JP3079364B2 - Window glass with electromagnetic shielding performance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a window glass used for a window of a building, a window glass of a vehicle such as an automobile or a train, and a window glass of a furniture such as a partition or a box. For those with shielding performance.

[0002]

2. Description of the Related Art The need for electromagnetic shielding inside buildings, buildings, or vehicles is due to frequency reuse, such as when a personal portable device using wireless technology is used within a legally regulated framework. It is required for the purpose of measures against radio wave interference and communication security.

For example, in a specific building, a business PHS
In the case of setting up (self-employed—for indoor use only) or Wireless-LAN (wireless LAN), both are manufactured based on technical standards, their technical contents are disclosed, and measuring instruments for analysis are commercially available. The communication information used for is easily accessed from outside, and the contents of the communication can be intercepted.

In PHS terminals that are also used for public use, it is very difficult to protect the leakage of communication contents by encryption or the like. Therefore, in order to maintain security, generally only an electromagnetic shield for preventing radio waves from leaking outside the communication area is used. There is no.

[0005] Further, since available frequency channels are limited, it is necessary to provide a shield for confining radio waves in accordance with a use area in order to secure the maximum number of use.

[0006] Further, the necessity of the electromagnetic shield is required when an electromagnetic wave interferes with a medical device or a patient in a medical field such as a hospital to cause an obstacle, or when another person uses a mobile phone in a public area such as a restaurant or a vehicle. It is also required to prevent inconvenience, and to prevent the operation of the mobile phone when the audience is required to be quiet in a concert hall or the like.

Electromagnetic shields for radio waves are already widely used even today, and much research has been done on metal plates, metal meshes, or radio wave absorbers. For example, as an electromagnetic shield for building structures, conventionally, each floor surface can be adequately shielded with a deck plate or other iron plate, and copper foil or metal mesh should be stuck on the external wall and partitions between tenants without gaps Thus, effective electromagnetic shielding can be performed even in the microwave band.

[0008]

On the other hand, it is difficult to shield the glass window from electromagnetic waves because the glass window ensures light transmission. Therefore, in order to perform electromagnetic shielding, there is a case where a window in each room of a building is completely eliminated to form a wall surface, and the wall surface has the above-mentioned electromagnetic shield structure. The result is a forced environment.

In order to provide an electromagnetic shielding structure to a window glass, a wire mesh is sometimes inserted inside the window glass. For example, in the electromagnetic shielding of a radio wave (frequency of 1.9 GHz band) used in PHS, it is about 0.1 mm. A very fine mesh is required, and although electromagnetic shielding is performed, transparency is impaired, and it cannot be said that the living environment is good.

As another example of applying an electromagnetic shield structure to a window glass, a very thin metal vapor-deposited film of tungsten, aluminum, or the like is laminated on the entire surface or inside of the glass, which is in practical use. In this method PHS
(1.9 GHz) or a wireless LAN (2.45 GHz) is known to be able to be attenuated to a maximum of 20 to 30 dB (= 1/100 to 1/1000). According to this, there is no restriction on visibility because visible light is reduced by only 30 to 35%.

However, although this method can shield the invading radio waves from the outside to some extent without impairing the feeling of openness of a building with daylighting, it can block radio waves in all frequency ranges. However, ordinary communications that would otherwise be difficult to shield, such as public cellular phones, pagers, various broadcasts, police and fire department emergency communications, cordless telephones, and other everyday communications would be blocked.

An object of the present invention is to eliminate the disadvantages of the prior art and to provide electromagnetic shielding by selecting only a radio wave band of a required frequency without impairing lighting and visibility. It is an object of the present invention to provide a window glass having an electromagnetic shielding performance that does not require conducting or grounding treatment with a conductive material in a gap between electromagnetic shielding members such as a metal sash.

[0013]

In order to achieve the above object, the present invention firstly employs a linear antenna element having an open end and a length that resonates with a radio wave to be shielded as an electromagnetic shielding element. Considering the electromagnetic field reflection equivalent area (scattering aperture area) or the electromagnetic field reflection equivalent volume (scattering aperture volume) of the element, and making the end of each side close to the center of the adjacent linear antenna element, Arrange between glass plates,
The gist is to scatter and attenuate radio waves with the linear antenna element.

Second, the length of one side (electric length) of the linear antenna element extending from the center is set to 1/4 wavelength of the radio wave to be shielded (1/2 wavelength in the case of a single shape). Third, the linear antenna elements are composed of a plurality of types so that a plurality of frequencies can be shielded, and two or more types of linear antenna elements having different dimensions and shapes are combined and arranged.
In addition, the gist of the present invention is to combine a plurality of linear antenna elements having different lengths between open-ended linear antenna elements so as to shield a plurality of frequencies.

Fifth, the linear antenna elements determine the arrangement interval in consideration of the relationship between attenuations. Sixth, the linear antenna elements have a volume resistivity of at least 5 × 10 ^−8.
(Ω · m) or less. Seventh, the linear antenna element is made of a material having excellent conductivity, durability, and weather resistance;
The gist is to mix a small amount of glass.

According to the first and second aspects of the present invention, in the linear antenna element, not only the area occupied by the metal portion of the antenna reflects electromagnetic wave energy but also a certain range of electromagnetic waves near the metal portion. Reflect the field over a wide area. Electromagnetic shielding can be achieved by arranging the linear antenna elements in a space or on a non-conductive material in a plane or three-dimensional manner in consideration of the electromagnetic field reflection equivalent area or equivalent volume. In addition, since there is an interval and the entire surface is not covered, the lighting and visibility are not impaired.

In addition, by specifying the length of the patterned small linear antenna element, a specific frequency can be shielded, and as a result, other radio waves can be passed. It does not block radio waves such as radio waves that need to be collected from outside, prevents leakage of only specific radio waves used inside the building, enhances security, and allows frequency channels to be reused.

As described above, most of the linear antenna element is shielded by reflection loss, while most of the absorbed (received) power is absorbed as heat loss. There is no need to conduct the ground to a metal sash or the like, and the setting can be freely performed without being limited to the conductive connection.

Further, in actual radio waves, the plane of polarization is not uniform but has various inclinations. However, by forming the linear antenna element into an annular line shape or an end-opened shape having directionality, all the planes of polarization can be obtained. We can cope with electric wave.

In addition, by arranging the linear antenna element at a place where the electric field is high and at a place where the electric field is low, it is possible to prevent the places where the electric field is high from being close to each other and prevent mutual interference between the elements. Further, the element density can be increased and the degree of attenuation can be increased.

According to the third and fourth aspects of the present invention, it is possible to electromagnetically shield radio waves in a plurality of frequency bands by combining and regularly arranging linear antenna elements having different lengths. In this way, it is possible to cope with a wide range by specifying the radio wave to be shielded in a plurality of frequency bands.
For example, for mobile phones, the 900 MHz band and 1.5
Electromagnetic shielding can be applied to all of the two frequency bands assigned to the GHz band.

To secure a high attenuation, it is desirable to arrange the linear antenna elements as close to each other as possible. On the other hand, if the linear antenna elements are arranged closer to the glass surface than necessary, visual problems (obstruction) occur. Let it. According to the present invention, it is found that there is a correlation between the arrangement interval of the linear antenna elements and the relationship between the attenuation and the arrangement interval between the linear antenna elements is determined from the required attenuation. By doing so, a large gap is secured between the linear antenna elements as much as possible, and better visibility can be secured on the glass surface.

In order to ensure a high attenuation, it is desirable to minimize the loss resistance of the linear antenna element. For this purpose, it is desirable to reduce the loss resistance by increasing the line width. However, increasing the line width of the linear antenna element impairs the optical transparency of the glass surface when the linear antenna elements are arranged. According to the present invention, when the linear antenna element has a line width of about 0.5 mm, it is preferable that the volume resistivity is set to 5 × 10 ⁻⁸ (Ω · m) or less to obtain sufficient performance. Can be secured.

Similarly, it is desirable to use a material having a low electric resistance in order to minimize the loss resistance of the linear antenna element in order to secure a high attenuation. The material of the linear antenna element is optimally copper, silver or gold, but gold is expensive and copper has an increase in resistance due to oxidation. Claim 7
According to the present invention described above, silver is used, which is not so expensive and does not increase the resistance value due to oxidation, and is integrated with glass by mixing a small amount of glass, for example, about 5%. The life of the linear antenna element can be made substantially the same as that of glass.

[0025]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a perspective view showing a first embodiment of a window glass having electromagnetic shielding performance according to the present invention, in which 1 is a window glass, 2 is a sash frame, and a length corresponding to the frequency of a radio wave to be shielded. Are arranged regularly on the window glass 1 in consideration of the electromagnetic field reflection equivalent area or volume, and the linear antenna element 5 attenuates radio waves.

First, the basic principle related to the present invention will be described. When a radio wave is incident on this surface when the conductor piece is in the air, one part is reflected, one part is absorbed, and the other is transmitted.
The amount of attenuation of the radio wave by the conductor piece differs depending on the shape and size of the conductor piece. If this conductor piece is a linear antenna element (dipole) 3 having an open end as shown in FIG. 3, a radio wave is reflected and a part is absorbed.

As shown in FIG. 4, a half-wavelength (λ / 2) linear antenna element (dipole) 3 placed parallel to a plane electromagnetic field receives electromagnetic wave energy only in the area of the metal part of the antenna element. Instead, it absorbs the electromagnetic field near the metal surface. Although the spread is not uniform, the calculated value of the equivalent cross-sectional area Ae is expressed by the following equation 1.

[0028]

[Formula 1] Ae ≒ 0.13λ ² (area of λ / 2 × λ / 4)

Approximately 3 of the electromagnetic wave in the range of the equivalent sectional area Ae
/ 4 is reflected, and the remaining １ ／ becomes the reception power. This is the effective aperture.

As shown in FIG. 5, such a half wavelength (λ
/ 2) When the input resistance of the linear antenna is set to zero,
If the antenna element has no ideal loss, all the power is reflected to the space, and the equivalent area is four times the effective aperture (scattering aperture). When arranged on the window glass 1 as shown in FIG. 6 in accordance with the equivalent area 4 × Ae (scattering aperture), a radio wave reflection effect similar to a metal film is exhibited. The antenna element generally has frequency dependency, and its characteristics and the receiving end resistance = 0 are the basic operations of the element by the linear antenna element 3, and if the linear antenna has a loss, a part of the radio wave will have a power As absorbed by the antenna loss resistance.

Moreover, since the linear antenna elements 3 are scattered, the lighting and visibility of the window glass 1 are not impaired. Note that the thickness of the conductive wire forming the linear antenna element 3 is selected to be thin and small in loss so as not to obstruct the view.

By the way, 1885 to 1950 MHz is the current personal communication (PHS-JAPAN., PCS-US. DECT-Europe) and FPLMTS (Future Public Land) which will be practical from 2000 AD.
Mobile Telephone System)
2480MHz is ISM (Industrial-Scien) defined by ITU
tific-Medical --- Industrial, scientific, and medical) frequency bands are allocated to wireless LANs in buildings, and are also used in microwave ovens and high-power linear accelerators for nondestructive testing.

In the case of the PHS, if the frequency is 1.90 GHz, the wavelength is λ = about 158 mm. In the case of the wireless LAN, if the frequency is 2.45 GHz, the wavelength is λ = about 122 mm.
Therefore, each linear antenna element 3 has an area of 4 × Ae
= 12,980 mm ² (PHS), 4 x Ae = 7,740 mm ² (LA
N), which may be regularly arranged, that is, scattered, in consideration of the electromagnetic field reflection equivalent area 4 × Ae between glass surfaces or glass plates.

However, if the linear antenna elements 3 are arranged in a horizontal line as shown in FIG. 6, the actual plane of polarization of the radio wave is not such a horizontal line, and cannot cope with various polarization planes. Therefore, the linear antenna element 3 is formed into an end-opened shape having a directivity as described later or an annular line shape. By doing so, it is possible to cope with radio waves having different inclinations on all surfaces.

FIGS. 1 and 2 show a first embodiment of the present invention. The linear antenna element 5 has an open end, the wavelength of the electromagnetic wave to be shielded is λ, and the linear antenna element is formed on the glass surface. When the equivalent relative permittivity when the
It was assumed that the element was an inverted Y-shaped element having a side length of approximately λ / (4√εq). That is, since .epsilon.q is 1 in the air, the length of one side of the linear antenna element 5 extending from the center 5a is a quarter wavelength of the radio wave to be shielded. However, when this linear antenna element 5 is arranged on glass, the length of one side changes depending on the glass and the inductive ratio of the boundary surface.

The window glass 1 on which the linear antenna element 3 and the linear antenna element 5 are provided is preferably float glass, gray pen glass, or the like. As a method of regularly arranging the antenna elements 5 in consideration of the equivalent electromagnetic field reflection area of the antenna element, a method of printing a metal paste of silver, copper, gold, or the like on a metal paste or attaching a film film can be considered. .

Among these, the attachment of the film film can prevent scattering when the glass is broken and can adjust the amount of solar radiation. Further, additional construction can be performed after construction, and it is a relatively inexpensive method. As a film material, a linear antenna element 5 is provided as a line pattern on a synthetic resin film such as a polyimide film, a polyester film, or a polyethylene film by an etching method, a laminating method, or a screen printing method, and this is adhered to glass or the like.

The etching method is the same as a general printed circuit board in which a film serving as a flexible board and a copper foil adhered thereto are used as a base material, the pattern portion is masked, and the remaining portion is dissolved with a solvent. . On the other hand, the screen printing method forms a line pattern by printing a metal paste such as silver or gold on a base material.

FIG. 7 shows an experimental result obtained by firing and printing the linear antenna element 5 with a silver paste on the glass surface in order to confirm the performance of the electromagnetic wave shielding glass having the Y-shaped linear antenna element 5 disposed thereon. .

The maximum attenuation is 35 dB (center frequency 1.9).
GHz) and the targeted 30 dB attenuation bandwidth is 35M
Hz, and it was confirmed that the shielding performance was sufficient for the PHS radio wave use band.

Table 1 below shows the specifications of the glass, and Table 2 shows an outline of the experiment.

[0042]

[Table 1]

[0043]

[Table 2]

FIG. 8 shows a case where the linear antenna element 5 is a quadrilateral, that is, a cross-shaped element. In this case, center 5
a is a place where the potential is low, and the end of each side 5b is a place where the potential is high. In the case of FIG. 2 as compared with the case of FIG. 8, a triangular shape in which the high potential portion and the low potential portion of the linear antenna element 5 are close to each other is arranged, so that the high potential portions are close to each other, and Interference can be prevented. The element density can be increased by arranging the elements as triangles.

FIG. 9 shows a linear antenna element 5 having an open end.
The following shows a further modified example. Among them, the one-letter type shown on the left has the same length as the half wavelength of the radio wave to be shielded.

The window glass 1 on which the linear antenna elements 5 are arranged is abutted with a glass (a gap between the glass).
It has been confirmed from the experimental results that even if there is a portion where the antenna element 5 is not provided in the portion where the packing or the like is disposed between the portions, the experiment can be sufficiently performed.
According to this, although the center frequency of the shield changes slightly due to the change in the glass gap size, the required shield performance can be satisfied up to about 30 mm.

In this experiment, as shown in FIG.
A radio wave is transmitted at a constant output from an antenna in a shielded room having a size of 51 cm x a height of 111 cm, and the radio wave is received from an antenna outside the shielded room. The present invention is based on two specimens in an opening. Window glass 1
The received electric field strength when the gap between the window glasses 1 is changed is measured by a spectrum analyzer.

By the way, first, the linear antenna elements 5 are regularly arranged on the window glass 1 in consideration of the electromagnetic field reflection equivalent area or volume, and the linear antenna elements 5 attenuate radio waves. As described above, the optimum distance between the linear antenna elements 5 can be further determined in consideration of the required attenuation.

To secure a high attenuation, it is desirable to arrange the linear antenna elements 5 as close as possible. On the other hand, if the linear antenna elements 5 are arranged closer than necessary to the glass surface of the window glass, there is a visual problem ( Eyesight).

FIG. 14 and FIG. 15 show an experimental apparatus for observing the relationship between the arrangement interval of linear antenna elements and the amount of attenuation. As a result, an experiment was conducted using copper rods as linear antenna elements. Thus, a correlation as shown in FIG. 24 was obtained.

Therefore, the arrangement intervals between the linear antenna elements 5 are determined in consideration of the relationship between the attenuation amounts, and the arrangement intervals between the linear antenna elements are determined as much as possible from the required attenuation amount. By securing a large gap between the linear antenna elements, better visibility can be secured on the glass surface.

In the above experimental results, the material of the linear antenna element 5 was silver paste firing printing and the line width was 0.5 mm.
The linear antenna element 5 has a volume resistivity of 5 × 10 ⁻⁸ (Ω ·
m) It is desirable to set the following.

To secure a high attenuation, it is desirable to minimize the loss resistance of the linear antenna element. For this purpose, it is desirable to reduce the loss resistance by increasing the line width or to adopt a material having good conductivity. However, increasing the line width of the linear antenna element impairs the optical transparency of the glass surface when the linear antenna elements are arranged. According to the present invention, when the linear antenna element has a line width of about 0.5 mm as described above, it is sufficient if the volume resistivity is at least 5 × 10 ⁻⁸ (Ω · m) or less. Performance can be ensured.

As a material of the linear antenna element, copper, silver, and gold are most suitable as materials having low electric resistance, but gold is expensive and copper has an increase in resistance due to oxidation. As described above, by employing silver, the price is not so high, and there is no possibility that the resistance value will increase due to oxidation. Further, by mixing about 5% of glass, the life of the linear antenna element can be made approximately the same as that of glass by integrating with glass.

Since the element is short, the electric field is low and the influence of the dielectric constant on the glass can be reduced.
b (characteristic impedance of two parallel lines) increases, and an effect of reducing the influence of glass can be obtained. Further, when the width is increased, the equivalent radius is increased, and a wide band can be realized with a thin line.

FIG. 10 shows a linear antenna element 5 as a further modified example of the linear antenna element 5 having an open end.
Is made to be the annular line shape 5c. In other words,
It is a composite type in which an annular line-shaped linear antenna element is incorporated in a portion of a linear antenna element having an open end.

In this manner, a large number of thin wires are used in parallel, so that the reflection surface area can be increased, the high-frequency loss resistance value can be reduced without deteriorating the transparency, and the bandwidth and the attenuation can be increased. Is possible.

[0058] By the way, for example, the frequency band on a mobile phone there are two types of 900 MH _Z band and 1,500 MH _Z band. Similarly, PHS has a frequency of 1.9 GHz and wireless LAN
In this case, the frequency is 2.45 GHz. In order to perform electromagnetic shielding on these radio bands, it is necessary to support a plurality of frequency bands.

As an embodiment of such an electromagnetic shielding method having a plurality of frequency bands, linear antenna elements having different lengths are combined and arranged regularly. Figure
As shown in FIG. 12, it is also possible to combine linear antenna elements 5 having open ends with different lengths.

Although the above embodiment has been described with reference to a window glass used for a window of a building, it is also applicable to a window glass of a vehicle such as an automobile or a train, or a window glass of furniture such as a partition or a box.

[0061]

As described above, the window glass of the present invention is
Only radio waves of a frequency band corresponding to the antenna element length are shielded, and other radio waves can be transmitted, so that only the radio wave band of a required frequency is selected and electromagnetic shielding is possible.

Further, it is possible to shield up to about 40 dB, and since a reflection area is formed around the antenna element, the shielding performance can be ensured even if there is a certain gap, and the antenna element can be made thinner. Does not impair the performance.

Further, there is no need to treat the gap between the members on which the above-mentioned members are applied and to carry out the energizing treatment with a conductive material for grounding.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of a window glass of the present invention.

FIG. 2 is a front view of a main part of the window glass according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram when a linear antenna element is a short-circuit dipole.

FIG. 4 is a first explanatory view showing the principle of the electromagnetic shielding method in the window glass of the present invention.

FIG. 5 is a second explanatory view showing the principle of the electromagnetic shielding method in the window glass of the present invention.

FIG. 6 is a front view of a window glass on which linear antenna elements are arranged.

FIG. 7 is a graph of an experimental result in which the performance of a window glass of the present invention in which a Y-shaped linear antenna element is arranged was confirmed.

FIG. 8 is an explanatory diagram showing an arrangement when a linear antenna element is formed in a cross shape.

FIG. 9 is an explanatory view showing a modified example of a linear antenna element having an open end.

FIG. 10 is a front view showing a modified example of a linear antenna element having an open end.

11 is a graph showing the electromagnetic shielding effect of the linear antenna element shown in FIG.

FIG. 12 is an explanatory diagram showing an example of combining linear antenna elements having open ends with different lengths.

FIG. 13 is an explanatory diagram of an experimental facility for confirming the shielding performance of a gap between window glasses.

FIG. 14 is a front view of an experimental apparatus for observing the relationship between the arrangement interval of linear antenna elements and the amount of attenuation.

FIG. 15 is a longitudinal sectional side view of an experimental apparatus for observing the relationship between the arrangement interval of linear antenna elements and the amount of attenuation.

FIG. 16 is a graph of an experimental result of a relationship between an arrangement interval of linear antenna elements and an amount of attenuation.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Window glass 2 ... Sash frame 3 ... Linear antenna element 4 ... Linear antenna element 5 ... Linear antenna element 5a ... Center 5b ... Side 5c ... Annular line shape

────────────────────────────────────────────────── ─── Continuing on the front page (72) Yoshimasa Yoshida 1-35-1 Awaza, Nishi-ku, Osaka-shi, Osaka Prefecture Kashima Construction Co., Ltd. Kansai Branch (72) Inventor Kazushi Yamanoue 1-3-3 Awaza, Nishi-ku, Osaka-shi, Osaka 15 Kashima Construction Co., Ltd.Kansai Branch No. 1 Kashima Corporation Co., Ltd. Technical Research Institute (56) References JP-A-63-168093 (JP, A) JP-A-8-330783 (JP, A) JP-A-9-148782 (JP, A) 9-162589 (JP, A) JP 1-170098 (JP, A) JP 2-296398 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05K 9 / 00

Claims (7)

(57) [Claims] A linear antenna element having an open end and having a length that resonates with a radio wave to be shielded is used as an electromagnetic shielding element, and an electromagnetic field reflection equivalent area (scattering aperture area) of the element is used.
Or considering the electromagnetic field reflection equivalent volume (scattering aperture volume),
In addition, place the end of each side close to the center of the adjacent linear antenna element.
In addition , a window glass having electromagnetic shielding performance, which is arranged on a glass surface or between glass plates and scatters and attenuates radio waves with the linear antenna element. 2. The linear antenna element has a length (electric length) of one side extending from the center, which is 1/1 of a radio wave to be shielded.
4. A wavelength of four wavelengths (1/2 wavelength in the case of a single shape).
A window glass having the described electromagnetic shielding performance. 3. The linear antenna element is composed of a plurality of types so that a plurality of frequencies can be shielded, and two or more types of linear antenna elements having different dimensions and shapes are arranged in combination.
Alternatively, the window glass having the electromagnetic shielding performance according to claim 2. 4. The electromagnetic shield according to claim 3, wherein a plurality of linear antenna elements are provided so as to shield a plurality of frequencies, and linear antenna elements having open ends are combined with different lengths. Window glass with performance. 5. The linear antenna elements determine an arrangement interval in consideration of a relationship between attenuations.
A window glass having the electromagnetic shielding performance according to any one of the above. 6. The window glass having electromagnetic shielding performance according to claim 1, wherein the linear antenna element has a volume resistivity of at least 5 × 10 ⁻⁸ (Ω · m) or less. 7. The electromagnetic antenna according to claim 1, wherein the linear antenna element is made of a material having excellent conductivity, durability, and weather resistance, and incorporating a small amount of vitreous material. Having window glass.