JP2007324570A - Electromagnetic wave absorption board to be used for wireless lan and implementation method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transparent electromagnetic wave absorption board with superior heat insulation performance and multiple glass configurations for electromagnetic waves, whose frequency is set to be within a range of 2.45 GHz to 5.2 GHz that is used in a wireless LAN. <P>SOLUTION: In this electromagnetic wave absorption board to be used for a wireless LAN, as for a multiple glass, configured by arranging a pair of transparent glass sheets at an interval by having a spacer at the circumferencial end portion, and forming a hollow layer sealed between the glass sheets, the thickness of the glass sheet is in the range of 2 to 20 mm, and the thickness of the hollow layer is within the range of 5 to 15 mm, and a resistive film within the range of 20-2 kΩ/SQUARE is formed at least on one glass sheet of the pair of glass sheets, and the resistive film is formed on the glass sheet surface on the hollow layer side. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electromagnetic wave absorbing plate for use in a transparent wireless LAN mainly used for an opening of an outer wall of a building or an indoor partition.

  In recent years, various information transmission has become possible with the rapid progress of information transmission technology. In particular, information transmission by radio is very excellent and actively used from the viewpoint of convenience.

  Examples of wireless information transmission means include cellular phones, PDAs (personal digital assistants), wireless LANs, broadcast waves, automobile radars, ETC in-vehicle devices, and various electronic devices.

  On the other hand, with the spread of these wireless information transmissions, electromagnetic waves emitted from devices used for wireless information transmission enter the building through the opening of the building and become electromagnetic noise of other electronic devices. There is a demand for an electromagnetic wave absorbing plate having transparency that can effectively absorb water.

  Among wireless information transmission, wireless LAN (in-house information communication network) does not require indoor LAN construction (code wiring work, etc.), so it greatly contributes to cost reduction and ease of use in offices and general homes. is doing.

  However, in the wireless LAN, indoors, the speed of the LAN decreases due to the influence of reflecting materials (desks, lockers, chairs, etc.), wiretapping due to leakage of radio waves to the outside, and radio interference between buildings and buildings (2.45 GHz band has 4 channels). Many problems occur, such as bad effects due to the above), unauthorized access from the outside, and spoofing.

  As countermeasures against such problems, exchange of issuer certificates between a communication terminal such as a PC (personal computer) and a server, data encryption or automatic automatic change of encryption key, ID or password Measures are taken by issuing.

  However, exchange of issuer certificates is not compatible between models and is difficult between different models. Further, measures such as data encryption, automatic automatic change of the encryption key, ID and password are accompanied by a risk of being decrypted by a third party.

  For this reason, it is necessary to arrange a transparent electromagnetic wave absorbing plate in an indoor partition or an opening of a building or building so that information does not leak outside.

  In recent years, from the viewpoint of energy saving, a multilayer glass excellent in heat insulation is often used for the opening. As an electromagnetic wave absorbing plate having such a multilayer glass structure, Patent Document 1 discloses an incoming electromagnetic wave. There is disclosed a λ / 4 type electromagnetic wave absorber in which an absorbing material to be absorbed and a reflecting material to reflect an incoming electromagnetic wave are arranged at an interval corresponding to ¼ of the wavelength of the electromagnetic wave to be absorbed.

  When the λ / 4 type electromagnetic wave absorber is used, the thickness of the absorber needs to be a quarter of the wavelength. Therefore, when the use center frequency of the wireless LAN is 2.45 GHz, the thickness is about 31 mm. Thickness is required. Therefore, there is a disadvantage that the thickness is too thick to attach this absorber to a partition, a window of a building, a wall, or the like.

  Further, in Patent Document 2, in order to reduce the thickness of the λ / 4 type electromagnetic wave absorber, it is formed in a stripe shape or a lattice shape between the absorber and the reflective material of the λ / 4 type electromagnetic wave absorber. There is also a proposal that realizes that the conductive film is provided to increase the effective dielectric constant between the absorber and the reflector, and to reduce the thickness thereof.

  In the electromagnetic wave absorber disclosed in Patent Document 2, a conductive film coated in a stripe shape or a lattice shape is disposed between the absorber and the reflector of the λ / 4 type electromagnetic wave absorber, thereby reducing the plate thickness. Although it can be reduced, the structure itself is complicated and the production becomes complicated.

  Patent Document 3 proposes an electromagnetic absorption layer provided outside the room on which electromagnetic waves are incident, an electromagnetic reflection layer provided on the indoor side, and a liquid containing a high dielectric constant instead of a hollow layer. .

In the radio wave absorbing glass disclosed in Patent Document 3, it is necessary to connect the electromagnetic reflection layer to the frame body. Furthermore, if a liquid having a high dielectric constant is used instead of the hollow layer, the heat insulating performance is inferior. End up.
JP 2001-44750 A Japanese Patent Laid-Open No. 10-275997 JP-A-5-37178

  The present invention has been made in view of the circumstances as described in Patent Documents 1 to 3, and is insulative with respect to electromagnetic waves having frequencies of 2.45 GHz and 5.2 GHz, which are used in a wireless LAN. A transparent electromagnetic wave absorbing plate having an excellent multilayer glass structure is provided.

  (A) The electromagnetic wave absorbing plate of the present invention is formed by separating a pair of transparent plate glasses via a spacer disposed at a peripheral edge, and forming a sealed hollow layer between the pair of plate glasses. In the multi-layer glass, the thickness of the plate glass is in the range of 2 to 20 mm, the thickness of the hollow layer is in the range of 5 to 15 mm, and one of the pair of plate glasses has a resistance in the range of 20 to 2 KΩ / □. A film is formed, and the resistive film is an electromagnetic wave absorbing plate used for a wireless LAN, which is formed on a surface of a plate glass on a hollow layer side.

  The electromagnetic wave absorbing plate used in the wireless LAN of the present invention is the electromagnetic wave absorbing plate used in the wireless LAN described in (A). (1) The thickness of the plate glass on which the resistance film is formed is 2 mm or more and less than 8 mm, The thickness is in the range of 5 mm to 15 mm, the resistance value of the resistance film is in the range of 20 to 2 kΩ / □, or (2) the thickness of the plate glass on which the resistance film is formed is 8 mm or more and less than 15 mm, and the hollow layer 7 Is in the range of 5 mm to 8 mm, and the resistance value of the resistance film is in the range of 20 to 2 kΩ / □, or (3) the thickness of the plate glass on which the resistance film is formed is 8 mm to 20 mm, and the hollow layer 7 having a thickness of 8 mm or more and 15 mm or less, a resistance value of the resistance film in a range of 20 to 600 Ω / □, and an electromagnetic wave absorption amount of 2.45 GHz is 10 dB or more. An electromagnetic wave absorbing plate used in a wireless LAN to symptoms.

  The electromagnetic wave absorbing plate used for the wireless LAN of the present invention is the electromagnetic wave absorbing plate used for the wireless LAN described in (A). (4) A plate glass in which the hollow layer 7 is in the range of 5 to 15 mm and a resistance film is formed. The resistance value of the resistive film is in the range of 100 to 2 KΩ / □, or (5) the thickness of the hollow layer 7 is in the range of 5 to 15 mm, and the resistance is The thickness of the sheet glass on which the film is formed is in the range of 2 mm to 8 mm, and the resistance value of the resistance film is in the range of 20 to 2 KΩ / □, or (6) the hollow layer 7 is in the range of 5 mm to 15 mm The thickness range of the plate glass on which the resistance film is formed is in the range of 15 mm or more and 20 mm or less, the resistance value of the resistance film is in the range of 20 to 600 Ω / □, and the electromagnetic wave absorption amount of 5.2 GHz is 10dB or more An electromagnetic wave absorbing plate used in a wireless LAN, characterized in that.

  The electromagnetic wave absorbing plate used in the wireless LAN of the present invention is characterized in that in the electromagnetic wave absorbing plate used in the wireless LAN, a resistive film is formed on a plate glass in the order of a dielectric film, a metal film, and a dielectric film. An electromagnetic wave absorbing plate.

  The electromagnetic wave absorbing plate used for the wireless LAN of the present invention is a radio wave absorbing plate used for the wireless LAN, wherein the metal film is made of Cr or Al in the electromagnetic wave absorbing plate used for the wireless LAN.

  Further, the electromagnetic wave absorbing plate construction method used for the wireless LAN of the present invention is a resistive film for preventing electromagnetic waves of the wireless LAN generated indoors from leaking outside in the electromagnetic wave absorbing plate used for the wireless LAN. This is a method for constructing an electromagnetic absorption plate used in a wireless LAN, characterized in that the plate glass on which the slab is formed is arranged on the indoor side.

The electromagnetic wave absorbing plate having a multilayer glass structure of the present invention has a simple multilayer glass structure and functions effectively in a frequency range of 1 to 10 GHz, particularly a transparent electromagnetic wave absorbing plate, particularly, wireless LAN frequencies 2.45 GHz and 5. An electromagnetic wave absorbing plate effective for 2 GHz is provided.

  Regarding the electromagnetic wave absorption performance, for example, the wireless LAN frequency band is a frequency band centered around 2.45 GHz and 5.2 GHz band, and the former is particularly frequently used because it can transmit from indoors to outdoors. The latter is only for indoor use due to radio wave regulations. Also, when performing wireless LAN, an “access point” is provided to amplify the output. Furthermore, electromagnetic interference with other parts is prevented. Since the output of “access point” at this time is 22 mw (0.022 w), it is necessary to correspond to this output. Even if this output is smaller than that of a general communication device (such as a mobile phone), it can be used as an electromagnetic wave absorber if the electromagnetic wave absorption performance is set to -10 dB or more (electromagnetic energy is attenuated to 1/10). it can.

  In addition, when a PHS phone or personal computer (PC) is used in a building for a wireless LAN in a building, and the purpose is to prevent malfunction of the PC or server or wiretapping for the wireless communication, electromagnetic wave absorption is required. The frequency range is 1-10 GHz.

  The frequency at which the electromagnetic wave absorbing plate of the present invention is effective is approximately 1 to 10 GHz, and this frequency range includes PDA (information for 800 MHz to 1 GHz, 1.5 GHz band for mobile phones and 1.9 GHz band for PHS phones. 2.45 GHz band of portable terminal), 2.45 GHz band and 5.2 GHz band used for wireless LAN of PC, and ETC on-board equipment 5.8 GHz band.

  In particular, the electromagnetic wave absorbing plate of the present invention effectively acts on electromagnetic waves in the 2.45 GHz band and the 5.2 GHz band used in wireless LAN, and is used for an opening of an outer wall of a building. It is desirable to use for preventing propagation of electromagnetic waves to the outside of the building, or preventing crosstalk due to electromagnetic waves entering from the outside of the building.

  As shown in FIG. 1, the electromagnetic wave absorbing plate according to the present invention is arranged so that transparent dielectric plates 1 and 2 face each other at a substantially constant interval by using a spacer 3 at the periphery of the dielectric plate. In addition, the structure of the double-glazed glass. The dielectric plates 1 and 2 and the spacer 3 are bonded by the adhesive 3, and the space near the edge of the dielectric plate formed by the spacer 4 and the dielectric plates 1 and 2 is sealed by the sealing material 4. It is preferable. It is preferable to use a butyl rubber adhesive for the adhesive 3 and a silicone resin, a hot melt resin, or the like for the sealing material 4.

  When the dielectric plates 1 and 2 are opposed to each other, the spacers 3 may not be used, and the dielectric plates 1 and 2 may be opposed to each other only by an elastic sealing material.

  The hollow layer 7 formed by the dielectric plates 1 and 2 is preferably filled with air, but may be filled with a rare gas such as argon gas.

  The surface of the dielectric plate 1 facing the hollow layer 7 is formed with a transparent resistive film 6 formed thereon.

  As the dielectric plates 1 and 2, glass plates such as soda-lime glass, aluminosilicate glass, and borosilicate glass, and various transparent plastic plates such as a polycarbonate plate and an acrylic plate can be used.

  The thicknesses of the dielectric plates 1 and 2 are important for developing the ability to absorb electromagnetic waves. For this reason, as shown in FIG. 2 and FIG. It is desirable to laminate the body plates 20 and 22 to adjust the thickness of the dielectric plate and to optimize the performance of absorbing electromagnetic waves.

  The dielectric plates can be laminated using, for example, an intermediate film such as polyvinyl butyral or EVA.

  The dielectric to be laminated is one or more kinds of dielectric plates from the glass plates such as soda-lime glass, aluminosilicate glass, borosilicate glass, etc., and various transparent plastic plates such as polycarbonate plate and acrylic plate. For example, a glass plate and a glass plate, a plate glass and a plastic plate, or a plastic plate is laminated.

The resistive film 6 formed on the surface of the dielectric plate 1 is a transparent metal film made of one or more kinds of metals selected from Ag, Au, Cr, Ti, Al, Cu, SUS, Ni, etc. A multilayer thin film in which a metal film and a metal oxide film such as ZnO, SnO ₂ , In ₂ O ₃ , TiO ₂ , Bi ₂ O ₃ , Ta ₂ O ₃ , WO ₃ , or ZnS are stacked can be used.

As the multilayer film, for example, three layers of ZnO film / Ag film / ZnO film, TiO ₂ film / Cr film / SnO ₂ film, ZnO film / Al film / ZnO film, SnO ₂ film / TiCr film / SnO ₂ film, etc. Laminated, ZnO film / Ag film / ZnO film / Ag film / ZnO film, ZnO film / Al film / ZnO film / Al film / ZnO film, SnO ₂ film / Al film / SnO ₂ film / Al film / SnO ₂ A laminate of five layers such as a film, or an ITO film or a Nesa film can be appropriately selected and used.

  The means for forming the resistance film 6 described above is not particularly specified, but a physical vapor deposition method (sputtering method, vacuum vapor deposition method, etc.) or a chemical vapor deposition method can be selected and used.

  Further, a transparent resin film on which a resistance film is formed may be bonded to the dielectric plate. As the resistance film at this time, the same film as the resistance film formed on a transparent resin plate such as a glass plate can be used. As the transparent resin film, a polyethylene terephthalate (PET) film, a polyester film, or the like can be used.

  The electromagnetic wave absorbing performance of the electromagnetic wave absorbing plate of the present invention is, as shown in FIG. 4, when electromagnetic waves are incident from the transparent dielectric plate 1 side on which the resistance film 6 is formed, and as shown in FIG. There are cases where electromagnetic waves are incident from the transparent dielectric plate 2 side on which the resistive coating 6 is not formed, and equivalent circuits for obtaining the amount of absorption of electromagnetic waves are as shown in FIGS. 5 and 7, respectively. Different.

  Hereinafter, the case where electromagnetic waves are incident from the side of the transparent dielectric plate 1 on which the resistance film 6 is formed as shown in FIG. 4 is referred to as case 1, and the transparent film on which the resistance film 6 is not formed as shown in FIG. A case where electromagnetic waves are incident from the side of the dielectric plate 2 is referred to as case 2.

  In case 1, the amount of electromagnetic wave absorption is determined as follows. The equivalent circuit in case 1 is as shown in FIG. In FIG. 5, the input impedance Zg1 of the dielectric plate 2 on the transmission side free space side opposite to the side on which the electromagnetic wave is incident is obtained by the following equation (1).

Here, ε ₂ is the complex dielectric constant of the transparent dielectric plate 2, and μ 2 is the relative permeability of the transparent dielectric plate 2. Further, γ ₂ is obtained by the equation (2), j = −1 ^1/2 , λ _i is the wavelength of the electromagnetic wave, and d _g2 is the thickness (m) of the transparent dielectric plate 2. is there.

The input impedance Z _ai to the hollow layer 7 is obtained by the equation (3).

Here _{d a} is the thickness of the hollow layer 7 (m).

The impedance Z _ri on the hollow layer 7 side of the resistance coating formed on the transparent dielectric plate 1 is obtained by the following equation (4) from the equivalent circuit diagram shown in FIG.

Here, _Zr is the sheet resistance (Ω / □) of the resistive coating 6, and 377 is the characteristic impedance of air.

The input impedance Z _xi of the electromagnetic wave on the transparent dielectric plate 1 side (electromagnetic wave incident side) in FIG. 4 is obtained by the following equation (5) from the equivalent circuit shown in FIG.

Here, ε ₁ is the complex dielectric constant of the transparent dielectric plate 1, and μ ₁ is the relative permeability of the transparent dielectric plate. In the case of plate glass, ε ₁ = 7−0.1j (j = (− 1) ^1/2 ) and μ ₁ = 1. λ _i is the wavelength of the electromagnetic wave, and d _g1 is the thickness (m) of the transparent plate.

Furthermore, the reflection coefficient Γ _{i of the} electromagnetic wave reflected from the surface of the transparent dielectric is a value obtained by the following equation (6):

From the reflection coefficient Γ _i1 , the electromagnetic wave absorption amount A _i1 can be obtained by the following equation (7).

Next, the amount of electromagnetic waves absorbed in case 2 is determined using the equivalent circuit shown in FIG. In FIG. 7, the input impedance Z _gi1 of the dielectric plate 2 on the free space side opposite to the side on which the electromagnetic wave is incident can be obtained by the following equation (8).

Here, γ ₁ is obtained by the following equation (9).

  The input impedance of the resistance film 3 formed on the transparent dielectric plate 1 is obtained by the following equation (10).

  Further, the input impedance Zai2 on the surface of the hollow layer 7 is obtained by the following equation (11).

  A resistance film having a surface resistance value Zr2 is assumed on the surface of the transparent derivative on the electromagnetic wave incident side shown in FIG. 6, and the impedance of the resistance film is obtained from the equivalent circuit of FIG.

  Furthermore, the impedance of the electromagnetic wave incident on the transparent dielectric 2 on the electromagnetic wave incident side is obtained by the following equation (13).

Here, ε ₂ is the complex dielectric constant of the transparent plate-like body, and μ ₂ is the relative permeability of the transparent plate-like body. In the case of plate glass, ε ₂ = 7−0.1j (j = (− 1) ^1/2 ) and μ ₂ = 1. λ _i is the wavelength of the electromagnetic wave, and d _g2 is the thickness (m) of the transparent dielectric plate.

The reflection coefficient Γ _{i2 of the} electromagnetic wave reflected by the transparent dielectric plate is a value obtained by the following equation (14):

From the reflection coefficient Γ _i2 , the electromagnetic wave absorption amount A _i2 when the electromagnetic wave is incident from the transparent dielectric plate side on which the resistance film is not formed can be obtained by the following equation (15).

  The amount of electromagnetic wave absorption when the glass plates are used for the transparent dielectric plates 1 and 2 shown in FIG. 1, for example, a resistance film is formed on a plate glass having a thickness of 6 mm, and the thickness of the hollow layer 7 is 6 mm, and further a resistance film is formed. When the thickness of the plate glass disposed opposite to the glass is 6 mm, the absorption amount of the electromagnetic wave in the case 1 is obtained by the equation (7), and the absorption amount with respect to the wavelength of the electromagnetic wave is obtained as shown in FIG. Is obtained.

The thickness of the sheet glass on which the resistance film is formed is 6 types of 3 mm, 5 mm, 8 mm, 10 mm, 12 mm, and 15 mm. For each of the sheet glass on which the resistance film is formed, a graph as shown in FIG. 5 mm, 8 mm, 10 mm, 12 mm and 15 mm were prepared, and when the resistance range of the resistive film having an absorption amount of 2.45 GHz and 5.2 GHz for electromagnetic waves of 10 dB or more was obtained, the results shown in Table 1 for case 1 were obtained. The results shown in Table 2 were obtained for Case 2.

  Table 1 is created based on the amount of absorption determined by equation (7), and Table 2 is prepared based on the amount of absorption determined by equation (15).

  In the preparation of Table 1 and Table 2, if the resistance value of the resistance film exceeds 2 KΩ / □, the absorption amount obtained by the equations (7) and (15) differs from the measurement value of the absorption amount described in the examples. The upper limit value of the resistance film was 2 KΩ / □.

  Comparing Table 1 and Table 2, it can be seen that the thickness range of the plate glass and the hollow layer 7 are wider in the thickness range of the case 1 than in the case 2 and the absorption amount is 10 dB or more.

  From Table 1 and Table 2, the thickness of the plate glass on which the resistance film is formed is in the range of 2 to 20 mm, the thickness of the hollow layer is in the range of 5 to 15 mm, and one of the pair of plate glasses has 20 It can be seen that the film formed with the resistance film in the range of ˜2 kΩ / □ has the ability to absorb 10 dB or more of the electromagnetic wave used in the wireless LAN.

  In particular, from Tables 1 and 2, with respect to electromagnetic waves of 2.45 GHz, (1) when the thickness of the plate glass on which the resistance film is formed is 2 mm or more and less than 8 mm, and the thickness of the hollow layer 7 is 5 mm to 15 mm, (2) When the thickness of the plate glass on which the resistance film is formed is 8 mm or more and less than 15 mm and the thickness of the hollow layer 7 is 5 mm or more and less than 8 mm, the resistance range of the resistance film is in the range of 20 to 2 kΩ / □, And in case 2 or in either case 1 or case 2, there is an electromagnetic wave absorption amount of 10 dB or more, which is preferable.

  Further, from Table 1, (3) the thickness of the plate glass on which the resistance film is formed is 8 mm or more and 20 mm or less, the thickness of the hollow layer 7 is 8 mm or more and 15 mm or less, and the surface resistance value of the resistance film is 20 to 600Ω / □. Accordingly, there are some which have an absorption amount of 2.45 GHz electromagnetic wave of 10 dB or more, which is preferable.

  Next, for electromagnetic waves of 5.2 GHz, from Tables 1 and 2, (4) the hollow layer 7 is in the range of 5 to 15 mm, and the thickness of the plate glass on which the resistive film is formed is more than 8 mm and less than 15 mm. Those having a resistance film of 100 to 2 KΩ / □ in the range have an electromagnetic wave absorption amount of 10 dB or more for both cases 1 and 2 or cases 1 and 2. Some are preferred.

  (5) The thickness of the hollow layer 7 is in the range of 5 mm to 15 mm, the thickness of the plate glass on which the resistance film is formed is in the range of 2 mm to 8 mm, and the resistance of the surface resistance value is in the range of 20 to 2 KΩ / □. Some of which a film is formed absorbs an electromagnetic wave of 5.2 GHz by 10 dB or more, which is preferable.

  (6) The hollow layer 7 is in the range of 5 mm to 15 mm, the thickness range of the plate glass on which the resistance film is formed is in the range of 15 mm to 20 mm, and the resistance film of 20 to 600Ω / □ is formed. Some absorb 5.2 GHz electromagnetic waves of 10 dB or more, which is preferable.

  Furthermore, in the case where the absorption amount is 20 dB or more (attenuated to 1/100) with respect to the thickness of the plate glass on which the anti-film is formed and the thickness of the hollow layer, Table 2. The resistance film has a surface resistance value range as shown in Table 4 for 5.2 GHz.

    Samples having different thicknesses of plate glass, hollow layer 7 and surface resistance of the resistance film shown in Table 5 using the glass plate float manufactured on dielectrics 1 and 2 as the electromagnetic absorption plate having the configuration shown in FIG. 1-4 were produced. The hollow layer 7 was filled with air. As the spacer, an aluminum spacer having a substantially square cross section was used, and the space between the hollow layers was changed depending on the size of the spacer.

  Samples 1 to 4 are electromagnetic wave absorbing plates prepared for use in the wireless LAN 2.45 GHz frequency band in case 1.

As the resistance film, a TiO ₂ film, a Cr film, and a SnO ₂ film were formed in this order by a sputtering method, and the area resistance of the resistance film was adjusted by the film thickness.

  The electromagnetic wave absorbing performance of the produced electromagnetic wave absorbing plates (samples 1 to 4) was measured by an arch type measuring apparatus using a time domain method shown in FIG.

  The measurement is performed by transmitting an electromagnetic wave from a transmission antenna 32 installed in an arched frame 33 using a network analyzer 30 and receiving the reflection amount of the electromagnetic wave reflected by the electromagnetic wave absorbing plate (samples 1 to 4) 36. Measurement is performed by a network analyzer using the antenna 32 '. A horn antenna was used for both the transmitting antenna 32 and the receiving antenna 32 '.

  For the electromagnetic wave absorption plate (samples 1 to 4) 36, the reflection amount of the metal plate made of aluminum is measured, and then the reflection amount of the electromagnetic wave absorption plate (samples 1 to 4) 36 is measured. The difference from the reflection amount of the electromagnetic wave absorbing plates (samples 1 to 4) 36 was calculated as the electromagnetic wave absorption amount of the samples 1 to 4.

  The reflection amount of the electromagnetic wave absorbing plate (samples 1 to 4) 36 is measured by placing the samples 1 to 4 on a sample base 35 made of an electromagnetic wave absorbing polyurethane foam and kneading and molding carbon. The measurement was performed by surrounding the body 34 with a body 34.

  Table 5 shows the measured electromagnetic wave absorption. Table 5 also shows the amount of electromagnetic wave absorption obtained by calculation. As shown in Table 5, the amount of electromagnetic wave absorption obtained by calculation and the measured amount of electromagnetic wave absorption agreed well.

  In the measurement, the TE wave (when the electric field is perpendicular to the incident surface) and the TM wave (when the magnetic field is perpendicular to the incident surface) were measured, but there was no significant difference.

  In addition to the normal incidence, measurements were also made in the case of oblique incidence with an inclination of 45 degrees from the vertical, but there was no significant difference compared to the measurement result of normal incidence.

  A box using the electromagnetic wave absorbing plates of Samples 1 to 4 was prepared, and a notebook computer was installed in the box. The box was made with the resistive coating surface on the inside.

  I tried to connect a wireless LAN in a frequency band of 2.45 GHz from a laptop computer installed in the box to a server installed outside the box, but I could not connect, and electromagnetic waves from the server were transmitted through the box. Not confirmed. Therefore, it was confirmed that the electromagnetic wave absorbing plates of Samples 1 to 4 have a practical level of electromagnetic wave absorbing performance.

  In the same manner as in Example 1, electromagnetic wave absorbing plates (samples 5 to 8) as shown in Table 6 were prepared for use in the 5.2 GHz frequency band of the wireless LAN in case 1. Further, the amount of electromagnetic waves absorbed was measured in the same manner as in Example 1.

  Table 6 shows the amount of electromagnetic wave absorption obtained by calculation and the amount of electromagnetic wave absorption measured, and both values agreed well.

The wireless LAN 2 in the case 2 is the same as in the first embodiment except that the resistance film is a ZnO ₂ film, an Al film, and a ZnO ₂ film formed in this order by sputtering. For use in the .45 GHz frequency band, electromagnetic wave absorbing plates (samples 9 to 11) as shown in Table 6 were prepared.

  In the same manner as in Example 1, the amount of electromagnetic waves absorbed was measured. Table 7 shows the amount of electromagnetic wave absorption obtained by calculation and the amount of electromagnetic wave absorption measured, and both values agreed well.

The wireless LAN 2 in the case 2 is the same as in the first embodiment except that the resistance film is a ZnO ₂ film, an Al film, and a ZnO ₂ film formed in this order by sputtering. For use in the .45 GHz frequency band, electromagnetic wave absorbing plates (samples 12 to 14) as shown in Table 6 were prepared.

  In the same manner as in Example 1, the amount of electromagnetic waves absorbed was measured. Table 8 shows the amount of electromagnetic wave absorption obtained by calculation and the amount of electromagnetic wave absorption measured, and both values agreed well.

It is sectional drawing of the electromagnetic wave absorption board by this invention. 1 is a cross-sectional view of an electromagnetic wave absorbing plate according to the present invention in which a dielectric plate formed with a resistance film is formed by laminating two dielectric plates with an intermediate film. It is sectional drawing of the electromagnetic wave absorption board of this invention formed by laminating | stacking two dielectric plates with an intermediate film, the dielectric plate in which the resistance film is not formed. It is a conceptual diagram which creates the equivalent circuit diagram for calculating an impedance when an electromagnetic wave arrives at the dielectric material board in which a resistive film is formed. FIG. 5 is an equivalent circuit diagram for calculating impedance when the radio wave arrival direction is shown in FIG. 4. It is a conceptual diagram which creates the equivalent circuit diagram for calculating an impedance when an electromagnetic wave arrives at the dielectric material board in which the resistance film is not formed. FIG. 7 is an equivalent circuit diagram for calculating impedance when the radio wave arrival direction is shown in FIG. 6. It is a graph which shows the relationship between the surface resistance value of a resistive film and the amount of electromagnetic waves absorbed when the thickness of plate glass is 6 mm and the thickness of the hollow layer 7 is 6 mm. The figure which shows the measuring apparatus of electromagnetic wave absorption performance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Transparent dielectric plate 3 Adhesive material 4 Spacer 5 Sealing material 6 Resistive film 7 Hollow layer 10, 12 Transparent dielectric plate 11 Intermediate film 20, 22 Transparent dielectric plate 21 Intermediate film 30 Network analyzer 31 Electric wire 32 Transmission / reception antenna 32 'Transmission / reception antenna 33 Arch frame 34 Electromagnetic wave absorber 35 Sample stage 36 Electromagnetic wave absorption plate

Claims (6)

  In a multi-layer glass in which a pair of transparent plate glasses are spaced apart via a spacer disposed at a peripheral edge, and a sealed hollow layer is formed between the pair of plate glasses, the thickness of the plate glass is 2 to 2 The thickness of the hollow layer is in the range of 5 to 15 mm, and a resistance film in the range of 20 to 2 KΩ / □ is formed on either one of the pair of glass sheets. An electromagnetic wave absorbing plate used for a wireless LAN, characterized by being formed on a surface on a hollow layer side.   (1) The thickness of the plate glass on which the resistance film is formed is 2 mm or more and less than 8 mm, the thickness of the hollow layer is in the range of 5 mm to 15 mm, and the resistance value of the resistance film is in the range of 20 to 2 kΩ / □, or ( 2) The thickness of the plate glass on which the resistance film is formed is 8 mm or more and less than 15 mm, the thickness of the hollow layer is in the range of 5 mm or more and 8 mm, and the resistance value of the resistance film is in the range of 20 to 2 kΩ / □, or ( 3) The thickness of the plate glass on which the resistance film is formed is 8 mm or more and 20 mm or less, the thickness of the hollow layer is 8 mm or more and 15 mm or less, the resistance value of the resistance film is in the range of 20 to 600Ω / □, and 2.45 GHz. 2. The electromagnetic wave absorbing plate used for a wireless LAN according to claim 1, wherein the electromagnetic wave absorption amount is 10 dB or more.   (4) The hollow layer is in the range of 5 to 15 mm, the thickness of the plate glass on which the resistance film is formed is in the range of more than 8 mm and less than 15 mm, and the resistance value of the resistance film is in the range of 100 to 2 KΩ / □. Or (5) The thickness of the hollow layer is in the range of 5 mm to 15 mm, the thickness of the plate glass on which the resistance film is formed is in the range of 2 mm to 8 mm, and the resistance value of the resistance film is in the range of 20 to 2 KΩ / □. Or (6) the hollow layer is in the range of 5 mm to 15 mm, the thickness range of the plate glass on which the resistance film is formed is in the range of 15 mm to 20 mm, and the resistance value of the resistance film is 20 to 600Ω / □ 2. The electromagnetic wave absorbing plate for use in a wireless LAN according to claim 1, wherein the electromagnetic wave absorbing amount of 5.2 GHz is 10 dB or more.   4. The electromagnetic wave absorbing plate for use in a wireless LAN according to claim 1, wherein the resistance film is formed on a plate glass in the order of a dielectric film, a metal film, and a dielectric film.   5. The radio wave absorber for use in a wireless LAN according to claim 1, wherein the metal film is made of Cr or Al.   6. The glass sheet according to claim 1, wherein a sheet glass having a resistance film is arranged on the indoor side in order to absorb the electromagnetic wave of the wireless LAN generated in the room and prevent it from coming out of the room. Method for constructing electromagnetic absorbing plate for use in wireless LAN