includes copper, aluminum, silver, and the like.

[0018] Preferably, the radio wave reflecting antennas selectively reflect a radio wave at a specified frequency or in a specified frequency band. Specific examples of the antennas of this kind includes a generally-called Jerusalem cross-shaped antenna, a Y-shaped antenna, and the like. Each radio wave reflecting antennas may include three linear first element parts radially extending from the antenna center at angles of approximately 120 degrees to each other and having substantially the same length and a linear second element part connected at an outer end of each of the first elements, thereby reflecting the radio wave at a specified frequency (in the present description, the antenna having this shape may be called a T-Y-shaped antenna).

[0019] Additionally, a method for manufacturing a radio shielding member in accordance with the present invention is a method for manufacturing a radio shielding member including: a base material having a surface in which at least one of a plurality of pores and a plurality of projections and depressions are formed; and a plurality of radio wave reflecting antennas formed above the base material. The method in accordance with the present invention includes the steps of: covering the surface of the base material with a coating film; and thereafter forming the plurality of radio wave reflecting antennas with the use of a radio wave reflecting material.

[0020] Formation of the coating film on the surface of the base material prior to formation of the radio wave reflecting antennas can flatten the surface of the base material (equalize the thickness of the entirety (the total thickness of the base material and the coating film).

This suppresses penetration of the material over the surface of the base material and the like, thereby leading to easy and accurate formation of the radio wave reflecting antennas having desired shape and dimension. Hence, a radio shielding member having excellent radio shielding characteristics can be manufactured easily by this manufacturing method.

Effects of the Invention [0021] The present invention can provide a radio shielding member of which manufacture

S

is easy and which has desired radio shielding characteristics.

Brief Description of the Drawings

[0022] [FIG. 1] FIG. 1 is a plan view showing a configuration of a radio shielding member in accordance with an embodiment of the present invention.

[FIG. 2] FIG. 2 is a plan view showing a part of the radio shielding member in an enlarged scale.

[FIG. 3] FIG. 3 is a sectional view taken along the line Ill-Ill in FIG. 2.

[FIG. 4] FIG. 4 is a plan view showing an antenna in an enlarged scale.

[FIG. 5] FIG. S is a plan view schematically showing a part of a base material made of woven fabric in an enlarged scale.

[FIG. 6] FIG. 6 is a sectional view taken along the line VI-VI in FIG. 5.

[FIG. 7] FIG. 7 is a sectional view showing a state of the radio shielding member having a base material side attached to a wall.

[FIG. 8] FIG. 8 is an explanatory drawing showing the entirety of a rolled radio shielding member including, on the base material side thereof, an adhesive and a protection film in combination of an enlarged sectional view of a part thereof.

[FIG. 9] FIG. 9 is a view corresponding to FIG. 7 which shows the radio shielding member having a reflection layer side attached to a wall.

[FIG. 10] FIG. 10 is a view corresponding to FIG. 8 which shows the entirety of a rolled radio shielding member including, on the base material side thereof, the adhesive and the protection film in combination of an enlarged sectional view of a part thereof.

[FIG. 11] FIG. 11 is a graph showing the relationship between the frequency of radio waves transmitted through the radio shielding member and the transmission loss thereof.

[FIG.12] FIG. 12 is a graph showing the relationship between the length of an element of an antenna and the frequency (matched frequency) of radio waves reflected by the antenna.

[FIG. 131 FIG. 13 is a view corresponding to FIG. 1 which shows Modified Example 1 of the radio shielding member.

[FIG. 14] FIG. 14 is a plan view showing an antenna of Modified Example I in an enlarged scale.

[FIG. 15] FIG. 15 is a view corresponding to FIG. 1 which shows Modified Example 2 of the radio shielding member.

[FIG. 16] FIG. 16 is a view corresponding to FIG. 1 which shows Modified Example 3 of the radio shielding member.

[FIG. 17] FIG. 17 is a view corresponding to FIG. 1 which shows Modified Example 4 of the radio shielding member.

[FIG. 18] FIG. 18 is a view corresponding to FIG. 1 which shows Modified Example 5 of the radio shielding member.

[FIG. 19] FIG. 19 is a view corresponding to FIG. 1 which shows Modified Example 6 of the radio shielding member.

[FIG. 20] FIG. 20 is a graph showing the relationship between the frequency of radio waves and the radio shielding amount (the transmission loss of the radio wave) in

Modified Example 6.

[FIG. 21] FIG. 21 is a view corresponding to FIG. I which shows Modified Example 7 of the radio shielding member.

[FIG. 22] FIG. 22 is a view corresponding to FIG. 1 which shows Modified Example 8 of the radio shielding member.

[FIG. 23] FIG. 23 is a view corresponding to FIG. I which shows Modified Example 9 of the radio shielding member.

[FIG. 24] FIG. 24 is a view corresponding to FIG. 1 which shows Modified Example 10 of the radio shielding member.

[FIG. 25] FIG. 25 is a view corresponding to FIG. 1 which shows Modified Example 11 of the radio shielding member.

[FIG. 26] FIG. 26 is a graph showing, in combination with a case of a comparative example, the relationship between the frequency of radio waves and the transmission loss thereof where the radio shielding member of Modified Example 2 is employed as a working example.

Index of Reference Numerals [0023] 1 radio shielding member base material I Oa surface of base material 11 coatingfllm 12 reflection layer 13, 16, 17, 22, 24, 25, 26, 27, 28, 29 antenna (radio wave reflecting antenna) 13a, 24a, 27a first element part 13b, 16b, 17b, 27b, 28b, 29b second element part 14, 18,20 antenna unit 15, 19,21 antennagroup wall 31 adhesive 32 protection film 40,41 yarn 42 pore 43 depression (roughness) 44 projection (roughness)

Best Mode for Carrying out the Invention

[0024] An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

[0025] FIG. 1 is a view showing a configuration of a radio shielding member in accordance with the present embodiment. FIG. 2 is a plan view showing a part of the radio shielding member in an enlarged scale. FIG. 3 is a sectional view taken along the line HI-Ill in FIG. 2. FIG. 4 is a plan view showing an antenna in an enlarged scale.

[0026] The radio shielding member 1 includes a base material 10 having a surface in which at least one of a plurality of pores and a plurality of projections and depressions are formed, a coating film 11, and a reflection film 12. The radio shielding member 1 may have an aspect for providing radio shielding characteristics to an interior existing object, for example, a window, a wall, a ceiling, a floor, a partition, a desk, or the like. In this case, the base material 10 preferably has a flat face in a plate-like shape, a sheet-like shape, a film-like shape, or the like.

[0027] In the present embodiment, the base material 10 is not limited to this specific structuie as long as it has a surface in which at least one of a plurality of pores and a plurality of projections and depressions are fonned. Within this limit, the base material may be made of any material appropriately selected according to the use of the radio shielding member 1. The base material 10 may be made of resin, glass, paper, cloth, rubber, plaster, tile, wood, or the like, for example. Specifically, the base material 10 may be made of foam of, for example, urethane resin, polyethylene (PE) resin, polystyrol resin, or the like, wood (including plywood), or fabric of, for example, woven fabric (plain weave or the like, for example), non-woven fabric, knit, lace, felt, paper, or the like (cloth or the like adhering or attached to a curtain, a wall, a floor, a ceiling, a window, a desk, a partition, or the like), or the like.

[0028) The plurality of pores and/or the plurality of projections and depressions formed in the surface of the base material 10 will be described with reference to FiG. 5 and FIG. 6 by referring to the case where the base material 10 is made of woven fabric. FIG. 5 is a plan view schematically showing a part of the base material 10 made of woven fabric in an enlarged scale, and FIG. 6 is a sectional view taken along the line VI-VI in FIG. 5 [0029] The base material 10 includes a plurality of first yams 40 extending in parallel with each other, and second yarns 41 extending across the first yarns 40 (typically at a right angle) and in parallel with each other. A plurality of spaces defined and formed by the first yarns 40 and the second yarns 41 when viewed in plan serve as pores 42. Further, as shown in FIG. 6, the second yarns 41 pass among the first yams 40 alternately to be meandered while the first yarns 40 pass among the second yarns 41 alternately to be meandered, thereby forming a plurality of projections 43 and depressions 44 (namely roughness) in a surface lOa of the base material 10 on which the coating film 11 is to be fonned. As will be described later in detail, the coating film 11 fills the pores 42 (specifically, openings of the pores 42) and flattens the depressions 43 and the projections 44.

[0030] For installing the radio shielding member I including the reflection layer 12 formed on the surface of the base material 10 on an interior existing object (a window, a wall, a ceiling, a floor, a partition, a desk, or the like, for example), the base material 10 may be subjected to, on at least one of the face thereof on which the reflection layer 12 is formed and the opposite face thereof, application of an adhesive or a binder or provision of adsorptive, a protection film is formed on the surface of the adhesive or the binder, and then the base material 10 is rolled (in a form of a toilet paper roll) so as to be capable of being cut into a desired length.

[0031] FiG. 7 to FIG. 10 show the aspects, as products (use states), of the radio shielding member 1 in accordance with the present embodiment. FIG 7 is a sectional view showing the radio shielding member 1 having the base material side attached to a wall, wherein it is attached to the wall 30 through an adhesive 31 provided on the base material 10 side thereof. FIG. 8 schematically shows the radio shielding member I which includes the adhesion 31 and a protection film 32 formed on the base material 10 side thereof and which is rolled into a toilet paper form, wherein the radio shielding member 1 can be cut into a desired length and be attached to a wall or the like with the protection film 32 removed. FIG. 9 is a sectional view showing the radio shielding member 1 having the reflection layer 12 side attached to the wall 30, wherein the adhesive 31 is provided on the reflection layer 12 side thereof. FIG. 10 schematically shows the radio shielding member 1 which includes the adhesive 31 and the protection film 32 formed on the reflection layer 12 side thereof and which is rolled into a toilet paper form, wherein the radio shielding member 1 can be cut into a desired length and be attached to a wall or the like with the protection film 32 removed. Preferably, the base material 10 functions not only as a mere matrix (for example, to secure the mechanical durability of the radio shielding member 1) but also to provide various characteristics to the radio shielding member, such as light transmission, fireproof, fire retardancy, non-halogenation, flexibility, impact resistance, heat resistance, and the like.

[00323 In the present embodiment, the reflection layer 12 selectively reflects a radio wave at a specified frequency. Specifically, the reflection layer 12 is composed of a plurality of antennas 13 two-dimensionally arranged for forming patterns. Each antenna 13 selectively reflects a radio wave at a specified frequency. The plurality of antennas 13 are formed by application of a radio wave reflecting material (preferably in a liquid state).

[0033] The coating film 11 is formed on the surface of the base material 10, in which the plurality of pores are formed, so as to cover the surface thereof. The coating film 11 suppresses penetration of the radio wave reflecting material (for example, a liquid radio wave reflecting material) for forming the antennas 13, which will be described later (for example, impregnation of the radio wave reflecting material (for example, a liquid radio wave reflecting material) in the direction of the surface of the base material), unintentional spread of the radio wave reflecting material (for example, a liquid radio wave reflecting material) on the surface of the base material 10, and the like. The coating film 11 preferably densifies and flattens the surface of the base material 10 (for example, a porous material) in which at least one of a plurality of pores and a plurality of projections and depressions are formed. More preferably, the coating film 11 equalizes the thickness of the base material 10 in addition to densification and flattening of the surface of the base material 10. Preferably, the coating film 11 swells less by the radio wave reflecting material (for example, a liquid radio wave reflecting material), namely, impregnates less the radio wave reflecting material (for example, a liquid radio wave reflecting material).

For example, the coating film 11 may be made of resin, such as urethane resin, acryl resin, polyester resin, or the like.

[0034] A method for manufacturing the radio shielding member 1 in accordance with the present embodiment will be described next. First, the coating film 11 is formed on the base material 10. Specifically, the coating film 11 is formed so as to flatten the surface of the base material 10 in which at least one of a plurality of pores and a plurality of projections and depressions are fonned, or so as to flatten the surface and equalize the entire thickness (the total thickness of the base material 10 and the coating film 11). The coating film 11 can be formed by roIl coating, slit die coating, doctor knife coating, gravure coating or the like.

[0035] Following formation of the coating film 11, the antennas 13 are formed with the radio wave reflecting material (for example, a liquid radio wave reflecting material) to form the reflection layer 12, thereby completing the radio shielding member 1.

Specifically, for example, a liquid radio wave reflecting material is applied and dried (and baked according to needs) to form a plurality of antennas 13, thereby forming the reflection layer 12. Application of the liquid radio wave reflecting material may be mist application, silk-screen printing, spin coating, doctor blade, discharge coating, splay coating, inkjetting, letterpress printing, intagrio printing, screen printing, micro gravure coating, or the like.

[0036] in the case where, for example, a liquid radio wave reflecting material is applied directly on the surface of the base material 10 without forming the coating film 11, the pores in the surface of the base material 10 causes capillarity to allow the liquid radio wave reflecting material to be impregnated into the base material 10 (causes impregnation of the liquid radio wave reflecting material in the direction of the surface of the base material).

As a result, the liquid radio wave reflecting material penetrates. This invites difficulty in formation of the antennas 13 in desired shape and dimension. Specifically, penetration of the liquid radio wave reflecting material causes the shape of the formed antennas 13 to be broad (the line width becomes wide and varies when compared with the design value in the case where the antennas 13 are linear). Further, the shape and the dimension of the antennas vary. Specifically, in the case where the antennas 13 in the present embodiment are in the T-Y shape, the lengths of first element parts 13a and second element parts 13b vary. Furthermore, a part of an antenna 13 may be cut electrically.

[0037] The roughness of the surface of the base material 10 causes the liquid radio wave reflecting material to flow unintentionally from a projection into an adjacent depression or to be gathered in a depression, thereby inviting difficulty in formation of the antennas 13 in desired shape and dimension. In other words, the formed antennas 13 may vary in shape and dimension or may be different in shape and dimension from desired one.

[0038] For example, the antennas 13 may be formed on the base material 10 by a dry method, such as sputtering or the like. In this case, no penetration of the liquid radio wave reflecting material is invited, but large-sized equipment is required to increase the manufacturing cost and to complicate the manufacturing process.

[0039] In contrast, the coating film 11 covers the surface of the base material 10 in the present embodiment. The coating film 11 fills the pores or the depressions formed in the surface of the base material 10 to flatten the surface thereof. Accordingly, penetration of the liquid radio wave reflecting material to the base material 10 (impregnation, especially impregnation of the liquid radio wave material in the direction of the surface of the base material 10) and unintentional flowing of the liquid radio wave reflecting material can be suppressed. Hence, the plurality of antennas 13 in a sharp shape with less variation in shape and dimension (in the case where the antennas 13 are linear, for example, the antennas 13 of which line width is unvarying and of which element parts have the unvarying lengths) can be formed by an antenna forming method using the liquid radio wave reflecting material, which requires no large-sized equipment and can carried out at low cost. Consequently, the radio shielding member 1 in accordance with the present embodiment can be manufactured easily at low cost and have excellent radio shielding characteristics.

[0040] The liquid radio wave reflecting material may be liquid or pasty (hereinafter it may be referred to as a conductive paste) one in and with which particles or colloid substantially made of a radio wave reflecting material, such as a conductive substance or the like are dispersed and mixed, a solution in which a radio wave reflecting material is fused, or the like.

[0041] The conductive material includes aluminum, silver, copper, gold, platinum, iron, carbon, graphite, indium tin oxide (ITO), indium zinc oxide (IZO), a mixture or an alloy thereof, and the like. Among of all, the antennas 13 preferably contain at least one of copper, aluminum, and silver, which have high conductivities and are comparatively low costs.

[0042] As a medium containing the conductive material, there are resin, such as polyester resin and the like, and a solvent, such as an organic solvent, water, and the like. In th e case where the particles containing a conductive material is dispersed in and mixed with resin, the content of the conductive material is preferably in the range between 40 wt% and wt%, both inclusive, more preferably, in the range between 50 wt% and 70 wt%, both inclusive. The content of the conductive material below 40 wt% leads to lowering of the conductivity of the antennas 13, and that over 80 wt% invites difficulty in homogenous dispersion in and homogenous mixing with the resin. The resin may serve as both the conductive material and a binder for binding the base material 10 [0043] The condition for drying (baking) the applied liquid radio wave reflecting material can be determined appropriately according to the compositions of the liquid radio wave reflecting material, wherein it is preferable to dry it, for example, at a temperature in the range between 100 °C and 200 °C, both inclusive, for a time period in the range between ten minutes and five hours, both inclusive.

[0044] In the case where the antennas 13 contain a material comparatively liable to be oxidized, such as silver, an anti-oxidizing film may be formed on the antennas 13 so as to cover the antennas 13.

[0045] Next, a configuration of the reflection layer 12 in the present embodiment will be described further in detail. In the present embodiment, the reflection layer 12 is formed of a plurality of antennas 13 having frequency selectivity and arranged in matrix at regular intervals. Namely, the antennas 13 reflect a radio wave at a specified frequency selectively. Accordingly, the radio shielding member I can shield the radio wave at the specified frequency selectively while transmitting the other radio waves.

[0046] Specifically, as shown in FIG. 4, each antenna 13 includes three first element parts 13a and three second element parts 13b. The three first element parts 13a extend outward from an antenna center Cl at angles of 120 degrees to each other.

[0047] The second element parts 13b are connected to the outer ends of the first element parts 13a. The first element parts 13a preferably have substantially the same length. As well, the second element parts 13b preferably have substantially the same length. This arrangement further enhances the frequency selectivity of the reflection layer 12.

[0048] The length (LI) of each first element part 13a may be different from or equal to the length (L2) of each second element part 13b (LI!= L2 or LI = L2). Preferably, the lengths (Li and L2) of each first element part 13a and each second element part 13b satisf' a relational expression, 0 <L2 <2(3)/L1. When L2 is equal to or larger than 2(3)fL] (L2 �= 2(3)ILl), adjacent second element parts 13b may be in contact with each other to attain no desired radio shielding effects. With a view to attaining a high radio shield factor against a specified frequency, the length (L2) of each second element part 13b is preferably in the range between 0.5 time and 2.0 times, both inclusive, as large as the length (LI) of each first elemeni part 13a (0.5xLl L2 S 2xLl). More preferably, it is in the range between 0.75 time and 2 times, both inclusive (0.75xL1 L2 2xLl).

Referring to each width of the first element parts 13a and the second element parts 13b, they may be different from or equal to each other. In the present embodiment, the width of each first element part 13a is substantially the same as the width of each second element part 13b.

[0049] As described above, each antenna 13 includes the three second element parts 13b connected to the outer ends of the first element parts 13a. Accordingly, each antenna 13 exhibits frequency selectivity higher than a Y-shaped linear antenna and a generally-called Jerusalem cross-shaped antenna (the Y-shaped antenna is a linear antenna composed of only three first element parts extending radially from the antenna center with no second element part included, and the Jerusalem cross-shaped antenna is one including four linear first element parts extending radially from the antenna center at angles of 90 degrees to each other and having the same length and a linear second element part connected to the outer end of each first element part). Hence, the radio shielding member 1 has high frequency selectivity.

[0050] With the second element parts 13b, the plural antennas 13 can be disposed readily in such a fashion that the second element parts 13b of adjacent antennas 13, 13 are opposed to each other (preferably, the opposed second element parts 13b are closed to each other, wherein the interval between the second element parts 13b, 13b is not equal to zero).

The arrangement of the plural antennas 13 in this way further increases the radio shield factor against a radio wave at a specified frequency. In the case where the second element parts 13b are arranged closely so as to be opposed to each other, penetration or flowing of the liquid radio wave reflecting material, if occurs, may lead to connection of opposed second element parts 13b to each other. Connection of the second element parts 13b to each other aftains no desired radio shielding characteristics (radio shield factor and frequency selectivity). In view of this, it is especially effective for arrangement in which the second element parts 13b of adjacent antennas 13 are opposed to each other (and close to each other) to provide the coating film 11.

[0051] For arranging the antennas 13 so that the second element parts 13b are opposed to each other as many as possible per unit area, it is preferable that the second element parts 13b are connected at the centers thereof to the outer ends of the first element parts 13a at a right angle with respect to the associated first element parts 13a. Further, it is preferable that the length of the second element parts 13b is substantially the same as that of the first element parts 13a.

[0052] The lengths of the first element parts 13a and the second element parts 13b correlate to the frequency (the specified frequency) of a radio wave to be reflected by the antennas 13. Accordingly, the lengths of the first element parts 13a and the second element parts 13b can be determined appropriately according to the frequency (the specified frequency) of the radio wave that the radio shielding member 1 is to shield. For example, in the case where lengths of the first element parts 13a and the second element parts 13b are equal to each other, elongation of the lengths of the first element parts 13a and the second element parts 13b can lower the specified frequency. Reversely, shortening of the lengths of the first element parts 13a and the second element parts 13b can increase the specified frequency.

[0053] Detailed description of the radio shielding characteristics of the radio shielding member I will be given with reference to FIG. 11 and FIG. 12, wherein the length (Li) of the first element parts 13a and the length (L2) of the second element parts 13 are equal to each other (herein, Li and L2 are referred to as an element length L correctively). FIG. 11 is a graph showing the relationship between the frequency of the radio wave and the transmission loss where the radio wave transmits through the radio shielding member 1, wherein LI and L2 are 10.6 mm (LI = L2 = 10.6 mm) and the width L3 is 0.7 mm (L3 0.7mm).

[0054] As shown in FIG. 11, the transmittance of the radio wave at a specified frequency (approximately 2.7 GHz) out of the radio waves incident on the radio shielding member 1 is attenuated selectively. In other words, the radio shielding member 1 selectively shields * 18 the radio wave at the specified frequency out of the radio waves incident on the radio shielding member 1. This is because the reflection layer 12 of the radio shielding member 1, specifically, each of the antennas 13 included in the reflection layer 12 selectively reflects the radio wave at the specified frequency out of the incident radio waves. The frequency of the radio wave reflected by the antennas 13 is detennined according to the length LI (=L) of the first element parts 13a and the length L2 (= L) of the second element parts 13.

[0055] FIG. 12 is a graphs showing the relationship between the element length L and the frequency of the radio wave reflected by the antennas 13. As understood from this graph, the longer the element length L is, the lower the frequency of the radio wave reflected by the antennas 13 is. In reverse, the shorter the element length L is, the higher the frequency of the radio wave reflected by the antennas 13 is.

[0056] On the other hand, the frequency of the reflected radio wave does not correlate to the width L3. Namely, the frequency of the reflected radio wave is determined mainly according to the element length L. Accordingly, the frequency (the specified frequency) of a radio wave to be reflected by the antennas 13 can be determined by calculation of the element length L on the basis of the relationship between the element length L and the selected frequency as shown in FIG. 12. For example, It is understood from FIG. 12 that the element length L is set at approximately 6 mm (L 6 mm) for forming the radio shielding member 1 for shielding the radio wave at a frequency of 5 GHz.

[00573 The specified frequency can be adjusted by adjusting the length L2 of each second element part 13b with the length Li of each first element part 13a fixed. Specifically, elongation of the length L2 of each second element part 13b lowers the specified frequency while shortening of the length L2 of each second element parts 13b increases the specified frequency.

[0058] The thickness of the antennas 13 is preferably in the range between 10 J.tm and 20 .un, both inclusive (10 to 20 j.un). The antennas 13 having a thickness smaller than 10 tm invite lowering of the conductivity of the antennas 13 while those having a thickness larger than 20 tm invite lowering of formability of the antennas 13.

[0059) Heretofore, detailed description has been given of the radio shielding member 1 in accordance with the present embodiment, but the shape and the dimension of the radio shielding member 1 is not limited thereto. The radio shielding member 1 may have a size measuring several millimeters, or several meters, or larger par side.

[0060] The radio shielding member 1 may be any arbitrary shape in plan, such as triangle, a quadrilateral (a rectangle or a square), a polygon, a circle, an elliptic, or the like.

[0061] There is no limit of the number of the antennas 13 included per unit area of the radio shielding member 1. The number of the antennas 13 included per unit area of the radio shielding member 1 can be changed appropriately according to the use of the radio shielding member 1. An increase in the number of the antennas 13 included per unit area of the radio shielding member 1 attains further enhanced radio shielding characteristics.

[0062] The present invention is free from limitation on the shape and the dimension of the antennas forming the reflection layer 12, and the antennas 13 described herein are mere examples. In addition, the reflection layer 12 may include, in addition to the plural antennas 13, one or more kinds of antennas different from the antennas 13 in shape and layout.

[0063] As modified examples of the present embodiment, various radio shielding members will be described below of which reflection layers 12 (shape and arrangement of the antennas 13) are different in configuration from each other.

[0064] (Modified Example 1) FIG. 13 is a plan view of a reflection layer 12a in Modified Example 1, and FIG. 14 is a plan view ofa part of the reflection layer 12a in an enlarged scale.

[0065] In Modified Example 1, the reflection layer 12 is so configured that the plural antennas 13 are disposed to form a plurality of antenna groups 15 in matrix at regular intervals. Specifically, each of a plurality of antenna units 14 is formed of a pair of antennas 13 arranged so that the associated second element parts 13b are opposed to each other, and the antenna units 14 are arranged so that the associated second element parts 13b are opposed to each other, thereby forming a plurality of continuously and two-dimensionally developed hexagonal antenna groups 15. More specifically, each antenna group 15 is composed of three antenna units 14 arranged so as to form a ring in which the associated second element parts 13b are opposed to each other. In other words, each antenna group 15 is composed of six antennas 13 annularly arranged so that the associated second element parts 13b are opposed to each other.

[0066] In the case where the second element parts 13b are opposed to each other closely as in Modified Example 1, penetration or unintentional flowing of the liquid radio wave reflecting material, if occurs, may lead to connection of opposed second element parts 13b to each other. This leads to no attainment of desired radio shielding characteristics (radio shield factor and frequency selectivity). For this reason, provision of the coating film 11 is especially effective for arranging the second element parts 13b of adjacent antennas 13 so as to be opposed (closely) to each other.

[0067] In Modified Example 1, 12 second element parts 13b of the 18 second element parts 13b in one antenna group 15 are opposed to each other in parallel with each other.

This arrangement of the antennas 13 in which comparatively many second element parts 13b are opposed to each other further increases the radio wave reflectivity (the radio shield factor) of the antennas 13 against a radio wave at a specified frequency. Hence, the radio shielding member can have a high radio shield factor against the radio wave at the specified frequency.

[0068] The shorter the distance Xl between the opposed second element parts 13b is, the higher the radio wave reflectivity of the antennas (radio shield factor of the radio shielding member) is. Specifically, the distance Xl (see FIG. 14) between the opposed second element parts 13b is preferably in the range between 0.4 mm and 3 mm, both inclusive (0.4 mm S Xl < 3 mm), and more preferably, in the range between 0.6 mm and 1 mm, both inclusive (0.6 mm Xl 1 mm). When the distance Xl is shorter than 0.4 (Xl <0.4 mm), the opposed second element parts 13b may be in contact with each other undesirably.

When the distance Xl is longer than 3 mm (Xl <3 mm), the radio shield factor is liable to lower.

[0069] With a view to attaining stable radio shielding characteristics against the radio waves incident at various incident angles, each antenna group 15 preferably forms a hexagon (more preferably, substantially a regular hexagon). This means that it is preferable that the first element parts 13a and the associated second element parts 13b form right angles. Further, the second element parts 13b are preferably connected at the centers thereof to the first element parts 13a.

[0070] (Modified Example 2) FIG. 15 is a plan view of a reflection layer 12b in Modified Example 2.

[0071] In Modified Example 2, the antenna groups 15 are arranged (in a generally-called honeycombed arrangement) so that more second element parts 13b are opposed to each other. Accordingly, in Modified Example 2, all of the second element parts 13b are opposed to each other. This arrangement of the antennas 13 increases the number of the second element parts 13b opposed to each other when compared with that in Modified Example 1. Hence, the radio shielding member has a further higher radio shield factor.

[00723 When penetration or unintentional flowing of the liquid radio wave reflecting material is caused to allow opposed second element parts 13b to be in contact with each other in the antenna arrangement as in Modified Example 2, no frequency selectivity of the reflection layer 12 may be attained. For this reason, provision of the coating film 11 is significantly effective in this antenna arrangement in Modified Example 2.

[0073] (Modified Example 3) FIG. 16 is a plan view of a reflection layer 12c in Modified Example 3.

[0074] In the example shown in FIG. 1 and Modified Examples I and 2, the reflection layer 12 is composed of antennas of only one kind. While in Modified Example 3, the reflection layer 12c is composed of plural kinds of antennas. Specifically, the reflection layer 12c includes two kinds of antennas 16, 17 of comparatively small antennas 16 and comparatively large antennas 17. The antennas 16 and the antennas 17 are generally-called T-Y-shaped antennas.

[0075] The antennas 16 and the antennas 17 are arranged alternately in matrix so as not to interfere with each other. The antennas 16 and the antennas 17 may be analogous or non-analogous with each other. Further, the reflection layer 12c may additionally include antennas different from the antennas 16 and the antennas 17.

[0076] The comparatively small antennas 16 and the comparatively large antennas 17 are different in frequency selectivity from each other. Namely, the frequencies of the reflected radio waves are different from each other. Accordingly, the radio shielding member can selectively shield two radio waves of which frequencies are different from each other.

[0077] For example, a wireless LAN uses radio waves at two frequencies, a radio wave in a frequency band of 2.4 0Hz and a radio wave in a frequency band of 5.2 0Hz. The radio shielding member in accordance with Modified Example 3 is especially useful in environments using radio waves at two frequencies, such as an environment using a wireless LAN or the like.

[0078] In an environment in which radio waves at three or more frequencies are used, the reflection layer 12c may be composed of three or more kinds of antennas different in size from each other.

[0079] (Modified Example 4) FIG. 17 is a plan view of a reflection layer 12d in Modified Example 4.

[0080] In Modified Example 4, similarly to those in Modified Example 2, each of a plurality of antenna units 18 is formed of a pair of antennas 16 arranged so that the associated second element parts 16b are opposed to each other, and the antenna units 18 are arranged so that the associate second element parts 16b are opposed to each other, thereby forming a plurality of continuously and two-dimensionally developed hexagonal antenna groups 19. Namely, each antenna group 19 is composed of three antenna units 18 arranged annularly so that the second element parts 16b are opposed to each other. In other words, each antenna group 19 is composed of six antennas 13 arranged annularly so that the second element parts 16b are opposed to each other. The antenna groups 19 are arranged (in a generally-called honeycombed arrangement) so that the second element parts 16b are opposed to each other.

[0081] On the other hand, each of a plurality of antenna units 20 is formed of a pair of antennas 17 arranged so that the associated second element parts 17b are opposed to each other, and the antenna units 20 are arranged so that the associated second element parts 17b are opposed to each other, thereby forming a plurality of continuously and two-dimensionally developed hexagonal antenna groups 21, similarly to the antennas 13 in Modified Example I. Each antenna group 21 is arranged so as to be surrounded by an antenna group 19. In this arrangement, the second element parts 16b of the antennas 16 are opposed to each other and the second element parts 17b of the antennas 17 are opposed to each other at respective high probabilities to attain arrangement of the antennas 16 and 17 at substantially the same density. Accordingly, both the radio wave that the antennas 16 reflect and the radio wave that the antennas 17 reflect can be shielded at higher frequency selectivity and a higher radio shield factor.

[0082] In Modified Example 4, as in Modified Examples I and 2, penetration or unintentional flowing of the liquid radio wave reflecting material, if occurs, may allow opposed second element parts 13b to be in contact with each other to attain no desirable radio shielding characteristics. Hence, provision of the coating film 11 is effective.

[0083] In Modified Example 4, it is preferable that each length of second element parts 16b, 17b is comparatively short. This suppresses contact between the antennas 16 and the antennas 17. This increases, in turn, the degree of freedom of dimension design of the antennas 17 forming the antenna groups 21 surrounded by the antenna groups 19. As a result, a radio shielding member can be realized which is capable of selectively shielding two radio waves of which frequencies are comparatively close to each other.

[0084] (Modified Example 5) FIG. 18 is a plan view of a reflection layer 12e in Modified Example 5.

[0085] Modified Example 5 is a modification of Modified Example 4. In Modified Example 5, the antenna groups 19 and the antenna groups 21 are disposed aslant with respect to each other so as to include symmetric axes different form each other (specifically, axes of line symmetry extending in the directions in which the antennas 16 and 17 are arranged).

[0086] In order to surround the antenna groups 21 by the antenna groups 19, it is necessary to set the dimension of the antennas 17 forming the antenna groups 21 smaller than that of the antenna 16 forming the antenna groups 19. When the antenna groups 19 and the antenna groups 21 are arranged not aslant, as depicted in Modified Example 4, the antennas 17 must be much smaller than the antennas 16 for avoiding interference of the antennas 17 with the antennas 16 to reduce the degree of freedom of the design of the antennas 16 and 17.

[0087] In contrast, in Modified Example 5, when the antenna groups 19 and the antenna groups 21 are disposed asla.nt (for example, 8 = 100 as in FIG. 18), the position of opposed second element parts 16b relative to the position of opposed second element parts 17b are displaced. Accordingly, in Modified Example 5, the relative size of the antennas 17 can be set comparatively larger than the size of the antennas 16 when compared with the case depicted in Modified Example 4. This increases the degree of freedom of the design in shape and dimension of the antennas 16 and 17. As a result, two radio waves of which frequencies are close to each other (a ratio of a first frequency to a second frequency larger than the first frequency is 0.45 or larger) can be shielded.

[0088] FIG. 18 shows a case in which the substantially hexagonal antenna groups 19 and 21 are disposed the most close to each other. According to a desired radio shield factor, each number of the substantially hexagonal antenna groups 19 and 21 may be adjusted appropriately without disposing them the most closely.

[00893 (Modified Example 6) In Modified Example 6, the refection layer is composed of plural kinds of antennas which selectively reflect radio waves of which specified frequencies are different from each other so as to be capable of selectively shielding the radio waves in a specified frequency band, which well be described below. Specifically, description will be given of a reflection layer 12f composed of three kinds of antennas 22a, 22b, 22c.

[0090] The frequency band means a frequency range of which fractional bandwidth exceeds 10 %. The radio shielding member selectively shielding the radio waves in a specified frequency band means a radio shielding member of which 10 dB fractional bandwidth (preferably, 20 dB fractional bandwidth, and more preferably, 30 dB fractional bandwidth) exceeds 10 %. In contrast, the radio shielding member selectively shielding a radio wave of a specified frequency means a radio shielding member of which 10 dB fractional bandwidth is equal to or lower than 10 %. The fractional bandwidth of 10 dB is expressed by 2(FmaxFmin)/(Fmax+Fmjn) where Fm is a maximum value of the frequency of the radio wave shielded over 10 dB and Fmjn is a minimum value thereof.

[0091] A configuration of the reflection layer 12f in Modified Example 6 will be described below with reference to FIG. 19. FIG. 19 is a plan view of the reflection layer 12f.

[0092] The reflection layer 12f is composed of plural kinds of antennas 22, specifically, the first antennas 22a, the second antennas 22b, and the third antennas 22c which selectively reflect radio waves of specified frequencies different from each other. The first antennas 22a, the second antennas 22b, and the third antennas 22c have radio reflection spectrum peaks not independent of each other. In other words, their radio reflection spectrum peaks are continuous. Accordingly, the reflection layer 2f in accordance with the present modified example can selectively reflect radio waves in a frequency band having a predetermined width (for example, a frequency band in the range between 815 MHz and 925 MHz, both inclusive). For example, the reflection layer 12f has the radio shielding characteristics (radio transmission loss) shown in FIG. 20. With a view to attaining excellent continuity of the radio reflection spectrum peaks, it is preferable to set the dimension of the respective antennas 22 of the reflection layer 12f within � 15 % (preferably, � 10 %, and more preferably, �5 %) of the dimension of antennas 22 of a reference type out of the antennas 22.

[0093] FIG. 20 is a graph showing the correlation between the radio shielding amount (radio transmission loss) of the reflection layer 12f and the frequency. As shown in the graph, a spectrum peak P2 of the first antennas 22a, that P3 of the second antennas 22b, and that P1 of the third antennas 22c are not independent of each other and are continuous.

Specifically, a ratio of the depth H2 of the valley from the base line BL to the depth Hi of P1, the highest peak, from the base line BL is equal to or smaller than 50 % (3 dB or higher). Accordingly, the reflection layer 12f shields (reflects) the radio waves in the entire range of the frequency band between the peaks P1 and P3 at a high radio shield factor of 10 dB or higher. The fractional bandwidth of 10 dB is preferably larger than 10%.

[0094] The wording, "the radio reflection spectrum peaks are not independent of each other (continuous)" means that a ratio of the minimum radio reflection (shield) factor at a valley between spectrum peaks to the radio reflection (shield) factor at a peak of the largest spectrum out of the radio reflection (shielding) spectrums of the radio shielding member exceeds 50 % (difference between the radio reflection (shield) factor at the peak of the largest spectrum and the lowest radio reflection (shield) factor at a valley is smaller than 3 dB). The wording, "the radio reflection spectrum peaks are independent of each other (not continuous)" means that that a ratio of the minimum radio reflection (shield) factor at a valley between spectrum peaks to the radio reflection (shield) factor at a peak of the largest spectrum out of the radio reflection (shielding) spectrums of the radio shielding member is 50 % or lower (difference between the radio reflection (shield) factor at the peak of the largest spectrum and the minimum radio reflection (shield) factor at a valley is 3 dB or larger).

[0095] The first antennas 22a, the second antennas 22b, and the third antennas 22c are in T-Y-shapes as described in Modified Example 6, but each of them may be a Y-shaped antenna, a generally-called Jerusalem cross-shaped antenna, or the like. Alternatively, first antennas 22a, the second antennas 22b, and the third antennas 22c may be antennas in different shapes from or in analogous shapes with each other.

[0096] Arrangement of the antennas 22 in Modified Example 6 will be described next.

As shown in FIG. 19, in the reflection layer 121, the first antennas 22a, the second antennas 22b, and the third antennas 22c are arranged alternately and two-dimensionally in one direction in this order to form a plurality of antenna rows 23. In other words, the refection layer 12f is composed of a plurality of antenna rows 23 each formed of the first antennas 22a, the second antennas 22b, and the third antenna s 22c arranged alternately in this order in one direction.

[0097] In the reflection layer 121, each first antenna 22a is adjacent to second antennas 22b and third antennas 22c belonging to antenna rows 23 adjacent to an antenna row 23 to which the associated first antenna 22a belongs. Similarly, each second antenna 22b is adjacent to first antennas 22a and third antennas 22c belonging to antenna rows 23 adjacent to an antenna row 23 to which the associated second antenna 22b belongs. Each third antenna 22c is adjacent to first antennas 22a and second antennas 22b belonging to antenna rows 23 adjacent to an antenna row 23 to which the associated third antenna 22c belongs. In other words, a triangle (preferably a regular triangular) is formed by the antenna centers of a first antenna 22a and those of adjacent first antennas 22a belonging to antenna rows 23 on the respective sides of an antenna row 23 to which the first antenna 22a belongs. Further, a triangle (preferably a regular triangular) is formed by the antenna centers of a second antenna 22b and those of adjacent second antennas 22b belonging to antenna rows 23 on the respective sides of an antenna row 23 to which the second antenna 22b belongs. As well, a triangle (preferably a regular triangular) is formed by the antenna centers of a third antenna 22c and those of adjacent third antennas 22c belonging to antenna rows 23 on the respective sides of an antenna row 23 to which the third antenna 22c belongs.

[0098] With the above arrangement, the plurality of antenna rows 23 can be arranged in rows closely so that, for example, the second element part of a first antenna 22a gets in between a second antenna 22b and a third antenna 22c belonging to an adjacent antenna row. in other words, the antennas 22 can be arranged closely so that the second element parts of adjacent antennas 22 get into a region R where a first antenna 22a is arranged, as shown in FIG. 19. Thus, much amount of the antennas 22a, 22b, 22c can be disposed closely per unit area.

[0099] The radio shield factor correlates to the number of antennas 22 per unit area, and namely, an increase in the number of antennas 22 per unit area increases the radio shield factor. Accordingly, the arrangement of the antennas 22 in Modified Example 6 attains a further higher radio shield factor. Further, the numbers of the first antennas 22a, the second antennas 22b, and the third antennas 22c per unit area can be set approximately equal to each other to suppress radio shielding irregularity in a frequency band. With a view to further increasing the number of antennas 22 per unit area, the second element parts are preferably shorter than the first element parts (L2> Li).

[0100] In the arrangement of the antennas 22 in Modified Example 6, the antennas 22 are arranged so that the second elements are opposed not in parallel to each other. This keeps the frequency selectivity of the antennas 22 comparatively low. in other words, the fractional bandwidth of the antennas 22 can be kept comparatively wide. Hence, a less biased high radio shield factor against radio waves in an entire specified frequency band can be attained.

[0101] In the antenna arrangement in Modified Example 6, the second element parts of antennas arranged adjacent to each other are not opposed to each other. This hardly leads to contact between the second element parts 131, of antennas 22 adjacent to each other. In the case where the number of the antennas 22 per unit area is increased by closely arranging them for attaining excellent radio shielding characteristics, however, a first element part and a second element part of an adjacent antenna may come in contact with each other to attain no desired radio shielding characteristics. Further, the reflection layer 12f in Modified Example 6 reflects the radio waves in a specified frequency band, and therefore, variation in length of the first element parts or the second element parts, if any, causes no attainment of desired frequency selectivity even through the frequency selectivity thereof is lower than that of the reflection layer in the above embodiment and the like. For this reason, provision of the coating film 11 is effective even in the antenna arrangement in Modified Example 6.

[0102] (Modified Example 7) Heretofore, the reflection layers 12 of T-Y-shaped antennas have been described.

The reflection layer 12 may be composed of antennas other than such T-Y-shaped antennas.

For example, as shown in FIG. 21, a reflection layer 12g may be composed of a plurality of Y-shaped antennas 24 arranged in matrix. Each antenna 24 is composed of three linear first element parts 24a radially extending from the antenna center at angles of 120 degrees to each other and having substantially the same length.

[0103] Even in the case where the Y-shaped antennas are arranged in this way, penetration or unintentional flowing of the liquid radio wave reflecting material, if occurs, causes variation in length of the first element parts 24a to attain no desired radio shielding characteristics. For this reason, even in the case where the Y-shaped antennas are arranged as in the reflection layer 12g. provision of the coating film 11 is effective.

[0104] (Modified Example 8) Modified Example 8 is a modification of Modified Example 7. While the reflection layer 12g in Modified Example 7 is composed of only one kind of antennas 24, a S 30 reflection layer 12h is composed of two kinds of Y-shaped antennas 25, 26 different in size from each other in Modified Example 8. With this arrangement, a radio shielding member can be realized which is capable of shielding plural kinds of radio waves of which frequencies are different from each other.

[0105] As shown in FIG. 22, in Modified Example 8, comparatively large antennas 25 are arranged so that the first element parts thereof are opposed to each other. Specifically, the three first element parts of an antenna 25 are closely opposed to the first element parts of antennas 25 different from each other and in parallel with each other. In each hexagonal region defined and formed by the comparatively large antennas 25, one comparatively small antenna 24 is arranged. With this arrangement, the radio shield factor of the antennas 25 against a radio wave at a specified frequency increases.

[0106] in Modified Example 8, the first element parts of antennas 25 are opposed to each other closely, so that penetration and unintentional flowing of the liquid radio wave reflecting material, if occurs, are liable to invite contact between adjacent antennas 25.

Accordingly, provision of the coating film 11 is effective in the antenna arrangement in

Modified Example 8.

[0107] (Modified Example 9) FIG. 23 is a plan view of a reflection layer 12i in Modified Example 9.

[0108] In Modified Example 9, the reflection layer 12i is composed of a plurality of generally-called Jerusalem cross-shaped antennas 27. Each antenna 27 includes four linear first element parts 27a extending radially from the antenna center at angles of 90 degrees to each other and having substantially the same length and a linear second element part 27b connected to the outer end of each first element part (typically, perpendicularly).

This reflection layer of the antennas 27 attains frequency selectivity higher than the reflection layers of the Y-shaped antennas as described in Modified Examples 7 and 8, wherein the frequency selectivity thereof is lower than that of a reflection layer of generally called T-Y-shaped antennas. S 31

[01093 The antennas 27 are arranged in matrix so that the second element parts 27b of adjacent antennas 27 are opposed to each other (more preferably, in parallel with each other closely). With this arrangement, the radio shield factor of the antennas 27 against a radio wave at a specified frequency can be increased further.

[0110] As described above, even in the arrangement of the Jerusalem cross-shaped antennas, variation in length of the element parts leads to no desired radio shielding characteristics, similarly to the arrangements of the T-Y-shaped antennas and the Y-shaped antennas. Accordingly, provision of the coating film 11 is effective even in the arrangement of Jerusalem cross-shaped antennas as in the reflection layer 12i.

[0111] (Modified Example 10) FIG. 24 is a plan view of a reflection layer 12j in Modified Example 1 0 [0112] Modified Example 10 is a modification of Modified Example 9. While only one kind of antennas 27 compose the reflection layer 12i in Modified Example 9, the reflection layer 12j is composed of two kinds of Jerusalem cross-shaped antennas 28, 29 different in size from each other. With this arrangement, a radio shielding member can be attained which is capable of shielding plural kinds of radio waves of which frequencies are different from each other.

[0113] As shown in FIG. 24, in Modified Example 10, the antennas 28 are arranged in matrix so that the second element parts 28b of adjacent antennas 28 are opposed to each other (preferably, in parallel to with each other closely). In each region defined and formed by comparatively large antennas 28, one comparatively small antenna 29 is arranged.

[01143 With this arrangement, the radio shield factor of the antennas 28 against radio waves at specified frequencies increases thrther.

[01153 In the antenna arrangement in Modified Example 10, penetration or unintentional flowing of the liquid radio wave reflecting material, if occurs, may cause second element parts 28b closely opposed to each other to come in contact with each other. As well, a second element part 29b of an antenna 29 may come in contact with a second element part 28b of an antenna 28 close to the antenna 29. Accordingly, provision of the coating film 11 is effective also in the antenna arrangement as in Modified Example 10.

[0116] (Modified Example 11) FIG. 25 is a plan view of a reflection layer 12k in Modified Example 11.

[0117] Modified Example 11 is a modification of Modified Example 10, of which difference from Modified Example 10 is only arrangement of the antennas 28, 29.

[0118] In Modified Example 11, rows of antennas 28 and rows of antennas 29 are arranged vertically alternately in FIG. 25, wherein each row of the antennas 28 is an arrangement in which transversely adjacent second element parts 28b are opposed to each other (preferably, in parallel with each other closely) while each row of the antennas 29 is an arrangement in which second element parts 29b are opposed to each other in the same direction (preferably, in parallel with each other closely). This increases the radio shield factors of the antennas 28 and 29 against radio waves at respective specified frequencies.

[0119] Similarly to the case of Modified Example 10, it is effective to provide the coating film 11 so as not to cause contact between second element parts 28b, between second element parts 29b, and between second element parts 28b and second element parts 29b and so as not to cause variation in length of the respective element parts.

Working Example

[0120] The radio shielding member shown in FIG. 15 (Modified Example 2) was prepared as a working example. Specifically, the surface of a fabric (base material), #071 7-CU (beige; a product by Ioyo Senka Kabushiki Kaisha) was coated with urethane resin by using a roll coater first.

[0121] Next, antennas were formed on the surface of the fabric coated with the urethane resin by screen printing using a silver paste obtained by dispersing and mixing silver powder of 63 wt% into and with polyester rein. Less or no penetration of the silver paste was observed in the thus formed antennas. Each line width of the first element parts and the second element parts was set at 1.58 mm while the lengths of the first element parts and the second element parts were set at 12.94 mm and 9.32 mm, respectively.

[0122] The transmission loss of the thus obtained radio shielding member was measured with the use of a network analyzer, a product of Agilent Technologies Inc. [0123] As a comparative example, a radio shielding member was prepared by the same maimer as in the above working example except that the coating film of urethane resin was not formed, and the transmission loss thereof was measured likewise. In the comparative example, penetration of the silver paste was observed in the thus formed antennas.

[0124] FIG. 26 is a graph showing each transmission loss in the working example and the comparative example. As can be understood from the graph, a high peak was observed around 2.4 0Hz in the working example. This proved that the working example exhibits comparatively high frequency selectivity. In contrast, the comparative example showed slightly high transmission loss around 2.4 GHz and indicated no peak-like peak. This proved that the comparative example has less or no frequency selectivity.

[0125] According to the above results, it was proved that resin coating on the surface of the fabric prior to antenna formation suppresses penetration of the silver paste, thereby attaining a radio shielding member having high frequency selectivity.

Industrial Applicability

[0126] As described above, the radio shielding member in accordance with the present invention has excellent radio shielding characteristics against a radio wave at a specified frequency and is therefore useful as a radio shielding member of a wall paper, a partition, cloth (roller screen), window glass, an exterior wall panel, a roof panel, a ceiling panel, an interior vall panel, a floor panel, and the like.

Claims

[1] A radio shielding member comprising: a base material having a surface in which at least one of a plurality of pores and a plurality of projections and depressions are formed; a coating film formed on the surface of the base material; and a plurality of radio wave reflecting antennas formed with a radio wave reflecting material as a use material on the coating film.

[2] The radio shielding member of claim 1, wherein the base material is made of fabric.

[3] The radio shielding member of claim 1, wherein the coating film is substantially made of resin.

[4] The radio shielding member of claim I, wherein the radio wave reflecting material contains a conductive material.

[5] The radio shielding member of claim I, wherein each of the radio wave reflecting antennas includes: three linear first element parts which extend radially from the center of an associated antenna at angles of approximately 120 degrees to each other and which have substantially same length; and a linear second element part which is connected to an outer end of each of the first element parts.

[6] A method for manufacturing a radio shielding member including: a base material having a surface in which at least one of a plurality of pores and a plurality of projections and depressions are formed; and a plurality of radio wave reflecting antennas formed above the base material, comprising the steps of: covering the surface of the base material with a coating film; and thereafter forming the plurality of radio wave reflecting antennas with the use of a radio wave reflecting material.