JP4073933B2 - Electromagnetic wave absorber - Google Patents

Description

  The present invention relates to an electromagnetic wave absorber that captures and absorbs electromagnetic waves.

In the construction of a local area network (LAN) of a computer network, a wireless LAN using microwaves is used, and a more flexible and highly mobile communication system is constructed. In addition, a communication service for wireless communication between a wide area network or switching network called FWA (Fixed Wireless Access) and a communication device operated by a user has started, and the wireless communication system is being used more closely. In addition, WPAN (Wireless Personal
A short-range wireless technology called Bluetooth, which is a representative of the Area Network, is used as an alternative technology to the wired cable technology. In the future, VoWLAN (Voice over Wireless Local
The spread of a communication system using a cellular phone device capable of voice communication by wireless LAN called “Area Network” is also expected.

  When building a plurality of wireless LAN systems in close proximity, or using an anti-theft device that uses a microwave oven and wireless communication technology in an environment where the wireless LAN system is built, the result of using electromagnetic waves in the same band, There may be a problem of electromagnetic interference (interference with other waves). Apart from that, there may be a problem of transmission errors due to reflected waves (multipath problem, self-interference). Specifically, the transmission speed between devices using the above wireless technology decreases, the BER (Bit Error Rate) increases, that is, the communication environment deteriorates. There is a concern about the influence on the electronic device, and in the worst case, the device may malfunction. In order to solve these problems, an electromagnetic wave absorber (hereinafter sometimes referred to as “pattern electromagnetic wave absorber”) having a pattern layer having a conductive pattern (hereinafter sometimes simply referred to as “pattern”) is used. .

  The pattern electromagnetic wave absorber is disclosed by patent documents 1-4, for example. In particular, Patent Document 4 discloses an electromagnetic wave absorber having a pattern layer having excellent oblique incidence characteristics. Further, Patent Document 3 describes a plurality of resonance type frequency selective electromagnetic wave shielding planar bodies, which relates to an electromagnetic wave absorber having a pattern layer having a bimodal characteristic. The shape of the pattern used in the electromagnetic wave absorber disclosed in these Patent Documents 1 to 4 is a polygon or a circle, and is a linear or planar shape. Regarding the pattern shape, no literature was found that considered the influence of the polarization of electromagnetic waves on the electromagnetic wave absorption characteristics.

Japanese Patent No. 3076473 (Japanese Patent Laid-Open No. 6-244583) Japanese Patent No. 3209456 (JP-A-6-140787) JP-A-11-204984 JP 2002-246786 A

  Pattern electromagnetic wave absorbers function as a receiving antenna corresponding to the electromagnetic wave of the frequency that should absorb the pattern, capture the electromagnetic wave, and cause the captured electromagnetic wave to interfere with each other so that the electromagnetic wave is attenuated or canceled by the pattern and the loss layer. Reduce the reflected wave. As described above, the patterned electromagnetic wave absorber realizes a thin electromagnetic wave absorber that is matched so as to resonate with respect to the electromagnetic wave having the frequency to be absorbed.

  The pattern electromagnetic wave absorber is designed so that the reflection amount of the electromagnetic wave of the frequency to be absorbed becomes small by appropriately setting the dimension of the pattern. However, when the polarization dependence of the pattern is large, the electromagnetic wave of the frequency to be absorbed It becomes difficult to correspond to. In other words, due to the shape of the pattern, the electromagnetic wave absorption characteristic, especially the absorption frequency fluctuates due to the TE wave, TM wave, electromagnetic wave entering from any angle between them, or circular polarization, and therefore the electromagnetic wave absorption characteristic is polarization dependent. There was a problem of having sex.

  This is due to the fact that the pattern electromagnetic wave absorber involves parameters including the pattern shape, number, arrangement, loss layer dimensions and material constants (ε ′, ε ″, μ ′, μ ″) to create an optimal state, Since it has realized a high-performance thin electromagnetic wave absorber, it has been designed to optimize the absorption characteristics for vertically incident electromagnetic waves, but the resonance state is easily affected by the incident angle and polarization of electromagnetic waves, and the resonance frequency It is because it is easy to fluctuate.

  An object of the present invention is to provide an electromagnetic wave absorber having a high peak value of electromagnetic wave absorption, or capable of absorbing electromagnetic waves of a plurality of frequencies, and having a small frequency shift in which the absorption amount reaches a peak depending on the polarization direction of the electromagnetic wave. Is to provide.

The present invention relates to a pattern formed in such a manner that a plurality of conductive patterns including one or a plurality of types of conductive patterns having a substantially polygonal outer shape in which at least one corner is curved are not connected to each other. Layers,
A loss layer having a portion made of a material that is at least one of a magnetic loss material having a complex relative permeability (μ ′, μ ″) and a dielectric loss material having a complex relative permittivity (ε ′, ε ″);
Constructed by laminating a conductive reflective layer located on the opposite side of the pattern layer with respect to the loss layer,
The dielectric loss material is formed by adding a material selected from the group of graphite, carbon black, carbon fiber, graphite fiber, metal powder, metal fiber to an organic polymer,
The pattern layer is provided so as to be close to the loss layer, and a ratio R / L between a substantially polygonal side length L and a curvature radius R of the curved corner is 0.1 to 0.46 . In addition, the electromagnetic wave absorber is formed so that R is 2 to 11.5 mm .

According to the present invention, an electromagnetic wave absorber having excellent electromagnetic wave absorption characteristics can be realized. In the electromagnetic wave absorber, first, an electromagnetic wave having a specific frequency is received by the conductive pattern of the pattern layer according to the resonance principle of the antenna. Here, the specific frequency is a frequency determined by specifications such as the shape and dimensions of the conductive pattern, and is a frequency to be absorbed by the electromagnetic wave absorber. Since the loss layer is provided by being laminated so as to be close to the pattern layer having the conductive pattern for receiving the electromagnetic wave, the energy of the received electromagnetic wave can be lost by the loss layer. In this way, electromagnetic waves can be absorbed.
The loss layer has a portion made of a material that is at least one of a magnetic loss material having a complex relative permeability (μ ′, μ ″) and a dielectric loss material having a complex relative permittivity (ε ′, ε ″). The dielectric loss material is formed by adding a material selected from the group consisting of graphite, carbon black, carbon fiber, graphite fiber, metal powder, and metal fiber to the organic polymer.

Further, the conductive pattern for receiving electromagnetic waves has a substantially polygonal outer shape which is basically a polygon, and at least one corner is formed in a curved shape. By imparting R to the corners, that is, in a curved shape, the shift in frequency at which the electromagnetic wave absorption amount (hereinafter sometimes simply referred to as “absorption amount”) reaches a peak value depending on the polarization direction of the electromagnetic wave is suppressed, The polarization characteristics can be improved. Accordingly, it is possible to realize an electromagnetic wave absorber having an excellent electromagnetic wave absorption characteristic in which the peak value of the electromagnetic wave absorption amount is high and the frequency shift at which the absorption amount reaches the peak value depending on the polarization direction of the electromagnetic wave is small. The ratio R / L between the substantially polygonal side length L and the radius of curvature R of the curved corner is 0.1 to 0.46, and R is 2 to 11.5 mm. .

  The pattern layer may have a configuration in which all the conductive patterns have curved corners, but may not have a configuration in which all the conductive patterns have curved corners. It is sufficient if the pattern has a curved corner. When some of the conductive patterns have curved corners, the other conductive patterns are not limited to the presence or absence of curved corners. Further, the conductive pattern having curved corners may be curved at some corners or may be curved at all corners. The conductive pattern may have a substantially polygonal planar shape or a closed loop linear shape extending in a substantially polygonal shape.

And the part formed in the curve shape in a corner | angular part can be made as small as possible. Accordingly, it is possible to increase the peak value of the electromagnetic wave absorption amount while suppressing the shift of the frequency at which the absorption amount reaches the peak depending on the polarization direction of the electromagnetic wave. That is, the pattern shape is such that the peak value of electromagnetic wave absorption is high and the radius of curvature R is optimized so as to improve the polarization characteristics. Therefore, an electromagnetic wave absorber having extremely excellent electromagnetic wave absorption characteristics can be realized.
Further, the place where the electromagnetic wave absorber is attached is reduced, and for example, the electromagnetic wave can be absorbed by being attached to an object whose surface is made of a non-conductive material. Therefore, convenience is improved.
According to the present invention, the outline shape is a shape formed by a combination of a straight line and a curved line.
According to the present invention, the outer shape has a conductive pattern which is a shape formed by a combination of a straight line and a curved line. Even if R is simply added to the corner, if the whole becomes a curve, the polarization characteristics will be good, but the peak value of the amount of absorption will be small, so the shape of the combination of a straight line and a curve By doing so, it is possible to realize an electromagnetic wave absorber having an excellent electromagnetic wave absorption characteristic in which the peak value of the electromagnetic wave absorption amount is high and the frequency shift at which the absorption amount reaches the peak value depending on the polarization direction of the electromagnetic wave is small.
In the present invention, the substantially polygonal shape is a shape in which four corners of a square are arcuate.
According to the present invention, the conductive pattern has a shape in which four corners of a square are formed in an arc shape. The shape of the square corners in the shape of an arc has a characteristic that the peak value of the electromagnetic wave absorption amount is high, and a characteristic that the shift of the frequency at which the absorption amount reaches the peak value depending on the polarization direction of the electromagnetic wave is small. It is a concrete shape that combines. Therefore, it is possible to specifically realize an electromagnetic wave absorber having excellent electromagnetic wave absorption characteristics having the above-mentioned conflicting characteristics.

In the present invention, the conductive pattern is a planar pattern.
According to the present invention, the pattern layer is laminated on the conductive layer, such as using the electromagnetic wave absorber mounted on an object made of a conductive material on the surface, or further using a conductive reflective layer. By using in a state, a capacitor can be constituted by the conductive pattern of the pattern layer and the conductive layer. Furthermore, since it is a planar pattern, the capacity of the capacitor can be increased. The planar conductive pattern can easily form a capacitor having a large capacity, and the reactance can be adjusted by forming the capacitor, so that the electromagnetic wave absorber using the conductive pattern can be thinned.

  In addition, the present invention is characterized in that conductive patterns having different outer peripheral lengths are formed in combination.

  According to the present invention, the conductive pattern functions as a resonant antenna for electromagnetic waves having a specific frequency. The conductive pattern is designed so that the outer peripheral length corresponds to a wavelength of a specific frequency. Therefore, by forming conductive patterns having different outer peripheral lengths, resonance occurs with respect to the frequencies of two or more electromagnetic waves respectively corresponding to the outer peripheral lengths. As a result, an electromagnetic wave absorber having multi-peak characteristics that absorbs electromagnetic waves having two or more frequencies can be realized. Also in this case, not only the high absorption characteristic but also the polarization characteristic can be improved by providing a curved shape at the corner of the pattern shape.

  In addition, the present invention is characterized in that conductive patterns having different curvature radii at the corners are formed in combination.

  According to the present invention, by forming conductive patterns with different corner radii of curvature, the peak value of electromagnetic wave absorption is reduced compared to the case where only conductive patterns with the same corner radius of curvature are formed. It is possible to change the frequency band (hereinafter sometimes referred to as “absorption band”) of the electromagnetic wave that is absorbed without being absorbed. Changing the absorption band includes widening the absorption band and changing the absorption frequency. For example, by giving a slight difference in the radius of curvature of the corners of adjacent conductive patterns, the absorption band can be widened without decreasing the peak value of the absorption amount of the electromagnetic wave absorber, and for example, adjacent conductive patterns By providing a slightly larger difference in the radius of curvature of the corner of the electromagnetic wave, the frequency of the electromagnetic wave that is absorbed without lowering the peak value of the absorption amount of the electromagnetic wave absorber (hereinafter sometimes referred to as “absorption frequency”) can be lowered. it can.

  In addition, the present invention is characterized in that the interval between two adjacent conductive patterns differs depending on the position.

  According to the present invention, the amount of electromagnetic wave absorption can be increased compared to the case where the interval between two adjacent conductive patterns is constant.

  In the invention, it is preferable that the conductive pattern has one or a plurality of holes, and the holes resonate with an electromagnetic wave having a frequency to be absorbed.

  According to the present invention, a hole is provided in the conductive pattern, and the hole itself can function as a receiving antenna. In other words, a slot pattern (slot antenna) that resonates at a frequency corresponding to the inner peripheral length can be provided in the conductive pattern that resonates at a frequency corresponding to the outer peripheral length, and resonates at a plurality of (two or more) different frequencies. be able to. Thereby, an electromagnetic wave absorber having multi-peak characteristics that absorbs electromagnetic waves having two or more frequencies can be obtained. Furthermore, it is possible to repeatedly provide another conductive pattern inside the slot pattern, which can be used as a resonant antenna to respond to electromagnetic waves of different frequencies, and theoretically absorb electromagnetic waves of three or more frequencies. It is possible to obtain an electromagnetic wave absorber with multimodal characteristics. Also in this case, not only the high absorption characteristic but also the polarization characteristic can be improved by providing a curved shape at the corner of the pattern shape. By repeating this operation, it becomes possible to absorb electromagnetic waves of a larger number (four or more) of frequencies.

In the present invention, the loss layer is
An electromagnetic wave absorbing layer made of a magnetic loss material or al,
And a dielectric layer made of a dielectric material.

  According to the present invention, electromagnetic wave absorption in the loss layer can be improved. Therefore, the electromagnetic wave absorption efficiency in the electromagnetic wave absorber can be increased, and the electromagnetic wave absorber can be thinned.

  The present invention is also characterized in that the real part μ ′ of the complex relative permittivity of the dielectric layer is in the range of 1 to 50.

  According to the present invention, the dielectric constant of the dielectric layer and the electromagnetic wave absorber can be arbitrarily controlled, which can contribute to the reduction in the size of the conductive pattern and the reduction in the thickness of the electromagnetic wave absorber.

Moreover, this invention is the electromagnetic wave absorption method by using the above-mentioned electromagnetic wave absorber.
According to the present invention, electromagnetic waves can be suitably absorbed by using an excellent electromagnetic wave absorber as described above.

  As a specific application of the electromagnetic wave absorber of each of the present invention described above, as an example only, as a floor material, a wall material and a ceiling material forming an electromagnetic environment space such as an office, or a metal surface of furniture and office equipment It can be used as a covering material or as a partition. The electromagnetic wave environment can be improved by arranging the electromagnetic wave absorber according to the present invention for these uses. More specifically, it can be used for the purpose of preventing malfunction of electronic equipment (medical equipment) due to self-wave interference and other-wave interference and protecting the human body from electromagnetic waves. Furthermore, wireless LAN (2.4 GHz band, 4.9 GHz band, 5.2 GHz band, etc.), IC tag (950 MHz band, 2.4 GHz band), DSRC, ETC (5.8 GHz band), and ship laser (9.4 GHz) Band, 3 GHz band), etc., and can be used as a countermeasure against the protection of the electromagnetic wave communication environment, and further as a countermeasure against laser fake image prevention. It can also be used to improve the electromagnetic wave communication environment of wireless communication between ITS-related moving objects that use millimeter wave band electromagnetic waves. And for electromagnetic environment, not only offices, general houses, hospitals, concert halls, factories, research facilities, station buildings, exhibition halls, roadside walls, ships, aircraft, containers, trucks, warehouses, distribution centers, department stores, parking lots, It can also be used at indoor and outdoor facilities such as gas stations, convenience stores, and stores. It can be used for each required location in walls, floors, ceilings, columns, panels, billboards, steel products, desks, partitions, shelves, columns, equipment, metal parts, etc. in each possible environment. The specific application described above is merely an example, and the present invention is not limited to this application, and can be widely used for a variety of applications intended to absorb electromagnetic waves.

  According to the present invention, the peak value of the electromagnetic wave absorption amount is high by using a plurality of conductive patterns that are basically polygonal and include a conductive pattern having at least some corners curved. It is possible to realize an electromagnetic wave absorber having excellent electromagnetic wave absorption characteristics with a small frequency shift in which the absorption amount reaches a peak depending on the polarization direction of the electromagnetic wave.

Moreover, the peak value of the electromagnetic wave absorption amount can be made as high as possible after suppressing the shift of the frequency at which the absorption amount reaches the peak depending on the polarization direction of the electromagnetic wave.
Further, according to the present invention, by forming the conductive pattern in the shape of a combination of a straight line and a curve, an excellent electromagnetic wave having a high peak value of electromagnetic wave absorption and a small frequency shift due to the polarization direction of the electromagnetic wave. An electromagnetic wave absorber having absorption characteristics is realized.
In addition, according to the present invention, an electromagnetic wave absorber having excellent electromagnetic wave absorption characteristics that have contradictory characteristics can be specifically realized.

Moreover, according to this invention, an electromagnetic wave absorber can be reduced in thickness.
In addition, according to the present invention, it is possible to receive electromagnetic waves of a plurality of frequencies by combining conductive patterns having different outer peripheral lengths, and to absorb a plurality (two or more) of electromagnetic waves.

  According to the invention, the electromagnetic wave absorption band can be changed by combining conductive patterns having different curvature radii at the corners. Changing the absorber region includes widening the absorption band and changing the absorption frequency.

In addition , according to the present invention, since the interval between two adjacent conductive patterns varies depending on the position, the amount of electromagnetic wave absorption can be increased as compared with the case where the interval between two adjacent conductive patterns is constant. .

  Further, according to the present invention, by forming a hole in the conductive pattern, it is possible to receive electromagnetic waves of a plurality of frequencies and absorb a plurality (two or more) of electromagnetic waves.

  Moreover, according to this invention, electromagnetic wave absorption in a loss layer can be made favorable and electromagnetic wave absorption amount can be made high.

  Moreover, according to this invention, electromagnetic waves can be suitably absorbed using the electromagnetic wave absorber excellent as mentioned above.

FIG. 1 is a front view of the pattern P showing the influence of the direction of the pattern P on the electric field generated in the pattern P when the pattern P receives an electromagnetic wave that is a TE wave. FIG. 1A shows how an electric field is generated when the two sides of a square pattern P are placed in parallel with each other in the direction of the electric field in electromagnetic waves (hereinafter sometimes referred to as “polarization direction”). 1 (2) shows how the electric field is generated when the pattern P is displaced by 45 degrees (°) from the positional relationship in FIG. 1, and FIG. 1 (3) shows the electric field in the case of the circular pattern P. It shows how it occurs. The positional relationship in FIG. 1A is a positional relationship of a square pattern P having sides parallel or perpendicular to the direction of the electric field in the electromagnetic wave. The positional relationship in FIG. 1B is a positional relationship in which the rectangular conductive pattern P is displaced by 45 degrees (°) from the position in FIG. A square is a quadrangle whose four interior angles are right angles. Each pattern P in FIG. 1 is a conductive pattern.

  As shown in FIG. 1, the direction E of the electric field generated in the pattern P when the electromagnetic wave is received by the pattern P varies depending on the shape of the pattern P. In the case of the square pattern P, the pattern with respect to the polarization direction of the electromagnetic wave. It depends on the positional relationship of P. In the case of FIG. 1A, the direction E of the electric field generated in the pattern P is a linear direction parallel to one side. In the case of FIGS. 1 (2) and 1 (3), the direction E of the electric field generated in the pattern P is substantially hyperbolic.

  When the direction E of the generated electric field changes, the resonance frequency with respect to the electromagnetic wave changes. When receiving electromagnetic waves, particularly TE waves and TM waves, in the rectangular pattern P, if the arrangement shown in FIG. 1A is used, a resonance current tends to flow along the sides in the vicinity of the sides. On the other hand, in the case of FIG. 1 (2) in which the square pattern P is displaced by 45 degrees (°) from FIG. 1 (1) and the case of FIG. It shows that the resonance current cannot be concentrated near the side as the P is used as shown in FIG. Therefore, the pattern used to receive the electromagnetic wave changes depending on the pattern such as a circular pattern in which the reception state is constant and the polarization direction of the electromagnetic wave, regardless of the polarization direction of the electromagnetic wave. There are conductive patterns such as square patterns. In an actual environment where electromagnetic wave absorbers are used, not only linearly polarized electromagnetic waves such as TE waves and TM waves, but also circularly polarized electromagnetic waves exist. It is not always the same direction, and electromagnetic waves with different polarization directions must be absorbed. Therefore, it is necessary to suppress the polarization dependence in which the reception state varies depending on the polarization direction. Improving sex is an important issue. The present invention can solve this problem.

  Furthermore, in the electromagnetic wave absorber that receives electromagnetic waves through the conductive pattern and loses energy in the loss layer, analysis of the trend of electromagnetic wave absorption characteristics due to the shape of the conductive pattern reveals an improvement in electromagnetic wave absorption and polarization dependence The improvement of the polarization characteristics, which is to reduce the number, is not compatible, but rather contradictory. When the shape of the conductive pattern is polygonal, regardless of whether it is linear or planar, the outer shape of the conductive pattern has an acute corner called an edge, and the amount of electromagnetic waves absorbed However, depending on the direction of the electric field of the electromagnetic wave, the frequency shift at which the absorption amount reaches the peak value increases. In addition, when the shape of the conductive pattern is circular, regardless of whether it is linear or planar, the frequency at which the amount of absorption reaches a peak does not shift depending on the polarization direction of the electromagnetic wave. The peak value becomes low.

A conductive pattern having sharp corners such as a polygon has a higher Q value than a circular conductive pattern. The Q value can be expressed by a resonance frequency and a bandwidth, and Q = resonance frequency / bandwidth. The bandwidth is a width of a band having a predetermined reception strength, for example, a reception strength that is one half or more of the reception strength at the resonance frequency ω0. Therefore, assuming that the resonance frequency is ω0 and the frequencies on both sides sandwiching the resonance frequency at which the reception intensity is one half of the reception intensity at the resonance frequency ω0 are ω1 and ω2 (> ω 1 ), respectively, Q = ω0 / (ω2− ω1).

  In order to show the electromagnetic wave absorption characteristics of the patterned electromagnetic wave absorber, this Q value is expressed by applying it to the peak value of the electromagnetic wave absorption amount. A high Q value means that the frequency band of electromagnetic waves to be absorbed (hereinafter sometimes referred to as “absorption band”) is small, but the peak value of the high electromagnetic wave absorption amount (hereinafter sometimes simply referred to as “absorption amount”). It represents having. A low Q value means that the peak value of the absorption amount is small but has a large absorption band width. The absorption band is the frequency of electromagnetic waves that are absorbed with an absorption amount that is greater than or equal to a predetermined absorption amount.

  A conductive pattern having sharp corners has a high Q value, so the peak value of the absorption amount is high, but the width of the absorption band is narrowed, and the resonance frequency shifts due to the difference in polarization direction. Will end up. This is because, in the case of FIG. 1 (1), a strong current is generated along the side of the pattern P and resonance occurs in that portion, whereas in the case of FIGS. 1 (2) and 1 (3), a strong current is generated. As is clear from the case of FIG. 1A, the path through which the current flows is not concentrated along the side. In other words, it can be said that by expanding the current path, the region where the half-wave wave related to resonance is distributed is expanded and the conditions for resonance increase. As a result, the width of the absorption band is increased. In the case of a rectangular conductive pattern, if it is arranged as shown in FIG. 1 (1), an electric field in a straight direction parallel to the side is formed, but if it is displaced by 45 degrees (°) as shown in FIG. 1 (2), Since the electric field is generated in a direction that draws an arc, the distribution is clearly different. That is, the configuration using the rectangular conductive pattern has polarization dependency although the electromagnetic wave absorption characteristic is improved as a result of concentrated resonance. Such a characteristic is not limited to a rectangular shape, and similarly has a configuration using a polygonal conductive pattern.

In this embodiment, the shape of the conductive pattern is optimized, and an excellent patterned electromagnetic wave absorber that can reduce the polarization dependency and increase the electromagnetic wave absorption amount is provided. A pattern electromagnetic wave absorber is an electromagnetic wave absorber provided with a pattern layer having a conductive pattern. In order to improve the above-mentioned drawbacks when using a polygonal conductive pattern, the shape of the conductive pattern is basically a polygon, but at least one corner is formed in a curved shape. . Imparting R to corner, i.e. the effect of the curve shape is that the resonant current flows easily without stagnating at the corners, is that the area to be further resonance becomes wider, the result Q value drops slightly However, the polarization characteristics are improved by exhibiting broadband performance.

  Accordingly, it is possible to suppress a shift in frequency at which the absorption amount reaches a peak value depending on the polarization direction of the electromagnetic wave. Accordingly, it is possible to realize an electromagnetic wave absorber having an excellent electromagnetic wave absorption characteristic in which the peak value of the electromagnetic wave absorption amount is high and the frequency shift at which the absorption amount reaches the peak value depending on the polarization direction of the electromagnetic wave is small.

  FIG. 2 is a cross-sectional view of the electromagnetic wave absorber 1 according to the embodiment of the present invention. For example, the electromagnetic wave absorber 1 for improving the electromagnetic wave environment in a space such as an office is provided with a pattern layer 5, an electromagnetic wave absorption layer 4, a dielectric layer 3, and a conductive reflection layer from the electromagnetic wave incident side above FIG. 2 are stacked in this order from the electromagnetic wave incident side. The pattern layer 5 has a plurality of conductive patterns 12. The conductive pattern 12 can adjust the matching frequency depending on the shapes of the patterns 30 and 31 included in the conductive pattern 12. The electromagnetic wave absorber 1 is used, for example, to absorb an electromagnetic wave of 2.4 GHz or 5.2 GHz.

  FIG. 3 is a front view showing the pattern layer 5 constituting the electromagnetic wave absorber 1 according to the embodiment of the present invention shown in FIG. FIG. 4 is an enlarged front view of a part of the pattern layer 5 in the embodiment shown in FIGS. 2 and 3.

  In the pattern layer 5, the conductive pattern 12 is formed on the surface of the plate-like substrate 11 on the electromagnetic wave incident side. The plate-like substrate 11 is made of, for example, a dielectric that is a synthetic resin, and this plate-like substrate 11 is also a dielectric loss material. The conductive pattern 12 has a radial pattern 30 and a substantially square pattern 31.

  The radial pattern 30 is formed in a radial shape, and a plurality of radial patterns 30 are provided at intervals (hereinafter referred to as “radial pattern intervals”) c2x and c2y. More specifically, for example, in this embodiment, the radial pattern 30 is formed in a cross shape that is radial along the x direction and the y direction perpendicular to each other, with a radial pattern interval c2x in the x direction. , May be regularly arranged in a matrix with radial pattern intervals c2y in the y direction.

  The radial pattern 30 has a shape in which the four corners 21 at the intersecting portion 16 are curved, more specifically, arcuate, based on the cross 20 shown in phantom in FIG. A cross-shaped portion 20 is formed by combining a rectangular shape portion 14 elongated in the x direction and a rectangular shape portion 15 elongated in the y direction by overlapping the centroids of the respective shape portions 14 and 15. The shape intersects at right angles. The shape portions 14 and 15 are shifted by 90 degrees around the vertical axis at the intersection portion 16 and have the same shape. Such a cross-shaped character 20 is divided into four substantially triangular shapes 22 that are right-angled isosceles triangles and have an arc shape in which the hypotenuse opposite to the right-angled corner is concave toward the right-angled corner. It is the shape provided so that it might fit in the corner | angular part 21 of each 20 intersection part 16. FIG.

  When the frequency of the electromagnetic wave to be absorbed is 2.4 GHz, when an example of the size of the radial pattern 30 is given, the widths a1x and a1y of the shape portions 14 and 15 are equal, for example, 1.0 mm. The lengths a2x and a2y of the portions 14 and 15 are equal, for example, 25.0 mm. The dimensions of the corners formed in an arc shape, that is, the length of the side excluding the hypotenuse of the substantially triangle 22, specifically, the length a3x of the side in the x direction and the length a3y of the side in the y direction are For example, 11.5 mm, and the curvature radius R1 of the hypotenuse is 11.5 mm. Regarding the radial pattern interval, the interval c2x in the x direction and the interval c2y in the y direction are equal, for example, 4.0 mm.

The substantially rectangular pattern 31 is arranged in a region surrounded by the radial pattern 30 with a space c1 (hereinafter referred to as “radiation-square interval”) c1 from the radial pattern 30, and fills the region surrounded by the radial pattern 30. It is provided as follows. More specifically, it is formed in a shape corresponding to a region surrounded by the radial pattern portion. Still more particularly, for example, in this embodiment, the radial pattern 30 is cross-shaped as described above, the region surrounded by the radial pattern 30 is substantially rectangular shall be the basis of a rectangle, this , That is, the radiation-square interval c1 is the same over the entire circumference. When the shape portions 14 and 15 have the same shape as described above, the region surrounded by the radial pattern 30 is a substantially square shape based on a square, and the substantially rectangular pattern 31 is a substantially square shape based on the square 25. It becomes. The substantially square pattern 31 is arranged so that the sides of the square 25 serving as a base extend in either the x direction or the y direction.

  The substantially square pattern 31 has a shape in which the four corners 26 are curved, specifically, arcuate, based on the square 25. Specifically, from the square 25, four substantially triangular shapes 27, which are right-angled isosceles triangles and have an arcuate shape in which the hypotenuse opposite to the right-angled corner is concave toward the right-angled corner, Is removed in a positional relationship so as to fit in each corner 26 of the square.

  When the frequency of the electromagnetic wave to be absorbed is 2.4 GHz, taking an example of the dimension of the substantially rectangular pattern 31, the dimension b1x in the x direction and the dimension b1y in the y direction of the square 25 are equal, for example, 25.0 mm. is there. The dimensions of the corners formed in an arc shape, that is, the length of the side excluding the hypotenuse of the substantially triangle 27, specifically, the length b2x of the side in the x direction and the length b2y of the side in the y direction are: For example, 10.0 mm, and the radius of curvature R2 of the hypotenuse is 10.0 mm. In the radiation-square interval, the interval c1x in the x direction and the interval c1y in the y direction are equal, for example, 4.0 mm.

  As described above, the radial pattern 30 and the substantially rectangular pattern 31 are conductive patterns having a substantially polygonal outer shape having a substantially polygonal shape and at least one corner portion being curved. In such a pattern, the resonance current when electromagnetic waves are received flows smoothly at the corners formed in a curved shape.

  The radial pattern 30 and the substantially rectangular pattern 31 are not closed loop lines (bands) extending along the outer peripheral edge of the above-described shape, but are planar patterns in which the inner peripheral portion is also painted. Therefore, a capacitor can be formed between the conductive reflective layer 2.

  In such an electromagnetic wave absorber 1, the electromagnetic wave having the resonance frequency of each conductive pattern 12 can be efficiently received by the pattern layer 5. However, the final resonance frequency is determined not only by the pattern dimensions but also by the influence of the coupling characteristics between the conductive patterns 12 and the impedance determined by the electromagnetic wave absorption layer 4 and the dielectric layer 3. The electromagnetic wave absorbing layer 4 and the dielectric layer 3 are provided in the vicinity of the pattern layer 5, and the energy of the electromagnetic wave received by the pattern layer 5 is lost. In other words, electromagnetic wave energy can be converted into heat energy and absorbed. By using the pattern layer 5 in this way, electromagnetic waves can be received and absorbed efficiently.

  The electromagnetic wave absorbing layer 4 is made of a material that is at least one of a magnetic loss material having a complex relative permeability (μ ′, μ ″) and a dielectric loss material having a complex relative dielectric constant (ε ′, ε ″). The dielectric layer 3 is made of a dielectric loss material having a complex relative dielectric constant (ε ′, ε ″). The conductive reflective layer 2 is a conductive film over the entire surface on the electromagnetic wave incident side of the plate-like substrate. The electromagnetic wave absorber 1 receives an electromagnetic wave having a resonance frequency determined by its shape and size by each conductive pattern 12 of the pattern layer 5 and converts the electromagnetic wave energy into the electromagnetic wave absorbing layer 4. Further, the loss can be absorbed by the loss layer including the dielectric layer 3. Specifically, the energy can be changed into thermal energy and absorbed.

  Since the electromagnetic wave absorber 1 has a laminated structure as described above, the electromagnetic wave absorption efficiency can be increased, so that an electromagnetic wave absorption characteristic having a large amount of electromagnetic wave absorption can be obtained, and a reduction in thickness and weight can be achieved. be able to. For example, compared with a configuration for absorbing 2.45 GHz electromagnetic waves, the electromagnetic wave absorber 1 is thin enough to have a thickness of about 1/3 to about 1/4 compared to a λ / 4 type electromagnetic wave absorber. The thickness can be reduced to about 1/2 and the weight can be reduced to about 1/4 compared with a single-layer electromagnetic wave absorber using rubber ferrite or the like. Further, the conductive pattern 12 can be formed into a planar pattern, and a capacitor can be formed between the conductive reflective layer 2 and the capacitance can be increased to increase the reception efficiency and the electromagnetic wave absorption efficiency.

  The electromagnetic wave absorber 1 is provided with a conductive reflector 2 as an electromagnetic wave shielding plate. When the conductive reflector 2 is not provided, the conductive reflector 2 is installed on the surface of an object having electromagnetic wave shielding performance. This facilitates determination, design, etc. of the shape and dimensions of the pattern layer 5. In this case, in the configuration using the conductive reflector 2, the resonance frequency of the conductive patterns 12, 30, and 31 is prevented from changing due to the influence of the installation location of the electromagnetic wave absorber 1. For example, even if the electromagnetic wave absorber 1 (a structure in which the conductive reflector 2 is not laminated) is provided on a building interior material that does not have conductivity, it is affected by the inherent complex dielectric constant of the interior material. The resonance frequency of the pattern (receiving antenna) may change, but this can be prevented.

  Further, in the conductive pattern 12, the radial pattern 30 is arranged so that the radially extending portions face each other as described above, and the substantially rectangular pattern 31 has a shape corresponding to the region surrounded by the radial pattern 30. It is formed. Such an arrangement has different reception principles (the radiation pattern is a dipole antenna and the square pattern is a patch antenna), and the reception efficiency is optimal (higher) by combining the radiation pattern 30 and the square pattern 31. It is a combination. Therefore, an electromagnetic wave absorber with high absorption efficiency can be realized. Further, the radial pattern 30 is arranged so as to radiate along the x direction and the y direction, and the square sides that form the basis of the substantially rectangular pattern 31 are arranged so as to extend in the x direction and the y direction. The reception efficiency of polarized electromagnetic waves can be increased so that the direction of the electric field exists in the y direction.

  In the electromagnetic wave absorber 1, the conductive pattern 12 that receives an electromagnetic wave has a substantially polygonal outer shape that is basically a polygon, and the peak value of the electromagnetic wave absorption amount is determined by the outer shape of the conductive pattern. Compared with a circular case, the peak value of the electromagnetic wave absorption can be increased. Thus, it is basically a polygon, and at least one corner is formed in a curved shape. Accordingly, it is possible to suppress a shift in frequency at which the absorption amount reaches a peak depending on the polarization direction of the electromagnetic wave. Therefore, it is possible to obtain excellent electromagnetic wave absorption characteristics in which the peak value of the electromagnetic wave absorption amount is high and the frequency shift at which the absorption amount reaches the peak value depending on the polarization direction of the electromagnetic wave is small.

  As described above, the electromagnetic wave absorber 1 of the present embodiment receives an electromagnetic wave having a specific frequency by the conductive pattern 12 of the pattern layer 5 according to the resonance principle of the antenna. In other words, in addition to absorbing electromagnetic waves, the electromagnetic wave absorber of the present invention has a function that the conductor pattern 12 operates effectively as a receiving antenna in the presence of a metal (conductive reflective layer 2) nearby. ing. Here, the specific frequency is a frequency determined by specifications such as the shape and dimensions of the conductive pattern 12 and is a frequency to be absorbed by the electromagnetic wave absorber 1. When the electromagnetic wave is received by the conductive pattern 12, a resonance current flows through the end portion of the conductive pattern 12. When this current flows, a magnetic field is generated around the current. The magnetic flux density is distributed in a larger state as it is closer to the current. When a loss layer having a magnetic loss material is provided near the pattern layer 5, the magnetic field can be lost energetically. Thus, the energy of electromagnetic waves can be changed to heat energy and absorbed. In the present embodiment, the loss layer includes the electromagnetic wave absorption layer 4 and the dielectric 3.

  Further, the electromagnetic wave absorber 1 is used by being attached to an object whose surface is made of a conductive material, or a conductive reflective layer is further provided on the opposite side of the pattern layer 5 with respect to the loss layer. Between the conductive pattern 12 of the pattern layer 5 and the conductive layer (the surface layer of the object made of a conductive material or the conductive reflective layer). Can be configured. When the distance between the conductive pattern 12 and the conductive layer is shortened, the capacitance of the capacitor can be increased. Capacitors can also be formed between the patterns. As described above, the pattern electromagnetic wave absorber can be thinned by providing a reactance adjusting function by using a capacitor.

  FIG. 5 is a cross-sectional view of an electromagnetic wave absorber 1 according to another embodiment of the present invention. This embodiment is similar to each of the embodiments shown in FIGS. 2 to 4 described above, and corresponding portions are denoted by the same reference numerals. Particularly in this embodiment, the electromagnetic wave absorption layer 4, the pattern layer 5, the dielectric layer 3, and the conductive reflection layer 2 are laminated in this order from the electromagnetic wave incident side. Other configurations are the same as those of the above-described embodiment.

  Calculation of the electromagnetic wave absorption amount (reflection loss amount) of the present invention is performed by computer simulation. The simulation uses the TLM method and uses “Micro-Stripes” manufactured by KCC. In the calculation, the material constant of the electromagnetic wave absorbing layer 4, for example, 2.4 GHz is as follows: real part ε ′ = 12.2 of complex relative permittivity, imaginary part ε ″ = 1.13 of complex relative permittivity, complex relative permeability Real part μ ′ = 1.02, complex relative permeability imaginary part μ ″ = 0.48, and thickness was 0.5 mm. The material constant of the dielectric layer 3, for example, 2.4 GHz is ε ′ = 3.79 and ε ″ = 0.03, and the thickness is 2.0 mm. That is, the thickness is as a 2.4 GHz band electromagnetic wave absorber. A thin thickness of 2.5 mm (0.5 mm thickness for the magnetic permeability layer) is realized, but the material constant and thickness are not limited to these values, and any combination can be selected. For example, in order to further reduce the thickness, it is possible to manufacture products having a total thickness of 0.5 mm or 1.0 mm by the wavelength shortening effect by improving ε ′ and μ ′.

  FIG. 6 is a cross-sectional view of an electromagnetic wave absorber 1 according to still another embodiment of the present invention. This embodiment is similar to the embodiment of FIGS. 2 to 4 described above, and corresponding portions are denoted by the same reference numerals. In particular, in this embodiment, the surface layer 6 may be further formed on the electromagnetic wave incident side (upper side in FIG. 6) of the pattern layer 5 as described above. The configuration is not limited to the configuration shown in FIGS. 5 and 6. For example, an electromagnetic wave absorbing layer 4, a pattern layer 5, an electromagnetic wave absorbing layer 4, a dielectric layer 3, and a conductive reflective layer 2 may be configured in this order from the electromagnetic wave incident side.

As an embodiment of the present invention, a laminated body in the order of the pattern layer 5, the electromagnetic wave absorption layer 4, the dielectric layer 3, and the conductive reflection layer 2 from the direction of incidence of radio waves, the electromagnetic wave absorption layer 4, the pattern layer 5, Laminate in order of dielectric layer 3, conductive reflective layer 2, electromagnetic wave absorbing layer 4, pattern layer 5, electromagnetic wave absorbing layer 4, dielectric layer 3, laminated body in order of conductive reflective layer 2, pattern layer 5 , there is a dielectric layer 3, and a laminate in the order of the conductive reflective layer 2. It is not limited to these, The laminated body of various aspects is included. Further, these laminates are obtained by extracting main layers, and are not necessarily arranged in this manner. For example, the same effect can be obtained even if an adhesive layer, a support, a protective layer, or the like is inserted between the layers. Moreover, it is also possible to combine the adhesive layer with the dielectric layer 3 and the electromagnetic wave absorbing layer 4 by blending with the adhesive.

  In still another embodiment of the present invention, the electromagnetic wave absorber does not include the conductive reflective layer 2 in each of the embodiments of FIGS. 2 to 6, and does not include such a conductive reflective layer 2. However, it is configured to be installed on a surface having electromagnetic wave shielding performance on the side opposite to the electromagnetic wave incident side (upper side of FIGS. 5 and 6) of the dielectric layer 3 (lower side of FIGS. 5 and 6). Also good. The surface having electromagnetic wave shielding performance may have the same configuration as that of the conductive reflective layer 2, for example, and may be realized by a metal plate, for example. Such a configuration can achieve electromagnetic wave absorption characteristics similar to those of the electromagnetic wave absorber having the conductive reflective layer 2.

  FIG. 7 is a front view showing a pattern layer 5 constituting an electromagnetic wave absorber 1 according to still another embodiment of the present invention. In the present embodiment, the pattern layer 5 shown in FIG. 7 is used instead of the pattern layer 5 shown in FIGS. Other configurations are the same as those in FIGS. The conductive pattern 12 of the pattern layer 5 shown in FIGS. 3 and 4 has a radial pattern 30 and a substantially square pattern 31, but the conductive pattern 12 of the pattern layer 5 of FIG. Only the pattern 31 is included. Even if it is such a structure, the same effect can be achieved.

  FIG. 8 is a front view showing a pattern layer 5 constituting an electromagnetic wave absorber 1 according to still another embodiment of the present invention. In the present embodiment, the pattern layer 5 shown in FIG. 8 is used instead of the pattern layer 5 shown in FIGS. Other configurations are the same as those in FIGS. The conductive pattern 12 of the pattern layer 5 shown in FIGS. 3 and 4 has a radial pattern 30 and a substantially square pattern 31, but the conductive pattern 12 of the pattern layer 5 of FIG. Only the pattern 30 is included. Even if it is such a structure, the same effect can be achieved.

  FIG. 9 is a front view showing a substantially square pattern 41 according to still another embodiment of the present invention. In the present embodiment, a substantially square pattern 41 shown in FIG. 9 is used in place of the substantially square pattern 31 shown in FIGS. 3, 4 and 7. Other configurations are the same as those in FIGS. Although the substantially square pattern 31 shown in FIGS. 3, 4 and 7 is a planar pattern, the substantially square pattern 41 of FIG. 9 is a closed loop linear (band) pattern extending along the outer peripheral edge. is there. Even if it is such a structure, although the capacity | capacitance of the capacitor | condenser formed between the electroconductive reflection layers 2 becomes small, the same effect can be achieved.

  FIG. 10 is a front view showing a radial pattern 40 according to still another embodiment of the present invention. In the present embodiment, a radial pattern 40 shown in FIG. 10 is used in place of the radial pattern 30 shown in FIGS. Other configurations are the same as those in FIGS. 2 to 6 and 8. Although the radial pattern 30 shown in FIGS. 3, 4 and 8 is a planar pattern, the substantially radial pattern 40 of FIG. 10 is a closed loop linear (band) pattern extending along the outer peripheral edge. is there. Even if it is such a structure, although the capacity | capacitance of the capacitor | condenser formed between the electroconductive reflection layers 2 becomes small, the same effect can be achieved.

  FIG. 11 is a graph showing a simulation result of electromagnetic wave absorption characteristics. The configuration of the electromagnetic wave absorber 1 is as shown in FIG. In FIG. 11, the horizontal axis indicates the frequency, and the vertical axis indicates the reflection loss. The reflection loss indicates that the smaller the value, the greater the amount of electromagnetic wave absorbed. The reflection characteristics were determined for the electromagnetic wave absorber in which squares and substantially square and circular patterns with arcs at the corners were arranged as shown in FIG. All conditions except for the radius of curvature of the corners are the same.

  Regardless of the subscripts “a” and “b”, the lines 50 a and 50 b denoted by reference numeral 50 indicate the electromagnetic wave absorption characteristics of a square pattern. Regardless of the suffixes “a” and “b”, the lines 51 a and 51 b denoted by reference numeral 51 indicate the electromagnetic wave absorption characteristics of a circular pattern. Regardless of the subscripts “a” and “b”, the lines 52 a and 52 b denoted by reference numeral 52 indicate electromagnetic wave absorption characteristics of a pattern in which corners are arc-shaped with a small radius of curvature based on a square. Regardless of the subscripts “a” and “b”, the lines 53 a and 53 b denoted by reference numeral 53 indicate electromagnetic wave absorption characteristics of a pattern in which corners are arc-shaped with an intermediate radius of curvature based on a square. Regardless of the subscripts “a” and “b”, the lines 54 a and 54 b denoted by reference numeral 54 indicate electromagnetic wave absorption characteristics of a pattern in which corners are arc-shaped with a small radius of curvature based on a square. For each pattern, the electromagnetic wave absorption characteristics with respect to electromagnetic waves having different polarization directions by 45 degrees (°) are indicated by subscripts “a” and “b”.

  In the square pattern (without R), the Q value is high and the peak value (peak absorption amount) of the electromagnetic wave absorption amount is large, but the frequency band where the absorption amount is large is small, and this band is set to the target frequency to be absorbed. Try to adjust it to fit. Moreover, depending on the polarization direction of the electromagnetic wave, the frequency at which the absorption amount of the electromagnetic wave reaches a peak (peak frequency) is greatly shifted, and the polarization characteristics are poor. In the circular pattern, the polarization characteristics are very good, but the Q value is low and the peak absorption amount is small. On the other hand, in a pattern (square with R) having corners curved with a square as a basis, the peak absorption amount is large and the polarization characteristics are good.

As is clear from FIG. 11, in the pattern in which the corners are curved on the basis of a square, the size of the portion formed in a curved shape at the corners has a frequency shift that can be absorbed due to the difference in polarization direction. There is a range that can be suppressed, that is, a polarization characteristic equivalent to a circular shape can be obtained. In the case of FIG. 11, good polarization characteristics are obtained in the pattern of two radii on the larger side among the curvature radii of the three corners. The peak absorption amount increases as the radius of curvature of the corner portion decreases. Therefore, the corner portion has a curvature with a dimension as small as possible within the range where polarization characteristics similar to a circle can be obtained. It is preferable to use a curve with a radius. The side of the corresponding square 25 of the substantially square pattern 31 in the case of FIG. 11 is 8 mm, and the sample having an arrangement parallel to the polarization direction is at the 0 degree (°) position (solid line in the figure, Hereinafter, the reflection loss may be referred to as “0 degree (°) polarization”, the reflection loss when R = 2 is −17 dB, the reflection loss when R = 3 is −14 dB, and the position of 0 degree (°). Even when the material is displaced by 45 degrees (°) (the broken line in the figure, sometimes referred to as “45 degrees (°) polarization” hereinafter), there is almost no shift in the absorption frequency and the polarization characteristics are good. I know that there is.

  The reflection loss is a loss from the viewpoint that the electromagnetic wave incident on the electromagnetic wave absorber is reflected by the electromagnetic wave absorber, and represents the loss due to the electromagnetic wave being absorbed by the electromagnetic wave absorber. It is a value corresponding to the amount of electromagnetic waves absorbed. The reflection loss is represented by a negative value, and the absolute value of the reflection loss is the amount of electromagnetic wave absorption.

  FIG. 12 is a graph showing a change in electromagnetic wave absorption characteristics depending on the size of a portion formed in a curved shape in a corner portion in a conductive pattern in which the corner portion is curved in a square shape. FIG. 12 shows an example in which, by providing a curved portion at the corner of the conductive pattern, the Q value is increased, the reflection loss is increased, and the electromagnetic wave absorption characteristics are improved. In the example of FIG. 12, the side length of the conductive pattern is 20 mm.

  When the radius of curvature R = 0 mm, the reflection loss of electromagnetic waves with 0 degree (°) polarization is indicated by a line 60 and the peak value is −23 dB (2.6 GHz), but the radius of curvature R = 2 mm. The reflection loss of electromagnetic waves with 0 degree (°) polarization is indicated by a line 61, and the peak value is −32 dB (2.65 GHz). Thus, it is considered that by applying R (curve portion formation), the flow of the resonance current becomes smooth and the Q value is increased. This indicates that the square pattern is not always in the state with the highest Q value. If the radius of curvature R is further increased, the value of the reflection loss is decreased and a tendency to shift to the high frequency side is also observed. In the case of the radius of curvature R = 10 mm, the reflection loss of electromagnetic waves with 0 degree (°) polarization is indicated by a line 63, and the peak value is lower than the case of the radius of curvature R = 0 mm. Therefore, in order to improve the reflection loss, it can be said that the range of the radius of curvature R is preferably 1 mm <R <20 mm.

The reflection loss of 45 degree (°) polarized electromagnetic waves when the radius of curvature R = 0 mm is indicated by a line 63, and the reflection loss of 45 degree (°) polarized electromagnetic waves when the curvature radius R = 2 mm. The reflection loss of 45-degree (°) polarized electromagnetic waves when the radius of curvature R is 10 mm is indicated by a line 65. The reflection loss of electromagnetic waves with 0 degree (°) polarization when the radius of curvature R = 4 mm is indicated by a line 66, and the reflection loss of electromagnetic waves with 45 degree (°) polarization when the radius of curvature R = 4 mm. Is indicated by line 67. The reflection loss improvement effect including the polarization characteristics is most excellent when the radius of curvature is R = 4 mm. (Reflection loss is -29 dB) From these results, it is shown that by adding R to the pattern shape, shift control of the absorption frequency to the high frequency side and further optimization of the Q value may be achieved. It can be seen that this is an effective means for adjusting the electromagnetic wave absorption characteristics. Further , when the shift of the absorption characteristic is calculated when the angle is displaced by 45 degrees (°) (45 degrees (°) polarized wave), the effect of improving R is surely confirmed.

  In the present embodiment, the dimension of the curved portion at the corner is determined to be a small dimension within a range of dimensions capable of suppressing the frequency shift that can be absorbed due to the difference in polarization direction. With such a configuration, a portion formed in a curved shape at the corner can be made as small as possible. As is apparent from FIGS. 11 and 12, the peak value of the electromagnetic wave absorption amount can be made as high as possible after suppressing the frequency shift at which the absorption amount reaches the peak depending on the polarization direction of the electromagnetic wave. That is, as the radius of curvature of the corner curve increases, the pattern shape approaches a circle and eventually becomes a circle. Accordingly, the Q value decreases and the electromagnetic wave absorption characteristics tend to decrease, but the polarization characteristics improve. Therefore, by determining the size of the portion formed in a curved shape in the corner portion to a small size within the range of the size that can suppress the shift of the frequency that can be absorbed due to the difference in the polarization direction, the electromagnetic wave absorption characteristics are high, However, the pattern shape has an optimized radius of curvature R so as to improve polarization characteristics. Therefore, an electromagnetic wave absorber having extremely excellent electromagnetic wave absorption characteristics can be realized.

  FIG. 13 is a graph showing a comparison between the calculated value and the actually measured value of the electromagnetic wave absorption characteristics of the electromagnetic wave absorber 1 based on the pattern arrangement of FIG. A line 70 indicates the calculated value of the electromagnetic wave absorption characteristic of the electromagnetic wave with 0 degree (°) polarization, and a line 71 indicates the calculated value of the electromagnetic wave absorption characteristic of the electromagnetic wave with 45 degree (°) polarization. A line 72 indicates an actual measurement value of the electromagnetic wave absorption characteristic of the electromagnetic wave of 0 degree (°) polarized TE wave, and a line 73 indicates an actual measurement value of the electromagnetic wave absorption characteristic of the electromagnetic wave of 0 degree (°) polarized TM wave. A line 74 indicates an actual measurement value of electromagnetic wave absorption characteristics of 45-degree (°) polarized TE waves, and a line 75 indicates an actual measurement value of electromagnetic wave absorption characteristics of 45-degree (°) polarized TM waves.

The electromagnetic wave absorber 1 using the substantially square pattern 31 is designed to match the electromagnetic wave absorption peak to 2.45 GHz. In the calculated value, a reflection loss of about −17 dB was observed, and there was hardly any shift in the absorption characteristics of 45 degrees (°) polarization . The actually measured values are electromagnetic wave absorption characteristics by the free space method with respect to the TE wave and the TM wave in 0 degree (°) polarization and 45 degree (°) polarization . The actual measured reflection loss (corresponding to electromagnetic wave absorption) is -15 to -19 dB (including TE and TM waves, including 0 ° and 45 ° polarized waves), and there is little difference from the calculated value, and the bandwidth is measured. The value is slightly larger. Absorption characteristics excellent in polarization characteristics were observed due to the R imparting effect.

  FIG. 14 is a graph showing the electromagnetic wave absorption characteristics of the electromagnetic wave absorber 1 in which R-applied substantially rectangular patterns 31 having different sizes are arranged and aimed to absorb electromagnetic waves of two frequencies. FIG. 15 is a front view showing a part of the arrangement of the conductive pattern showing the electromagnetic wave absorption characteristics of FIG. As another embodiment of the present invention, conductive patterns having different outer peripheral lengths are formed in combination. In the present embodiment, as the substantially square pattern 31, a first substantially square pattern 31a whose corresponding square 25 has a side length of 10 mm and a second substantially rectangular pattern 31b whose corresponding square 25 has a side length of 24 mm are used. A square pattern unit having a side length of 27 mm shown in FIG. 15 is repeatedly arranged so as to have a mirror surface in the x direction and the y direction to form the pattern layer 5. In other words, the first substantially square patterns 31b are arranged in a checkered pattern, and four second substantially square patterns 31a are arranged in a matrix between the first substantially square patterns 31b.

In FIG. 14, a solid line 70 indicates an electromagnetic wave absorption characteristic of 0 degree (°) polarization, and a broken line 71 indicates an electromagnetic wave absorption characteristic of 45 degree (°) polarization. In this electromagnetic wave absorber 1, the reflection loss (electromagnetic wave absorption characteristics) shows two absorption peaks of about −10 dB at 2.45 GHz and 5.2 GHz. Further, when calculating the shift of the absorption characteristic of 45 degrees (°) polarization , it can be seen that there is almost no shift, and the effect of improving the R addition is surely confirmed.

  Table 1 shows a comparison of electromagnetic wave absorption characteristics when the substantially square patterns 31 having different curvature radii R are combined.

  FIG. 16 is a graph showing a comparison of electromagnetic wave absorption characteristics when the substantially square patterns 31 having different curvature radii R are combined. As another embodiment of the present invention, conductive patterns having different corner radii of curvature are combined and formed. In the present embodiment, in the configuration in which the substantially rectangular patterns 31 shown in FIG. 7 are arranged, the substantially rectangular patterns 31 adjacent to each other in the x direction and the y direction have different curvature radii R, and the curvature radii R of the corners are different. A substantially square pattern 31 having a first value and a substantially square pattern 31 having a second radius of curvature R at each corner are arranged in a checkered pattern. The first value and the second value are different. The curvature radius R corresponds to the curvature radius R1 at the corner of the substantially rectangular pattern 31 in FIGS. 3 and 4 used in the description of FIG. 7, but “R” is used for convenience.

  FIG. 16 shows electromagnetic wave absorption characteristics depending on the difference in the radius of curvature R of the substantially rectangular pattern 31 adjacent in the x direction and the y direction in the configuration in which the substantially square patterns 31 are arranged as shown in FIG. In FIG. 16, each line 100-103 shows the electromagnetic wave absorption characteristic of the structure which formed each square corner | angular part whose length of one side is 23 mm in the shape of a curve. The interval between the squares is 6 mm. A broken line 100 indicates electromagnetic wave absorption characteristics when the curvature radius R of the substantially rectangular pattern 31 adjacent in the x direction and the y direction is the same 7 mm. A solid line 101 has a radius of curvature R of each corner of one of the substantially rectangular patterns 31 among the substantially rectangular patterns 31 adjacent to each other in the x direction and the y direction, and each corner of the other substantially square pattern 31. The electromagnetic wave absorption characteristics when the radius of curvature R is 8 mm are shown. A dotted line 102 indicates that, among the substantially rectangular patterns 31 adjacent to each other in the x direction and the y direction, the curvature radius R of each corner of one of the substantially rectangular patterns 31 is 5 mm, and each corner of the other substantially rectangular pattern 31 The electromagnetic wave absorption characteristics when the radius of curvature R is 9 mm are shown. An alternate long and short dash line 103 indicates that, among the substantially rectangular patterns 31 adjacent to each other in the x direction and the y direction, the curvature radius R of each corner of one of the substantially rectangular patterns 31 is 4 mm, and each corner of the other substantially rectangular pattern 31 Electromagnetic wave absorption characteristics when the radius of curvature R is 10 mm are shown.

  A broken line 100 indicates the electromagnetic wave absorption characteristics of the configuration described as “one type” in Table 1. A solid line 101 indicates the electromagnetic wave absorption characteristics of the configuration described as “2 types 1” in Table 1. A dotted line 102 indicates the electromagnetic wave absorption characteristics of the configuration indicated as “two types 2” in Table 1. An alternate long and short dash line 103 indicates the electromagnetic wave absorption characteristics of the configuration described as “2 types 3” in Table 1. In Table 1, the width of the absorption band indicates the width of the frequency band in which the reflection loss is −20 dB, −15 dB, −10 dB, −6 dB or more.

  By making the radius of curvature R of the corners of adjacent substantially rectangular patterns 31 different, the outer peripheral lengths of the substantially rectangular patterns 31 are different, and the resonance frequencies are different accordingly. The difference in electromagnetic wave absorption characteristics between the case where the radius of curvature R of the adjacent substantially square pattern 31 is the same and the case where it is different is, for example, if the radius of curvature R is increased, the outer periphery of the substantially square pattern 31 according to the ratio. It is not a simple difference such that the length becomes shorter and the resonance frequency shifts to a higher frequency. As is clear from FIG. 16, when the radius of curvature R of two adjacent substantially rectangular patterns 31 is held so that the total value is constant and the difference is increased, the electromagnetic wave absorption frequency is shifted to the lower frequency side. To do. The absorption frequency is a frequency at which the absorption amount reaches a peak value.

  In addition, when the difference between the curvature radii R of two adjacent substantially rectangular patterns 31 is small, in the example shown in FIG. 16, when the difference is 2 mm, the peak value of the electromagnetic wave absorption amount is the curvature of the two adjacent substantially rectangular patterns 31. The absorption band is widened while maintaining the peak value of the absorption amount when the radius R is the same. This inventor confirmed that the phenomenon that the absorption band is widened occurs when the distance between adjacent conductive patterns is relatively close, in other words, when the distance between the conductive patterns is such that an interference effect can be seen. Has been. When the difference between the radii of curvature R of two adjacent substantially rectangular patterns 31 is further increased, the absorption frequency shifts to a low frequency without significantly reducing the peak value of electromagnetic wave absorption. In the example shown in FIG. 16, especially when the difference in curvature radius is 4 mm or less, the peak value of the electromagnetic wave absorption amount is the peak value of the absorption amount when the curvature radii R of two adjacent substantially rectangular patterns 31 are the same. Is maintained.

  Thus, it is clear that the radius of curvature R of two adjacent substantially rectangular patterns 31 contributes effectively as a design parameter of the electromagnetic wave absorber. A peculiar phenomenon occurs due to interference and influence between adjacent conductive patterns. By combining a plurality of conductive patterns whose resonance frequencies are close due to the difference in the radius of curvature R at the corner, the absorption band and the absorption frequency change. Compared with the case where the radius of curvature R of the adjacent conductive pattern is made the same by making the radius of curvature R of the adjacent conductive pattern different from each other, and the effect of the adjacent conductive patterns exerting on each other. The absorption frequency can be changed while maintaining the peak value of the absorption amount.

  In this way, according to the configuration in which the radius of curvature R of the corner portions of the adjacent conductive patterns is different, the peak value of the electromagnetic wave absorption amount is obtained when only the conductive pattern having the same radius of curvature of the corner portions is formed. The absorption band can be changed without lowering. For example, by giving a slight difference in the radius of curvature of the corners of adjacent conductive patterns, the absorption band can be widened without decreasing the peak value of the absorption amount of the electromagnetic wave absorber, and for example, adjacent conductive patterns By providing a slightly larger difference in the radius of curvature of the corner of the electromagnetic wave, the frequency of the electromagnetic wave that is absorbed without lowering the peak value of the absorption amount of the electromagnetic wave absorber (hereinafter sometimes referred to as “absorption frequency”) can be lowered. it can.

  In FIG. 17, a hole portion (slot antenna portion) 75 is provided in the substantially rectangular pattern 31 provided with R, and the pattern layer 5 in which the small-sized substantially square pattern 31 is further arranged in the hole portion 75 is provided. 3 is a graph showing electromagnetic wave absorption characteristics of the electromagnetic wave absorber 1. FIG. 18 is a front view showing a part of the array of conductive patterns showing the electromagnetic wave absorption characteristics of FIG. In this example, as the substantially square pattern 31, the corresponding square 25 has a side length of 24 mm, and a substantially square (four corners are curved) holes in a direction inclined by 45 degrees (°). The first substantially square pattern 31c in which 75 is formed and the second substantially square pattern 31d which is arranged in the same direction as the first substantially square pattern 31c and is formed inside the hole portion 75 are provided. It is done. The side length of the hole 75 is 16 mm, and the second substantially square pattern 31d is 10 mm.

  FIG. 17 shows a calculation result of the reflection loss of the electromagnetic wave absorber 1 using the pattern layer 5 in which the pattern units shown in FIG. 18 are repeatedly arranged in the x direction and the y direction. In FIG. 17, the solid line 80 indicates the electromagnetic wave absorption characteristic of 0 degree (°) polarization, and the broken line 81 indicates the electromagnetic wave absorption characteristic of 45 degree (°) polarization. In the electromagnetic wave absorber 1 in this case, electromagnetic wave absorption is observed in three bands according to each antenna, which is −3.5 dB at 1.8 GHz, −9 dB at 5.4 GHz, −18 dB at 7.5 dB. When calculating the shift of the absorption characteristic when tilted by 45 °, it can be seen that there is almost no shift, and the effect of improving R provision is surely confirmed.

  According to the configuration shown in FIGS. 17 and 18, the hole portion 75 is provided in the first substantially rectangular pattern 31 c that is a conductive pattern, and the hole portion itself can function as a receiving antenna. That is, a slot pattern (slot antenna portion) 75 that resonates with respect to the frequency corresponding to the inner peripheral length can be provided in the substantially rectangular pattern 31c that resonates with the frequency corresponding to the outer peripheral length, and is approximately one conductive pattern. The rectangular pattern 31c can resonate with a plurality of (two or more) different frequencies. Thereby, it is possible to obtain an electromagnetic wave absorber having a bimodal characteristic that absorbs electromagnetic waves of two frequencies corresponding to the outer peripheral length of one conductive pattern and the inner peripheral length of one slot pattern formed thereon.

  Further, when a plurality of slot patterns are formed in one conductive pattern and the inner peripheral lengths of the respective slot patterns are different, a multi-peak that absorbs electromagnetic waves having a frequency equal to the number of slot patterns + 1 by one conductive pattern. A characteristic electromagnetic wave absorber can be obtained. Further, it is possible to repeatedly provide another conductive pattern inside the slot pattern, which can be used as a resonant antenna to correspond to an electromagnetic wave of another frequency, and further increase the absorption frequency so that one conductive pattern is provided. By forming one slot pattern in the sex pattern and theoretically absorbing an electromagnetic wave having three or more frequencies, an electromagnetic wave absorber having multi-peak characteristics can be obtained. Also in this case, not only the high absorption characteristic but also the polarization characteristic can be improved by providing a curved shape at the corner of the conductive pattern. By repeating this operation, it becomes possible to absorb electromagnetic waves of a larger number (four or more) of frequencies.

  The manufacturing method of the electromagnetic wave absorber 1 in the present invention is, for example, the following method. The pattern layer 5 is manufactured by forming a conductive pattern having a predetermined shape by an etching method using an aluminum-deposited PET film (film thickness = 25 μm, aluminum thickness≈600 to 800 Å). The electromagnetic wave absorbing layer 4 is formed by blending 340 parts of ferrite and 50 parts of carbon black into 100 parts of SBS (styrene / butadiene / styrene copolymer) resin, kneading with other fillers, and sheeting to 0.5 mm thickness. is doing. The dielectric layer 3 is formed by filling an SBS (styrene / butadiene / styrene copolymer) resin with an inorganic material and other fillers (no magnetic loss material is used) and then sheeting to 2.0 mm thickness. Is done. The material constant of each layer is processed into a ring shape of φ7 × φ3, measured by a network analyzer by the coaxial tube method, and the blending is adjusted so as to obtain a desired material constant. As other fillers, flame retardants, anti-aging agents, processing aids, inorganic fillers and the like are appropriately used.

  Each of these layers was laminated via an adhesive, and was cut into a size of 50 cm × 50 cm after the adhesion reaction was completed.

  Examples of the ferrite include soft ferrite such as Mn—Zn ferrite, Ni—Zn ferrite and Mn—Mg ferrite, or hard ferrite which is a permanent magnet material. Examples of iron alloys include magnetic stainless steel (Fe—Cr—Al—Si alloy), sendust (Fe—Si—Al alloy), perm alloy (Fe—Ni alloy), silicon copper (Fe—Cu—Si alloy), Fe -Si-B (-Cu-Nb) alloy, Fe-Si-Cr alloy, Fe-Ni-Cr-Si alloy etc. are mentioned. In addition, in these alloys, you may use a flat thing. Examples of the iron particles include carbonyl iron powder. In the case of carbonyl iron, it should be as close to a true sphere as possible. If it is a magnetic material, there is no restriction | limiting in the shape, A block shape, a flat shape, a fiber shape, etc. can be used suitably. It is preferable to use soft ferrite powder with low complex cost and high complex relative permeability. If there is no magnetic loss material such as ferrite, thinning using complex relative permeability cannot be achieved. Further, the electromagnetic wave absorbing layer 4 may be formed of a magnetic material itself. In this case, a method of forming a soft magnetic sintered body such as ferrite, a plated product thereof, a layer of a metal compound or a metal oxide is employed.

The dielectric loss material included in the electromagnetic wave absorbing layer 4 or, if necessary, the dielectric layer 3 is an electromagnetic wave absorbing material that is a material selected from the group consisting of graphite, carbon black, carbon fiber, graphite fiber, metal powder, and metal fiber. Is the body. The electromagnetic wave absorbing layer 4 contains a magnetic loss material as an essential component, but it is also preferable to give an appropriate complex relative dielectric constant for impedance matching. For this purpose, the dielectric loss material filled in the electromagnetic wave absorption layer 4 or, if necessary, the dielectric layer 3 is, for example, carbon black such as furnace black or channel black, conductive particles such as stainless steel, copper or aluminum, fiber, graphite , Carbon fiber, graphite fiber, titanium oxide and the like. The dielectric material preferably used in the present invention is carbon black, in particular, a nitrogen adsorption specific surface area (ASTM (American Society for Testing and Materials) D3037-93) of 100 to 1000 m ² / g, DBP oil absorption (ASTM D2414- 96) is preferably 100 to 400 ml / 100 g, for example, trade name IP1000 manufactured by Showa Cabot and trade name Ketjen Black EC manufactured by Lion Akzo. Because the DBP oil absorption is a DBP which is a kind of plasticizer absorption of (abbreviation of dibutyl phthalate) (unit ^cm 3 / 100g).

  As the organic polymer material (vehicle) used for the electromagnetic wave absorbing layer 4 and the dielectric layer 3, synthetic resin, rubber, and thermoplastic elastomer are used. For example, thermoplastics such as polyethylene, polypropylene, copolymers thereof, polyolefins such as polybutadiene and copolymers, polyurethane, polyvinyl chloride, polyvinyl acetate, epoxy resins, phenol resins, melamine resins, or thermosetting resins. Resin and bitumen are listed. Resins having biodegradability such as polyuric acid can also be used. Further, the FRP may be filled with a material such as glass fiber.

  The electromagnetic wave absorbing layer 4 may be a gypsum material, cement material, or non-woven fabric, foam, paper, cardboard or the like impregnated with a magnetic paint or the like other than the organic polymer, and contains a filler. A material that can be selected can be selected as appropriate.

  The dielectric layer 3 is not limited to the one using an organic polymer material, and any material can be used as long as it has a complex dielectric constant and does not exhibit conductivity. For example, wood, plywood, paper, gypsum, cement, clay, sand, earth, non-woven fabric, recycled resin, incombustible board, bitumen, asphalt, foam and the like can be used.

  The electromagnetic wave absorbing layer 4 can also serve as an adhesive layer. For example, an epoxy resin can be blended with ferrite or a dielectric loss material so that it can be positioned between the layers of the pattern layer 5, the dielectric layer 3, and the conductive reflective layer 2 when used in each interface or lamination. In this case, as described above, a configuration in which a plurality of electromagnetic wave absorbing layers 4 and dielectric layers 3 are alternately laminated can be employed.

  At this time, in order to impart flame retardancy to the electromagnetic wave absorption layer 4 and the dielectric layer 3, a predetermined amount of flame retardant and flame retardant aid are blended. As a measure of flame retardancy, it is required to satisfy UL94V0. The flame retardant is not particularly limited, and phosphorus compounds, boron compounds, bromine-based flame retardants, zinc-based flame retardants, nitrogen-based flame retardants, hydroxide-based flame retardants, and the like can be used in appropriate amounts. Examples of phosphorus compounds include phosphate esters and titanium phosphate. Examples of the boron compound include zinc borate. Examples of brominated flame retardants include hexabromobenzene, decabromobenzyl phenyl ether, decabromobenzyl phenyl oxide, tetrabromobisphenol, ammonium bromide and the like. Examples of the zinc-based flame retardant include zinc carbonate, zinc oxide, and zinc borate. Examples of nitrogen-based flame retardants include triazine compounds, hindered amine compounds, or melamine compounds such as melamine cyanurate and melamine anidine compounds. Examples of the hydroxide flame retardant include magnesium hydroxide and aluminum hydroxide. When flame retardancy or nonflammability is imparted, the PET film used for the pattern layer 5 and the conductive reflective layer 2 becomes a problem. Basically, it is difficult to make a PET film flame-retardant, and it is conceivable to cover it with a non-flammable material such as char (carbonized layer). As other methods, a configuration in which only the conductive pattern is transferred to the electromagnetic wave absorbing layer 4 with respect to the pattern layer 5 and the PET film is peeled off, or instead of the PET film for the conductive reflective layer 2 is used. This is achieved by using a layer of glass fiber or glass cloth with metal foil added.

  In the flame retardant compounding carried out in the present invention, the electromagnetic wave absorbing layer 4 has a PVC as a binder of 100 (phr), while calcium carbonate 70 (phr), a flame retardant (Nonsan SAN— 1) Based on 20 (phr), a dispersant, a plasticizer, ferrite, graphite and the like are blended. Further, the dielectric layer 3 contains recycled PVC 100 (phr), calcium carbonate 140 (phr), a flame retardant (Nonsan SAN-1 manufactured by Maruhishi Oil Chemical Co., Ltd.) 10 (phr), and the like as binders. All the layers showed flame retardancy equivalent to UL94 V-0. In addition, the pattern electromagnetic wave absorber created with this composition has passed the flameproof standard as a product.

  The pattern layer 5 and the conductive reflective layer 2 may be a metal such as gold, platinum, silver, nickel, chromium, aluminum, copper, zinc, lead, tungsten, iron, and the like. It may be a resin mixture mixed with carbon black or a film of conductive resin. The said metal etc. may be processed into a board, a sheet, a film, a nonwoven fabric, etc. Or you may have the structure by which the metal layer of film thickness, for example, 600 mm, was formed on the synthetic resin film. What transferred metal foil to base materials, such as a film or cloth, may be used. Further, a conductive ink (for example, resistivity 10Ω / □ or less, 0.5Ω / □ or more) may be applied on the substrate, the electromagnetic wave absorber 4 or the dielectric layer 3.

  The electromagnetic wave absorption characteristics are based on the free space method. In the free space method, a plane wave is irradiated to the electromagnetic wave absorber 1 as a measurement sample placed in free space, and the reflection coefficient and transmission coefficient at that time are measured by changing the frequency, incident angle, and polarization, This is a measurement method for obtaining the complex relative permittivity and the complex relative permeability, and calculating the electromagnetic wave absorption amount (reflection loss) of the electromagnetic wave absorber 1 from the complex relative permittivity and the complex relative permeability thus obtained. . At this time, measurement is performed in a state in which the TE wave, the TM wave, and the sample are rotated by 45 °. The measuring instrument used was a network analyzer (trade name HP8720ES manufactured by Agilent Technologies), and the antenna was a double rigid antenna. The size of each side of the rectangle of the measurement sample that is the electromagnetic wave absorber 1 is 500 × 500 (mm) and 1000 × 1000 (mm).

  The surface layer 6 in FIG. 6 may be placed on the electromagnetic wave absorber 1 that is not only stacked in the order of FIG. 6 but also in other stacking orders. Specific examples of the surface layer 6 include wallpaper, tile carpet, tile, non-combustible board, plywood, decorative board, painted surface, resin board, fabric product, paper, and the like. Basically, any material other than a conductive material having electromagnetic wave shielding properties can be laminated on the outside (outside the pattern layer). If these thicknesses are as thin as 1 mm or less, for example, the electromagnetic wave absorption characteristics are hardly affected, but if they are thick or the complex relative dielectric constant is high, redesign for optimization of the electromagnetic wave absorption characteristics is required. However, if adjusted by this redesign, desired electromagnetic wave absorption characteristics can be exhibited.

  The electromagnetic waves targeted in the present invention are determined depending on the application, and are, for example, electromagnetic waves of at least some frequencies in the 900 MHz band, and more specifically, frequencies including a range of 950 MHz to 956 MHz. Of electromagnetic waves. The frequency of the electromagnetic wave to be blocked is an exemplification, and a configuration for blocking electromagnetic waves having a frequency other than the illustrated frequency is also included in the present invention. The 900 MHz band is a frequency range from 880 MHz to less than 1000 MHz. The material characteristics of each constituent layer change with little difference in these frequency ranges, and the numerical values in the present invention can be used as they are.

  In addition, electromagnetic waves having a frequency in the 2.4 GHz band may be targeted for absorption. The 2.4 GHz band is an electromagnetic wave of 2400 MHz or more and less than 2500 MHz. Specifically, it is an electromagnetic wave having a frequency including a range of 2400 MHz to 2483.5 MHz for RFID.

  As these frequencies, any single frequency or a plurality of frequencies can be selected as long as they are within the UHF band (300 MHz to 3 GHz), the SHF band (3 GHz to 30 GHz), and the EHF band (30 GHz to 300 GHz). That is, the electromagnetic wave to be absorbed includes an electromagnetic wave having a frequency of 300 MHz to 300 GHz.

Finally, the pattern shape, layered configuration, and composition of the patterned wave absorber having absorption characteristics in the 950 MHz band are shown. The pattern shape is the configuration shown in FIG. 3, a1x = a1y = 1.0 mm, a2x = a2y = 17.5 mm, b1x = b1y = 20.5 mm, c2x = c2y = 9.0 mm, c1 = 1.5 mm, radial shape The curvature radius R1 of the substantially triangular portion 22 in the pattern 30 was set to 7.5 mm, and the curvature radius R2 of the corner portion in the substantially rectangular pattern 31 was set to 7.0 mm. The electromagnetic wave absorber layer 4 is blended in PVC (Kaneka Corporation, KS1700) 100 (phr), ferrite (LD-M manufactured by JFE Ferrite Co., Ltd.) 430 (phr), graphite (Nippon Graphite Co., Ltd. Blue P 35 (phr) ) Based on plasticizer, dispersant, calcium carbonate, etc. The structure is a pattern layer (aluminum-deposited PET film), electromagnetic wave absorber layer 4 (2.5 mm), and dielectric layer 3 as plywood (6 0.5 mm) and a conductive reflective layer (aluminum-deposited PET film).
Table 2 shows the electromagnetic wave absorption characteristics of the TE wave and TM wave measured by the free space method.

  FIG. 19 is a graph showing the electromagnetic wave absorption characteristics of TE waves measured by the free space method. FIG. 20 is a graph showing the electromagnetic wave absorption characteristics of TM waves measured by the free space method. In FIG. 19, a solid line 110 indicates an electromagnetic wave absorption characteristic when the incident angle is 10 degrees (°), a broken line 111 indicates an electromagnetic wave absorption characteristic when the incident angle is 30 degrees (°), and a one-dot chain line 112 indicates The electromagnetic wave absorption characteristics when the incident angle is 45 degrees (°) are shown. In FIG. 20, a solid line 120 indicates an electromagnetic wave absorption characteristic when the incident angle is 10 degrees (°), a broken line 121 indicates an electromagnetic wave absorption characteristic when the incident angle is 30 degrees (°), and a one-dot chain line 122 indicates The electromagnetic wave absorption characteristics when the incident angle is 45 degrees (°) are shown. The electromagnetic wave absorber having the above-described configuration exhibits, for example, an electromagnetic wave absorption amount of 20 dB with respect to a TE wave incident at an incident angle of 10 degrees (°), and with respect to a TM wave incident at an incident angle of 10 degrees (°). An electromagnetic wave absorption amount of 25 dB was shown. It was found that there was little anisotropy and high absorption performance was exhibited. As is apparent from FIGS. 19 and 20 and Table 2, the electromagnetic wave absorber 1 that absorbs electromagnetic waves of 950 MHz is selected by appropriately selecting the dimensions of the radial pattern 30 and the substantially rectangular pattern 31 and the material of the electromagnetic wave absorbing layer 4. It is clear that it is obtained.

FIG. 21 is a front view showing a pattern layer 5 constituting an electromagnetic wave absorber 1 according to still another embodiment of the present invention. FIG. 22 is a graph showing the electromagnetic wave absorption characteristics of the electromagnetic wave absorber 1 including the pattern layer 5 shown in FIG. Furthermore, the pattern shape of a pattern electromagnetic wave absorber which has an absorption characteristic in the 950 MHz band which shows thickness reduction, a lamination structure, and a mixing | blending are shown. As shown in FIG. 21, the pattern shape is substantially the same as that shown in FIG. 3. The difference is that the dimensions are different, and the same reference numerals are given to corresponding portions. In the present embodiment, the curvatures of the radial pattern 30 and the substantially rectangular pattern 31 are made different, and the difference is continuously changed in the interval c1 between the two patterns 30 and 31. The conductor pattern dimensions are a1x = a1y = 1.0 mm, a2x = a2y = 20.0 mm, b1x = b1y = 25 mm, c2x = c2y = 7.0 mm, c1 = 0.5 mm to 2.5 mm, radial pattern 30 The radius of curvature R1 of the substantially triangular portion 22 is 6.5 mm, and the radius of curvature R2 of the corner of the substantially rectangular pattern 31 is 10.5 mm. The distance c1 between the radial pattern 30 and the substantially rectangular pattern 31 is continuously changed so that the intermediate portion is larger than both end portions in the direction in which the gap between the patterns 30 and 31 extends.
The composition of the electromagnetic wave absorber layer 4 is based on chlorinated polyethylene (Showa Denko KK, Eraslen 301NA) 100 (phr), carbonyl iron (EW-1 manufactured by BASF) 650 (phr), plasticizer, dispersant, calcium carbonate Etc. are added. The configuration was a laminate of a pattern layer (aluminum-deposited PET film), an electromagnetic wave absorber layer 4 (1.2 mm), a dielectric layer 3 (3.2 mm), and a conductive reflective layer (aluminum-deposited PET film). The material constants of 950 MHz of the electromagnetic wave absorbing layer 4 and the dielectric layer 3 are as shown in Table 3 below. That is, a thin film having a thickness of 4.4 mm (1.2 mm thick as a layer having a magnetic permeability) is realized as an electromagnetic wave absorber in the 950 MHz band. The electromagnetic wave absorption by the simulation is as shown in FIG. In FIG. 22, the electromagnetic wave absorption amount is indicated by a line 200. An absorption amount of 19.5 dB could be obtained in the 925 MHz band.

  As shown in FIG. 21, the distance c1 between the radial pattern 30 and the substantially rectangular pattern 31 that are two adjacent conductive patterns can be different depending on the position. As a result, the amount of electromagnetic wave absorption can be increased compared to the case where the distance c1 between the radial pattern 30 and the substantially rectangular pattern 31 is constant. Therefore, by changing the radius of curvature of the corners of adjacent conductive patterns and continuously changing the interval between the conductive patterns, it is possible to shift the absorption frequency to a low frequency and increase the amount of absorption. Become.

  Table 3 shows the material constants and thicknesses of the electromagnetic wave absorbing layer 4 and the dielectric layer 3 used in the above-described examples. In Table 3, the electromagnetic wave absorbing layer 4 is simply referred to as “absorbing layer”.

  The above-described embodiment is merely an example of the present invention, and the configuration can be changed within the scope of the present invention. The present invention is greatly characterized in that the corners of the conductive pattern are curved, but it is not necessary to form the corners of all the conductive patterns in a curved shape, only for some of the conductive patterns. A shape having curved corners may be used. Further, when forming the angle of the conductive pattern in a curved shape, all the corners may be curved, or only some of the corners may be curved.

  The conductive pattern may have a substantially polygonal planar shape or a closed loop linear shape extending along the outer peripheral edge of the substantially polygonal shape.

  The electromagnetic wave absorbing layer is blended in an amount of 1 part by weight or more and 1500 parts by weight or less of one or more materials selected from the group of ferrite, iron alloy, and iron particles as a magnetic loss material with respect to 100 parts by weight of the organic polymer. It can be set as the structure included in. With such a configuration, it is possible to impart complex relative permeability (μ ′, μ ″) to the loss layer, and to efficiently and energetically attenuate the magnetic field generated around the conductor pattern. Become.

  The real part μ ′ of the complex relative permittivity of the dielectric layer may be in the range of 1 to 50. With such a configuration, the dielectric constant of the dielectric layer and the electromagnetic wave absorber can be arbitrarily controlled, which can contribute to the reduction in the size of the conductive pattern and the reduction in the thickness of the electromagnetic wave absorber.

  Further, the electromagnetic wave absorber for absorbing the 2.4 GHz band electromagnetic wave may have a total thickness of 4 mm or less. With such a configuration, the conductive pattern can function as a resonant antenna for electromagnetic waves in the 2.4 GHz band. Therefore, the electromagnetic wave absorption efficiency in the electromagnetic wave absorber can be increased, and the electromagnetic wave absorber can be thinned.

  Further, the electromagnetic wave absorber for absorbing electromagnetic waves in the 900 MHz band can have a total thickness of 10 mm or less. With such a configuration, the conductive pattern can function as a resonant antenna with respect to a 900 MHz band radio wave. Therefore, the electromagnetic wave absorption efficiency in the electromagnetic wave absorber can be increased, and the electromagnetic wave absorber can be thinned.

The following embodiments are possible for the present invention.
(1) A pattern layer formed by arranging a plurality of conductive patterns having one or more kinds of conductive patterns having a substantially polygonal outer shape in which at least one corner is curved;
A loss layer made of a material that is at least one of a magnetic loss material having a complex relative permeability (μ ′, μ ″) and a dielectric loss material having a complex relative permittivity (ε ′, ε ″); An electromagnetic wave absorber characterized by comprising.

  An electromagnetic wave absorber having excellent electromagnetic wave absorption characteristics can be realized. The reason will be described in detail below.

  The mechanism of thickness reduction in the electromagnetic wave absorber using a conductive pattern will be described below. First, an electromagnetic wave having a specific frequency is received by the conductive pattern of the pattern layer according to the resonance principle of the antenna. Here, the specific frequency is a frequency determined by specifications such as the shape and dimensions of the conductive pattern, and is a frequency to be absorbed by the electromagnetic wave absorber. When the electromagnetic wave is received by the conductive pattern, a resonance current flows through the end portion of the conductive pattern. When this current flows, a magnetic flux is generated around the current. The magnetic flux increases as it is closer to the current source, and is distributed with a high magnetic flux density. When a loss layer having a magnetic loss material is provided in the vicinity of the pattern layer, magnetic field energy can be lost. Thus, the energy of electromagnetic waves can be changed to heat energy and absorbed.

  In addition, an electromagnetic wave absorber is used by attaching it to an object whose surface is made of a conductive material, or a conductive reflective layer is further provided on the opposite side of the pattern layer from the loss layer. By using in a laminated state through a loss layer, a capacitor can be formed between the conductive pattern of the pattern layer and the conductive layer (the surface layer of the object made of a conductive material or the conductive reflective layer). it can. When the distance between the conductive pattern and the conductive layer is shortened, the capacitance of the capacitor can be increased. Capacitors can also be formed between the patterns. As described above, the pattern electromagnetic wave absorber can be thinned by providing a reactance adjustment function by using a capacitor.

  Furthermore, the conductive pattern for receiving electromagnetic waves has a substantially polygonal outer shape that is basically a polygon, and the peak value of the electromagnetic wave absorption is compared with the case where the outer shape of the conductive pattern is circular. The peak value of electromagnetic wave absorption can be increased.

  This is because in the case of a polygon pattern, the Q value is higher than that of a circular pattern. First, the Q value will be described. The resonance Q value can be expressed by a bandwidth. The relationship between the two is Q = resonance frequency / bandwidth. Therefore, a high Q value means a narrow bandwidth.

  This relationship is expressed by applying the peak value of the electromagnetic wave absorption amount of the electromagnetic wave absorber using the pattern. In other words, a high Q value of the polygonal pattern means that it has a high electromagnetic wave reflection attenuation amount (peak value of the electromagnetic wave absorption amount) although it is a narrow band, and a low Q value means an electromagnetic wave reflection attenuation that shows a wide absorption band. The amount (peak value of electromagnetic wave absorption amount) is low.

  If the polygon pattern has a high Q value, the absorption band is narrowed, and the resonance frequency shifts due to the influence of polarization. This is because when a square (rectangular) pattern is subjected to an electric field of 0 ° (with no polarization), a strong current flows along the sides of the square pattern and resonance occurs in that part, whereas the electric field is applied to the square pattern. In the case of 45 ° inclination or in the case of a circular pattern, this can be explained by the phenomenon that a path through which a strong current flows becomes narrower and less concentrated on the edge as the square pattern becomes 0 °. In other words, it can be said that by expanding the current path, the region where the half-wave wave related to resonance is distributed is expanded and the conditions for resonance increase. As a result, we believe that we can earn bandwidth. For example, in the case of a square pattern, when an electromagnetic wave (TE wave) is received, an electric field is generated in parallel with the side, but when the square is rotated by 45 °, the electric field in the pattern when receiving the electromagnetic wave (TE wave) is Since it occurs like drawing an arc, the distribution is clearly different. That is, the square (polygonal) pattern has a drawback that it easily develops polarization dependency although the electromagnetic wave absorption characteristic is improved as a result of concentrated resonance.

  In order to improve this defect, the pattern shape is basically a polygon, but at least one corner is formed in a curved shape. Here, the effect of imparting R to the corner, that is, the curved surface, is that the resonance current easily flows without stagnation at the corner, and further, the resonating region is widened. As a result, the Q value is slightly The polarization characteristics are improved by showing wideband performance although it falls. Accordingly, it is possible to suppress a shift in frequency at which the absorption amount reaches a peak depending on the polarization direction of the electromagnetic wave. Therefore, it is possible to realize an electromagnetic wave absorber having an excellent electromagnetic wave absorption characteristic in which the peak value of the electromagnetic wave absorption amount is high and the frequency shift at which the absorption amount peaks depending on the polarization direction of the electromagnetic wave is small.

  The conductive pattern may have a substantially polygonal planar shape or a closed loop linear shape extending along the outer peripheral edge of the substantially polygonal shape.

  It is basically a polygon, and by making at least some corners curved, the peak value of the electromagnetic wave absorption amount is high, and the frequency shift at which the absorption amount peaks due to the polarization direction of the electromagnetic wave is small. An electromagnetic wave absorber having excellent electromagnetic wave absorption characteristics can be realized.

  (2) An electromagnetic wave characterized in that a dimension of a curved portion at the corner is determined to be a small dimension within a range of dimensions capable of suppressing a shift in frequency that can be absorbed due to a difference in polarization direction. Absorber.

  A portion formed in a curved shape at the corner can be made as small as possible. As a result, the peak value of the electromagnetic wave absorption amount can be made as high as possible after suppressing the shift of the frequency at which the absorption amount peaks depending on the polarization direction of the electromagnetic wave. That is, when the radius of curvature R of the corner curve increases, the pattern shape approaches a circle and finally becomes a circle. Accordingly, the Q value decreases and the electromagnetic wave absorption characteristics tend to decrease, but the polarization characteristics improve. In the present invention, the pattern shape is such that the radius of curvature R is optimized so as to improve electromagnetic wave absorption characteristics but improve polarization characteristics. Therefore, an electromagnetic wave absorber having extremely excellent electromagnetic wave absorption characteristics can be realized.

  The peak value of the electromagnetic wave absorption amount can be made as high as possible after suppressing the shift of the frequency at which the absorption amount reaches the peak depending on the polarization direction of the electromagnetic wave.

(3) The electromagnetic wave absorber, wherein the conductive pattern is a planar pattern.
By using the electromagnetic wave absorber attached to an object made of a conductive material on the surface or using a conductive reflective layer, the pattern layer is used in a state where it is laminated on the conductive layer, A capacitor can be constituted by the conductive pattern of the pattern layer and the conductive layer. Furthermore, since it is a planar pattern, the capacity of the capacitor can be increased. The planar conductive pattern can easily form a capacitor having a large capacity, and can effectively utilize a reactance adjustment function that is effective in reducing the thickness of the electromagnetic wave absorber using the conductive pattern.

  The electromagnetic wave receiving efficiency by the conductive wire pattern can be increased, and the electromagnetic wave absorption amount in the electromagnetic wave absorber can be increased.

  (4) An electromagnetic wave absorber that can absorb electromagnetic waves of two or more frequencies by a combination of conductive patterns.

  The conductive pattern functions as a resonant antenna for electromagnetic waves having a specific frequency. In the case of a planar pattern, the outer peripheral length is designed to correspond to a wavelength of a specific frequency. Then, when a plurality of types whose pattern sizes correspond to two or more electromagnetic wave frequencies are arranged, a bimodal electromagnetic wave absorber that absorbs electromagnetic waves of two or more frequencies can be realized. Also in this case, not only the high absorption characteristic but also the polarization characteristic can be improved by providing a curved shape at the corner of the pattern shape.

  The combination of pattern shapes enables reception of electromagnetic waves having a plurality of frequencies, and absorption of two or more electromagnetic waves can be achieved.

  (5) The electromagnetic wave absorber, wherein the conductive pattern has one or a plurality of holes, and the holes resonate with an electromagnetic wave having a frequency to be absorbed.

  For example, a hole can be provided inside the planar pattern, and the hole itself can also function as a receiving antenna. That is, a slot pattern (slot antenna) can be provided inside a planar pattern that is a resonant patch antenna. Thereby, an electromagnetic wave absorber having a bimodal characteristic that absorbs electromagnetic waves of two frequencies can be obtained. Further, by repeatedly providing a planar pattern inside the slot pattern, it can be used as a resonant antenna to respond to electromagnetic waves of different frequencies, and theoretically absorbs electromagnetic waves of three frequencies. Can be obtained. Also in this case, not only the high absorption characteristic but also the polarization characteristic can be improved by providing a curved shape at the corner of the pattern shape. By repeating this operation, it becomes possible to absorb electromagnetic waves of a larger number (four or more) of frequencies.

  By forming a hole portion in the conductive pattern, it is possible to receive electromagnetic waves of a plurality of frequencies and absorb two or more electromagnetic waves.

(6) The loss layer is
An electromagnetic wave absorbing layer made of a material that is at least one of a magnetic loss material and a dielectric loss material;
An electromagnetic wave absorber comprising a dielectric layer made of a dielectric material.

The absorption of electromagnetic waves in the loss layer can be improved. Therefore, the electromagnetic wave absorption efficiency in the electromagnetic wave absorber can be increased, and the electromagnetic wave absorber can be thinned.
The absorption of electromagnetic waves in the loss layer can be improved, and the amount of electromagnetic waves absorbed can be increased.

(7) The electromagnetic wave absorber, wherein the electromagnetic wave absorbing layer and the dielectric layer each have a surface resistivity of 10 ⁶ Ω / □ or more.

The surface resistivity (according to JIS K6911) of the electromagnetic wave absorbing layer and the dielectric layer is sufficiently higher than a level (10 ⁻⁴ to 10 ¹ Ω / □) which is said to be conductive, and these layers have so-called electromagnetic shielding properties. There is nothing. As a result, an electromagnetic wave having a specific frequency can be taken into the interior with high efficiency and converted into heat energy.
It can absorb suitably, without reflecting electromagnetic waves.

  (8) An electromagnetic wave absorber in which at least one of the electromagnetic wave absorption layer and the dielectric layer is laminated in a plurality of layers.

It is assumed that the electromagnetic wave absorbing layer and the dielectric layer are configured as a laminate, and that the electromagnetic wave absorbing layer and the dielectric layer are alternately stacked. For example, when using an incombustible board, a thermosetting resin, a thin sheet of flame retardant paper or plywood as the dielectric layer, and an adhesive layer containing a magnetic loss material in an adhesive resin as the electromagnetic wave absorbing layer, the adhesive layer If thick coating is required to obtain the required thickness, dedicated equipment will be required, leading to an increase in cost. Even if the thin coating is made multilayer, the effect as an electromagnetic wave absorbing layer can be obtained. Therefore, if an alternate lamination in which thin coating is applied and the number of laminations is increased with existing equipment is adopted, new dedicated equipment becomes unnecessary.
By making each layer thinner and thinner, it can be manufactured at low cost using existing equipment.

  (9) An electromagnetic wave absorber, wherein the conductive reflective layer is laminated on the side opposite to the pattern layer with respect to the loss layer.

There are fewer restrictions on the place where the electromagnetic wave absorber is mounted. For example, the electromagnetic wave can be absorbed by being mounted on an object made of a non-conductive material. Therefore, convenience is improved.
A highly convenient electromagnetic wave absorber can be obtained.

(10) An electromagnetic wave absorption method using the above-described electromagnetic wave absorber.
By using an excellent electromagnetic wave absorber as described above, electromagnetic waves can be suitably absorbed.

As a specific application of the above-mentioned electromagnetic wave absorber, as a flooring material, a wall material, a ceiling material formed in an electromagnetic wave environment space such as an office, or as a coating material on a metal surface of furniture or office equipment, or as a partition, The electromagnetic wave environment is improved by arranging the electromagnetic wave absorber according to the present invention. Specifically, prevention of malfunction of electronic devices (medical devices) due to self-wave interference and other-wave interference, human body protection, wireless LAN (2.4 GHz band, 4.9 GHz band, 5.2 GHz band, etc.) and DSRC, ETC This is a countermeasure for transmission delay such as (5.8 GHz) and a countermeasure for maintaining the electromagnetic wave communication environment. It can also be used to improve the electromagnetic wave communication environment for wireless communication between ITS-related moving objects that use millimeter wave band electromagnetic waves. The electromagnetic wave environment can be used not only in offices but also in homes, hospitals, concert halls, factories, research facilities, station buildings, exhibition halls, outdoor facilities such as roadside walls, and the like. It can be used for each required location in walls, floors, ceilings, columns, panels, billboards, steel products, etc. in environments that can be assumed.
As described above, the electromagnetic wave can be suitably absorbed by using an excellent electromagnetic wave absorber.

It is a front view which shows the pattern P in order to demonstrate the direction which the electric field generate | occur | produces at the time of electromagnetic wave irradiation by the angle of a square pattern. It is sectional drawing of the electromagnetic wave absorber 1 of one Embodiment of this invention. It is a front view which shows the pattern layer 5 which comprises the electromagnetic wave absorber 1 of one Embodiment of this invention shown by FIG. FIG. 4 is an enlarged front view of a part of a pattern layer 5 in the embodiment shown in FIGS. 2 and 3. It is sectional drawing of the electromagnetic wave absorber 1 of the other form of implementation of this invention. It is sectional drawing of the electromagnetic wave absorber 1 of further another form of implementation of this invention. It is a front view which shows the pattern layer 5 which comprises the electromagnetic wave absorber 1 of further another form of implementation of this invention. It is a front view which shows the pattern layer 5 which comprises the electromagnetic wave absorber 1 of further another form of implementation of this invention. It is a front view which shows the substantially square pattern 41 of further another form of implementation of this invention. It is a front view which shows the radial pattern 40 of further another form of implementation of this invention. It is a graph which shows the simulation result of the absorption characteristic of electromagnetic waves. It is the graph (simulation result) which shows that the absorption characteristic improved by R provision, and that an absorption frequency shifts to a high frequency. It is the graph which compared the simulation result and measured value of the absorption characteristic of a 2.45 GHz band. It is a graph which shows the simulation result whose absorption frequency is two. It is a front view which shows a part of arrangement | sequence of the electroconductive pattern which shows the electromagnetic wave absorption characteristic of FIG. 14, specifically, the substantially rectangular pattern 31. FIG. It is a graph which shows the simulation result from which electromagnetic wave absorption characteristics change with the combination of the substantially square pattern 31 from which a curvature radius R differs. It is a graph which shows the simulation result whose absorption frequency is three. FIG. 18 is a front view showing a part of the arrangement of the conductive pattern showing the electromagnetic wave absorption characteristics of FIG. 17, specifically, the substantially rectangular pattern 31. It is a graph of the electromagnetic wave absorption characteristic of the TE wave of the electromagnetic wave absorber which has an absorption peak in 900 MHz band as an Example of this invention. It is a graph of the electromagnetic wave absorption characteristic of TM wave of the electromagnetic wave absorber which has an absorption peak in 900 MHz band as an Example of this invention.

It is a front view which shows the pattern layer 5 which comprises the electromagnetic wave absorber 1 of further another form of implementation of this invention. It is a graph which shows the simulation result of the electromagnetic wave absorber which has an absorption peak in 900 MHz band as an Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electromagnetic wave absorber 2 Conductive reflection layer 3 Dielectric layer 4 Electromagnetic wave absorption layer 5 Pattern layer 11 Base material 12 Conductive pattern 30, 40 Radial pattern 31, 41 Substantially square pattern

Claims (11)

A plurality of conductive patterns including one or a plurality of types of conductive patterns having a substantially polygonal outline shape in which at least one corner is curved, and a pattern layer formed in a manner in which the conductive patterns are not connected to each other;
A loss layer having a portion made of a material that is at least one of a magnetic loss material having a complex relative permeability (μ ′, μ ″) and a dielectric loss material having a complex relative permittivity (ε ′, ε ″);
Constructed by laminating a conductive reflective layer located on the opposite side of the pattern layer with respect to the loss layer,
The dielectric loss material is formed by adding a material selected from the group of graphite, carbon black, carbon fiber, graphite fiber, metal powder, metal fiber to an organic polymer,
The pattern layer is provided so as to be close to the loss layer, and a ratio R / L between a substantially polygonal side length L and a curvature radius R of the curved corner is 0.1 to 0.46 . And an electromagnetic wave absorber formed such that R is 2 to 11.5 mm .   2. The electromagnetic wave absorber according to claim 1, wherein the outer shape is a shape formed by a combination of a straight line and a curved line.   3. The electromagnetic wave absorber according to claim 1, wherein the substantially polygonal shape has a shape in which four corners of a square are formed in an arc shape. 4.   The electromagnetic wave absorber according to claim 1, wherein the conductive pattern is a planar pattern.   The electromagnetic wave absorber according to claim 1, wherein conductive patterns having different outer peripheral lengths are formed in combination.   The electromagnetic wave absorber according to any one of claims 1 to 5, wherein conductive patterns having different curvature radii at corners are formed in combination.   The electromagnetic wave absorber according to any one of claims 1 to 6, wherein an interval between two adjacent conductive patterns varies depending on a position.   The conductive pattern has one or a plurality of hole portions, and the hole portions have dimensions that resonate with electromagnetic waves having a frequency to be absorbed. Electromagnetic wave absorber as described in one. The loss layer is
An electromagnetic wave absorbing layer made of a magnetic loss material or al,
The electromagnetic wave absorber according to claim 1, further comprising a dielectric layer made of a dielectric material. 10. The electromagnetic wave absorber according to claim 9, wherein the real part μ ′ of the complex relative permittivity of the dielectric layer is in the range of 1 to 50 . The electromagnetic wave absorption method by using the electromagnetic wave absorber as described in any one of Claims 1-10 .

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