Radio wave reflection plate

Abstract

Provided is a radio wave reflection plate including: a patch electrode on a first substrate; a ground electrode on a second substrate different from the first substrate; a liquid crystal layer between the patch electrode and the ground electrode; and a first region in which the ground electrode overlaps with the patch electrode and a second region in which the ground electrode does not overlap with the patch electrode in a plan view. In the first region, the patch electrode includes a plurality of first openings having a first opening area, and the ground electrode includes a plurality of second openings having a second opening area. In the second region, the ground electrode includes a plurality of third openings having a third opening area. The plurality of second openings overlap with the plurality of first openings, and the second opening area is greater than the first opening area.

Description

radio wave reflector

[0001] An embodiment of the present invention relates to a radio wave reflector that can control the reflection direction of incident radio waves.

[0002] A phased array antenna device (hereinafter sometimes referred to as a "radio wave reflector") controls the directivity of a fixed antenna by adjusting the amplitude and phase of a high-frequency signal applied to each of a plurality of antenna elements arranged in a plane. The phased array antenna device requires a phase shifter. A phased array antenna device using a phase shifter that utilizes a change in the dielectric constant due to the orientation state of liquid crystals has been disclosed (see, for example, Patent Document 1).

[0003] The antenna elements of the phased array antenna device in Patent Document 1 include multiple strip lines, a planar electrode facing the multiple strip lines, and a liquid crystal layer disposed between the multiple strip lines and the planar electrode. Different voltages are applied to the multiple strip lines in the multiple antenna elements. The dielectric constant of the liquid crystal layer for each antenna element is then adjusted to superimpose the reflected waves, thereby changing the phase. This allows the reflection direction of the radio wave to be set to any desired direction.

[0004] Japanese Patent Application Publication No. 11-103201

[0005] Radio wave reflectors can simplify radio wave base stations. However, because the installation of radio wave reflectors can cause visual disturbance, transparent radio wave reflectors are desired for use in the fifth-generation mobile communication system (G5). Radio wave reflectors using liquid crystals can be made transparent. However, even transparent radio wave reflectors using liquid crystals have problems with in-plane transparency variations, such as the shape of the electrodes included in the radio wave reflector being visible. Therefore, there is a need to improve the in-plane transparency variations of transparent radio wave reflectors.

[0006] In view of the above-mentioned problems, one object of one embodiment of the present invention is to provide a transparent radio wave reflector in which in-plane variations in transparency are suppressed.

[0007] A radio wave reflector according to one embodiment of the present invention includes a patch electrode on a first substrate, a ground electrode on a second substrate different from the first substrate, a liquid crystal layer between the patch electrode and the ground electrode, and a first region in which the ground electrode overlaps with the patch electrode in a planar view and a second region in which the ground electrode does not overlap with the patch electrode, wherein in the first region, the patch electrode includes a plurality of first openings having a first opening area, and the ground electrode includes a plurality of second openings having a second opening area, and in the second region, the ground electrode includes a plurality of third openings having a third opening area, the plurality of second openings overlap with the plurality of first openings, and the second opening area is larger than the first opening area.

[0008] FIG. 1 is a schematic plan view showing an overview of the configuration of a radio wave reflector according to one embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing the configuration of a reflecting antenna cell of a radio wave reflector according to one embodiment of the present invention and the direction in which radio waves are reflected by the reflecting antenna cell. FIG. 3 is a schematic plan view showing the configuration of a patch electrode and a ground electrode of a radio wave reflector according to one embodiment of the present invention. FIG. 4 is a schematic plan view showing an electrode pattern of a patch electrode of a radio wave reflector according to one embodiment of the present invention. FIG. 5 is a schematic cross-sectional view showing the configuration of a first region of a radio wave reflector according to one embodiment of the present invention. FIG. 6 is a schematic plan view showing the configuration of a patch electrode and a ground electrode of a radio wave reflector according to one embodiment of the present invention. FIG. 7 is a schematic cross-sectional view showing the configuration of a first region of a radio wave reflector according to one embodiment of the present invention. FIG. 8 is a schematic plan view showing the electrode pattern of a patch electrode of a radio wave reflector according to one embodiment of the present invention. FIG. 1 is a schematic plan view showing the configuration of a patch electrode and a ground electrode of a radio wave reflector according to one embodiment of the present invention. FIG. 2 is a schematic plan view showing the electrode pattern of the ground electrode of a radio wave reflector according to one embodiment of the present invention. FIG. 3 is a schematic plan view showing the configuration of a patch electrode and a ground electrode of a radio wave reflector according to one embodiment of the present invention. FIG. 4 is a schematic plan view showing the electrode pattern of the patch electrode of a radio wave reflector according to one embodiment of the present invention. FIG. 5 is a schematic plan view showing the electrode pattern of the ground electrode of a radio wave reflector according to one embodiment of the present invention. FIG. 6 is a schematic plan view showing the configuration of the patch electrode and the ground electrode of a radio wave reflector according to one embodiment of the present invention.

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention can be implemented in many different forms, and should not be construed as being limited to the description of the following exemplary embodiments. For clarity of explanation, the drawings may show schematic representations of the width, thickness, shape, etc. of each part compared to the actual form. However, these are merely examples and are not intended to limit the interpretation of the present invention. Furthermore, in this specification and drawings, components similar to those described above with reference to the previous figures may be designated by the same reference numerals, and detailed descriptions may be omitted as appropriate. Furthermore, the letters "first" and "second" attached to components are convenient labels used to distinguish between components and have no further meaning unless otherwise specified.

[0010] In this specification, when a member or region is referred to as being "on (or under)" another member or region, unless otherwise specified, this includes not only the case where it is directly above (or directly under) the other member or region, but also the case where it is above (or under) the other member or region, i.e., the case where another component is included between the member or region and above (or under) the other member or region.

[0011] A radio wave reflector 10 according to one embodiment of the present invention will be described with reference to FIGS.

[0012] 1. Configuration of Radio Wave Reflector 10 FIG. 1 is a schematic plan view showing an outline of the configuration of a radio wave reflector 10 according to one embodiment of the present invention.

[0013] As shown in FIG. 1 , the radio wave reflector 10 includes a reflecting antenna region 11 and a driving circuit region 12. The reflecting antenna region 11 is provided in the center of the radio wave reflector 10, and the driving circuit region 12 is provided in the peripheral region of the radio wave reflector 10. In other words, the driving circuit region 12 is provided around the reflecting antenna region 11. The reflecting antenna region 11 is provided with a plurality of reflecting antenna cells 100. The reflecting antenna cells 100 are arranged in a matrix in the x-axis direction and the y-axis direction. However, the arrangement of the reflecting antenna cells 100 is not limited to this. The driving circuit region 12 is provided with a driving circuit that generates control signals to control each of the reflecting antenna cells 100. Although not shown, terminals for supplying signals or power from an external source may be provided in the peripheral region of the radio wave reflector 10.

[0014] Now, the configuration and function of the reflecting antenna cell 100 will be described with reference to FIG.

[0015] Fig. 2 is a schematic cross-sectional view showing the configuration of a reflecting antenna cell 100 of a radio wave reflector 10 according to one embodiment of the present invention and the direction in which radio waves are reflected by the reflecting antenna cell 100. Fig. 2 shows two adjacent reflecting antenna cells 100, namely, a first reflecting antenna cell 100-1 and a second reflecting antenna cell 100-2.

[0016] Each of the first reflecting antenna cell 100-1 and the second reflecting antenna cell 100-2 includes a patch electrode 120 provided on the first substrate 110-1 and a ground electrode 130 provided on the second substrate 110-2. The patch electrode 120 of the first reflecting antenna cell 100-1 and the patch electrode 120 of the second reflecting antenna cell 100-2 are not electrically connected. On the other hand, the ground electrode 130 is provided in common to the first reflecting antenna cell 100-1 and the second reflecting antenna cell 100-2. A first alignment film 140-1 is provided on the patch electrode 120. A second alignment film 140-2 is provided on the ground electrode 130. The first substrate 110-1 and the second substrate 110-2 are arranged so that the patch electrode 120 and the ground electrode 130 face each other, and a liquid crystal layer 150 is provided between the first alignment film 140-1 and the second alignment film 140-2.

[0017] Each of the first substrate 110-1 and the second substrate 110-2 can be made of glass, quartz, resin, or the like.

[0018] A metal material can be used for each of the patch electrode 120 and the ground electrode 130. For example, the metal material is molybdenum (Mo), tungsten (W), titanium (Ti), aluminum (Al), copper (Cu), or an alloy thereof. Each of the patch electrode 120 and the ground electrode 130 may have a single-layer structure or a multilayer structure.

[0019] Each of the first alignment film 140-1 and the second alignment film 140-2 can be made of a polyimide resin, etc. The first alignment film 140-1 and the second alignment film 140-2 have been subjected to alignment treatment using a rubbing method, a photo-alignment method, or the like.

[0020] The liquid crystal layer 150 includes a liquid crystal material having dielectric anisotropy. For example, a nematic liquid crystal or a cholesteric liquid crystal containing liquid crystal molecules capable of twist alignment can be used as the liquid crystal material of the liquid crystal layer 150. Furthermore, the liquid crystal layer 150 preferably includes a chiral agent to stabilize the twist alignment of the liquid crystal molecules.

[0021] The initial alignment state (alignment state when no voltage is applied) of the liquid crystal molecules in the liquid crystal layer 150 is controlled by the first alignment film 140-1 and the second alignment film 140-2 that have been subjected to alignment treatment. When a voltage is applied to the patch electrode 120 and a potential difference is formed between the patch electrode 120 and the ground electrode 130, the alignment state of the liquid crystal molecules in the liquid crystal layer 150 changes, and the dielectric constant of the liquid crystal layer 150 also changes. As will be described in detail later, the radio wave reflector 10 uses the change in the dielectric constant of the liquid crystal layer 150 to control the phase of the reflected radio waves.

[0022] When liquid crystal molecules have positive dielectric anisotropy, the dielectric constant of the liquid crystal becomes larger when a voltage is applied than when no voltage is applied. Furthermore, when liquid crystal molecules have negative dielectric anisotropy, the dielectric constant of the liquid crystal becomes smaller when a voltage is applied than when no voltage is applied. The liquid crystal layer 150 formed of liquid crystals with dielectric anisotropy can also be considered a variable dielectric layer. By utilizing the dielectric anisotropy of the liquid crystal layer 150, the reflecting antenna cell 100 can control the phase delay (or non-delay) of radio waves scattered by the ground electrode 130.

[0023] As described above, the first reflecting antenna cell 100-1 and the second reflecting antenna cell 100-2 have the same basic configuration. That is, each of the plurality of reflecting antenna cells 100 has the above-described basic configuration. Meanwhile, each of the plurality of reflecting antenna cells 100 is electrically connected to a switching element 160. Specifically, the switching element 160 is electrically connected to the patch electrode 120, and by controlling the switching element 160, the voltage applied to the patch electrode 120 changes.

[0024] As shown in Figure 2, radio waves are incident on the radio wave reflector 10 in a direction parallel to the normal to the surface of the first substrate 110-1 (see "Propagation direction of incident wave" in Figure 2). Here, consider a case where a first voltage V1 is applied to the patch electrode 120 of the first reflecting antenna cell 100-1, and a second voltage V2 different from the first voltage V1 is applied to the patch electrode 120 of the second reflecting antenna cell 100-2. When radio waves having the same phase are incident on the first reflecting antenna cell 100-1 and the second reflecting antenna cell 100-2, scattered waves with different phases are generated in the first reflecting antenna cell 100-1 and the second reflecting antenna cell 100-2 because the dielectric constants of the liquid crystal layers 150 are different between the first reflecting antenna cell 100-1 and the second reflecting antenna cell 100-2. For example, as shown in Figure 2, the phase of the scattered wave R2 scattered by the second reflecting antenna cell 100-2 leads the phase of the scattered wave R1 scattered by the first reflecting antenna cell 100-1. In this case, the radio wave reflected by the reflecting antenna area 11 travels in a direction different from the normal direction to the surface of the first substrate 110-1 (see "Direction of travel of reflected wave" in Figure 2). Although Figure 2 shows two adjacent reflecting antenna cells 100, the radio wave reflector 10 can separately control multiple reflecting antenna cells 100 arranged in a matrix. Therefore, the radio wave reflector 10 can control the reflection direction of the radio wave in any direction.

[0025] The frequency bands to which the radio wave reflector 10 is applicable are the very high frequency (VHF) band, the ultra high frequency (UHF) band, the super high frequency (SHF) band, the submillimeter wave (THF) band, and the extra high frequency (EHF) band. As described above, in the liquid crystal layer 150, the orientation state of the liquid crystal molecules changes depending on the voltage applied to the patch electrode 120, but does not substantially follow the frequency of the radio wave incident on the ground electrode 130. Due to such characteristics of the liquid crystal molecules, the dielectric constant of the liquid crystal layer 150 can be changed by the patch electrode 120, and the ground electrode 130 can scatter the radio waves and control the phase of the scattered radio waves.

[0026] 2. Configuration of the Patch Electrode 120 and the Ground Electrode 130 Fig. 3 is a schematic plan view showing the configuration of the patch electrode 120 and the ground electrode 130 of the radio wave reflector 10 according to one embodiment of the present invention. Specifically, Fig. 3 is a partial enlarged view of an area A including four reflecting antenna cells 100 in Fig. 1. Fig. 4A is a schematic plan view showing the electrode pattern of the patch electrode 120 of the radio wave reflector 10 according to one embodiment of the present invention, and Fig. 4B is a schematic plan view showing the electrode pattern of the ground electrode 130 of the radio wave reflector 10 according to one embodiment of the present invention. The plan views of Figs. 4A and 4B correspond to the plan view of Fig. 3.

[0027] The radio wave reflector 10 includes a first region 101 and a second region 102. The first region 101 is a region where the patch electrode 120 and the ground electrode 130 overlap in a planar view. That is, the first region 101 is a region corresponding to the reflecting antenna cell 100. The second region 102 is a region where the patch electrode 120 and the ground electrode 130 do not overlap in a planar view. That is, the second region 102 is a region where only the ground electrode 130 is provided.

[0028] In the first region 101, the patch electrode 120 includes a plurality of first openings 121 having a first opening area (see FIG. 4A ). In the first region 101, the ground electrode 130 includes a plurality of second openings 131 having a second opening area (see FIG. 4B ). The cross-sectional shape of each of the first openings 121 and the second openings 131 is rectangular, but is not limited to this. The second opening area is larger than the first opening area. The first openings 121 and the second openings 131 overlap each other. Specifically, one of the plurality of second openings 131 overlaps four of the plurality of first openings 121.

[0029] In the second region 102, the ground electrode 130 includes a plurality of third openings 132 having a third opening area (see FIG. 4B ). The cross-sectional shape of the third openings is rectangular, but is not limited thereto. The third opening area is the same as the first opening area. In other words, the opening ratio of the ground electrode 130 in the second region 102 is smaller than the opening ratio of the ground electrode 130 in the first region 101.

[0030] The patch electrode 120 and the ground electrode 130 do not transmit light. However, in the radio wave reflector 10, many openings (plurality of first openings 121, pluralities of second openings 131, and pluralities of third openings 132) are provided in the patch electrode 120 and the ground electrode 130 to allow light to pass through, and light incident on the radio wave reflector 10 passes through the openings. Therefore, the radio wave reflector 10 is a transparent radio wave reflector.

[0031] Here, with reference to FIGS. 5 and 6, the configuration of the patch electrode 120 and the ground electrode 130 in the first region 101 of the radio wave reflector 10, which is a transparent radio wave reflector, will be described in more detail.

[0032] Fig. 5 is a schematic plan view showing the configuration of the first region 101 of the radio wave reflector 10 according to one embodiment of the present invention. Fig. 6 is a schematic cross-sectional view showing the configuration of the first region 101 of the radio wave reflector 10 according to one embodiment of the present invention. Specifically, Fig. 6 is a cross-sectional view of the first region 101 taken along line B1-B2 in Fig. 5. As described above, the first region 101 corresponds to the reflecting antenna cell 100.

[0033] 5 and 6 show a transistor as an example of the switching element 160. That is, the switching element 160 includes a semiconductor layer 161, a gate insulating layer 162, and a gate electrode 163. The semiconductor layer 161 is provided on the first substrate 110-1. The gate insulating layer 162 is provided on the first substrate 110-1 so as to cover the semiconductor layer 161. The gate electrode 163 is provided on the gate insulating layer 162 so as to overlap the semiconductor layer 161. The gate electrode 163 is electrically connected to a selection signal line 166. An interlayer insulating layer 164 is provided on the gate electrode 163. Two openings are formed in the interlayer insulating layer 164, through which the semiconductor layer 161 is exposed. The semiconductor layer 161 is electrically connected to the patch electrode 120 through one opening and to the data signal line 167 through the other opening. A planarization layer 165 is provided on the interlayer insulating layer 164 and the data signal line 167. The patch electrode 120 is provided on the planarization layer 165 .

[0034] The semiconductor layer 161 is formed using a silicon semiconductor such as amorphous silicon or polycrystalline silicon, or an oxide semiconductor such as indium gallium zinc oxide, indium gallium aluminum oxide, indium gallium oxide, zinc oxide, or gallium oxide. The gate insulating layer 162 and the interlayer insulating layer 164 are formed using, for example, a silicon oxide film or a stacked structure of a silicon oxide film and a silicon nitride film. The gate electrode 163 and the selection signal line 166 may be formed in the same layer. The gate electrode 163 and the selection signal line 166 are formed using, for example, molybdenum (Mo), tungsten (W), or an alloy thereof. The data signal line 167 is formed using a metal material such as titanium (Ti), aluminum (Al), or molybdenum (Mo). For example, the data signal line 167 is formed using a stacked structure of titanium (Ti), aluminum (Al), and titanium (Ti), or a stacked structure of molybdenum (Mo), aluminum (Al), and molybdenum (Mo). The planarizing layer 165 is formed using a resin material such as acrylic or polyimide.

[0035] The selection signal line 166 and the data signal line 167 are electrically connected to the drive circuit in the drive circuit region 12. A control signal from the drive circuit is input to the switching element 160 via the selection signal line 166 and the data signal line 167. The switching element 160 operates based on the control signal, thereby changing the alignment state of the liquid crystal molecules in the liquid crystal layer 150.

[0036] The transparency of the radio wave reflector 10 is related to the light transmittance of the radio wave reflector 10. For example, as the amount of light passing through the radio wave reflector 10 increases, the transparency of the radio wave reflector 10 improves. Light incident on the radio wave reflector 10 is mainly blocked by the patch electrode 120 and the ground electrode 130. Only the ground electrode 130 is provided in the second region 102. On the other hand, the patch electrode 120 and the ground electrode 130 are provided in the first region 101. Therefore, light incident on the radio wave reflector 10 is more likely to be blocked in the first region 101 than in the second region 102. Therefore, generally, the transparency of the first region 101 is lower than that of the second region 102. However, in the first region 101 of the radio wave reflector 10, the second opening area of ​​the second opening 131 is large, and light is less likely to be blocked by the ground electrode 130. Furthermore, light is incident on the radio wave reflector 10 from all directions, not just the normal direction of the first substrate 110-1 or the second substrate 110-2, but if the second opening area of ​​the second opening 131 is large, light incident from all directions is more likely to transmit through the first region 101. As a result, the difference in transparency between the first region 101 and the second region 102 becomes smaller, and the in-plane variation in transparency of the radio wave reflector 10 can be reduced.

[0037] As described above, in the first region 101 (reflecting antenna cell 100) of the radio wave reflector 10, the second opening area of ​​the second opening 131 provided in the ground electrode 130 is larger than the first opening area of ​​the first opening 121 provided in the patch electrode 120. Therefore, light blocking by the ground electrode 130 is reduced, and the amount of light transmitted through the first region 101 increases. As a result, the transparency of the first region 101 is improved. Furthermore, the first opening 121 in the first region 101 and the third opening 132 in the second region 102 have the same shape and size. Therefore, the brightness of the light transmitted through the first region 101 is approximately the same as the brightness of the light transmitted through the second region 102, and the in-plane variation in transparency of the radio wave reflector 10 can be reduced.

[0038] 7 to 8B, a radio wave reflector 10A will be described as a first modified example of the radio wave reflector 10. In the following, when the radio wave reflector 10A includes the same components as the radio wave reflector 10, the description of those components may be omitted.

[0039] Fig. 7 is a schematic plan view showing the configuration of a patch electrode 120A and a ground electrode 130A of a radio wave reflector 10A according to one embodiment of the present invention. Fig. 7 is a plan view corresponding to region A in Fig. 1. Fig. 8A is a schematic plan view showing the electrode pattern of the patch electrode 120A of the radio wave reflector 10A according to one embodiment of the present invention, and Fig. 8B is a schematic plan view showing the electrode pattern of the ground electrode 130A of the radio wave reflector 10A according to one embodiment of the present invention. The plan views of Figs. 8A and 8B correspond to the plan view of Fig. 7.

[0040] In plan view, the radio wave reflector 10A includes a first region 101 where the patch electrode 120A and the ground electrode 130A overlap, and a second region 102 where the patch electrode 120A and the ground electrode 130A do not overlap.

[0041] In the first region 101, the patch electrode 120A includes a plurality of first openings 121A having a first opening area (see FIG. 8A ). In addition, in the first region 101, the ground electrode 130A includes a plurality of second openings 131 having a second opening area (see FIG. 8B ). The cross-sectional shape of the first openings 121A is circular, and the cross-sectional shape of the second openings 131 is rectangular. The second opening area is larger than the first opening area. Although the first openings 121A and the second openings 131 have different shapes and sizes, the first openings 121A and the second openings 131 overlap in the first region 101. Specifically, one of the plurality of second openings 131 overlaps four of the plurality of first openings 121A. Since light passing through the first opening 121A and the second opening 131 is not blocked by the patch electrode 120A and the ground electrode 130A, the first region 101 has light-transmitting properties.

[0042] In the second region 102, the ground electrode 130A includes a plurality of third openings 132A having a third opening area (see FIG. 8B ). Light passing through the third openings 132A is not blocked by the patch electrode 120A and the ground electrode 130A, and therefore the second region 102 is translucent. The cross-sectional shape of the third openings 132A is rectangular. The third opening area is the same as the first opening area. That is, the third openings 132A have the same shape and size as the first openings 121A.

[0043] As described above, in the first region 101 (reflecting antenna cell 100) of the radio wave reflector 10A, the first opening 121A provided in the patch electrode 120A and the second opening 131 provided in the ground electrode have different shapes and sizes. However, because the second opening area of ​​the second opening 131 is larger than the first opening area of ​​the first opening 121A, light blocking by the ground electrode 130A is reduced, and the amount of light transmitted through the first region 101 is increased. As a result, the transparency of the first region 101 is improved. Furthermore, the first opening 121A in the first region 101 and the third opening 132A in the second region 102 have the same shape and size. Therefore, the brightness of light transmitted through the first region 101 is approximately the same as the brightness of light transmitted through the second region 102, thereby reducing in-plane variation in transparency in the radio wave reflector 10A.

[0044] 9 and 10, a radio wave reflector 10B will be described as a second modification of the radio wave reflector 10. In the following, when the radio wave reflector 10B includes the same components as the radio wave reflector 10, the description of those components may be omitted.

[0045] Fig. 9 is a schematic plan view showing the configuration of the patch electrode 120 and the ground electrode 130B of a radio wave reflector 10B according to one embodiment of the present invention. Fig. 9 is a plan view corresponding to region A in Fig. 1. Fig. 10 is a schematic plan view showing the electrode pattern of the ground electrode 130B of the radio wave reflector 10B according to one embodiment of the present invention. The plan view of Fig. 10 corresponds to the plan view of Fig. 9. The electrode pattern of the patch electrode 120 of the radio wave reflector 10B is the same as the electrode pattern shown in Fig. 4A.

[0046] In plan view, the radio wave reflector 10B includes a first region 101 where the patch electrode 120 and the ground electrode 130B overlap, and a second region 102 where the patch electrode 120 and the ground electrode 130B do not overlap.

[0047] In the first region 101, the ground electrode 130B includes a plurality of second openings 131B having a second opening area (see FIG. 10 ). The cross-sectional shape of the first openings 121 is rectangular, and the cross-sectional shape of the second openings 131B is triangular. The distance between two adjacent second openings 131B (i.e., the line width of the ground electrode 130B located between two adjacent second openings 131B) is smaller than the distance between two adjacent first openings 121 (i.e., the line width of the patch electrode 120 located between two adjacent first openings 121). Therefore, the second opening area is larger than the first opening area. Although the first openings 121 and the second openings 131B have different shapes and sizes, the first openings 121 and the second openings 131B overlap in the first region 101. Specifically, one of the plurality of second openings 131B overlaps with two of the plurality of first openings 121. In this manner, one of the plurality of second openings 131B can overlap with any number of the plurality of first openings 121. However, if too many first openings 121 overlap with one of the plurality of second openings 131B, it becomes difficult to generate a potential difference between the patch electrode 120 and the ground electrode 130, and the orientation of the liquid crystal molecules may not change even when a voltage is applied to the patch electrode 120. In this case, the reflection loss of the radio wave reflector 10B increases. Therefore, in order to suppress the increase in reflection loss of the radio wave reflector 10B, it is preferable that one of the plurality of second openings 131B overlaps with two to four of the plurality of first openings 121.

[0048] As described above, in the first region 101 (reflecting antenna cell 100) of the radio wave reflector 10B, one of the multiple second openings 131B can overlap any number of the multiple first openings 121. Even in this case, the second opening area of ​​the second opening 131B is larger than the first opening area of ​​the first opening 121, so light blocking by the ground electrode 130 is reduced and the amount of light transmitted through the first region 101 of the radio wave reflector 10B is increased. As a result, the transparency of the first region 101 is improved. Furthermore, the first opening 121 in the first region 101 and the third opening 132 in the second region 102 have the same shape and size. Therefore, the brightness of light transmitted through the first region 101 is approximately the same as the brightness of light transmitted through the second region 102, thereby reducing in-plane variation in transparency in the radio wave reflector 10B.

[0049] 11 and 12, a radio wave reflector 10C will be described as a third modification of the radio wave reflector 10. In the following, when the radio wave reflector 10C includes the same components as the radio wave reflector 10, the description of those components may be omitted.

[0050] Fig. 11 is a schematic plan view showing the configuration of the patch electrode 120 and the ground electrode 130C of a radio wave reflector 10C according to one embodiment of the present invention. Fig. 12 is a plan view corresponding to region A in Fig. 1. Fig. 12 is also a schematic plan view showing the electrode pattern of the ground electrode 130C of the radio wave reflector 10C according to one embodiment of the present invention. The plan view of Fig. 12 corresponds to the plan view of Fig. 11. The electrode pattern of the patch electrode 120 of the radio wave reflector 10C is the same as the electrode pattern shown in Fig. 4A.

[0051] In plan view, the radio wave reflector 10C includes a first region 101 where the patch electrode 120 and the ground electrode 130C overlap, and a second region 102 where the patch electrode 120 and the ground electrode 130C do not overlap.

[0052] In the first region 101, the ground electrode 130C includes a plurality of second openings 131C having a second opening area (see FIG. 12 ). The cross-sectional shape of each of the plurality of second openings 131C is polygonal. However, the sizes of the plurality of second openings 131C are not the same. That is, the second opening areas of the plurality of second openings 131C increase from the inside to the outside of the first region 101. Note that the second opening area of ​​the second opening 131C located at the innermost position in the first region 101 is the same as the first opening area of ​​the first opening 121. However, in order to improve brightness near the center of the first region 101, it is preferable that the second opening area of ​​the second opening 131 located at the innermost position in the first region 101 be larger than the first opening area of ​​the first opening 121.

[0053] In this modified example, a configuration is shown in which the electrode pattern of the ground electrode 130C in the first region 101 completely overlaps with the electrode pattern of the patch electrode 120 in the first region 101, but a configuration is also possible in which the electrode pattern of the ground electrode 130C in the first region 101 overlaps with an offset from the electrode pattern of the patch electrode 120 in the first region 101.

[0054] As described above, in the first region 101 (reflecting antenna cell 100) of the radio wave reflector 10C, the second opening areas of the multiple second openings 131C increase from the inside to the outside of the first region 101. In a transparent radio wave reflector, the shape of the first region 101 is easily visible at the boundary between the first region 101, where the patch electrode 120 is provided, and the second region 102, where the patch electrode 120 is not provided. Therefore, by gradually changing the brightness of the light transmitted through the first region 101, i.e., by gradually increasing the brightness of the light transmitted from the inside to the outside of the first region 101, the difference in transparency at the boundary between the first region 101 and the second region 102 can be made less noticeable. In addition, the first openings 121 in the first region 101 and the third openings 132 in the second region 102 have the same shape and size. Therefore, the brightness of light passing through the first region 101 is approximately the same as the brightness of light passing through the second region 102, and the in-plane variation in transparency of the radio wave reflector 10B can be reduced. Furthermore, inside the first region 101 of the radio wave reflector 10C, the area of ​​the region where the patch electrode 120 and the ground electrode 130 overlap can be increased. Therefore, an increase in the reflection loss of the radio wave reflector 10C can be suppressed.

[0055] 13 to 14B, a radio wave reflector 10D will be described as a fourth modification of the radio wave reflector 10. In the following, when the radio wave reflector 10D includes the same components as the radio wave reflector 10, the description of those components may be omitted.

[0056] Fig. 13 is a schematic plan view showing the configuration of a patch electrode 120D and a ground electrode 130D of a radio wave reflector 10D according to one embodiment of the present invention. Fig. 14 is a plan view corresponding to region A in Fig. 1. Fig. 14A is a schematic plan view showing the electrode pattern of the patch electrode 120D of the radio wave reflector 10D according to one embodiment of the present invention, and Fig. 14B is a schematic plan view showing the electrode pattern of the ground electrode 130D of the radio wave reflector 10D according to one embodiment of the present invention. The plan views of Figs. 14A and 14B correspond to the plan view of Fig. 13.

[0057] In plan view, the radio wave reflector 10D includes a first region 101 where the patch electrode 120D and the ground electrode 130D overlap, and a second region 102 where the patch electrode 120D and the ground electrode 130D do not overlap.

[0058] In the first region 101, the patch electrode 120A includes a plurality of first openings 121D having a first opening area (see FIG. 14A). In the first region 101, the ground electrode 130D includes a plurality of second openings 131D having a second opening area (see FIG. 14B). The cross-sectional shapes of the first openings 121D and the second openings 131D are rectangular, but are not limited thereto. The second opening area is smaller than the first opening area. The first openings 121D and the second openings 131D overlap each other. Specifically, one of the plurality of first openings 121D overlaps four of the plurality of second openings 131D.

[0059] In the second region 102, the ground electrode 130D includes a plurality of third openings 132D having a third opening area (see FIG. 14B ). The cross-sectional shape of the third openings 132D is rectangular, but is not limited to this. The third opening area is the same as the second opening area. Therefore, the third openings 132D have the same configuration as the second openings 131D. In other words, the ground electrode 130D has a plurality of second openings 131D having a second opening area in the first region 101 and the second region 102.

[0060] The radio wave reflector 10D has a configuration in which the size of the first opening area of ​​the first opening 121 provided in the patch electrode 120 is reversed to the size of the second opening area of ​​the second opening 131 provided in the ground electrode 130 in the first region 101 of the radio wave reflector 10D. Also in the first region 101 of the radio wave reflector 10D, the first opening area of ​​the first opening 121D is large, so that the patch electrode 120D is less likely to block light.

[0061] As described above, in the first region 101 (reflecting antenna cell 100) of the radio wave reflector 10D, the first opening area of ​​the first opening 121D provided in the patch electrode 120D is larger than the second opening area of ​​the second opening 131D provided in the ground electrode 130D. Therefore, light blocking by the patch electrode is reduced, and the amount of light transmitted through the first region 101 increases. As a result, the transparency of the first region 101 is improved. Furthermore, the second opening 131D in the first region 101 and the third opening 132D in the second region 102 have the same shape and size. Therefore, the brightness of the light transmitted through the first region 101 is approximately the same as the brightness of the light transmitted through the second region 102, thereby reducing in-plane variation in transparency in the radio wave reflector 10D.

[0062] 15 and 16, a radio wave reflector 10E will be described as a fifth modification of the radio wave reflector 10. In the following, when the radio wave reflector 10E includes the same components as the radio wave reflector 10, the description of those components may be omitted.

[0063] Fig. 15 is a schematic plan view showing the configuration of the patch electrode 120 and the ground electrode 130E of a radio wave reflector 10E according to one embodiment of the present invention. Fig. 15 is a plan view corresponding to region A in Fig. 1. Fig. 16 is a schematic plan view showing the electrode pattern of the ground electrode 130E of a radio wave reflector 10E according to one embodiment of the present invention. The plan view of Fig. 16 corresponds to the plan view of Fig. 15. The electrode pattern of the patch electrode 120 of the radio wave reflector 10E is the same as the electrode pattern shown in Fig. 4A.

[0064] In plan view, the radio wave reflector 10E includes a first region 101 where the patch electrode 120 and the ground electrode 130E overlap, and a second region 102 where the patch electrode 120 and the ground electrode 130E do not overlap.

[0065] In the first region 101, the ground electrode 130E includes a plurality of second openings 131E having a second opening area (see FIG. 16 ). The cross-sectional shape of the second openings 131E is rectangular. The second opening area is larger than the first opening area. The first openings 121 and the second openings 131E overlap each other. Specifically, one of the plurality of second openings 131E overlaps with four of the plurality of first openings 121.

[0066] In the second region 102, the ground electrode 130E includes a plurality of third openings 132E having a third opening area (see FIG. 16 ). The cross-sectional shape of the third openings 132E is rectangular. The third opening area is smaller than the first opening area. Only the ground electrode 130E is provided in the second region 102. On the other hand, the patch electrode 120 and the ground electrode 130E are provided in the first region 101. Therefore, light incident on the radio wave reflector 10E is more likely to be blocked in the first region 101 than in the second region 102. Therefore, in the second region 102 of the radio wave reflector 10E, the opening area of ​​the third openings 132 is made smaller, and the brightness of the light passing through the second region 102 is adjusted to match the brightness of the light passing through the first region 101. As a result, the difference in transparency between the first region 101 and the second region 102 becomes smaller, and the in-plane variation in transparency of the radio wave reflector 10E can be reduced.

[0067] As described above, in the first region 101 (reflecting antenna cell 100) of the radio wave reflector 10E, the second opening area of ​​the second opening 131E provided in the ground electrode 130E is larger than the first opening area of ​​the first opening 121 provided in the patch electrode 120. Therefore, light blocking by the ground electrode 130E is reduced, and the amount of light transmitting through the first region 101 is increased. As a result, the transparency of the first region 101 is improved. Furthermore, the third opening area of ​​the third opening 132E provided in the ground electrode 130E in the second region 102 is smaller than the opening area of ​​the first opening 121 provided in the patch electrode 120 in the first region 101. Therefore, light is more easily blocked in the second region 102 than in the first region 101, but the brightness of the light transmitting through the second region 102 can be adjusted. Therefore, the brightness of the light passing through the first region 101 can be adjusted to be the same as the brightness of the light passing through the second region 102, and the in-plane variation in transparency of the radio wave reflector 10E can be reduced.

[0068] The embodiments and modifications of the present invention can be combined as appropriate as long as they are not mutually inconsistent. Furthermore, even if a person skilled in the art adds or deletes components or modifies the design as appropriate based on the embodiments, or adds or omits steps or modifies conditions, such additions or deletions or modifications are made to the embodiments, they will also be included in the scope of the present invention as long as they include the gist of the present invention.

[0069] Even if there are other effects and advantages different from those brought about by the above-described embodiments, those that are clear from the description in this specification or that can be easily predicted by a person skilled in the art are naturally understood to be brought about by the present invention.

[0070] 10, 10A, 10B, 10C, 10D, 10E: radio wave reflector, 11: reflecting antenna area, 12: driving circuit area, 100: reflecting antenna cell, 100-1: first reflecting antenna cell, 100-2: second reflecting antenna cell, 101: first area, 102: second area, 110-1: first substrate, 110-2: second substrate, 120, 120A, 120D: patch electrode, 121, 121A, 121D: first opening, 130, 130A, 130B, 130C, 130D, 130E: ground electrode, 131, 131B, 131C, 131D, 131E: second opening, 132, 132A, 132D, 132E: third opening, 140-1: first alignment film, 140-2: second alignment film, 150: liquid crystal layer, 160: switching element, 161: semiconductor layer, 162: gate insulating layer, 163: gate electrode, 164: interlayer insulating layer, 165: planarization layer, 166: selection signal line, 167: data signal line

Claims

1. A radio wave reflector including: a patch electrode on a first substrate; a ground electrode on a second substrate different from the first substrate; a liquid crystal layer between the patch electrode and the ground electrode; a first region where the ground electrode overlaps the patch electrode in a plan view and a second region where the ground electrode does not overlap the patch electrode; in the first region, the patch electrode includes a plurality of first openings having a first opening area, and the ground electrode includes a plurality of second openings having a second opening area; in the second region, the ground electrode includes a plurality of third openings having a third opening area; the plurality of second openings overlap the plurality of first openings; and the second opening area is larger than the first opening area.

2. The radio wave reflector according to claim 1, wherein the third opening area is the same as the first opening area.

3. The radio wave reflector according to claim 1, wherein the third opening area is smaller than the first opening area.

4. The radio wave reflector according to claim 1, wherein an aperture ratio of the ground electrode in the second region is smaller than an aperture ratio of the ground electrode in the first region.

5. The radio wave reflector according to claim 1, wherein one of the plurality of second openings overlaps 2 to 4 of the plurality of first openings.

6. The radio wave reflector according to claim 1, wherein the second opening area of the plurality of second openings increases from the inside to the outside of the first region.

7. The radio wave reflector according to claim 1, wherein a cross-sectional shape of each of the plurality of first openings, the plurality of second openings, and the plurality of third openings is rectangular.

8. The radio wave reflector according to claim 1, wherein a cross-sectional shape of each of the plurality of first openings and the plurality of third openings is circular.

9. Further including a switching element on the first substrate, wherein the patch electrode is electrically connected to the switching element.

10. A radio wave reflector including a patch electrode on a first substrate, a ground electrode on a second substrate different from the first substrate, a liquid crystal layer between the patch electrode and the ground electrode, a first region where the ground electrode overlaps the patch electrode in a plan view, and a second region where the ground electrode does not overlap the patch electrode. In the first region, the patch electrode includes a plurality of first openings having a first opening area, and the ground electrode includes a plurality of second openings having a second opening area. In the second region, the ground electrode includes a plurality of third openings having a third opening area. The plurality of second openings overlap the plurality of first openings, and the second opening area is smaller than the first opening area.

11. The radio wave reflector according to claim 10, wherein the third opening area is the same as the second opening area.

12. The radio wave reflector according to claim 10, wherein the third opening area is smaller than the second opening area.

13. The radio wave reflector according to claim 10, wherein an aperture ratio of the ground electrode in the second region is smaller than an aperture ratio of the ground electrode in the first region.

14. The radio wave reflector according to claim 10, wherein one of the plurality of first openings overlaps two to four of the plurality of second openings.

15. The radio wave reflector according to claim 10, wherein the first opening area of the plurality of first openings increases from the inside to the outside of the first region.

16. The radio wave reflector according to claim 10, wherein a cross-sectional shape of each of the plurality of first openings, the plurality of second openings, and the plurality of third openings is rectangular.

17. The radio wave reflector according to claim 10, wherein a cross-sectional shape of each of the plurality of second openings and the plurality of third openings is circular.

18. Further including a switching element on the first substrate, and the patch electrode is electrically connected to the switching element. The radio wave reflector according to claim 10.